Lattice and thermal misfit dislocations in epitaxial CaF2/Si(111) and BaF2-CaF2/Si(111) structures.

Abstract

Atomic force microscopy reveals straight slip steps resulting from dislocation glide in the primary {100}〈110〉 glide system in ``low mismatch'' ${\mathrm{CaF}}_{2}$/Si(111) structures. From the height and spacing of the steps, the strain relieved by these misfit dislocations is compatible with the relief of the tensile thermal strain change on cooldown. In ``high mismatch'' ${\mathrm{BaF}}_{2}$/${\mathrm{CaF}}_{2}$/Si(111) structures, dislocations which relieve the thermal mismatch change are mobile, while the 14% lattice mismatch is mainly overcome by sessile misfit dislocations with Burgers vectors parallel to the interface.