GROWTH OF PT CU(100) - FORMATION OF A SURFACE ALLOY/

Synchrotron-radiation induced core-level photoemission spectroscopy (P ES) has been used to characterise the growth of Pt:Cu(100). Decomposit ion 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 t o bz 50%. This result is consistent with the observed c(2 x 2) LEED pa ttern. For higher coverage, the surface alloy is destroyed and a pure and disordered Pt thin film starts to grow. Annealing of the surface a lloy 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 k inetic blocking of the dissolution. The surface composition of this su rface alloy is Cu50Pt50. This particular behaviour of the kinetics of dissolution has been already observed in PtCu(111).