Determination of diffusion energies on face-centred cubic (111) surfaces from diffraction experiments: a Monte Carlo study

The nucleation of adatom islands on face-centred cubic (fcc) (111) surfaces is studied by kinetic Monte Carlo simulations (MCS). The temperature dependence of the island density follows an Arrhenius behaviour with characteristic energy ED/3 (where ED denotes the diffusion energy on terraces), in agreement with classical nucleation theory for the critical nucleus size of one. The diffuse scattering of the diffraction spots in the submonolayer range shows ring-like structures which are attributed to the characteristic island distance, since the ring radius follows an Arrhenius behaviour with characteristic energy ED/6. This energy does not depend on coverage for the submonolayer range investigated (Θ≤0.5 ML), which implies that the diffusion energy can also be obtained from higher coverages where coalescence of islands has already started. The results of these MCS are applied to experimental data of homoepitaxial growth on Pt(111).