1203.2061 (Vesselin Tonchev)

Classification of step bunching phenomena    [PDF]

Vesselin Tonchev

The classification of bunching of straight steps on vicinal crystal surfaces identifies two types according to the behavior of the minimal step-step distance in the bunch lmin with increasing the number of steps N in it. In the B1-type lmin remains constant while in the B2-type it decreases. Both types are illustrated by new results for well-known models. The precise numerical analysis is aimed at the intermediate asymptotic regime where self-similar spatiotemporal patterns develop. In the model of Tersoff et al. the regular step train is destabilized by step-step attraction of infinite range. It is shown that this model belongs to the B1-type and the same time-scaling exponent of 1/5 for N, terrace width and bunch width is obtained. An extended set of scaling exponents is obtained from the model of S.Stoyanov of diffusion limited evaporation affected by electromigration of the adatoms. This model is of B2-type and shows a shift of the exponents with respect to the predictions of the hypothesis for universality classes in bunching thus requiring further modification of the latter.

View original: http://arxiv.org/abs/1203.2061