Molecular dynamics simulations were used to investigate the mechanical response to high-dose ion bombardment. They were also used to simulate the beam-induced amorphization. It was found that the behavior of the irradiated material was related to the rate at which it could relax. Depending upon the ability to deform, either the generation of a high compressive stress and subsequent expansion of the material, or the generation of tensile stresses and densification, were observed. It was noted that properties such as the radial distribution function were insufficient to differentiate between differing densities of amorphous samples. At reasonable deformation rates, an expansion of the target during amorphization was observed; in agreement with experimental observations. This contrasted with the results of quenching simulations, which usually resulted in denser structures relative to the crystalline material. It was concluded that, although there was appreciable agreement between experimental data and simulation results, amorphous structures could exhibited fundamental differences. A difference in density could be attributed to local defects within the amorphous network. It was shown that annealing simulations of amorphized samples could lead to a reduction in the number of high-energy local defects; without large-scale rearrangement of the amorphous network. This confirmed that defects in the amorphous material were analogous to those in the crystalline silicon.

Direct Simulation of Ion-Beam-Induced Stressing and Amorphization of Silicon K.M.Beardmore, N.Grønbech-Jensen: Physical Review B, 1999, 60[18], 12610-6