TEMPERATURE-DEPENDENCE OF THE STEP STRUCTURE OF VICINAL SI(001) SURFACES

Si(001) surfaces miscut slightly towards the [110] direction consist of alternating domains of (1 x 2) and (2 x 1) reconstruction, separated by inequivalent, single-atomic-height steps; at higher miscut angles, the surface is mainly monodomain, with terraces separated by double-atomic-height steps. High-resolution low-energy electron diffraction has been used to determine the step structure of vicinal Si(001) as a function of both temperature and miscut angle. The concentration of double-atomic-height steps continuously increases with miscut angle and, for vicinalities greater than approximately 2-degrees, decreases with increasing temperature. From a comparison of the experimental results with the predictions of a one-dimensional model treating the problem in terms of chemical equilibrium in a two-component system we obtain information on the energetics of the structure transformation.