DYNAMICS OF THE SI(100) SURFACE

The Si(100) surface is constituted by asymmetric dimers and presents c omplex dynamical behaviour. To understand the influence of dimer motio n on the surface electronic properties, we investigate the dynamics of the Si(100) surface experimentally and theoretically in a wide temper ature range (150-00K). High-resolution electron energy-loss spectrosco py measurements are compared to a microscopic tight-binding calculatio n of the dielectric function. An instantaneous symmetric-like nat dime r configuration due to fast dimer-flipping is responsible for the elec tronic transition at 0.8 eV and for the surface metallization observed at 900 K,well below the suggested incomplete melting temperature (140 0 K).