Nucleation and growth of Si/Si(111) observed by scanning tunneling microscopy during epitaxy

Si(111) homoepitaxy was studied with scanning tunneling microscopy (STM) during growth at high temperatures. The nucleation process on top of the epitaxially grown islands was directly observed with atomic resolution. The nucleation on the epitaxial layer occurs preferentially at domain boundaries of the 7×7 reconstruction. The high density of domain boundaries on the grown film and the low density of these surface defects on the original substrate lead to the observed multilayer growth for low coverages. At higher coverages, when the substrate is covered by the epitaxial layer, there is no longer a difference in the defect density in the different layers and the growth mode turns to layer growth. The layer distribution is directly measured with STM and can be described by simple rate equations. The high nucleation probability on top of the epitaxial layer results in an effective mass transport on top of the first-layer islands. © 1996 The American Physical Society.