Determination of Imprint Effects in Ferroelectrics from the Quantified Phase and Amplitude ResponseClick to copy article linkArticle link copied!
- Subhajit PalSubhajit PalSchool of Engineering & Materials Science, Queen Mary University of London, London E1 4NS, United KingdomMore by Subhajit Pal
- Emanuele PalladinoEmanuele PalladinoSchool of Engineering & Materials Science, Queen Mary University of London, London E1 4NS, United KingdomMore by Emanuele Palladino
- Haozhen YuanHaozhen YuanSchool of Engineering & Materials Science, Queen Mary University of London, London E1 4NS, United KingdomMore by Haozhen Yuan
- Muireann Anna de h-ÓraMuireann Anna de h-ÓraDepartment of Materials Science & Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United KingdomMore by Muireann Anna de h-Óra
- Judith L. MacManus-DriscollJudith L. MacManus-DriscollDepartment of Materials Science & Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United KingdomMore by Judith L. MacManus-Driscoll
- Jorge OntanedaJorge OntanedaSchool of Engineering & Materials Science, Queen Mary University of London, London E1 4NS, United KingdomMore by Jorge Ontaneda
- Vivek DwijVivek DwijUGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452017, IndiaMore by Vivek Dwij
- Vasant G. SatheVasant G. SatheUGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452017, IndiaMore by Vasant G. Sathe
- Joe Briscoe*Joe Briscoe*Email: [email protected]School of Engineering & Materials Science, Queen Mary University of London, London E1 4NS, United KingdomMore by Joe Briscoe
Abstract
Piezoresponse force microscopy (PFM) is a robust characterization technique to explore ferroelectric properties at the nanoscale. However, the PFM signal can lead to misinterpretation of results due to the dominant electrostatic interaction between the tip and the sample. In this work, a detailed calibration process is presented and a procedure to identify the parasitic phase offset is demonstrated. To obtain artifact-free phase–amplitude loops, a methodology is developed by combining the outcomes from switching spectroscopy-PFM (SS-PFM) and Kelvin probe force microscopy (KPFM). It is demonstrated that the phase and amplitude loops obtained from SS-PFM at a specific read voltage, ascertained from the surface potential by KPFM, can convey accurate electromechanical information. These methodologies are applied to quantify the imprint voltage in BaTiO3 and BiFeO3, along with vertically aligned BaTiO3:Sm2O3 and BaTiO3:MgO nanocomposites. The variation of the imprint voltage measured under different tip voltages demonstrates the importance of selecting the correct read voltage in determining the local imprint voltage. Additionally, 2D imprint voltage maps in each domain of a BaTiO3 single crystal are obtained using the datacube-PFM technique, which allows pixel-by-pixel determination of artifact-free spatial variation of PFM phase–amplitude response.
This publication is licensed under
License Summary*
You are free to share(copy and redistribute) this article in any medium or format and to adapt(remix, transform, and build upon) the material for any purpose, even commercially within the parameters below:
Creative Commons (CC): This is a Creative Commons license.
Attribution (BY): Credit must be given to the creator.
*Disclaimer
This summary highlights only some of the key features and terms of the actual license. It is not a license and has no legal value. Carefully review the actual license before using these materials.
License Summary*
You are free to share(copy and redistribute) this article in any medium or format and to adapt(remix, transform, and build upon) the material for any purpose, even commercially within the parameters below:
Creative Commons (CC): This is a Creative Commons license.
Attribution (BY): Credit must be given to the creator.
*Disclaimer
This summary highlights only some of the key features and terms of the actual license. It is not a license and has no legal value. Carefully review the actual license before using these materials.
License Summary*
You are free to share(copy and redistribute) this article in any medium or format and to adapt(remix, transform, and build upon) the material for any purpose, even commercially within the parameters below:
Creative Commons (CC): This is a Creative Commons license.
Attribution (BY): Credit must be given to the creator.
*Disclaimer
This summary highlights only some of the key features and terms of the actual license. It is not a license and has no legal value. Carefully review the actual license before using these materials.
1. Introduction
2. Experimental Methods
Synthesis of BiFeO3 (BFO) Thin Films
Synthesis of BTO, BTO:SmO, and BTO:MgO Thin Films
PFM and KPFM Measurements
3. Results and Discussion
Figure 1
Figure 1. Phase sweep with respect to frequency, PFM phase image, and domain distribution of the BFO thin film measured under (a–c) uncalibrated conditions. After electrical writing, PFM phase images and domain distribution of a BFO thin film in (d) uncalibrated, (e) partially calibrated (autocalibrated), and (f) fully calibrated conditions. Images were taken in 6 × 6 μm2 after ±10 V poling in the 4 × 4 and 2 × 2 μm2 areas, respectively. Phase sweep with respect to frequency, PFM phase image, and domain distribution of the BFO thin film measured under (g–i) calibrated conditions.
Figure 2
Figure 2. (a) The schematic of single-segment SS-PFM script showing the voltage waveform in bias on and off conditions. (b) Example multisegment SS-PFM script displaying write and three read voltage steps, where read voltage steps are −1, 0, and +1 V. (c −g) PFM phase and amplitude hysteresis loop of a BFO thin film measured for −0.50 to +0.50 V read voltages, respectively. The electrostatically neutral phase amplitude loop is displayed in part d. (h) KPFM image (2 × 2 μm2) and (i) KPFM line scan of the BFO thin film in the measured SS-PFM area.
Figure 3
Figure 3. (a–e) PFM phase and amplitude hysteresis loop of a BTO single crystal for −1 to +1 V read voltage segments. (f) KPFM image (1 × 1 μm2) and (g) KPFM line scan in the measured SS-PFM area.
Figure 4
Figure 4. (a, d) Phase versus bias voltage and (b, e) switching voltage measured at the correct Vr value obtained from several measurements for a BTO single crystal and BFO thin film, respectively. (c and f) Variation of imprint voltage obtained under different Vr values.
Figure 5
Figure 5. PFM phase response exhibiting the ferroelectric domain switching behavior and phase loops of (a and c) BTO and (b and d) BTO:SmO VAN structures. Images were taken in 6 × 6 μm2 after ±10 V poling in the 4 × 4 and 2 × 2 um2 areas, respectively. (e) The imprint voltages for BTO and BTO:SmO VAN structures.
Figure 6
Figure 6. (a, b, and c) PFM phase, amplitude, and KPFM potential of a BTO:MgO VAN structure of an 8 × 8 um2 area after ±10 V poling in the 4 × 4 and 2 × 2 um2 areas, respectively. (d) Imprint voltage extracted from the sample at the unpoled, positive, and negative poled conditions using Vr values obtained locally within each region as shown in part (c).
Figure 7
Figure 7. Coercive voltage map acquired from the forward (a) and backward (b) voltage sweeps in a 15 × 10 μm2 area, with the respective amplitude sweeps from a selection of pixels shown below, as indicated by the arrows. (c) Imprint voltage map and (d) corresponding PFM phase image of a BTO crystal.
4. Conclusion
Data Availability
The data that support the findings of this study are available at Queen Mary Research Online (QMRO) at https://qmro.qmul.ac.uk/xmlui/.
Supporting Information
The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsaelm.4c00875.
Angle-resolved PFM of BFO and BTO, topographic image, SHO fitting of amplitude and R2 value with frequency for BFO; SHO fitting of amplitude, phase sweep with frequency, and R2 value with frequency for BTO; optical image of a BFO thin film where PFM calibration is performed; SS-PFM waveform; KPFM before and after SS-PFM measurements on BFO; phase image, domain distribution, and phase–amplitude curve of a BFO thin film in the uncalibrated and calibrated conditions; phase–amplitude curve of a BTO thin film measured in uncalibrated and calibrated conditions; off-surface SS-PFM measurements, topographic image of BTO and BTO:SmO thin films; KPFM image of BTO and BTO:SmO; imprint variation at Vr = 0 for BTO:MgO; force, voltage, amplitude, and phase versus measurement time for BFO and BTO samples (PDF)
Supporting video file demonstrating the calibration procedure of a BFO thin film (MP4)
Terms & Conditions
Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.
Acknowledgments
This project received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programs (Grant agreement no. 101001626 and no. 882929). SP acknowledges SEMS, QMUL for Early Career Research Award. The authors thank Mickael Febvre from Bruker for valuable discussions and Ahmed Kursumovic from the University of Cambridge for commenting on the manuscript. JD thanks the Royal Academy of Engineering Chair in Emerging Technologies Grant CiET1819\24.
References
This article references 57 other publications.
- 1Gruverman, A.; Alexe, M.; Meier, D. Piezoresponse Force Microscopy and Nanoferroic Phenomena. Nat. Coummn 2019, 10, 1661, DOI: 10.1038/s41467-019-09650-8Google ScholarThere is no corresponding record for this reference.
- 2Hong, S.; Woo, J.; Shin, H.; Jeon, J. U.; Pak, Y. E.; Colla, E. L.; Setter, N.; Kim, E.; No, K. Principle of Ferroelectric Domain Imaging Using Atomic Force Microscope. J. Appl. Phys. 2001, 89, 1377– 1386, DOI: 10.1063/1.1331654Google Scholar2https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3MXmvFeg&md5=3e38939ff395d43144bc7400c03dad5aPrinciple of ferroelectric domain imaging using atomic force microscopeHong, Seungbum; Woo, Jungwon; Shin, Hyunjung; Jeon, Jong Up; Pak, Y. Eugene; Colla, Enrico L.; Setter, Nava; Kim, Eunah; No, KwangsooJournal of Applied Physics (2001), 89 (2), 1377-1386CODEN: JAPIAU; ISSN:0021-8979. (American Institute of Physics)The contrast mechanisms of domain imaging expts. assisted by at. force microscope (AFM) have been investigated by model expts. on nonpiezoelec. (silicon oxide) and piezoelec. [Pb(Zr,Ti)O3] thin films. The first step was to identify the electrostatic charge effects between the tip, the cantilever, and the sample surface. The second step was to explore the tip-sample piezoelec. force interaction. The static deflection of the cantilever was measured as a function of dc bias voltage (Vdc) applied to the bottom electrode (n-type Si wafers) for noncontact and contact modes. In addn., a small ac voltage (Vac[hthinsp]sin[hthinsp]ωt) was applied to the tip to measure the amplitude (Aω) and phase ([Fgr]ω) of the first harmonic (ω) signal as a function of Vdc. By changing from the noncontact to the contact mode, a repulsive contribution to the static deflection was found in addn. to the attractive one and a 180° phase shift in [Fgr]ω was obsd. These results imply that in the contact mode the cantilever buckling is induced by the capacitive force between the cantilever and the sample surface. This interaction adds to the tip-sample piezoelec. interaction thereby overlapping the obtained tip vibration signal. Therefore, the antiparallel ferroelec. domain images obtained at zero dc bias voltage will show a variation in Aω but a negligible one in [Fgr]ω. The capacitive force contribution to the tip vibration signal was further verified in piezoelec. hysteresis loop measurement assisted by the AFM. The obsd. vertical offset of the loops was explained by the contact p.d. between the cantilever and the bottom electrode. The shape of the curve could be explained by the capacitive force interaction combined with the tip-sample piezoelec. interaction. The exptl. results obtained in this study support the interpretation of the cantilever-sample capacitive force contribution to the tip vibration signal in ferroelec. domain imaging expts. using AFM as a probing tool. The use of a large area top electrode between the tip and the sample resulted in the elimination of the electrostatic cantilever-sample interaction with negligible degrdn. of the domain contrast. This method proved to be successful because the cantilever-sample interaction was hardly detected and only the tip-sample interaction was obsd.
- 3Murrell, M. P.; Welland, M. E.; O’Shea, S. J.; Wong, T. M. H.; Barnes, J. R.; McKinnon, A. W.; Heyns, M.; Verhaverbeke, S. Spatially Resolved Electrical Measurements of SiO2 Gate Oxides Using Atomic Force Microscopy. Appl. Phys. Lett. 1993, 62, 786– 788, DOI: 10.1063/1.108579Google Scholar3https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK3sXhtlOgt74%253D&md5=910e0860f198115749f0f34116d72eabSpatially resolved electrical measurements of silica gate oxides using atomic force microscopyMurrell, M. P.; Welland, M. E.; O'Shea, S. J.; Wong, T. M. H.; Barnes, J. R.; McKinnon, A. W.; Heyns, M.; Verhaverbeke, S.Applied Physics Letters (1993), 62 (7), 786-8CODEN: APPLAB; ISSN:0003-6951.By using a modified at. force microscope (AFM) with a conducting cantilever, the authors have investigated the dielec. strength of SiO2 gate oxide films. This has been achieved by spatially resolving the prebreakdown tunneling current flowing between the silicon substrate and tip. During AFM imaging, a voltage ramp was applied to the tip at each image point so as to det. the local threshold voltage required to generate a small tunneling current in the oxide without causing an irreversible elec. breakdown. For an oxide 12-nm thick, this voltage was found to vary by more than a factor of 2.7 over an area of 0.14 μm2, with a max. value of 40.5 V. This suggests that the breakdown strength of conventional metal-oxide-silicon capacitors may not be limited by the intrinsic dielec. strength of the oxide, but by imperfections or nonuniformities in the Si/SiO2 structure. By preventing irreversible oxide breakdown during scanning, the authors can image the dielec. properties of oxide films with a lateral resoln. better than 20 nm.
- 4Nonnenmacher, M.; O’Boyle, M. P.; Wickramasinghe, H. K. Kelvin Probe Force Microscopy. Appl. Phys. Lett. 1991, 58, 2921– 2923, DOI: 10.1063/1.105227Google ScholarThere is no corresponding record for this reference.
- 5Polcari, D.; Dauphin-Ducharme, P.; Mauzeroll, J. Scanning Electrochemical Microscopy: A Comprehensive Review of Experimental Parameters from 1989 to 2015. Chem. Rev. 2016, 116, 13234– 13278, DOI: 10.1021/acs.chemrev.6b00067Google Scholar5https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xhs1Kjs7nL&md5=df364f985fc28b4a7c6971fbf9bdd5fcScanning Electrochemical Microscopy: A Comprehensive Review of Experimental Parameters from 1989 to 2015Polcari, David; Dauphin-Ducharme, Philippe; Mauzeroll, JanineChemical Reviews (Washington, DC, United States) (2016), 116 (22), 13234-13278CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)A review. Scanning electrochem. microscopy (SECM) is an electroanal. scanning probe technique capable of imaging substrate topog. and local reactivity with high resoln. Since its inception in 1989, it has expanded into a wide variety of research areas including biol., corrosion, energy, kinetics, instrumental development, and surface modification. In the past 25 years, over 1800 peer-reviewed publications have focused on SECM, including several topical reviews. However, these reviews often omit key details, forcing readers to search the literature. In this review, the authors provide a comprehensive summary of the exptl. parameters (e.g., solvents, probes, and mediators) used in all SECM publications since 1989, irresp. of the application. It can be used to rapidly assess exptl. possibilities and make an informed decision about exptl. design. It is a practical guide to SECM.
- 6Williams, C. C.; Wickramasinghe, H. K. Scanning Thermal Profiler. Appl. Phys. Lett. 1986, 49, 1587– 1589, DOI: 10.1063/1.97288Google ScholarThere is no corresponding record for this reference.
- 7Zhang, Y.; Zhu, W.; Hui, F.; Lanza, M.; Borca-Tasciuc, T.; Rojo, M. M. A Review on Principles and Applications of Scanning Thermal Microscopy (SThM). Adv. Funct. Mater. 2020, 30, 1900892, DOI: 10.1002/adfm.201900892Google Scholar7https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhslSqurvL&md5=7e7bbbe363ff549020579cec6c13f390A Review on Principles and Applications of Scanning Thermal Microscopy (SThM)Zhang, Yun; Zhu, Wenkai; Hui, Fei; Lanza, Mario; Borca-Tasciuc, Theodorian; Munoz Rojo, MiguelAdvanced Functional Materials (2020), 30 (18), 1900892CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA)A review. As the size of materials, particles, and devices shrinks to nanometer, at., or even quantum scale, it is more challenging to characterize their thermal properties reliably. Scanning thermal microscopy (SThM) is an emerging method to obtain local thermal information by controlling and monitoring probe-sample thermal exchange processes. In this review, key exptl. and theor. components of the SThM system are discussed, including thermal probes and exptl. methods, heat transfer mechanisms, calibration strategies, thermal exchange resistance, and effective heat transfer coeffs. Addnl., recent applications of SThM to novel materials and devices are reviewed, with emphasis on thermoelec., biol., phase change, and 2D materials.
- 8Rubio-Marcos, F.; Del Campo, A.; Marchet, P.; Fernandez, J. F. Ferroelectric Domain Wall Motion Induced by Polarized Light. Nat. Coummn 2015, 6, 6594, DOI: 10.1038/ncomms7594Google ScholarThere is no corresponding record for this reference.
- 9Lu, H.; Tan, Y.; McConville, J. P. V.; Ahmadi, Z.; Wang, B.; Conroy, M.; Moore, K.; Bangert, U.; Shield, J. E.; Chen, L.-Q.; Gregg, J. M.; Gruverman, A. Electrical Tunability of Domain Wall Conductivity in LiNbO3 Thin Films. Adv. Mater. 2019, 31, 1902890, DOI: 10.1002/adma.201902890Google Scholar9https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhvFWktb%252FN&md5=3947e7f60a7d6290858ae49c0ffa7c9dElectrical tunability of domain wall conductivity in LiNbO3 thin filmsLu, Haidong; Tan, Yueze; McConville, James P. V.; Ahmadi, Zahra; Wang, Bo; Conroy, Michele; Moore, Kalani; Bangert, Ursel; Shield, Jeffrey E.; Chen, Long-Qing; Gregg, J. Marty; Gruverman, AlexeiAdvanced Materials (Weinheim, Germany) (2019), 31 (48), 1902890CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)Domain wall nanoelectronics is a rapidly evolving field, which explores the diverse electronic properties of the ferroelec. domain walls for application in low-dimensional electronic systems. One of the most prominent features of the ferroelec. domain walls is their elec. cond. Here, using a combination of scanning probe and scanning transmission electron microscopy, the mechanism of the tunable conducting behavior of the domain walls in the sub-micrometer thick films of the technol. important ferroelec. LiNbO3 is explored. It is found that the elec. bias generates stable domains with strongly inclined domain boundaries with the inclination angle reaching 20° with respect to the polar axis. The head-to-head domain boundaries exhibit high conductance, which can be modulated by application of the sub-coercive voltage. Electron microscopy visualization of the elec. written domains and piezoresponse force microscopy imaging of the very same domains reveals that the gradual and reversible transition between the conducting and insulating states of the domain walls results from the elec. induced wall bending near the sample surface. The obsd. modulation of the wall conductance is corroborated by the phase-field modeling. The results open a possibility for exploiting the conducting domain walls as the elec. controllable functional elements in the multilevel logic nanoelectronics devices.
- 10Liu, Z.; Wang, H.; Li, M.; Tao, L.; Paudel, T. R.; Yu, H.; Wang, Y.; Hong, S.; Zhang, M.; Ren, Z.; Xie, Y.; Tsymbal, E. Y.; Chen, J.; Zhang, Z.; Tian, H. In-plane Charged Domain Walls With Memristive Behaviour in a Ferroelectric Film. Nature 2023, 613, 656– 661, DOI: 10.1038/s41586-022-05503-5Google Scholar10https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3sXhslKitro%253D&md5=9cb07b6ea2d8a4d107f958269f74f19fIn-plane charged domain walls with memristive behaviour in a ferroelectric filmLiu, Zhongran; Wang, Han; Li, Ming; Tao, Lingling; Paudel, Tula R.; Yu, Hongyang; Wang, Yuxuan; Hong, Siyuan; Zhang, Meng; Ren, Zhaohui; Xie, Yanwu; Tsymbal, Evgeny Y.; Chen, Jingsheng; Zhang, Ze; Tian, HeNature (London, United Kingdom) (2023), 613 (7945), 656-661CODEN: NATUAS; ISSN:1476-4687. (Nature Portfolio)Abstr.: Domain-wall nanoelectronics is considered to be a new paradigm for non-volatile memory and logic technologies in which domain walls, rather than domains, serve as an active element. Esp. interesting are charged domain walls in ferroelec. structures, which have subnanometre thicknesses and exhibit non-trivial electronic and transport properties that are useful for various nanoelectronics applications1-3. The ability to deterministically create and manipulate charged domain walls is essential to realize their functional properties in electronic devices. Here we report a strategy for the controllable creation and manipulation of in-plane charged domain walls in BiFeO3 ferroelec. films a few nanometers thick. By using an in situ biasing technique within a scanning transmission electron microscope, an unconventional layer-by-layer switching mechanism is detected in which ferroelec. domain growth occurs in the direction parallel to an applied elec. field. Based on atomically resolved electron energy-loss spectroscopy, in situ charge mapping by in-line electron holog. and theor. calcns., we show that oxygen vacancies accumulating at the charged domain walls are responsible for the domain-wall stability and motion. Voltage control of the in-plane domain-wall position within a BiFeO3 film gives rise to multiple non-volatile resistance states, thus demonstrating the key functional property of being a memristor a few unit cells thick. These results promote a better understanding of ferroelec. switching behavior and provide a new strategy for creating unit-cell-scale devices.
