The influence of Cu∕Al ratio on properties of chemical-vapor-deposition-grown p-type Cu–Al–O transparent semiconducting films

Abstract

Transparent p-type copper aluminum oxide (Cu–Al–O) semiconducting thin films, with Cu∕Al atomic ratios ranging from 1.0 to 4.3, were deposited by plasma-enhanced metal-organic chemical-vapor deposition. The films were grown on z-cut single-crystal quartz substrates, at a substrate temperature of 450°C. Crystalline CuAlO2 was found dominant in the films, including small amounts of CuAl2O4, Al2O3, and amorphous Cu2O. The effect of varying Cu∕Al ratio on the structural, electrical, and optical properties of the films were studied by x-ray diffraction, energy dispersive x-ray spectroscopy, x-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy, and Seebeck technique, and discussed. We were able to optimize the Cu∕Al ratio for the p-type conductivity and transmittance in copper aluminum oxide thin films, and the best conductive film, with a room-temperature conductivity of 0.289Scm−1 and a transparency of 80%, was found to have a Cu∕Al ratio of 1.4±0.3. In addition, the mechanism of the p-type conduction of copper aluminum oxide was discussed.