Theoretical study of step bunching dynamics in the presence of an alternating heating current

We analyze theoretically the influence of an alternating electric current on step dynamics during sublimation of a vicinal surface. We explain quantitatively why in previous experiments the application of an alternating current left the vicinal surface unaffected, i.e. no step-bunching. This is due to the fact that the excitation period used is much lower than the intrinsic time scale for the cooperative phenomenon that leads to step-bunching. Our analysis suggests that step-bunching should be present, for Si(111) at 1250 °C, at a frequency of about 1 Hz. This should manifest itself by a bunching-debunching process in the course of time. The determination of the excitation frequency above which this process no longer exists should give access to the strength of the electromigration force. The proposed experiment should also constitute a crucial test of the electromigration hypothesis. Discussions of some unresolved puzzles together with outlooks are presented.