Transition from 2D to 3D growth during Ag/Si(111)-(7 x 7) heteroepitaxy

The Stranski-Krastanov growth of Ag on Si(111)-(7 x 7) surface at coverages from 0.5 to 2.5 ML, different temperatures (< 500 K) and deposition rates has been investigated by STM. A 2D wetting layer with complex structure has been observed. Deposition beyond critical thickness leads to the formation of 3D islands with a very low height-to-size ratio. The critical thickness increases with temperature. At the onset of 3D growth almost all islands have a uniform height of 2 ML of Ag(111). During further deposition, 3D islands higher than 2 ML appear. The top layers of the islands are always fully completed. 3D island densities, size and height distributions are discussed. A qualitative change in the morphology of the wetting layer and the temperature dependence of 3D island density at elevated temperatures have been observed. (C) 2001 Elsevier Science B.V. All rights reserved.