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 degrees C to 800 degrees 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 degrees C, monoclinic CuO and spinel CuCr2O4 phases were simultaneously formed in the film. Upon increasing the annealing temperature to 600 degrees 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 SI-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.