Low-temperature growth of ZnO nanowire array by a simple physical vapor-deposition method

Well-aligned single-crystalline wurzite zinc oxide (ZnO) nanowire array was successfully fabricated on an Al₂O₃ substrate by a simple physical vapor-deposition method at a low temperature of 450°C. The diameter and growth rate of ZnO nanowires increased as a function of growth temperature. TEM observation showed that the ZnO nanowires were synthesized along the c-axial direction of the hexagonal crystal structure. We demonstrate that ZnO nanowires followed the self-catalyzed growth mechanism on the ZnO nuclei. Besides high-quality ZnO nanowires, sometimes a fascinating hierarchically ordered ZnO structure was also observed.