A novel method for preparing CuAlO2 thin films and the film properties Original Research Article

Single-phase CuAlO2 thin films have been successfully prepared by rapid thermal reaction of a Cu2O/sapphire structure. Second phases, such as CuAl2O4, could be formed if there were any chance to transform Cu2O into CuO. Therefore, the annealing ambient, the reaction temperature and the temperature ramp rate are crucial for the formation of CuAlO2. An Al2O3 cap layer is necessary to prevent the formation of Cu2O droplets when the sample is heated to a temperature above 1000 °C and turned into a liquid state. The optical bandgap of a CuAlO2 film with monocrystalline structure was determined to be 3.75 eV. The electrical properties related to the oxygen diffusion in and out of the films are reported.