New Lutetium Oxide: Electrically Conducting Rock-Salt LuO Epitaxial Thin Film
- Kenichi KaminagaKenichi KaminagaDepartment of Chemistry, The University of Tokyo, Tokyo 113-0033, JapanWPI-Advanced Institute for Materials Research and Core Research Cluster, Tohoku University, Sendai 980-8577, JapanMore by Kenichi Kaminaga
- ,
- Daichi Oka
- ,
- Tetsuya HasegawaTetsuya HasegawaDepartment of Chemistry, The University of Tokyo, Tokyo 113-0033, JapanMore by Tetsuya Hasegawa
- , and
- Tomoteru Fukumura*Tomoteru Fukumura*E-mail: [email protected]WPI-Advanced Institute for Materials Research and Core Research Cluster and Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, JapanDepartment of Chemistry, Tohoku University, Sendai 980-8578, JapanMore by Tomoteru Fukumura
Copyright © 2022 American Chemical Society. This publication is licensed under these Terms of Use.
This publication is Open Access under the license indicated. Learn More
Abstract
C-rare earth structure lutetium sesquioxide Lu2O3 has been recognized as a high-k widegap insulator with closed shell Lu3+ ions. In this study, rock-salt structure lutetium monoxide LuO with unusual valence of Lu2+ (4f145d1), previously known as the gaseous phase, was synthesized as an epitaxial thin film by the pulsed laser deposition method. In contrast with transparent and highly insulating Lu2O3, LuO possessed a dark-brown color and high electrical conductivity concomitant with strong spin–orbit coupling as a manifestation of Lu 5d electron carriers.
Introduction
ARTICLE SECTIONS
Among binary lutetium oxides, only Lu2O3 is the stable solid phase with closed shell trivalent Lu ions, (1) possessing a strong insulating behavior owing to its large band gap (5.8 ± 0.1 eV). (2−4) On the other hand, lutetium monoxide LuO has existed only as a gaseous phase (5−7) such as various rare earth monoxides with divalent cations (except EuO) because of its largely positive Gibbs formation energy of the solid phase. (1,8) However, various rock-salt type rare earth monoxides were recently synthesized in the form of epitaxial thin films owing to nonequilibrium kinetic growth of the pulsed laser deposition method. For example, YO is a narrow gap semiconductor, (9) SmO is a heavy fermionic metal, (10) and LaO is a superconductor. (11) In this study, we report the first synthesis of rock-salt type LuO epitaxial thin films with unusual valence of Lu2+ (Lu2+: [Xe]4f145d1). In stark contrast with high-k insulator Lu2O3, (2−4) LuO exhibited a narrow band gap and high electrical conduction with a strong spin–orbit interaction originating from its 5d electron carriers.
Experimental Section
ARTICLE SECTIONS
LuO epitaxial thin films were deposited by the pulsed laser deposition method. The Lu2O3 polycrystalline pellet sintered at 1400 °C was used as a target. The thin films were grown at 300 °C on CaF2(001) (a = 5.4630 Å) substrates using KrF excimer laser (λ = 248 nm) with an energy density of 1.6 J/cm2 and a repetition ratio of 15 Hz. Ar + 1% O2 mixed gas was supplied during the deposition to keep oxygen partial pressure PO2 of 6 × 10–10 Torr measured with a quadrupole mass analyzer. Reflection high energy electron diffraction during deposition was in situ monitored to confirm the streak pattern of the thin films. The film surface was in situ capped with an AlOx layer at room temperature to prevent oxidation.The typical film thickness was approximately 150 nm. From X-ray reflectivity measurement of a referential sample, thickness of the LuO layer and the Lu2O3 layer was estimated to be approximately 105 and 40 nm, respectively. The Lu2O3 thin film on CaF2(001) substrates was also deposited as a reference for the absorption spectrum and quantitative analysis by X-ray photoelectron spectroscopy (XPS). θ–2θ X-ray diffractions (XRD) and two-dimensional reciprocal space mapping (RSM) were measured with Cu Kα1 radiation. XPS combined with Ar+ sputtering was measured using a monochromated Al Kα source to evaluate ionic valence, where the XPS peak positions were calibrated by the C 1s peak position (284.8 eV). The absence of the impurity element was confirmed by XPS (Figure S1). Absorption spectra were obtained from transmittance and reflectance. Resistivity and the Hall effect under out-of-plane magnetic field were measured using a Hall bar-shaped sample with 1 mm width and 3 mm length to evaluate carrier density and mobility from 2 to 300 K.
Results and Discussion
ARTICLE SECTIONS
Figure 1a shows the θ–2θ XRD pattern of the LuO thin film. Two peaks at 2θ = 36.952° and 78.943° corresponded to the rock-salt structure LuO 002 and 004 diffractions, respectively. In addition, cubic Lu2O3 00n peaks were observed as a result of surface oxidation of LuO similar to the Y2O3 surface layer of the YO thin film, (9,12) in which Lu2O3 002, 006, and 0010 forbidden peaks were generated because of oxygen vacancies. Figure 1b shows a two-dimensional RSM of the same LuO thin film as that in Figure 1a. Both the LuO thin film and the cubic Lu2O3 layer were fully relaxed and epitaxially grown on the CaF2 substrate with the epitaxial relationships of LuO [001]∥CaF2 [001] and Lu2O3 [001]∥CaF2 [001], respectively. The lattice constants of LuO were a = b = 4.76 Å and c = 4.79 Å (inset of Figure 1b). The ionic radius of Lu2+ in LuO was evaluated to be 0.984 Å from the cube root of the cell volume. This value is slightly smaller than the ionic radius of Lu2+ (1.02 Å) calculated from the empirical formula (14) with the Shannon’s ionic radius of 6-coordinated Lu3+, (13) possibly because of the spatially extended 5d orbital in Lu2+ in comparison with the 4f orbital in Lu3+. (15)
Figure 1
Figure 1. (a) θ–2θ XRD pattern for the LuO thin film on the CaF2(001) substrate. (b) RSM around the 204 diffraction peak of the CaF2 substrate, the 204 diffraction peak of the LuO thin film, and the 408 diffraction peak of the cubic Lu2O3 film. The inset shows the rock-salt structure of LuO. The structure was drawn by the VESTA program. (23)
Figure 2 shows Lu 4f XPS spectra for LuO and Lu2O3 thin films. The XPS spectrum of the Lu2O3 thin film was composed of dominant Lu3+ peaks, small Lu0 peaks, plasmons peak, and O 2p peak (Figure 2b), in which the Lu0 4f7/2 peak position (6.5 eV) was consistent with the previous study. (16,17) For LuO thin films, the Lu2+ 4f7/2 peak at 8.0 eV was dominant and located between the Lu3+ 4f7/2 peak at 8.3 eV and the Lu0 4f7/2 peak at 6.5 eV (Figure 2a). The composition was determined to be Lu1O0.90 from the areal intensity ratio of Lu 4d5/2 and O 1s peaks in the LuO thin film, taking into account the inelastic mean free paths obtained from the TPP-2M predictive equation (see the Supporting Information). (18) The presence of oxygen vacancies in the LuO thin film was consistent with electron carrier conduction in the LuO thin film as described below.
Figure 2
Figure 2. Lu 4f XPS spectra for (a) LuO and (b) Lu2O3 films on CaF2(001) substrates after Ar+ etching (open symbol). Fitting curves (solid curve) and the deconvoluted Lu0 (gray), Lu2+ (red), Lu3+ (blue), the plasmons (green), and O 2p (yellow) spectra are also shown.
