CC BY
17LM-O-10
Numerical Modeling of Thermal Response of Molybdenum Thin Film on Different Substrates Irradiated by Short Laser Pulse
K. Hlinomaz1'2, Y. Levy1, T. J. Y. Derrien1 and N. M. Bulgakova1
1- HiLASE Centre, Institute of Physics of the Czech Academy of Sciences, Za Radnici 828, 25241 Dolni Brezany,
Czech Republic
2- Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Brehova 7,
115 19 Praha 1, Czech Republic
hlinomazk@fzu. cz
Heterostructures consisting of a thin metallic film deposited on a dielectric or semiconducting substrate are employed in a number of applications in the field of optoelectronics [1], photovoltaics [2], nanoparticle production [3] and in laser-induced forward transfer (LIFT) [4]. These thin films are often processed using ultra-short laser pulses. However, the type of substrate where they are deposited may affect the temperature evolution upon the laser exposure and the resulting structure.
In this work, numerical simulations based on two-temperature model (TTM) have been performed to study the effect of substrate on the thermal response of thin Mo film irradiated by a single laser pulse (wavelength 400 nm, pulse duration 200 fs at FWHM). The effect of three different dielectric substrates (fused silica, silicon, and soda-lime glass) was investigated in terms of temperature distribution and energy relaxation. For the same irradiation conditions, the results reveal different maximal temperatures achieved at the Mo-substrate interface for different substrates. In the case of fused silica substrate, the temperature at the interface can exceed its softening point with fluence even lower than the Mo thin film melting threshold. The softened state of fused silica can lead to the damage of the system at the Mo-substrate interface. A possible softening and corresponding compaction of fused silica was studied by systematically varying thickness of the film irradiated by laser pulses at the thickness-dependent melting threshold fluence. The time duration for which the substrate remains in its softened state has been calculated.
The numerical model, which includes temperature-dependent properties of substrate materials and molybdenum, was validated by controlling the energy conservation [5] and by comparing with the experimental melting threshold fluences of Mo films [4] for film thicknesses from 5 to 200 nm.
[1] A. D. Rakic, A. B. Djurisic, J. M. Elazar, M. L. Majewski, Optical properties of metallic films for vertical-cavity optoelectronic devices, Applied Optics, 37, 22 5271-5283, (1998).
[2] S. Zoppel, H. Huber, G.A. Reider, Selective ablation of thin Mo and TCO films with femtosecond laser pulses for structuring thin film solar cells, Applied Physics A, 89, 1 161-163, (2007).
[3] S. J. Henley, J. D. Carey, S. R. P.Silva, Metal nanoparticle production by pulsed laser nanostructuring of thin metal films, Applied Surface Science, 253, 19 8080-8085, (2007).
[4] M. Domke, S. Rapp, M. Schmidt, H. P. Huber, Ultra-fast movies of thin-film laser ablation, Applied Physics A, 109, 2 409-420 (2012).
[5] K. Hlinomaz, Y. Levy, T. J.-Y. Derrien, N. M. Bulgakova, Modeling the melting threshold of Mo films upon ultrashort laser irradiation, Modern Machinery (MM) Science Journal, Dec. 2019, 3585-3593 (2019).
