Multiphysics Simulation of Melt-Pool Dynamics in Laser-Induced Liquid-Phase Crystallization of Ge
Laser-induced liquid phase crystallization (LLPC) forms crystalline Ge wires on insulators, but the micron-scale, microsecond-lived melt pool governing crystal quality is hard to observe directly.
We built a custom 3D COMSOL Multiphysics® model of a 440 mW Gaussian beam scanned at 100 mm/s over a 500 nm-thick Ge wire on SiO₂. No Application Library model was used. The Heat Transfer and CFD Modules couple heat transfer with latent heat via the apparent heat capacity method, laminar flow, moving-mesh free-surface tracking, and the Marangoni effect, with temperature-dependent Ge properties.
The model reproduces a moving comet-shaped temperature field, complete melt-through above 1211 K, and outward Marangoni flow from the hot center toward the cooler edges. It also identifies spurious surface uplift from Ge densification and unconstrained mesh motion in solidified regions on cooling. Mesh constraints and smoothing suppress this instability, providing a basis for LLPC optimization.
