Thermodynamic evidence for surfactant behaviour of Sb in the growth of Ge on Si(001)

Thermodynamic evidence of the Stranski-Krastanov growth of Ge on the Si(001) surface is provided, based upon ab initio density functional theory calculations. Island formation is predicted to begin at a Ge coverage of around three monolayers, in good agreement with recent experimental findings. The presence of a terminating Sb layer is shown to promote epitaxial growth. The analysis of energetic data in terms of surface free energy as a function of chemical potential provides a general theoretical signature for both Stranski-Krastanov and epitaxial growth modes, (C) 1998 Elsevier Science B.V.