It was found that the deposition of half of a monolayer of Cu onto the (100) surface of W led to the formation of a sharp c(2 x 2) structure when the surface was annealed at 800K. A low-energy electron diffraction intensity analysis revealed that the Cu atoms were adsorbed displacively into W sites so as to form an ordered 2-dimensional surface alloy. Due to the lattice mismatch between Cu and W, substantial buckling of the first layer of the alloy was also observed. The clean bulk terminated (100) W surface was only just stable relative to the c(2 x 2) vacancy-covered (100) W surface. This relative stability of the vacancy structure explained the driving force behind the formation of this alloy.

P.Hu, A.Wander, L.Morales de la Garza, M.P.Bessent, D.A.King: Surface Science Letters, 1993, 286[1-2], L542-6