(181o) Unraveling the Mechanisms of Crystal Nucleation and Growth At the Nanoscale

We discuss results recently obtained on crystal nucleation and growth in metals and alloys as well as in semiconductors. In the case of metals, we apply our approach to the formation of nanocrystallites in single-components systems as well as in binary systems. More specifically, we show how our approach accounts for the formation of gold nanoparticles exhibiting twinned FCC crystals as observed in experiments. We also unravel the interplay between the composition and the crystalline structure during the nucleation and growth of Pd-Ni nanoparticles. In the case of semiconductors, we show how the nucleation of a crystalline nucleus of silicon is preceded by the formation of a nanosized droplet of a metastable low density liquid precursor. We also show that the formation of the crystalline nucleus subsequently occurs at the interface between the two liquid phases. This result suggests that theories, like the classical nucleation theory, and empirical rules, like Ostwald's rule, should be modified to account for the role of liquid polymorphs in the nucleation process.