Effect of step permeability on step instabilities due to alternation of kinetic coefficients on a growing vicinal face

We study the effect of step permeability on step instabilities on a growing vicinal face. When alternation of kinetic coefficients is taken into account, pairing of steps occurs on the vicinal face. Irrespective of the step permeability, the step pairs are stable for a wandering instability. The bunching of step pairs occurs if the steps are impermeable. The bunch size increases with time as tβ with β=1/2, which does not depend on the form of the repulsive interaction potential between steps. The repulsion influences the relation between the step distance in a bunch and the bunch size. When the repulsive potential ζ with the step distance l is given by ζ∼l-ν, the average step distance $\bar{l}$ in a bunch decreases as $\bar{l} \sim N^{-\alpha}$ with α=1/(ν+1). The exponents, β and α are the same as those in the bunching induced by the Ehrlich-Schowebel effect in growth