CHAOTIC STEP BUNCHING DURING CRYSTAL-GROWTH

We study a simple model for step bunching during crystal growth by propagating a disturbance into an unstable system of equidistant steps. The system exhibits a wide range of different bunching modes as a function of the initial step spacing, leading to distinctive spatial patterns: periodic (with subharmonic bifurcations), chaotic and intermittent. Linear and nonlinear marginal stability theory gives extremely accurate predictions of the velocity of the propagating front. One of the bifurcations is identified as a transition from a regime where linear marginal stability applies to a nonlinear marginal stability regime. The location of this bifurcation is determined accurately.