Compositional patterning in immiscible alloys driven by irradiation - art.no. 134111

Ion-beam mixing of immiscible alloys is viewed as a competing dynamic proce ss, where irradiation-induced mixing opposes thermal decomposition. The ext ernal perturbation drives the system away from equilibrium, and in the long -time regime the system can exhibit phase and microstructural modifications . Due to the nonequilibrium nature of the process, the steady state depends explicitly on the details of the interplay between irradiation and the int ernal kinetics of the alloy. In particular, we have recently developed a co ntinuum model that takes into account the finite range of atomic relocation s during collision cascades [R. A. Enrique and P. Bellon, Phys. Rev. Lett. 84, 2885 (2000)]. Using this model, we have shown that self-organized compo sitional patterns can spontaneously appear if the range of atomic relocatio ns is large enough, and we have introduced a dynamical phase diagram descri bing the steady state regimes as a function of the forcing and material par ameters. In this paper we follow up with the analysis of the continuum mode l, and we consider the problem of fluctuations. In order to study the pheno menology and test the predictions, we perform kinetic Monte Carlo simulatio ns of an immiscible binary alloy undergoing finite-range atomic relocations . The simulations show that compositional patterns at the nanometer scale c an indeed be stabilized, and that the behavior of those patterns as a funct ion of the control parameters can be suitably described by our continuum mo del, and previous theory of fluctuations in driven alloys. The results corr oborate the idea that irradiation can be used as a processing tool to synth esize nanostructures.