Comparative study of the Si(100) surface reconstruction under successive dehydrogenation. I. Si(100)(1x1)-H surface

AM1-based quantum-chemical semiempirical study has been performed for a nin e-layer cluster containing 178 silicon atoms cut off the silicon bulk. The cluster presents a double layer of the (100) surface unit cells in width an d covers 16 (1 x 1) units in plane. As shown, the cluster size has provided a reliable selection of "self-embedded': unit cells (SEUC) for which edge effects caused by hydrogen terminators on the bottom and back sides of the cluster are practically negligible and which can be considered as the most appropriate model for the surface under study. A transformation of the init ial bare (1 x 1) surface into the (1 x 1)-H form caused by a complete hydro genation of the topmost silicon atoms has been traced. Surface structure is described in terms of spatial (Si-Si distance) and electronic (charge, spi n density, density of electronic states as well as local electron density c ontour maps) characteristics.