Filtern
Erscheinungsjahr
Dokumenttyp
- Vortrag (68)
- Posterpräsentation (31)
- Beitrag zu einem Tagungsband (21)
- Zeitschriftenartikel (13)
- Buchkapitel (10)
- Beitrag zu einem Sammelband (4)
- Monografie (1)
- Corrigendum (1)
- Video (1)
Referierte Publikation
- nein (150) (entfernen)
Schlagworte
- Laser-induced periodic surface structures (LIPSS) (34)
- Surface functionalization (21)
- Femtosecond laser (17)
- Femtosecond laser ablation (14)
- Laser processing (12)
- Applications (9)
- Laser-induced periodic surface structures, LIPSS (9)
- Laser ablation (7)
- Microstructures (6)
- Nanostructures (6)
- Oxidation (6)
- Friction (5)
- Tribology (5)
- Wear (5)
- Ablation (4)
- Electromagnetic scattering (4)
- Capillary waves (3)
- Femtosecond laser processing (3)
- Laser-induced X-ray emission (3)
- Oberflächenfunktionalisierung (3)
- Ultrafast laser processing (3)
- Wetting (3)
- Atomic force microscopy (2)
- Chalcopyrite (2)
- Cu(InGa)Se2 (2)
- Damage threshold (2)
- Dielectrics (2)
- Doping (2)
- Femtosecond (2)
- Free electron laser (2)
- Hard X-ray photoelectron spectroscopy (HAXPES) (2)
- Incubation (2)
- Indium phosphide (2)
- Industrial applications (2)
- LIPSS (2)
- Laser-Materialbearbeitung (2)
- Laser-induced periodic surface structures (2)
- Light concentration (2)
- Micro solar cells (2)
- Nanosecond laser ablation (2)
- Nanostrukturen (2)
- Radiation protection (2)
- Selective emitter (2)
- Silicon (2)
- Steel (2)
- Ti6Al4V alloy (2)
- Time-resolved scattering (2)
- Titanium alloy (2)
- 100Cr6 (1)
- 532 nm wavelength (1)
- Absorber optimization (1)
- Additive (1)
- Additives (1)
- Anodization (1)
- Antiadhesive surfaces (1)
- Antibakterielle Oberflächen (1)
- Antimicrobial (1)
- Auger electron spectroscopy (1)
- Bacteria (1)
- Bacteria-repellent surfaces (1)
- Bacterial adhesion tests (1)
- Bessel-Strahlen (1)
- Biofilm growth (1)
- Biofilme (1)
- Biofilms (1)
- Bone screws (1)
- CIGS (1)
- Carrier excitation (1)
- Carrier plasmas (1)
- Cell adhesion (1)
- Cell-repellent surfaces (1)
- Chalkopyrite (1)
- Chemical analyses (1)
- Chemical analysis (1)
- Copper indium gallium diselenide (CIGSe) (1)
- Cribellate spiders (1)
- CuInSe2 (1)
- Double-pulse (1)
- Dünnschichtsolarzellen (1)
- Electrical properties (1)
- Electrochemical treatment (1)
- Electromagnetic radiation (1)
- Femtosecond laser irradiation (1)
- Femtosecond laser-processing (1)
- Femtosecond pulse laser (1)
- Femtosekunden-Laserablation (1)
- Femtosekundenlaser (1)
- Finite-difference time-domain calculations (1)
- Fluid transport (1)
- Force distance curve (1)
- Free electron laser (FEL) (1)
- Glasses (1)
- Glow-discharge optical emission spectroscopy (1)
- Hydrodynamics (1)
- Implant material (1)
- Interferometer (1)
- Ionic liquid (1)
- Isotopes (1)
- LIFT (1)
- Laser induced periodic surface structures (LIPSS) (1)
- Laser material processing (1)
- Laser materials processing (1)
- Laser nanostructuring (1)
- Laser scribing (1)
- Laser technology (1)
- Laser-induced Periodic Surface Structures (LIPSS) (1)
- Laser-induced amorphization (1)
- Laser-induced forward transfer (LIFT) (1)
- Laser-induced micro- and nanostructures (1)
- Laser-induced periodic surface strcutures (LIPSS) (1)
- Laser-induced periodic surface strcutures, LIPSS (1)
- Laser-induzierte periodische Oberflächen-Nanostrukturen (1)
- Laser-induzierte periodische Oberflächenstrukturen (1)
- Laserschutz (1)
- Laserstrukturierung (1)
