EVOLUTION OF A TRAIN OF INTERACTING STEPS IN A SURFACE-DIFFUSION FIELD

We study the time evolution of a train of parallel straight steps interacting with an elastic interaction. A general formula for the step velocity is given as a function of the step distances, the interaction strength and the kinetic coefficients of the step. If the attachment kinetics from the lower terrace of the step is faster than that from the upper terrace, the interference of diffusion field gives rise to an effective attraction in sublimation. There is a critical undersaturation below which two repulsive steps can form a bound state. When a step collides with a bound pair, recombination of the steps takes place, which looks like billiards. For an equidistant step train, under a similar condition, an instability occurs and the steps form pairs, which has a significant effect on the growth law of the vicinal surface.