Chemical design and thin film preparation of p-type conductive transparentoxides

Chemical design to find a new transparent conductive oxide having p-type co nductivity has been proposed. Following the chemical design, we have select ed CuGaO2 and CuAlO2 as candidate materials. CuGaO2 thin films were prepare d on silica glass substrates by RF sputtering method. The optical band gap of the film was estimated to be similar to 3.4 eV. Positive sign of Seebeck coefficient demonstrated the p-type conductivity of the film. The dc condu ctivity of the film was 5.6 x 10(-3) S . cm(-1) and the activation energy w as 0.22 eV at room temperature. Because of rough texture of the film, the o bserved conductivity was not an intrinsic property of the material. Further , CuAlO2 thin films were prepared by laser ablation. The film deposited in O-2 atmosphere of 1.3 Pa at 690 degrees C showed higher optical transmissio n in visible and near-infrared regions than previously reported. Contributi on of Cu 3d components to upper edge of valence band in CuGaO2 and CuAlO2 w ere confirmed by photoemission spectroscopic measurements.