Growth, doping, and characterization of ZnO nanowire arrays

Abstract

Zinc oxide (ZnO) nanowire (NW) arrays were grown by chemical vapor deposition using the carbothermal reduction of ZnO powder at different pressures from 0.13 to 1.0 atm on basal plane sapphire substrates. The ZnO NWs were oriented in their [0001] direction. Lower growth pressures led to generally longer and smaller diameter wires. A model relating the length and diameter of the NWs was used to interpret the growth mechanism of these ZnO NWs as a function of pressure as the combination of adatom diffusion along the NW sidewalls and direct impingement growth on the NW tip. Al-doped ZnO NWs were synthesized by introducing Al power into the source material, resulting in an Al mole fraction up to 1.8 at. % in the NWs and a concurrent reduction in NW resistivity. Raman spectroscopy revealed slight lattice distortion to the ZnO crystal lattice, while room temperature photoluminescence showed an increase in the near band edge emission concurrently with a reduction in the green emission. The near band edge emission was also blue shifted in a manner consistent with the Burstein–Moss effect in degenerated semiconductor materials.