The effect of substrate temperature on the properties of Cu-Al-O thin films prepared by sputtering

Cu-Al-O thin films were deposited by RF magnetron sputtering using polycrystalline CuAlO2 target. Fourier transform infrared spectra show the Cu-0, Al-0 and O-Cu-O bonding related with CuAlO2 phase. Cu-Al-O thin films show good transparency in the visible range, and the transmittance is 60%-70% for the films prepared at 400 degrees C similar to 500 degrees C. The direct and indirect band gap energies estimated are 3.52 eV and 1.83 eV, which are consistent with those of polycrystalline CuAlO2 film. In the range of close room temperature (RT), the conductive mechanism of Cu-Al-O thin films belongs to the thermally activated conduction. The electrical conductivity of the films increases and then decreases as the substrate temperature increases. The film deposited at 500 degrees C has the higher electrical conductivity (RT, 2.36x 10(-3) S center dot cm(-1)), which may be due to the improvement of the structure of Cu-Al-O thin film.