Effect of Laser Irradiation on the Properties of ZnO Buffer Layers and Its Application to Selective-Growth of ZnO Nano/Microcrystals

摘要

ZnO nanocrystals, which are characterized by their configurations and fine structures, are unique oxide semiconductors. They are synthesized by nanoparticle-assisted pulsed laser deposition on ZnO buffer layers deposited on a-cut sapphire substrates. In this report, the new possibilities of UV laser-processing to the field of ZnO buffer layers and ZnO nano/microcrystals are suggested. Effects of ultraviolet laser-irradiation on morphological and electrical properties of ZnO buffer lay-ers were investigated. After laser irradiation, surface work function increased in the region laser-irradiated at 300 mJ/cm2, whereas it decreased in the region laser-irradiated at 500 mJ/cm2. Then, ZnO nanowires were synthesized on the ZnO buffer layers locally laser-irradiated at 300 mJ/cm2 and 500 mJ/cm2 by nanoparticle-assisted pulsed laser deposition. Number densities of ZnO nan-owires were varied depend on laser fluences. It decreased in the region pre-laser-irradiated at 300 mJ/cm2, whereas it increased in the region pre-laser-irradiated at 500 mJ/cm2. Additionally, it was demonstrated that periodically-aligned ZnO microcrystals can be synthesized using four-beam inter-ference laser irradiation to the ZnO buffer layers followed by nanoparticle-assisted pulsed laser deposition. Since these processes do not require any catalysts, they are expected to be the new fabri-cation method for ZnO nano/micro crystals.