Low-temperature growth and relaxation of misfitting films were analyzed, on the basis of 2-dimensional molecular dynamics simulations, by using Lennard-Jones potentials. The temporal evolution of the surface morphology, and the mechanisms of misfit dislocation nucleation and stress relaxation, were monitored. Pseudomorphic film growth was observed up to a critical thickness. In some cases, the formation of voids within the film relaxed some of the stress. At the critical thickness, dislocations nucleated and relaxed most of the misfit. The critical thickness increased with decreasing lattice mismatch, and depended upon the sign of the misfit. The critical thickness of compressively strained films was smaller than that of tensioned films which exhibited the same degree of misfit. The mechanism of dislocation nucleation was different for tension and compression and, in all cases, was associated with the roughness of the film surface. In the compressive case, dislocations nucleated by squeezing out an atom at the base of surface depressions. In the tensile case, the nucleation of misfit dislocations involved the concerted motion of a relatively large number of atoms; leading to the insertion of an extra lattice plane.

Stress Relaxation and Misfit Dislocation Nucleation in the Growth of Misfitting Films: a Molecular Dynamics Simulation Study L.Dong, J.Schnitker, R.W.Smith, D.J.Srolovitz: Journal of Applied Physics, 1998, 83[1], 217-27