Photoelectron spectroscopy studies of growth, alloying, and segregation for transition-metal films on tungsten (211)

High resolution soft x-ray photoelectron spectroscopy using synchrotron radiation and Auger-electron spectroscopy are used to study late-transition-metal films (Pt, Pd, Ir, Ph, An,) on W(211). It is found that the films prow in a layer mode at 300 K. As a function of the film thickness, different 4f(7/2), photoemission peaks are observed, corresponding to a single monolayer, to an interface layer, to bulk atoms and to surface atoms. Single physical monolayers of these late-transition metals on tungsten are stable against thermal rearrangement. In contrast, when multilayer films of Pdl Pt, Lr, Rh an annealed above 700-1000 K, tungsten atoms diffuse into the overlayer to form an alloy film. Gold constitutes a different case; upon annealing it does not alloy with tungsten but the metal in excess of one monolayer forms clusters. The evolution of the bimetallic systems as a function of coverage and annealing temperature is interpreted by analysis of intensities and shapes of the 4S(7/2) features. Born-Haber cycles and the equivalent core approximation are used to extract thermochemical data concerning energetics of adhesion, segregation, and alloying in these early-late transition-metal systems.