Molecular dynamics simulation of silicon nanoparticle crystallization during laser-induced forward transfer printing

Abstract

Laser-induced forward transfer (LIFT) printing is a versatile technique to realize micro/nano-scale additive manufacturing of functional materials, including metals and semiconductors. However, the crystallization phenomena during LIFT printing have not been well understood, which is critical to determine the resulting microstructure and properties. In this work, we systematically investigate silicon crystallization during LIFT printing using molecular dynamics (MD) simulations. Specifically, MD simulation with Stillinger-Weber (SW) potential is used to investigate the size effect and surface influence on the crystallization of Si nanoparticles during transportation in air. We found that with a decrease in nanoparticle size, crystallization becomes increasingly rare, even at low cooling rates. The nucleation location of different particles is also analyzed and almost always starts at a sub-surface location (below 5 Å). The evolution of the atomic structure during solidification is also monitored to guide LIFT printing of Si. Our simulation results indicate that nano-confinement induced by the surface layer can lead to single-crystal structure formation, which may shed light on additive manufacturing of single-crystal structures and devices.