Growth of Pt thin films on Cu(111) and formation of Pt/Cu surface alloys: Growth mechanism and diffusion barrier

Ultra-thin platinum films evaporated on Cu(111) at 100 K and at room temper ature were investigated by using in situ Auger electron spectroscopy (AES) and low energy electron diffraction (LEED). A growth mechanism of the layer -by-layer type was evidenced up to at least 5-ML of Pt. Over the first Pt m onolayer, the Pt-Pt bond distances were strained about 7 % beyond the equil ibrium bond distances found for bulk platinum. Surface alloys were formed b y diffusing the Pt adatoms into the Cu(111) substrate at temperatures above 500 K with a diffusion barrier of 0.85 eV. For higher annealing temperatur es, the Pt concentration got smaller. From an Auger depth profile, the diff usion barrier for surface alloy formation was estimated using Fick's second law.