The inset of Figure 3 shows photographs of LuO and Lu2O3 thin films. In contrast with the bluish transparent Lu2O3 thin film, the LuO thin film possessed dark-brown color as a result of its visible light absorption. Figure 3 shows absorption spectra of LuO and Lu2O3 thin films. Lu2O3 showed sharp absorption edge with negligible in-gap absorption. On the other hand, the LuO thin film showed a significant and broad visible absorption. The spectral shape shows remarkable resemblance with that of the YO thin film (9) and those of Yb monochalcogenides (YbX, X = S, Se, and Te) thin films. (19) As indicated in Figure 3, the characteristic absorption energies could be attributed to Lu 4f → Lu 5d t2g transition (A), Lu 4f → Lu 5d eg transition (B), O 2p → Lu 5d t2g transition (D), and O 2p → Lu 5d eg transition superposed with intergap absorption of the Lu2O3 surface oxidation layer (E). A kink at around 4 eV (C) was similar to that in the YO thin film, (9) in spite of the unknown origin. The spectral resemblance between LuO and YO is caused by similar d1 electronic configuration of Lu2+ with Y2+.
Figure 3
Figure 3. Absorption spectra of the LuO thin film and the Lu2O3 film. Inset shows photographs of LuO and Lu2O3 films. The indices (A–E) are explained in text.
Figure 4a–c shows temperature dependence of the electrical conductivity, the carrier density, and the mobility for the LuO thin film. The temperature dependence of conductivity in the LuO thin film showed a metallic behavior (Figure 4a). The carrier polarity was n-type, probably originated from 5d electrons of Lu2+ and oxygen vacancies serving as an electron donor. The carrier density and the mobility were insignificantly changed for 2–300 K, and those at 300 K were 7.4 × 1020 cm–3 and 0.46 cm2/V s, respectively (Figure 4b,c), which were approximately the same as those of metallic YO thin films. (9) The carrier density was extremely small, assuming fully itinerant 5d electrons from Lu2+, estimated to be the carrier density of 3.7 × 1022 cm–3, possibly caused by strong electron correlation between the 5d electrons. Figure 4d shows temperature dependence of resistivity for the LuO thin film at 0 and 9 T. The resistivity of the LuO thin film showed the local minimum at 28 K corresponding to the local maximum of the carrier density (Figure 4b). The resistivity proportional to −log T below 28 K suggests the appearance of the Kondo effect persisting up to 9 T, possibly originated from the presence of oxygen vacancies observed in YO. (9)Figure 4e shows isothermal magnetoresistance of the LuO thin film at 2–50 K. The positive magnetoresistance is thought to be originated from the weak antilocalization effect, indicating strong spin–orbit coupling of the Lu 5d orbital. The maximum magnetoresistance at 2 K and 9 T was +2.6%, which was much larger than that of the YO thin film +0.96%, (9) possibly caused by the larger spin–orbit coupling owing to the heavier Lu element. (20)
Figure 4
Figure 4. Temperature dependence of (a) conductivity, (b) carrier density, and (c) mobility for the LuO thin film. (d) Temperature dependence of resistivity for the LuO thin film under 0 and 9 T. (e) Isothermal magnetoresistance of the LuO thin film at different temperatures.
Conclusions
ARTICLE SECTIONS
In summary, we synthesized solid phase rock-salt LuO with unusual valence Lu2+ in the form of the epitaxial thin film for the first time. The LuO thin film showed strong visible absorption and high electrical conduction, in stark contrast with Lu2O3. In addition, the Kondo effect and sizable positive magnetoresistance were observed. The strong spin–orbit interaction in this compound would be useful for spintronic electrodes in heterojunctions like Pt and IrO2. (21,22)
Supporting Information
ARTICLE SECTIONS
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsomega.8b02082.
PDF data, discussion of quantitative analysis of the LuO thin film, and typical XPS spectrum for the LuO(001) epitaxial thin film (PDF)
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.
Author Information
ARTICLE SECTIONS
- Tomoteru Fukumura - WPI-Advanced Institute for Materials Research and Core Research Cluster and Center for Spintronics Research Network, and , Tohoku University, Sendai 980-8577, Japan; Department of Chemistry, Tohoku University, Sendai 980-8578, Japan;
http://orcid.org/0000-0002-8957-3520;
- Kenichi Kaminaga - Department of Chemistry, The University of Tokyo, Tokyo 113-0033, Japan; WPI-Advanced Institute for Materials Research and Core Research Cluster, and , Tohoku University, Sendai 980-8577, Japan;http://orcid.org/0000-0001-7331-7453
- Daichi Oka - Department of Chemistry, Tohoku University, Sendai 980-8578, Japan;http://orcid.org/0000-0003-2747-9675
Acknowledgments
ARTICLE SECTIONS
XPS measurement was conducted at Research Hub for Advanced Nano Characterization, The University of Tokyo, under the support of the Nanotechnology Platform by MEXT, Japan (no. 12024046). This work is supported by JST-CREST, JSPS-KAKENHI (nos. 26105002, JP17J05331, 18H03872), and the Mitsubishi Foundation.
References
ARTICLE SECTIONS
This article references 23 other publications.
- 1Adachi, G.-y.; Imanaka, N. The Binary Rare Earth Oxides. Chem. Rev. 1999, 98, 1479– 1514, DOI: 10.1021/cr940055h
- 2Perego, M.; Seguini, G.; Scarel, G.; Fanciulli, M. X-ray photoelectron spectroscopy study of energy-band alignments of Lu2O3 on Ge. Surf. Interface Anal. 2006, 38, 494– 497, DOI: 10.1002/sia.2268[Crossref], [CAS], Google Scholar2https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28XkvVCisLs%253D&md5=85ca2b35e63d7ba1498a1dfff4ff0efcX-ray photoelectron spectroscopy study of energy-band alignments of Lu2O3 on GePerego, M.; Seguini, G.; Scarel, G.; Fanciulli, M.Surface and Interface Analysis (2006), 38 (4), 494-497CODEN: SIANDQ; ISSN:0142-2421. (John Wiley & Sons Ltd.)XPS was used to investigate the band alignment of Lu2O3 films with a Ge substrate. Lu2O3 films were grown on Ge (100) by at. layer deposition. The conduction- (CBO) and valence- (VBO) band offsets of the Lu2O3/Ge heterojunction were detd. to be 2.2 ± 0.1 and 2.9 ± 0.1 eV resp. Internal photoemission measurements performed on metal-oxide-semiconductor devices gave a CBO of 2.1 ± 0.1 eV and a VBO of 3.0 eV, in excellent agreement, within the exptl. error, with the values obtained by XPS.
- 3Darmawan, P.; Lee, P. S.; Setiawan, Y.; Ma, J.; Osipowicz, T. Effect of low fluence laser annealing on ultrathin Lu2O3 high-k dielectric. Appl. Phys. Lett. 2007, 91, 092903, DOI: 10.1063/1.2771065
- 4Darmawan, P.; Lee, P. S.; Setiawan, Y.; Lai, J. C.; Yang, P. Thermal stability of rare-earth based ultrathin Lu2O3 for high-k dielectrics. J. Vac. Sci. Technol., B: Microelectron. Nanometer Struct.-Process., Meas., Phenom. 2007, 25, 1203– 1206, DOI: 10.1116/1.2749526[Crossref], [CAS], Google Scholar4https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXovFKltbY%253D&md5=0e7defc18763015bf8a524eb6e50e589Thermal stability of rare-earth based ultrathin Lu2O3 for high-k dielectricsDarmawan, P.; Lee, P. S.; Setiawan, Y.; Lai, J. C.; Yang, P.Journal of Vacuum Science & Technology, B: Microelectronics and Nanometer Structures--Processing, Measurement, and Phenomena (2007), 25 (4), 1203-1206CODEN: JVSTBM; ISSN:1071-1023. (American Institute of Physics)Lu2O3 thin film was deposited on n-type (100) Si substrates using pulsed laser deposition. A k value of 15.95 with an equiv. oxide thickness (EOT) of 1.10 nm and a c.d. of 2.6×10-5 A/cm2 at +1 V accumulation bias is achievable for the 4.5 nm thick Lu2O3 thin film deposited at room temp. after postdeposition annealing at 600°C in oxygen ambient. Annealing a similar sample at 900 °C caused the EOT and leakage c.d. to increase to 1.68 nm and 1×10-4 A/cm2, resp. High resoln. transmission electron microscopy anal. has shown that Lu2O3 film remains amorphous at high temp. annealing at 900°C. An x-ray reflectivity anal. on a sep. prepd. sample with lower annealing temp. (800°C) suggested a formation of Lu-based silicate layer. It is believed that the formation of low-k silicate layer may have contributed to the obsd. increase in EOT and the redn. in the k value. (c) 2007 American Institute of Physics.
