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Laser-induced graphitized periodic surface structure formed on tetrahedral amorphous carbon films
摘要： Femtosecond laser-induced periodic surface structure (LIPSS), graphitization and swelling observed on ultra-hard, hydrogen-free tetrahedral amorphous carbon (ta-C) films are examined and compared with those on hydrogenated amorphous carbon (a-C:H) films, nitride films, and glassy carbon plates. The threshold fluence for LIPSS formation on ta-C is approximately twice as high as that for other specimens, and the LIPSS period Λ near the threshold is very fine at ca. 80 nm. Λ gradually increases with increasing fluence, and rapidly increases to ca. 600 nm at a high fluence. The ablation rate also increases rapidly at this fluence. In addition, ta-C and a-C:H are graphitized by irradiation and expand in volume. The surface layer of ta-C film changes to nanocrystalline graphite as the fluence increases and the crystallinity is improved; however, at higher fluence, the crystallinity deteriorates suddenly similar to that at low fluence. At high fluence, the rapid increase in Λ and the ablation rate, and the sudden deterioration in crystallinity are determined as common phenomena for these disordered carbons. LIPSS formation and swelling over a large area by scanned spot irradiation produces submicron height flat hills with conductivity and surface functionality on the insulating surface.
关键词： Graphitization,Swelling,Laser-induced periodic surface structure,Femtosecond-laser processing,Nanocrystalline graphite,Tetrahedral amorphous carbon
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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Laser-engineered heavy hydrocarbons: Old materials with new opportunities
摘要： Polycyclic heavy hydrocarbons (HHs) such as coal, tar, and pitch are a family of materials with extremely rich and complex chemistry, representing a massive opportunity for their use in a range of potential applications. The present work shows that optimal selection of initial HHs based on molecular constituents is essential in tuning the material for a particular and targeted electronic application. Combining the selection of feedstock chemistry (H:C and aromatic content) and controlling variable laser treatment parameters (laser power, speed, and focus) lead to full control over the H:C ratio, sp2 concentration, and degree of graphitic stacking order of the products. The broad intertunability of these factors results from a wide distribution of carbon material crystallinity from amorphous to highly graphitic and a broad distribution of electrical conductivity up to 103 S/m.
关键词： heavy hydrocarbons,graphitization,conductivity,electronic applications,laser ablation
更新于2025-09-23 15:19:57
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Atomic structure of nanodiamond and its evolution upon annealing up to 1200?°C: Real space neutron diffraction analysis supported by MD simulations
摘要： Lattice strain, crystallite shape and the crystallite size distribution in nanocrystalline diamond were determined from powder diffraction data. The data were analysed by the direct space PDF method in combination with Molecular Dynamics simulations. Experimental Pair Distribution Functions were obtained from the large Q neutron diffraction data. Lattice strains were determined by comparison of the atomic pair distances at different length scales. The experimental pair-distance data were matched against the Molecular Dynamics models of diamond nanograins. Lattice relaxation at the surface and in the bulk of the simulated nanodiamond grains varied with their shape and size. Comparison of the model data to the experimentally determined strain characteristics yielded accurate information on the structure of the actual nanodiamond powders. In the as-synthesized nanodiamond the grains are polyhedrons predominantly terminated by (100) and (111) surfaces. Upon annealing the (111) surfaces with one dangling bond per atom graphitize and transform into surfaces with three dangling bond per-atom. In the samples annealed at 1200oC all grains are octahedrons terminated only by three dangling bond (111) surfaces. The mechanism of the atom rearrangement during the transformation of the (111) diamond surface into a graphite double-sheet was proposed.
关键词： graphitization,atomic structure,molecular dynamics,nanodiamond
更新于2025-09-19 17:15:36
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Improved conductivity of carbonized polyimide by CO <sub/>2</sub> laser graphitization
摘要： Direct laser writing (DLW) is a fast and cost-effective technique for printing conductive structures on flexible substrates such as polyimide (PI) by the conversion of insulative PI to conductive carbon. However, the conductivity (B103 S m?1) obtained by this method needs to be improved to compete with ink-jet printing of carbon-based materials. The reason behind the low conductivity achieved by the DLW process is due to the crystallinity and hybridization of bonding in carbonaceous structures. In this work, the DLW process has been implemented in two steps: the first step called carbonization was performed by writing pulsed CO2 laser on PI to form tracks which consist of amorphous tetrahedral carbon (a mixture of sp2 and sp3 hybridized carbon) having intrinsically low conductivity. The second step called graphitization is overwriting of the laser on the pre-carbonized tracks to convert sp3 hybridized bonds to sp2 hybridized bonds by the process called laser graphitization. The conductivity of tracks carbonized at (0.21 ± 0.02) W and fluence (3.31 ± 0.32) × 103 mJ cm?2 at a repetition rate of 0.1 kHz was 56.1 ± 3.1 S m?1 which increased to 146.7 ± 5.1 S m?1 upon overwriting with the laser at (0.50 ± 0.03) W and fluence (7.88 ± 0.47) × 103 mJ cm?2 at the same repetition rate. The photothermal process of carbonization and graphitization is modeled for the DLW process and the threshold power of both the processes is calculated and validated by Raman spectroscopy. Improved conductivity achieved by detailed understanding of the laser and material parameters involved in this transformation enables process optimization leading to future applications in scalable manufacturing of flexible bio-sensors and electrochemical energy storage devices.
