In situ study of relaxation of SiGe thin films by the modified Frank-Read mechanism

We have studied the dynamics of thermal relaxation of highly metastable films of SiGe/Si(100) in situ in the transmission electron microscope (TEM). This makes it possible to study the early stages of strain relaxation, and thus obtain information about the nucleation of dislocations. We find that, when care is taken not to introduce artifacts during sample preparation, relaxation occurs by the multiplication of "precursor dislocations" through a mechanism similar to the Frank-Read mechanism. An individual nucleation site is observed, confirming the model previously proposed.