Special Issue "Laser-Generated Periodic Nanostructures"

A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "Synthesis, Interfaces and Nanostructures".

Deadline for manuscript submissions: 31 March 2021.

Special Issue Editors

Dr. Peter Simon
Website
Guest Editor
Laser-Laboratorium Göttingen e.V., Hans-Adolf-Krebs-Weg 1, D-37077 Göttingen, Germany
Interests: periodic nanostructures; nanostructure formation by ultrashort laser pulses; laser interference ablation; diffractive beam management; compression of ultrashort laser pulses at high power levels
Dr. Jürgen Ihlemann
Website
Guest Editor
Laser-Laboratorium Göttingen e.V., Hans-Adolf-Krebs-Weg 1, D-37077 Göttingen, Germany
Interests: laser ablation; surface patterning; thin film patterning; transparent materials; periodic nanostructures; nanoparticles
Dr. Jörn Bonse
Website
Guest Editor
Bundesanstalt für Materialforschung und -prüfung (BAM), Berlin, Germany
Interests: laser–matter interaction; femtosecond laser technology; laser ablation; ultrashort laser pulses and applications; micro- and nano-structured surfaces; tribological properties of laser-textured surfaces; biomimetics; ultrafast microscopy; time-resolved spectroscopy; plasmonics; laser processes in photovoltaics; laser safety
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

The study of laser fabricated periodic nanostructures is one of the leading topics of today’s photonics research. Such structures on the surface of metals, semiconductors, dielectrics or polymers can generate new material properties with special functionalities. Depending on the specific material parameters and the morphology of the structures, new devices like microlasers, optical nanoswitches, optical storage devices, biosensors or antifraud features can be realized. Furthermore, surface textures can be used to improve the tribological properties of special tools for the reduction of friction losses or wear, to modify the wettability or the cell and biofilm growth properties of surfaces or as decoration elements for the refinement of precious goods.

This Special Issue focuses on the latest theoretical developments and practical applications of laser-induced periodic surface structures that can be generated in a self-organized way (LIPSS, ripples) or via laser interference ablation. It aims to attract both academic and industrial researchers in order to foster the current knowledge of nanomaterials and to present new ideas for future applications and new technologies.

Dr. Peter Simon
Dr. Jürgen Ihlemann
Dr. Jörn Bonse
Guest Editors

Manuscript Submission Information

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Keywords

  • Periodic surface pattern
  • Laser ablation
  • Laser induced structures Beam interference
  • Periodic nanostructure
  • Surface ripples
  • Laser-induced periodic surface structures (LIPSS)
  • Self-organization
  • Laser applications

Published Papers (12 papers)