- 5Effantin, C.; Bacis, R.; Dincan, J. Rotational analysis of beta system and vibrational analysis of gamma LuO system. C. R. Seances Acad. Sci., Ser. B 1971, 273, 605Google ScholarThere is no corresponding record for this reference.
- 6Cooke, S. A.; Krumrey, C.; Gerry, M. C. L. Rotational spectroscopy of lutetium monoxide. J. Mol. Spectrosc. 2011, 267, 108– 111, DOI: 10.1016/j.jms.2011.02.017
- 7Liu, Z.; Xie, H.; Li, Q.; Qin, Z.; Cong, R.; Wu, X.; Tang, Z.; Fan, H. On the photoelectron velocity-map imaging of lutetium monoxide anion LuO. J. Chem. Phys. 2014, 140, 034312, DOI: 10.1063/1.4862142
- 8Leger, J. M.; Yacoubi, N.; Loriers, J. Synthesis of rare earth monoxides. J. Solid State Chem. 1981, 36, 261– 270, DOI: 10.1016/0022-4596(81)90436-9[Crossref], [CAS], Google Scholar8https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL3MXitVWqs7c%253D&md5=50f4e7e137af9ded6298a4ae28d9156cSynthesis of rare earth monoxidesLeger, J. M.; Yacoubi, N.; Loriers, J.Journal of Solid State Chemistry (1981), 36 (3), 261-70CODEN: JSSCBI; ISSN:0022-4596.The std. Gibbs energy changes for the formation of an ionic or metallic monoxide from rare earth metal and its sesquioxide were calcd. Under high pressures ionic YbO and lighter rare earth metallic monoxides should be obtained, which is confirmed by expts. in a belt-type app. in the range 15-80 kbar and 500-1200°. For Ln = La, Ce, Pr, Nd, Sm, a fcc. compd. is obtained from each reaction. The cell parameters are resp. 5.144, 5.089, 5.031, 4.994, and 4.943 ± 0.005 Å. The compds. appear golden yellow with a metallic luster. From chem. analyses and cell parameter considerations these compds. are identified as the rare earth monoxides. For Ln = Gd, Dy, Tm, no reaction is obsd. at 50 kbar and 1000°. The rare earth monoxides show a variety of properties: LaO, CeO, PrO, and NdO are metallic with the rare earth in the trivalent state; EuO and YbO are semiconductors with the rare earth in the divalent state; SmO is metallic with Sm in an intermediate valence state close to 3.
- 9Kaminaga, K.; Sei, R.; Hayashi, K.; Happo, N.; Tajiri, H.; Oka, D.; Fukumura, T.; Hasegawa, T. A divalent rare earth oxide semiconductor: Yttrium monoxide. Appl. Phys. Lett. 2016, 108, 122102, DOI: 10.1063/1.4944330
- 10Uchida, Y.; Kaminaga, K.; Fukumura, T.; Hasegawa, T. Samarium monoxide epitaxial thin film as a possible heavy-fermion compound. Phys. Rev. B 2017, 95, 125111, DOI: 10.1103/physrevb.95.125111
- 11Kaminaga, K.; Oka, D.; Hasegawa, T.; Fukumura, T. Superconductivity of Rock-Salt Structure LaO Epitaxial Thin Film. J. Am. Chem. Soc. 2018, 140, 6754– 6757, DOI: 10.1021/jacs.8b03009[ACS Full Text
], [CAS], Google Scholar11https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXpvVakurs%253D&md5=20a14f14942d5986d05cb78a0d2efb19Superconductivity of Rock-Salt Structure LaO Epitaxial Thin FilmKaminaga, Kenichi; Oka, Daichi; Hasegawa, Tetsuya; Fukumura, TomoteruJournal of the American Chemical Society (2018), 140 (22), 6754-6757CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The authors report a superconducting transition in a LaO epitaxial thin film with the superconducting transition onset temp. (Tc) at ∼5 K. This Tc is higher than those of other lanthanum monochalcogenides and opposite to their chem. trend: Tc = 0.84, 1.02, and 1.48 K for LaX (X = S, Se, Te), resp. The carrier control resulted in a dome-shaped Tc as a function of electron carrier d. The Tc was significantly sensitive to epitaxial strain in spite of the highly sym. crystal structure. This rock-salt superconducting LaO could be a building block to design novel superlattice superconductors. - 12Stellhorn, J. R.; Hosokawa, S.; Happo, N.; Tajiri, H.; Matsushita, T.; Kaminaga, K.; Fukumura, T.; Hasegawa, T.; Hayashi, K. A valence-selective X-ray fluorescence holography study of an yttrium oxide thin film. J. Appl. Crystallogr. 2017, 50, 1583– 1589, DOI: 10.1107/s1600576717012821[Crossref], [CAS], Google Scholar12https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhvFahtLfF&md5=25474a007f86956809b58160e30ee0b4A valence-selective X-ray fluorescence holography study of an yttrium oxide thin filmStellhorn, J. R.; Hosokawa, S.; Happo, N.; Tajiri, H.; Matsushita, T.; Kaminaga, K.; Fukumura, T.; Hasegawa, T.; Hayashi, K.Journal of Applied Crystallography (2017), 50 (6), 1583-1589CODEN: JACGAR; ISSN:1600-5767. (International Union of Crystallography)The first direct valence-selective structure detn. by X-ray fluorescence holog. is reported. The method is applied to investigate an epitaxial thin film of the rare earth monoxide YO, which has recently been synthesized by pulsed laser deposition. The surface of the sample is easily oxidized to Y2O3. In order to sep. the structural information connected with the two different valence states of Y, the X-ray fluorescence holog. measurements were performed close to the Y K absorption edge. Using the shift of the absorption edge for the different valence states, very different relative contributions of YO and Y2O3 are obtained. Thus, it is possible to distinguish the crystal structures of YO and Y2O3 in the thin-film sample.
- 13Shannon, R. D. Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. Acta Crystallogr., Sect. A: Cryst. Phys., Diffr., Theor. Gen. Crystallogr. 1976, 32, 751– 767, DOI: 10.1107/s0567739476001551
- 14Jia, Y. Q. Crystal radii and effective ionic radii of the rare earth ions. J. Solid State Chem. 1991, 95, 184– 187, DOI: 10.1016/0022-4596(91)90388-x[Crossref], [CAS], Google Scholar14https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK3MXmvFWksr0%253D&md5=a41ad00fccb05a9ac413d01fb2deae88Crystal radii and effective ionic radii of the rare earth ionsJia, Y. Q.Journal of Solid State Chemistry (1991), 95 (1), 184-7CODEN: JSSCBI; ISSN:0022-4596.There exist some relations between the crystal radii of the rare earth ions, the 4f electron no., and the coordination no. On the basis of these relations, 2 empirical formulas are proposed to calc. the unknown crystal radii of the rare earth ions from the known crystal radii of the trivalent rare earth ions. The crystal radii and effective ionic radii of all the rare earth ions (trivalent and divalent) with different coordination no. (N = 6-12) were evaluated. The calcd. results are very satisfactory, and for most of examples the relative error is <1.0%.
