Programme

P.12 -- Poster, ANSWCCMS-2023

Date: Tuesday, 7 November 2023

Time: 13:00 - 14:30

Numerical Investigation of Heat Transfer in Ultrafast Laser Processing of Silicon Material

De Mesa, Joseph A. (1), Dasallas, Lean (2), and Garcia, Wilson O. (1)

(1) National Institute of Physics, University of the Philippines - Diliman, (2) Material Science and Engineering, University of the Philippines - Diliman

Processing materials using low-energy, high-repetition-rate ultrafast laser poses a challenging problem in the ablation of materials. Understanding the primary ablation mechanism at this laser condition is essential for properly designing the laser processing experiments. Using numerical simulation, we investigated free-electron generation and heat dynamics in a semiconductor material when irradiated by a low-energy high-repetition-rate ultrafast laser. The numerical simulation was based on a density-dependent two-temperature model (nTTM). We use a narrow gap silicon (Si) as the model target to consider both generations, free-electron generation via linear and non-linear absorption and lattice heating. We showed that the nTTM simulation could predict thermal and non-thermal ablation depending on the choice of laser fluence F. Non-thermal ablation can be expected at specific laser fluence by investigating the maximum free-electron number density and the lattice temperature. The numerical simulation continued to multi-pulse fs-laser cases involving high-repetition laser pulses. The nTTM simulation showed that the slow heat dissipation in lattice results in accumulated heat that is enhanced by the arrivals of multiple pulses with short pulse delay. Low energy fs-laser can induce material ablation when the series of laser pulses have a fast pulse delay (high repetition rate), quick enough for the Si lattice to cool down and diffuse the residual heat before the arrival of the next pulse. Heat dissipation on the material is strongly affected by the material's thermal conductivity. Semiconductors with lower thermal conductivity and smaller grains allow low heat dissipation and, thus, better ablation. The proposed numerical model is a promising tool for giving insights and determining the optimal laser parameters in semiconductor materials' laser ablation and thin film deposition. Our numerical results help us choose the appropriate semiconductor target for this laser source for the thin film deposition experiments.

Presenter: Joseph Aban De Mesa