Growth and structure of thin Pt films on Cu(111) studied by low energy Li+ ion scattering

The growth and structure of thin Pt films on Cu(111) have been studied by low energy Li⁺ ion scattering. The results are compared to those obtained from a Cu₃Pt(111) single crystal alloy. Deposition of Pt on Cu(111) at coverages up to a few monolayers at room temperature (≤ 50°C) and then annealing to 300°C result in the formation of a metastable surface alloy. This surface alloy has been examined to consist of at least three layers of Cu₃Pt by analyzing the incident angle dependence associated with shadowing effects. The experimental results also show that the surface composition depends strongly on annealing temperature. The formation of a relatively stable surface alloy in local equilibrium over the few topmost layers is discussed on the basis of the segregation and ordering behaviour. No surface chemical ordering of the surface alloy has been evidenced in this study.