- 11Crassous, A.; Sluka, T.; Tagantsev, A. K.; Setter, N. Polarization Charge as a Reconfigurable Quasi-Dopant in Ferroelectric Thin Films. Nat. Nanotechnol. 2015, 10, 614– 618, DOI: 10.1038/nnano.2015.114Google Scholar11https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtlOhu73F&md5=673d3749884123320b0cac1c2c7257eePolarization charge as a reconfigurable quasi-dopant in ferroelectric thin filmsCrassous, Arnaud; Sluka, Tomas; Tagantsev, Alexander K.; Setter, NavaNature Nanotechnology (2015), 10 (7), 614-618CODEN: NNAABX; ISSN:1748-3387. (Nature Publishing Group)Impurity elements used as dopants are essential to semiconductor technol. for controlling the concn. of charge carriers. Their location in the semiconductor crystal is detd. during the fabrication process and remains fixed. However, another possibility exists whereby the concn. of charge carriers is modified using polarization charge as a quasi-dopant, which implies the possibility to write, displace, erase and re-create channels having a metallic-type cond. inside a wide-bandgap semiconductor matrix. Polarization-charge doping is achieved in ferroelecs. by the creation of charged domain walls. The intentional creation of stable charged domain walls has so far only been reported in BaTiO3 single crystals, with a process that involves cooling the material through its phase transition under a strong elec. bias, but this is not a viable technol. when real-time reconfigurability is sought in working devices. Here, the authors demonstrate a technique allowing the creation and nanoscale manipulation of charged domain walls and their action as a real-time doping activator in ferroelec. thin films. Stable individual and multiple conductive channels with various lengths from 3 μm to 100 nm were created, erased and recreated in another location, and their high metallic-type cond. was verified. This takes the idea of hardware reconfigurable electronics one step forward.
- 12Gruverman, A.; Wu, D.; Lu, H.; Wang, Y.; Jang, H. W.; Folkman, C. M.; Zhuravlev, M. Ye.; Felker, D.; Rzchowski, M.; Eom, C.-B.; Tsymbal, E. Y. Tunneling Electroresistance Effect in Ferroelectric Tunnel Junctions at the. Nanoscale Nano Lett. 2009, 10, 3539– 3543, DOI: 10.1021/nl901754tGoogle ScholarThere is no corresponding record for this reference.
- 13Li, T.; Lipatov, A.; Lu, H.; Lee, H.; Lee, J.-W.; Torun, E.; Wirtz, L.; Eom, C.-B.; Iniguez, J.; Sinitskii, A.; Gruverman, A. Optical Control of Polarization in Ferroelectric Heterostructures. Nat. Coummn. 2018, 9, 3344, DOI: 10.1038/s41467-018-05640-4Google ScholarThere is no corresponding record for this reference.
- 14Alexe, M.; Hesse, D. Tip-enhanced Photovoltaic Effects in Bismuth Ferrite. Nat. Coummn 2011, 2, 256, DOI: 10.1038/ncomms1261Google ScholarThere is no corresponding record for this reference.
- 15Catalan, G.; Seidel, J.; Ramesh, R.; Scott, J. F. Domain Wall Nanoelectronics. Rev. Mod. Phys. 2012, 84, 119, DOI: 10.1103/RevModPhys.84.119Google Scholar15https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XotVOns7g%253D&md5=6b85589cdf76a167de162bf321e0fd81Domain wall nanoelectronicsCatalan, G.; Seidel, J.; Ramesh, R.; Scott, J. F.Reviews of Modern Physics (2012), 84 (1), 119-156CODEN: RMPHAT; ISSN:0034-6861. (American Physical Society)A review. Domains in ferroelecs. were considered to be well understood by the middle of the last century: They were generally rectilinear, and their walls were Ising-like. Their simplicity stood in stark contrast to the more complex Bloch walls or Neel walls in magnets. Only within the past decade and with the introduction of at.-resoln. studies via transmission electron microscopy, electron holog., and at. force microscopy with polarization sensitivity has their real complexity been revealed. Addnl. phenomena appear in recent studies, esp. of magnetoelec. materials, where functional properties inside domain walls are being directly measured. In this paper these studies are reviewed, focusing attention on ferroelecs. and multiferroics but making comparisons where possible with magnetic domains and domain walls. An important part of this review will concern device applications, with the spotlight on a new paradigm of ferroic devices where the domain walls, rather than the domains, are the active element. Here magnetic wall microelectronics is already in full swing, owing largely to the work of Cowburn and of Parkin and their colleagues. These devices exploit the high domain wall mobilities in magnets and their resulting high velocities, which can be supersonic, as shown by Kreines' and co-workers 30 years ago. By comparison, nanoelectronic devices employing ferroelec. domain walls often have slower domain wall speeds, but may exploit their smaller size as well as their different functional properties. These include domain wall cond. (metallic or even superconducting in bulk insulating or semiconducting oxides) and the fact that domain walls can be ferromagnetic while the surrounding domains are not.
- 16Neumayer, S. M.; Saremi, S.; Martin, L. W.; Collins, L.; Tselev, A.; Jesse, S.; Kalinin, S. V.; Balke, N. Piezoresponse Amplitude and Phase Quantified for Electromechanical Characterization. J. Appl. Phys. 2020, 128, 171105, DOI: 10.1063/5.0011631Google Scholar16https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXit1Ois7jN&md5=d5651a50c9dc606bd82b37989b6b55a3Piezoresponse amplitude and phase quantified for electromechanical characterizationNeumayer, Sabine M.; Saremi, Sahar; Martin, Lane W.; Collins, Liam; Tselev, Alexander; Jesse, Stephen; Kalinin, Sergei V.; Balke, NinaJournal of Applied Physics (Melville, NY, United States) (2020), 128 (17), 171105CODEN: JAPIAU; ISSN:0021-8979. (American Institute of Physics)Piezoresponse force microscopy (PFM) is a powerful characterization technique to readily image and manipulate the ferroelec. domains. PFM gives an insight into the strength of local piezoelec. coupling and polarization direction through PFM amplitude and phase, resp. Converting measured arbitrary units into units of effective piezoelec. const. remains a challenge, and insufficient methods are often used. While most quantification efforts have been spent on quantifying the PFM amplitude signal, little attention has been given to the PFM phase, which is often arbitrarily adjusted to fit expectations. This is problematic when investigating materials with unknown or neg. sign of the probed effective electrostrictive coeff. or strong frequency dispersion of electromech. responses, because assumptions about the PFM phase cannot be reliably made. The PFM phase can, however, provide important information on the polarization orientation and the sign of the effective electrostrictive coeff. probed by PFM. Most notably, the orientation of the PFM hysteresis loop is detd. by the PFM phase. Moreover, when presenting PFM data as a combined signal, the resulting response can be artificially lowered or asym. if the phase data have not been correctly processed. Here, we explain the PFM amplitude quantification process and demonstrate a path to identify the phase offset required to ext. correct meaning from the PFM phase data. We explore different sources of phase offsets including the exptl. setup, instrumental contributions, and data anal. We discuss the phys. working principles of PFM and develop a strategy to ext. phys. meaning from the PFM amplitude and phase. (c) 2020 American Institute of Physics.
- 17Collins, L.; Liu, Y.; Ovchinnikova, O. S.; Proksch, R. Quantitative Electromechanical Atomic Force Microscopy. ACS Nano 2019, 13, 8055– 8066, DOI: 10.1021/acsnano.9b02883Google Scholar17https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhtlSntbvM&md5=028a3e36f62f344dbe31b87a93f1e0ccQuantitative electromechanical atomic force microscopyCollins, Liam; Liu, Yongtao; Ovchinnikova, Olga S.; Proksch, RogerACS Nano (2019), 13 (7), 8055-8066CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)The ability to probe a material's electromech. functionality on the nanoscale is crit. to applications from energy storage and computing to biol. and medicine. Voltage-modulated at. force microscopy (VM-AFM) has become a mainstay characterization tool for investigating these materials due to its ability to locally probe electromechanically responsive materials with spatial resoln. from micrometers to nanometers. However, with the wide popularity of VM-AFM techniques such as piezoresponse force microscopy and electrochem. strain microscopy there has been a rise in reports of nanoscale electromech. functionality, including hysteresis, in materials that should be incapable of exhibiting piezo- or ferroelectricity. Explanations for the origins of unexpected nanoscale phenomena have included new material properties, surface-mediated polarization changes, and/or spatially resolved behavior that is not present in bulk measurements. At the same time, it is well known that VM-AFM measurements are susceptible to numerous forms of crosstalk, and, despite efforts within the AFM community, a global approach for eliminating this has remained elusive. In this work, the authors develop a method for easily demonstrating the presence of hysteretic (i.e., "false ferroelec.") long-range interactions between the sample and cantilever body. This method should be easy to implement in any VM-AFM measurement. They then go on to demonstrate fully quant. and repeatable nanoelectromech. characterization using an interferometer. These quant. measurements are crit. for a wide range of devices including MEMS actuators and sensors, memristor, energy storage, and memory.
- 18Buragohain, P.; Lu, H.; Richter, C.; Schenk, T.; Kariuki, P.; Glinsek, S.; Funakubo, H.; Íñiguez, J.; Defay, E.; Schroeder, U.; Gruverman, A. Quantification of the Electromechanical Measurements by Piezoresponse Force Microscopy. Adv. Mater. 2022, 34, 2206237, DOI: 10.1002/adma.202206237Google Scholar18https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38XislegtLzO&md5=e0f05919a14c966368c237ba04683301Quantification of the Electromechanical Measurements by Piezoresponse Force MicroscopyBuragohain, Pratyush; Lu, Haidong; Richter, Claudia; Schenk, Tony; Kariuki, Pamenas; Glinsek, Sebastjan; Funakubo, Hiroshi; Iniguez, Jorge; Defay, Emmanuel; Schroeder, Uwe; Gruverman, AlexeiAdvanced Materials (Weinheim, Germany) (2022), 34 (47), 2206237CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)Piezoresponse force microscopy (PFM) is widely used for characterization and exploration of the nanoscale properties of ferroelecs. However, quantification of the PFM signal is challenging due to the convolution of various extrinsic and intrinsic contributions. Although quantification of the PFM amplitude signal has received considerable attention, quantification of the PFM phase signal has not been addressed. A properly calibrated PFM phase signal can provide valuable information on the sign of the local piezoelec. coeff.-an important and nontrivial issue for emerging ferroelecs. In this work, two complementary methodologies to calibrate the PFM phase signal are discussed. The first approach is based on using a std. ref. sample with well-known independently measured piezoelec. coeffs., while the second approach exploits the electrostatic sample-cantilever interactions to det. the parasitic phase offset. Application of these methodologies to studies of the piezoelec. behavior in ferroelec. HfO2-based thin-film capacitors reveals intriguing variations in the sign of the longitudinal piezoelec. coeff., d33,eff. It is shown that the piezoelec. properties of the HfO2-based capacitors are inherently sensitive to their thickness, electrodes, as well as deposition methods, and can exhibit wide variations including a d33,eff sign change within a single device.
- 19Kim, S.; Seol, D.; Lu, X.; Alexe, M.; Kim, Y. Electrostatic-free Piezoresponse Force Microscopy. Sci. Rep. 2017, 7, 41657, DOI: 10.1038/srep41657Google Scholar19https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXitVyisr8%253D&md5=6d18695f2a62e1da85ec7d85eabbf57fElectrostatic-free piezoresponse force microscopyKim, Sungho; Seol, Daehee; Lu, Xiaoli; Alexe, Marin; Kim, YunseokScientific Reports (2017), 7 (), 41657CODEN: SRCEC3; ISSN:2045-2322. (Nature Publishing Group)Contact and non-contact based at. force microscopy (AFM) approaches have been extensively utilized to explore various nanoscale surface properties. In most AFM-based measurements, a concurrent electrostatic effect between the AFM tip/cantilever and sample surface can occur. This electrostatic effect often hinders accurate measurements. Thus, it is very important to quantify as well as remove the impact of the electrostatic effect on AFM-based measurements. In this study, we examine the impact of the electrostatic effect on the electromech. (EM) response in piezoresponse force microscopy as a model AFM mode. We quant. studied the effects of increasing the external elec. field and reducing the spring const. of a cantilever. Further, we explored ways to minimize the electrostatic effect. The results provide broad guidelines for quant. analyzing the EM response as well as, eventually, for obtaining the electrostatic-free EM response. The conclusions can be applied to other AFM-based measurements that are subject to a strong electrostatic effect between the AFM tip/cantilever and sample surface, regardless of contact and non-contact modes.
- 20Balke, N.; Jesse, S.; Yu, P.; Carmichael, B.; Kalinin, S. V.; Tselev, A. Quantification of Surface Displacements and Electromechanical Phenomena via Dynamic Atomic Force Microscopy. Nanotechnology 2016, 27, 425707, DOI: 10.1088/0957-4484/27/42/425707Google Scholar20https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BC2svgs1ahsg%253D%253D&md5=363cd3ac972f07bc0e4aca7fb2790f56Quantification of surface displacements and electromechanical phenomena via dynamic atomic force microscopyBalke Nina; Jesse Stephen; Yu Pu; Ben Carmichael; Kalinin Sergei V; Tselev AlexanderNanotechnology (2016), 27 (42), 425707 ISSN:.Detection of dynamic surface displacements associated with local changes in material strain provides access to a number of phenomena and material properties. Contact resonance-enhanced methods of atomic force microscopy (AFM) have been shown capable of detecting ∼1-3 pm-level surface displacements, an approach used in techniques such as piezoresponse force microscopy, atomic force acoustic microscopy, and ultrasonic force microscopy. Here, based on an analytical model of AFM cantilever vibrations, we demonstrate a guideline to quantify surface displacements with high accuracy by taking into account the cantilever shape at the first resonant contact mode, depending on the tip-sample contact stiffness. The approach has been experimentally verified and further developed for piezoresponse force microscopy (PFM) using well-defined ferroelectric materials. These results open up a way to accurate and precise measurements of surface displacement as well as piezoelectric constants at the pm-scale with nanometer spatial resolution and will allow avoiding erroneous data interpretations and measurement artifacts. This analysis is directly applicable to all cantilever-resonance-based scanning probe microscopy (SPM) techniques.
- 21Killgore, J. P.; Robinsa, L.; Collins, L. Electrostatically-blind Quantitative Piezoresponse Force Microscopy Free of Distributed-Force Artifacts. Nanoscale Adv. 2022, 4, 2036– 2045, DOI: 10.1039/D2NA00046FGoogle ScholarThere is no corresponding record for this reference.
- 22Sharma, P.; Ryu, S.; Viskadourakis, Z.; Paudel, T. R.; Lee, H.; Panagopoulos, C.; Tsymbal, E. Y.; Eom, C.-B.; Gruverman, A. Electromechanics of Ferroelectric-like Behavior of LaAlO3 Thin Films. Adv. Funct. Mater. 2015, 25, 6538– 6544, DOI: 10.1002/adfm.201502483Google Scholar22https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhsFGktrbO&md5=fb5f17b3201646bffbab4d6ce979b62fElectromechanics of Ferroelectric-Like Behavior of LaAlO3 Thin FilmsSharma, Pankaj; Ryu, Sangwoo; Viskadourakis, Zacharias; Paudel, Tula R.; Lee, Hyungwoo; Panagopoulos, Christos; Tsymbal, Evgeny Y.; Eom, Chang-Beom; Gruverman, AlexeiAdvanced Functional Materials (2015), 25 (41), 6538-6544CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA)Electromech. coupling in complex oxide heterostructures opens new possibilities for the development of a broad range of novel electronic devices with enhanced functionality. In this article, the switchable hysteretic electro-mech. behavior of cryst. epitaxial LaAlO3 (LAO) thin films assocd. with polarization induced by elec. and mech. stimuli is investigated. The field-time-dependent testing of the induced polarization states along with transport measurements and theor. modeling suggests that the ferroelec.-like response of the LAO thin films is mediated by the field-induced ion migration in the bulk of the film. Comparative anal. of the dynamics of polarization reversal under the elec. field and mech. stress applied via a tip of a scanning probe microscope demonstrates that both elec. and mech. stimulus can be used to effectively control polarization at least at the submillisecond timescale. However, the mech. writing is more localized than the elec. one. A combined elec./mech. approach for tuning the phys. properties of oxide hetero-structures may potentially facilitate novel memory and logic devices, in which the data bits are written mech. and read elec.
- 23Balke, N.; Jesse, S.; Li, Q.; Maksymovych, P.; Okatan, M. B.; Strelcov, E.; Tselev, A.; Kalinin, S. V. Current and Surface Charge Modified Hysteresis Loops in Ferroelectric Thin Films. J. Appl. Phys. 2015, 118, 072013, DOI: 10.1063/1.4927811Google Scholar23https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtlOgsrnN&md5=9a2eb140c5f65c65692d0080bd1953eeCurrent and surface charge modified hysteresis loops in ferroelectric thin filmsBalke, Nina; Jesse, Stephen; Li, Qian; Maksymovych, Petro; Baris Okatan, M.; Strelcov, Evgheni; Tselev, Alexander; Kalinin, Sergei V.Journal of Applied Physics (Melville, NY, United States) (2015), 118 (7), 072013/1-072013/8CODEN: JAPIAU; ISSN:0021-8979. (American Institute of Physics)Polarization domains in ferroelec. materials and the ability to orient them with an external elec. field lead to the development of a variety of applications from information storage to actuation. The development of piezoresponse force microscopy (PFM) has enabled researchers to investigate ferroelec. domains and ferroelec. domain switching on the nanoscale, which offers a pathway to study structure-function relationships in this important material class. Due to its com. availability and ease of use, PFM has become a widely used research tool. However, measurement artifacts, i.e., alternative signal origins besides the piezoelec. effect are barely discussed or considered. This becomes esp. important for materials with a small piezoelec. coeff. or materials with unknown ferroelec. properties, including non-ferroelec. materials. Here, the role of surface charges and current flow during PFM measurements on classical ferroelecs. are discussed and it will be shown how they alter the PFM hysteresis loop shape. This will help to better address alternative signal origins in PFM-type expts. and offer a pathway to study addnl. phenomena besides ferroelectricity. (c) 2015 American Institute of Physics.
- 24Lu, H.; Glinsek, S.; Buragohain, P.; Defay, E.; Iñiguez, J.; Gruverman, A. Probing Antiferroelectric-Ferroelectric Phase Transitions in PbZrO3 Capacitors by Piezoresponse Force Microscopy. Adv. Funct. Mater. 2020, 30, 2003622, DOI: 10.1002/adfm.202003622Google ScholarThere is no corresponding record for this reference.
