SIMPLE-MODEL FOR ANISOTROPIC STEP-GROWTH

We consider a simple model for the growth of isolated steps on a vicin al crystal surface. It incorporates diffusion and drift of adatoms on the terrace, and strong step and kink edge barriers. Using a combinati on of analytic methods and Monte Carlo simulations, we study the morph ology of growing steps in detail. In particular, under typical molecul ar beam epitaxy conditions the step morphology is linearly unstable in the model and develops fingers separated by deep cracks. The vertical roughness of the step:grows linearly in time, while horizontally the fingers coarsen proportional to t(0.33). We develop scaling arguments to study the saturation of the ledge morphology for a finite width and length of the terrace.