Fabrication of cuprous and cupric oxide thin films by heat treatment

Cuprous oxide (Cu2O) and cupric oxide (CuO) thin films were prepared by thermal oxidation of copper films coated on indium tin oxide (ITO) glass and non-alkaline glass substrates. The formation of Cu2O and CuO was controlled by varying oxidation conditions such as, oxygen partial pressure, heat treatment temperature, and oxidation time. The microstructure, crystal direction, and optical properties of copper oxide films were measured with X-ray diffraction, atomic force microscopy, and optical spectroscopy. The results indicated that the phase-pure Cu2O and CuO films were produced in the oxidation process. Optical transmittance and reflectance spectra of Cu2O and CuO clearly exhibited distinct characteristics related to their phases. The electrical properties indicated that these films formed ohmic contacts with Cu and ITO electrode materials. Multilayers of Cu2O/CuO were fabricated by choosing the oxidation sequence. The experimental results in this paper suggest that the thermal oxidation method can be employed to fabricate device quality Cu2O and CuO films that are up to 200-300 nm thick.