Abstract
This study reports the successful growth of large-scale vertically aligned ZnO nanowires on sapphire, silicon, and glass substrate by direct thermal evaporation. In this processing, neither adding metal catalysts nor the usage of seed layers, we fabricate ZnO nanowires via a surface roughness assisted vapor-solid mechanism. Simple processing steps including steel needle scratching, mechanical polishing with sand-paper, and chemical etching have been utilized to improve surface roughness of substrates. By this method, the heterogeneous nucleation sites have been provided largely; as the growth parameters are well-controlled, the synthesis of vertically aligned ZnO nanowires can be achieved. Compared with other methods, this study has some advantages like simple processing, no catalyst contamination, no seed-layer usage and suitable for various types of substrates. On the other hand, the luminescence spectrometer was applied to measure the PL properties of ZnO nanowires. Three obvious peaks in UV (384 nm), blue-green (481 nm), and green (521 nm) region have been observed. Furthermore, as the nanowires have been annealed in atmosphere, the intensity of blue-green peak dropped, which can be the circumstantial evidence of oxygen vancancies.