- 15Cox, P. A. The Electronic Structure and Chemistry of Solids; Oxford University Press: New York, 1987.Google ScholarThere is no corresponding record for this reference.
- 16Kaichev, V. V.; Asanova, T. I.; Erenburg, S. B.; Perevalov, T. V.; Shvets, V. A.; Gritsenko, V. A. Atomic and electronic structures of lutetium oxide Lu2O3. J. Exp. Theor. Phys. 2013, 116, 323– 329, DOI: 10.1134/s1063776113020131[Crossref], [CAS], Google Scholar16https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXktVKjtrw%253D&md5=3ae61c2c5e4996d32b1ecefafc020813Atomic and electronic structures of lutetium oxide Lu2O3Kaichev, V. V.; Asanova, T. I.; Erenburg, S. B.; Perevalov, T. V.; Shvets, V. A.; Gritsenko, V. A.Journal of Experimental and Theoretical Physics (2013), 116 (2), 323-329CODEN: JTPHES; ISSN:1063-7761. (MAIK Nauka/Interperiodica)The chem. compn., electronic structure, structure, and phys. properties a Lu oxide Lu2O3 film were studied by XPS, ellipsometry, and x-ray absorption spectroscopy. The short-range order in Lu2O3 is found to correspond to its cubic modification. The binding energies of the 1s and 2p levels of O and the 4d5/2 and 4f7/2 levels of Lu are 529.2, 5.0 and 7.4, 195.9 eV, resp. The energy gap detd. from the electron energy loss spectrum of the film is 5.9 eV. The electron energy loss spectra have two peaks at 17.4 and 22.0 eV, which can be attributed to the excitation of bulk plasma oscillations. The dispersion of the refractive index is measured by spectral ellipsometry. The refractive index increases from 1.82 at 1.5 eV to 2.18 at 5.0 eV, and the high-frequency permittivity of Lu2O3 is 3.31.
- 17Yermolayeva, Y. V.; Tolmachev, A. V.; Korshikova, T. I.; Yavetskiy, R. P.; Dobrotvorskaya, M. V.; Danylenko, N. I.; Sofronov, D. S. Spherical core–shell structured nanophosphors on the basis of europium-doped lutetium compounds. Nanotechnology 2009, 20, 325601, DOI: 10.1088/0957-4484/20/32/325601
- 18Tanuma, S.; Powell, C. J.; Penn, D. R. Calculation of electron inelastic mean free paths (IMFPs) VII. Reliability of the TPP-2M IMFP predictive equation. Surf. Interface Anal. 2003, 35, 268– 275, DOI: 10.1002/sia.1526[Crossref], [CAS], Google Scholar18https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXisVegu70%253D&md5=35bbab150b6fce516cb82e97f24e525aCalculation of electron inelastic mean free paths (IMFPs) VII. Reliability of the TPP-2M IMFP predictive equationTanuma, S.; Powell, C. J.; Penn, D. R.Surface and Interface Analysis (2003), 35 (3), 268-275CODEN: SIANDQ; ISSN:0142-2421. (John Wiley & Sons Ltd.)The authors report comparisons of electron inelastic mean free paths (IMFPs) detd. from predictive IMFP equation TPP-2M and ref. IMFPs calcd. from optical data. These comparisons were made for values of the parameter Nv (the no. of valence electrons per atom or mol.) that the authors have recommended and those that were recommended in a recent paper by Seah et al. (Surf. Interface Anal. 2001; 31: 778). The comparisons were made for 8 elemental solids (K, Y, Gd, Tb, Dy, Hf, Ta and Bi) and 2 compds. (KBr and Y2O3) for which there were appreciable differences in the recommended Nv values from the 2 sources and for which optical data were available for the IMFP calcns. The av. of the root-mean-square deviations for the 10 materials between IMFPs from the TPP-2M equation with Nv values and the ref. IMFPs was 11.0%, whereas the corresponding av. with the Seah et al. Nv values was 20.2%. The larger av. in the latter comparison was mainly due to large (>20%) root-mean-square deviations for 4 materials (K, Hf, Ta and KBr). For the other 6 materials, the root-mean-square deviations with the Seah et al. values of Nv were similar to those with values of Nv. Based on the comparisons for these 10 materials, probably it is preferable to use values of Nv in the TPP-2M equation.
- 19Narayanamurti, V.; Jayaraman, A.; Bucher, E. Optical absorption in ytterbium monochalcogenides under pressure. Phys. Rev. B: Solid State 1974, 9, 2521– 2523, DOI: 10.1103/physrevb.9.2521[Crossref], [CAS], Google Scholar19https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaE2cXktVyjsrg%253D&md5=702b998b6aaaa5559744740bc1ef3821Optical absorption in ytterbium monochalcogenides under pressureNarayanamurti, V.; Jayaraman, A.; Bucher, E.Physical Review B: Solid State (1974), 9 (6), 2521-3CODEN: PLRBAQ; ISSN:0556-2805.The pressure dependence of the lowest-lying 4f → 5d absorption band in cryst. films of YbTe, YbSe, and YbS was studied. The absorption edge which occurs at ∼1.8 in YbTe, 1.5 in YbSe, and 1.1 eV in YbS at zero pressure closes at a rate of 11.0, 9.8, and 6.5 meV/kbar, resp., for pressures up to 8 kbar. The measurements predict gap collapses in all the 3 chalcogenides at pressures of ∼175 kbar, in good agreement with pressure-vol. studies and qual. changes in the reflectivity at high pressures.
- 20Ogasawara, H.; Kotani, A.; Thole, B. T. Lifetime effect on the multiplet structure of 4d x-ray-photoemission spectra in heavy rare-earth elements. Phys. Rev. B: Condens. Matter Mater. Phys. 1994, 50, 12332– 12341, DOI: 10.1103/physrevb.50.12332
- 21Kimura, T.; Otani, Y.; Sato, T.; Takahashi, S.; Maekawa, S. Room-temperature reversible spin Hall effect. Phys. Rev. Lett. 2007, 98, 156601, DOI: 10.1103/physrevlett.98.249901[Crossref], [PubMed], [CAS], Google Scholar21https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXkt1Grsr4%253D&md5=63cadea7ac51690ebae0c7d1c2413881Room-Temperature Reversible Spin Hall EffectKimura, T.; Otani, Y.; Sato, T.; Takahashi, S.; Maekawa, S.Physical Review Letters (2007), 98 (15), 156601/1-156601/4CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)Reversible spin Hall effect comprising the direct and inverse spin Hall effects was elec. detected at room temp. A platinum wire with a strong spin-orbit interaction is used not only as a spin current absorber but also as a spin-current source in the specially designed lateral structure. The obtained spin Hall conductivities are 2.4×104 (Ωm)-1 at room temp., 104 times larger than the previously reported values of semiconductor systems. Spin Hall conductivities obtained from both the direct and inverse spin Hall effects are exptl. confirmed to be the same, demonstrating the Onsager reciprocal relations between spin and charge currents.
