Scanning tunneling microscope observation of Si(111) δ7 × 7 formed by Si deposition

Using scanning tunneling microscopy (STM), we study the initial stage of silicon deposition on Si(111)7 × 7 at room temperature. At less than 0.1 monolayer, three kinds of adsorbed structures are observed. The most common (70%) is a structure which has four maxima around a center dimer in its STM image. The position of the protrusions observed by STM changes drastically in the empty and the filled state. The bias voltage dependence is explained by the molecular orbitals between sp3 bonds which are formed upon the breaking of backbonds of adatoms. Based on the measured diffusion length on the surface, the molecular beam is also analyzed. Si2 is suggested to sublimate from the resistivity-heated Si source.