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Simultaneous positive and negative optical patterning with dye-sensitized CdSe quantum dots
摘要： CdSe quantum dots are functionalized with the organic dye iron β-tetraaminophthalocyanine to reward a solution-processable hybrid material with two individually addressable optical resonances. We exploit this dual functionality during optical write/optical read patterning experiments and show that it is possible to simultaneously write complex optical patterns with positive and negative fluorescence contrast. This is enabled by a fluorescence enhancement under near-resonant excitation of the quantum dots in combination with a fluorescence bleaching during excitation of the singlet transition of the phthalocyanine. The presence of the organic dye not only enables negative optical patterning but also enhances the contrast during positive patterning. Furthermore, the patterning result is strongly dependent on the excitation wavelength during readout. Our results highlight the new possibilities that arise from combining inorganic quantum dots and organic π-systems into hybrid nanocomposites.
关键词： fluorescence contrast,optical patterning,iron β-tetraaminophthalocyanine,CdSe quantum dots,hybrid nanocomposites
更新于2025-09-12 10:27:22
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A resist-less patterning method of Al thin film on polycarbonate by F2 laser irradiation
摘要： In recent years, polycarbonate is gathering interests as light and strong material for smart windows. In this paper, a resist-less patterning method of Al thin ?lm on silicone hard-coated polycarbonate by 157 nm F2 laser irradiation is reported. A photomask placed on Al thin ?lm on polycarbonate and irradiated with F2 laser and the non-irradiated area was removed by KOH aq. The mechanism of the method was examined by XPS measurement and it represents that the surface of Al thin ?lm is modi?ed to Al2O3 by F2 laser irradiation and the Al2O3 surface prevents the chemical etching. The ATR-FTIR and XPS measurements of polycarbonate surface under Al thin ?lm imply that the silicone hard coat layer of polycarbonate was oxidized by F2 laser irradiation even under Al thin ?lm and Al-O-Si bonds might be formed between Al and silicone hard coat interface. The formation of Al2O3 at the surface of Al thin ?lm and Al-O-Si bonds at Al/silicone hard coat interface are expected to give abrasion resistance and strong adhesion for Al thin ?lm on silicone hard-coated polycarbonate. This patterned Al ?lm fabrication method contributes to the manufacturing of electrodes for smart polycarbonate windows.
关键词： Surface modi?cation,Metal thin ?lm,VUV laser,Patterning,Chemical etching
更新于2025-09-12 10:27:22
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Pre-Inscribed Laser Surface Pattering for Increased Joining Strength in Laser Fusion Bonding of CFRP and Zinc-Coated Steel
摘要： In this study, we present improved fusion-bonding strength results between carbon fiber-reinforced polyetheretherketone (CFR-PEEK) and zinc-coated steel through the introduction of pre-inscribed laser surface patterns. Optimized laser welding parameters, including laser power, focal position, pitch, number of passes, and clamping pressure, are presented along with parameters for producing the rectangular laser patterns. It was found that for the optimized parameters, the tensile shear strength of the welded samples is improved by as much as 100% when pre-inscribed laser patterns are present. Detailed SEM images of the fractured fusion welded joint samples after the tensile shear test are presented for analysis. The tight bonding between the polymer matrix and the zinc-coated steel inside the formed grooves is found to be the main reason behind the increased tensile shear strength. A comparison of the tensile shear loads for various joining methods is also presented and discussed.
关键词： zinc-coated steel,laser fusion welding,dissimilar joining,laser surface patterning,CRFP and metal joint
更新于2025-09-12 10:27:22
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Simultaneous laser-induced synthesis and micro-patterning of a metal organic framework
摘要： Micro-patterning of a metal organic framework (MOF) from a solution of precursors is achieved by local laser heating. Nano-sized MOFs are formed, followed by rapid assembly due to convective flows around a heat-induced micro-bubble. This laser-induced bottom-up technique is the first to suggest simultaneous synthesis and micro-patterning of MOFs, alleviating the need for pre-preparation and stabilization.
关键词： laser-induced synthesis,metal organic framework,Marangoni convection flows,micro-patterning,nano-MOFs
更新于2025-09-12 10:27:22
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Fabrication of hierarchical surface textures using multi-pulse Direct Laser Interference Patterning with nanosecond pulses
摘要： In this study, we report on the one-step fabrication of hierarchical microstructures on stainless steel substrates using multi-pulse Direct Laser Interference Patterning. The complex structures are produced using a two-beam interference setup with nanosecond laser pulses. The effect of laser fluence and number of pulses on the formation of multi-scale microstructures is systematically investigated. The resulting surface structures are characterized by scanning electron microscopy and white light interference microscopy. It was observed that at low laser fluence, the periodic microstructures remain defined and grow in height above the initial surface, independent on the number of pulses. For higher laser fluences as well as larger number of pulses, the structures adopt a crater-like morphology including a periodic line-like structure.
