ZnO Grown by Metal Organic Chemical Vapor Deposition: Effect of Substrate on Optical and Structural Properties

Abstract

This paper reports the effects of the following substrates on the optical, structural and morphological properties of ZnO thin films: Si (100), Si (111), c- and r-sapphire, glass, GaAs and ZnO. The thin films were deposited by low pressure Metal Organic Chemical Vapor Deposition using diethylzinc and tertiary butanol as the zinc and oxygen sources, respectively. X-ray diffraction analysis shows that all the ZnO layers are c-axis orientated. Scanning Electron microscopy reveals similar morphology for all the substrates used, with hexagonal columns having cone shape ends being evident. The photoluminescence spectra are similar, but the various transitions have different relative intensities. It is clear that the different substrates influence neither the orientation of the films, nor the surface morphology, significantly. The photoluminescence hints at larger stacking fault densities in films grown on silicon and glass, however, as evidenced by stronger basal plane stacking fault-related luminescence at ~3.319 eV in the relevant low temperature photoluminescence spectra.