Interfacial reactions of ultrahigh-vacuum-deposited Cu thin films on atomically cleaned (111)Si. II. Oxidation of silicon catalyzed by η″-Cu3Si at room temperature

Room-temperature oxidation of (111)Si catalyzed by η″-Cu3Si has been studied by transmission electron microscopy, x-ray diffractometry (XRD), and Auger electron spectroscopy. XRD analysis showed that volume fractions of η″-Cu3Si and Cu decrease and increase with exposure time in air ambient, respectively. From TEM diffraction analysis, Cu precipitates were found to be epitaxially related to Si. After prolonged exposure in air, the Cu precipitates were found to form an irregular network structure in the SiO2 layer. Examination of the same area of annealed samples with intermittent exposure in air indicated that the oxidation was mainly initiated at the grain boundaries. Significant differences in room-temperature oxidation behavior between (111) and (001) samples were found.