Session: 17-01-01: Research Posters

Paper Number: 150473

150473 - Molecular Dynamics (Md) Simulation of Silicon Nanoparticle Crystallization During Laser-Induced (Lift) Printing 

Due to the wide applications in microelectronics, photonics, and computing, silicon (Si) is still one of the most important semiconductors. Although various manufacturing techniques have been developed for Si, additive manufacturing of Si is underexplored. Among various Si crystallization processes, lasers have shown great versatility in patterning without mask. Yet, direct printing of crystalline Si, especially, single-crystal Si, in an additive approach remains challenging. Recently, laser-induced forward transfer (LIFT) printing has emerged as a versatile technique for the precise deposition of various materials, including metals, polymers, and semiconductors. It also has shown good printability of Si. However, the understanding of the Si phase transformation during printing is limited, which prevents us from controlling the crystallization process for single-crystal Si printing. Here, we investigate the nucleation and crystallization evolution of Si nanodroplets during the flying in air with molecular dynamics (MD) simulations. A classical interatomic potential, Stillinger-Webe (SW) potential, is employed to model the interactions between Si atoms. To identify the crystalline Si atoms, a bond order parameter method is used. Different droplet sizes and processing conditions are systematically studied to understand the Si solidification in air during the printing. Specifically, the nanoconfinement effect is investigated to reveal their influence on the nucleation and crystallization process. The critical nucleus is monitored during the solidification, which gives us a good understanding of the atomic transport trajectory. Mathematical and statistical relationships are established to correlate the size (atom number) with solidification temperature. It is found that the latent heat release plays a critical role for the crystalline formation. In order to establish a comprehensive understanding of the size effect, we also simulate the melting phenomena of Si with different sizes. The relationship between melting and solidification is further explored with different particle sizes. Furthermore, we monitor the surface tension change during the crystallization, and their influence on nucleation is analyzed. It is observed that nucleation tends to start from the sub-surface while crystal growth prefers to take place near the particle center. We find by tuning the cooling rate, single crystal Si nanoparticles can be obtained; while the possibility of forming single crystal Si is also affected by several other critical factors, including size and undercooling temperature. Through a comprehensive study, we hope to gain in-depth understanding of the nucleation and crystallization process during LIFT printing of Si. It is believed such findings will help researchers design better experimental procedures for additive manufacturing of Si, which will also be meaningful for other materials printing. 

Presenting Author: Youwen Liang University of Arkansas

Presenting Author Biography: Youwen Liang is a recent PhD student in the Department of Mechanical Engineering at University of Arkansas, where he works in Dr. Wan Shou’s research group on laser-based advanced manufacturing and soft robotics.

Authors:

Youwen Liang University of Arkansas
Wan Shou University of Arkansas