Enhanced near-band edge emission in pulsed laser deposited ZnO/c-sapphire nanocrystalline thin films
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We report on the enhanced near-band edge emission with negligible defect-assisted emission in ZnO nanocrystalline thin films of varying thickness on c-sapphire substrates. X-ray diffraction studies reveal wurtzite structure of thin films grown preferentially along (002) plane. The crystallinity and grain size of the deposited films have been increased with increase in film thickness. The band gap of the films was calculated by Tauc’s plot which shows negligible change in band gap with increase in thickness of ZnO film. The various Raman modes observed in ZnO thin films of different thicknesses support the formation of hexagonal wurtzite structure. The room temperature photoluminescence (PL) spectrum shows the strong near-band edge emission in the wavelength range 378–381 nm which further enhances with film thickness. The enhanced PL emission in near ultraviolet visible (UV) region with negligible defect-assisted emission may find potential applications in ZnO-based UV-excited light-emitting diodes.
Authors are grateful to the Head, Centre for Material Science and Engineering, National Institute of Technology, Hamirpur (H.P) for providing experimental facilities to carry out this work. The authors are highly thankful prof. M. K. Banerjee Department of Metallurgical & Materials Engineering, Malaviya National Institute of Technology Jaipur for their valuable suggestions. The authors also acknowledge the funds provided by UGC-DAE Consortium Scientific Research (CSR-IC-BL-74/CRS-191/2016-17/855), India in terms of a research project.
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