Surface islands and their elastic interaction with adatoms

We describe the elastic interaction between adatoms on a (001) bcc surface and monolayer-high two- and three-dimensional islands, within the general context of thin-film growth. A discrete harmonic model based on the concepts of eigenstrain and surface stress yields the elastic field owing to the presence of adatoms and islands. Adatoms can be attracted or repelled by islands, depending on the sign of the interaction energy. Our results indicate that the elastic field does not generally favor a flat two-dimensional growth mode for homoepitaxy, or heteroepitaxy, when the overlayer is in compression. Based on elastic interactions alone, our results indicate that, in heteroepitaxy, two-dimensional step-flow growth becomes likely only for overlayers in tension. The model used in the study offers substantial advantages in computational efficiency when compared with atomic simulations that are the norm in this field.