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Research

Open AccessFeature PaperArticle
Icephobic Performance of Multi-Scale Laser-Textured Aluminum Surfaces for Aeronautic Applications
Nanomaterials 2021, 11(1), 135; https://doi.org/10.3390/nano11010135 - 08 Jan 2021
Abstract
Ice-building up on the leading edge of wings and other surfaces exposed to icing atmospheric conditions can negatively influence the aerodynamic performances of aircrafts. In the past, research activities focused on understanding icing phenomena and finding effective countermeasures. Efforts have been dedicated to [...] Read more.
Ice-building up on the leading edge of wings and other surfaces exposed to icing atmospheric conditions can negatively influence the aerodynamic performances of aircrafts. In the past, research activities focused on understanding icing phenomena and finding effective countermeasures. Efforts have been dedicated to creating coatings capable of reducing the adhesion strength of ice to a surface. Nevertheless, coatings still lack functional stability, and their application can be harmful to health and the environment. Pulsed laser surface treatments have been proven as a viable technology to induce icephobicity on metallic surfaces. However, a study aimed to find the most effective microstructures for reducing ice adhesion still needs to be carried out. This study investigates the variation of the ice adhesion strength of micro-textured aluminum surfaces treated using laser-based methods. The icephobic performance is tested in an icing wind tunnel, simulating realistic icing conditions. Finally, it is shown that optimum surface textures lead to a reduction of the ice adhesion strength from originally 57 kPa down to 6 kPa, corresponding to a relative reduction of ~90%. Consequently, these new insights will be of great importance in the development of functionalized surfaces, permitting an innovative approach to prevent the icing of aluminum components. Full article
(This article belongs to the Special Issue Laser-Generated Periodic Nanostructures)
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Open AccessFeature PaperArticle
Microfabrication and Surface Functionalization of Soda Lime Glass through Direct Laser Interference Patterning
Nanomaterials 2021, 11(1), 129; https://doi.org/10.3390/nano11010129 - 08 Jan 2021
Abstract
All-purpose glasses are common in many established and emerging industries, such as microelectronics, photovoltaics, optical components, and biomedical devices due to their outstanding combination of mechanical, optical, thermal, and chemical properties. Surface functionalization through nano/micropatterning can further enhance glasses’ surface properties, expanding their [...] Read more.
All-purpose glasses are common in many established and emerging industries, such as microelectronics, photovoltaics, optical components, and biomedical devices due to their outstanding combination of mechanical, optical, thermal, and chemical properties. Surface functionalization through nano/micropatterning can further enhance glasses’ surface properties, expanding their applicability into new fields. Although laser structuring methods have been successfully employed on many absorbing materials, the processability of transparent materials with visible laser radiation has not been intensively studied, especially for producing structures smaller than 10 µm. Here, interference-based optical setups are used to directly pattern soda lime substrates through non-lineal absorption with ps-pulsed laser radiation in the visible spectrum. Line- and dot-like patterns are fabricated with spatial periods between 2.3 and 9.0 µm and aspect ratios up to 0.29. Furthermore, laser-induced periodic surface structures (LIPSS) with a feature size of approximately 300 nm are visible within these microstructures. The textured surfaces show significantly modified properties. Namely, the treated surfaces have an increased hydrophilic behavior, even reaching a super-hydrophilic state for some cases. In addition, the micropatterns act as relief diffraction gratings, which split incident light into diffraction modes. The process parameters were optimized to produce high-quality textures with super-hydrophilic properties and diffraction efficiencies above 30%. Full article
(This article belongs to the Special Issue Laser-Generated Periodic Nanostructures)
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Open AccessArticle
Femtosecond Laser-Induced Periodic Surface Structures on Different Tilted Metal Surfaces
Nanomaterials 2020, 10(12), 2540; https://doi.org/10.3390/nano10122540 - 17 Dec 2020
Abstract
Laser-induced periodic surface structures (LIPSS) are used for the precision surface treatment of 3D components. However, with LIPSS, the non-normal incident angle between the irradiated laser beam and the specimen surface occurs. This study investigated LIPSS on four different metals (SUS 304, Ti, [...] Read more.
Laser-induced periodic surface structures (LIPSS) are used for the precision surface treatment of 3D components. However, with LIPSS, the non-normal incident angle between the irradiated laser beam and the specimen surface occurs. This study investigated LIPSS on four different metals (SUS 304, Ti, Al, and Cu), processed on a tilted surface by an s-polarized femtosecond fiber laser. A rotated low spatial frequency LIPSS (LSFL) was obtained on SUS 304 and Ti materials by the line scanning process. However, LSFL on Cu and Al materials was still perpendicular to the laser polarization. The reason for the rotated and un-rotated LSFL on tilted metal surfaces was presented. The electron-phonon coupling factor and thermal conductivity properties might induce rotational LSFL on tilted SUS 304 and Ti surfaces. When fabricating LSFL on an inclined plane, a calibration model between the LSFL orientation and inclined plane angle must be established. Hence, the laser polarization direction must be controlled to obtain suitable LSFL characteristics on a 3D surface. Full article
