Copper and copper oxide thin films were prepared by reactive rf sputtering on glass substrates, and their electrical and optical properties were investigated. Pure copper disks were employed as the targets and mixtures of argon and oxygen as the sputtering gases. Copper oxide thin films with various oxygen contents were obtained by changing the oxygen concentration of the sputtering gas and the rf power density, and X-ray diffraction confirmed that the oxygen content of the films increased from Cu to CuO (i, e., in the order of Cu, Cu+Cu2O, Cu2O, Cu2O+CuO and CuO) with increases in the oxygen concentration of the sputtering gas. The sputtering condition for the formation of Cu2O was found to be very limited. Film resistivity, on the whole, increased with increases in the oxygen content of the specimens. The resistivity of Cu films decreased as their crystallinity increased. This phenomena may be attributed to electron scattering by structural defects. In CuO, on the other hand, film resistivity increased with increases in film crystallinity, indicating that carrier generation due to structural imperfections plays an important role in electrical conduction. Films consisting of Cu and Cu+Cu2O showed metallic conductivity, while those consisting of Cu2O, Cu2O+CuO and CuO showed semiconductive behavior. The latter group also showed photoconductivity.
