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Composition and Strain Evolution of Undoped Si <sub/>0.8</sub> Ge <sub/>0.2</sub> Layers Submitted to UV-Nanosecond Laser Annealing
摘要： Ultraviolet Nanosecond Laser Annealing (UV-NLA, XeCl laser, 308 nm, 145 ns) was performed on 30 nm-thick Si0.8Ge0.2 epitaxial layers. The various regimes encountered after single pulse UV-NLA are described and discussed, including submelt, SiGe layer partial and total melt, as well as melt beyond the SiGe epi-layer. Energy densities around 2.00 J/cm2 and above led to the formation of pseudomorphic layers with strong Ge redistribution. Starting from uniform Si0.8Ge0.2 layers, Ge segregation towards the surface resulted in the formation of a Ge-rich surface layer with up to 55% Ge for 2.00 J/cm2. Such pseudomorphic SiGe layers with graded composition and a Ge-rich surface layer may find some promising applications such as contact resistance lowering in doped layers.
关键词： SiGe,pseudomorphic,contact resistance,Ge redistribution,Ultraviolet Nanosecond Laser Annealing
更新于2025-11-14 14:32:36
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Hybrid Laser Ablation and Chemical Modification for Fast Fabrication of Bio-inspired Super-hydrophobic Surface with Excellent Self-cleaning, Stability and Corrosion Resistance
摘要： Although laser ablation is considered as a facile technique to fabricate bio-inspired super-hydrophobic surfaces, the issue is that the initial laser treated metallic surfaces show super-hydrophilic property. It will take a long period to reach super-hydrophobic state under ambient air. It is reported that these super-hydrophobic surfaces could be easily damaged by thermal heating effect or interaction with other liquids, causing uncontrolled loss of super-hydrophobicity. In this study, a stable super-hydrophobic aluminum surface was rapidly fabricated via the hybrid laser ablation and surface chemical modification of (heptadecafluoro-1, 1, 2, 2-tetradecyl) triethoxysilane (AC-FAS). Surface morphology and chemistry were systematically investigated to explore the generation mechanism of super-hydrophobicity. The water contact angle of the treated surfaces can reach up to 160.6? ± 1.5? with rolling angle of 3.0? ± 1.0?, exhibiting perfect self-cleaning capability, long-term stability, and excellent chemical stability in acidic as well as alkaline solutions. The potentiodynamic polarization tests implied that the super-hydrophobic surfaces showed better anti-corrosion performance. This hybrid laser ablation and surface chemical modification are very time-saving and low-cost, which offers a rapid way for quantity production of super-hydrophobic surface on aluminum material.
关键词： nanosecond laser,bioinspiration,corrosion resistance,chemical stability,self-cleaning,super-hydrophobic,long-term stability
更新于2025-09-23 15:22:29
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High-throughput laser generation of Si-nanoparticle based surface coatings for antibacterial applications
摘要： High-productivity regime of nanosecond IR-laser ablative generation of silicon colloidal solutions in water for anti-bacterial applications was found in terms of GW/cm2-level laser intensity and scanning velocity by measuring multi-shot ablative mass loss and extinction coefficients of the colloids as sub-linear and third-power intensity functions, respectively. This advantageous regime implies sub-linear mass loss versus laser intensity at the simultaneous third-power yield of nanoparticles, resulting from the subcritical-density, opaque ablative plasma regulating the sample ablation rate and the related plasma-mediated dissociation (dispergation) of the ablation products. In contrast, at higher intensities, there is a drastic increase in mass loss with the corresponding increased yield of (sub) micrometer-sized particles owing to intense plasma-driven expulsion of micro-scale melt droplets and the corresponding saturation of the extinction coefficient of the colloidal solutions because of their dynamic local “self-limiting” effect during the high-rate ablation. The optimal low-intensity regime for Si nanoparticle production demonstrates the monotonous correlated increase of mass loss and extinction coefficient in terms of increasing laser scanning velocity, indicating the diminished cumulative effects. Surface coatings prepared from the generated Si nanoparticles exhibit minor surface oxidation, as acquired as their elemental composition via energy-dispersive X-ray spectroscopy, making their contact angle for water droplets (≈51°) close to that of bare Si wafer (≈58°) with its nanometer-thick native oxide layer. Owing to good wetting, the nanoparticle-based surface coatings show strong antibacterial response regarding Gram-negative Pseudomonas auereginosa bacteria even despite their minor oxidative passivation.
