Intermixing during Ripening in Ge–Si Incoherent Epitaxial Nanocrystals

Abstract

Ostwald ripening is an interesting phenomenon that takes place in a variety of systems in nature, including nanostructured materials. A large number of nanoscale systems are formed by a mixture, which has to be considered for a realistic description of its evolution upon equilibrium. Here, a thermodynamic-based model is used to explain the intermixing contribution to Ostwald ripening phenomenon in a two-components system (AxB1–x). By considering the mixing entropy on the general growth rate equation of particles, ripening is maximized for an alloy with x = 0.5. As an example, Ge–Si incoherently strained epitaxial islands were analyzed. A selective chemical etching was used to reveal the complex effect of intermixing in islands' final composition profile. Alloying was found to take place primarily through surface diffusion, as revealed by the etching experiments.