SURFACE ALLOYING OF PB ON CU(111) - A TEAS STUDY

Thermal energy atom scattering on vacuum deposited Pb submonolayers on Cu(lll) in close to equilibrium conditions, at substrate temperatures between 303 K and 413 K, gives evidence for: (a) decoration by Pb ato ms of monatomic steps on the Cu surface at degree of coverage 0 < thet a < 0.004; (b) formation of disordered surface alloy in the first latt ice plane of the copper substrate in the coverage range 0.004 < theta < 0.21; (c) formation of non-alloyed Pb layer with a p(4 x 4) structur e above this coverage, up to the monolayer (theta approximate to 0.56) . The latter transition is shown to be of first order. The role of the deposition kinetics in far from equilibrium conditions is pointed out .