(This article belongs to the Special Issue Laser-Generated Periodic Nanostructures)
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Open AccessArticle
Response of NIH 3T3 Fibroblast Cells on Laser-Induced Periodic Surface Structures on a 15×(Ti/Zr)/Si Multilayer System
Nanomaterials 2020, 10(12), 2531; https://doi.org/10.3390/nano10122531 - 16 Dec 2020
Abstract
Ultrafast laser processing with the formation of periodic surface nanostructures on the 15×(Ti/Zr)/Si multilayers is studied in order to the improve cell response. A novel nanocomposite structure in the form of 15×(Ti/Zr)/Si multilayer thin films, with satisfying mechanical properties and moderate biocompatibility, was [...] Read more.
Ultrafast laser processing with the formation of periodic surface nanostructures on the 15×(Ti/Zr)/Si multilayers is studied in order to the improve cell response. A novel nanocomposite structure in the form of 15×(Ti/Zr)/Si multilayer thin films, with satisfying mechanical properties and moderate biocompatibility, was deposited by ion sputtering on an Si substrate. The multilayer 15×(Ti/Zr)/Si thin films were modified by femtosecond laser pulses in air to induce the following modifications: (i) mixing of components inside of the multilayer structures, (ii) the formation of an ultrathin oxide layer at the surfaces, and (iii) surface nano-texturing with the creation of laser-induced periodic surface structure (LIPSS). The focus of this study was an examination of the novel Ti/Zr multilayer thin films in order to create a surface texture with suitable composition and structure for cell integration. Using the SEM and confocal microscopies of the laser-modified Ti/Zr surfaces with seeded cell culture (NIH 3T3 fibroblasts), it was found that cell adhesion and growth depend on the surface composition and morphological patterns. These results indicated a good proliferation of cells after two and four days with some tendency of the cell orientation along the LIPSSs. Full article
(This article belongs to the Special Issue Laser-Generated Periodic Nanostructures)
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Open AccessArticle
Surface Superconductivity Changes of Niobium Sheets by Femtosecond Laser-Induced Periodic Nanostructures
Nanomaterials 2020, 10(12), 2525; https://doi.org/10.3390/nano10122525 - 16 Dec 2020
Abstract
Irradiation with ultra-short (femtosecond) laser beams enables the generation of sub-wavelength laser-induced periodic surface structures (LIPSS) over large areas with controlled spatial periodicity, orientation, and depths affecting only a material layer on the sub-micrometer scale. This study reports on how fs-laser irradiation of [...] Read more.
Irradiation with ultra-short (femtosecond) laser beams enables the generation of sub-wavelength laser-induced periodic surface structures (LIPSS) over large areas with controlled spatial periodicity, orientation, and depths affecting only a material layer on the sub-micrometer scale. This study reports on how fs-laser irradiation of commercially available Nb foil samples affects their superconducting behavior. DC magnetization and AC susceptibility measurements at cryogenic temperatures and with magnetic fields of different amplitude and orientation are thus analyzed and reported. This study pays special attention to the surface superconducting layer that persists above the upper critical magnetic field strength Hc2, and disappears at a higher nucleation field strength Hc3. Characteristic changes were distinguished between the surface properties of the laser-irradiated samples, as compared to the corresponding reference samples (non-irradiated). Clear correlations have been observed between the surface nanostructures and the nucleation field Hc3, which depends on the relative orientation of the magnetic field and the surface patterns developed by the laser irradiation. Full article
(This article belongs to the Special Issue Laser-Generated Periodic Nanostructures)
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Open AccessArticle
Formation of the Submicron Oxidative LIPSS on Thin Titanium Films During Nanosecond Laser Recording
Nanomaterials 2020, 10(11), 2161; https://doi.org/10.3390/nano10112161 - 29 Oct 2020
Cited by 1
Abstract
Laser-induced periodic surface structures (LIPSSs) spontaneously appearing on the laser-treated (melted or evaporated) surfaces of bulk solid materials seem to be a well-studied phenomenon. Peculiarities of oxidative mechanisms of LIPSS formation on thin films though are far less clear. In this work, the [...] Read more.
Laser-induced periodic surface structures (LIPSSs) spontaneously appearing on the laser-treated (melted or evaporated) surfaces of bulk solid materials seem to be a well-studied phenomenon. Peculiarities of oxidative mechanisms of LIPSS formation on thin films though are far less clear. In this work, the appearance of oxidative LIPSSs on thin titanium films was demonstrated under the action of commercially available nanosecond-pulsed Yb-fiber laser. The temperature and energy regimes favoring their formation were revealed, and their geometric characteristics were determined. The period of these LIPSSs was found to be about 0.7 λ, while the modulation depth varied between 70 and 110 nm, with high stability and reproducibility. It was shown that LIPSS orientation is rather easily manageable in the regimes of our interest, which could provide a way of controlling their properties. Full article
