Low-flux elucidation of initial growth of Ge clusters deposited onSi(111)−7×7observed by scanning tunneling microscopy

Abstract

Deposition of Ge on $\text{Si}(111)\text{\ensuremath{-}}7\ifmmode\times\else\texttimes\fi{}7$ under very low Ge flux is examined using ultrahigh vacuum scanning tunneling microscopy; Ge atoms are deposited at $150\text{ }\ifmmode^\circ\else\textdegree\fi{}\text{C}$ under a flux of $\ensuremath{\sim}0.005$ or 0.05 ML/min. Initially Ge atoms are substituted for Si atoms on corner adatom sites of faulted half unit cells. At a Ge coverage of 0.08 ML under the lower flux, hollow-centered hexagonal Ge clusters with six protrusions are formed preferentially on faulted half unit cells, which are uniform and separated from other clusters. At the higher flux various types of clusters grow, frequently neighboring with others. This indicates that the low flux is needed to elucidate the stable type of Ge clusters grown on $\text{Si}(111)\text{\ensuremath{-}}7\ifmmode\times\else\texttimes\fi{}7$.