PHASE-FIELD CRYSTAL MODELING OF NANOCRYSTAL GROWTH

Edwin J. Schwalbach, James A. Warren, Kuo-An Wu, and Peter W. Voorhees

The Phase-Field Crystal (PFC) model is a relatively new form of the phase-field continuum model capable of simulating crystal growth. PFC models naturally incorporate the effects of elasticity and crystal anisotropy, as well as topological defects such as dislocations and grain boundaries. Recent work has extended this model to the diamond cubic crystal structure relevant to semiconductor growth. This combination of physical effects as well as the atomic length and diffusive time scales accessible to PFC models make them a natural choice to study nanocrystal growth scenarios such as Vapor-Liquid-Solid (VLS) nanowire growth.

Existing PFC models include liquid and crystal phases, but we have developed a variation of the PFC model that adds a vapor phase. This addition allows us to investigate the dynamic behaviors and interactions between faceted solid-vapor, solid-liquid, and liquid-vapor interfaces and vapor-liquid-solid trijunctions. We first describe the model's ability to reproduce various interface properties important to VLS growth. Then, we examine the VLS trijunction and its effect on the motion and shape of solid-liquid interfaces during solidification and describe implications for VLS nanowire growth. Finally, we will address grain-boundaries within nanowires and their effect on the solid-liquid interface.