(This article belongs to the Special Issue Laser-Generated Periodic Nanostructures)
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Open AccessArticle
Formation of Periodic Nanoridge Patterns by Ultrashort Single Pulse UV Laser Irradiation of Gold
Nanomaterials 2020, 10(10), 1998; https://doi.org/10.3390/nano10101998 - 10 Oct 2020
Cited by 1
Abstract
A direct comparison of simulation and experimental results of UV laser-induced surface nanostructuring of gold is presented. Theoretical simulations and experiments are performed on an identical spatial scale. The experimental results have been obtained by using a laser wavelength of 248 nm and [...] Read more.
A direct comparison of simulation and experimental results of UV laser-induced surface nanostructuring of gold is presented. Theoretical simulations and experiments are performed on an identical spatial scale. The experimental results have been obtained by using a laser wavelength of 248 nm and a pulse length of 1.6 ps. A mask projection setup is applied to generate a spatially periodic intensity profile on a gold surface with a sinusoidal shape and periods of 270 nm, 350 nm, and 500 nm. The formation of structures at the surface upon single pulse irradiation is analyzed by scanning and transmission electron microscopy (SEM and TEM). For the simulations, a hybrid atomistic-continuum model capable of capturing the essential mechanisms responsible for the nanostructuring process is used to model the interaction of the laser pulse with the gold target and the subsequent time evolution of the system. The formation of narrow ridges composed of two colliding side walls is found in the simulation as well as in the experiment and the structures generated as a result of the material processing are categorized depending on the range of applied fluencies and periodicities. Full article
(This article belongs to the Special Issue Laser-Generated Periodic Nanostructures)
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Open AccessArticle
Fabrication of Periodic Nanostructures on Silicon Suboxide Films with Plasmonic Near-Field Ablation Induced by Low-Fluence Femtosecond Laser Pulses
Nanomaterials 2020, 10(8), 1495; https://doi.org/10.3390/nano10081495 - 30 Jul 2020
Abstract
Silicon suboxide (SiOx, x ≈ 1) is a substoichiometric silicon oxide with a large refractive index and optical absorption coefficient that oxidizes to silica (SiO2) by annealing in air at ~1000 °C. We demonstrate that nanostructures with a groove [...] Read more.
Silicon suboxide (SiOx, x ≈ 1) is a substoichiometric silicon oxide with a large refractive index and optical absorption coefficient that oxidizes to silica (SiO2) by annealing in air at ~1000 °C. We demonstrate that nanostructures with a groove period of 200–330 nm can be formed in air on a silicon suboxide film with 800 nm, 100 fs, and 10 Hz laser pulses at a fluence an order of magnitude lower than that needed for glass materials such as fused silica and borosilicate glass. Experimental results show that high-density electrons can be produced with low-fluence femtosecond laser pulses, and plasmonic near-fields are subsequently excited to create nanostructures on the surface because silicon suboxide has a larger optical absorption coefficient than glass. Calculations using a model target reproduce the observed groove periods well and explain the mechanism of the nanostructure formation. Full article
(This article belongs to the Special Issue Laser-Generated Periodic Nanostructures)
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Open AccessFeature PaperArticle
Large-Area Fabrication of Laser-Induced Periodic Surface Structures on Fused Silica Using Thin Gold Layers
Nanomaterials 2020, 10(6), 1187; https://doi.org/10.3390/nano10061187 - 18 Jun 2020
Cited by 3
Abstract
Despite intensive research activities in the field of laser-induced periodic surface structures (LIPSS), the large-area nanostructuring of glasses is still a challenging problem, which is mainly caused by the strongly non-linear absorption of the laser radiation by the dielectric material. Therefore, most investigations [...] Read more.
Despite intensive research activities in the field of laser-induced periodic surface structures (LIPSS), the large-area nanostructuring of glasses is still a challenging problem, which is mainly caused by the strongly non-linear absorption of the laser radiation by the dielectric material. Therefore, most investigations are limited to single-spot experiments on different types of glasses. Here, we report the homogeneous generation of LIPSS on large-area surfaces of fused silica using thin gold layers and a fs-laser with a wavelength λ = 1025 nm, a pulse duration τ = 300 fs, and a repetition frequency frep = 100 kHz as radiation source. For this purpose, single-spot experiments are performed to study the LIPSS formation process as a function of laser parameters and gold layer thickness. Based on these results, the generation of large-area homogenous LIPSS pattern was investigated by unidirectional scanning of the fs-laser beam across the sample surface using different line spacing. The nanostructures are characterized by a spatial period of about 360 nm and a modulation depth of around 160 nm. Chemical surface analysis by Raman spectroscopy confirms a complete ablation of the gold film by the fs-laser irradiation. The characterization of the functional properties shows an increased transmission of the nanostructured samples accompanied by a noticeable change in the wetting properties, which can be additionally modified within a wide range by silanization. The presented approach enables the reproducible LIPSS-based laser direct-writing of sub-wavelength nanostructures on glasses and thus provides a versatile and flexible tool for novel applications in the fields of optics, microfluidics, and biomaterials. Full article
