Non-equilibrium microstructure of the (110) vicinal surface of Si during MBE

We consider the layer-by-layer growth on vicinal surfaces when the separation between the geometrical steps is of the order of an adatom diffusion length with respect to irreversible nucleation. The surface diffusion is strongly anisotropic, therefore the steps become rough. We derive a type of diffusion equation for kinks on the roughened steps and obtain a distribution function of the lengths of the terraces between two adjacent steps. This enables us to calculate the distribution of quasi 1D nuclei on the terraces. We predict a sharp increase in the number of non-equilibrium surface vacancies in the range of parameters where the nucleation takes over from `step flowʹ growth. The theory is applied to the (110) vicinal surface of silicon. Calculated results are compared to some previously published and new experimental data.