Cu–In–O composite thin films deposited by reactive DC magnetron sputtering

Abstract

Cu–In–O composite thin films were deposited by reactive DC magnetron sputtering at room temperature. The samples were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), UV/vis spectrophotometer, four-probe measurement and Seebeck effect measurement, etc. The samples contain Cu, In and O. The ratios of Cu to In and O to In increase with increase in O 2 flow rates. The ratio of Cu to In is over 1 and this suggests that Cu is in excess. The obtained Cu–In–O thin films are very possibly made of rhombohedral In 2O 3 and monoclinic CuO. Transmittance of the films decreases with increase in O 2 flow rate. The decrease in transmittance results from increase in Cu content in the films. The optical band gap of all the samples is estimated to be 4.1–4.4 eV, which is larger than those of In 2O 3 and CuO. The sheet resistance of the films decreases with increase in O 2 flow rate. Conductivity of the films is a little low, due to the addition of Cu and the poor crystalline quality of the film. The conduction behavior of the films is similar to that of In 2O 3 and the conduction mechanism of Cu–In–O thin films is through O vacancy.