Controlled growth of ZnO layers and nanowires using methane as reducing precursor

摘要

Zinc oxide (ZnO) layers and nanowires were grown by chemical vapor deposition (CVD) using methane (CH_4) as reducing agent. Compared to conventional CVD processes, which commonly use graphite powder to reduce the ZnO powder source material, this low-cost method allows an improved controllability of the growth processes. Specifically, the consumption of the source material-a commercially available ZnO powder-can be controlled in a very precise way by varying the flow of the reducing CH_4 or the re-oxidizing O_2. Using this parameter, the growth can be switched between ZnO layers and nanostructures. High-quality ZnO layers have been grown on gallium nitride (GaN) substrates and on c-plane sapphire with an intermediate aluminum nitride (A1N) nucleation layer. By adjusting the growth conditions accordingly, ZnO nanowires were also grown with this method catalyst-free using a- and c-plane sapphire with ZnO nucleation layer as a substrate. The optical properties of the nanowires were investigated by low-temperature photoluminescence (PL) and compared to samples grown by conventional carbo-thermal CVD.