Fracture and the formation of misfit dislocations between PbS and PbSe

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Abstract
Experiments performed to determine the modes of misfit dislocation formation in (001) deposits of PbS on PbSe suggest that the dominaant process is as follows. Thin films of PbS on PbSe are elastically strained to accommodate most of the misfit between the two lattices. These strains give rise to tensile stresses which cause the PbS to fracture on {100} planes perpendicular to the film plane. Fracture is followed by nucleation of misfit dislocations at point where the lines of intersection of (100) and (010) fracture surfaces meet the PbS-PbSe interface. The dislocations are in edge orientation. Their Burgers vectors lie in the interface, and are of the type ½a⟨110⟩. This mechanism for dislocation formation divides the PbS film up into microcrystallites which are elastically strained to match the PbS lattice along one of the ⟨110⟩ directions in the interface but not along the other. The crystallites are separated from one another by low-angle tilt boundaries. The angle of tilt across the boundaries is approximately equal to the misfit between the unstrained lattices of PbS and PbSe.

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