- Lizard (1)
- Lizards (1)
- Lubrication (1)
- Materialbearbeitung (1)
- Matter reorganization (1)
- Medical implants (1)
- Metals (1)
- Micro solar cell (1)
- Micromachining (1)
- Microstructure (1)
- Mikrostrukturen (1)
- Modelling (1)
- Molybdenum (1)
- Multicrystalline silicon (1)
- Multiphoton absorption (1)
- Nanometrology (1)
- Nanosecond pulses (1)
- Nanostrcutures (1)
- Native oxide layer (1)
- Nonlinear lithography (1)
- Oberflächenmodifikation (1)
- Optical properties (1)
- Optical scattering (1)
- Optics at surfaces (1)
- PAG (1)
- Pacemaker (1)
- Photovoltaik (1)
- Polymer (1)
- Pulse shaping (1)
- Pump-probe (1)
- Pump-probe experiments (1)
- Quantitative phase-contrast microscopy (1)
- Quarzglas (1)
- Reactive oxygen species (1)
- Refractive index engineering (1)
- Reibung (1)
- Reibungsreduktion (1)
- Ripples (1)
- Röntgenemission (1)
- Saphir (1)
- Scanning electron microscopy (1)
- Scanning/atomic force microscopy (SFM/AFM) (1)
- Second harmonic generation (SHG) (1)
- Secondary hazard (1)
- Sekundärstrahlung (1)
- Self-organization (1)
- Semiconductor (1)
- Semiconductors (1)
- Silicon solar cell (1)
- Simulation (1)
- Spatial light interference microscopy (1)
- Spectroscopic imaging ellipsometry (1)
- Sputter deposition (1)
- Stiffness (1)
- Strain (1)
- Surface engineering (1)
- Surface plasmon polaritons (1)
- Surface structures (1)
- TeO2 (1)
- Tellurium dioxide crystals (1)
- Theoretical modelling (1)
- Thin-film solar cells (1)
- TiAl64V (1)
- Time-of-flight mass spectrometry (TOF-MS) (1)
- Time-of-flight mass spectroscopy (1)
- Time-of-flight secondary ion mass spectrometry (ToF-SIMS) (1)
- Time-offlight secondary ion mass spectrometry (ToF-SIMS) (1)
- Time-resolved analysis (1)
- Time-resolved coherent XUV scattering (1)
- Time-resolved coherent scattering (1)
- Titanium (1)
- Titanium alloys (1)
- Titanium nitride (1)
- ToF-SIMS (1)
- Transmission electron microscopy (1)
- Tribologie (1)
- Ultra-short pulse laser processing (1)
- Ultrafast laser excitation (1)
- Ultrafast phenomena (1)
- Ultrafast scattering (1)
- Ultrakurze Laserpulse (1)
- Ultrakurzpuls-Laser (1)
- Ultrakurzpuls-Laserbearbeitung (1)
- Ultrashort (1)
- Ultrashort laser material interaction (1)
- Ultrashort laser processing (1)
- Ultrashort pulse laser processing (1)
- VUV nanosecond laser ablation (1)
- Verschleiß (1)
- Verschleißreduktion (1)
- X-ray (1)
- XUV scattering (1)
- a-Si/my-Si (1)
Organisationseinheit der BAM
- 6 Materialchemie (58)
- 6.2 Material- und Oberflächentechnologien (58)
- 9 Komponentensicherheit (11)
- 9.5 Tribologie und Verschleißschutz (11)
- 6.1 Oberflächen- und Dünnschichtanalyse (7)
- 4 Material und Umwelt (5)
- 4.1 Biologische Materialschädigung und Referenzorganismen (5)
- 6.6 Physik und chemische Analytik der Polymere (1)
Laser-induced periodic surface structures (LIPSS) have gained remarkable attention as they represent a universal phenomenon that is often accompanying laser-processing. Such LIPSS enable a large variety of different surface functionalizations for applications in the fields of optics, fluidics, tribology, or medicine. Moreover, so-called “high spatial frequency LIPSS” (HSFL) provide an appealing and straightforward way for surface nanostructuring featuring spatial periods even below 100 nm – far beyond the optical diffraction limit. However, the imposed surface functionalities are usually caused by both, topographic