关键词： Silicon nanoparticles,Colloids,Surface oxidation,Extinction coefficient,Wetting,Antibacterial tests,Gram-negative bacteria Pseudomonas auereginosa,Sub-critical ablative plasma,Nanosecond laser ablation,Mass loss
更新于2025-09-23 15:21:21
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Propulsion effects after laser ablation in water, confined by different geometries
摘要： A Nd:YAG laser with 7-ns pulses and pulse energies up to 10 mJ is used to induce an optical breakdown in the front surface of an aluminum rod, covered by a water layer. The rod is part of a ballistic pendulum. In this way, we study the propulsion effects by means of coupling coefficient and energy-conversion efficiency with respect to different confining geometries, volumes of water applied to the front surface of the rod, and the distance of this surface from the laser-beam focus. Holes with different dimensions are drilled on the target surface and filled with different volumes of water to examine the influence of the confinement by the liquid (a free boundary) and a solid-surface geometry on laser ablation effects. The rod movement and the water ejection after laser ablation are acquired by a high-speed camera with 10k frames per second. The results show that the confinement by cavity substantially increases the propulsion effects by shaping the ejected flow of the liquid; while the cavitation bubble, induced inside the water layer, plays a significant role in propulsion efficiency. From the presented results, it follows that the laser-propelled rod carries below 0.5% of the total mechanical energy after propulsion, while the rest of this energy represents the kinetic energy of the ablated water. As expected, moving the target surface away from the focal position decreases the ablative-propulsion efficiency. When the focus is moved inside the solid target, the decrease occurs due to lower conversion of the pulse energy into the energy of the cavitation bubble. If the focus is moved from the surface outward, the bubble moves towards the liquid–gas interface and it is not able to efficiently eject all the liquid from the target.
关键词： Cavitation bubble,Coupling coefficient,Laser propulsion,Nanosecond laser,Energy-conversion efficiency,Laser ablation
更新于2025-09-23 15:21:01
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The interaction between the osteosarcoma cell and stainless steel surface, modified by high-fluence, nanosecond laser pulses
摘要： The irradiation of metallic surfaces by high-fluence laser pulses in an oxygen-containing atmosphere inevitably modifies the surface topography, chemistry, and wettability. These modifications significantly influence cell-surface interactions and, consequently, surface biocompatibility. We investigate how surface texturing by high-fluence nanosecond laser pulses from a Nd:YAG laser (wavelength of 1064 nm) influences cell adhesion and morphology with the aim of assessing its impact on initial cell behaviour. Quantitative and qualitative analysis of osteosarcoma cell adhesion, viability, and cell morphology were evaluated after 24-hour exposure to non-treated and laser-textured stainless-steel (AISI 316L) surfaces by fluorescent and scanning electron microscopy. The results reveal that this, initial interaction between the cells and the laser-textured surfaces leads to round shaped cells with a smaller footprint. Contrarily, on the non-processed stainless-steel and control-glass surfaces the polygonal, highly elongated, and flattened cells are observed. The cells on the laser-textured surfaces are less dendritic, with short tubular protrusions and an overexpression of extracellular vesicles, which are rarely found on non-treated and control samples. This likely happens due to the formation of nanostructured, high-temperature oxides that are induced by laser ablation. The analysis by X-ray photoelectron spectroscopy reveals that the laser-textured stainless-steel surfaces contain Cr hexavalent oxide, which is more toxic than the native oxide layer on the non-processed samples.
关键词： MG63 cells,cell adhesion,Laser surface engineering,laser texturing,nanosecond-laser ablation
更新于2025-09-23 15:21:01
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Rapid laser fabrication of long-term stable superhydrophilic aluminum surface
摘要： A simple method for fabricating stable superhydrophilic aluminum surface is reported in this paper. Controllable micro-nanostructures were prepared on the surface of aluminum plate by nanosecond laser and then soaked in boiled 45% ethanol solution for 2 h as the post-treatment. It is demonstrated that the laser-ablated aluminum plate surface is hydrophilic and then switch to superhydrophilic after a 45% ethanol solution post-treatment. The treated superhydrophilic structure has good hydrophilic stability in a certain period of time. The mechanism of superhydrophilic behavior of aluminum surface treated with laser and ethanol solution was discussed. A new method for preparing stable superhydrophilic surface is proposed in this paper, which is of great significance for the preparation of superhydrophilic surface and the application of superhydrophilic surface in industrial production.
关键词： Superhydrophilic surface,Ethanol solution,Nanosecond laser,Aluminum,Contact angle
更新于2025-09-23 15:21:01
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Ytterbium-doped fibre femtosecond laser offers robust operation with deep and precise microsurgery of C. elegans neurons
摘要： Laser microsurgery is a powerful tool for neurobiology, used to ablate cells and sever neurites in-vivo. We compare a relatively new laser source to two well-established designs. Rare-earth-doped mode-locked fibre lasers that produce high power pulses recently gained popularity for industrial uses. Such systems are manufactured to high standards of robustness and low maintenance requirements typical of solid-state lasers. We demonstrate that an Ytterbium-doped fibre femtosecond laser is comparable in precision to a Ti:Sapphire femtosecond laser (1–2 micrometres), but with added operational reliability. Due to the lower pulse energy required to ablate, it is more precise than a solid-state nanosecond laser. Due to reduced scattering of near infrared light, it can lesion deeper (more than 100 micrometres) in tissue. These advantages are not specific to the model system ablated for our demonstration, namely neurites in the nematode C. elegans, but are applicable to other systems and transparent tissue where a precise micron-resolution dissection is required.
