Changes in surface composition of low-Z compound materials with ion bombardment and heat treatment

Abstract

Changes in the composition of the well defined surface of low-Z carbides have been studied with the use of Auger electron spectroscopy. Polycrystalline B 4C with a stoichiometric bulk composition and single crystals of TiC with a (001) plane and SiC with a (0001) plane were used as the samples for quantitative surface analysis. Comparisons in surface properties of these materials were made by various surface treatments such as ion bombardment with argon (3 keV, 8 μA/cm 2) and heating up to 1000°C under ultra-high vacuum. In the case of B 4C, carbon atoms segregated on the surface with the increase of temperature while with the argon ion bombardment a segregation of boron atoms took place. The surface composition ratios B/C examined at 1000°C were 2.6 and 4.4 with and without the ion bombardment, respectively. The TiC surface, on the other hand, was very stable against the heat treatment and no surface segregation was observed even at 1000°C. However, with the argon ion bombardment carbon atoms segregated slightly to the surface with the atomic ratio Ti/C of 0.87. In the case of SiC, a significant surface segregation of carbon was observed with the atomic ratio Si/C less than 0.3 at 1000°C and this tendency was retarded by the argon ion bombardment to 0.6 at the same temperature.