- 25Buragohain, P.; Erickson, A.; Mimura, T.; Shimizu, T.; Funakubo, H.; Gruverman, A. Effect of Film Microstructure on Domain Nucleation and Intrinsic Switching in Ferroelectric Y:HfO2 Thin Film Capacitors. Adv. Funct. Mater. 2022, 32, 2108876, DOI: 10.1002/adfm.202108876Google Scholar25https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXisF2gsbnE&md5=fe74eab4ae0897caa3cf25ffca3c0f84Effect of Film Microstructure on Domain Nucleation and Intrinsic Switching in Ferroelectric Y:HfO2 Thin Film CapacitorsBuragohain, Pratyush; Erickson, Adam; Mimura, Takanori; Shimizu, Takao; Funakubo, Hiroshi; Gruverman, AlexeiAdvanced Functional Materials (2022), 32 (9), 2108876CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA)One of the general features of ferroelec. systems is a complex nature of polarization reversal, which involves domain nucleation and motion of domain walls. Here, time-resolved nanoscale domain imaging is applied in conjunction with the integral switching current measurements to investigate the mechanism of polarization reversal in yttrium-doped HfO2 (Y:HfO2)-currently one of the most actively studied ferroelec. systems. More specifically, the effect of film microstructure on the nucleation process is investigated by performing a comparative study of the polarization switching behavior in the epitaxial and polycryst. Y:HfO2 thin film capacitors. It is found that although the epitaxial Y:HfO2 capacitors tend to switch slower than their polycryst. counterparts, they exhibit a significantly higher nucleation d. and rate, suggesting that this is a rate-limiting mechanism. In addn., it is obsd. that under the external fields approaching the activation field value, the switching kinetics can be described equally well by the nucleation limited switching and the Kolmogorov-Avrami-Ishibashi models for both types of capacitors. This signifies convergence of two different mechanisms implying that the polarization reversal proceeds via a homogeneous nucleation process unaffected by the film microstructure, which can be considered as approaching the intrinsic switching limit.
- 26Tan, H.; Lyu, J.; Sheng, Y.; Machado, P.; Song, T.; Bhatnagar, A.; Coll, M.; Sanchez, F.; Fontcuberta, J.; Fina, I. A Transversal Approach to Predict Surface Charge Compensation in Piezoelectric Force Microscopy. Appl. Surf. Sci. 2023, 607, 154991, DOI: 10.1016/j.apsusc.2022.154991Google Scholar26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38XisFSru7jI&md5=c40bcc576173e7e643a18e29ff958d31A transversal approach to predict surface charge compensation in piezoelectric force microscopyTan, Huan; Lyu, Jike; Sheng, Yunwei; Machado, Pamela; Song, Tingfeng; Bhatnagar, Akash; Coll, Mariona; Sanchez, Florencio; Fontcuberta, Josep; Fina, IgnasiApplied Surface Science (2023), 607 (), 154991CODEN: ASUSEE; ISSN:0169-4332. (Elsevier B.V.)Piezoelec. force microscopy (PFM) has demonstrated to be a powerful tool to characterize ferroelec. materials. However, extrinsic effects, most notably, those resulting from surface charges, often mask or mirror genuine piezoelec. response, challenging PFM data understanding. The contribution of surface charges to PFM signal is commonly compensated by using appropriate external bias voltage, which is ad-hoc selected and sample dependent. Here, we det. the compensating voltage in thin films of different ferroelec. materials and we compare with the corresponding I-V characteristics recorded using suitable electrodes. It turns out that the sign and magnitude of the bias voltage required to compensate the surface charges are related to the asymmetry of the I-V characteristics. We propose that this relation results from the fact that the semiconducting properties of the material det. both the I-V dependence, and the sign of charged adsorbates. We show how to make use of this correlation to predict the required compensation voltage of a non-ferroelec. material and we show that spurious piezoelec.-like contributions are largely cancelled. The results provide guidelines to mitigate common extrinsic contributions in PFM imaging.
- 27Labuda, A.; Proksch, R. Quantitative Measurements of Electromechanical Response With a Combined Optical Beam and Interferometric Atomic Force Microscope. Appl. Phys. Lett. 2015, 106, 253103, DOI: 10.1063/1.4922210Google Scholar27https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtVyns7%252FM&md5=bc1ec04c0b84304ccb7e89c9e36bbb51Quantitative measurements of electromechanical response with a combined optical beam and interferometric atomic force microscopeLabuda, Aleksander; Proksch, RogerApplied Physics Letters (2015), 106 (25), 253103/1-253103/4CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)An ongoing challenge in at. force microscope (AFM) expts. is the quant. measurement of cantilever motion. The vast majority of AFMs use the optical beam deflection (OBD) method to infer the deflection of the cantilever. The OBD method is easy to implement, has impressive noise performance, and tends to be mech. robust. However, it represents an indirect measurement of the cantilever displacement, since it is fundamentally an angular rather than a displacement measurement. Here, we demonstrate a metrol. AFM that combines an OBD sensor with a laser Doppler vibrometer (LDV) to enable accurate measurements of the cantilever velocity and displacement. The OBD/LDV AFM allows a host of quant. measurements to be performed, including in-situ measurements of cantilever oscillation modes in piezoresponse force microscopy. As an example application, we demonstrate how this instrument can be used for accurate quantification of piezoelec. sensitivity-a longstanding goal in the electromech. community. (c) 2015 American Institute of Physics.
- 28Gruverman, A.; Rodriguez, B. J.; Kingon, A. I.; Nemanich, R. J.; Cross, J. S.; Tsukada, M. Spatial Inhomogeneity of Imprint and Switching Behavior in Ferroelectric Capacitors. Appl. Phys. Lett. 2003, 82, 3071– 3073, DOI: 10.1063/1.1570942Google Scholar28https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXjsVSqtrw%253D&md5=fdda9514f3a77ae2eb2029d1d2978681Spatial inhomogeneity of imprint and switching behavior in ferroelectric capacitorsGruverman, A.; Rodriguez, B. J.; Kingon, A. I.; Nemanich, R. J.; Cross, J. S.; Tsukada, M.Applied Physics Letters (2003), 82 (18), 3071-3073CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)Piezoresponse force microscopy has been used to perform nanoscale characterization of the spatial variations in the imprint and switching behavior of (111)-oriented Pb(Zr,Ti)O3-based capacitors on Pt electrodes. Mapping of polarization distribution in the poled capacitors as well as local d33-V loop measurements revealed a significant difference in imprint and switching behavior between the peripheral and inner parts of the capacitors. It has been found that the inner regions of the capacitors are neg. imprinted (with the preferential direction of the normal component of polarization upward) and tend to switch back after application of the pos. poling voltage. On the other hand, switchable regions at the edge of the integrated capacitors generally exhibit more sym. hysteresis behavior. Application of an ac switching voltage, contrary to what was expected, resulted in an increase of the neg. imprinted regions. The obsd. effect has been explained by incomplete or asym. switching due to the mech. stress conditions existing in the central parts of the capacitors.
- 29Christman, J. A.; Kim, S.-H.; Maiwa, H.; Maria, J.-P.; Rodriguez, B. J.; Kingon, A. I.; Nemanich, R. J. Spatial Variation of Ferroelectric Properties in Pb(Zr0.3,Ti0.7)O3 Thin Films Studied by Atomic Force Microscopy. J. Appl. Phys. 2000, 87, 8031– 8034, DOI: 10.1063/1.373492Google ScholarThere is no corresponding record for this reference.
- 30Gruverman, A.; Auciello, O.; Tokumoto, H. Nanoscale Investigation of Fatigue Effects in Pb(Zr,Ti)O3 Films. Appl. Phys. Lett. 1996, 69, 3191– 3193, DOI: 10.1063/1.117957Google ScholarThere is no corresponding record for this reference.
- 31Zhou, Y.; Chan, H. K.; Lam, C. H.; Shin, F. G. Mechanisms of Imprint Effect on Ferroelectric Thin Films. J. Appl. Phys. 2005, 98, 024111, DOI: 10.1063/1.1984075Google Scholar31https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXntV2hsLk%253D&md5=fa811a82cb7e8c978f7cf98508aea009Mechanisms of imprint effect on ferroelectric thin filmsZhou, Y.; Chan, H. K.; Lam, C. H.; Shin, F. G.Journal of Applied Physics (2005), 98 (2), 024111/1-024111/9CODEN: JAPIAU; ISSN:0021-8979. (American Institute of Physics)We have developed a single/double layer model to explain horizontal shifting of measured D-E hysteresis loops (imprint) for ferroelec. thin films. Such phenomenon can be explained by considering three mechanisms or their multiple effects: (1) stress induced by film/electrode lattice mismatch or clamping, (2) domain pinning induced by, e.g., oxygen vacancies, or (3) degrdn. of ferroelec. properties in film/electrode surface layers. First, it is found that hysteresis loops under the influence of stress exhibit large horizontal shifts with magnitudes comparable to those obsd. in expts. Second, a pseudo-non-switching layer with a large coercive field is assumed to be present at the film/electrode interface in an otherwise homogeneous ferroelec. thin film, and in this case our simulation also shows a large imprint effect. Third, it is also found that time-dependent space-charge-limited conduction is likely to be one origin for the occurrence of imprint.
- 32Damodaran, A. R.; Breckenfeld, E.; Chen, Z.; Lee, S.; Martin, L. W. Enhancement of Ferroelectric Curie Temperature in BaTiO3 Films via Strain-Induced Defect Dipole Alignment. Adv. Mater. 2014, 26, 6341– 6347, DOI: 10.1002/adma.201400254Google Scholar32https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXht1Kksb%252FI&md5=9c5d52fa268d034a7134a29212a81f62Enhancement of Ferroelectric Curie Temperature in BaTiO3 Films via Strain-Induced Defect Dipole AlignmentDamodaran, Anoop R.; Breckenfeld, Eric; Chen, Zuhuang; Lee, Sungki; Martin, Lane W.Advanced Materials (Weinheim, Germany) (2014), 26 (36), 6341-6347CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)The coupling between epitaxial strain and defect dipoles that form due to the pulsed-laser deposition growth process to controllably tune the TC of BaTiO3 to over 800° C is explored. Purely epitaxial strain-based approaches for TC enhancement are limited by the magnitude of strain that can be applied, the thicknesses that can be achieved before film relaxation, and a lack of strain tunability. It is shown in this work that epitaxial strain can be used to control the ordering of defect dipoles inducing addnl. out-of-plane strains and enabling controlled enhancement of TC without the need to change substrates. This is esp. exciting since neither the polarization nor the leakage properties are diminished thereby enabling the measurement of well-defined ferroelec. hysteresis loops to at least 500° C. It should be noted that even in bulk crystals, aging can give rise to enhanced TC but the exact mechanism was not well understood nor is it known how to deterministically control the magnitude and nature of these effects. This work provides a new application to complex oxide ferroelecs. and represents an exciting discovery with implications for utilization of these materials in high-temp. applications.
- 33Buragohain, P.; Erickson, A.; Kariuki, P.; Mittmann, T.; Richter, C.; Lomenzo, P. D.; Lu, H.; Schenk, T.; Mikolajick, T.; Schroeder, U.; Gruverman, A. Fluid Imprint and Inertial Switching in Ferroelectric La:HfO2 Capacitors. ACS Appl. Mater. Interfaces 2019, 11, 35115– 35121, DOI: 10.1021/acsami.9b11146Google Scholar33https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhs1Kks7vF&md5=fd593338a0658d401b5bf1a813595878Fluid imprint and inertial switching in ferroelectric La:HfO2 capacitorsBuragohain, Pratyush; Erickson, Adam; Kariuki, Pamenas; Mittmann, Terence; Richter, Claudia; Lomenzo, Patrick D.; Lu, Haidong; Schenk, Tony; Mikolajick, Thomas; Schroeder, Uwe; Gruverman, AlexeiACS Applied Materials & Interfaces (2019), 11 (38), 35115-35121CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)Ferroelec. (FE) HfO2-based thin films, which are considered as one of the most promising material systems for memory device applications, exhibit an adverse tendency for strong imprint. Manifestation of imprint is a shift of the polarization-voltage (P-V) loops along the voltage axis due to the development of an internal elec. bias, which can lead to the failure of the writing and retention functions. Here, to gain insight into the mechanism of the imprint effect in La-doped HfO2 (La:HfO2) capacitors, we combine the pulse switching technique with high-resoln. domain imaging by means of piezoresponse force microscopy. This approach allows us to establish a correlation between the macroscopic switching characteristics and domain time-voltage-dependent behavior. It has been shown that the La:HfO2 capacitors exhibit a much more pronounced imprint compared to Pb(Zr,Ti)O3-based FE capacitors. Also, in addn. to conventional imprint, which evolves with time in the poled capacitors, an easily changeable imprint, termed as "fluid imprint", with a strong dependence on the switching prehistory and measurement conditions, has been obsd. Visualization of the domain structure reveals a specific signature of fluid imprint-continuous switching of polarization in the same direction as the previously applied field that continues a long time after the field was turned off. This effect, termed as "inertial switching", is attributed to charge injection and subsequent trapping at defect sites at the film-electrode interface.
- 34Alcala, R.; Materano, M.; Lomenzo, P. D.; Vishnumurthy, P.; Hamouda, W.; Dubourdieu, C.; Kersch, A.; Barrett, N.; Mikolajick, T.; Schroede, U. The Electrode-Ferroelectric Interface as the Primary Constraint on Endurance and Retention in HZO-Based Ferroelectric Capacitors. Adv. Funct. Mater. 2023, 23, 2303261, DOI: 10.1002/adfm.202303261Google ScholarThere is no corresponding record for this reference.
- 35Lee, H.; Kim, T. H.; Patzner, J. J.; Lu, H.; Lee, J. W.; Zhou, H.; Chang, W.; Mahanthappa, M. K.; Tsymbal, E. Y.; Gruverman, A.; Eom, C. B. Imprint Control of BaTiO3 Thin Films via Chemically Induced Surface Polarization Pinning. Nano Lett. 2016, 16, 2400– 2406, DOI: 10.1021/acs.nanolett.5b05188Google Scholar35https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XivFOgu70%253D&md5=3b43a8ba1fd3cc504da391b648244a64Imprint Control of BaTiO3 Thin Films via Chemically Induced Surface Polarization PinningLee, Hyungwoo; Kim, Tae Heon; Patzner, Jacob J.; Lu, Haidong; Lee, Jung-Woo; Zhou, Hua; Chang, Wansoo; Mahanthappa, Mahesh K.; Tsymbal, Evgeny Y.; Gruverman, Alexei; Eom, Chang-BeomNano Letters (2016), 16 (4), 2400-2406CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)Surface-adsorbed polar mols. can significantly alter the ferroelec. properties of oxide thin films. Thus, fundamental understanding and controlling the effect of surface adsorbates are crucial for the implementation of ferroelec. thin film devices, such as ferroelec. tunnel junctions. Herein, we report an imprint control of BaTiO3 (BTO) thin films by chem. induced surface polarization pinning in the top few at. layers of the water-exposed BTO films. Our studies based on synchrotron X-ray scattering and coherent Bragg rod anal. demonstrate that the chem. induced surface polarization is not switchable but reduces the polarization imprint and improves the bistability of ferroelec. phase in BTO tunnel junctions. We conclude that the chem. treatment of ferroelec. thin films with polar mols. may serve as a simple yet powerful strategy to enhance functional properties of ferroelec. tunnel junctions for their practical applications.
- 36Tan, H.; Castro, G.; Lyu, J.; Loza-Alvarez, P.; Sanchez, F.; Fontcuberta, J.; Fina, I. Control of up-to-down/down-to-up Light-induced Ferroelectric Polarization Reversal Mater. Horiz. 2022, 9, 2345– 2352, DOI: 10.1039/D2MH00644HGoogle ScholarThere is no corresponding record for this reference.
- 37Long, X.; Tan, H.; Sánchez, F.; Fina, I.; Fontcuberta, J. Non-Volatile Optical Switch of Resistance in Photoferroelectric Tunnel Junctions. Nat. Coummn 2021, 12, 382, DOI: 10.1038/s41467-020-20660-9Google ScholarThere is no corresponding record for this reference.
- 38Alikin, D.; Abramov, A.; Turygin, A.; Ievlev, A.; Pryakhina, V.; Karpinsky, D.; Hu, Q.; Jin, L.; Shur, V.; Tselev, A.; Kholkin, A. Exploring Charged Defects in Ferroelectrics by the Switching Spectroscopy Piezoresponse Force Microscopy. Small Methods 2022, 6, 2101289, DOI: 10.1002/smtd.202101289Google ScholarThere is no corresponding record for this reference.
- 39Balke, N.; Maksymovych, P.; Jesse, S.; Herklotz, A.; Tselev, A.; Eom, C.-B.; Kravchenko, I. I.; Yu, P.; Kalinin, S. V. Differentiating Ferroelectric and Nonferroelectric Electromechanical Effects With Scanning Probe Microscopy. ACS Nano 2015, 9, 6484– 6492, DOI: 10.1021/acsnano.5b02227Google Scholar39https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXpsFalu74%253D&md5=81a7f07498af83064bae16808dcdda74Differentiating Ferroelectric and Nonferroelectric Electromechanical Effects with Scanning Probe MicroscopyBalke, Nina; Maksymovych, Petro; Jesse, Stephen; Herklotz, Andreas; Tselev, Alexander; Eom, Chang-Beom; Kravchenko, Ivan I.; Yu, Pu; Kalinin, Sergei V.ACS Nano (2015), 9 (6), 6484-6492CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)Ferroelectricity in functional materials remains one of the most fascinating areas of modern science in the past several decades. In the last several years, the rapid development of piezoresponse force microscopy (PFM) and spectroscopy revealed electromech. hysteresis loops and bias-induced remnant polar states in a broad variety of materials including many inorg. oxides, polymers, and biosystems. In many cases, this behavior was interpreted as the ample evidence for ferroelec. nature of the system. Here, the authors systematically analyze PFM responses on ferroelec. and nonferroelec. materials and demonstrate that mechanisms unrelated to ferroelectricity can induce ferroelec.-like characteristics through charge injection and electrostatic forces on the tip. The authors will focus on similarities and differences in various PFM measurement characteristics to provide an exptl. guideline to differentiate between ferroelec. material properties and charge injection. In the end, the authors apply the developed measurement protocols to an unknown ferroelec. material.
- 40Buragohain, P.; Richter, C.; Schenk, T.; Lu, H.; Mikolajick, T.; Schroeder, U.; Gruverman, A. Nanoscopic Studies of Domain Structure Dynamics in Ferroelectric La:HfO2 Capacitors. Appl. Phys. Lett. 2018, 112, 222901, DOI: 10.1063/1.5030562Google Scholar40https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhtVGit73K&md5=078ffc0f4619f8677118a6adef888689Nanoscopic studies of domain structure dynamics in ferroelectric La:HfO2 capacitorsBuragohain, P.; Richter, C.; Schenk, T.; Lu, H.; Mikolajick, T.; Schroeder, U.; Gruverman, A.Applied Physics Letters (2018), 112 (22), 222901/1-222901/5CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)Visualization of domain structure evolution under an elec. bias has been carried out in ferroelec. La:HfO2 capacitors by a combination of Piezoresponse Force Microscopy (PFM) and pulse switching techniques to study the nanoscopic mechanism of polarization reversal and the wake-up process. It has been directly shown that the main mechanism behind the transformation of the polarization hysteretic behavior and an increase in the remanent polarization value upon the a.c. cycling is elec. induced domain de-pinning. PFM imaging and local spectroscopy revealed asym. switching in the La:HfO2 capacitors due to a significant imprint likely caused by the different boundary conditions at the top and bottom interfaces. Domain switching kinetics can be well-described by the nucleation limited switching model characterized by a broad distribution of the local switching times. It has been found that the domain velocity varies significantly throughout the switching process indicating strong interaction with structural defects. (c) 2018 American Institute of Physics.
- 41Wu, D.; Vrejoiu, I.; Alexe, M.; Gruverman, A. Anisotropy of Domain Growth in Epitaxial Ferroelectric Capacitors. Appl. Phys. Lett. 2010, 96, 112903, DOI: 10.1063/1.3366724Google ScholarThere is no corresponding record for this reference.
