THE REDUCTION OF COPPER-OXIDE THIN-FILMS WITH HYDROGEN PLASMA GENERATED BY AN ATMOSPHERIC-PRESSURE GLOW-DISCHARGE

The reduction of copper oxide thin films by a hydrogen plasma generate d by an atmospheric-pressure glow (APG) discharge was investigated. Th e copper oxide films were prepared by heating the sputtered copper fil ms to 150 degrees C in the air (heat-formed copper oxide) or by sputte ring (sputtered copper oxide). Both films were composed of Cu2O. The r eduction occurs first on the surface, then the Cu/Cu2O interface gradu ally shifts from the surface into the inner region and finally the who le layer is reduced to metallic copper. This process is approximately explained by assuming that the diffusion of the atomic hydrogen in the reduced layer is the rate-deyermining step. By transmission electron microscopic (TEM) observation, a layer of 3-5 nm thickness composed of many Cu2O microcrystals was observed along the surface of the heat-fo rmed copper oxide. After the APG hydrogen plasma treatment, the crysta l Cu2O layer disappeared and the crystalline lattice was re-arranged t o form large crystal Cu grains.