Annealing effect on the structural and optoelectronic properties of Cu-Cr-O thin films deposited by reactive magnetron sputtering using a single CuCr target

The aim of this study is to explore the structural and optoelectronic properties of Cu-Cr-O thin films when processed by the magnetron sputtering method using a single equimolar CuCr alloy target. These films were then post-annealed in a controlled Ar atmosphere at 500°C to 800°C for 2 h. The as-deposited Cu-Cr-O thin film consisted of an amorphous phase and exhibited extremely poor optoelectronic properties. After annealing was conducted at 500°C, monoclinic CuO and spinel CuCr₂O₄ phases were simultaneously formed in the film. Upon increasing the annealing temperature to 600°C, the CuCr₂O₄ phase reacted completely with the CuO phase and transformed into the delafossite CuCrO₂ phase, possessing optimal optoelectronic performance. It has an electrical resistivity of 41 Ω-cm and a light transmittance of 49.5%, making it suitable for p-type transparent conducting electrodes. A further increase in annealing temperature resulted in larger grains and greater surface roughness and void density, which, in turn, degraded the optoelectronic performance.