XPS, AES and friction studies of single-crystal silicon carbide

Abstract

An investigation was conducted to examine the surface chemistry and friction behavior of a single crystal silicon carbide (0001) surface in sliding contact with iron at various temperatures to 1500°C in a vacuum of 3 × 10 nPa using X-ray photoelectron and Auger electron spectroscopies. The results indicate that graphite and carbide-type carbon are seen primarily on the silicon carbide surface in addition to silicon at temperatures to 800°C by XPS and AES. The coefficents of friction for iron sliding against a silicon carbide (0001) surface were high at temperatures to 800°C. At 800°C, the silicon and carbide-type carbon are at maximum intensity in the XPS spectra. With increasing temperature above 800°C, the concentration of the graphite increases rapidly on the surface, while that of the carbide-type carbon and silicon decrease rapidly and this presence of graphite is accompanied by a marked decrease in friction. The thickness of the graphite layer is of the order of 2 nm. When the friction experiments were conducted at temperature above 800°C, the coefficients of friction were dramatically lower. The surfaces preheated to 1500°C also gave dramatically lower coefficients of friction when reheating in the sliding temperature range of from room to 1200°C. This reduction in friction is due to the graphite layer on the silicon carbide surface.