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Photoluminescence and excitonic absorption of ZnO/SiO2 multilayer thin films under various annealing temperatures

LINHUA XU1,2,* , SHAORONG XIAO1,2, CHENGYI ZHANG1,2, GAIGE ZHENG1,2, WEIFENG RAO1, FENGLIN XIAN3, JUHONG MIAO1, HONGYAN WU1, ZHANHUI LIU1

Affiliation

  1. School of Physics and Optoelectronic Engineering, Nanjing University of Information Science & Technology, Nanjing 210044, China
  2. Optics and Photonic Technology Laboratory, Nanjing University of Information Science & Technology, Nanjing 210044, China
  3. Department of Applied Physics, Nanjing University of Science and Technology, Nanjing 210094, China

Abstract

SiO2 has an important regulation effect on the luminescence of ZnO nanomaterials. In this study, the ZnO/SiO2 multilayer thin films were prepared by electron beam evaporation and the influence of various annealing temperatures on optical properties of the samples was investigated. The X-ray diffraction (XRD) patterns show that all the samples exhibit a (002) peak of wurtzite ZnO. With the increase of annealing temperature, the intensity of the (002) peak is increased and its full width at half maximum (FWHM) is decreased, which means the crystalline quality of ZnO is gradually improved. Compared with the pure ZnO thin films with the same annealing temperatures, the ZnO/SiO2 multilayer thin films have much smoother surfaces. The absorption spectra display that the excitonic peak is more obvious and the absorption edge becomes much sharper and steeper after annealing treatments. This suggests that the defect density in ZnO layers is reduced. With the rise of annealing temperature, the ultraviolet emission of ZnO is evidently enhanced, which can be attributed to the increased density of free excitons. On the other hand, the ultraviolet emission peak has a slight blue-shift with the increasing annealing temperature, which is probably connected with the improvement of the crystalline quality and the decrease of defect density in ZnO grains..

Keywords

ZnO/SiO2 multilayer thin films, Annealing temperature, Transmittance, Excitonic absorption, Photoluminescence.

Submitted at: Aug. 20, 2013
Accepted at: Nov. 13, 2014

Citation

LINHUA XU, SHAORONG XIAO, CHENGYI ZHANG, GAIGE ZHENG, WEIFENG RAO, FENGLIN XIAN, JUHONG MIAO, HONGYAN WU, ZHANHUI LIU, Photoluminescence and excitonic absorption of ZnO/SiO2 multilayer thin films under various annealing temperatures, Journal of Optoelectronics and Advanced Materials Vol. 16, Iss. 11-12, pp. 1285-1289 (2014)