(This article belongs to the Special Issue Laser-Generated Periodic Nanostructures)
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Open AccessArticle
Hierarchical Micro-/Nano-Structures on Polycarbonate via UV Pulsed Laser Processing
Nanomaterials 2020, 10(6), 1184; https://doi.org/10.3390/nano10061184 - 17 Jun 2020
Cited by 2
Abstract
Hierarchical micro/-nanostructures were produced on polycarbonate polymer surfaces by employing a two-step UV-laser processing strategy based on the combination of Direct Laser Interference Patterning (DLIP) of gratings and pillars on the microscale (3 ns, 266 nm, 2 kHz) and subsequently superimposing Laser-induced Periodic [...] Read more.
Hierarchical micro/-nanostructures were produced on polycarbonate polymer surfaces by employing a two-step UV-laser processing strategy based on the combination of Direct Laser Interference Patterning (DLIP) of gratings and pillars on the microscale (3 ns, 266 nm, 2 kHz) and subsequently superimposing Laser-induced Periodic Surface Structures (LIPSS; 7–10 ps, 350 nm, 100 kHz) which adds nanoscale surface features. Particular emphasis was laid on the influence of the direction of the laser beam polarization on the morphology of resulting hierarchical surfaces. Scanning electron and atomic force microscopy methods were used for the characterization of the hybrid surface structures. Finite-difference time-domain (FDTD) calculations of the laser intensity distribution on the DLIP structures allowed to address the specific polarization dependence of the LIPSS formation observed in the second processing step. Complementary chemical analyzes by micro-Raman spectroscopy and attenuated total reflection Fourier-transform infrared spectroscopy provided in-depth information on the chemical and structural material modifications and material degradation imposed by the laser processing. It was found that when the linear laser polarization was set perpendicular to the DLIP ridges, LIPSS could be formed on top of various DLIP structures. FDTD calculations showed enhanced optical intensity at the topographic maxima, which can explain the dependency of the morphology of LIPSS on the polarization with respect to the orientation of the DLIP structures. It was also found that the degradation of the polymer was enhanced for increasing accumulated fluence levels. Full article
(This article belongs to the Special Issue Laser-Generated Periodic Nanostructures)
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Open AccessArticle
Ultrafast Laser Processing of Nanostructured Patterns for the Control of Cell Adhesion and Migration on Titanium Alloy
Nanomaterials 2020, 10(5), 864; https://doi.org/10.3390/nano10050864 - 30 Apr 2020
Cited by 1
Abstract
Femtosecond laser texturing is a promising surface functionalization technology to improve the integration and durability of dental and orthopedic implants. Four different surface topographies were obtained on titanium-6aluminum-4vanadium plates by varying laser processing parameters and strategies: surfaces presenting nanostructures such as laser-induced periodic [...] Read more.
Femtosecond laser texturing is a promising surface functionalization technology to improve the integration and durability of dental and orthopedic implants. Four different surface topographies were obtained on titanium-6aluminum-4vanadium plates by varying laser processing parameters and strategies: surfaces presenting nanostructures such as laser-induced periodic surface structures (LIPSS) and ‘spikes’, associated or not with more complex multiscale geometries combining micro-pits, nanostructures and stretches of polished areas. After sterilization by heat treatment, LIPSS and spikes were characterized to be highly hydrophobic, whereas the original polished surfaces remained hydrophilic. Human mesenchymal stem cells (hMSCs) grown on simple nanostructured surfaces were found to spread less with an increased motility (velocity, acceleration, tortuosity), while on the complex surfaces, hMSCs decreased their migration when approaching the micro-pits and preferentially positioned their nucleus inside them. Moreover, focal adhesions of hMSCs were notably located on polished zones rather than on neighboring nanostructured areas where the protein adsorption was lower. All these observations indicated that hMSCs were spatially controlled and mechanically strained by the laser-induced topographies. The nanoscale structures influence surface wettability and protein adsorption and thus influence focal adhesions formation and finally induce shape-based mechanical constraints on cells, known to promote osteogenic differentiation. Full article
(This article belongs to the Special Issue Laser-Generated Periodic Nanostructures)
