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)-(7×7) by Chemical Vapour Deposition (CVD) of disilane (Si₂H₆) at elevated substrate temperatures directly during the growth process. Different kinetic processes, as island nucleation, growth and coarsening and step flow have directly been imaged as a function of temperature and Si₂H₆ flow. On a substrate with a low defect concentration several growth modes depending on the flux and the total coverage are distinguished: the formation of multi-level islands as a transient mode leaving the substrate partially uncovered up to 20 bilayers, a transition to layer-by-layer growth when the multi-level islands initially formed coalesce and the formation of three-dimensional islands with tetrahedral shape at higher growth rates which are only metastable due to the presence of hydrogen at the surface. The equilibrium shape of two-dimensional islands is a hexagon whereas the kinetically influenced shape during growth is triangular.