TIME-RESOLVED OBSERVATION OF CVD-GROWTH OF SILICON ON SI(111) WITH STM

Scanning tunneling microscopy is used to study the epitaxial growth of silicon on Si(111)-(7 x 7) by Chemical Vapour Deposition (CVD) of dis ilane (Si2H6) at elevated substrate temperatures directly during the g rowth process. Different kinetic processes, as island nucleation, grow th and coarsening and step flow have directly been imaged as a functio n of temperature and Si2H6 flow. On a substrate with a low defect conc entration several growth modes depending on the flux and the total cov erage are distinguished: the formation of multi-level islands as a tra nsient mode leaving the substrate partially uncovered up to 20 bilayer s, a transition to layer-by-layer growth when the multi-level islands initially formed coalesce and the formation of three-dimensional islan ds with tetrahedral shape at higher growth rates which are only metast able due to the presence of hydrogen at the surface. The equilibrium s hape of two-dimensional islands is a hexagon whereas the kinetically i nfluenced shape during growth is triangular.