Delafossite-CuAlO2 films prepared by annealing of amorphous Cu–Al–O films at high temperature under controlled atmosphere

In this study, amorphous Cu–Al–O films were deposited onto a (100) p-type silicon substrate by a magnetron sputtering system. The films were then annealed at 700 °C and 800 °C for 2 h in N2, air and O2. X-ray diffraction patterns showed that the as-deposited films were amorphous. When the films were annealed at 700 °C, the monoclinic-CuO and spinel-CuAl2O4 phases were detected in all atmospheres. As the annealing temperature increased to 800 °C, delafossite-CuAlO2 (R3¯m and P63/mmc phases) appeared in N2 whereas monoclinic-CuO and spinel-CuAl2O4 phases were detected in air and O2. Thermodynamic calculations can explain the formation of delafossite-CuAlO2 films. The optical bandgap and conductivity of delafossite-CuAlO2 films were 3.30 eV and 6.8 × 10− 3 S/cm, respectively, which are compatible with other data in the literature. The p-type characteristic in delafossite-CuAlO2 films was verified by a hot-probe method.