Chemical Design and Thin Film Preparation of p-Type Conductive Transparent Oxides

Abstract

Chemical design to find a new transparent conductive oxide having p-type conductivity has been proposed. Following the chemical design, we have selected CuGaO₂ and CuAlO₂ as candidate materials. CuGaO₂ thin films were prepared on silica glass substrates by RF sputtering method. The optical band gap of the film was estimated to be ∼3.4 eV. Positive sign of Seebeck coefficient demonstrated the p-type conductivity of the film. The dc conductivity of the film was 5.6 × 10⁻³S·cm^-1 and the activation energy was 0.22 eV at room temperature. Because of rough texture of the film, the observed conductivity was not an intrinsic property of the material. Further, CuAlO₂ thin films were prepared by laser ablation. The film deposited in O₂ atmosphere of 1.3 Pa at 690°C showed higher optical transmission in visible and near-infrared regions than previously reported. Contribution of Cu 3d components to upper edge of valence band in CuGaO₂ and CuAlO₂ were confirmed by photoemission spectroscopic measurements.