- 22Fujiwara, K.; Fukuma, Y.; Matsuno, J.; Idzuchi, H.; Niimi, Y.; Otani, Y.; Takagi, H. 5d iridium oxide as a material for spin-current detection. Nat. Commun. 2013, 4, 2893, DOI: 10.1038/ncomms3893[Crossref], [PubMed], [CAS], Google Scholar22https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BC2c3lsVyqtA%253D%253D&md5=3a65a3f9d27c6b482e066c38e61594115d iridium oxide as a material for spin-current detectionFujiwara Kohei; Fukuma Yasuhiro; Matsuno Jobu; Idzuchi Hiroshi; Niimi Yasuhiro; Otani Yoshichika; Takagi HidenoriNature communications (2013), 4 (), 2893 ISSN:.Devices based on pure spin currents have been attracting increasing attention as key ingredients for low-dissipation electronics. To integrate such spintronics devices into charge-based technologies, electric detection of spin currents is essential. The inverse spin Hall effect converts a spin current into an electric voltage through spin-orbit coupling. Noble metals such as Pt and Pd, and also Cu-based alloys, have been regarded as potential materials for a spin-current injector, owing to the large direct spin Hall effect. Their spin Hall resistivity ρSH, representing the performance as a detector, is not large enough, however, due mainly because of their low charge resistivity. Here we report that a binary 5d transition metal oxide, iridium oxide, overcomes the limitations encountered in noble metals and Cu-based alloys and shows a very large ρSH~38 μΩ cm at room temperature.
- 23Momma, K.; Izumi, F. VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data. J. Appl. Crystallogr. 2011, 44, 1272– 1276, DOI: 10.1107/s0021889811038970[Crossref], [CAS], Google Scholar23https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhsFSisrvP&md5=885fbd9420ed18838813d6b0166f4278VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology dataMomma, Koichi; Izumi, FujioJournal of Applied Crystallography (2011), 44 (6), 1272-1276CODEN: JACGAR; ISSN:0021-8898. (International Union of Crystallography)VESTA is a 3D visualization system for crystallog. studies and electronic state calcns. It was upgraded to the latest version, VESTA 3, implementing new features including drawing the external morphpol. of crysals; superimposing multiple structural models, volumetric data and crystal faces; calcn. of electron and nuclear densities from structure parameters; calcn. of Patterson functions from the structure parameters or volumetric data; integration of electron and nuclear densities by Voronoi tessellation; visualization of isosurfaces with multiple levels, detn. of the best plane for selected atoms; an extended bond-search algorithm to enable more sophisticated searches in complex mols. and cage-like structures; undo and redo is graphical user interface operations; and significant performance improvements in rendering isosurfaces and calcg. slices.
Cited By
This article is cited by 16 publications.
- Francesco Di Quarto, Andrea Zaffora, Francesco Di Franco, Monica Santamaria. Band Gap Modeling of Different Ternary and Quaternary Alumina Garnet Phases Y3(AlxGa1–x)5O12 (YAGG) and Lu3(AlxGa1–x)5O12 (LuAGG). A Semiempirical Approach. The Journal of Physical Chemistry C 2022, 126 (40) , 17313-17327. https://doi.org/10.1021/acs.jpcc.2c04523
- Daichi Saito, Daichi Oka, Kenichi Kaminaga, Miho Kitamura, Daisuke Shiga, Hiroshi Kumigashira, Tomoteru Fukumura. Thickness-dependent magnetotransport properties of rocksalt NdO epitaxial thin films: observation of a ferromagnetic phase far above the Curie temperature. Journal of Materials Chemistry C 2023, 11 (36) , 12400-12405. https://doi.org/10.1039/D3TC02478D
- Emeka Ndaguba, Jua Cilliers, Sumita Ghosh, Shanaka Herath, Eveline Tancredo Mussi. Operability of Smart Spaces in Urban Environments: A Systematic Review on Enhancing Functionality and User Experience. Sensors 2023, 23 (15) , 6938. https://doi.org/10.3390/s23156938
- Wan-Yu Lyu, Wei-Di Liu, Meng Li, Xiao-Lei Shi, Min Hong, Tianyi Cao, Kai Guo, Jun Luo, Jin Zou, Zhi-Gang Chen. Condensed point defects enhance thermoelectric performance of rare-earth Lu-doped GeTe. Journal of Materials Science & Technology 2023, 151 , 227-233. https://doi.org/10.1016/j.jmst.2023.01.004
- Shunda Zhang, Jiachang Bi, Ruyi Zhang, Peiyi Li, Fugang Qi, Zhiyang Wei, Yanwei Cao. Electronic and magnetic properties of Lu and LuH2. AIP Advances 2023, 13 (6) https://doi.org/10.1063/5.0153011
- M. Coskun, Ozgur Polat, Y. Yildirim, Z. Durmus, C. Sen, Y. Caglar, M. Caglar, A. Turut. High resistivity and low dielectric loss of LuFe1−xOsxO3 (x = 0.0–0.10) ferrites. Journal of Materials Science: Materials in Electronics 2023, 34 (8) https://doi.org/10.1007/s10854-023-10141-2
- Sergey V. Ushakov, Qi-Jun Hong, Dustin A. Gilbert, Alexandra Navrotsky, Axel van de Walle. Thorium and Rare Earth Monoxides and Related Phases. Materials 2023, 16 (4) , 1350. https://doi.org/10.3390/ma16041350
- Satoshi Sasaki, Daichi Oka, Kenichi Kaminaga, Daichi Saito, Taku Yamamoto, Nobuto Abe, Hirokazu Shimizu, Tomoteru Fukumura. A high- T C heavy rare earth monoxide semiconductor TbO with a more than half-filled 4f orbital. Dalton Transactions 2022, 51 (43) , 16648-16652. https://doi.org/10.1039/D2DT02710K
- Nobuto Abe, Daichi Oka, Kenichi Kaminaga, Daisuke Shiga, Daichi Saito, Taku Yamamoto, Noriaki Kimura, Hiroshi Kumigashira, Tomoteru Fukumura. Rocksalt CeO epitaxial thin film as a heavy-fermion system transiting from p -type metal to partially compensated n -type metal by 4 f delocalization. Physical Review B 2022, 106 (12) https://doi.org/10.1103/PhysRevB.106.125106
- Tahta Amrillah, Daichi Oka, Hirokazu Shimizu, Satoshi Sasaki, Daichi Saito, Kenichi Kaminaga, Tomoteru Fukumura. Rock salt-type HoO epitaxial thin film as a heavy rare-earth monoxide ferromagnetic semiconductor with a Curie temperature above 130 K. Applied Physics Letters 2022, 120 (8) https://doi.org/10.1063/5.0081040
- S. Irimiciuc, J. More-Chevalier, S. Chertpalov, L. Fekete, M. Novotný, Š. Havlová, M. Poupon, T. Zikmund, K. Kůsová, J. Lančok. In-situ plasma monitoring by optical emission spectroscopy during pulsed laser deposition of doped Lu2O3. Applied Physics B 2021, 127 (10) https://doi.org/10.1007/s00340-021-07689-4
- Pei-Han Sun, Jian-Feng Zhang, Kai Liu, Qiang Han, Zhong-Yi Lu. First-principles study of the superconductivity in LaO. Physical Review B 2021, 104 (4) https://doi.org/10.1103/PhysRevB.104.045121
- Shoya Sakamoto, Kenichi Kaminaga, Daichi Oka, Ryu Yukawa, Masafumi Horio, Yuichi Yokoyama, Kohei Yamamoto, Kou Takubo, Yosuke Nonaka, Keisuke Koshiishi, Masaki Kobayashi, Arata Tanaka, Akira Yasui, Eiji Ikenaga, Hiroki Wadati, Hiroshi Kumigashira, Tomoteru Fukumura, Atsushi Fujimori. Hard and soft x-ray photoemission spectroscopy study of the new Kondo system SmO thin film. Physical Review Materials 2020, 4 (9) https://doi.org/10.1103/PhysRevMaterials.4.095001
- Taku Yamamoto, Kenichi Kaminaga, Daichi Saito, Daichi Oka, Tomoteru Fukumura. Rock salt structure GdO epitaxial thin film with a high ferromagnetic Curie temperature. Applied Physics Letters 2020, 117 (5) https://doi.org/10.1063/5.0017954
- Kenichi Kaminaga, Daichi Oka, Hirofumi Oka, Tomoteru Fukumura. Heteroepitaxy of Rock-salt Superconductor/Ferromagnet Thin Film: LaO/EuO. Chemistry Letters 2019, 48 (10) , 1244-1247. https://doi.org/10.1246/cl.190460
- Taku Yamamoto, Kenichi Kaminaga, Daichi Saito, Daichi Oka, Tomoteru Fukumura. High electron mobility with significant spin-orbit coupling in rock-salt YbO epitaxial thin film. Applied Physics Letters 2019, 114 (16) https://doi.org/10.1063/1.5085938
Abstract
Figure 1
Figure 1. (a) θ–2θ XRD pattern for the LuO thin film on the CaF2(001) substrate. (b) RSM around the 204 diffraction peak of the CaF2 substrate, the 204 diffraction peak of the LuO thin film, and the 408 diffraction peak of the cubic Lu2O3 film. The inset shows the rock-salt structure of LuO. The structure was drawn by the VESTA program. (23)
Figure 2
Figure 2. Lu 4f XPS spectra for (a) LuO and (b) Lu2O3 films on CaF2(001) substrates after Ar+ etching (open symbol). Fitting curves (solid curve) and the deconvoluted Lu0 (gray), Lu2+ (red), Lu3+ (blue), the plasmons (green), and O 2p (yellow) spectra are also shown.
