XPS, Auger study of Cu 3Si and its reaction with oxygen

Abstract

The copper silicon alloy Cu 3Si (η phase) was investigated by XPS and Auger analysis. XPS binding energies of Si2p 3 2 = 99.4 eV and Cu2p 3 2 = 932.7 eV were found, identical to their values in pure elemental Si or Cu, respectively. The X-ray induced Cu LMM Auger peak was observed at kinetic energy of 914.1 eV, again similar to that found for pure copper metal. In the electron excited N( E) Auger spectrum the Si LVV for η phase displays a shoulder at 92.3 eV on the main Si peak (89.0 eV). This shoulder causes the derivative spectrum to split into two negative excursions at 90.3 and 94.3 eV. Cu 3Si was found to react readily with oxygen. The oxidation state of Cu in η phase was stable with respect to O 2 exposure. Silicon however, was preferentially oxidized to SiO 2 with a decrease in the surface Cu/Si ratio with exposure to O 2 and air. Exposure of Cu 3Si to air for two weeks produced oxide layers 3600 Å deep.