关键词： Direct laser writing,carbonization,graphitization,CO2 laser,polyimide,conductivity
更新于2025-09-19 17:13:59
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[IEEE 2019 Wave Electronics and its Application in Information and Telecommunication Systems (WECONF) - Saint-Petersburg, Russia (2019.6.3-2019.6.7)] 2019 Wave Electronics and its Application in Information and Telecommunication Systems (WECONF) - Analysis of Hpht Diamonds by Laser-Induced Breakdown Spectroscopy
摘要： The analysis of sectoral nitrogen-containing HPHT diamonds by the method of laser-induced breakdown spectroscopy was performed. The possibility of detecting changes in structural bonds and the impurity composition under conditions of laser- induced graphitization of the surface was studied. It was found that the plasma spectra of transition states of the surface during the process of laser-induced graphitization are also very important for analysis and can help identification of diamonds. the Identification of diamonds can occur both based on detecting differences in the content of H, O, N impurities, and detecting differences in the structural disorder of carbon bonds, particularly in the relative change in the number of C=C bonds. All these differences may be a consequence of either technological differences in the history of diamond synthesis, or the presence of additional post-growth diamond processing, or with the presence of the multisectoral structure of the test sample
关键词： HPHT diamonds,laser-induced breakdown spectroscopy,laser-induced graphitization
更新于2025-09-12 10:27:22
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Pure carbon conductive transparent electrodes synthetized by a full laser deposition and annealing process
摘要： One of the biggest challenge that face optoelectronic and photovoltaic devices is the necessity to provide a reliable alternative to transparent conducting oxide (TCO) like Indium Thin Oxide (ITO). We recently published a study proposing a method to produce transparent conductive electrodes only based on carbon materials. In a first step, we use the Pulsed Laser Deposition (PLD) to produce high performance DLC. Those thin films own very interesting properties in kindship with diamond, like high transparency in the visible range, chemical inertness and biocompatibility. In addition, the DLC is a perfect electrical insulator and presents a relative high opacity in ultra-violet (UV). This particularity has a great interest to perform, in a second step, UV laser annealing over the DLC surface. The aim is to break the existing diamond bindings (sp3 hybridization) on the surface and allow atoms being reorganized in graphitic bindings (sp2 hybridization). We demonstrate that the increase of atomic graphitic bindings leads to a valuable surface conductivity. According to optimized annealing parameters, the surface conductivity reaches values comparable to ITO. We also show that the laser treatments only sparsely affects the DLC transparency. Moreover, this full laser-based process remains compatible with the standard microelectronic technological steps.
关键词： Diamond-Like Carbon (DLC),Graphitization,Pulsed Laser Deposition (PLD),Transparent electrodes,Laser surface annealing
更新于2025-09-12 10:27:22
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Preparation of multicolored carbon quantum dots using HNO <sub/>3</sub> /HClO <sub/>4</sub> oxidation of graphitized carbon
摘要： The microstructure of carbon quantum dots (CQDs) has a great influence on their fluorescence properties. Here, different microstructures of CQDs were synthesized by the selective oxidation of graphitized activated carbon using HNO3/HClO4 as the oxidant. We characterized the microstructure and surface chemistry of the CQDs, and the results show that the degree of graphitization of activated carbon has a significant effect on the structure and fluorescence properties of the obtained CQDs. The fluorescence of the CQD solution can be tuned from yellow to green by regulating the degree of graphitization of the activated carbon by heat treatment at high temperature (up to 2500 °C). Moreover, the increased degree of graphitization of the raw carbon precursor is beneficial for significantly reducing the fluorescence self-absorption quenching of the concentrated CQD solution. Importantly, the as-prepared CQDs have no cytotoxicity and can be used as bioimaging agents.
关键词： fluorescence properties,graphitization,bioimaging,carbon quantum dots
更新于2025-09-12 10:27:22
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Low-temperature preparation of crystallized graphite nanofibers for high performance perovskite solar cells
摘要： Integration of two-dimensional graphite nanosheets into one-dimensional graphite nano?bers is essential for deep application of graphite materials. Here, we report preparation of crystallized graphite nano?bers by nozzle-less electrospinning and subsequent low-temperature heat treatment (500 °C). Depending on this graphitized one-dimensional nanostructure, we ?rst apply the graphite nano?bers as sca?old for perovskite solar cells (PSCs), which would provide a charge transfer highway in the light absorb layer and then improve the performance of devices. A high power conversion e?ciency of 18.23% was recorded for the graphite nano?bers based PSC with high ?ll factor of 76%.
关键词： Perovskite solar cell,Charge transfer,Electrospinning,Graphite nano?bers,Graphitization temperature
更新于2025-09-12 10:27:22
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Research on the mechanism of micromachining of CVD diamond by femtosecond laser
摘要： Diamond is an excellent material in terms of hardness, thermal conductivity and chemical stability. In order to broaden its application area, the interaction mechanism of CVD diamond processed by femtosecond laser is analyzed based on laser micromachining technology. Through the threshold theory, the ablation threshold of CVD diamond is calculated. At the same time, the graphitization phase transition occurred in the diamond. The internal elements before and after the ablation of diamond by femtosecond laser are characterized by X-ray energy spectrum analysis. The changes of element content and bonding form are analyzed, and the relevant graphitization mechanism is revealed.
关键词： XPS,graphitization,ablation,CVD diamond,Femtosecond laser
更新于2025-09-11 14:15:04