Effects of deposition and annealing temperatures on the electrical and optical properties of Ag₂ O and Cu₂ O- Ag₂ O thin films

Ag₂ O and Ag₂ O- Cu₂ O films were deposited on glass substrates by magnetron sputtering of Ag and Cu targets at various substrate temperatures. After deposition, some of these films were annealed using a rapid thermal annealing system, with the variation of temperature. An UV-VIS-NIR photometer and a Hall measurement system were used to characterize the optical and electrical properties of these films. On annealing, Ag₂ O (hexagonal) phase would slowly change to Ag ⁺ Ag₂ O (cubic) phases when the annealing temperature is greater than 200 °C. When the annealing temperature was higher than 450 °C, the Ag₂ O phase would transform into a metallic Ag phase completely. Accordingly, the band gap of these films will change, along with the optical and electrical properties. In the study of Ag₂ O- Cu ₂ O films, it is found that these two-phase composite films could exist obviously when deposited at room temperature. The photoinduced current of these composite films could be increased significantly, compared with that of a single Cu₂ O phase. This is most likely due to that a large band gap semiconductor (Cu₂ O) is coupled with a small band gap semiconductor (Ag₂ O).