Structural, electrical and optical properties of copper-doped zinc oxide films deposited by spray pyrolysis

Abstract

The effect of copper doping on structural, electrical, and optical properties of zinc oxide films was evaluated. Copper-doped films (ZnO:Cu) were successfully deposited on a glass substrate by spray pyrolysis at doping levels of 0, 2.5, and 7.5 at% (ZnO, ZC2.5, ZC7.5). All films were polycrystalline, single-phase with ZnO hexagonal wurtzite structure. The films presented nanostructured crystallites, from 36.7 to 38.2 nm. Cu doping increased the electrical conductivity of the ZnO films; this change was proportional to the Cu concentration. The films presented high optical transmittance of 70-80% in the visible wavelength. The energy gap decreased upon Cu doping. The photoluminescence spectrum of all films displayed an intense ultraviolet emission and a weaker blue emission. The emissions shifted to lower wavelengths with increasing dopant concentrations. ZC7.5 presented the most promising properties for an application as transparent conducting oxide: intense optical transmittance and UV photoluminescence, also the lowest electrical resistivity.