DETERMINATION OF LATERAL INTERACTION ENERGIES IN AGAU ALLOY-FILMS ON RU(0001) BY MONTE-CARLO SIMULATIONS

A lattice eas model with nonadditive lateral interactions is used to d escribe Ag, Au and AgAu bilayer films on a Ru(0001) substrate. By Mont e Carlo simulations of adsorbate confiqurations and thermal desorption spectra of the Ag, Au and AgAu films, the microscopic interaction par ameters of the gold and silver adatoms in the alloy film on Ru(0001) a re obtained. The model reproduces experimental thermal desorption spec tra of Ag, Au and AgAu films on Ru(0001) and also shows segregation of silver in the second monolayer of the alloy in agreement with experim ental results. Based on perturbation theory, the configurational Gibbs free energy G of the AgAu monolayer alloy is calculated as a function of temperature and composition. (C) 1998 American Institute of Physic s. [S0021-9606(98)02410-6].