Effect of thermal annealing on the stress and morphology of deposited nanofilms analyzed using molecular dynamics

Molecular dynamics (MD) simulations are used to investigate the surface roughness and intermixing of grown films and to calculate the atomic-level stress before and after the annealing process. The tight-binding second-moment approximation (TB-SMA) many-body potential is employed to model the interaction. The results reveal that the morphology of the film becomes smoother after 900 K annealing due to the substrate temperature being lower for the as-deposited film. The results indicate that the annealing decreases the number of vacancies and voids for all thin films. More Al atoms penetrate into the substrate after the annealing process. The interface mixing of annealed film is thus better than that of as-deposited film. The first peak of the radial distribution function (RDF) becomes higher and narrower when the Al–Cu film is cooled from 700 to 300 K. This indicates that new grains nucleate and grow to replace those deformed by internal stresses and that recrystallization may occur for the Al–Cu film. In the atomic-level stress analysis, the average normal stress along the thickness direction and the average mean biaxial stress are considered. Both residual stresses decrease for all layers after the annealing process. This implies that internal stress is relieved within the Al–Cu film during the cooling phase.