Generation of micro- and nano-morphologies on a stainless steel surface irradiated with 257 nm femtosecond laser pulses

Abstract

a Surface structuring by femtosecond lasers has emerged as an efficient tool to functionalize the surfaces of various solid materials. Laser induced periodic surface structures (LIPSS) can drastically impact the wetting, friction and optical properties of the surface depending on the size, aspect ratio and period of the structures. Morphological characteristics in the nanoscale, such as nano roughness, contributing to a hierarchical surface formation are considered to have a significant impact on those properties. In this study, we demonstrate for the first time to our knowledge the feasibility of inducing ripples and spikes utilizing a 257 nm femtosecond laser. LIPSS with a period smaller than 200 nm were realised.Furthermore, we show the evolution of those structures into conical spikes for this wavelength, and we provide an interpretation on their formation. Finally, we show that sub 200 nm LIPSS can create subwavelength gratings providing non-angular dependent light reflection and non-periodic morphologies showing super hydrophobic behaviour.

High-frequency periodic patterns driven by non-radiative fields coupled with Marangoni convection instabilities on laser-excited metal surfaces

“…12(b). Between the LSFL crests, smaller structures are formed parallel to laser polarization with periods ≈ 200 nm, resembling crossoriented HSFL commonly observed in experiments [21,22,43,59,68,69]. We note that the energy is absorbed in the hollows of the LSFL structures mostly perpendicular to laser polarization, amplifying the pre-existent gratings.…”

“…The formation of microstructures such as grooves and spikes was then explained by Tsibidis et al based on the solution of incompressible Navier-Stokes equations, indicating the generation of hydrothermal waves and convection rolls for low and high Prandtl number fluids accordingly due to thermal gradients created by previously formed LSFL [39,40]. Nevertheless, the existing models fail to explain the formation of regular HSFL with orientations both perpendicular and parallel to laser polarization and periods down to λ/15 on metal surfaces [22,43], as well as more complex morphologies, consisting of hierarchical periodic surface structures [19,21,22,43,59,60,[67][68][69] and quasihexagonal arrangements [36, 47, 49-53, 70, 71]. For instance, the transitions between HSFL and LSFL are contradictory discussed in the literature, where both lithographic scenarios, based on electromagnetic field enhancement between regular rectangu-lar grooves and period reduction or grating splitting [57,[72][73][74][75], and hydrodynamic scenarios based on the instability [48,59,60] were proposed.…”

“…Additionally, a variety of HSFL periods different from half of LSFL periods were reported, with HSFL at the border of laser-affected zone, where less energy is deposited [22,43,76,77]. Regarding the hexagonal nano-and microstructure selforganization, several plausible scenarios were proposed revealing similarities with Bénard-Marangoni or other convective instabilities [47,53,69,71], but also dewetting in thin liquid films [50], and Rayleigh-Taylor instabilities [30,36,49]. To our best knowledge, none of these scenarios have been verified by numerical modeling.…”

Femtosecond-Laser Nanostructuring of Black Diamond Films under Different Gas Environments

“…In recent years, lots of research activities have been reported on LIPSS, which represent a versatile and practical way to functionalize the surface of metals [ 9 , 10 , 11 , 12 , 13 ], dielectrics [ 14 , 15 , 16 ] and semiconductors [ 17 , 18 , 19 ]. Current applications of LIPSS span from the control of surface wetting to the tailoring of surface colonization by bacterial biofilms, from the improvement of the tribological performance of nanostructured metal surfaces to the efficient water-oil separation in marine oil spills [ 20 ].…”

Пластическая Деформация Меди В Результате Воздействия Мощного Ультрафиолетового Наносекундного Лазерного Импульса

“…Наносекундные импульсы УФ-лазера способны модифицировать поверхность металла, существенно изменяя его поверхностные свойства [1][2][3][4]. Диффузионная сварка металлов, обработанных подобным образом, заметно улучшается благодаря интенсификации диффузионных процессов в зоне контакта соединяемых поверхностей [5].…”