Synthesis and Optical Properties of ZnO Nanowires for Nanophotonics

One-dimensional nanostructures, especially semi-conductor nanowires, have been an on-going research topic due to their peculiar optical and physical properties, and their potential for a wide range of the applications in electronics, photonics, and magnetic devices. Such nanostructures can also serve as template matrices for nanoscale sensors. Zinc oxide (ZnO), with its wide bandgap and large exciton binding energy, is a promising semiconductor material for optical devices such as solid state lighting and photovoltaics. ZnO nanowires have recently attracted tremendous interest because of the possibility to combine the unique optical characteristics of ZnO at the nanoscale. However, realizing well aligned nanowires has remained challenging, with various shapes and orientations being reported. The resulting optical properties have not been thoroughly correlated with the shape, orientation and growth parameters of the nanowires. We report here the growth of ZnO nanowires by chemical vapor deposition using both a catalyst-assisted vapor-liquid-solid and a catalyst-free vapor-solid deposition approach. The nanowires were characterized through scanning electron microscopy, x-ray diffraction, optical absorption, micro-photoluminescence, confocal Raman spectroscopy, and Terahertz time domain spectroscopy.