THE CONDITION FOR STEP FLOW IN MBE GROWTH ON VICINAL SURFACES

We discuss the growth-mode transition from two-dimensional nucleation to step flow in MBE growth on vicinal surfaces, which is observed as the disappearance of RHEED intensity oscillations. With the sticking coefficient of adatoms to the step edges (p(step)) and the coalescence probability of adatoms to form dimers (p11) taken into account, the critical condition for the growth-mode transition is derived for cases in which the surface diffusion coefficient D, as well as p(step) and p11, is anisotropic. It is shown that not only D, p(step), and p11 along the direction perpendicular to the steps, but also those along the direction parallel to the steps, affect the critical condition. In addition, we discuss the difference between the diffusion lengths obtained from the observation of the RHEED oscillation disappearance and those estimated from the distribution of the growth rate on patterned surfaces.