Spatially anisotropic atom extraction around defects on Si(001) using a STM

A scanning tunneling microscope has been used to extract atoms that are adjacent to native defects on the Si(001) surface. We found a spatially anisotropic extraction frequency for the different sites around a so-called C defect. The most common occurrence is the extraction of Si atoms from a C defect to form a double dimer vacancy. Extraction of double dimers from the neighboring dimer row on one side of the defect was also observed, but dimers in the neighboring dimer row on the other side of the defect and dimers adjacent to the defect in the same row were rarely extracted. In the case of native dimer vacancy defects, few neighboring Si atoms were found to be extracted. We discuss the relationship of these observations to the energetics of defects on the Si(001) surface.