Scanning-tunneling-microscopy study of the Si(111)-7×7 rest-atom layer following adatom removal by reaction with Cl

In this scanning-tunneling-microscopy study we find that the reaction of Cl with Si(111)-7×7 results in extensive surface modification. On a Cl saturated and annealed surface, most of the adatom layer is stripped away, permitting the complete underlying Si-rest-atom layer to be imaged for the first time. The structure of this layer is shown to correspond closely to that predicted by the dimer-adatom stacking-fault model. We directly observe the presence of the stacking fault, an electronic effect associated with this fault, and different outward surface-normal relaxations in the faulted and unfaulted regions of the cell. © 1989 The American Physical Society.