Step bunching at the surface of a sublimating crystal, that was Joule-heated by a direct electric current, was investigated in the presence of both adatoms and advacancies. It was shown that the inclusion of advacancies in the Burton-Cabrera-Frank step-flow model was crucial in order to reproduce the high-temperature behavior of real (111)Si vicinal surfaces. This provided a complete qualitative picture of the reported morphologies, and strongly supported the electromigration hypothesis. Agreement with experimental data was obtained only by assuming that the force which was exerted on adatoms and advacancies by the electric current was opposite to the latter.

C.Misbah, O.Pierre-Louis, A.Pimpinelli: Physical Review B, 1995, 51[23], 17283-6