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Open AccessArticle
The Role of the Laser-Induced Oxide Layer in the Formation of Laser-Induced Periodic Surface Structures
Nanomaterials 2020, 10(1), 147; https://doi.org/10.3390/nano10010147 - 14 Jan 2020
Cited by 10
Abstract
Laser-induced periodic surface structures (LIPSS) are often present when processing solid targets with linearly polarized ultrashort laser pulses. The different irradiation parameters to produce them on metals, semiconductors and dielectrics have been studied extensively, identifying suitable regimes to tailor its properties for applications [...] Read more.
Laser-induced periodic surface structures (LIPSS) are often present when processing solid targets with linearly polarized ultrashort laser pulses. The different irradiation parameters to produce them on metals, semiconductors and dielectrics have been studied extensively, identifying suitable regimes to tailor its properties for applications in the fields of optics, medicine, fluidics and tribology, to name a few. One important parameter widely present when exposing the samples to the high intensities provided by these laser pulses in air environment, that generally is not considered, is the formation of a superficial laser-induced oxide layer. In this paper, we fabricate LIPSS on a layer of the oxidation prone hard-coating material chromium nitride in order to investigate the impact of the laser-induced oxide layer on its formation. A variety of complementary surface analytic techniques were employed, revealing morphological, chemical and structural characteristics of well-known high-spatial frequency LIPSS (HSFL) together with a new type of low-spatial frequency LIPSS (LSFL) with an anomalous orientation parallel to the laser polarization. Based on this input, we performed finite-difference time-domain calculations considering a layered system resembling the geometry of the HSFL along with the presence of a laser-induced oxide layer. The simulations support a scenario that the new type of LSFL is formed at the interface between the laser-induced oxide layer and the non-altered material underneath. These findings suggest that LSFL structures parallel to the polarization can be easily induced in materials that are prone to oxidation. Full article
(This article belongs to the Special Issue Laser-Generated Periodic Nanostructures)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Extreme Sub-Wavelength Structure Formation from Mid-IR Femtosecond Laser Interaction with Silicon
Authors: Kevin Werner (1), Enam A Chowdhury (3,2,1)
Affiliation: (1) Department of Physics, The Ohio State University, Columbus, OH 43210 (2) Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH 43210 (3) Department of Material Science and Engineering, The Ohio State University, Columbus, OH 43210
Abstract: Mid-infrared (MIR) wavelength (2-10 um) opens up a new paradigm in femtosecond laser solid interaction, both from fundamental and applications perspectives. On fundamental level, compared to ubiquitous near-IR (NIR) or visible (VIS) laser interactions, MIR photon energy scale renders semiconductors like Si and Ge to behave like high bandgap materials, while at the same time conduction electrons are driven harder due to \lambda$^2$ scaling of cycle averaged energy, altering energy absorption characteristics. From applications perspective, many materials that are non-transparent to VIS-NIR range, are transparent to MIR wavelengths, allowing patterning, waveguide writing and machining inside these materials, and also extend interaction to higher order multi-photon processes, paving way to finer resolution in materials processing. Here we present the formation of an anomalous extreme sub-wavelength structure formation ($\sim \lambda/50$) on single crystal silicon surface by a 3600 nm MIR femtosecond laser with a pulse duration of 200 fs. The 50-100 nm linear structures were aligned parallel to the laser polarization direction with a quasi periodicity of approx 700 nm. The dependence of the structure on the native oxide, laser pulse number and polarization were studied. The properties of the structures were studied using SEM, HRTEM, EDS. As traditional models for the formation of laser induced periodic surface structure do not explain how these structures form, new theoretical efforts are needed.

Title: Formation of the submicron oxidative LIPSS on thin titanium films during nanosecond laser recording
Authors: Dmitry A. Sinev, Daria S.Yuzhakova, and Vadim P. Veiko
Affiliation: Faculty of Laser Photonics and Optoelectronics, ITMO University, 49-A Kronverksky Pr., St. Petersburg 197101, Russia
Abstract: Laser-induced periodic surface structures (LIPSS) spontaneously appearing on the laser-treated (melted or evaporated) surfaces of bulk solid materials seem to be a well-studied phenomenon. Peculiarities of oxidative mechanisms of LIPSS formation on thin films though are far less clear. In the present work the appearance of oxidative LIPSS on thin titanium films under ns-pulsed Yb-fiber laser action is demonstrated. The temperature and energy regimes favoring to their formation were revealed, and their geometric characteristics were determined. The period of these LIPSS was found to be about 0.6 λ, and their modulation depth varies between 70 and 110 nm. It was shown that in the regimes of our interest LIPSS tend to predominately self-organize perpendicularly to the scanning direction, which could give a simple way to control their properties.

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