Abstract

Zinc oxide (ZnO) is a well-studied wide band gap (~3.37 eV) n-type semiconductor material with significant properties such as large exciton binding energy (60 meV). Recently, 1-dimensional ZnO nanostructures have attracted a lot of attention owing to their dimensionality-dependent chemical, physical, electrical, and magnetic properties. In this project, we have grown patterned low-aspect-ratio, well-separated single ZnO nanorods using a hydrothermal method on two different substrates with dissimilar crystal orientations. ZnO nuclei have been used as a seed layer to compensate the crystal mismatch between the substrates and nanorods. Based on XRD results, in order to have highly oriented nanorods, the seed layer must be annealed over 300 ̊ C. Micro-Raman spectra show that our patterned nanorods have a wurtzite crystal structure, with most nanorods presenting vertical orientation relative to the substrate. Room-temperature micro-photoluminescence spectra from the nanorods show sharp band edge emission at 385 nm and a common broadband defect emission in the visible range. This method is a significant step towards an economical controlled synthesis of 1-dimensional ZnO for application in mass-production advanced devices. In the second part, undoped and C-doped (C: Mg, Ni, Mn, Co, Cu, Cr, Na) ZnO nanorods were synthesized by a hydrothermal method at temperatures as low as 60 ̊C. The effect of doping on morphology of the ZnO nanorods was visualized by taking their cross section and top SEM images. The crystallinity change of the ZnO nanorods due to each cationic dopant was thoroughly investigated according to their XRD patterns. The optical Raman active modes of undoped and cation-doped nanorods were measured with a micro-Raman set up at room temperature. The surface chemistry of undoped and doped ZnO nanorods were investigated by X-ray photoelectron spectroscopy and Energy-dispersive X-ray spectroscopy. Finally, the band gap shift and defect emission of undoped and doped nanorods were measured by a photoluminescence set up at room temperature. Our results can be used as a comprehensive reference regarding the engineering of the morphological, structural and optical properties of ZnO nanorods by using a low temperature doping synthesis as an economical mass production approach.