- 42Gruverman, A.; Rodriguez, B. J.; Kingon, A. I.; Nemanich, R. J.; Tagantsev, A. K.; Cross, J. S.; Tsukada, M. Mechanical Stress Effect on Imprint Behavior of Integrated Ferroelectric Capacitors. Appl. Phys. Lett. 2003, 83, 728– 730, DOI: 10.1063/1.1593830Google Scholar42https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXlvVWlsLs%253D&md5=e4a85ba7a342a7490c1ed830d1654059Mechanical stress effect on imprint behavior of integrated ferroelectric capacitorsGruverman, A.; Rodriguez, B. J.; Kingon, A. I.; Nemanich, R. J.; Tagantsev, A. K.; Cross, J. S.; Tsukada, M.Applied Physics Letters (2003), 83 (4), 728-730CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)Stress-induced changes in the imprint and switching behavior of (111)-oriented Pb(Zr,Ti)O3 (PZT)-based capacitors have been studied using piezoresponse force microscopy. Visualization of polarization distribution and d33-loop measurements in individual 1×1.5-μm2 capacitors before and after stress application, generated by substrate bending, provided direct exptl. evidence of stress-induced switching. Mech. stress caused elastic switching in capacitors with the direction of the resulting polarization detd. by the sign of the applied stress. In addn., stress application turned capacitors into a heavily imprinted state characterized by strongly shifted hysteresis loops and almost complete backswitching after application of the poling voltage. It is suggested that substrate bending generated a strain gradient in the PZT layer, which produced asym. lattice distortion with preferential polarization direction and triggered polarization switching due to the flexoelec. effect.
- 43Miao, P.; Zhao, Y.; Luo, N.; Zhao, D.; Chen, A.; Sun, Z.; Guo, M.; Zhu, M.; Zhang, H.; Li, Q. Ferroelectricity and Self-Polarization in Ultrathin Relaxor Ferroelectric Films. Sci. Rep. 2016, 6, 19965, DOI: 10.1038/srep19965Google Scholar43https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhslOgsb4%253D&md5=3db969d2500e70216afd7945eac6601bFerroelectricity and Self-Polarization in Ultrathin Relaxor Ferroelectric FilmsMiao, Peixian; Zhao, Yonggang; Luo, Nengneng; Zhao, Diyang; Chen, Aitian; Sun, Zhong; Guo, Meiqi; Zhu, Meihong; Zhang, Huiyun; Li, QiangScientific Reports (2016), 6 (), 19965CODEN: SRCEC3; ISSN:2045-2322. (Nature Publishing Group)We report ferroelectricity and self-polarization in the (001) oriented ultrathin relaxor ferroelec. PMN-PT films grown on Nb-SrTiO3, SrRuO3 and La0.7Sr0.3MnO3, resp. Resistance-voltage measurements and AC impedance anal. suggest that at high temps. Schottky depletion width in a 4 nm thick PMN-PT film deposited on Nb-SrTiO3 is smaller than the film thickness. We propose that Schottky interfacial dipoles make the dipoles of the nanometer-sized polar nanoregions (PNRs) in PMN-PT films grown on Nb-SrTiO3 point downward at high temps. and lead to the self-polarization at room temp. with the assistance of in-plane compressive strain. This work sheds light on the understanding of epitaxial strain effects on relaxor ferroelec. films and self-polarization mechanism.
- 44Ma, J.; Zhu, Y.; Tang, Y.; Han, M.; Wang, Y.; Zhang, N.; Zou, M.; Feng, Y.; Gengac, W.; Maa, X. Modulation of Charged a1/a2 Domains and Piezoresponses of Tensile Strained PbTiO3 Films by the Cooling Rate. RSC Adv. 2019, 9, 13981– 13990, DOI: 10.1039/C9RA02485AGoogle Scholar44https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXovFelsbs%253D&md5=a8e6bc029f3748045a2881094bd95204Modulation of charged a1/a2 domains and piezoresponses of tensile strained PbTiO3 films by the cooling rateMa, Jinyuan; Zhu, Yinlian; Tang, Yunlong; Han, Mengjiao; Wang, Yujia; Zhang, Ningbin; Zou, Minjie; Feng, Yanpeng; Geng, Wanrong; Ma, XiuliangRSC Advances (2019), 9 (25), 13981-13990CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)Controlling domain width, orientation, and patterns in oxide ferroelecs. are not only important for fundamental research but also for potential electronic application. Here, a series of PbTiO3 thin films under various cooling rates were deposited on (110)-oriented NdScO3 substrates by pulsed laser deposition and investigated by using conventional transmission electron microscopy, Cs-cor. scanning TEM and piezoresponse force microscopy. Contrast anal. and electron diffraction revealed that PbTiO3 films are a1/a2 domain patterns under large tensile strains with different cooling rates. The a1/a2 domains distribute periodically and the domain width increases with decrease in the cooling rates. Upon increasing the cooling rate, the domain d. increases and the domain configurations become complicated. There are special square frame-like domain patterns with charged domain walls found in the PTO films with the fast cooling rate. PFM measurement shows that the PTO films with high cooling rate exhibit enhanced piezoresponse behavior which is ascribed to the high d. domain/domain walls and special domain configurations. The formation mechanism of the different domain configurations is discussed in terms of the effect of cooling rates, defects and thermal kinetics. These results are expected to provide useful information for domain/domain wall control and thus facilitate further modulation of the properties for potential applications.
- 45Kos, A. B.; Killgore, J. P.; Hurley, D. C. SPRITE: A Modern Approach to Scanning Probe Contact Resonance Imaging Meas. Sci. Technol. 2014, 25, 025405, DOI: 10.1088/0957-0233/25/2/025405Google ScholarThere is no corresponding record for this reference.
- 46Jesse, S.; Kalinin, S. V.; Proksch, R.; Baddorf, A. P.; Rodriguez, B. J. The Band Excitation Method in Scanning Probe Microscopy for Rapid Mapping of Energy Dissipation on the. Nanoscale Nanotechnology 2007, 18, 435503, DOI: 10.1088/0957-4484/18/43/435503Google ScholarThere is no corresponding record for this reference.
- 47Rodriguez, B. J.; Callahan, C.; Kalinin, S. V.; Proksch, R. Dual-Frequency Fesonance-Tracking Atomic Force Microscopy Nanotechnology 2007, 18 475504. DOI: 10.1088/0957-4484/18/47/475504Google ScholarThere is no corresponding record for this reference.
- 48Zhang, Q.; Huang, H. H.; Sando, D.; Summers, M.; Munroe, P.; Standarda, O.; Valanoor, N. Mixed-Phase Bismuth Ferrite Thin Films by Chemical Solution Deposition. J. Mater. Chem. C 2018, 6, 2882– 2888, DOI: 10.1039/C7TC05841AGoogle Scholar48https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXivFSntLY%253D&md5=3c4d5948365604664e82be5abb09318fMixed-phase bismuth ferrite thin films by chemical solution depositionZhang, Qi; Huang, Hsin-Hui; Sando, Daniel; Summers, Max; Munroe, Paul; Standard, Owen; Valanoor, NagarajanJournal of Materials Chemistry C: Materials for Optical and Electronic Devices (2018), 6 (11), 2882-2888CODEN: JMCCCX; ISSN:2050-7534. (Royal Society of Chemistry)Epitaxial mixed-phase bismuth ferrite (BiFeO3, BFO) thin films were successfully synthesized on (001) lanthanum aluminate (LaAlO3, LAO) substrates by a chem. soln. deposition (CSD) technique. X-ray diffraction measurements confirm the co-existence of a completely relaxed rhombohedral-like (R') phase and a strained tetragonal-like (T') phase. Atomic resoln. scanning transmission electron microscopy (STEM) measurements reveal that the T' and R' phases in our CSD derived BFO/LAO films are mixed homogeneously at the nanoscale. This is in stark contrast to the typical phys. vapor deposition-derived mixed-phase BFO thin films, which show R' phase striations embedded in a T' phase matrix. This phenomenon is attributed to the specific deposition-nucleation-crystn.-relaxation pathway characteristic of the CSD route. This homogenously mixed-phase still demonstrates the well-known morphotropic phase boundary effect, i.e. superior electromech. properties compared to either the pure T' phase or R' phase constituents themselves. Moreover, the max. piezoelec. coeff. measured by using nanoscale top electrodes shows surprising insensitivity to the clamping effect from the substrate, thereby offering considerable promise in thin film applications.
- 49Zhou, J.; Sando, D.; Cheng, X.; Ma, Z.; Valanoor, N.; Zhang, Q. Tuning Phase Fractions and Leakage Properties of Chemical Solution Deposition-Derived Mixed-Phase BiFeO3 Thin Films. ACS Appl. Electron. Mater. 2020, 2, 4099– 4110, DOI: 10.1021/acsaelm.0c00891Google Scholar49https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXisFSqu7%252FP&md5=acbe6731f29897fbced50fe5d0cdeb64Tuning Phase Fractions and Leakage Properties of Chemical Solution Deposition-Derived Mixed-Phase BiFeO3 Thin FilmsZhou, Jinling; Sando, Daniel; Cheng, Xuan; Ma, Zhijun; Valanoor, Nagarajan; Zhang, QiACS Applied Electronic Materials (2020), 2 (12), 4099-4110CODEN: AAEMBP; ISSN:2637-6113. (American Chemical Society)Phase-pure epitaxial bismuth ferrite (BiFeO3, BFO) thin films with a homogeneous mixed-phase structure were synthesized on (001)-oriented lanthanum aluminate (LaAlO3, LAO) substrates using chem. soln. deposition. The phase development of the BFO thin film and its leakage current characteristics have been systematically investigated as a function of thickness (no. of spin-coated layers) and the heat treatment process (heating temp. and dwell time). The results show that the tetragonal-like (T') phase fraction changes dramatically from 35% (45 nm thick single layer) to 10% (250 nm thick four-layer films). In a two-layer film (80 nm) configuration, the T'-phase fraction was further tuned. When annealing at 640°C for 30 min, this mixed-phase BFO film, despite its high T'-phase fraction (28%), shows the lowest leakage current (<0.1 A/cm2 at <500 kV/cm), comparable to 200 nm pulsed laser deposition-grown pure R-BFO thin films. In contrast to the obsd. bulk-limited Ohmic or space-charge-limited-conduction (SCLC)-predominant mechanism in pure R'-phase and low T'-phase fraction BFO thin films, the high T'-phase fraction (~ 28%) mixed-phase BFO film displays an interface-limited Schottky emission to an SCLC mechanism transition with increasing elec. field.
- 50Yang, S. Y.; Martin, L. W.; Byrnes, S. J.; Conry, T. E.; Basu, S. R.; Paran, D.; Reichertz, L.; Ihlefeld, J.; Adamo, C.; Melville, A.; Chu, Y.-H.; Yang, C.-H.; Musfeldt, J. L.; Schlom, D. G.; Ager III, J. W.; Ramesh, R. Photovoltaic Effects in BiFeO3. Appl. Phys. Lett. 2009, 95, 062909, DOI: 10.1063/1.3204695Google Scholar50https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXhtVSiurbJ&md5=e2e200bd78e874bbb266c55f057727a2Photovoltaic effects in BiFeO3Yang, S. Y.; Martin, L. W.; Byrnes, S. J.; Conry, T. E.; Basu, S. R.; Paran, D.; Reichertz, L.; Ihlefeld, J.; Adamo, C.; Melville, A.; Chu, Y.-H.; Yang, C.-H.; Musfeldt, J. L.; Schlom, D. G.; Ager, J. W., III; Ramesh, R.Applied Physics Letters (2009), 95 (6), 062909/1-062909/3CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)We report a photovoltaic effect in ferroelec. BiFeO3 thin films. The all-oxide heterostructures with SrRuO3 bottom and Sn doped In oxide top electrodes are characterized by open-circuit voltages ∼0.8-0.9 V and external quantum efficiencies up to ∼10% when illuminated with the appropriate light. Efficiencies are at least an order of magnitude larger than the max. efficiency under sunlight (AM 1.5) thus far reported for ferroelec.-based devices. The dependence of the measured open-circuit voltage on film thickness suggests contributions to the large open-circuit voltage from both the ferroelec. polarization and band offsets at the BiFeO3/Sn doped In oxide interface. (c) 2009 American Institute of Physics.
- 51Jesse, S.; Lee, H. N.; Kalinin, S. V. Quantitative Mapping of Switching Behavior in Piezoresponse Force Microscopy Rev. Sci. 2006, 77, 073702, DOI: 10.1063/1.2214699Google ScholarThere is no corresponding record for this reference.
- 52Augurio, A.; Alvarez-Fernandez, A.; Panchal, V.; Pittenger, B.; Wolf, P. De; Guldin, S.; Briscoe, J. Controlled Porosity in Ferroelectric BaTiO3 Photoanodes. ACS Appl. Mater. Interfaces 2022, 14, 13147– 13157, DOI: 10.1021/acsami.1c17419Google Scholar52https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38XmsFeis78%253D&md5=ec550411426ee17de9ae54cb224cd24aControlled Porosity in Ferroelectric BaTiO3 PhotoanodesAugurio, Adriana; Alvarez-Fernandez, Alberto; Panchal, Vishal; Pittenger, Bede; De Wolf, Peter; Guldin, Stefan; Briscoe, JoeACS Applied Materials & Interfaces (2022), 14 (11), 13147-13157CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)The use of ferroelec. polarization to promote electron-hole sepn. has emerged as a promising strategy to improve photocatalytic activity. Although ferroelec. thin films with planar geometry have been largely studied, nanostructured and porous ferroelec. thin films have not been commonly used in photo-electrocatalysis. The inclusion of porosity in ferroelec. thin films would enhance the surface area and reactivity, leading to a potential improvement of the photoelectrochem. (PEC) performance. Herein, the prepn. of porous barium titanate (pBTO) thin films by a soft template-assisted sol-gel method is reported, and the control of porosity using different org./inorg. ratios is verified by the combination of SEM and ellipsometry techniques. Using piezoresponse force microscopy, the switching of ferroelec. domains in pBTO thin films is obsd., confirming that the ferroelec. polarization is still retained in the porous structures. In addn., the presence of porosity in pBTO thin films leads to a clear improvement of the PEC response. By electrochem. poling, we also demonstrated the tuning of the PEC performance of pBTO thin films via ferroelec. polarization. Our work offers a simple and low-cost approach to control the morphol. optimization of ferroelec. thin films, which could open up the development of materials with great potential for PEC applications.
- 53Dwij, V.; De, B. K.; Rana, S.; Kunwar, H. S.; Yadav, S.; Sahu, S. R.; Venkatesh, R.; Lalla, N. P.; Phase, D. M.; Shukla, D. K.; Sathe, V. G. Optical Control of Domain Configuration Through Light Polarization in Ferroelectric BaTiO3. Phys. Rev. B 2022, 105, 134103, DOI: 10.1103/PhysRevB.105.134103Google Scholar53https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38Xhtlags7jK&md5=f455c40b08e9748bc7045606f4acf6b1Optical control of domain configuration through light polarization in ferroelectric BaTiO3Dwij, Vivek; De, Binoy Krishna; Rana, Sumesh; Kunwar, Hemant Singh; Yadav, Satish; Sahu, Shikha Rani; Venkatesh, R.; Lalla, N. P.; Phase, D. M.; Shukla, D. K.; Sathe, V. G.Physical Review B (2022), 105 (13), 134103CODEN: PRBHB7; ISSN:2469-9969. (American Physical Society)Optical control and switching of domain configuration are intriguing to overcome the sluggish time response, hysteresis, and Joule heating losses present in conventional methods where resistive contacts are involved. The effective optical control of the domain configuration has remained challenging and far from fully understood. It has been reported that light polarization can be used to control the domain configuration in BaTiO3, however, without much focus on origin of its mechanism. By combining the exptl. techniques that are sensitive to the local and av. crystal structure and to elec. polarization and electronic structure, we detect and demonstrate the optically guided variations in the domain configurations of BaTiO3 and show that the strain field generated through the bulk photovoltaic effect plays a key role in domain reconfiguration. Complete mechanism of reversible domain control via light polarization is discussed.
- 54Dong, G.; Li, S.; Yao, M.; Zhou, Z.; Zhang, Y.-Q.; Han, X.; Luo, Z.; Yao, J.; Peng, B.; Hu, Z.; Huang, H.; Jia, T.; Li, J.; Ren, W.; Ye, Z.-G.; Ding, X.; Sun, J.; Nan, C.-W.; Chen, L.-Q.; Li, J.; Liu, M. Super-Elastic Ferroelectric Single-Crystal Membrane With Continuous Electric Dipole Rotation. Science 2019, 366, 475– 479, DOI: 10.1126/science.aay7221Google Scholar54https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXitVemtrnO&md5=7e5107e8db091f201d570a693bedfa6eSuper-elastic ferroelectric single-crystal membrane with continuous electric dipole rotationDong, Guohua; Li, Suzhi; Yao, Mouteng; Zhou, Ziyao; Zhang, Yong-Qiang; Han, Xu; Luo, Zhenlin; Yao, Junxiang; Peng, Bin; Hu, Zhongqiang; Huang, Houbing; Jia, Tingting; Li, Jiangyu; Ren, Wei; Ye, Zuo-Guang; Ding, Xiangdong; Sun, Jun; Nan, Ce-Wen; Chen, Long-Qing; Li, Ju; Liu, MingScience (Washington, DC, United States) (2019), 366 (6464), 475-479CODEN: SCIEAS; ISSN:1095-9203. (American Association for the Advancement of Science)High-quality ferroelec. materials, which polarize in response to an elec. field, are usually oxides that crack when bent. Dong et al. found that high-quality membranes of barium titanate are surprisingly flexible and super-elastic. These films accommodate large strains through dynamic evolution of nanodomains during deformation. This discovery is important for developing more robust flexible devices.
- 55Takada, K.; Takarae, S.; Shimamoto, K.; Fujimura, N.; Yoshimura, T. Time-Dependent Imprint in Hf0.5Zr0.5O2 Ferroelectric Thin Films. Adv. Electron. Mater. 2021, 7, 2100151, DOI: 10.1002/aelm.202100151Google Scholar55https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXhsVKls7fF&md5=2bfb27003a05554424174911121009afTime-Dependent Imprint in Hf0.5Zr0.5O2 Ferroelectric Thin FilmsTakada, Kenshi; Takarae, Shuya; Shimamoto, Kento; Fujimura, Norifumi; Yoshimura, TakeshiAdvanced Electronic Materials (2021), 7 (8), 2100151CODEN: AEMDBW; ISSN:2199-160X. (Wiley-VCH Verlag GmbH & Co. KGaA)The discovery of the HfO2-based ferroelec. films has opened new opportunities for using this silicon-compatible ferroelec. material to realize low-power logic circuits and high-d. non-volatile memories. The functional performances of ferroelecs. are intimately related to their dynamic response to external stimuli, such as elec. fields at finite temps. In the case of HfO2-based films, the time-dependent imprint and wake-up effect, which distinguish them from conventional ferroelecs., play important roles in understanding the remaining reliability issues, such as insufficient endurance. In this study, the time-dependent imprint process is carefully investigated using Hf0.5Zr0.5O2 (HZO) films with different ferroelec. properties and defect d. The amt. of redistributed charge, which causes imprint during polarization retention, is affected by the remanent polarization of the ferroelec. layer, suggesting that the depolarization field corresponding to the remanent polarization generates and works as a driving force of charge redistribution. The time-dependent measurement of the imprint distinguishes the origins of charge redistribution processes, which have different time consts. In addn., the correlation between the amt. of redistributed charge and the dielec. relaxation of the HZO films is discussed. Correlations are identified between the redistributed charge and the dielec. relaxation, indicating that the mobile charge contributes to the time-dependent imprint.
