- 标题
- 摘要
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Selected aspects of graphene exfoliation as an introductory step towards 3D structuring of graphene nano-sheets
摘要： The paper reviews the advantages of the synthesis of porous three-dimensional (3D) graphene obtained by various exfoliation methods, with a focus on their recent progress and remaining challenges. The manufacturing procedure influences some crucial properties of obtained carbon materials, such as pore structure and the chemical composition of the surface.
关键词： extended surface,graphene,exfoliation,hard template method,3D structuring,porosity
更新于2025-09-23 15:22:29
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Exploiting lateral current flow due to doped layers in semiconductor devices having crossbar electrodes
摘要： Organic electronic devices such as light-emitting diodes, solar cells or rectifying diodes normally have a sandwich layer architecture stacked between the electrodes in a crossbar layout. Often however, the side effects of operating the devices in such an arrangement are either ignored or give rise to misinterpretations regarding the device performance or layer quality. For the sake of simplicity, device currents are typically assumed to exclusively flow in the direction vertical to the substrate, even though the conductivity of doped organic layers is high and gives rise to significant lateral current flows. Here, we study the vertical and lateral charge up along the n-doped and the p-doped layers as well as the resulting capacitance increase of charging the intrinsic layer outside the active area. We observe that controlling such lateral charging by structuring the doped layers can reduce the leakage current dramatically. We employ impedance spectroscopy to investigate the lateral charging responsibility for the capacitance increase at low frequencies. Modeling of the devices by a distributed RC circuit model yields information about the thickness, the conductivity, and the corresponding activation energy of both, the n-doped and the p-doped layers, simultaneously. We demonstrate that the capacitive effects from lateral charging can easily be misinterpreted as trap states in capacitance frequency characteristics. However, correct analysis with the proposed model actually yields rich and detailed post-fabrication information which can be utilized in device failure and degradation tests. Moreover, our results will aid the design and characterization of new electronic devices where lateral charge flow is part of the device concept.
关键词： Parasitic current,Leakage current,Impedance spectroscopy,Crossbar electrodes,Lateral current flow,Organic light-emitting diode,Capacitance,Organic solar cell,Structuring
更新于2025-09-23 15:21:21
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A molecular dynamics approach to nanostructuring of particles produced via aerosol cationic photopolymerization
摘要： Structuring of particles obtained by aerosol photopolymerization is here described from both the experimental and the simulation point of view. Transport phenomena occurring within aerosol droplets are studied in order to identify the key issues that must be carefully designed when considering particles structuring. In particular, phase separation and diffusion of the reacting species were evaluated using molecular dynamics simulations, allowing the identification of a series of formulation parameters such as the composition of a mixed solvent (hexadecane and 2-octanone) or the addition of a chain transfer reagent, which are crucial for the control of phase separation and, thus, of the final morphology of the microparticles. The results were compared with morphology analyses obtained from the experimental work. We also found that molecular simulations were useful for the decoupling of the effects of different solvents which were thus treated separately. The interplay between phase separation and gelation rates was also found to be crucial in the structuring process. For example, the ratio between hexadecane and a chain transfer reagent seemed to strongly affect the final morphology of micro-particles.
关键词： Photopolymerization,Nanoparticles,Nano-structuring,Phase separation,Molecular dynamics
更新于2025-09-23 15:21:01
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Spiky Nickel Electrodes for Electrochemical Oxygen Evolution Catalysis by Femtosecond Laser Structuring
摘要： Micro- and nanostructured Ni/NiO surfaces were generated by femtosecond laser structuring for oxygen evolution reaction in alkaline water electrolysis cells. For two different angles between the laser beam and the nickel surface, two different types of laser-structured electrodes were prepared, characterized, and compared with a plane tempered nickel electrode. Their electrochemical activities for the oxygen evolution reaction were tested by using cyclic and linear sweep voltammetry. The chemical surface composition was investigated by X-ray photoelectron spectroscopy. Laser structuring increased the overall electrochemical performance by more than one order of magnitude. The overpotential of the laser-structured electrodes for the oxygen evolution reaction was decreased by more than 100 mV due to high defect densities of the structures created by the laser ablation process.
关键词： nickel electrodes,femtosecond laser structuring,alkaline water electrolysis,electrochemical catalysis,oxygen evolution reaction
更新于2025-09-23 15:21:01
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All-carbon THz components based on laser-treated diamond
摘要： We report on fs laser structuring and graphitization of diamond and experimental characterization of its THz response. A full characterization of graphitized, conductive layer generated by laser irradiation is carried out by performing scanning-electron microscopy, Raman spectroscopy and electrical measurements. The transmittance of the laser textured diamond samples, both with the graphitic overlayer and after selective oxidizing etching, is analyzed in the (0.25 ÷ 6.0) THz spectral range. A significant selective absorption of the graphitized overlayer towards polarized THz radiation is demonstrated, which is associated to the formation of graphitic laser induced periodic surface structures. This anisotropy allows conceiving compact passive metasurfaces based on conductive/dielectric patterns on the diamond plate surface for the development of robust, lightweight and broadband THz optical components.
关键词： graphitic laser induced periodic surface structures,graphitization,electrical measurements,fs laser structuring,THz response,transmittance,THz optical components,polarized THz radiation,conductive layer,diamond,Raman spectroscopy,metasurfaces
更新于2025-09-23 15:19:57
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Features of fused silica ablation by laser induced carbon microplasma
摘要： The features of surface structuring on the transparent material by laser-induced microplasma were studied and the intensity of its microplasma was measured. The formation of micro-relief by a series of nanosecond pulsed laser induced carbon microplasma in confinement mode on the surface of fused silica were investigated and the measured intensity was compared with the features of micro-relief. The dependence of depth of formed relief and track on the laser regime was determined. It is shown that the mechanism of microstructure formation is dependent on multifactor and associated with the ablation on the surface of fused silica by the microplasma, which exists quite long time after the pulses.
