Structural and optoelectronic properties of p-type semiconductor CuAlO2 thin films

Abstract This study investigates the structural and optoelectronic properties of p-type CuAlO 2 films. The films were prepared through magnetron sputtering deposition and underwent annealing in a controlled Ar atmosphere at 800 °C with different holding times. This temperature ensures that the formation of the CuAlO 2 phase is favored. As the holding time for annealing increases, diffusion of copper, aluminum and oxygen atoms contributes to the phase change and grain growth of CuAlO 2 . CuO, Al 2 O 3 and CuAl 2 O 4 exist as reaction intermediates, but their proportion of the sample is reduced to zero during the formation of CuAlO 2 . No interface compound was found as a byproduct on the quartz substrate and CuAlO 2 film due to the high-temperature annealing. The single-phase CuAlO 2 films had root mean square roughness of 3.98 nm. The average CuAlO 2 grain size increased from 33.70 to 35.43 nm after 4 and 5 h of annealing, respectively. The increased grain size is concurrent with a decrease of the band gap of the CuAlO 2 film. Single-phase p-type CuAlO 2 films showed lower electrical resistivities of 231.9 and 242.5 Ω cm, with direct band gaps of 3.33 and 3.26 eV, respectively.