- 56Harrington, S. A.; Zhai, J.; Denev, S.; Gopalan, V.; Wang, H.; Bi, Z.; Redfern, S. A. T.; Baek, S.-H.; Bark, C. W.; Eom, C.-B.; Jia, Q.; Vickers, M. E.; MacManus-Driscoll, J. L. Thick Lead-Free Ferroelectric Films With High Curie Temperatures Through Nanocomposite-Induced. Strain Nat. Nanotechnol. 2011, 6, 491, DOI: 10.1038/nnano.2011.98Google Scholar56https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXotlCktL8%253D&md5=71b6c92a8b13627c3abc7267bd73cf72Thick lead-free ferroelectric films with high Curie temperatures through nanocomposite-induced strainHarrington, Sophie A.; Zhai, Junyi; Denev, Sava; Gopalan, Venkatraman; Wang, Haiyan; Bi, Zhenxing; Redfern, Simon A. T.; Baek, Seung-Hyub; Bark, Chung W.; Eom, Chang-Beom; Jia, Quanxi; Vickers, Mary E.; MacManus-Driscoll, Judith L.Nature Nanotechnology (2011), 6 (8), 491-495CODEN: NNAABX; ISSN:1748-3387. (Nature Publishing Group)Ferroelec. materials are used in applications ranging from energy harvesting to high-power electronic transducers. However, industry-std. ferroelec. materials contain lead, which is toxic and environmentally unfriendly. The preferred alternative, BaTiO3, is non-toxic and has excellent ferroelec. properties, but its Curie temp. of ∼130° is too low to be practical. Strain was used to enhance the Curie temp. of BaTiO3 and SrTiO3 films, but only for thicknesses of tens of nanometers, which is not thick enough for many device applications. Here, we increase the Curie temp. of micrometer-thick films of BaTiO3 to at least 330°, and the tetragonal-to-cubic structural transition temp. to beyond 800°, by interspersing stiff, self-assembled vertical columns of Sm2O3 throughout the film thickness. Lattice parameters are given. The columns, which are 10 nm in diam., strain the BaTiO3 matrix by 2.35%, forcing it to maintain its tetragonal structure and resulting in the highest BaTiO3 transition temps. so far.
- 57Lee, D.; Yoon, A.; Jang, S. Y.; Yoon, J.-G.; Chung, J.-S.; Kim, M.; Scott, J. F.; Noh, T. W. Giant Flexoelectric Effect in Ferroelectric Epitaxial Thin Films. Phys. Rev. Lett. 2011, 107, 057602, DOI: 10.1103/PhysRevLett.107.057602Google Scholar57https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXps1ent7Y%253D&md5=dc382c13be982ab3c707b993a2385acfGiant flexoelectric effect in ferroelectric epitaxial thin filmsLee, D.; Yoon, A.; Jang, S.-Y.; Yoon, J.-G.; Chung, J.-S.; Kim, M.; Scott, J. F.; Noh, T.-W.Physical Review Letters (2011), 107 (5), 057602/1-057602/4CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)We report on nanoscale strain gradients in ferroelec. HoMnO3 epitaxial thin films, resulting in a giant flexoelec. effect. Using grazing-incidence in-plane x-ray diffraction, we measured strain gradients in the films, which were 6 or 7 orders of magnitude larger than typical values reported for bulk oxides. The combination of TEM, elec. measurements, and electrostatic calcns. showed that flexoelectricity provides a means of tuning the phys. properties of ferroelec. epitaxial thin films, such as domain configurations and hysteresis curves.
Cited By
This article has not yet been cited by other publications.
Article Views
Altmetric
Citations
Article Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.
Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.
The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated.
Recommended Articles
Abstract
Figure 1
Figure 1. Phase sweep with respect to frequency, PFM phase image, and domain distribution of the BFO thin film measured under (a–c) uncalibrated conditions. After electrical writing, PFM phase images and domain distribution of a BFO thin film in (d) uncalibrated, (e) partially calibrated (autocalibrated), and (f) fully calibrated conditions. Images were taken in 6 × 6 μm2 after ±10 V poling in the 4 × 4 and 2 × 2 μm2 areas, respectively. Phase sweep with respect to frequency, PFM phase image, and domain distribution of the BFO thin film measured under (g–i) calibrated conditions.
Figure 2
Figure 2. (a) The schematic of single-segment SS-PFM script showing the voltage waveform in bias on and off conditions. (b) Example multisegment SS-PFM script displaying write and three read voltage steps, where read voltage steps are −1, 0, and +1 V. (c −g) PFM phase and amplitude hysteresis loop of a BFO thin film measured for −0.50 to +0.50 V read voltages, respectively. The electrostatically neutral phase amplitude loop is displayed in part d. (h) KPFM image (2 × 2 μm2) and (i) KPFM line scan of the BFO thin film in the measured SS-PFM area.
Figure 3
Figure 3. (a–e) PFM phase and amplitude hysteresis loop of a BTO single crystal for −1 to +1 V read voltage segments. (f) KPFM image (1 × 1 μm2) and (g) KPFM line scan in the measured SS-PFM area.
Figure 4
Figure 4. (a, d) Phase versus bias voltage and (b, e) switching voltage measured at the correct Vr value obtained from several measurements for a BTO single crystal and BFO thin film, respectively. (c and f) Variation of imprint voltage obtained under different Vr values.
Figure 5
Figure 5. PFM phase response exhibiting the ferroelectric domain switching behavior and phase loops of (a and c) BTO and (b and d) BTO:SmO VAN structures. Images were taken in 6 × 6 μm2 after ±10 V poling in the 4 × 4 and 2 × 2 um2 areas, respectively. (e) The imprint voltages for BTO and BTO:SmO VAN structures.
Figure 6
Figure 6. (a, b, and c) PFM phase, amplitude, and KPFM potential of a BTO:MgO VAN structure of an 8 × 8 um2 area after ±10 V poling in the 4 × 4 and 2 × 2 um2 areas, respectively. (d) Imprint voltage extracted from the sample at the unpoled, positive, and negative poled conditions using Vr values obtained locally within each region as shown in part (c).
Figure 7
Figure 7. Coercive voltage map acquired from the forward (a) and backward (b) voltage sweeps in a 15 × 10 μm2 area, with the respective amplitude sweeps from a selection of pixels shown below, as indicated by the arrows. (c) Imprint voltage map and (d) corresponding PFM phase image of a BTO crystal.
References
This article references 57 other publications.
- 1Gruverman, A.; Alexe, M.; Meier, D. Piezoresponse Force Microscopy and Nanoferroic Phenomena. Nat. Coummn 2019, 10, 1661, DOI: 10.1038/s41467-019-09650-8There is no corresponding record for this reference.
- 2Hong, S.; Woo, J.; Shin, H.; Jeon, J. U.; Pak, Y. E.; Colla, E. L.; Setter, N.; Kim, E.; No, K. Principle of Ferroelectric Domain Imaging Using Atomic Force Microscope. J. Appl. Phys. 2001, 89, 1377– 1386, DOI: 10.1063/1.13316542https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3MXmvFeg&md5=3e38939ff395d43144bc7400c03dad5aPrinciple of ferroelectric domain imaging using atomic force microscopeHong, Seungbum; Woo, Jungwon; Shin, Hyunjung; Jeon, Jong Up; Pak, Y. Eugene; Colla, Enrico L.; Setter, Nava; Kim, Eunah; No, KwangsooJournal of Applied Physics (2001), 89 (2), 1377-1386CODEN: JAPIAU; ISSN:0021-8979. (American Institute of Physics)The contrast mechanisms of domain imaging expts. assisted by at. force microscope (AFM) have been investigated by model expts. on nonpiezoelec. (silicon oxide) and piezoelec. [Pb(Zr,Ti)O3] thin films. The first step was to identify the electrostatic charge effects between the tip, the cantilever, and the sample surface. The second step was to explore the tip-sample piezoelec. force interaction. The static deflection of the cantilever was measured as a function of dc bias voltage (Vdc) applied to the bottom electrode (n-type Si wafers) for noncontact and contact modes. In addn., a small ac voltage (Vac[hthinsp]sin[hthinsp]ωt) was applied to the tip to measure the amplitude (Aω) and phase ([Fgr]ω) of the first harmonic (ω) signal as a function of Vdc. By changing from the noncontact to the contact mode, a repulsive contribution to the static deflection was found in addn. to the attractive one and a 180° phase shift in [Fgr]ω was obsd. These results imply that in the contact mode the cantilever buckling is induced by the capacitive force between the cantilever and the sample surface. This interaction adds to the tip-sample piezoelec. interaction thereby overlapping the obtained tip vibration signal. Therefore, the antiparallel ferroelec. domain images obtained at zero dc bias voltage will show a variation in Aω but a negligible one in [Fgr]ω. The capacitive force contribution to the tip vibration signal was further verified in piezoelec. hysteresis loop measurement assisted by the AFM. The obsd. vertical offset of the loops was explained by the contact p.d. between the cantilever and the bottom electrode. The shape of the curve could be explained by the capacitive force interaction combined with the tip-sample piezoelec. interaction. The exptl. results obtained in this study support the interpretation of the cantilever-sample capacitive force contribution to the tip vibration signal in ferroelec. domain imaging expts. using AFM as a probing tool. The use of a large area top electrode between the tip and the sample resulted in the elimination of the electrostatic cantilever-sample interaction with negligible degrdn. of the domain contrast. This method proved to be successful because the cantilever-sample interaction was hardly detected and only the tip-sample interaction was obsd.
- 3Murrell, M. P.; Welland, M. E.; O’Shea, S. J.; Wong, T. M. H.; Barnes, J. R.; McKinnon, A. W.; Heyns, M.; Verhaverbeke, S. Spatially Resolved Electrical Measurements of SiO2 Gate Oxides Using Atomic Force Microscopy. Appl. Phys. Lett. 1993, 62, 786– 788, DOI: 10.1063/1.1085793https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK3sXhtlOgt74%253D&md5=910e0860f198115749f0f34116d72eabSpatially resolved electrical measurements of silica gate oxides using atomic force microscopyMurrell, M. P.; Welland, M. E.; O'Shea, S. J.; Wong, T. M. H.; Barnes, J. R.; McKinnon, A. W.; Heyns, M.; Verhaverbeke, S.Applied Physics Letters (1993), 62 (7), 786-8CODEN: APPLAB; ISSN:0003-6951.By using a modified at. force microscope (AFM) with a conducting cantilever, the authors have investigated the dielec. strength of SiO2 gate oxide films. This has been achieved by spatially resolving the prebreakdown tunneling current flowing between the silicon substrate and tip. During AFM imaging, a voltage ramp was applied to the tip at each image point so as to det. the local threshold voltage required to generate a small tunneling current in the oxide without causing an irreversible elec. breakdown. For an oxide 12-nm thick, this voltage was found to vary by more than a factor of 2.7 over an area of 0.14 μm2, with a max. value of 40.5 V. This suggests that the breakdown strength of conventional metal-oxide-silicon capacitors may not be limited by the intrinsic dielec. strength of the oxide, but by imperfections or nonuniformities in the Si/SiO2 structure. By preventing irreversible oxide breakdown during scanning, the authors can image the dielec. properties of oxide films with a lateral resoln. better than 20 nm.
- 4Nonnenmacher, M.; O’Boyle, M. P.; Wickramasinghe, H. K. Kelvin Probe Force Microscopy. Appl. Phys. Lett. 1991, 58, 2921– 2923, DOI: 10.1063/1.105227There is no corresponding record for this reference.
- 5Polcari, D.; Dauphin-Ducharme, P.; Mauzeroll, J. Scanning Electrochemical Microscopy: A Comprehensive Review of Experimental Parameters from 1989 to 2015. Chem. Rev. 2016, 116, 13234– 13278, DOI: 10.1021/acs.chemrev.6b000675https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xhs1Kjs7nL&md5=df364f985fc28b4a7c6971fbf9bdd5fcScanning Electrochemical Microscopy: A Comprehensive Review of Experimental Parameters from 1989 to 2015Polcari, David; Dauphin-Ducharme, Philippe; Mauzeroll, JanineChemical Reviews (Washington, DC, United States) (2016), 116 (22), 13234-13278CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)A review. Scanning electrochem. microscopy (SECM) is an electroanal. scanning probe technique capable of imaging substrate topog. and local reactivity with high resoln. Since its inception in 1989, it has expanded into a wide variety of research areas including biol., corrosion, energy, kinetics, instrumental development, and surface modification. In the past 25 years, over 1800 peer-reviewed publications have focused on SECM, including several topical reviews. However, these reviews often omit key details, forcing readers to search the literature. In this review, the authors provide a comprehensive summary of the exptl. parameters (e.g., solvents, probes, and mediators) used in all SECM publications since 1989, irresp. of the application. It can be used to rapidly assess exptl. possibilities and make an informed decision about exptl. design. It is a practical guide to SECM.
- 6Williams, C. C.; Wickramasinghe, H. K. Scanning Thermal Profiler. Appl. Phys. Lett. 1986, 49, 1587– 1589, DOI: 10.1063/1.97288There is no corresponding record for this reference.
- 7Zhang, Y.; Zhu, W.; Hui, F.; Lanza, M.; Borca-Tasciuc, T.; Rojo, M. M. A Review on Principles and Applications of Scanning Thermal Microscopy (SThM). Adv. Funct. Mater. 2020, 30, 1900892, DOI: 10.1002/adfm.2019008927https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhslSqurvL&md5=7e7bbbe363ff549020579cec6c13f390A Review on Principles and Applications of Scanning Thermal Microscopy (SThM)Zhang, Yun; Zhu, Wenkai; Hui, Fei; Lanza, Mario; Borca-Tasciuc, Theodorian; Munoz Rojo, MiguelAdvanced Functional Materials (2020), 30 (18), 1900892CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA)A review. As the size of materials, particles, and devices shrinks to nanometer, at., or even quantum scale, it is more challenging to characterize their thermal properties reliably. Scanning thermal microscopy (SThM) is an emerging method to obtain local thermal information by controlling and monitoring probe-sample thermal exchange processes. In this review, key exptl. and theor. components of the SThM system are discussed, including thermal probes and exptl. methods, heat transfer mechanisms, calibration strategies, thermal exchange resistance, and effective heat transfer coeffs. Addnl., recent applications of SThM to novel materials and devices are reviewed, with emphasis on thermoelec., biol., phase change, and 2D materials.
- 8Rubio-Marcos, F.; Del Campo, A.; Marchet, P.; Fernandez, J. F. Ferroelectric Domain Wall Motion Induced by Polarized Light. Nat. Coummn 2015, 6, 6594, DOI: 10.1038/ncomms7594There is no corresponding record for this reference.
- 9Lu, H.; Tan, Y.; McConville, J. P. V.; Ahmadi, Z.; Wang, B.; Conroy, M.; Moore, K.; Bangert, U.; Shield, J. E.; Chen, L.-Q.; Gregg, J. M.; Gruverman, A. Electrical Tunability of Domain Wall Conductivity in LiNbO3 Thin Films. Adv. Mater. 2019, 31, 1902890, DOI: 10.1002/adma.2019028909https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhvFWktb%252FN&md5=3947e7f60a7d6290858ae49c0ffa7c9dElectrical tunability of domain wall conductivity in LiNbO3 thin filmsLu, Haidong; Tan, Yueze; McConville, James P. V.; Ahmadi, Zahra; Wang, Bo; Conroy, Michele; Moore, Kalani; Bangert, Ursel; Shield, Jeffrey E.; Chen, Long-Qing; Gregg, J. Marty; Gruverman, AlexeiAdvanced Materials (Weinheim, Germany) (2019), 31 (48), 1902890CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)Domain wall nanoelectronics is a rapidly evolving field, which explores the diverse electronic properties of the ferroelec. domain walls for application in low-dimensional electronic systems. One of the most prominent features of the ferroelec. domain walls is their elec. cond. Here, using a combination of scanning probe and scanning transmission electron microscopy, the mechanism of the tunable conducting behavior of the domain walls in the sub-micrometer thick films of the technol. important ferroelec. LiNbO3 is explored. It is found that the elec. bias generates stable domains with strongly inclined domain boundaries with the inclination angle reaching 20° with respect to the polar axis. The head-to-head domain boundaries exhibit high conductance, which can be modulated by application of the sub-coercive voltage. Electron microscopy visualization of the elec. written domains and piezoresponse force microscopy imaging of the very same domains reveals that the gradual and reversible transition between the conducting and insulating states of the domain walls results from the elec. induced wall bending near the sample surface. The obsd. modulation of the wall conductance is corroborated by the phase-field modeling. The results open a possibility for exploiting the conducting domain walls as the elec. controllable functional elements in the multilevel logic nanoelectronics devices.
- 10Liu, Z.; Wang, H.; Li, M.; Tao, L.; Paudel, T. R.; Yu, H.; Wang, Y.; Hong, S.; Zhang, M.; Ren, Z.; Xie, Y.; Tsymbal, E. Y.; Chen, J.; Zhang, Z.; Tian, H. In-plane Charged Domain Walls With Memristive Behaviour in a Ferroelectric Film. Nature 2023, 613, 656– 661, DOI: 10.1038/s41586-022-05503-510https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3sXhslKitro%253D&md5=9cb07b6ea2d8a4d107f958269f74f19fIn-plane charged domain walls with memristive behaviour in a ferroelectric filmLiu, Zhongran; Wang, Han; Li, Ming; Tao, Lingling; Paudel, Tula R.; Yu, Hongyang; Wang, Yuxuan; Hong, Siyuan; Zhang, Meng; Ren, Zhaohui; Xie, Yanwu; Tsymbal, Evgeny Y.; Chen, Jingsheng; Zhang, Ze; Tian, HeNature (London, United Kingdom) (2023), 613 (7945), 656-661CODEN: NATUAS; ISSN:1476-4687. (Nature Portfolio)Abstr.: Domain-wall nanoelectronics is considered to be a new paradigm for non-volatile memory and logic technologies in which domain walls, rather than domains, serve as an active element. Esp. interesting are charged domain walls in ferroelec. structures, which have subnanometre thicknesses and exhibit non-trivial electronic and transport properties that are useful for various nanoelectronics applications1-3. The ability to deterministically create and manipulate charged domain walls is essential to realize their functional properties in electronic devices. Here we report a strategy for the controllable creation and manipulation of in-plane charged domain walls in BiFeO3 ferroelec. films a few nanometers thick. By using an in situ biasing technique within a scanning transmission electron microscope, an unconventional layer-by-layer switching mechanism is detected in which ferroelec. domain growth occurs in the direction parallel to an applied elec. field. Based on atomically resolved electron energy-loss spectroscopy, in situ charge mapping by in-line electron holog. and theor. calcns., we show that oxygen vacancies accumulating at the charged domain walls are responsible for the domain-wall stability and motion. Voltage control of the in-plane domain-wall position within a BiFeO3 film gives rise to multiple non-volatile resistance states, thus demonstrating the key functional property of being a memristor a few unit cells thick. These results promote a better understanding of ferroelec. switching behavior and provide a new strategy for creating unit-cell-scale devices.
- 11Crassous, A.; Sluka, T.; Tagantsev, A. K.; Setter, N. Polarization Charge as a Reconfigurable Quasi-Dopant in Ferroelectric Thin Films. Nat. Nanotechnol. 2015, 10, 614– 618, DOI: 10.1038/nnano.2015.11411https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtlOhu73F&md5=673d3749884123320b0cac1c2c7257eePolarization charge as a reconfigurable quasi-dopant in ferroelectric thin filmsCrassous, Arnaud; Sluka, Tomas; Tagantsev, Alexander K.; Setter, NavaNature Nanotechnology (2015), 10 (7), 614-618CODEN: NNAABX; ISSN:1748-3387. (Nature Publishing Group)Impurity elements used as dopants are essential to semiconductor technol. for controlling the concn. of charge carriers. Their location in the semiconductor crystal is detd. during the fabrication process and remains fixed. However, another possibility exists whereby the concn. of charge carriers is modified using polarization charge as a quasi-dopant, which implies the possibility to write, displace, erase and re-create channels having a metallic-type cond. inside a wide-bandgap semiconductor matrix. Polarization-charge doping is achieved in ferroelecs. by the creation of charged domain walls. The intentional creation of stable charged domain walls has so far only been reported in BaTiO3 single crystals, with a process that involves cooling the material through its phase transition under a strong elec. bias, but this is not a viable technol. when real-time reconfigurability is sought in working devices. Here, the authors demonstrate a technique allowing the creation and nanoscale manipulation of charged domain walls and their action as a real-time doping activator in ferroelec. thin films. Stable individual and multiple conductive channels with various lengths from 3 μm to 100 nm were created, erased and recreated in another location, and their high metallic-type cond. was verified. This takes the idea of hardware reconfigurable electronics one step forward.