and chemical surface alterations. For exploring these effects in detail, multi-method characterizations were performed here for HSFL on processed Ti- 6Al- 4V alloy upon irradiation with near-infrared ps-laser pulses (1030 nm wavelength, ~1 ps pulse duration, 1 – 400 kHz pulse repetition rate) under different laser and scan processing conditions. The sample characterization involved morphological and topographical investigations by scanning electron microscopy (SEM), atomic force microscopy (AFM), stylus profilometry (SP), and white light interference microscopy (WLIM), as well as near-surface chemical analyses by X-ray photoelectron spectroscopy (XPS), hard X-ray photoelectron spectroscopy (HAXPES) and depth-profiling time-of-flight secondary ion mass spectrometry (TOF-SIMS). The results allow to qualify the laser ablation depth, the geometrical HSFL characteristics and provide detailed insights into the depth extent and the nature of the ps-laser-induced near-surface oxidation. Significance for medical applications will be outlined.
Chemical effects during the formation of femtosecond laser-induced periodic surface structures
(2019)
The processing of laser-induced periodic surface structures (LIPSS, ripples) on metals and semiconductors in ambient air is usually accompanied by superficial oxidation effects – a fact that is widely neglected in the current literature. In this contribution, chemical, structural, and mechanical alterations in the formation of femtosecond LIPSS are characterized by a variety of surface analytical techniques, including energy dispersive X-ray analyses (EDX), X-ray photoelectron spectroscopy (XPS), micro Raman spectroscopy (µ-RS), and depth-profiling Auger electron microscopy (AEM). Alternative routes of electrochemical and thermal oxidation allow to qualify the relevance of superficial oxidation effects on the tribological performance in oil lubricated reciprocating sliding tribological tests (RSTT). It is revealed that the fs-laser processing of near-wavelength sized LIPSS on metals leads to the formation of a few hundreds of nanometers thick graded oxide layers, consisting mainly of amorphous oxides. Regardless of reduced hardness and limited thickness, this nanostructured surface layer efficiently prevents a direct metal-to-metal contact in the RSTT and may also act as an anchor layer for specific wear-reducing additives contained in the used engine oil.
The processing of laser-induced periodic surface structures (LIPSS, ripples) on metals and semiconductors in ambient air is usually accompanied by superficial oxidation effects - widely neglected in the current literature. In this contribution, chemical, structural, and mechanical alterations in the formation of femtosecond LIPSS are characterized by a variety of surface analytical techniques, including energy dispersive X-ray analyses (EDX), X-ray photoelectron spectroscopy (XPS), micro Raman spectroscopy (µ-RS), and depth-profiling Auger electron microscopy (AEM). Alternative routes of electrochemical and thermal oxidation allow to qualify the relevance of superficial oxidation effects on the tribological performance in oil lubricated reciprocating sliding tribological tests (RSTT). It is revealed that the fs-laser processing of near-wavelength sized LIPSS on metals leads to the formation of a few hundreds of nanometer thick graded oxide layer, consisting mainly of amorphous oxides.
