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 CuAl 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 CuAl O2 was found dominant in the films, including small amounts of Cu Al2 O4, Al2 O3, and amorphous Cu2 O. The effect of varying CuAl 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 CuAl 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 0.289 S cm-1 and a transparency of 80%, was found to have a CuAl ratio of 1.4±0.3. In addition, the mechanism of the p -type conduction of copper aluminum oxide was discussed. © 2005 American Institute of Physics.