Activation barriers to strain relaxation in lattice-mismatched epitaxy

We study the activation barriers to strain relaxation in metastable ${\mathrm{Ge}}_{0.25}$ ${\mathrm{Si}}_{0.75}$/Si(100) films by in situ annealing in a transmission electron microscope, observing in real time the dynamic relaxation events of misfit-dislocation nucleation, propagation, and interaction as a function of the sample annealing temperature. Activation energies for misfit-dislocation nucleation and propagation are obtained, and it is firmly established that both these processes and dislocation interactions inhibit strain relaxation in ${\mathrm{Ge}}_{\mathrm{x}}$ ${\mathrm{Si}}_{1\mathrm{-}\mathrm{x}}$/Si epitaxy.