Synthesis and Characterization of c -Axis Oriented Zinc Oxide Thin Film and Its Use for the Subsequent Hydrothermal Grow
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.65
Synthesis and Characterization of c-Axis Oriented Zinc Oxide Thin Film and Its Use for the Subsequent Hydrothermal Growth of Zinc Oxide Nanorods S.F.U. Farhad,1* N.I. Tanvir,1 M.S. Bashar2, and M. Sultana2 1 Solar Energy Conversion and Storage Research Section, Industrial Physics Division, BCSIR Labs, Dhaka 1205
2 Institute of Fuel Research and Development (IFRD), Dhaka 1205, Bangladesh Council of Scientific and Industrial Research (BCSIR), Bangladesh
*
E-mail: [email protected] / Phone: (0088) 01881755767
ABSTRACT
Oriented ZnO seed layers were deposited by three different techniques, namely, simple drop casting (DC), sol-gel derived dip coating (DPC) and spin coating of ball-milled ZnO powder solution(BMD) for the subsequent growth of vertically aligned ZnO nanorods along the substrate normal. X-ray diffraction (XRD) analyses revealed that ZnO(DC) seed layer exhibit the highest preferential c-axis texturing among the ZnO seed layers synthesized by different techniques. The Scanning Electron Microscopy (SEM) analysis evident that the morphology of ZnO seed layer surface is compact and coherently carpets the underlying substrate. ZnO nanorods(NRs) were then grown by hydrothermal method atop the ZnO seeded and nonseeded substrates grown by different techniques to elucidate the best ZnO seed layer promoting well-aligned ZnO Nanorods. The presence of c-axis oriented ZnO(DC) seeding layers was found to significantly affect the surface morphology and crystallographic orientation of the resultant ZnO NRs films. The optical band gap of ZnO(DC) seed and ZnO NRs were estimated to be 3.30 eV and in the range of 3.18 – 3.25 eV respectively by using UV-VIS-NIR diffuse reflection spectroscopy. The room temperature photoluminescence analyses revealed that nanostructured ZnO films exhibit a sharp near-band-edge luminescence peak at ~380 nm consistent with the estimated optical band gap and the ZnO nanorod arrays are notably free from defect-related green-yellow emission peaks.
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INTRODUCTION Zinc Oxide (ZnO) is one of the most promising II - VI group semiconductors generally crystallizes in the thermodynamically most stable hexagonal wurtzite structure. ZnO naturally exhibits n-type conductivity due to the formation of oxygen vacancies in the crystal lattice and has a wide direct band gap of 3.37 eV at room temperature [1-3]. Furthermore, ZnO is an environmentally benign, chemically stable and mechanically robust material and can be grown by number of deposition techniques [2, 4]. These intriguing properties together with wide range of multi-functionalities make ZnO material a potential candidate for a wide variety of applications [1, 2]. Recently, nano scale single crystalline ZnO materials such as nanorods (NRs)
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