An analysis of the residual strains in epitaxial tin films

Epitaxial tin islands are grown by evaporation onto tin telluride substrates in ultra-high vacuum. The strain within an island, measured by moiré fringe techniques, shows a general inverse variation with size rising to over 2% in islands 100 Å wide. It is shown that the dislocation network at the interface can give incomplete compensation of the mismatch of an island with the substrate causing a periodic variation of the strain due to the introduction of successive misfit dislocations as the island grows. There is no evidence for the existence of a barrier against the nucleation of misfit dislocations at the edge of an island. A simplified model to describe the variation of strain during growth is set out and compared with the more general theory developed by van der Merwe.