SURFACE ALLOY FORMATION AT THE SM RU(001) INTERFACE - EVIDENCE FROM RU 3D CORE-LEVEL EMISSION/

Vapor deposited Sm on a Ru(001)surface at 500 K has been investigated by X-ray photoelectron spectroscopy (XPS), temperature programmed deso rption spectroscopy (TPD) and work function measurements. The developm ent of a first monolayer can be described as simple adsorption of Sm o n the Ru(001) surface. At higher coverages, intermixing of Sm and Ru o ccurs leading to the formation of a SmRu alloy. The formation of an in terfacial alloy above 1 ML coverage is confirmed by Ru 3d core-level p hotoemission. The average valency of Sm in the alloy phase is determin ed. Temperature dependent experiments indicate the formation of two al loy phases at the 400-700 and 700-800 K regions. TPD data indicate the zero-order desorption of Sm. Work function changes show that there is a significant amount of charge transfer from Sm atoms to the Ru subst rate at low coverages.