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Title: Optical absorption edge of ZnO thin films: The effect of substrate

Abstract

The optical absorption edge and the near-absorption edge characteristics of undoped ZnO films grown by laser ablation on various substrates have been investigated. The band edge of films on C [(0001)] and R-plane [(1102)] sapphire, 3.29 and 3.32 eV, respectively, are found to be very close to the single crystal value of ZnO (3.3 eV) with the differences being accounted for in terms of the thermal mismatch strain using the known deformation potentials of ZnO. In contrast, films grown on fused silica consistently exhibit a band edge {approximately}0.1eV lower than that predicted using the known deformation potential and the thermal mismatch strains. This behavior is attributed to the small grain size (50 nm) realized in these films and the effect of electrostatic potentials that exist at the grain boundaries. Additionally, the spread in the tail (E{sub 0}) of the band edge for the different films is found to be very sensitive to the defect structure in the films. For films grown on sapphire substrates, values of E{sub 0} as low as 30 meV can be achieved on annealing in air, whereas films on fused silica always show a value {gt}100meV. We attribute this difference to the substantially higher density ofmore » high-angle grain boundaries in the films on fused silica. {copyright} {ital 1997 American Institute of Physics.}« less

Authors:
;  [1]
  1. Materials Department, College of Engineering, University of California, Santa Barbara, California 93106-5050 (United States)
Publication Date:
OSTI Identifier:
496661
DOE Contract Number:  
FG03-91ER45447
Resource Type:
Journal Article
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 81; Journal Issue: 9; Other Information: PBD: May 1997
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ZINC OXIDES; ABSORPTION SPECTRA; ZINC COMPOUNDS; THERMAL STRESSES; GRAIN SIZE; ANNEALING; THIN FILMS; STRAINS; GRAIN BOUNDARIES; POTENTIALS; SUBSTRATES; ABLATION; LASER RADIATION

Citation Formats

Srikant, V, and Clarke, D R. Optical absorption edge of ZnO thin films: The effect of substrate. United States: N. p., 1997. Web. doi:10.1063/1.364393.
Srikant, V, & Clarke, D R. Optical absorption edge of ZnO thin films: The effect of substrate. United States. https://doi.org/10.1063/1.364393
Srikant, V, and Clarke, D R. 1997. "Optical absorption edge of ZnO thin films: The effect of substrate". United States. https://doi.org/10.1063/1.364393.
@article{osti_496661,
title = {Optical absorption edge of ZnO thin films: The effect of substrate},
author = {Srikant, V and Clarke, D R},
abstractNote = {The optical absorption edge and the near-absorption edge characteristics of undoped ZnO films grown by laser ablation on various substrates have been investigated. The band edge of films on C [(0001)] and R-plane [(1102)] sapphire, 3.29 and 3.32 eV, respectively, are found to be very close to the single crystal value of ZnO (3.3 eV) with the differences being accounted for in terms of the thermal mismatch strain using the known deformation potentials of ZnO. In contrast, films grown on fused silica consistently exhibit a band edge {approximately}0.1eV lower than that predicted using the known deformation potential and the thermal mismatch strains. This behavior is attributed to the small grain size (50 nm) realized in these films and the effect of electrostatic potentials that exist at the grain boundaries. Additionally, the spread in the tail (E{sub 0}) of the band edge for the different films is found to be very sensitive to the defect structure in the films. For films grown on sapphire substrates, values of E{sub 0} as low as 30 meV can be achieved on annealing in air, whereas films on fused silica always show a value {gt}100meV. We attribute this difference to the substantially higher density of high-angle grain boundaries in the films on fused silica. {copyright} {ital 1997 American Institute of Physics.}},
doi = {10.1063/1.364393},
url = {https://www.osti.gov/biblio/496661}, journal = {Journal of Applied Physics},
number = 9,
volume = 81,
place = {United States},
year = {Thu May 01 00:00:00 EDT 1997},
month = {Thu May 01 00:00:00 EDT 1997}
}