Regardless of its reduced hardness and limited thickness, this nanostructured surface layer can effciently prevent a direct metal-metal contact in the RSTT and may also act as an anchor layer for specific wear-reducing additives contained in the engine oil involved
A corrosion study is performed on six variations of titanium grade 5 (Ti6Al4V) samples. Samples are prepared in different conditions by variation of preanodization, postanodization, and picosecond-laser (ps-laser) surface treatment, while polished and anodized samples serve as reference. Microcones and nanosized periodic surface features are successfully produced on Ti6Al4V samples. The morphology and topography of the structures are visualized by scanning electron microscopy and white light interference microscopy. Furthermore, the relative electrochemically active surface area (ECSA) is determined for the ps-laser-treated samples. It is determined that the preanodized and laser-treated sample has 3.5 times larger ECSA than a polished sample, and that the laser-treated sample has 4.1 times larger area. Moreover, Tafel analysis is performed to determine the corrosion properties of the samples. It is shown that the corrosion resistance improves for both laser-structured samples after the anodization. To further study the surface of the samples, electrochemical impedance spectroscopy measurements are conducted. The study indicates that the ps-laser-treated and anodized Ti6Al4V is suitable to be used for the fabrication of bone screws and plates due to its improved corrosion resistance as compared to nonanodized samples.
Surface nanostructures provide the possibility to create and tailor surface functionalities mainly via controlling their topography along with other chemical and physical material properties. One of the most appealing technologies for surface functionalization via micro- and nanostructuring is based on laser processing. This can be done either via direct contour-shaping of the irradiated material using a tightly focused laser beam or in a self-ordered way that allows employing larger laser beam diameters along with areal scanning to create a variety of laser-induced periodic surface structures (LIPSS). For the latter approach, particularly ultrashort pulsed lasers have recently pushed the borders across long-lasting limitations regarding the minimum achievable feature sizes and additionally boosted up the production times. This chapter reviews the plethora of recently investigated applications of LIPSS—for example, via imposing diffractive or plasmonic structural colors, the management of liquids and surface wetting properties, biomedical and bioinspired functionalities, beneficial effects in tribology for reducing friction and wear, the manipulation of optical scattering and absorption in photovoltaics, or the modification of magnetic or superconducting surface properties in other energy applications. The footprint of the LIPSS-based technology is explored in detail regarding the current state of industrialization, including an analysis of the market and associated LIPSS production costs.
Given their unique properties, ultrashort laser pulses with durations in the femtosecond to picosecond range currently open new avenues in the field of laser materials processing, resulting in groundbreaking new applications based on laser-induced surface functionalization. This article reviews the usability of temporally distributed energy deposition via double-pulse irradiation in applications based on laser ablation. This includes simple new techniques for surface nanostructuring and improved sensitivities in spectroscopic material analyses.
Laser material processing is an emerging technology that generates surface functionalities on the basis of optical, mechanical, or chemical properties. In the form of laser surface texturing (LST), it has attracted a remarkable amount of research to tailor surface properties towards various tribological applications. The main advantages of this single-step, laser-based technology are the contactless machining, featuring a high flexibility, efficiency, and speed, along with the excellent quality of the processed products. LST can be applied precisely localized to sub-micrometric areas, but, via laser beam scanning, it is also feasible for structuring large surface areas at the square meter size.
This Special Issue focuses on the latest developments concerning the tribological performance of laser-generated periodic surface nano- and microstructures and their applications. This includes the laser-based processing of different surface patterns, such as “self-organized” laser-induced periodic surface structures (LIPSS, ripples), grooves, micro-spikes, hierarchical hybrid nano-/micro-structures, microfeatures generated by direct laser interference patterning (DLIP), or even dimples or other topographic geometries shaped by direct laser modification or ablation. The applications of these periodically nano- and micro-patterned surfaces may improve the lubricated or non-lubricated tribological performance of surfaces in conformal and even non-conformal contact through a reduction of wear, a variation of the coefficient of friction, altered load carrying capacity, etc., resulting in energy saving, improved reliability, increased lifetimes as well as durability, leading in turn to extended maintenance intervals/reduced down-time. This can be beneficial in terms of bearings, gears, engines, seals, cutting tools, or other tribological components. Fundamental aspects addressed may involve the investigation of the relevant physical and chemical effects accompanying the laser-generated nano- and microscale topographies, such as alterations of the material structures, the hardness, superficial oxidation, the role of additives contained in lubricants, surface wettability, micro-hydrodynamic effects, etc.
For this Special Issue we aim to attract both academic and industrial researchers and would like to provide a bridge between research in the fields of tribology and laser material processing in order to foster the current knowledge and present new ideas for future applications and new technologies.
