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Journal of Nanomaterials
Volume 2015 (2015), Article ID 970545, 11 pages
http://dx.doi.org/10.1155/2015/970545
Research Article

The Role of Edge Dislocations on the Red Luminescence of ZnO Films Deposited by RF-Sputtering

1Department of Materials Science and Metallurgical Engineering and Inorganic Chemistry, University of Cádiz, Puerto Real, 11510 Cádiz, Spain
2Institute of Research on Electron Microscopy and Materials of the University of Cádiz (IMEYMAT), Puerto Real, 11510 Cádiz, Spain
3Department of Physic and I3N, University of Aveiro, Campus of Santiago, 3810-193 Aveiro, Portugal
4Department of Physics, CICECO, University of Aveiro, 3810-193 Aveiro, Portugal
5Instituto Superior Técnico (IST), Campus Tecnológico e Nuclear, Estrada Nacional 10, Bobadela, 2695-066 Loures, Portugal

Received 28 July 2015; Accepted 8 November 2015

Academic Editor: Run-Wei Li

Copyright © 2015 Rocío Félix et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The existence of extended defects (i.e., dislocations) in inorganic semiconductors, such as GaN or ZnO, responsible for broad emission peaks in photoluminescence analysis remains unresolved. The possible assignments of these luminescence bands are still matter of discussion. In this study, two different zinc oxide samples, grown under different oxygen partial pressures and substrate temperatures, are presented. Epitaxial and structural properties were analysed by means of X-ray diffraction and transmission electron microscopy techniques. They confirm that the layers are single-phase with a good crystalline quality. Nevertheless, a different density of threading dislocations, with a higher contribution of edge dislocations, was found. Photoluminescence spectroscopy has been used to investigate the optical properties. The steady state luminescence spectra performed at 14 K evidenced the donor bound exciton recombination and deep green and red emission bands. The red band with a maximum at 1.78 eV was found to be stronger in the sample grown at lower oxygen pressure which also shows higher density of threading dislocations. From the temperature and excitation density dependence of the red band, a donor acceptor pair recombination model was proposed, where hydrogen and zinc vacancies are strong candidates for the donor and acceptor species, respectively.