RATCHET EFFECT IN SURFACE ELECTROMIGRATION - SMOOTHING SURFACES BY ANAC FIELD

We demonstrate that for surfaces that have a nonzero Schwoebel barrier the application of an ac field parallel to the surface induces a net electromigration current that points in the descending step direction. The magnitude of the current is calculated analytically and compared with Monte Carlo simulations. Since a downhill current smoothes the su rface, our results imply that the application of ac fields can aid the smoothing process during annealing and can slow or eliminate the Schw oebel-barrier-induced mound formation during growth. [S0031-9007(97)05 220-4].