CC BY
17LM-I-37
Ultrafast laser nanopatterning of metals below 100 nm
J.P. Colombier,1 A. Nakhoul,12 A. Rudenko,3 C. Maurice,2 F. Garrelie1, F. Pigeon,1
1- Univ Lyon, UJM-St-Etienne, CNRS, Institute of Optics Graduate School, Laboratoire Hubert Curien UMR 5516,
F-42023 Saint-Etienne, France
2- Ecole Nationale Supérieure des Mines de Saint-Etienne, Laboratoire Georges Friedel, CNRS, UMR5307, 42023
St-Etienne, France
3- Arizona Center for Mathematical Sciences and College of Optical Sciences, University of Arizona,
Tucson, AZ 85721, USA
jean.philippe.colombier@univ-st-etienne.fr
Ultrafast laser sources enable the structuring at the nanoscale driven by remarkable surface material response to photoexcitation involving extreme states of temperature and pressure far from equilibrium. During the lifetime of a transient laser-induced melting layer, we uncover that dissipative structures can emerge and continuously exchange energy and entropy with photonic flux to ensure relief growth and topographic organization upon solidification. Using a crossed-polarization irradiation strategy to prevent commonly oriented nanostripes formation, we report the formation of arranged laser-induced cavities and peaks well below the diffraction limit on metallic surfaces. Self-organized nanopatterns with various symmetries and aspect-ratios can be formed, demonstrating the potential of temporal beam shaping for the fabrication of advanced surfaces with a topography designed at the nanoscale [1-2].
Local field enhancement on local roughness fosters the energy absorption on the smallest dimensions much smaller than the light wavelength, resulting in extreme and inhomogeneous thermo-mechanical conditions. Fluctuations can be amplified upon positive feedback and trigger a convection instability at the nanoscale [3]. Destabilized forces arise from subtle contributions of Marangoni flows that follows transverse temperature gradients and longitudinal rarefaction shock wave relaxation. Distinct self-organization regimes can then result from this convection mechanism driven by light energy coupling on emerging surface patterns [4]. The surface and irradiation dose conditions required to switch from a self-organization regime to another one will be discussed based on experimental results interpreted by simulations coupling Maxwell solver to Navier-Stokes equations. Hydrodynamic instabilities, similar to the Rayleigh-Benard-Marangoni flows, drives the matter towards self-organized convection nanocells and can induce thermocapillary waves oriented by nonradiative sub-diffraction near-field patterns.
Figure 1: Crossed-polarized double pulse sequence for isotropic energy regulation. An hexagonal lattice of nanocavities of 20 nm in size ana spaced by 60 nm has been performed on (100) Ni surface.
[1] A. Abou Saleh, A. Rudenko, S. Reynaud, F. Pigeon, F. Garrelie, & J.P. Colombier, "Sub-100 nm 2D nanopatterning on large scale by ultrafast laser energy regulation", Nanoscale 12 (12), 6609 (2020).
[2] R. Stoian, & J.P. Colombier, "Advances in ultrafast laser structuring of materials at the nanoscale", Nanophotonics 9 (16), 4665-4688 (2020).
[3] A. Rudenko, A. Abou-Saleh, F. Pigeon, C. Mauclair, F. Garrelie, R. Stoian, & J. P. Colombier "High-frequency periodic patterns driven by non-radiative fields coupled with Marangoni convection instabilities on laser-excited surfaces" Acta Materiala 194, 93 (2020).
[4] A. Nakhoul, C. Maurice, M. Agoyan, A. Rudenko, F. Garrelie, F. Pigeon, & J.P. Colombier "Self-Organization Regimes Induced by Ultrafasl Laser on Surfaces in the Tens of Nanometer Scales". Nanomaterials, 11(4), 1020 (2021).
