Photoresponse of sol-gel-synthesized ZnO nanorods

ZnO nanorods were grown on $SiO2/Si$ substrates by a sol-gel method at low temperatures of around $T=95 °C.$ The diameters and the lengths of ZnO nanorods increased at high concentrations of zinc nitrate hexahydrate and methenamine solution. Current–voltage characteristics of the ZnO nanorods network followed a typical nonlinear behavior with significant photoresponse below $λ<400 nm$ in air, and the conductance was enhanced in vacuum with negligible photoresponse. In photoluminescence (PL) and photocurrent (PC) spectra, the PL peak $(λpeak=380 nm$ and 3.26 eV) did not match the PC edge $(λedge=400 nm$ and 3.1 eV), indicating the nondirect band-gap transition in photocurrent. The origin of the photocurrent was discussed from the point of the influence of the desorption of adsorbed water molecules on the surface or inside the ZnO nanorods.