- 12Gruverman, A.; Wu, D.; Lu, H.; Wang, Y.; Jang, H. W.; Folkman, C. M.; Zhuravlev, M. Ye.; Felker, D.; Rzchowski, M.; Eom, C.-B.; Tsymbal, E. Y. Tunneling Electroresistance Effect in Ferroelectric Tunnel Junctions at the. Nanoscale Nano Lett. 2009, 10, 3539– 3543, DOI: 10.1021/nl901754tThere is no corresponding record for this reference.
- 13Li, T.; Lipatov, A.; Lu, H.; Lee, H.; Lee, J.-W.; Torun, E.; Wirtz, L.; Eom, C.-B.; Iniguez, J.; Sinitskii, A.; Gruverman, A. Optical Control of Polarization in Ferroelectric Heterostructures. Nat. Coummn. 2018, 9, 3344, DOI: 10.1038/s41467-018-05640-4There is no corresponding record for this reference.
- 14Alexe, M.; Hesse, D. Tip-enhanced Photovoltaic Effects in Bismuth Ferrite. Nat. Coummn 2011, 2, 256, DOI: 10.1038/ncomms1261There is no corresponding record for this reference.
- 15Catalan, G.; Seidel, J.; Ramesh, R.; Scott, J. F. Domain Wall Nanoelectronics. Rev. Mod. Phys. 2012, 84, 119, DOI: 10.1103/RevModPhys.84.11915https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XotVOns7g%253D&md5=6b85589cdf76a167de162bf321e0fd81Domain wall nanoelectronicsCatalan, G.; Seidel, J.; Ramesh, R.; Scott, J. F.Reviews of Modern Physics (2012), 84 (1), 119-156CODEN: RMPHAT; ISSN:0034-6861. (American Physical Society)A review. Domains in ferroelecs. were considered to be well understood by the middle of the last century: They were generally rectilinear, and their walls were Ising-like. Their simplicity stood in stark contrast to the more complex Bloch walls or Neel walls in magnets. Only within the past decade and with the introduction of at.-resoln. studies via transmission electron microscopy, electron holog., and at. force microscopy with polarization sensitivity has their real complexity been revealed. Addnl. phenomena appear in recent studies, esp. of magnetoelec. materials, where functional properties inside domain walls are being directly measured. In this paper these studies are reviewed, focusing attention on ferroelecs. and multiferroics but making comparisons where possible with magnetic domains and domain walls. An important part of this review will concern device applications, with the spotlight on a new paradigm of ferroic devices where the domain walls, rather than the domains, are the active element. Here magnetic wall microelectronics is already in full swing, owing largely to the work of Cowburn and of Parkin and their colleagues. These devices exploit the high domain wall mobilities in magnets and their resulting high velocities, which can be supersonic, as shown by Kreines' and co-workers 30 years ago. By comparison, nanoelectronic devices employing ferroelec. domain walls often have slower domain wall speeds, but may exploit their smaller size as well as their different functional properties. These include domain wall cond. (metallic or even superconducting in bulk insulating or semiconducting oxides) and the fact that domain walls can be ferromagnetic while the surrounding domains are not.
- 16Neumayer, S. M.; Saremi, S.; Martin, L. W.; Collins, L.; Tselev, A.; Jesse, S.; Kalinin, S. V.; Balke, N. Piezoresponse Amplitude and Phase Quantified for Electromechanical Characterization. J. Appl. Phys. 2020, 128, 171105, DOI: 10.1063/5.001163116https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXit1Ois7jN&md5=d5651a50c9dc606bd82b37989b6b55a3Piezoresponse amplitude and phase quantified for electromechanical characterizationNeumayer, Sabine M.; Saremi, Sahar; Martin, Lane W.; Collins, Liam; Tselev, Alexander; Jesse, Stephen; Kalinin, Sergei V.; Balke, NinaJournal of Applied Physics (Melville, NY, United States) (2020), 128 (17), 171105CODEN: JAPIAU; ISSN:0021-8979. (American Institute of Physics)Piezoresponse force microscopy (PFM) is a powerful characterization technique to readily image and manipulate the ferroelec. domains. PFM gives an insight into the strength of local piezoelec. coupling and polarization direction through PFM amplitude and phase, resp. Converting measured arbitrary units into units of effective piezoelec. const. remains a challenge, and insufficient methods are often used. While most quantification efforts have been spent on quantifying the PFM amplitude signal, little attention has been given to the PFM phase, which is often arbitrarily adjusted to fit expectations. This is problematic when investigating materials with unknown or neg. sign of the probed effective electrostrictive coeff. or strong frequency dispersion of electromech. responses, because assumptions about the PFM phase cannot be reliably made. The PFM phase can, however, provide important information on the polarization orientation and the sign of the effective electrostrictive coeff. probed by PFM. Most notably, the orientation of the PFM hysteresis loop is detd. by the PFM phase. Moreover, when presenting PFM data as a combined signal, the resulting response can be artificially lowered or asym. if the phase data have not been correctly processed. Here, we explain the PFM amplitude quantification process and demonstrate a path to identify the phase offset required to ext. correct meaning from the PFM phase data. We explore different sources of phase offsets including the exptl. setup, instrumental contributions, and data anal. We discuss the phys. working principles of PFM and develop a strategy to ext. phys. meaning from the PFM amplitude and phase. (c) 2020 American Institute of Physics.
- 17Collins, L.; Liu, Y.; Ovchinnikova, O. S.; Proksch, R. Quantitative Electromechanical Atomic Force Microscopy. ACS Nano 2019, 13, 8055– 8066, DOI: 10.1021/acsnano.9b0288317https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhtlSntbvM&md5=028a3e36f62f344dbe31b87a93f1e0ccQuantitative electromechanical atomic force microscopyCollins, Liam; Liu, Yongtao; Ovchinnikova, Olga S.; Proksch, RogerACS Nano (2019), 13 (7), 8055-8066CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)The ability to probe a material's electromech. functionality on the nanoscale is crit. to applications from energy storage and computing to biol. and medicine. Voltage-modulated at. force microscopy (VM-AFM) has become a mainstay characterization tool for investigating these materials due to its ability to locally probe electromechanically responsive materials with spatial resoln. from micrometers to nanometers. However, with the wide popularity of VM-AFM techniques such as piezoresponse force microscopy and electrochem. strain microscopy there has been a rise in reports of nanoscale electromech. functionality, including hysteresis, in materials that should be incapable of exhibiting piezo- or ferroelectricity. Explanations for the origins of unexpected nanoscale phenomena have included new material properties, surface-mediated polarization changes, and/or spatially resolved behavior that is not present in bulk measurements. At the same time, it is well known that VM-AFM measurements are susceptible to numerous forms of crosstalk, and, despite efforts within the AFM community, a global approach for eliminating this has remained elusive. In this work, the authors develop a method for easily demonstrating the presence of hysteretic (i.e., "false ferroelec.") long-range interactions between the sample and cantilever body. This method should be easy to implement in any VM-AFM measurement. They then go on to demonstrate fully quant. and repeatable nanoelectromech. characterization using an interferometer. These quant. measurements are crit. for a wide range of devices including MEMS actuators and sensors, memristor, energy storage, and memory.
- 18Buragohain, P.; Lu, H.; Richter, C.; Schenk, T.; Kariuki, P.; Glinsek, S.; Funakubo, H.; Íñiguez, J.; Defay, E.; Schroeder, U.; Gruverman, A. Quantification of the Electromechanical Measurements by Piezoresponse Force Microscopy. Adv. Mater. 2022, 34, 2206237, DOI: 10.1002/adma.20220623718https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38XislegtLzO&md5=e0f05919a14c966368c237ba04683301Quantification of the Electromechanical Measurements by Piezoresponse Force MicroscopyBuragohain, Pratyush; Lu, Haidong; Richter, Claudia; Schenk, Tony; Kariuki, Pamenas; Glinsek, Sebastjan; Funakubo, Hiroshi; Iniguez, Jorge; Defay, Emmanuel; Schroeder, Uwe; Gruverman, AlexeiAdvanced Materials (Weinheim, Germany) (2022), 34 (47), 2206237CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)Piezoresponse force microscopy (PFM) is widely used for characterization and exploration of the nanoscale properties of ferroelecs. However, quantification of the PFM signal is challenging due to the convolution of various extrinsic and intrinsic contributions. Although quantification of the PFM amplitude signal has received considerable attention, quantification of the PFM phase signal has not been addressed. A properly calibrated PFM phase signal can provide valuable information on the sign of the local piezoelec. coeff.-an important and nontrivial issue for emerging ferroelecs. In this work, two complementary methodologies to calibrate the PFM phase signal are discussed. The first approach is based on using a std. ref. sample with well-known independently measured piezoelec. coeffs., while the second approach exploits the electrostatic sample-cantilever interactions to det. the parasitic phase offset. Application of these methodologies to studies of the piezoelec. behavior in ferroelec. HfO2-based thin-film capacitors reveals intriguing variations in the sign of the longitudinal piezoelec. coeff., d33,eff. It is shown that the piezoelec. properties of the HfO2-based capacitors are inherently sensitive to their thickness, electrodes, as well as deposition methods, and can exhibit wide variations including a d33,eff sign change within a single device.
- 19Kim, S.; Seol, D.; Lu, X.; Alexe, M.; Kim, Y. Electrostatic-free Piezoresponse Force Microscopy. Sci. Rep. 2017, 7, 41657, DOI: 10.1038/srep4165719https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXitVyisr8%253D&md5=6d18695f2a62e1da85ec7d85eabbf57fElectrostatic-free piezoresponse force microscopyKim, Sungho; Seol, Daehee; Lu, Xiaoli; Alexe, Marin; Kim, YunseokScientific Reports (2017), 7 (), 41657CODEN: SRCEC3; ISSN:2045-2322. (Nature Publishing Group)Contact and non-contact based at. force microscopy (AFM) approaches have been extensively utilized to explore various nanoscale surface properties. In most AFM-based measurements, a concurrent electrostatic effect between the AFM tip/cantilever and sample surface can occur. This electrostatic effect often hinders accurate measurements. Thus, it is very important to quantify as well as remove the impact of the electrostatic effect on AFM-based measurements. In this study, we examine the impact of the electrostatic effect on the electromech. (EM) response in piezoresponse force microscopy as a model AFM mode. We quant. studied the effects of increasing the external elec. field and reducing the spring const. of a cantilever. Further, we explored ways to minimize the electrostatic effect. The results provide broad guidelines for quant. analyzing the EM response as well as, eventually, for obtaining the electrostatic-free EM response. The conclusions can be applied to other AFM-based measurements that are subject to a strong electrostatic effect between the AFM tip/cantilever and sample surface, regardless of contact and non-contact modes.
- 20Balke, N.; Jesse, S.; Yu, P.; Carmichael, B.; Kalinin, S. V.; Tselev, A. Quantification of Surface Displacements and Electromechanical Phenomena via Dynamic Atomic Force Microscopy. Nanotechnology 2016, 27, 425707, DOI: 10.1088/0957-4484/27/42/42570720https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BC2svgs1ahsg%253D%253D&md5=363cd3ac972f07bc0e4aca7fb2790f56Quantification of surface displacements and electromechanical phenomena via dynamic atomic force microscopyBalke Nina; Jesse Stephen; Yu Pu; Ben Carmichael; Kalinin Sergei V; Tselev AlexanderNanotechnology (2016), 27 (42), 425707 ISSN:.Detection of dynamic surface displacements associated with local changes in material strain provides access to a number of phenomena and material properties. Contact resonance-enhanced methods of atomic force microscopy (AFM) have been shown capable of detecting ∼1-3 pm-level surface displacements, an approach used in techniques such as piezoresponse force microscopy, atomic force acoustic microscopy, and ultrasonic force microscopy. Here, based on an analytical model of AFM cantilever vibrations, we demonstrate a guideline to quantify surface displacements with high accuracy by taking into account the cantilever shape at the first resonant contact mode, depending on the tip-sample contact stiffness. The approach has been experimentally verified and further developed for piezoresponse force microscopy (PFM) using well-defined ferroelectric materials. These results open up a way to accurate and precise measurements of surface displacement as well as piezoelectric constants at the pm-scale with nanometer spatial resolution and will allow avoiding erroneous data interpretations and measurement artifacts. This analysis is directly applicable to all cantilever-resonance-based scanning probe microscopy (SPM) techniques.
- 21Killgore, J. P.; Robinsa, L.; Collins, L. Electrostatically-blind Quantitative Piezoresponse Force Microscopy Free of Distributed-Force Artifacts. Nanoscale Adv. 2022, 4, 2036– 2045, DOI: 10.1039/D2NA00046FThere is no corresponding record for this reference.
- 22Sharma, P.; Ryu, S.; Viskadourakis, Z.; Paudel, T. R.; Lee, H.; Panagopoulos, C.; Tsymbal, E. Y.; Eom, C.-B.; Gruverman, A. Electromechanics of Ferroelectric-like Behavior of LaAlO3 Thin Films. Adv. Funct. Mater. 2015, 25, 6538– 6544, DOI: 10.1002/adfm.20150248322https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhsFGktrbO&md5=fb5f17b3201646bffbab4d6ce979b62fElectromechanics of Ferroelectric-Like Behavior of LaAlO3 Thin FilmsSharma, Pankaj; Ryu, Sangwoo; Viskadourakis, Zacharias; Paudel, Tula R.; Lee, Hyungwoo; Panagopoulos, Christos; Tsymbal, Evgeny Y.; Eom, Chang-Beom; Gruverman, AlexeiAdvanced Functional Materials (2015), 25 (41), 6538-6544CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA)Electromech. coupling in complex oxide heterostructures opens new possibilities for the development of a broad range of novel electronic devices with enhanced functionality. In this article, the switchable hysteretic electro-mech. behavior of cryst. epitaxial LaAlO3 (LAO) thin films assocd. with polarization induced by elec. and mech. stimuli is investigated. The field-time-dependent testing of the induced polarization states along with transport measurements and theor. modeling suggests that the ferroelec.-like response of the LAO thin films is mediated by the field-induced ion migration in the bulk of the film. Comparative anal. of the dynamics of polarization reversal under the elec. field and mech. stress applied via a tip of a scanning probe microscope demonstrates that both elec. and mech. stimulus can be used to effectively control polarization at least at the submillisecond timescale. However, the mech. writing is more localized than the elec. one. A combined elec./mech. approach for tuning the phys. properties of oxide hetero-structures may potentially facilitate novel memory and logic devices, in which the data bits are written mech. and read elec.
- 23Balke, N.; Jesse, S.; Li, Q.; Maksymovych, P.; Okatan, M. B.; Strelcov, E.; Tselev, A.; Kalinin, S. V. Current and Surface Charge Modified Hysteresis Loops in Ferroelectric Thin Films. J. Appl. Phys. 2015, 118, 072013, DOI: 10.1063/1.492781123https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtlOgsrnN&md5=9a2eb140c5f65c65692d0080bd1953eeCurrent and surface charge modified hysteresis loops in ferroelectric thin filmsBalke, Nina; Jesse, Stephen; Li, Qian; Maksymovych, Petro; Baris Okatan, M.; Strelcov, Evgheni; Tselev, Alexander; Kalinin, Sergei V.Journal of Applied Physics (Melville, NY, United States) (2015), 118 (7), 072013/1-072013/8CODEN: JAPIAU; ISSN:0021-8979. (American Institute of Physics)Polarization domains in ferroelec. materials and the ability to orient them with an external elec. field lead to the development of a variety of applications from information storage to actuation. The development of piezoresponse force microscopy (PFM) has enabled researchers to investigate ferroelec. domains and ferroelec. domain switching on the nanoscale, which offers a pathway to study structure-function relationships in this important material class. Due to its com. availability and ease of use, PFM has become a widely used research tool. However, measurement artifacts, i.e., alternative signal origins besides the piezoelec. effect are barely discussed or considered. This becomes esp. important for materials with a small piezoelec. coeff. or materials with unknown ferroelec. properties, including non-ferroelec. materials. Here, the role of surface charges and current flow during PFM measurements on classical ferroelecs. are discussed and it will be shown how they alter the PFM hysteresis loop shape. This will help to better address alternative signal origins in PFM-type expts. and offer a pathway to study addnl. phenomena besides ferroelectricity. (c) 2015 American Institute of Physics.
- 24Lu, H.; Glinsek, S.; Buragohain, P.; Defay, E.; Iñiguez, J.; Gruverman, A. Probing Antiferroelectric-Ferroelectric Phase Transitions in PbZrO3 Capacitors by Piezoresponse Force Microscopy. Adv. Funct. Mater. 2020, 30, 2003622, DOI: 10.1002/adfm.202003622There is no corresponding record for this reference.
- 25Buragohain, P.; Erickson, A.; Mimura, T.; Shimizu, T.; Funakubo, H.; Gruverman, A. Effect of Film Microstructure on Domain Nucleation and Intrinsic Switching in Ferroelectric Y:HfO2 Thin Film Capacitors. Adv. Funct. Mater. 2022, 32, 2108876, DOI: 10.1002/adfm.20210887625https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXisF2gsbnE&md5=fe74eab4ae0897caa3cf25ffca3c0f84Effect of Film Microstructure on Domain Nucleation and Intrinsic Switching in Ferroelectric Y:HfO2 Thin Film CapacitorsBuragohain, Pratyush; Erickson, Adam; Mimura, Takanori; Shimizu, Takao; Funakubo, Hiroshi; Gruverman, AlexeiAdvanced Functional Materials (2022), 32 (9), 2108876CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA)One of the general features of ferroelec. systems is a complex nature of polarization reversal, which involves domain nucleation and motion of domain walls. Here, time-resolved nanoscale domain imaging is applied in conjunction with the integral switching current measurements to investigate the mechanism of polarization reversal in yttrium-doped HfO2 (Y:HfO2)-currently one of the most actively studied ferroelec. systems. More specifically, the effect of film microstructure on the nucleation process is investigated by performing a comparative study of the polarization switching behavior in the epitaxial and polycryst. Y:HfO2 thin film capacitors. It is found that although the epitaxial Y:HfO2 capacitors tend to switch slower than their polycryst. counterparts, they exhibit a significantly higher nucleation d. and rate, suggesting that this is a rate-limiting mechanism. In addn., it is obsd. that under the external fields approaching the activation field value, the switching kinetics can be described equally well by the nucleation limited switching and the Kolmogorov-Avrami-Ishibashi models for both types of capacitors. This signifies convergence of two different mechanisms implying that the polarization reversal proceeds via a homogeneous nucleation process unaffected by the film microstructure, which can be considered as approaching the intrinsic switching limit.
- 26Tan, H.; Lyu, J.; Sheng, Y.; Machado, P.; Song, T.; Bhatnagar, A.; Coll, M.; Sanchez, F.; Fontcuberta, J.; Fina, I. A Transversal Approach to Predict Surface Charge Compensation in Piezoelectric Force Microscopy. Appl. Surf. Sci. 2023, 607, 154991, DOI: 10.1016/j.apsusc.2022.15499126https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38XisFSru7jI&md5=c40bcc576173e7e643a18e29ff958d31A transversal approach to predict surface charge compensation in piezoelectric force microscopyTan, Huan; Lyu, Jike; Sheng, Yunwei; Machado, Pamela; Song, Tingfeng; Bhatnagar, Akash; Coll, Mariona; Sanchez, Florencio; Fontcuberta, Josep; Fina, IgnasiApplied Surface Science (2023), 607 (), 154991CODEN: ASUSEE; ISSN:0169-4332. (Elsevier B.V.)Piezoelec. force microscopy (PFM) has demonstrated to be a powerful tool to characterize ferroelec. materials. However, extrinsic effects, most notably, those resulting from surface charges, often mask or mirror genuine piezoelec. response, challenging PFM data understanding. The contribution of surface charges to PFM signal is commonly compensated by using appropriate external bias voltage, which is ad-hoc selected and sample dependent. Here, we det. the compensating voltage in thin films of different ferroelec. materials and we compare with the corresponding I-V characteristics recorded using suitable electrodes. It turns out that the sign and magnitude of the bias voltage required to compensate the surface charges are related to the asymmetry of the I-V characteristics. We propose that this relation results from the fact that the semiconducting properties of the material det. both the I-V dependence, and the sign of charged adsorbates. We show how to make use of this correlation to predict the required compensation voltage of a non-ferroelec. material and we show that spurious piezoelec.-like contributions are largely cancelled. The results provide guidelines to mitigate common extrinsic contributions in PFM imaging.
