NONEQUILIBRIUM MICROSTRUCTURE OF THE (110) VICINAL SURFACE OF SI DURING MBE

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