Photocurrent in ZnO nanowires grown from Au electrodes

ZnO nanowires were grown between two Au electrodes on an Al2O3-deposited Si wafer. Photoresponse, photoresponse spectrum, and current–voltage (I–V) studies were performed for the investigation into photoconduction mechanism in these nanowires. The photoresponse of the nanowires under the continuous illumination of light with above- or below-gap energies was slow, which indicates that photocurrent in the nanowires is surface-related rather than bulk-related. The photoresponse spectrum represents the above- and below-gap absorption bands for the photocurrents. The I–V characteristics under the illumination of the above-gap light are ohmic, but the characteristics under the illumination of the below-gap light are Schottky. This observation indicates that the above-gap light lowers the potential barrier built in the contact between the ZnO nanowires and electrodes, but that the below-gap light does not lower the potential barrier.