THE DRIVING FORCE BEHIND THE CHEMISTRY OF HYDROGEN ON THE SI(111)-7X7 SURFACE

A scanning tunneling microscopy and spectroscopy study of the chemistry of H on the Si(111)- 7 x 7 surface is presented. It is shown that the driving force behind the chemistry is the relaxation of the strained bonds formed by the reconstruction. The limited number of such bonds accounts for the apparent saturation of H on this surface. The manner in which this relaxation occurs determines both the nature and the population of different hydrides present on the surface. Models that fail to account for the presence of these strained bonds and their modes of relaxation necessarily provide an inadequate description of the surface chemistry.