Post annealing effect on structural and optical properties of ZnO thin films derived by sol–gel route
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Zinc oxide thin films have been spun coated on p-Si (100) substrates by sol–gel route. These films were annealed at different annealing temperatures from 300 to 1,000 °C in the oxygen ambient. In this way a suitable annealing temperature window for the sol–gel derived ZnO films exhibiting minimum defects (points and dislocations) and better quality (crystal and optical) was investigated. The structural and optical features of ZnO thin films have been examined by X-ray diffraction, atomic force microscopy, UV–Vis spectroscopy, and photoluminescence spectra. The results revealed that the crystallization in the films initiated at 300 °C, improved further with annealing. All the deposited films exhibited wurtzite phase with c-axis orientations. The variations in the position of characteristic (002) peak, stress, strain and lattice parameters are investigated as a function of annealing temperature. The optical band gap is not significantly affected with annealing as observed by UV–Vis transmission spectroscopy. The Photoluminescence spectra exhibited three luminescence centers. The near band edge esmission was observed in UV region which enhanced with the heat treatment, is an indication of improvement in the optical quality of films. The other two visible emissions are related to native defects in ZnO lattice were appeared only for higher annealing (≥700 °C).
KeywordsScrew Dislocation Hall Mobility Post Annealing Near Band Edge Emission Post Annealing Temperature
The authors wish to thank all the members of Hybrid Microcircuits group, CEERI, Pilani and Department of Electronic Science, K.U.K. for their technical support. The authors are extremely thankful to Dr. Chandra Shekhar, Director, CEERI, Pilani for his permission to utilize the facilities in his institution. One of authors Amanpal Singh is also thankful to Council of Scientific and Industrial Research (CSIR), India for award of senior research fellowship. This work was financially supported by the Department of Science and Technology, Ministry of Science, India, under the project number SR/S3/EECE/043/2007.
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