Scanning Tunneling Microscopy Observation of Small Si Islands and Atomic Steps on Si(111) 7X7

摘要

Small Si islands and atomic steps on Si(111) 7X7 have been observed by scaning tunneling microscopy (STM). At the edges of both structures, we observed characteristic elliptic double protrusions in the STM images. We have proposed atomic structural models of the islands and steps. Partial collapse of the islands during STM observation is well explained by the proposed model. It is concluded that the double protrusions are caused by the distortion of the 3X3 half unit-cell (HUC) of the dimer-adatom-stacking fault structure. This HUC has a specific structure that only one side of the triangular HUS is connected with a neighboring 3X3 HUC.