关键词： multi-scale structures,Direct Laser Interference Patterning,nanosecond pulsed laser,surface microstructuring
更新于2025-09-12 10:27:22
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Tailoring of Silver Nanoparticle Size Distributions in Hydrogenated Amorphous Diamond‐like Carbon Nanocomposite Thin Films by Direct Femtosecond Laser Interference Patterning
摘要： Tailoring of Silver Nanoparticle Size Distributions in Hydrogenated Amorphous Diamond-like Carbon Nanocomposite Thin Films by Direct Femtosecond Laser Interference Patterning
关键词： diamond-like carbon,direct laser interference patterning,silver nanoparticles,ablation threshold,nanocomposites
更新于2025-09-11 14:15:04
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The Role of the Surface Nano-Roughness on the Wettability Performance of Microstructured Metallic Surface Using Direct Laser Interference Patterning
摘要： Superhydrophobic natural surfaces usually have multiple levels of structure hierarchy, particularly microstructures covered with nano-roughness. The multi-scale nature of such a surface reduces the wetting of water and oils, and supports self-cleaning properties. In this work, in order to broaden our understanding of the wetting properties of technical surfaces, biomimetic surface patterns were fabricated on stainless steel with single and multi-scale periodic structures using direct laser interference patterning (DLIP). Micropillars with a spatial period of 5.5 μm and a structural depth of 4.2 μm were fabricated and covered by a sub-micro roughness by using ultrashort laser pulses, thus obtaining a hierarchical geometry. In order to distinguish the influence of the different features on the wettability behavior, a nanosecond laser source was used to melt the nano-roughness, and thus to obtain single-scale patterns. Then, a systematic comparison between the single- and multi-scale structures was performed. Although, the treated surfaces showed hydrophilic behavior directly after the laser treatment, over time they reached a steady-state hydrophobic condition. However, the multi-scale structured metal showed a contact angle 31° higher than the single-scale geometry when the steady-state conditions were reached. Furthermore, the impact of the surface chemistry was investigated by energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) analyses. Finally, a hydrophobizing agent was applied to the laser treated samples in order to further enhance the water contact angles and to determine the pure contribution of the surface topography. In the latter case, the multi-scale periodic microstructures reached static contact angles of 152° ± 2° and a contact angle hysteresis of only 4° ± 2°, while the single-scale structures did not show superhydrophobic behavior. These results definitely suggest that multi-scale DLIP structures in conjunction with a surface chemistry modification can promote a superhydrophobic regime.
关键词： multi-scale microstructures,wettability transition,nanosecond and picosecond laser pulses,direct laser interference patterning
更新于2025-09-11 14:15:04
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Modelling of Optical Damage in Nanorippled ZnO Produced by Ion Irradiation
摘要： Here, we report on the production of nanoripples on the surface of ZnO bulk substrates by ion beam erosion with 20 keV Ar+ ions at an oblique incidence (60°). The ripple patterns, analyzed by atomic force microscopy, follow a power law dependence for both the roughness and the wavelength. At high fluences these ripples show coarsening and asymmetric shapes, which become independent of the beam direction and evidence additional mechanisms for the pattern development. The shallow damaged layer is not fully amorphized by this process, as confirmed by medium energy ion scattering. A detailed study of the damage-induced changes on the optical properties was carried out by means of spectroscopic ellipsometry. Using a 3-layer model based on Tauc-Lorenz and critical point parameter band oscillators, the optical constants of the damaged layer were determined. The results showed a progressive reduction in the refractive index and enhanced absorption below the bandgap with the fluence.
关键词： ripples,ZnO,patterning,sputtering,damage,spectroscopic ellipsometry
更新于2025-09-11 14:15:04
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[Laser Institute of America ICALEO? 2016: 35th International Congress on Applications of Lasers & Electro-Optics - San Diego, California, USA (October 16–20, 2016)] International Congress on Applications of Lasers & Electro-Optics - Selective femtosecond laser ablation of graphene for its micro-patterning
摘要： Due to the outstanding electrical properties of graphene, the demand of its clean and well-defined micro-structures for diverse applications has increased. However, such micro-structured graphene is difficult due to handling and machining problems. Femtosecond lasers are versatile tools for controlled ablation and resulting patterning process. In this paper, we present the selective ablation and functionalization of monolayers of graphene on 300 nm thick thermally grown silicon dioxide on silicon substrates with a Ti:sapphire laser (λ = 800 nm, τ = 40 fs). Investigations were performed on the micro-patterns in graphene ablated by the laser in the fluence range of 0.9-2.2 J/cm2. Just below the ablation threshold functionalization of the graphene layer was obtained. The resolution of the patterning was in the range of a few micrometers. In order to study the effect of oxidation of graphene at the ablation rim, the experiments were conducted both under ambient and inert gas atmosphere conditions. The morphology of the irradiated region of graphene was evaluated with optical microscopy, scanning electron microscopy and atomic force microscopy. With Raman spectroscopy the complete removal of graphene was ascertained. Finally, we find that femtosecond laser ablation is a promising method for direct writing of micro-patterns in graphene monolayers for various potential applications, e.g. for electrodes of thin film transistors.
关键词： selective ablation,functionalization,femtosecond laser ablation,micro-patterning,graphene
更新于2025-09-11 14:15:04
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Picosecond Laser Interference Patterning of Periodical Micro-Architectures on Metallic Molds for Hot Embossing
摘要： In this work, it is demonstrated that direct laser interference patterning (DLIP) is a method capable of producing microtextured metallic molds for hot embossing processes. Three different metals (Cr, Ni, and Cu), relevant for the mold production used in nanoimprinting systems, are patterned by DLIP using a picosecond laser source emitting at a 532 nm wavelength. The results show that the quality and surface topography of the produced hole-like micropatterns are determined by the laser processing parameters, such as irradiated energy density and the number of pulses. Laser-induced periodic surface structures (LIPSS) are also observed on the treated surfaces, whose shapes, periodicities, and orientations are strongly dependent on the accumulated fluence. Finally, the three structured metals are used as embossing molds to imprint microlenses on polymethyl methacrylate (PMMA) foils using an electrohydraulic press. Topographical profiles demonstrate that the obtained structures are comparable to the masters showing a satisfactory reproduction of the texture. The polymeric microlens arrays that showed the best surface homogeneity and overall quality were those embossed with the Cr molds.
关键词： direct laser interference patterning,microstructures,hot embossing,polymethyl methacrylate,laser-induced periodic surface structures
更新于2025-09-11 14:15:04