Phase transformations of the Pt/Ru(0 0 0 1) interface studied by photoemission

The changes of the core level binding energies as well as the shape of the valence band were correlated with morphological changes in the platinum submonolayer grown on a ruthenium substrate. Transformation of a relaxed (dendritic structure, as deposited at room temperature) to stressed (polymorphic, annealed) phase was detected at 873 K from the Pt 4f binding energy shift of +71 meV. Dissolution of Pt adatoms in the Ru(0 0 0 1) substrate (alloyed phase) took place at higher temperatures. Starting from 973 K the binding energy of the Pt 4f shifts by +175 meV relative to the relaxed adlayer. At the same time, the distance between high binding energy and surface contribution of the Ru 3d increases from −391 (clean) to −429 meV upon alloying.