Modelling of layer epitaxial growth: surface morphology and growth mode transitions

Recently we have proposed a simple kinetic model for layer epitaxial growth, which combines a rate equation approach and a concept of a feeding zone. With this model it has distinctively been shown on how with decreasing adatom surface diffusivity and/or increasing the Ehrlich–Schwoebel (ES) barrier height the growth mode crosses over from a smooth layer-by-layer (LL) growth to a rough 3D growth, and a “phase diagram” of the growth mode in the parameter space has been constructed. This paper reports on a systematic study the effect of a critical nucleus size, the growing island collision behaviour (impingement/coalescence) and the existence (in the case of heteroepitaxy) of two different adatom surface mobilities (heterodiffusion in the first layer and self-diffusion in all the next ones) on the epitaxial growth. It is shown that the increase of a critical nucleus size expands a rough growth region, whereas the island collision behaviour weakly affects on the growth mode transition but significantly influences on the nucleation kinetics. The effect of two adatom mobilities is essential at initial stages and dramatically depends on the relation between them: a slower heterodiffusion results in a smoother initial growth and thus retards the transition to a rough growth, whereas a faster heterodiffusion promotes it especially at a higher ES barrier.