Atomistic studies of strain relaxation in heteroepitaxial systems

We present a review of recent theoretical studies of different atomistic mechanisms of strain relaxation in heteroepitaxial systems. We explore these systems in two and three dimensions using different semi-empirical interatomic potentials of Lennard-Jones and many-body embedded atom model type. In all cases we use a universal molecular static method for generating minimum energy paths for transitions from the coherent epitaxial (defect free) state to the state containing an isolated defect (localized or extended). This is followed by a systematic search for the minimum energy configuration as well as self-organization in the case of a periodic array of islands. In this way we are able to understand many general features of the atomic mechanisms and energetics of strain relaxation in these systems. Finally, for the special case of Pd/Cu(100) and Cu/Pd(100) heteroepitaxy we also use conventional molecular dynamics simulation techniques to compare the compressively and tensilely strained cases. The results for this case are in good agreement with the existing experimental data. (AU)