Initial stages of oxidation of Cu0.7Zn0.3(1 1 1)

The initial stages of oxidation of Cu0.7Zn0.3(1 1 1) exposed to O2 at low pressure (7.0 × 10−7 mbar), at room temperature and at 120 °C, have been studied by auger electron spectroscopy (AES), low energy electron diffraction (LEED) and, for the first time on brass surfaces, by scanning tunneling microscopy/spectroscopy (STM/STS). asurements show that the oxidation at room temperature quickly reaches saturation. The comparison with data obtained on Cu(1 1 1) indicates a higher and faster uptake of oxygen on brass. The STM images show that, contrarily to what was observed on Cu(1 1 1), the oxide nucleation is homogeneous on the surface. haviour at 120 °C is drastically different. The oxygen uptake increases considerably and saturation is obtained for higher exposure. The AES signals of zinc and oxygen increase linearly with the exposure, indicating the growth of zinc oxide at the surface promoted by the segregation of Zn from the bulk. At saturation, STM images indicate that the surface is covered by ZnO islands. STS reveals that between the ZnO islands the conductive substrate surface is measured. Moreover two types of islands are differentiated by local spectroscopy. They may be attributed to ZnO{0 0 0 1} islands of different polarity.