A new relaxation mechanism in nanoscale films

A new mechanism of stress relaxation in heteroepitaxial films of nanoscale thickness is suggested and theoretically described. The mechanism represents nucleation of a 'non-crystallographic' partial dislocation (at the film-substrate interface) whose Burgers vector magnitude continuously grows during the nucleation process. It is shown that the new mechanism effectively competes with the standard nucleation of a perfect misfit dislocation at the free surface of the film and its further glide towards the film-substrate interface