Growth of Pt/Cu(100): Formation of a surface alloy

Synchrotron-radiation induced core-level photoemission spectroscopy (PES) has been used to characterise the growth of Pt:Cu(100). Decomposition of the Pt 4f(7/2) photoemission lines shows, for Pt deposition up to 2 ML, the formation during the growth process of an extended Pt-Cu surface alloy. We estimate the Pt concentration in the surface layer to bz 50%. This result is consistent with the observed c(2 x 2) LEED pattern. For higher coverage, the surface alloy is destroyed and a pure and disordered Pt thin film starts to grow. Annealing of the surface alloy formed during the growth of the pure Pt thin film at 300 degrees C leads to the same situation: formation of a surface alloy due to a kinetic blocking of the dissolution. The surface composition of this surface alloy is Cu50Pt50. This particular behaviour of the kinetics of dissolution has been already observed in PtCu(111).