Nanoscale lateral variations in the stress field of undulated Si0.7Ge0.3/Si(100) films were experimentally studied via in situ transmission electron microscopy annealing and through finite element calculations. When annealed at ~480C, misfit dislocations in a 30nm film (having surface undulations of ~70nm wavelength and ~3nm amplitude) propagated at 80nm/s average speed but with periodic variations from 0 to 30nm/s at the peaks of the undulations to 160 to 240nm/s at the troughs. A 2.0GPa average film stress with variations from 3.2 to 4.4GPa at the troughs to 0.7 to 1.2GPa at the peaks was inferred from the observed dislocation velocities. These stress variations were significantly higher than those calculated from a finite element model of Si0.7Ge0.3/Si with the same surface geometry. Using standard models of dislocation kink dynamics, it was calculated how the effect of high stresses at the undulation troughs would be expected to enhance kink nucleation rates, and have found good agreement between the present models and the experimentally observed range of dislocation velocities. These observations demonstrated the potential of probing the nanoscale structure in thin films through local variations of dislocation velocities.

Nanoscale Mechanisms of Misfit Dislocation Propagation in Undulated Si1-xGex/Si(100) Epitaxial Thin Films. C.C.Wu, E.A.Stach, R.Hull: Nanotechnology, 2007, 18[16], 165705 (6pp)