STM study of structural defects on in situ prepared Si(111) 1 × 1-H surfaces

Abstract

We have used scanning tunneling microscopy to study the structural defects occurring on Si(111)1 × 1-H surfaces prepared by in situ hydrogen exposure of Si(111)7 × 7 surfaces at elevated temperatures. These defects can be divided into four categories: point-like defects, holes in the first bulk bilayer, islands, and stacking-faulted regions. The two most frequently occurring point-like defects are identified as adatom trihydrides and top-layer atoms with a missing hydrogen atom. The islands observed on the 1 × 1-H surfaces are single-layer linear islands and bilayer-high linear and triangular islands. We have identified three distinct types of island edges and proposed structural models for each type. These models, which involve different arrangements of tilted monohydride edge species, are also applicable for the step edges on the created surfaces. The stacking-faulted regions, triangular in shape, are found to have a double periodicity along the borders which is explained in terms of a dimerization of the surrounding second-layer atoms.