Phase Field Model for Morphological Transition in Nanowire Vapor–Liquid–Solid Growth

The vapor–liquid–solid (VLS) method is widely used for nanowire (NW) synthesis. However, growth of irregular NW geometries is often observed, and the mechanisms responsible are not fully understood. In this article, we present a multiphase field model for studying NW morphological transition during the VLS growth. Introducing the chemical potential and an external perturbation force by means of the method of Lagrange multipliers, the position of the catalyst droplet and the volumetric growth rate of the NW can be precisely controlled in the model. This allows us to capture the morphology of NWs growing along metastable orientations and simulate the formation of complex NW structures. Additionally, with the model's ability to constrain the NW shape, the interface free energy change along designated droplet moving path can be evaluated, from which a free energy landscape for the catalyst droplet on top of a NW pedestal can be obtained.