Figure 3
Figure 3. Absorption spectra of the LuO thin film and the Lu2O3 film. Inset shows photographs of LuO and Lu2O3 films. The indices (A–E) are explained in text.
Figure 4
Figure 4. Temperature dependence of (a) conductivity, (b) carrier density, and (c) mobility for the LuO thin film. (d) Temperature dependence of resistivity for the LuO thin film under 0 and 9 T. (e) Isothermal magnetoresistance of the LuO thin film at different temperatures.
References
ARTICLE SECTIONSThis article references 23 other publications.
- 1Adachi, G.-y.; Imanaka, N. The Binary Rare Earth Oxides. Chem. Rev. 1999, 98, 1479– 1514, DOI: 10.1021/cr940055h
- 2Perego, M.; Seguini, G.; Scarel, G.; Fanciulli, M. X-ray photoelectron spectroscopy study of energy-band alignments of Lu2O3 on Ge. Surf. Interface Anal. 2006, 38, 494– 497, DOI: 10.1002/sia.2268[Crossref], [CAS], Google Scholar2https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28XkvVCisLs%253D&md5=85ca2b35e63d7ba1498a1dfff4ff0efcX-ray photoelectron spectroscopy study of energy-band alignments of Lu2O3 on GePerego, M.; Seguini, G.; Scarel, G.; Fanciulli, M.Surface and Interface Analysis (2006), 38 (4), 494-497CODEN: SIANDQ; ISSN:0142-2421. (John Wiley & Sons Ltd.)XPS was used to investigate the band alignment of Lu2O3 films with a Ge substrate. Lu2O3 films were grown on Ge (100) by at. layer deposition. The conduction- (CBO) and valence- (VBO) band offsets of the Lu2O3/Ge heterojunction were detd. to be 2.2 ± 0.1 and 2.9 ± 0.1 eV resp. Internal photoemission measurements performed on metal-oxide-semiconductor devices gave a CBO of 2.1 ± 0.1 eV and a VBO of 3.0 eV, in excellent agreement, within the exptl. error, with the values obtained by XPS.
- 3Darmawan, P.; Lee, P. S.; Setiawan, Y.; Ma, J.; Osipowicz, T. Effect of low fluence laser annealing on ultrathin Lu2O3 high-k dielectric. Appl. Phys. Lett. 2007, 91, 092903, DOI: 10.1063/1.2771065
- 4Darmawan, P.; Lee, P. S.; Setiawan, Y.; Lai, J. C.; Yang, P. Thermal stability of rare-earth based ultrathin Lu2O3 for high-k dielectrics. J. Vac. Sci. Technol., B: Microelectron. Nanometer Struct.-Process., Meas., Phenom. 2007, 25, 1203– 1206, DOI: 10.1116/1.2749526[Crossref], [CAS], Google Scholar4https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXovFKltbY%253D&md5=0e7defc18763015bf8a524eb6e50e589Thermal stability of rare-earth based ultrathin Lu2O3 for high-k dielectricsDarmawan, P.; Lee, P. S.; Setiawan, Y.; Lai, J. C.; Yang, P.Journal of Vacuum Science & Technology, B: Microelectronics and Nanometer Structures--Processing, Measurement, and Phenomena (2007), 25 (4), 1203-1206CODEN: JVSTBM; ISSN:1071-1023. (American Institute of Physics)Lu2O3 thin film was deposited on n-type (100) Si substrates using pulsed laser deposition. A k value of 15.95 with an equiv. oxide thickness (EOT) of 1.10 nm and a c.d. of 2.6×10-5 A/cm2 at +1 V accumulation bias is achievable for the 4.5 nm thick Lu2O3 thin film deposited at room temp. after postdeposition annealing at 600°C in oxygen ambient. Annealing a similar sample at 900 °C caused the EOT and leakage c.d. to increase to 1.68 nm and 1×10-4 A/cm2, resp. High resoln. transmission electron microscopy anal. has shown that Lu2O3 film remains amorphous at high temp. annealing at 900°C. An x-ray reflectivity anal. on a sep. prepd. sample with lower annealing temp. (800°C) suggested a formation of Lu-based silicate layer. It is believed that the formation of low-k silicate layer may have contributed to the obsd. increase in EOT and the redn. in the k value. (c) 2007 American Institute of Physics.
- 5Effantin, C.; Bacis, R.; Dincan, J. Rotational analysis of beta system and vibrational analysis of gamma LuO system. C. R. Seances Acad. Sci., Ser. B 1971, 273, 605Google ScholarThere is no corresponding record for this reference.
- 6Cooke, S. A.; Krumrey, C.; Gerry, M. C. L. Rotational spectroscopy of lutetium monoxide. J. Mol. Spectrosc. 2011, 267, 108– 111, DOI: 10.1016/j.jms.2011.02.017
- 7Liu, Z.; Xie, H.; Li, Q.; Qin, Z.; Cong, R.; Wu, X.; Tang, Z.; Fan, H. On the photoelectron velocity-map imaging of lutetium monoxide anion LuO. J. Chem. Phys. 2014, 140, 034312, DOI: 10.1063/1.4862142
- 8Leger, J. M.; Yacoubi, N.; Loriers, J. Synthesis of rare earth monoxides. J. Solid State Chem. 1981, 36, 261– 270, DOI: 10.1016/0022-4596(81)90436-9[Crossref], [CAS], Google Scholar8https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL3MXitVWqs7c%253D&md5=50f4e7e137af9ded6298a4ae28d9156cSynthesis of rare earth monoxidesLeger, J. M.; Yacoubi, N.; Loriers, J.Journal of Solid State Chemistry (1981), 36 (3), 261-70CODEN: JSSCBI; ISSN:0022-4596.The std. Gibbs energy changes for the formation of an ionic or metallic monoxide from rare earth metal and its sesquioxide were calcd. Under high pressures ionic YbO and lighter rare earth metallic monoxides should be obtained, which is confirmed by expts. in a belt-type app. in the range 15-80 kbar and 500-1200°. For Ln = La, Ce, Pr, Nd, Sm, a fcc. compd. is obtained from each reaction. The cell parameters are resp. 5.144, 5.089, 5.031, 4.994, and 4.943 ± 0.005 Å. The compds. appear golden yellow with a metallic luster. From chem. analyses and cell parameter considerations these compds. are identified as the rare earth monoxides. For Ln = Gd, Dy, Tm, no reaction is obsd. at 50 kbar and 1000°. The rare earth monoxides show a variety of properties: LaO, CeO, PrO, and NdO are metallic with the rare earth in the trivalent state; EuO and YbO are semiconductors with the rare earth in the divalent state; SmO is metallic with Sm in an intermediate valence state close to 3.
