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Journal of Spectroscopy
Volume 2013 (2013), Article ID 797232, 7 pages
http://dx.doi.org/10.1155/2013/797232
Research Article

Study of Ultraviolet Emission Spectra in ZnO Thin Films

1Shenzhen Key Laboratory of Special Functional Materials, College of Materials Science and Engineering, Shenzhen University, Shenzhen 518060, China
2Institute of Optoelectronic Materials and Technology, South China Normal University, Guangzhou 510631, China

Received 7 June 2012; Accepted 21 August 2012

Academic Editor: Vincenza Crupi

Copyright © 2013 Y. M. Lu 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

Photoluminescence (PL) of ZnO thin films prepared on c-Al2O3 substrates by pulsed laser deposition (PLD) are investigated. For all samples, roomtemperature (RT) spectra show a strong band-edge ultraviolet (UV) emission with a pronounced low-energy band tail. The origin of this UV emission is analyzed by the temperature dependence of PL spectra. The result shows that the UV emission at RT contains different recombination processes. At low temperature donor-bound exciton (D0X) emission plays a major role in PL spectra, while the free exciton transition (FX) gradually dominates the spectrum with increasing temperatures. It notes that at low temperature an emission band (FA) appears in low energy side of D0X and FX and can survive up to RT. Further confirmation shows that the origin of the band FA can be attributed to the transitions of conduction band electrons to acceptors (e, A0), in which the acceptor binding energy is estimated to be approximately 121 meV. It is concluded that at room temperature UV emission originates from the corporate contributions of the free exciton and free electrons-to-acceptor transitions.