Abstract
Morphological evolution in ZnO nanostructures has been observed by varying the temperature and pretreatment step on silicon substrate. The ZnO nanostructures were grown by the thermal evaporation of high-purity metallic zinc powder in the presence of oxygen without the use of any catalyst or additives. The local substrate temperature, pretreatment step, and distance of the substrate from the source material showed a great effect on the morphologies of the deposited structures. Therefore, specific structures were obtained at specific temperature zones at particular distances from the source material with or without pretreatment step. Detailed structural investigations demonstrated that the deposited nanostructures are single crystalline with the wurtzite hexagonal phase. Raman-scattering and room-temperature photoluminescence spectra reflect the high purity and almost defect free quality with good optical properties for all the as-grown products.