Grande conférence iLM

Friday 27 May 2011 à 14h00.

On the coexistence of bunching and meandering instabilities during step-flow epitaxy

''Vicinal surfaces consist of terraces separated by atomic steps. During step-flow growth, adsorbed atoms (from the vapor or a beam) diffuse on the terraces until they attach to steps, causing them to advance. This collective lateral motion of steps results in the growth of the underlying crystalline thin film. For a train of initially equidistant straight steps, two modes of morphological instabilities occur: bunching, which leads to regions of high step density separated by wide terraces, and meandering, whereby steps become wavy. Experiments indicate that bunching and meandering can coexist on some stepped surfaces, in contradiction of the predictions of the classical Burton-Cabrera-Frank (BCF). In this talk, I will review the BCF theory and present a thermodynamically consistent (TC) generalization of it that resolves this apparent paradox. In particular, I will show that step bunching and meandering can occur simultaneously, provided that the adatom equilibr ium coverage is not negligible. I will then compare the TC model with various extensions of the BCF framework that also attempt to reconcile theory with experiments.''