Low energy ion scattering spectroscopy is applied to determine the surface composition of Pt10Ni90(110). Measurements performed at different scattering geometries allow us to distinguish between scattering from first and second monolayer atoms. Trajectory simulations including neutralization allow the determination of first and second monolayer composition. After annealing at 970 K the topmost atomic layer is found to consist nearly exclusively of Ni atoms, whereas the second monolayer shows a strong Pt enrichment. This oscillating behaviour of the composition depth profiles is observed after bombarding the surface with ions as well. After thermal treatment distinct differences in the temperature dependence of the composition between the first and second monolayer are found.
Corresponding author: W. Hofer (hofer).