On the surface segregation of silicon in Cu 3Si

Abstract

Silicon segregates to a large extent to the surface of a Cu 3Si alloy stabilized at 700 K. The top layer contains as much as 70 at% Si, the second and third layers are also significantly enriched in silicon. Such a phenomenon could largely account for the renewal of the surface layers of the silicide as the silicon is consumed during the direct synthesis (of methylchlorosilane by reaction with methyl chloride). As demonstrated by calculations of the segragation free enthalpy based on the broken-bond model, the difference in surface tension between Cu and Si is the main driving force involved in the observed segregation.