Native oxide layers formed on the surface of ultra high-purity iron and copper investigated by angle resolved XPS

Abstract

Angle resolved X-ray photoelectron spectroscopy (AR-XPS) has been used for characterizing native oxide layers formed on the surface of ultra high-purity iron and copper by exposure to air at room temperature. Thickness of an oxide layer formed on the surface of ultra high-purity iron is found to be thicker than that for ultra high-purity copper in the initial stage of oxidation and almost unchanged by air exposure time. On the other hand, thickness of an oxide layer formed on ultra high-purity copper is found to increase with increasing air exposure time. These results are consistent with spectral information for ultra high-purity iron and copper exposed to air; the chemical state of Fe in the surface of ultra high-purity iron is almost independent of exposure time, whereas the chemical state varies in the surface of ultra high-purity copper by exposure for a long term.