Shape control and characterization of one-dimensional ZnO nanostructures through the synthesis procedure

The one-dimensional ZnO nanostructures prepared through thermal evaporation under various cooling down procedures by changing the flow rates of the carrier gas and the reactive gas were investigated. The nanorod structures were changed into the nanonail types with a broad head through the reduction of the flow rate of the carrier gas. The decrease of the reactive gas reduced the length of the nail heads due to the limited mass transport of reactive gas. The intensity ratio of the ultraviolet emission/green emission of photoluminescence was proportional to the length of the broad head showing a larger surface area. The vertically aligned nanostructures were grown along the [0 0 0 1] direction of ZnO regardless of the aligned directions. The crystal direction of the nanostructures was determined by that of the initial ZnO crystal.