MEASUREMENT OF THE ACTIVATION BARRIER TO NUCLEATION OF DISLOCATIONS IN THIN-FILMS

We introduce a method to study the activation barrier to nucleation of dislocations during strain relaxation of thin films. By growing on substrates with a range of misorientations from (001), we change the applied shear stress on the different glide systems, leading to an imbalance between nucleation on the different glide systems. The resulting tilt between the relaxed layer and the substrate provides a direct measure of the stress derivative of the nucleation barrier. A phenomenological model, which makes no assumptions about the detailed nucleation mechanism, can then be used to infer from this the activation energy for nucleation. We obtain an activation energy of 5 eV for the observed nucleation mechanism.