Simulation of initial stages of Ge nano-island nucleation on Si (111) surface

Reasons of three-layer Ge island nucleation on Si(111) surfaces at low deposition rate at the initial stages of wetting layer formation were investigated. Simulation of Ge epitaxial growth on atomically clean and flat Si(111) surface was carried out by 3D Monte Carlo model. If the activation energy of heterodiffusion of adsorbate along the substrate is less than homodiffusion energies of the adsorbate and the substrate, growth of multilayer islands is observed. However, for this process the great difference between activation energies of homo and heterodiffusion is necessary (about 1 eV). It was suggested that at the borders of the islands the reconstruction of dangling bonds takes place and dimmers are created. Atom attachment into these bonds requires surmounting of some additional energy barrier. Multilayer growth takes place at small difference in activation energies of adsorbate and substrate atoms (/spl sim/ 0.2-0.3 cV), when attachment probability to the model dimer sites is decreased.