Atomic Layer Deposition of Lead Sulfide Thin Films for Quantum Confinement

Neil P. Dasgupta*, Wonyoung Lee and Fritz B. Prinz
† Department of Mechanical Engineering
‡ Department of Materials Science and Engineering
Stanford University, California 94305
Chem. Mater., 2009, 21 (17), pp 3973–3978
DOI: 10.1021/cm901228x
Publication Date (Web): August 11, 2009
Copyright © 2009 American Chemical Society
*Corresponding author. E-mail: dasgupta@stanford.edu. Phone: (773) 497-9532. Fax: (650) 723-5034.

Abstract

Abstract Image

Lead sulfide (PbS) thin films were deposited by atomic layer deposition (ALD) for the fabrication of quantum well structures. A linear growth rate of 0.9 Å/cycle and pulse saturation behavior characteristic of ALD were observed. The stoichiometry of the films was confirmed using X-ray photoelectron spectroscopy (XPS) with no chemical contamination. The polycrystalline film morphology was observed with grain sizes ranging from 30 to 150 nm. Size quantization effects are shown on the bandgap by fabricating PbS quantum wells with a sub-10 nm thickness. Bandgap values were measured by tunneling spectroscopy (TS) using scanning tunneling microscopy (STM) and are matched to an effective mass model. The bandgap of the films was changed from 0.4 to 2.75 eV by varying only the number of ALD cycles.

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History

  • Published In Issue September 08, 2009
  • Article ASAPAugust 11, 2009
  • Received: May 04, 2009
    Revised: June 23, 2009

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