Monte Carlo simulation of the nucleation and growth of binary-alloy particles of Au, Ag, and Pd on NaCl(100) substrates

The initial phase of thin-film formation from two components that are simultaneously deposited on a substrate was simulated by Monte Carlo calculations of adatom processes, e.g., surface diffusion, reevaporation, nucleation, and cluster growth by collisions and capture. Experiments had revealed that the condensation of Pd is nearly complete on NaCl at 300 °C, whereas Au and Ag exhibit very low initial condensation coefficients. Therefore, the composition of the nuclei differs strongly from that of the vapor beam. Monte Carlo calculations of the composition at the early stage of Au-Pd and of Ag-Pd depositions were fitted to experimental data from earlier work, which allowed us to determine the differences of the atomic energy parameters of the components, e.g., of the energies of adsorption ${\mathit{E}}_{\mathit{a}}$ and of diffusion ${\mathit{E}}_{\mathit{d}}$ with high accuracy. These differences are (${\mathit{E}}_{\mathit{a}}$-${\mathit{E}}_{\mathit{d}}$ ${)}_{\mathrm{Pd}}$-(${\mathit{E}}_{\mathit{a}}$-${\mathit{E}}_{\mathit{d}}$ ${)}_{\mathrm{Au}}$=0.12±0.03 eV, and (${\mathit{E}}_{\mathit{a}}$-${\mathit{E}}_{\mathit{d}}$ ${)}_{\mathrm{Pd}}$-(${\mathit{E}}_{\mathit{a}}$-${\mathit{E}}_{\mathit{d}}$ ${)}_{\mathrm{Ag}}$=0.25±0.05 eV.