Systematic Study on Experimental Conditions for Large-Scale Growth of Aligned ZnO

In vapor-liquid-solid (VLS) growth, it is generally believed that nanowires would grow as long as the right catalysts and substrate are supplied as well as the growth temperature is adequate. We show here, however, that oxygen partial pressure plays a key role in determining the quality of the aligned ZnO nanowires. We present a “phase diagram ” between the oxygen partial pressure and the growth chamber pressure for synthesizing high quality aligned ZnO nanowires on GaN substrate. This result provides a road map for large-scale, controlled synthesis of ZnO nanowires on nitride semiconductor substrates with the potential to meet the needs of practical applications. The chemical process involved in the growth process is also systematically elaborated based on experimental data received under different conditions. Recently, quasi-one-dimensional (1D) ZnO nanostructures such as nanobelts,1 nanowires,2 nanorods3 and nanosprings/ nanorings4 have attracted a lot of research interest due to their shape induced unique electrical and optical properties for applications in sensors,5 optoelectronics,6 field emissions,7 and logical circuit devices.8 Growth of ZnO nanostructures has been one of the most active fields in nanotechnology.9 Fabricatio