关键词： Ytterbium-doped fibre femtosecond laser,Laser microsurgery,neuronal regeneration,Ti:Sapphire femtosecond laser,solid-state nanosecond laser,C. elegans
更新于2025-09-23 15:19:57
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Damage-free patterning of thermally sensitive CIGS thin-film solar cells: Can nanosecond pulses outperform ultrashort laser pulses?
摘要： Nanosecond pulses are usually not considered as a suitable candidate for low-damage processing of heat-sensitive materials due to high thermal effects and significant melt formation. Many studies have shown, that CIGS is thermally sensitive material and ultrashort lasers have been chosen as the primary source for the processing of CIGS cells. However, we report on the P3 scribing of CIGS thin-film solar cells with the ns pulse duration at the wavelength of 2.5 μm – a wavelength close to the mid-infrared region and compare the results with the ps pulses covering traditional wavelengths of 355 nm, 532 nm, 1064 nm, and 1342 nm. In our case, 6 ns pulses at 2.5 μm wavelength outperformed the picosecond laser sources operating at VIS and NIR wavelength range. The minimal P3 scribe conductivity of 4.7 mS/m was achieved for ns laser patterning, corresponding to simulated CIGS module efficiency loss of just 0.01%. We proposed that high absorption in the transparent conductive oxide - TCO efficiently shielded the underlying CIGS with only a fraction of energy reaching the back-contact. Finally, results show that nanosecond pulses can be as competitive as picosecond ones for P3 processing of high-efficiency CIGS devices.
关键词： CIGS,Nanosecond laser,Scribing,Picosecond laser,VIS and NIR wavelength range,Thin-film
更新于2025-09-23 15:19:57
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Precise laser trimming of alloy strip resistor: A comparative study with femtosecond laser and nanosecond laser
摘要： Laser trimming has become one of the powerful tools for precise manufacturing of alloy resistors that are widely used in electrical vehicles, electrical controlling, and in appliances. In this work, the influence of femtosecond laser trimming is compared with nanosecond laser trimming. The authors found that lasers focused on different heights relative to the sample surface induced significant changes in surface morphologies. The resistance change was systematically investigated as a function of cutting lengths and cutting depths of different laser powers for both lasers. The experiments display that femtosecond laser trimming has a higher precision of the resistance adjustment than nanosecond laser trimming. The periodic ripple structure by the femtosecond laser was investigated at the focus position above, onto, or beneath the surface. The period of a low frequency ripple structure (LFRS) on the ablated groove bottom is about 600–700 nm when the laser focuses just right on the surface but changes to 490–560 nm when focusing above or beneath the surface. The period of a high frequency ripple structure is about 100–380 nm at the vertical direction of LFRS. The period of low frequency ripple on the outside of the groove is smaller than that on the groove bottom for all three focusing cases. The period of the LFRS is not sensitive to the laser power. The range of the resistor value change in the s-polarized light direction of the femtosecond laser is more than that in the p-polarized light direction.
关键词： Fe-Cr-Al alloy resistor,micromachining,femtosecond laser trimming,nanosecond laser trimming
更新于2025-09-23 15:19:57
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Formation of periodic superhydrophilic microstructures by infrared nanosecond laser processing of single-crystal silicon
摘要： The evolution of the morphology and composition of the single-crystal silicon surface irradiated by infrared and visible nanosecond laser pulses is investigated as a function of processing parameters (laser fluence, irradiation spot size, the number of pulses, background gas pressure and composition). Two types of periodic surface microstructures are obtained with IR (1064 nm) laser pulses in a narrow fluence range of 3-6 J/cm2. At a relatively low number of laser pulses applied, a grid of cleavage cracks is produced within the irradiation spot along the crystal orientation. With further Si irradiation, periodic microhillocks are formed in the nodes of the crack grid. Silicon surface with such microhillocks exhibits superhydrophilic properties which are retained during prolonged storage in air. The cracks are produced in any environment (including vacuum) but the microhillocks are observed only in the presence of oxygen. No periodic structures were observed with visible (532 nm) laser pulses. Mechanisms of nanosecond laser-induced periodic microstructure formation on silicon are discussed.
关键词： oxidation,superhydrophilicity,silicon,periodic microstructures,Nanosecond laser ablation,damage threshold
更新于2025-09-23 15:19:57