- 27Labuda, A.; Proksch, R. Quantitative Measurements of Electromechanical Response With a Combined Optical Beam and Interferometric Atomic Force Microscope. Appl. Phys. Lett. 2015, 106, 253103, DOI: 10.1063/1.492221027https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtVyns7%252FM&md5=bc1ec04c0b84304ccb7e89c9e36bbb51Quantitative measurements of electromechanical response with a combined optical beam and interferometric atomic force microscopeLabuda, Aleksander; Proksch, RogerApplied Physics Letters (2015), 106 (25), 253103/1-253103/4CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)An ongoing challenge in at. force microscope (AFM) expts. is the quant. measurement of cantilever motion. The vast majority of AFMs use the optical beam deflection (OBD) method to infer the deflection of the cantilever. The OBD method is easy to implement, has impressive noise performance, and tends to be mech. robust. However, it represents an indirect measurement of the cantilever displacement, since it is fundamentally an angular rather than a displacement measurement. Here, we demonstrate a metrol. AFM that combines an OBD sensor with a laser Doppler vibrometer (LDV) to enable accurate measurements of the cantilever velocity and displacement. The OBD/LDV AFM allows a host of quant. measurements to be performed, including in-situ measurements of cantilever oscillation modes in piezoresponse force microscopy. As an example application, we demonstrate how this instrument can be used for accurate quantification of piezoelec. sensitivity-a longstanding goal in the electromech. community. (c) 2015 American Institute of Physics.
- 28Gruverman, A.; Rodriguez, B. J.; Kingon, A. I.; Nemanich, R. J.; Cross, J. S.; Tsukada, M. Spatial Inhomogeneity of Imprint and Switching Behavior in Ferroelectric Capacitors. Appl. Phys. Lett. 2003, 82, 3071– 3073, DOI: 10.1063/1.157094228https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXjsVSqtrw%253D&md5=fdda9514f3a77ae2eb2029d1d2978681Spatial inhomogeneity of imprint and switching behavior in ferroelectric capacitorsGruverman, A.; Rodriguez, B. J.; Kingon, A. I.; Nemanich, R. J.; Cross, J. S.; Tsukada, M.Applied Physics Letters (2003), 82 (18), 3071-3073CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)Piezoresponse force microscopy has been used to perform nanoscale characterization of the spatial variations in the imprint and switching behavior of (111)-oriented Pb(Zr,Ti)O3-based capacitors on Pt electrodes. Mapping of polarization distribution in the poled capacitors as well as local d33-V loop measurements revealed a significant difference in imprint and switching behavior between the peripheral and inner parts of the capacitors. It has been found that the inner regions of the capacitors are neg. imprinted (with the preferential direction of the normal component of polarization upward) and tend to switch back after application of the pos. poling voltage. On the other hand, switchable regions at the edge of the integrated capacitors generally exhibit more sym. hysteresis behavior. Application of an ac switching voltage, contrary to what was expected, resulted in an increase of the neg. imprinted regions. The obsd. effect has been explained by incomplete or asym. switching due to the mech. stress conditions existing in the central parts of the capacitors.
- 29Christman, J. A.; Kim, S.-H.; Maiwa, H.; Maria, J.-P.; Rodriguez, B. J.; Kingon, A. I.; Nemanich, R. J. Spatial Variation of Ferroelectric Properties in Pb(Zr0.3,Ti0.7)O3 Thin Films Studied by Atomic Force Microscopy. J. Appl. Phys. 2000, 87, 8031– 8034, DOI: 10.1063/1.373492There is no corresponding record for this reference.
- 30Gruverman, A.; Auciello, O.; Tokumoto, H. Nanoscale Investigation of Fatigue Effects in Pb(Zr,Ti)O3 Films. Appl. Phys. Lett. 1996, 69, 3191– 3193, DOI: 10.1063/1.117957There is no corresponding record for this reference.
- 31Zhou, Y.; Chan, H. K.; Lam, C. H.; Shin, F. G. Mechanisms of Imprint Effect on Ferroelectric Thin Films. J. Appl. Phys. 2005, 98, 024111, DOI: 10.1063/1.198407531https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXntV2hsLk%253D&md5=fa811a82cb7e8c978f7cf98508aea009Mechanisms of imprint effect on ferroelectric thin filmsZhou, Y.; Chan, H. K.; Lam, C. H.; Shin, F. G.Journal of Applied Physics (2005), 98 (2), 024111/1-024111/9CODEN: JAPIAU; ISSN:0021-8979. (American Institute of Physics)We have developed a single/double layer model to explain horizontal shifting of measured D-E hysteresis loops (imprint) for ferroelec. thin films. Such phenomenon can be explained by considering three mechanisms or their multiple effects: (1) stress induced by film/electrode lattice mismatch or clamping, (2) domain pinning induced by, e.g., oxygen vacancies, or (3) degrdn. of ferroelec. properties in film/electrode surface layers. First, it is found that hysteresis loops under the influence of stress exhibit large horizontal shifts with magnitudes comparable to those obsd. in expts. Second, a pseudo-non-switching layer with a large coercive field is assumed to be present at the film/electrode interface in an otherwise homogeneous ferroelec. thin film, and in this case our simulation also shows a large imprint effect. Third, it is also found that time-dependent space-charge-limited conduction is likely to be one origin for the occurrence of imprint.
- 32Damodaran, A. R.; Breckenfeld, E.; Chen, Z.; Lee, S.; Martin, L. W. Enhancement of Ferroelectric Curie Temperature in BaTiO3 Films via Strain-Induced Defect Dipole Alignment. Adv. Mater. 2014, 26, 6341– 6347, DOI: 10.1002/adma.20140025432https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXht1Kksb%252FI&md5=9c5d52fa268d034a7134a29212a81f62Enhancement of Ferroelectric Curie Temperature in BaTiO3 Films via Strain-Induced Defect Dipole AlignmentDamodaran, Anoop R.; Breckenfeld, Eric; Chen, Zuhuang; Lee, Sungki; Martin, Lane W.Advanced Materials (Weinheim, Germany) (2014), 26 (36), 6341-6347CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)The coupling between epitaxial strain and defect dipoles that form due to the pulsed-laser deposition growth process to controllably tune the TC of BaTiO3 to over 800° C is explored. Purely epitaxial strain-based approaches for TC enhancement are limited by the magnitude of strain that can be applied, the thicknesses that can be achieved before film relaxation, and a lack of strain tunability. It is shown in this work that epitaxial strain can be used to control the ordering of defect dipoles inducing addnl. out-of-plane strains and enabling controlled enhancement of TC without the need to change substrates. This is esp. exciting since neither the polarization nor the leakage properties are diminished thereby enabling the measurement of well-defined ferroelec. hysteresis loops to at least 500° C. It should be noted that even in bulk crystals, aging can give rise to enhanced TC but the exact mechanism was not well understood nor is it known how to deterministically control the magnitude and nature of these effects. This work provides a new application to complex oxide ferroelecs. and represents an exciting discovery with implications for utilization of these materials in high-temp. applications.
- 33Buragohain, P.; Erickson, A.; Kariuki, P.; Mittmann, T.; Richter, C.; Lomenzo, P. D.; Lu, H.; Schenk, T.; Mikolajick, T.; Schroeder, U.; Gruverman, A. Fluid Imprint and Inertial Switching in Ferroelectric La:HfO2 Capacitors. ACS Appl. Mater. Interfaces 2019, 11, 35115– 35121, DOI: 10.1021/acsami.9b1114633https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhs1Kks7vF&md5=fd593338a0658d401b5bf1a813595878Fluid imprint and inertial switching in ferroelectric La:HfO2 capacitorsBuragohain, Pratyush; Erickson, Adam; Kariuki, Pamenas; Mittmann, Terence; Richter, Claudia; Lomenzo, Patrick D.; Lu, Haidong; Schenk, Tony; Mikolajick, Thomas; Schroeder, Uwe; Gruverman, AlexeiACS Applied Materials & Interfaces (2019), 11 (38), 35115-35121CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)Ferroelec. (FE) HfO2-based thin films, which are considered as one of the most promising material systems for memory device applications, exhibit an adverse tendency for strong imprint. Manifestation of imprint is a shift of the polarization-voltage (P-V) loops along the voltage axis due to the development of an internal elec. bias, which can lead to the failure of the writing and retention functions. Here, to gain insight into the mechanism of the imprint effect in La-doped HfO2 (La:HfO2) capacitors, we combine the pulse switching technique with high-resoln. domain imaging by means of piezoresponse force microscopy. This approach allows us to establish a correlation between the macroscopic switching characteristics and domain time-voltage-dependent behavior. It has been shown that the La:HfO2 capacitors exhibit a much more pronounced imprint compared to Pb(Zr,Ti)O3-based FE capacitors. Also, in addn. to conventional imprint, which evolves with time in the poled capacitors, an easily changeable imprint, termed as "fluid imprint", with a strong dependence on the switching prehistory and measurement conditions, has been obsd. Visualization of the domain structure reveals a specific signature of fluid imprint-continuous switching of polarization in the same direction as the previously applied field that continues a long time after the field was turned off. This effect, termed as "inertial switching", is attributed to charge injection and subsequent trapping at defect sites at the film-electrode interface.
- 34Alcala, R.; Materano, M.; Lomenzo, P. D.; Vishnumurthy, P.; Hamouda, W.; Dubourdieu, C.; Kersch, A.; Barrett, N.; Mikolajick, T.; Schroede, U. The Electrode-Ferroelectric Interface as the Primary Constraint on Endurance and Retention in HZO-Based Ferroelectric Capacitors. Adv. Funct. Mater. 2023, 23, 2303261, DOI: 10.1002/adfm.202303261There is no corresponding record for this reference.
- 35Lee, H.; Kim, T. H.; Patzner, J. J.; Lu, H.; Lee, J. W.; Zhou, H.; Chang, W.; Mahanthappa, M. K.; Tsymbal, E. Y.; Gruverman, A.; Eom, C. B. Imprint Control of BaTiO3 Thin Films via Chemically Induced Surface Polarization Pinning. Nano Lett. 2016, 16, 2400– 2406, DOI: 10.1021/acs.nanolett.5b0518835https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XivFOgu70%253D&md5=3b43a8ba1fd3cc504da391b648244a64Imprint Control of BaTiO3 Thin Films via Chemically Induced Surface Polarization PinningLee, Hyungwoo; Kim, Tae Heon; Patzner, Jacob J.; Lu, Haidong; Lee, Jung-Woo; Zhou, Hua; Chang, Wansoo; Mahanthappa, Mahesh K.; Tsymbal, Evgeny Y.; Gruverman, Alexei; Eom, Chang-BeomNano Letters (2016), 16 (4), 2400-2406CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)Surface-adsorbed polar mols. can significantly alter the ferroelec. properties of oxide thin films. Thus, fundamental understanding and controlling the effect of surface adsorbates are crucial for the implementation of ferroelec. thin film devices, such as ferroelec. tunnel junctions. Herein, we report an imprint control of BaTiO3 (BTO) thin films by chem. induced surface polarization pinning in the top few at. layers of the water-exposed BTO films. Our studies based on synchrotron X-ray scattering and coherent Bragg rod anal. demonstrate that the chem. induced surface polarization is not switchable but reduces the polarization imprint and improves the bistability of ferroelec. phase in BTO tunnel junctions. We conclude that the chem. treatment of ferroelec. thin films with polar mols. may serve as a simple yet powerful strategy to enhance functional properties of ferroelec. tunnel junctions for their practical applications.
- 36Tan, H.; Castro, G.; Lyu, J.; Loza-Alvarez, P.; Sanchez, F.; Fontcuberta, J.; Fina, I. Control of up-to-down/down-to-up Light-induced Ferroelectric Polarization Reversal Mater. Horiz. 2022, 9, 2345– 2352, DOI: 10.1039/D2MH00644HThere is no corresponding record for this reference.
- 37Long, X.; Tan, H.; Sánchez, F.; Fina, I.; Fontcuberta, J. Non-Volatile Optical Switch of Resistance in Photoferroelectric Tunnel Junctions. Nat. Coummn 2021, 12, 382, DOI: 10.1038/s41467-020-20660-9There is no corresponding record for this reference.
- 38Alikin, D.; Abramov, A.; Turygin, A.; Ievlev, A.; Pryakhina, V.; Karpinsky, D.; Hu, Q.; Jin, L.; Shur, V.; Tselev, A.; Kholkin, A. Exploring Charged Defects in Ferroelectrics by the Switching Spectroscopy Piezoresponse Force Microscopy. Small Methods 2022, 6, 2101289, DOI: 10.1002/smtd.202101289There is no corresponding record for this reference.
- 39Balke, N.; Maksymovych, P.; Jesse, S.; Herklotz, A.; Tselev, A.; Eom, C.-B.; Kravchenko, I. I.; Yu, P.; Kalinin, S. V. Differentiating Ferroelectric and Nonferroelectric Electromechanical Effects With Scanning Probe Microscopy. ACS Nano 2015, 9, 6484– 6492, DOI: 10.1021/acsnano.5b0222739https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXpsFalu74%253D&md5=81a7f07498af83064bae16808dcdda74Differentiating Ferroelectric and Nonferroelectric Electromechanical Effects with Scanning Probe MicroscopyBalke, Nina; Maksymovych, Petro; Jesse, Stephen; Herklotz, Andreas; Tselev, Alexander; Eom, Chang-Beom; Kravchenko, Ivan I.; Yu, Pu; Kalinin, Sergei V.ACS Nano (2015), 9 (6), 6484-6492CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)Ferroelectricity in functional materials remains one of the most fascinating areas of modern science in the past several decades. In the last several years, the rapid development of piezoresponse force microscopy (PFM) and spectroscopy revealed electromech. hysteresis loops and bias-induced remnant polar states in a broad variety of materials including many inorg. oxides, polymers, and biosystems. In many cases, this behavior was interpreted as the ample evidence for ferroelec. nature of the system. Here, the authors systematically analyze PFM responses on ferroelec. and nonferroelec. materials and demonstrate that mechanisms unrelated to ferroelectricity can induce ferroelec.-like characteristics through charge injection and electrostatic forces on the tip. The authors will focus on similarities and differences in various PFM measurement characteristics to provide an exptl. guideline to differentiate between ferroelec. material properties and charge injection. In the end, the authors apply the developed measurement protocols to an unknown ferroelec. material.
- 40Buragohain, P.; Richter, C.; Schenk, T.; Lu, H.; Mikolajick, T.; Schroeder, U.; Gruverman, A. Nanoscopic Studies of Domain Structure Dynamics in Ferroelectric La:HfO2 Capacitors. Appl. Phys. Lett. 2018, 112, 222901, DOI: 10.1063/1.503056240https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhtVGit73K&md5=078ffc0f4619f8677118a6adef888689Nanoscopic studies of domain structure dynamics in ferroelectric La:HfO2 capacitorsBuragohain, P.; Richter, C.; Schenk, T.; Lu, H.; Mikolajick, T.; Schroeder, U.; Gruverman, A.Applied Physics Letters (2018), 112 (22), 222901/1-222901/5CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)Visualization of domain structure evolution under an elec. bias has been carried out in ferroelec. La:HfO2 capacitors by a combination of Piezoresponse Force Microscopy (PFM) and pulse switching techniques to study the nanoscopic mechanism of polarization reversal and the wake-up process. It has been directly shown that the main mechanism behind the transformation of the polarization hysteretic behavior and an increase in the remanent polarization value upon the a.c. cycling is elec. induced domain de-pinning. PFM imaging and local spectroscopy revealed asym. switching in the La:HfO2 capacitors due to a significant imprint likely caused by the different boundary conditions at the top and bottom interfaces. Domain switching kinetics can be well-described by the nucleation limited switching model characterized by a broad distribution of the local switching times. It has been found that the domain velocity varies significantly throughout the switching process indicating strong interaction with structural defects. (c) 2018 American Institute of Physics.
- 41Wu, D.; Vrejoiu, I.; Alexe, M.; Gruverman, A. Anisotropy of Domain Growth in Epitaxial Ferroelectric Capacitors. Appl. Phys. Lett. 2010, 96, 112903, DOI: 10.1063/1.3366724There is no corresponding record for this reference.
- 42Gruverman, A.; Rodriguez, B. J.; Kingon, A. I.; Nemanich, R. J.; Tagantsev, A. K.; Cross, J. S.; Tsukada, M. Mechanical Stress Effect on Imprint Behavior of Integrated Ferroelectric Capacitors. Appl. Phys. Lett. 2003, 83, 728– 730, DOI: 10.1063/1.159383042https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXlvVWlsLs%253D&md5=e4a85ba7a342a7490c1ed830d1654059Mechanical stress effect on imprint behavior of integrated ferroelectric capacitorsGruverman, A.; Rodriguez, B. J.; Kingon, A. I.; Nemanich, R. J.; Tagantsev, A. K.; Cross, J. S.; Tsukada, M.Applied Physics Letters (2003), 83 (4), 728-730CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)Stress-induced changes in the imprint and switching behavior of (111)-oriented Pb(Zr,Ti)O3 (PZT)-based capacitors have been studied using piezoresponse force microscopy. Visualization of polarization distribution and d33-loop measurements in individual 1×1.5-μm2 capacitors before and after stress application, generated by substrate bending, provided direct exptl. evidence of stress-induced switching. Mech. stress caused elastic switching in capacitors with the direction of the resulting polarization detd. by the sign of the applied stress. In addn., stress application turned capacitors into a heavily imprinted state characterized by strongly shifted hysteresis loops and almost complete backswitching after application of the poling voltage. It is suggested that substrate bending generated a strain gradient in the PZT layer, which produced asym. lattice distortion with preferential polarization direction and triggered polarization switching due to the flexoelec. effect.
- 43Miao, P.; Zhao, Y.; Luo, N.; Zhao, D.; Chen, A.; Sun, Z.; Guo, M.; Zhu, M.; Zhang, H.; Li, Q. Ferroelectricity and Self-Polarization in Ultrathin Relaxor Ferroelectric Films. Sci. Rep. 2016, 6, 19965, DOI: 10.1038/srep1996543https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhslOgsb4%253D&md5=3db969d2500e70216afd7945eac6601bFerroelectricity and Self-Polarization in Ultrathin Relaxor Ferroelectric FilmsMiao, Peixian; Zhao, Yonggang; Luo, Nengneng; Zhao, Diyang; Chen, Aitian; Sun, Zhong; Guo, Meiqi; Zhu, Meihong; Zhang, Huiyun; Li, QiangScientific Reports (2016), 6 (), 19965CODEN: SRCEC3; ISSN:2045-2322. (Nature Publishing Group)We report ferroelectricity and self-polarization in the (001) oriented ultrathin relaxor ferroelec. PMN-PT films grown on Nb-SrTiO3, SrRuO3 and La0.7Sr0.3MnO3, resp. Resistance-voltage measurements and AC impedance anal. suggest that at high temps. Schottky depletion width in a 4 nm thick PMN-PT film deposited on Nb-SrTiO3 is smaller than the film thickness. We propose that Schottky interfacial dipoles make the dipoles of the nanometer-sized polar nanoregions (PNRs) in PMN-PT films grown on Nb-SrTiO3 point downward at high temps. and lead to the self-polarization at room temp. with the assistance of in-plane compressive strain. This work sheds light on the understanding of epitaxial strain effects on relaxor ferroelec. films and self-polarization mechanism.
