A THEORETICAL-STUDY OF STEP BUNCHING DYNAMICS IN THE PRESENCE OF AN ALTERNATING HEATING CURRENT

We analyze theoretically the influence of an alternating electric curr ent on step dynamics during sublimation of a vicinal surface. We expla in quantitatively why in previous experiments the application of an al ternating current left the vicinal surface unaffected, i.e. no step-bu nching. This is due to the fact that the excitation period used is muc h lower than the intrinsic time scale for the cooperative phenomenon t hat leads to step-bunching. Our analysis suggests that step-bunching s hould be present, for Si(lll) at 1250 degrees C, at a frequency of abo ut 1 Hz. This should manifest itself by a bunching-debunching process in the course of time. The determination of the excitation frequency a bove which this process no longer exists should give access to the str ength of the electromigration force. The proposed experiment should al so constitute a crucial test of the electromigration hypothesis. Discu ssions of some unresolved puzzles together with outlooks are presented .