Fabrication And Physical Characterisation Of Zinc Oxide Thin Films
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Date
2012-03
Authors
Lim, Yam Tee
Journal Title
Journal ISSN
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Publisher
Universiti Sains Malaysia
Abstract
Zinc oxide (ZnO) thin films were deposited on α-0001 sapphire substrates using direct current (d.c.) magnetron sputtering process and annealed at various temperatures in an inert atmosphere to investigate its effect on the ultraviolet (UV) emission, stress, lattice constants, crystallite size as well as the possibility of inducing nanostructure growth. Scanning electron microscope (SEM) and X-ray diffraction (XRD) found that ZnO thin films have a fairly uniform granular surface structure with a preferential c-axis growth direction. The reduction of the E1(LO) peak of Raman spectrum, the shift in the UV peak position as well as the significant increase in the intensity of the UV peak after annealing indicated that the annealing process helped to reduce the defects in the sputtered ZnO thin films. Evidence from Raman and XRD analyses showed a decrease in stress and the lattice constant values. The crystallite size calculated using the Scherrer equation increased after annealing. Evidence from Raman and photoluminescence spectroscopy as well as XRD thus suggests that the quality of ZnO thin films increases as a result of annealing. Nanorods and tetrapods were observed on the thin films annealed at 800oC. The different sizes and different stages of the nanostructures indicate that growth occurs throughout the annealing process and not only at its onset. The nanostructures were found to grow directly from the ZnO crystallites. A possible cause for inducing the growth of nanostructures is that the sputtered ZnO thin films are zinc-rich as indicated by Raman spectroscopy.
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Keywords
Fabrication and physical characterisation , of zinc oxide thin films