EXPERIMENTAL-STUDY BY HE DIFFRACTION (TEAS) OF A VICINAL SILICON (100) SURFACE - SI(1 1 1 7)

The vicinal Si(100) surfaces show a single-step or double-step reconstruction depending on the miscut angle of the surface. This phenomenon is now well known from LEED and STM studies. A critical miscut angle of the order of 3-degrees can be deduced from the set of available data with the observation of the crystal at room temperature. In our He beam scattering experiment the Si(1117) face is investigated which corresponds to a miscut angle of 4.76-degrees. In this way, a double-step reconstruction is guaranteed at room temperature. We follow the evolution of the surface structure as a function of temperature. A strong structural modification is found at 800 K, which is interpreted as a transition from the initial double-step structure to the single-step reconstruction. This observation is in good agreement with the prediction of a model presented by Alerhand and co-workers.