Faceting, roughness, and step disordering of vicinal Si(111) surfaces: An x-ray-scattering study.

The equilibrium and nonequilibrium behavior of the step structure of vicinal Si(111) surfaces has been studied in synchrotron x-ray-scattering experiments. Below the 7×7 reconstruction transition temperature of 1100 K, the surface phase separates into macroscopic (111) facets larger than 0.4×0.1 μm 2 and stepped regions with increased step density. At temperatures above the transition up to 1275 K where there is significant sublimation, the surface is thermally rough, characterized by a uniform step lattice with an algebraically decaying correlation function. The algebraic decay exponent η was measured to be 0.18±0.13, in agreement with the theory of entropically interacting steps