Horizontal growth and ultraviolet sensitivity characteristics of ZnO nanowires on sapphire substrates

ZnO nanowires were synthesized without any kind of catalyst on a-plane sapphire substrate by chemical vapor deposition (CVD). Only the (100) and (101) diffraction peaks of ZnO were found on the XRD patterns of the samples. SEM images show that the ZnO nanowires are parallel to the sapphire substrate. Following the deposition of Au finger electrodes on the samples, the samples' UV-sensitive performance was detected with a wavelength of illumination of 256nm. The results show that the ZnO nanowires respond very fast to UV-light, the ratio of photo current to dark current is about 30 at 5 V, and the maximum photo-responsibility is of 0.56 A/W at 354 nm.