Auger electron spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS) measurements have been carried out on the β-SiC(100) surface simultaneously. The AES and XPS results differ significantly in the bonding state of oxygen for both as-grown surfaces and as-etched surfaces. Differences in the same carbon-KLL Auger spectra induced by both electron beams and x rays from the same surface suggest that the electron beam used in AES removed considerable amounts of carbonaceous species in the contaminant layers. Furthermore, comparison of the Si 2p and Si LVV spectra revealed that the SiOx (x<2) species on the surface was also reduced by the electron beam used in AES. Although previous AES results have shown that both as-grown and as-etched surfaces of β-SiC(100) were covered with only submonolayer coverage of oxygen bonded to Si atoms, with no detectable carbonaceous contaminants, this work shows that the real surfaces, however, are covered with several tens of contaminant layers, including SiO, CC, CH, and CO bonds.
This paper describes a study of the galvanic corrosion of steel coupled to noble metals in sodium chloride solutions. The corrosion behavior was measured by the amount of galvanic current with a zero impedance ammeter and by the weight loss. The galvanic current flowing from the steel is not related to the cathodic metal, but is proportional to the area ratio of the steel to the cathodic metal. The galvanic current density flowing in the cathodic metal is not related to the area ratio or to the nature of the cathodic metal, and approaches the limiting current density for oxygen reduction. Further, local action currents on the steel depend on the area ratio of the steel to the cathodic metal and they are not related to the concentration of sodium chloride in neutral solution.
The solid state reaction between a thick Fe-film and β-SiC (100) surface in UHV has been studied using AES in conjunction with ion sputtering. Upon annealing of the thick-Fe-film/SiC at 250°C, only the C-atoms diffused to the film surface and exhibited a Fe3C feature. During a 540°C anneal, the Si-atoms also segregated at the surface through grain boundary diffusion and formed the elemental-Si and the Fe-silicide phase. The depth profile showed that the atomic ratio among silicide, Fe3C, graphite and unreacted-Fe in the film was approximately 1:2:0.8:15, indicating a limited reaction. Big pile-ups of both Fe3C and elemental-Si were detected at the Fe-SiC interface, which suggests that the Fe3C acts as a reaction barrier and prevents the free Si-atoms from diffusing into the Fe-film.
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