(627c) Molecular Dynamics Investigation of Crystal-Melt Interface Kinetics and Its Stability Limits during Horizontal Ribbon Growth of Silicon

Horizontal ribbon growth (HRG) is an emerging method currently being developed for the fabrication of high-quality and low-cost single-crystal silicon wafers for solar cells. This work intends to improve the fundamental knowledge of HRG processes by modeling a continuous silicon crystal growth from molecular dynamics (MD) using the forced velocity solidification (FVS) approach. We studied growth modes of Si(100) and steps vicinal to Si(111) at high pulling speeds (~0.005 – 0.05 Å/ps), determined kinetics from interface temperature free of thermostatic effects, and investigated the stability of growth kinetics at high growth rates. We predicted kinetic coefficients from precise interface temperature facilitated by the FVS method, which increased kinetic coefficients for rough and stepped growths by ~40%. Also, we report an increase in step kinetic coefficient as step-size increased and a break-down of step propagation at a large step size of 23.10 Å due to the onset of interface roughening. The thermal gradients analysis across the melt and crystal parts of the interface suggests that interface roughening develops at higher pull speeds when the liquid's heat gradient is significantly low. Finally, we show that crystal-melt interface instabilities appear in the form of grain boundary grooves that served as nucleation sites for the formation of stacking faults and dislocations at undercooling as low as ~4 K—a value lower than previously observed from molecular dynamics.