CC BY
24LMI-I-14
Laser made random and solitary surface structures
N. Inogamov1,2, V. Zhakhovsky1, S. Anisimov2, Y. Petrov2, V. Khokhlov2 1The Dukhov Research Institute of Automatics,
The Centre for Fundamental and Applied Research, Moscow, Russian Federation 2Landau Institute for Theoretical Physics of the Russian Academy of Sciences, Lasers and Plasma, Chernogolovka- Moscow region, Russian Federation
Studies in physics of a laser-matter interaction are necessary for optimization for several modern technologies. There are printing technologies like LIFT (laser induced forward transfer) and LIBT (laser induced backward transfer) [1]; LAL - laser ablation in liquid as the ecologically clean way for nanoparticles production [2]; LSP - laser shock peening for improvement of quality of materials; and fabrication of multipurpose metasurfaces [3]. There are two ways of fabrication of the metasurfaces. One of them is connected with creation of a tiny (its size along a target surface is ~ micron) solitary "cupola" by a diffraction limited ultrashort laser action; we use a term "cupola" here as the generalizing name because it may be a cupola, or cupola with a jet above in its tip, or hole in a film; usually a target is a thin film mounted on dielectric substrate. We create a matrix of the cupolas repeating placing of them on a film in the desired points. This matrix changes surface properties of a target thus transferring the usual surface into a metasurface.
Wide beam and ultrashort action are used on the second way to fabricate a metasurface. In this case (illuminating above an ablation threshold) a random surface micro- nano-structures appears first described in the papers by Vorobyev and Guo [4]. Creation of solitary and random structures are connected with many physical processes: there are hydrodynamic and dynamic of deformable solids phenomena including strong heating and cooling with phase transitions which convert (a) solids to liquid therefore the capillary effects become dynamically important, (b) rarefactions, tensile stress, fragmentation, formation of the three-phase (solid-liquid-vapour) mixtures, evaporation, foaming of hot liquid metals, (c) conductive cooling, re-crystallization in motion.
Laser action inevitably creates shocks. The LSP technologies are based on that. The shocks have to be strong enough (above limits of plasticity) to cause the irremovable deformation in solids. Therefore physics of laser initiated shocks in elastic-plastic media (ductile metals) have to be studied [5].
Laser ablative action in liquid generates a chain of processes covering many orders of magnitudes in space and time. Initial stages significantly depend on duration of a pulse and absorbed energy. They cause foaming of metal in the case of picosecond pulses. While in the case of a nanosecond action the foam is absent. To produce nanoparticles the heating have to be strong. There are significant differences between the situations when a target is heated below its critical parameters and above. In the last case the surface tension at a contact boundary between a target material and liquid disappears. Thus mutual diffusion is enhanced. The dissolved target atoms filling the diffusion layer are cooled down (because the surrounding liquid is colder) and begin to condense [2].
References
[1] C. Unger et al., Opt. Express 20, 24864 (2012); N. Inogamov et al., Journal of Experimental and
Theoretical Physics, Vol. 120, No. 1, pp. 15-48 (2015)
[2] D. Zhang et al., Chem Rev. 117(5), 3990-4103 (2017). doi:10.1021/acs.chemrev.6b00468; Yu. Petrov et al., Contributions to Plasma Physics, e419, First published: 15 May 2019. doi: 10.1002/ctpp.201800180 (2019); arXiv:1812.09929; arXiv:1812.09109; arXiv:1811.11990
[3] A. Kuchmizhak et al., Nanoscale 8, 12352-12361 (2016). DOI: 10.1039/C6NR01317AN; Inogamov et al., Applied Physics A: Material Science and Processing 122, 432 (9 pages) (2016). DOI 10.1007/s00339-016-9942-9X; Wang et al., Phys. Rev. Appl. 8, 044016 (2017)
[4] A. Vorobyev and C. Guo, J Appl Phys 110, 043102 (2011)
[5] M. Agranat et al., JETP Lett. 91 (9), 471-477 (2010); S. Ashitkov et al., JETP Lett. 92 (8), 516-520
(2010); V. Zhakhovskii and N. Inogamov, JETP Lett., 92 (8), 521-526 (2010); N. Inogamov et al., JETP Letters, v. 93 (4), 226-232 (2011); V. Zhakhovsky et al., Phys. Rev. Lett., v. 107, 135502
(2011); B. Albertazzi et al., Sci. Adv. 3, e1602705 (2017)
