Antimony induced cluster formation on the Si( 111 )7 x 7 surface

The growth of Sb nanostructures at submonolayer coverages on the Si(111)7 X 7 surface was investigated using scanning tunneling microscopy. Sb atoms show a high affinity to substitute Si atoms, e.g. Si adatoms of the Si(111)7 X 7 reconstruction, in all growth regimes. At low Sb coverages, this behavior results in the formation of Si clusters that are known from Si homoepitaxy studies. With increasing coverage, different Sb containing cluster types are observed. In particular, ringlike clusters, which dominate at certain growth conditions, are formed. Based on the observed structural and electronic properties, a structure model was developed for the ringlike clusters. These clusters were found to appear with different heights compared to the surrounding Si surface. Considering that Sb atoms can replace Si cluster atoms, the varying apparent heights are explained by different Sb contents of the ringlike clusters.