Ultrashort pulse laser materials processing can be accompanied by the production of X-rays. Small doses per laser pulse can accumulate to significant dose rates at high laser pulse repetition rates which may exceed the permitted X-ray limits for human exposure. Consequently, a proper radiation shielding must be considered in laser machining. A brief overview of the current state of the art in the field of undesired generation of X-ray radiation during ultrashort pulse laser material processing in air is presented.
Der Vortrag gibt einen Überblick über die Erzeugung und Charakterisierung anisotroper Nanostrukturen mittels ultrakurzgepulster Laserstrahlung. Besonderes Augenmerk liegt dabei auf dem Phänomen der sogenannten Laser-induzierten periodischen Oberflächen-Nanostrukturen auf dielektrischen Werkstoffen und ihrer zeitlichen Dynamik. Weitere Beispiele von Volumen-Nanostrukturen aus der Literatur werden diskutiert.
We discuss the dynamics of ultrashort pulsed laser excitation in bulk optical silica-based glasses (fused silica and borosilicate BK7) well-above the permanent modification threshold. We indicate subsequent structural and thermomechanical energy relaxation paths that translate into positive and negative refractive index changes, compression and rarefaction zones. If fast electronic decay occurs at low excitation levels in fused silica via self-trapping of excitons, for carrier densities in the vicinity of the critical value at the incident wavelength, persistent long-living absorptive states indicate the achievement of low viscosity matter states manifesting pressure relaxation, rarefaction, void opening and compaction in the neighboring domains. An intermediate ps-long excited carrier dynamics is observed for BK7 in the range corresponding to structural expansion and rarefaction. The amount of excitation and the strength of the subsequent hydrodynamic evolution is critically dependent on the pulse time envelope, indicative of potential optimization schemes.
A laser-based bottom-up technique for the fabrication of Cu(In,Ga)Se2 (CIGSe) micro solar cells is presented.
We use femtosecond laser-induced forward transfer (LIFT) to transport a metallic precursor composed of copper, indium, and gallium onto a molybdenum back contact layer on a glass substrate. A CIGSe absorber forms by subsequent selenization. An array of micro absorbers with defined spacing is fabricated to solar cells and characterized under concentrated light illumination. The solar cell array exhibited a conversion efficiency of 1.4‰ at 1 sun as well as a significant efficiency enhancement of 68% rel. under 20-fold concentration. This work demonstrates the possibility of directly grown micrometer-sized solar cells based on chalcogenide absorber layers, enabling effective material usage.
Multi-shot investigations of Ti:sapphire laser (wavelength (lambda) approximately equals 800 nm) induced damage were performed in three different laboratories (BAM, Berlin; LZH, Hannover; UNM, Albuquerque). The ablation behavior of a high reflecting mirror consisting of alternating (lambda) /4- layers of Ta2O5 and SiO2 was studied. Fused silica served as substrate. The influence of the pulse duration ((tau) equals 13 - 130 fs), the pulse number (30 - (infinity) ) and the repetition rate (10 Hz - 100 MHz) on the damage threshold will be discussed.
Micromachining experiments were performed with Ti:sapphire laser pulses (130 fs - 150 fs, 800 nm, approximately 10 Hz) in air. Employing the direct focusing technique, highly absorbing titanium nitride (TiN) and weakly absorbing polyimide (PI) and polymethylmethacrylate (PMMA) served as target materials. The lateral and vertical precision of the laser ablation and morphological features were characterized by scanning force (SFM), scanning electron (SEM) and optical microscopy. For TiN, incubation can be observed, i.e. the single-pulse surface damage threshold (0.26 J/cm2) is by a factor of two greater than the threshold for 100 pulses. Ablation rates below 10 nm per pulse can be achieved. The evolution of sub-wavelength ripples is presented in dependence on pulse number and laser fluence, respectively. The incubation behavior of the polymers can be described by an accumulation model as for TiN. Experiments on PI with varying focal lengths result in the same modification thresholds. Different polarization states of light (linear, circular) lead to a variation of the ablation rate and to various morphological patterns in the ablation craters (wavelength ripples, cones). Swelling of PMMA occurred at fluences below the ablation threshold.