- 9Kaminaga, K.; Sei, R.; Hayashi, K.; Happo, N.; Tajiri, H.; Oka, D.; Fukumura, T.; Hasegawa, T. A divalent rare earth oxide semiconductor: Yttrium monoxide. Appl. Phys. Lett. 2016, 108, 122102, DOI: 10.1063/1.4944330
- 10Uchida, Y.; Kaminaga, K.; Fukumura, T.; Hasegawa, T. Samarium monoxide epitaxial thin film as a possible heavy-fermion compound. Phys. Rev. B 2017, 95, 125111, DOI: 10.1103/physrevb.95.125111
- 11Kaminaga, K.; Oka, D.; Hasegawa, T.; Fukumura, T. Superconductivity of Rock-Salt Structure LaO Epitaxial Thin Film. J. Am. Chem. Soc. 2018, 140, 6754– 6757, DOI: 10.1021/jacs.8b03009[ACS Full Text], [CAS], Google Scholar11https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXpvVakurs%253D&md5=20a14f14942d5986d05cb78a0d2efb19Superconductivity of Rock-Salt Structure LaO Epitaxial Thin FilmKaminaga, Kenichi; Oka, Daichi; Hasegawa, Tetsuya; Fukumura, TomoteruJournal of the American Chemical Society (2018), 140 (22), 6754-6757CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The authors report a superconducting transition in a LaO epitaxial thin film with the superconducting transition onset temp. (Tc) at ∼5 K. This Tc is higher than those of other lanthanum monochalcogenides and opposite to their chem. trend: Tc = 0.84, 1.02, and 1.48 K for LaX (X = S, Se, Te), resp. The carrier control resulted in a dome-shaped Tc as a function of electron carrier d. The Tc was significantly sensitive to epitaxial strain in spite of the highly sym. crystal structure. This rock-salt superconducting LaO could be a building block to design novel superlattice superconductors.
- 12Stellhorn, J. R.; Hosokawa, S.; Happo, N.; Tajiri, H.; Matsushita, T.; Kaminaga, K.; Fukumura, T.; Hasegawa, T.; Hayashi, K. A valence-selective X-ray fluorescence holography study of an yttrium oxide thin film. J. Appl. Crystallogr. 2017, 50, 1583– 1589, DOI: 10.1107/s1600576717012821[Crossref], [CAS], Google Scholar12https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhvFahtLfF&md5=25474a007f86956809b58160e30ee0b4A valence-selective X-ray fluorescence holography study of an yttrium oxide thin filmStellhorn, J. R.; Hosokawa, S.; Happo, N.; Tajiri, H.; Matsushita, T.; Kaminaga, K.; Fukumura, T.; Hasegawa, T.; Hayashi, K.Journal of Applied Crystallography (2017), 50 (6), 1583-1589CODEN: JACGAR; ISSN:1600-5767. (International Union of Crystallography)The first direct valence-selective structure detn. by X-ray fluorescence holog. is reported. The method is applied to investigate an epitaxial thin film of the rare earth monoxide YO, which has recently been synthesized by pulsed laser deposition. The surface of the sample is easily oxidized to Y2O3. In order to sep. the structural information connected with the two different valence states of Y, the X-ray fluorescence holog. measurements were performed close to the Y K absorption edge. Using the shift of the absorption edge for the different valence states, very different relative contributions of YO and Y2O3 are obtained. Thus, it is possible to distinguish the crystal structures of YO and Y2O3 in the thin-film sample.
- 13Shannon, R. D. Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. Acta Crystallogr., Sect. A: Cryst. Phys., Diffr., Theor. Gen. Crystallogr. 1976, 32, 751– 767, DOI: 10.1107/s0567739476001551
- 14Jia, Y. Q. Crystal radii and effective ionic radii of the rare earth ions. J. Solid State Chem. 1991, 95, 184– 187, DOI: 10.1016/0022-4596(91)90388-x[Crossref], [CAS], Google Scholar14https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK3MXmvFWksr0%253D&md5=a41ad00fccb05a9ac413d01fb2deae88Crystal radii and effective ionic radii of the rare earth ionsJia, Y. Q.Journal of Solid State Chemistry (1991), 95 (1), 184-7CODEN: JSSCBI; ISSN:0022-4596.There exist some relations between the crystal radii of the rare earth ions, the 4f electron no., and the coordination no. On the basis of these relations, 2 empirical formulas are proposed to calc. the unknown crystal radii of the rare earth ions from the known crystal radii of the trivalent rare earth ions. The crystal radii and effective ionic radii of all the rare earth ions (trivalent and divalent) with different coordination no. (N = 6-12) were evaluated. The calcd. results are very satisfactory, and for most of examples the relative error is <1.0%.
- 15Cox, P. A. The Electronic Structure and Chemistry of Solids; Oxford University Press: New York, 1987.Google ScholarThere is no corresponding record for this reference.
- 16Kaichev, V. V.; Asanova, T. I.; Erenburg, S. B.; Perevalov, T. V.; Shvets, V. A.; Gritsenko, V. A. Atomic and electronic structures of lutetium oxide Lu2O3. J. Exp. Theor. Phys. 2013, 116, 323– 329, DOI: 10.1134/s1063776113020131[Crossref], [CAS], Google Scholar16https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXktVKjtrw%253D&md5=3ae61c2c5e4996d32b1ecefafc020813Atomic and electronic structures of lutetium oxide Lu2O3Kaichev, V. V.; Asanova, T. I.; Erenburg, S. B.; Perevalov, T. V.; Shvets, V. A.; Gritsenko, V. A.Journal of Experimental and Theoretical Physics (2013), 116 (2), 323-329CODEN: JTPHES; ISSN:1063-7761. (MAIK Nauka/Interperiodica)The chem. compn., electronic structure, structure, and phys. properties a Lu oxide Lu2O3 film were studied by XPS, ellipsometry, and x-ray absorption spectroscopy. The short-range order in Lu2O3 is found to correspond to its cubic modification. The binding energies of the 1s and 2p levels of O and the 4d5/2 and 4f7/2 levels of Lu are 529.2, 5.0 and 7.4, 195.9 eV, resp. The energy gap detd. from the electron energy loss spectrum of the film is 5.9 eV. The electron energy loss spectra have two peaks at 17.4 and 22.0 eV, which can be attributed to the excitation of bulk plasma oscillations. The dispersion of the refractive index is measured by spectral ellipsometry. The refractive index increases from 1.82 at 1.5 eV to 2.18 at 5.0 eV, and the high-frequency permittivity of Lu2O3 is 3.31.