- 44Ma, J.; Zhu, Y.; Tang, Y.; Han, M.; Wang, Y.; Zhang, N.; Zou, M.; Feng, Y.; Gengac, W.; Maa, X. Modulation of Charged a1/a2 Domains and Piezoresponses of Tensile Strained PbTiO3 Films by the Cooling Rate. RSC Adv. 2019, 9, 13981– 13990, DOI: 10.1039/C9RA02485A44https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXovFelsbs%253D&md5=a8e6bc029f3748045a2881094bd95204Modulation of charged a1/a2 domains and piezoresponses of tensile strained PbTiO3 films by the cooling rateMa, Jinyuan; Zhu, Yinlian; Tang, Yunlong; Han, Mengjiao; Wang, Yujia; Zhang, Ningbin; Zou, Minjie; Feng, Yanpeng; Geng, Wanrong; Ma, XiuliangRSC Advances (2019), 9 (25), 13981-13990CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)Controlling domain width, orientation, and patterns in oxide ferroelecs. are not only important for fundamental research but also for potential electronic application. Here, a series of PbTiO3 thin films under various cooling rates were deposited on (110)-oriented NdScO3 substrates by pulsed laser deposition and investigated by using conventional transmission electron microscopy, Cs-cor. scanning TEM and piezoresponse force microscopy. Contrast anal. and electron diffraction revealed that PbTiO3 films are a1/a2 domain patterns under large tensile strains with different cooling rates. The a1/a2 domains distribute periodically and the domain width increases with decrease in the cooling rates. Upon increasing the cooling rate, the domain d. increases and the domain configurations become complicated. There are special square frame-like domain patterns with charged domain walls found in the PTO films with the fast cooling rate. PFM measurement shows that the PTO films with high cooling rate exhibit enhanced piezoresponse behavior which is ascribed to the high d. domain/domain walls and special domain configurations. The formation mechanism of the different domain configurations is discussed in terms of the effect of cooling rates, defects and thermal kinetics. These results are expected to provide useful information for domain/domain wall control and thus facilitate further modulation of the properties for potential applications.
- 45Kos, A. B.; Killgore, J. P.; Hurley, D. C. SPRITE: A Modern Approach to Scanning Probe Contact Resonance Imaging Meas. Sci. Technol. 2014, 25, 025405, DOI: 10.1088/0957-0233/25/2/025405There is no corresponding record for this reference.
- 46Jesse, S.; Kalinin, S. V.; Proksch, R.; Baddorf, A. P.; Rodriguez, B. J. The Band Excitation Method in Scanning Probe Microscopy for Rapid Mapping of Energy Dissipation on the. Nanoscale Nanotechnology 2007, 18, 435503, DOI: 10.1088/0957-4484/18/43/435503There is no corresponding record for this reference.
- 47Rodriguez, B. J.; Callahan, C.; Kalinin, S. V.; Proksch, R. Dual-Frequency Fesonance-Tracking Atomic Force Microscopy Nanotechnology 2007, 18 475504. DOI: 10.1088/0957-4484/18/47/475504There is no corresponding record for this reference.
- 48Zhang, Q.; Huang, H. H.; Sando, D.; Summers, M.; Munroe, P.; Standarda, O.; Valanoor, N. Mixed-Phase Bismuth Ferrite Thin Films by Chemical Solution Deposition. J. Mater. Chem. C 2018, 6, 2882– 2888, DOI: 10.1039/C7TC05841A48https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXivFSntLY%253D&md5=3c4d5948365604664e82be5abb09318fMixed-phase bismuth ferrite thin films by chemical solution depositionZhang, Qi; Huang, Hsin-Hui; Sando, Daniel; Summers, Max; Munroe, Paul; Standard, Owen; Valanoor, NagarajanJournal of Materials Chemistry C: Materials for Optical and Electronic Devices (2018), 6 (11), 2882-2888CODEN: JMCCCX; ISSN:2050-7534. (Royal Society of Chemistry)Epitaxial mixed-phase bismuth ferrite (BiFeO3, BFO) thin films were successfully synthesized on (001) lanthanum aluminate (LaAlO3, LAO) substrates by a chem. soln. deposition (CSD) technique. X-ray diffraction measurements confirm the co-existence of a completely relaxed rhombohedral-like (R') phase and a strained tetragonal-like (T') phase. Atomic resoln. scanning transmission electron microscopy (STEM) measurements reveal that the T' and R' phases in our CSD derived BFO/LAO films are mixed homogeneously at the nanoscale. This is in stark contrast to the typical phys. vapor deposition-derived mixed-phase BFO thin films, which show R' phase striations embedded in a T' phase matrix. This phenomenon is attributed to the specific deposition-nucleation-crystn.-relaxation pathway characteristic of the CSD route. This homogenously mixed-phase still demonstrates the well-known morphotropic phase boundary effect, i.e. superior electromech. properties compared to either the pure T' phase or R' phase constituents themselves. Moreover, the max. piezoelec. coeff. measured by using nanoscale top electrodes shows surprising insensitivity to the clamping effect from the substrate, thereby offering considerable promise in thin film applications.
- 49Zhou, J.; Sando, D.; Cheng, X.; Ma, Z.; Valanoor, N.; Zhang, Q. Tuning Phase Fractions and Leakage Properties of Chemical Solution Deposition-Derived Mixed-Phase BiFeO3 Thin Films. ACS Appl. Electron. Mater. 2020, 2, 4099– 4110, DOI: 10.1021/acsaelm.0c0089149https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXisFSqu7%252FP&md5=acbe6731f29897fbced50fe5d0cdeb64Tuning Phase Fractions and Leakage Properties of Chemical Solution Deposition-Derived Mixed-Phase BiFeO3 Thin FilmsZhou, Jinling; Sando, Daniel; Cheng, Xuan; Ma, Zhijun; Valanoor, Nagarajan; Zhang, QiACS Applied Electronic Materials (2020), 2 (12), 4099-4110CODEN: AAEMBP; ISSN:2637-6113. (American Chemical Society)Phase-pure epitaxial bismuth ferrite (BiFeO3, BFO) thin films with a homogeneous mixed-phase structure were synthesized on (001)-oriented lanthanum aluminate (LaAlO3, LAO) substrates using chem. soln. deposition. The phase development of the BFO thin film and its leakage current characteristics have been systematically investigated as a function of thickness (no. of spin-coated layers) and the heat treatment process (heating temp. and dwell time). The results show that the tetragonal-like (T') phase fraction changes dramatically from 35% (45 nm thick single layer) to 10% (250 nm thick four-layer films). In a two-layer film (80 nm) configuration, the T'-phase fraction was further tuned. When annealing at 640°C for 30 min, this mixed-phase BFO film, despite its high T'-phase fraction (28%), shows the lowest leakage current (<0.1 A/cm2 at <500 kV/cm), comparable to 200 nm pulsed laser deposition-grown pure R-BFO thin films. In contrast to the obsd. bulk-limited Ohmic or space-charge-limited-conduction (SCLC)-predominant mechanism in pure R'-phase and low T'-phase fraction BFO thin films, the high T'-phase fraction (~ 28%) mixed-phase BFO film displays an interface-limited Schottky emission to an SCLC mechanism transition with increasing elec. field.
- 50Yang, S. Y.; Martin, L. W.; Byrnes, S. J.; Conry, T. E.; Basu, S. R.; Paran, D.; Reichertz, L.; Ihlefeld, J.; Adamo, C.; Melville, A.; Chu, Y.-H.; Yang, C.-H.; Musfeldt, J. L.; Schlom, D. G.; Ager III, J. W.; Ramesh, R. Photovoltaic Effects in BiFeO3. Appl. Phys. Lett. 2009, 95, 062909, DOI: 10.1063/1.320469550https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXhtVSiurbJ&md5=e2e200bd78e874bbb266c55f057727a2Photovoltaic effects in BiFeO3Yang, S. Y.; Martin, L. W.; Byrnes, S. J.; Conry, T. E.; Basu, S. R.; Paran, D.; Reichertz, L.; Ihlefeld, J.; Adamo, C.; Melville, A.; Chu, Y.-H.; Yang, C.-H.; Musfeldt, J. L.; Schlom, D. G.; Ager, J. W., III; Ramesh, R.Applied Physics Letters (2009), 95 (6), 062909/1-062909/3CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)We report a photovoltaic effect in ferroelec. BiFeO3 thin films. The all-oxide heterostructures with SrRuO3 bottom and Sn doped In oxide top electrodes are characterized by open-circuit voltages ∼0.8-0.9 V and external quantum efficiencies up to ∼10% when illuminated with the appropriate light. Efficiencies are at least an order of magnitude larger than the max. efficiency under sunlight (AM 1.5) thus far reported for ferroelec.-based devices. The dependence of the measured open-circuit voltage on film thickness suggests contributions to the large open-circuit voltage from both the ferroelec. polarization and band offsets at the BiFeO3/Sn doped In oxide interface. (c) 2009 American Institute of Physics.
- 51Jesse, S.; Lee, H. N.; Kalinin, S. V. Quantitative Mapping of Switching Behavior in Piezoresponse Force Microscopy Rev. Sci. 2006, 77, 073702, DOI: 10.1063/1.2214699There is no corresponding record for this reference.
- 52Augurio, A.; Alvarez-Fernandez, A.; Panchal, V.; Pittenger, B.; Wolf, P. De; Guldin, S.; Briscoe, J. Controlled Porosity in Ferroelectric BaTiO3 Photoanodes. ACS Appl. Mater. Interfaces 2022, 14, 13147– 13157, DOI: 10.1021/acsami.1c1741952https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38XmsFeis78%253D&md5=ec550411426ee17de9ae54cb224cd24aControlled Porosity in Ferroelectric BaTiO3 PhotoanodesAugurio, Adriana; Alvarez-Fernandez, Alberto; Panchal, Vishal; Pittenger, Bede; De Wolf, Peter; Guldin, Stefan; Briscoe, JoeACS Applied Materials & Interfaces (2022), 14 (11), 13147-13157CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)The use of ferroelec. polarization to promote electron-hole sepn. has emerged as a promising strategy to improve photocatalytic activity. Although ferroelec. thin films with planar geometry have been largely studied, nanostructured and porous ferroelec. thin films have not been commonly used in photo-electrocatalysis. The inclusion of porosity in ferroelec. thin films would enhance the surface area and reactivity, leading to a potential improvement of the photoelectrochem. (PEC) performance. Herein, the prepn. of porous barium titanate (pBTO) thin films by a soft template-assisted sol-gel method is reported, and the control of porosity using different org./inorg. ratios is verified by the combination of SEM and ellipsometry techniques. Using piezoresponse force microscopy, the switching of ferroelec. domains in pBTO thin films is obsd., confirming that the ferroelec. polarization is still retained in the porous structures. In addn., the presence of porosity in pBTO thin films leads to a clear improvement of the PEC response. By electrochem. poling, we also demonstrated the tuning of the PEC performance of pBTO thin films via ferroelec. polarization. Our work offers a simple and low-cost approach to control the morphol. optimization of ferroelec. thin films, which could open up the development of materials with great potential for PEC applications.
- 53Dwij, V.; De, B. K.; Rana, S.; Kunwar, H. S.; Yadav, S.; Sahu, S. R.; Venkatesh, R.; Lalla, N. P.; Phase, D. M.; Shukla, D. K.; Sathe, V. G. Optical Control of Domain Configuration Through Light Polarization in Ferroelectric BaTiO3. Phys. Rev. B 2022, 105, 134103, DOI: 10.1103/PhysRevB.105.13410353https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38Xhtlags7jK&md5=f455c40b08e9748bc7045606f4acf6b1Optical control of domain configuration through light polarization in ferroelectric BaTiO3Dwij, Vivek; De, Binoy Krishna; Rana, Sumesh; Kunwar, Hemant Singh; Yadav, Satish; Sahu, Shikha Rani; Venkatesh, R.; Lalla, N. P.; Phase, D. M.; Shukla, D. K.; Sathe, V. G.Physical Review B (2022), 105 (13), 134103CODEN: PRBHB7; ISSN:2469-9969. (American Physical Society)Optical control and switching of domain configuration are intriguing to overcome the sluggish time response, hysteresis, and Joule heating losses present in conventional methods where resistive contacts are involved. The effective optical control of the domain configuration has remained challenging and far from fully understood. It has been reported that light polarization can be used to control the domain configuration in BaTiO3, however, without much focus on origin of its mechanism. By combining the exptl. techniques that are sensitive to the local and av. crystal structure and to elec. polarization and electronic structure, we detect and demonstrate the optically guided variations in the domain configurations of BaTiO3 and show that the strain field generated through the bulk photovoltaic effect plays a key role in domain reconfiguration. Complete mechanism of reversible domain control via light polarization is discussed.
- 54Dong, G.; Li, S.; Yao, M.; Zhou, Z.; Zhang, Y.-Q.; Han, X.; Luo, Z.; Yao, J.; Peng, B.; Hu, Z.; Huang, H.; Jia, T.; Li, J.; Ren, W.; Ye, Z.-G.; Ding, X.; Sun, J.; Nan, C.-W.; Chen, L.-Q.; Li, J.; Liu, M. Super-Elastic Ferroelectric Single-Crystal Membrane With Continuous Electric Dipole Rotation. Science 2019, 366, 475– 479, DOI: 10.1126/science.aay722154https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXitVemtrnO&md5=7e5107e8db091f201d570a693bedfa6eSuper-elastic ferroelectric single-crystal membrane with continuous electric dipole rotationDong, Guohua; Li, Suzhi; Yao, Mouteng; Zhou, Ziyao; Zhang, Yong-Qiang; Han, Xu; Luo, Zhenlin; Yao, Junxiang; Peng, Bin; Hu, Zhongqiang; Huang, Houbing; Jia, Tingting; Li, Jiangyu; Ren, Wei; Ye, Zuo-Guang; Ding, Xiangdong; Sun, Jun; Nan, Ce-Wen; Chen, Long-Qing; Li, Ju; Liu, MingScience (Washington, DC, United States) (2019), 366 (6464), 475-479CODEN: SCIEAS; ISSN:1095-9203. (American Association for the Advancement of Science)High-quality ferroelec. materials, which polarize in response to an elec. field, are usually oxides that crack when bent. Dong et al. found that high-quality membranes of barium titanate are surprisingly flexible and super-elastic. These films accommodate large strains through dynamic evolution of nanodomains during deformation. This discovery is important for developing more robust flexible devices.
- 55Takada, K.; Takarae, S.; Shimamoto, K.; Fujimura, N.; Yoshimura, T. Time-Dependent Imprint in Hf0.5Zr0.5O2 Ferroelectric Thin Films. Adv. Electron. Mater. 2021, 7, 2100151, DOI: 10.1002/aelm.20210015155https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXhsVKls7fF&md5=2bfb27003a05554424174911121009afTime-Dependent Imprint in Hf0.5Zr0.5O2 Ferroelectric Thin FilmsTakada, Kenshi; Takarae, Shuya; Shimamoto, Kento; Fujimura, Norifumi; Yoshimura, TakeshiAdvanced Electronic Materials (2021), 7 (8), 2100151CODEN: AEMDBW; ISSN:2199-160X. (Wiley-VCH Verlag GmbH & Co. KGaA)The discovery of the HfO2-based ferroelec. films has opened new opportunities for using this silicon-compatible ferroelec. material to realize low-power logic circuits and high-d. non-volatile memories. The functional performances of ferroelecs. are intimately related to their dynamic response to external stimuli, such as elec. fields at finite temps. In the case of HfO2-based films, the time-dependent imprint and wake-up effect, which distinguish them from conventional ferroelecs., play important roles in understanding the remaining reliability issues, such as insufficient endurance. In this study, the time-dependent imprint process is carefully investigated using Hf0.5Zr0.5O2 (HZO) films with different ferroelec. properties and defect d. The amt. of redistributed charge, which causes imprint during polarization retention, is affected by the remanent polarization of the ferroelec. layer, suggesting that the depolarization field corresponding to the remanent polarization generates and works as a driving force of charge redistribution. The time-dependent measurement of the imprint distinguishes the origins of charge redistribution processes, which have different time consts. In addn., the correlation between the amt. of redistributed charge and the dielec. relaxation of the HZO films is discussed. Correlations are identified between the redistributed charge and the dielec. relaxation, indicating that the mobile charge contributes to the time-dependent imprint.
- 56Harrington, S. A.; Zhai, J.; Denev, S.; Gopalan, V.; Wang, H.; Bi, Z.; Redfern, S. A. T.; Baek, S.-H.; Bark, C. W.; Eom, C.-B.; Jia, Q.; Vickers, M. E.; MacManus-Driscoll, J. L. Thick Lead-Free Ferroelectric Films With High Curie Temperatures Through Nanocomposite-Induced. Strain Nat. Nanotechnol. 2011, 6, 491, DOI: 10.1038/nnano.2011.9856https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXotlCktL8%253D&md5=71b6c92a8b13627c3abc7267bd73cf72Thick lead-free ferroelectric films with high Curie temperatures through nanocomposite-induced strainHarrington, Sophie A.; Zhai, Junyi; Denev, Sava; Gopalan, Venkatraman; Wang, Haiyan; Bi, Zhenxing; Redfern, Simon A. T.; Baek, Seung-Hyub; Bark, Chung W.; Eom, Chang-Beom; Jia, Quanxi; Vickers, Mary E.; MacManus-Driscoll, Judith L.Nature Nanotechnology (2011), 6 (8), 491-495CODEN: NNAABX; ISSN:1748-3387. (Nature Publishing Group)Ferroelec. materials are used in applications ranging from energy harvesting to high-power electronic transducers. However, industry-std. ferroelec. materials contain lead, which is toxic and environmentally unfriendly. The preferred alternative, BaTiO3, is non-toxic and has excellent ferroelec. properties, but its Curie temp. of ∼130° is too low to be practical. Strain was used to enhance the Curie temp. of BaTiO3 and SrTiO3 films, but only for thicknesses of tens of nanometers, which is not thick enough for many device applications. Here, we increase the Curie temp. of micrometer-thick films of BaTiO3 to at least 330°, and the tetragonal-to-cubic structural transition temp. to beyond 800°, by interspersing stiff, self-assembled vertical columns of Sm2O3 throughout the film thickness. Lattice parameters are given. The columns, which are 10 nm in diam., strain the BaTiO3 matrix by 2.35%, forcing it to maintain its tetragonal structure and resulting in the highest BaTiO3 transition temps. so far.
- 57Lee, D.; Yoon, A.; Jang, S. Y.; Yoon, J.-G.; Chung, J.-S.; Kim, M.; Scott, J. F.; Noh, T. W. Giant Flexoelectric Effect in Ferroelectric Epitaxial Thin Films. Phys. Rev. Lett. 2011, 107, 057602, DOI: 10.1103/PhysRevLett.107.05760257https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXps1ent7Y%253D&md5=dc382c13be982ab3c707b993a2385acfGiant flexoelectric effect in ferroelectric epitaxial thin filmsLee, D.; Yoon, A.; Jang, S.-Y.; Yoon, J.-G.; Chung, J.-S.; Kim, M.; Scott, J. F.; Noh, T.-W.Physical Review Letters (2011), 107 (5), 057602/1-057602/4CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)We report on nanoscale strain gradients in ferroelec. HoMnO3 epitaxial thin films, resulting in a giant flexoelec. effect. Using grazing-incidence in-plane x-ray diffraction, we measured strain gradients in the films, which were 6 or 7 orders of magnitude larger than typical values reported for bulk oxides. The combination of TEM, elec. measurements, and electrostatic calcns. showed that flexoelectricity provides a means of tuning the phys. properties of ferroelec. epitaxial thin films, such as domain configurations and hysteresis curves.
Supporting Information
Supporting Information
The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsaelm.4c00875.
Angle-resolved PFM of BFO and BTO, topographic image, SHO fitting of amplitude and R2 value with frequency for BFO; SHO fitting of amplitude, phase sweep with frequency, and R2 value with frequency for BTO; optical image of a BFO thin film where PFM calibration is performed; SS-PFM waveform; KPFM before and after SS-PFM measurements on BFO; phase image, domain distribution, and phase–amplitude curve of a BFO thin film in the uncalibrated and calibrated conditions; phase–amplitude curve of a BTO thin film measured in uncalibrated and calibrated conditions; off-surface SS-PFM measurements, topographic image of BTO and BTO:SmO thin films; KPFM image of BTO and BTO:SmO; imprint variation at Vr = 0 for BTO:MgO; force, voltage, amplitude, and phase versus measurement time for BFO and BTO samples (PDF)
Supporting video file demonstrating the calibration procedure of a BFO thin film (MP4)
Terms & Conditions
Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.