skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Effects of low-temperature-buffer, rf-power, and annealing on structural and optical properties of ZnO/Al{sub 2}O{sub 3}(0001) thin films grown by rf-magnetron sputtering

Abstract

ZnO thin films were epitaxially grown on Al{sub 2}O{sub 3} (0001) substrates in a radio-frequency (rf) magnetron sputtering chamber. The surface morphology of ZnO was remarkably affected by the incorporation of a low-temperature grown ZnO buffer as well as the changes in rf-power. X-ray diffractions, combined with the surface micropits, revealed strain relaxations in the ZnO epilayers grown with higher rf-powers, which in turn caused a redshift to the intrinsic exciton absorption peak. Strain relaxations were also observed in the ZnO epilayers upon thermal annealing, which led to a redshift in the E{sub 2}{sup high} Raman mode. A factor of approx0.7 cm{sup -1} GPa{sup -1}, i.e., a biaxial stress of 1 GPa can shift the E{sub 2}{sup high} mode by 0.7 cm{sup -1}, was obtained. The point defects related absorptions and the exciton localizations were suppressed by annealing, which, in conjunction with the strain-relaxation induced redshift in the intrinsic-exciton absorptions, steepened the absorption edge and increased the optical bandgap energy of the ZnO epilayer.

Authors:
;  [1]
  1. Institute of Materials Research and Engineering (IMRE), A-STAR (Agency for Science, Technology and Research), 3 Research Link, Singapore 117602 (Singapore)
Publication Date:
OSTI Identifier:
21359321
Resource Type:
Journal Article
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 106; Journal Issue: 2; Other Information: DOI: 10.1063/1.3176497; (c) 2009 American Institute of Physics; Journal ID: ISSN 0021-8979
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ABSORPTION; ALUMINIUM OXIDES; ANNEALING; CRYSTAL GROWTH; DEPOSITION; ENERGY GAP; EPITAXY; EXCITONS; MORPHOLOGY; OPTICAL PROPERTIES; POINT DEFECTS; PRESSURE RANGE GIGA PA; RADIOWAVE RADIATION; RAMAN SPECTRA; RED SHIFT; SEMICONDUCTOR MATERIALS; SPUTTERING; THIN FILMS; X-RAY DIFFRACTION; ZINC OXIDES; ALUMINIUM COMPOUNDS; CHALCOGENIDES; COHERENT SCATTERING; CRYSTAL DEFECTS; CRYSTAL GROWTH METHODS; CRYSTAL STRUCTURE; DIFFRACTION; ELECTROMAGNETIC RADIATION; FILMS; HEAT TREATMENTS; MATERIALS; OXIDES; OXYGEN COMPOUNDS; PHYSICAL PROPERTIES; PRESSURE RANGE; QUASI PARTICLES; RADIATIONS; SCATTERING; SORPTION; SPECTRA; ZINC COMPOUNDS

Citation Formats

Liu, H. F., and Chua, S. J. Effects of low-temperature-buffer, rf-power, and annealing on structural and optical properties of ZnO/Al{sub 2}O{sub 3}(0001) thin films grown by rf-magnetron sputtering. United States: N. p., 2009. Web. doi:10.1063/1.3176497.
Liu, H. F., & Chua, S. J. Effects of low-temperature-buffer, rf-power, and annealing on structural and optical properties of ZnO/Al{sub 2}O{sub 3}(0001) thin films grown by rf-magnetron sputtering. United States. doi:10.1063/1.3176497.
Liu, H. F., and Chua, S. J. Wed . "Effects of low-temperature-buffer, rf-power, and annealing on structural and optical properties of ZnO/Al{sub 2}O{sub 3}(0001) thin films grown by rf-magnetron sputtering". United States. doi:10.1063/1.3176497.
@article{osti_21359321,
title = {Effects of low-temperature-buffer, rf-power, and annealing on structural and optical properties of ZnO/Al{sub 2}O{sub 3}(0001) thin films grown by rf-magnetron sputtering},
author = {Liu, H. F. and Chua, S. J.},
abstractNote = {ZnO thin films were epitaxially grown on Al{sub 2}O{sub 3} (0001) substrates in a radio-frequency (rf) magnetron sputtering chamber. The surface morphology of ZnO was remarkably affected by the incorporation of a low-temperature grown ZnO buffer as well as the changes in rf-power. X-ray diffractions, combined with the surface micropits, revealed strain relaxations in the ZnO epilayers grown with higher rf-powers, which in turn caused a redshift to the intrinsic exciton absorption peak. Strain relaxations were also observed in the ZnO epilayers upon thermal annealing, which led to a redshift in the E{sub 2}{sup high} Raman mode. A factor of approx0.7 cm{sup -1} GPa{sup -1}, i.e., a biaxial stress of 1 GPa can shift the E{sub 2}{sup high} mode by 0.7 cm{sup -1}, was obtained. The point defects related absorptions and the exciton localizations were suppressed by annealing, which, in conjunction with the strain-relaxation induced redshift in the intrinsic-exciton absorptions, steepened the absorption edge and increased the optical bandgap energy of the ZnO epilayer.},
doi = {10.1063/1.3176497},
journal = {Journal of Applied Physics},
issn = {0021-8979},
number = 2,
volume = 106,
place = {United States},
year = {2009},
month = {7}
}