Synthesis of a cuprite thin film by oxidation of a Cu metal precursor utilizing ultrasonically generated water vapor

A Cu2O thin film of cuprite crystal structure was fabricated via a decomposition reaction of water vapor generated by ultrasonic vibration. The thin film, which was grown on a soda-lime glass substrate at 530 °C, exhibited a prominent (111) preferred orientation with an optical bandgap of about 2.1 eV and resistivity of 2.81 × 104 Ω cm. Generation of H2 gas during the reaction process contributed to suppressing the growth of impurity tenorite phase. In a conventional process of thermal oxidation, the formation of the cuprite phase was always accompanied by that of the tenorite phase due to an excess oxygen exposure near the surface of the films.