Two-level ablation and damage morphology of Ru films under femtosecond extreme UV irradiation

0540252 - ÚFP 2021 RIV NL eng J - Journal Article
Milov, I. - Zhakhovsky, V. - Ilnitsky, D. - Migdal, K. - Khokhlov, V. - Petrov, Y. - Inogamov, N. - Lipp, V. - Medvedev, Nikita - Ziaja, B. - Medvedev, V. - Makhotkin, I.A. - Louis, E. - Bijkerk, F.
Two-level ablation and damage morphology of Ru films under femtosecond extreme UV irradiation.
Applied Surface Science. Roč. 528, October (2020), s. 1-18, č. článku 146952. ISSN 0169-4332. E-ISSN 1873-5584
R&D Projects: GA MŠMT LTT17015; GA MŠMT(CZ) LM2015083
EU Projects: European Commission(XE) 654148 - LASERLAB-EUROPE
Institutional support: RVO:61389021
Keywords : Extreme ultraviolet * Femtosecond laser ablation * Free-electron laser * Molecular dynamics * Monte Carlo * Thin films
OECD category: Fluids and plasma physics (including surface physics)
Impact factor: 6.707, year: 2020
Method of publishing: Open access
https://www.sciencedirect.com/science/article/pii/S0169433220317098?via%3Dihub

The dynamics of a thin ruthenium film irradiated by femtosecond extreme UV laser pulses is studied with a hybrid computational approach, which includes Monte Carlo, two-temperature hydrodynamics and molecular dynamics models. This approach is capable of accurate simulations of all stages of material evolution induced by extreme UV or X-ray photons: from nonequilibrium electron kinetics till complete lattice relaxation. We found that fast energy deposition in a subsurface layer leads to a two-level ablation: the top thin layer is ablated as a gas–liquid mixture due to expansion of overheated material at near and above critical conditions, whereas a thicker liquid layer below is ablated via a cavitation process. The latter occurs due to a thermo-mechanically induced tensile pressure wave. The liquid ablating layer exhibits unstable behaviour and disintegrates into droplets soon after detachment from the rest of the target. Our simulations reveal basic processes leading to formation of specific surface morphologies outside and inside the damage craters. The calculated ablation threshold, crater depth and morphological features are in quantitative agreement with the experimental data, which justifies the applicability of our hybrid model to study laser-induced material damage.
Permanent Link: http://hdl.handle.net/11104/0317887