Tuning the Growth Mechanism of ZnO Nanowires by Controlled Carrier and Reaction Gas Modulation in Thermal CVD

A general schematic is developed for the main parameters leading to the formation of vapor–solid and catalyst-assisted-grown ZnO nanowires. We developed a schematic representation of the different parameters influencing the growth and discuss them in detail. Selected shape diagrams are presented that correlate the various changes in parameters (carrier and reaction gas flow, powder and substrate temperature) to the observed nanostructures. With the help of the here-presented shape diagrams, we are able to identify unique parameter ranges for film formation, vapor–solid growth, and the switching to the catalyst-assisted VLS-growth mechanism. The systematic experiments demonstrate the controlled growth of VS and catalyst-assisted-grown ZnO nanowires in a CVD reactor by the carbothermal reduction method based on either upstream or downstream deposition techniques.