Estimation of the core cut-off parameter for misfit dislocations at a Si_xGe_1-x/Si interface

The misfit dislocation structure at a partially relaxed Si/Si _xGe_1-x interface has been investigated using weak-beam electron microscopy in order to probe features near the dislocation core. The dislocations were found to be dissociated, allowing for the direct measurement of the stacking fault energy at the epitaxial interface. This has been supplemented with the measurement of the width of symmetrical threefold stacking fault nodes at the same interface. These independent measurements have been combined to estimate the dislocation core cut-off parameter using isotropic approximations of anisotropic elasticity theories. The size of the core of the misfit dislocation is consistent with both geometric and atomistic models predicting core delocalization at coherent interfaces.