Surface Crystallization of Liquid Au-Si and Its Impact on Catalysis.

Abstract

In situ transmission electron microscopy reveals that an atomically thin crystalline phase at the surface of liquid Au–Si is stable over an unexpectedly wide range of conditions. By measuring the surface structure as a function of droplet temperature and composition, a simple thermodynamic model is developed to explain the stability of the ordered phase. The results show that the presence of surface ordering plays a key role in the pathway by which the Au–Si eutectic solidifies and also dramatically affects the catalytic properties of the liquid, explaining the anomalously slow growth kinetics of Si nanowires at low temperature. A strategy to control the presence of the surface phase is discussed, using it as a tool in designing strategies for nanostructure growth.