关键词： Ablation,Surface structuring,Laser-induced microplasma,Nanosecond pulses,Fiber laser,Fused silica
更新于2025-09-23 15:19:57
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Laser Direct Structuring of Bioinspired Spine with Backward Microbarbs and Hierarchical Microchannels for Ultrafast Water Transport and Efficient Fog Harvesting
摘要： Achieving effective dropwise capture and ultrafast water transport is essential for fog harvesting. In nature, Cactus uses the conical spine with micro-barbs to effectively capture fog while Sarracenia utilizes the trichome with hierarchical microchannels to quickly transport water. Herein, we combined their advantages to present a novel configuration, spine with barbs and hierarchical channels (SBHC), for simultaneous ultrafast water transport and high-efficient fog harvesting. This bio-inspired SBHC exhibited the fastest water transport ability and the highest fog harvesting efficiency in comparison with spine with hierarchical channels (SHC), spine with barbs and grooves (SBG) and spine with barbs (SB). Based on the fundamental SBHC unit, we further designed and fabricated a 2D spider-web alike fog collector and a 3D cactus alike fog collector using direct laser structuring and Origami techniques. The 2D spider-web and 3D cactus alike fog collectors showed high-efficient fog collection capacity. We envision that this fundamental understanding and rational design strategy can be applied in fog harvesting, heat transfer, liquid manipulation, and microfluidics.
关键词： Direct laser structuring,Water transport,Spine and micro-barbs,Fog harvesting,Hierarchical microchannels
更新于2025-09-23 15:19:57
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Broadband, wide-angle antireflection in GaAs through surface nano-structuring for solar cell applications
摘要： We demonstrate broadband and wide-angle antireflective surface nanostructuring in GaAs semiconductors using variable dose electron-beam lithography (EBL). Various designed structures are written with EBL on a positive EB-resist coated GaAs and developed followed by shallow inductively coupled plasma etching. An optimized nanostructured surface shows a reduced surface reflectivity down to less than 2.5% in the visible range of 450–700 nm and an average reflectance of less than 4% over a broad near-infrared wavelength range from 900–1400 nm. The results are obtained over a wide incidence angle of 33.3°. This study shows the potential for anti-reflective structures using a simpler reverse EBL process which can provide optical absorption or extraction efficiency enhancement in semiconductors relevant to improved performance in solar photovoltaics or light-emitting diodes.
关键词： GaAs,surface nano-structuring,broadband,solar cell applications,wide-angle,antireflection
更新于2025-09-23 15:19:57
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Femtosecond laser-induced surface structuring of the porous transport layers in proton exchange membrane water electrolysis
摘要： In proton exchange membrane water electrolysis (PEMWE) cells the performance and thus the conversion efficiency are influenced by the interface between the porous transport layer (PTL) and the catalyst layer (CL). In the following paper, this interface is modified by the use of femtosecond laser-induced surface structuring, so that the specific surface area of the titanium based fibers of the PTL is increased. The resulting morphology exhibits two roughness levels of (i) a relatively coarse structure featuring tips of a few micrometers in diameter and depth, which are each covered in turn by (ii) a substructure of smaller tips of a few to several hundred nanometers in diameter and depth. PEMWE electrochemical characterization and short-term stress tests reveal that the cell performance is increased due to the laser-structuring of the PTL surface towards the CL. For instance, the cell voltage is reduced by approximately 30 mV after 100 h at 4 A cm?2. These beneficial effects are observed over the entire current density range and thus correspond to a decreased equivalent cell resistance of at least 6 mΩ cm2 for electrical interfacial contact losses and at least 2 mΩ cm2 for mass transport losses. A physical characterization by scanning electron microscopy shows that the CL surface is much rougher and more jagged when using laser-structured fibers. Thus, the gaseous oxygen and the liquid water transport both from and to the active sites of the catalyst seem to be improved.
关键词： catalyst layer,cell performance,proton exchange membrane water electrolysis,porous transport layers,femtosecond laser-induced surface structuring
更新于2025-09-23 15:19:57
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Characterization of a magnetic fluid exposed to a shear flow and external magnetic field using small angle laser scattering
摘要： The paper demonstrates a possibility to use Small Angle Light Scattering (SALS) method realized in a conventional laboratory to investigate structuring processes in a magnetic fluid simultaneously exposed to a shear flow and external magnetic field. We have used custom made SALS-setup with a laser source combined with a microfluidic chip, an electromagnet and a magnetic circuit to obtain scattering images of a low concentrated biocompatible magnetic fluid with clustered iron oxide nanoparticles. Application of an external magnetic field drastically influences a physical behaviour of the fluid and this effect is directly related to aggregation of particles resulting in chains with a dimension of several micrometers. These chains results in the anisotropy of the scattering patterns. We have observed an influence of the field and flow on the intensity gradient of the obtained scattering patterns. Presented methodic opens broad perspectives to obtain microstructural information as well to evaluate structuring kinetics of the diluted magnetic suspensions using conventional laboratory conditions. Performed by us SALS measurements are accomplished with a full characterization of the fluid using magneto-rheometry, vibrating sample magnetometry, microscopy as well as dynamic light scattering.
关键词： small angle laser scattering,structuring,microstructure,magnetic fluid
更新于2025-09-19 17:13:59