INITIAL GROWTH AND SURFACE ALLOY FORMATION OF PT ON NI(111)

Auger electron spectroscopy, Rutherford backscattering spectrometry and low energy electron diffraction have been used to study the growth and annealing behaviour of Pt overiayers on Ni(111). The absolute Pt coverages were measured by means of Rutherford backscattering spectrometry. Electron attenuation lengths in platinum have been determined from the Auger uptake curves. For the room temperature deposition of Pt on the Ni(111) surface a disordered layer-by-layer growth is observed. At deposition temperatures above 250°C a pseudomorphic growth type is deduced. Above 350°C a surface alloy film starts to develop. During annealing at 450°C a metastable surface alloy film is formed, with roughly 50%-50% composition and a rather abrupt interface with the Ni bulk. This surface alloy formation is in remarkable agreement with predictions based on the Pt-Ni bulk phase diagram. © 1990.