Phase relationships in Cu-O thin films prepared by sputtering

The conditions for deposition of Cu and Cu-oxide thin films by reactive dc sputtering have been investigated by characterizing the crystal structure of growing films both during and immediately following deposition using an in situ x-ray diffraction technique. The relationship between sputtering conditions and the phases deposited was established for a variety of conditions. At each temperature studied, increasing the oxygen pressure in the system resulted in a systematic change in the phases deposited. Of significant importance was the identification of temperature-pressure regimes in which CuO was stable during deposition but reverted to Cu₂O after the sputtering plasma was extinguished, suggesting a shift in the oxidizing potential in the plasma environment. These results also suggest that the in situ analysis technique may be ideally suited for the investigation of phase relationships and phase diagrams in other systems.