Local structure and electronic state of a nanoscale Si island on Si(1 1 1)-7×7 substrate

The structural features and electronic structure of a nanoscale rounded Si island on the Si(1 1 1) substrate are investigated with scanning tunneling microscopy and scanning tunneling spectroscopy. The rounded island is composed of 162 atoms which arrange in three reconstructed 5×5 unit cells. The structural features and electronic structure of the island show the following: the dangling bonds on the outside adatoms of the island have a high density of states compared with that on the inside adatoms; and the height of the outside adatoms is slightly higher than that of the inside adatoms. These results are attributed to a charge transfer caused by the structural relaxation to stabilize the rounded island.