- 17Yermolayeva, Y. V.; Tolmachev, A. V.; Korshikova, T. I.; Yavetskiy, R. P.; Dobrotvorskaya, M. V.; Danylenko, N. I.; Sofronov, D. S. Spherical core–shell structured nanophosphors on the basis of europium-doped lutetium compounds. Nanotechnology 2009, 20, 325601, DOI: 10.1088/0957-4484/20/32/325601
- 18Tanuma, S.; Powell, C. J.; Penn, D. R. Calculation of electron inelastic mean free paths (IMFPs) VII. Reliability of the TPP-2M IMFP predictive equation. Surf. Interface Anal. 2003, 35, 268– 275, DOI: 10.1002/sia.1526[Crossref], [CAS], Google Scholar18https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXisVegu70%253D&md5=35bbab150b6fce516cb82e97f24e525aCalculation of electron inelastic mean free paths (IMFPs) VII. Reliability of the TPP-2M IMFP predictive equationTanuma, S.; Powell, C. J.; Penn, D. R.Surface and Interface Analysis (2003), 35 (3), 268-275CODEN: SIANDQ; ISSN:0142-2421. (John Wiley & Sons Ltd.)The authors report comparisons of electron inelastic mean free paths (IMFPs) detd. from predictive IMFP equation TPP-2M and ref. IMFPs calcd. from optical data. These comparisons were made for values of the parameter Nv (the no. of valence electrons per atom or mol.) that the authors have recommended and those that were recommended in a recent paper by Seah et al. (Surf. Interface Anal. 2001; 31: 778). The comparisons were made for 8 elemental solids (K, Y, Gd, Tb, Dy, Hf, Ta and Bi) and 2 compds. (KBr and Y2O3) for which there were appreciable differences in the recommended Nv values from the 2 sources and for which optical data were available for the IMFP calcns. The av. of the root-mean-square deviations for the 10 materials between IMFPs from the TPP-2M equation with Nv values and the ref. IMFPs was 11.0%, whereas the corresponding av. with the Seah et al. Nv values was 20.2%. The larger av. in the latter comparison was mainly due to large (>20%) root-mean-square deviations for 4 materials (K, Hf, Ta and KBr). For the other 6 materials, the root-mean-square deviations with the Seah et al. values of Nv were similar to those with values of Nv. Based on the comparisons for these 10 materials, probably it is preferable to use values of Nv in the TPP-2M equation.
- 19Narayanamurti, V.; Jayaraman, A.; Bucher, E. Optical absorption in ytterbium monochalcogenides under pressure. Phys. Rev. B: Solid State 1974, 9, 2521– 2523, DOI: 10.1103/physrevb.9.2521[Crossref], [CAS], Google Scholar19https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaE2cXktVyjsrg%253D&md5=702b998b6aaaa5559744740bc1ef3821Optical absorption in ytterbium monochalcogenides under pressureNarayanamurti, V.; Jayaraman, A.; Bucher, E.Physical Review B: Solid State (1974), 9 (6), 2521-3CODEN: PLRBAQ; ISSN:0556-2805.The pressure dependence of the lowest-lying 4f → 5d absorption band in cryst. films of YbTe, YbSe, and YbS was studied. The absorption edge which occurs at ∼1.8 in YbTe, 1.5 in YbSe, and 1.1 eV in YbS at zero pressure closes at a rate of 11.0, 9.8, and 6.5 meV/kbar, resp., for pressures up to 8 kbar. The measurements predict gap collapses in all the 3 chalcogenides at pressures of ∼175 kbar, in good agreement with pressure-vol. studies and qual. changes in the reflectivity at high pressures.
- 20Ogasawara, H.; Kotani, A.; Thole, B. T. Lifetime effect on the multiplet structure of 4d x-ray-photoemission spectra in heavy rare-earth elements. Phys. Rev. B: Condens. Matter Mater. Phys. 1994, 50, 12332– 12341, DOI: 10.1103/physrevb.50.12332
- 21Kimura, T.; Otani, Y.; Sato, T.; Takahashi, S.; Maekawa, S. Room-temperature reversible spin Hall effect. Phys. Rev. Lett. 2007, 98, 156601, DOI: 10.1103/physrevlett.98.249901[Crossref], [PubMed], [CAS], Google Scholar21https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXkt1Grsr4%253D&md5=63cadea7ac51690ebae0c7d1c2413881Room-Temperature Reversible Spin Hall EffectKimura, T.; Otani, Y.; Sato, T.; Takahashi, S.; Maekawa, S.Physical Review Letters (2007), 98 (15), 156601/1-156601/4CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)Reversible spin Hall effect comprising the direct and inverse spin Hall effects was elec. detected at room temp. A platinum wire with a strong spin-orbit interaction is used not only as a spin current absorber but also as a spin-current source in the specially designed lateral structure. The obtained spin Hall conductivities are 2.4×104 (Ωm)-1 at room temp., 104 times larger than the previously reported values of semiconductor systems. Spin Hall conductivities obtained from both the direct and inverse spin Hall effects are exptl. confirmed to be the same, demonstrating the Onsager reciprocal relations between spin and charge currents.
- 22Fujiwara, K.; Fukuma, Y.; Matsuno, J.; Idzuchi, H.; Niimi, Y.; Otani, Y.; Takagi, H. 5d iridium oxide as a material for spin-current detection. Nat. Commun. 2013, 4, 2893, DOI: 10.1038/ncomms3893[Crossref], [PubMed], [CAS], Google Scholar22https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BC2c3lsVyqtA%253D%253D&md5=3a65a3f9d27c6b482e066c38e61594115d iridium oxide as a material for spin-current detectionFujiwara Kohei; Fukuma Yasuhiro; Matsuno Jobu; Idzuchi Hiroshi; Niimi Yasuhiro; Otani Yoshichika; Takagi HidenoriNature communications (2013), 4 (), 2893 ISSN:.Devices based on pure spin currents have been attracting increasing attention as key ingredients for low-dissipation electronics. To integrate such spintronics devices into charge-based technologies, electric detection of spin currents is essential. The inverse spin Hall effect converts a spin current into an electric voltage through spin-orbit coupling. Noble metals such as Pt and Pd, and also Cu-based alloys, have been regarded as potential materials for a spin-current injector, owing to the large direct spin Hall effect. Their spin Hall resistivity ρSH, representing the performance as a detector, is not large enough, however, due mainly because of their low charge resistivity. Here we report that a binary 5d transition metal oxide, iridium oxide, overcomes the limitations encountered in noble metals and Cu-based alloys and shows a very large ρSH~38 μΩ cm at room temperature.
- 23Momma, K.; Izumi, F. VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data. J. Appl. Crystallogr. 2011, 44, 1272– 1276, DOI: 10.1107/s0021889811038970[Crossref], [CAS], Google Scholar23https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhsFSisrvP&md5=885fbd9420ed18838813d6b0166f4278VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology dataMomma, Koichi; Izumi, FujioJournal of Applied Crystallography (2011), 44 (6), 1272-1276CODEN: JACGAR; ISSN:0021-8898. (International Union of Crystallography)VESTA is a 3D visualization system for crystallog. studies and electronic state calcns. It was upgraded to the latest version, VESTA 3, implementing new features including drawing the external morphpol. of crysals; superimposing multiple structural models, volumetric data and crystal faces; calcn. of electron and nuclear densities from structure parameters; calcn. of Patterson functions from the structure parameters or volumetric data; integration of electron and nuclear densities by Voronoi tessellation; visualization of isosurfaces with multiple levels, detn. of the best plane for selected atoms; an extended bond-search algorithm to enable more sophisticated searches in complex mols. and cage-like structures; undo and redo is graphical user interface operations; and significant performance improvements in rendering isosurfaces and calcg. slices.
Supporting Information
Supporting Information
ARTICLE SECTIONSThe Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsomega.8b02082.
PDF data, discussion of quantitative analysis of the LuO thin film, and typical XPS spectrum for the LuO(001) epitaxial thin film (PDF)
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.