Thermodynamics and kinetics of surface/interface segregation in the stressed ultrathin alloy film on inert substrate

Highlights: • A method is proposed to evaluate surface/interface segregation in stressed film. • More Ag is segregated on surface than at interface for Cu(Ag) film on sapphire. • Interface segregation is manipulated by modifying film–substrate adhesion energy. • Surface segregation depends on segregating atoms size misfit relaxation on surface. • Segregation kinetics strongly depends on heteroepitaxial strain. A general method is proposed for the simulation of thermodynamics and kinetics of surface/interface segregation in ultrathin alloy films deposited on inert substrates. This method takes into account the effects of the finite size of the system, the interlayer atomic interaction and the heteroepitaxial strain, and is based on the combination of the regular solution broken bond-type model and the modified Darken model. As an example, the method is applied to simulate the equilibrium surface/interface segregation in ultrathin Cu(1 1 1)–0.25at.% Ag alloy film deposited on the sapphire substrate, and the kinetics of its change. It is shown that heteroepitaxial strain strongly affects the chemical compositions of the film surface and its interface with the substrate.