Monte-Carlo investigation of vertical correlations in self-organized multilayer growth of islands

The usual kinetic Monte-Carlo method, adapted to treat off-lattice problems, is used to investigate the experimental observation of the vertical self-organization of buried islands, grown in heteroepitaxial multilayers films. It is found that, during the early stage of island nucleation and growth (before Ostwald ripening), the adatoms diffuse to preferential sites, just above the centers of the buried islands, resulting in the vertical replication of the islands. Starting from an ordered island array, this ordered configuration is reproduced during the subsequent growth of the multilayer. Starting from a ‘quasi-ordered’ island array, where a few islands are larger than the others, it is found that the system relaxes quickly within two bilayers toward the common island size. The distribution curve of the vertical correlations is reported. The map of the stress inside a spacer layer is calculated by means of molecular dynamics methods. All these results confirm the model of the island-induced strain fields resulting in the directed diffusion of adatoms above the buried islands. All these results come out naturally from the off-lattice model described above.