misfitdislocatie

Misfit dislocation (Dutch: misfitdislocatie) is a crystallographic defect located at the interface between two materials that have differing lattice constants. It arises in heteroepitaxial systems, where a film is grown on a substrate with lattice mismatch and the interface must accommodate the mismatch to relieve strain.

When a film thickens beyond a characteristic critical thickness, the elastic energy stored in the strained lattice is reduced by introducing dislocations at the interface. The dislocation lines lie in the interface plane, and the Burgers vector is also in the interface plane; misfit dislocations are typically edge-type and aligned along directions of high mismatch.

A network of misfit dislocations can form at the interface, with the average spacing between dislocations inversely related to the lattice mismatch and the Burgers vector. In simple models, spacing D ≈ b/|f|, where f is the relative lattice mismatch f = (af − as)/as and b is the Burgers vector magnitude. The dislocation density ρ is roughly 1/D.

Function and impact: misfit dislocations relieve a portion of the misfit strain, enabling thicker films and altering the electronic, optical, and mechanical properties of the heterointerface. They can degrade crystal quality, act as scattering centers for carriers, and serve as nonradiative recombination sites; however, a controlled misfit-dislocation network is sometimes used to engineer strain relaxation.

Observation and applications: misfit dislocations are studied with transmission electron microscopy and X-ray diffraction, among other techniques. They are a central consideration in the design of semiconductor heterostructures and oxide interfaces, influencing device performance and reliability.