UNBINDING OF DOUBLE STEPS ON VICINAL SI(001) SURFACES

The nature of the transition between double-stepped and single-stepped structures of vicinal Si(001) surfaces is investigated theoretically. By using the transfer-matrix method and the elastic monopole and dipo le step-step interactions, modified in such a way that they are valid at small step separations, it is predicted that the double steps, whic h are stable only at low temperatures and large miscut angles (theta g reater-than-or-equal-to 1.37-degrees), gradually unbind into pairs of single steps as T is increased or theta is decreased. The recently pub lished experimental data support the proposed model.