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Title: Achieving highly-enhanced UV photoluminescence and its origin in ZnO nanocrystalline films

Abstract

ZnO is an efficient luminescent material in the UV-range ~3.4 eV with a wide range of applications in optical technologies. Sputtering is a cost-effective and relatively straightforward growth technique for ZnO films; however, most as-grown films are observed to contain intrinsic defects which can significantly diminish the desirable UV-emission. In this research the defect dynamics and optical properties of ZnO sputtered films were studied via post-growth annealing in Ar or O 2 ambient, with X-ray diffraction (XRD), imaging, transmission and Urbach analysis, Raman scattering, and photoluminescence (PL). The imaging, XRD, Raman and Urbach analyses indicate significant improvement in crystal morphology and band-edge characteristics upon annealing, which is nearly independent of the annealing environment. The native defects specific to the as-grown films, which were analyzed via PL, are assigned to Zn i related centers that luminesce at 2.8 eV. Their presence is attributed to the nature of the sputtering growth technique, which supports Zn-rich growth conditions. After annealing, in either environment the 2.8 eV center diminished accompanied by morphology improvement, and the desirable UV-PL significantly increased. The O 2 ambient was found to introduce nominal O i centers while the Ar ambient was found to be the ideal environment for themore » enhancement of the UV-light emission: an enhancement of ~40 times was achieved. The increase in the UV-PL is attributed to the reduction of Zn i-related defects, the presence of which in ZnO provides a competing route to the UV emission. Also, the effect of the annealing was to decrease the compressive stress in the films. Lastly, the dominant UV-PL at the cold temperature regime is attributed to luminescent centers not associated with the usual excitons of ZnO, but rather to structural defects.« less

Authors:
 [1];  [1];  [2];  [3];  [3];  [1]
  1. Univ. of Idaho, Moscow, ID (United States)
  2. Lewis-Clark State College, Lewiston, ID (United States)
  3. Washington State Univ., Pullman, WA (United States)
Publication Date:
Research Org.:
Washington State Univ., Pullman, WA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1257289
Alternate Identifier(s):
OSTI ID: 1434897
Grant/Contract Number:  
FG02-07ER46386
Resource Type:
Journal Article: Published Article
Journal Name:
Optical Materials
Additional Journal Information:
Journal Volume: 58; Journal Issue: C; Journal ID: ISSN 0925-3467
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY; ZnOUV-photoluminescence; DC-sputtering; Raman; Native defects; Annealing

Citation Formats

Thapa, Dinesh, Huso, Jesse, Morrison, John L., Corolewski, Caleb D., McCluskey, Matthew D., and Bergman, Leah. Achieving highly-enhanced UV photoluminescence and its origin in ZnO nanocrystalline films. United States: N. p., 2016. Web. doi:10.1016/j.optmat.2016.05.008.
Thapa, Dinesh, Huso, Jesse, Morrison, John L., Corolewski, Caleb D., McCluskey, Matthew D., & Bergman, Leah. Achieving highly-enhanced UV photoluminescence and its origin in ZnO nanocrystalline films. United States. doi:10.1016/j.optmat.2016.05.008.
Thapa, Dinesh, Huso, Jesse, Morrison, John L., Corolewski, Caleb D., McCluskey, Matthew D., and Bergman, Leah. Tue . "Achieving highly-enhanced UV photoluminescence and its origin in ZnO nanocrystalline films". United States. doi:10.1016/j.optmat.2016.05.008.
@article{osti_1257289,
title = {Achieving highly-enhanced UV photoluminescence and its origin in ZnO nanocrystalline films},
author = {Thapa, Dinesh and Huso, Jesse and Morrison, John L. and Corolewski, Caleb D. and McCluskey, Matthew D. and Bergman, Leah},
abstractNote = {ZnO is an efficient luminescent material in the UV-range ~3.4 eV with a wide range of applications in optical technologies. Sputtering is a cost-effective and relatively straightforward growth technique for ZnO films; however, most as-grown films are observed to contain intrinsic defects which can significantly diminish the desirable UV-emission. In this research the defect dynamics and optical properties of ZnO sputtered films were studied via post-growth annealing in Ar or O2 ambient, with X-ray diffraction (XRD), imaging, transmission and Urbach analysis, Raman scattering, and photoluminescence (PL). The imaging, XRD, Raman and Urbach analyses indicate significant improvement in crystal morphology and band-edge characteristics upon annealing, which is nearly independent of the annealing environment. The native defects specific to the as-grown films, which were analyzed via PL, are assigned to Zni related centers that luminesce at 2.8 eV. Their presence is attributed to the nature of the sputtering growth technique, which supports Zn-rich growth conditions. After annealing, in either environment the 2.8 eV center diminished accompanied by morphology improvement, and the desirable UV-PL significantly increased. The O2 ambient was found to introduce nominal Oi centers while the Ar ambient was found to be the ideal environment for the enhancement of the UV-light emission: an enhancement of ~40 times was achieved. The increase in the UV-PL is attributed to the reduction of Zni-related defects, the presence of which in ZnO provides a competing route to the UV emission. Also, the effect of the annealing was to decrease the compressive stress in the films. Lastly, the dominant UV-PL at the cold temperature regime is attributed to luminescent centers not associated with the usual excitons of ZnO, but rather to structural defects.},
doi = {10.1016/j.optmat.2016.05.008},
journal = {Optical Materials},
number = C,
volume = 58,
place = {United States},
year = {Tue Jun 14 00:00:00 EDT 2016},
month = {Tue Jun 14 00:00:00 EDT 2016}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.optmat.2016.05.008

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Cited by: 7 works
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