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Formation of a Track Template during PETP Irradiation with High-Energy Helium Ions for the Template Synthesis of Regular Microstructures
摘要： The features of obtaining track membranes (TMs) with the help of a classical cyclotron situated at Tomsk Polytechnic University are discussed. It is demonstrated that TMs can be employed as templates. The results of research into columnar nanostructures formed with the help of a TM template are presented. The creation of regular microstructures is investigated using deep X-ray lithography with synchrotron radiation and templates made of track membranes.
关键词： track membrane,argon ions,synchrotron radiation,helium ions,polyethylene terephthalate
更新于2025-09-23 15:23:52
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Many-electron character of two-photon above-threshold ionization of Ar
摘要： The absolute generalized cross sections and angular distribution parameters of photoelectrons for the two-photon above-threshold 3p ionization of Ar were calculated in the exciting photon energy range from 15.76 to 36 eV. The correlation function technique developed earlier was extended for the case when an intermediate-state function is of a continuum-type. We show that two-photon ionization of Ar near the 3p4 threshold to a large extent is determined by the (3p (cid:2)(cid:2)(cid:3) εd )2 two-photon absorption via the giant resonance. This many-electron correlation causes (i) an increase of the photoionization cross sections by more than a factor of 3; and (ii) the appearance of resonances in the exciting-photon energy range of the doubly excited states. The predictions are supported by a good agreement between length and velocity results obtained after taking into account the higher-order perturbation theory corrections.
关键词： angular distribution,two-photon ionization,above-threshold ionization,many-electron correlations,argon,generalized cross sections
更新于2025-09-23 15:23:52
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Chemical imaging of buried interfaces in organic-inorganic devices using FIB-ToF-SIMS
摘要： Organic-inorganic hybrid materials enable the design and fabrication of new materials with enhanced properties. The interface between the organic and inorganic materials is often critical to the device’s performance and therefore chemical characterization is of significant interest. Since the interfaces are often buried, milling by focused ion beams (FIB) to expose the interface is becoming increasingly popular. Chemical imaging can subsequently be obtained using secondary ion mass spectrometry. However, the FIB milling process damages the organic material. In this study, we make an organic-inorganic test structure to develop a detailed understanding of the processes involved in FIB milling and SIMS imaging. We provide an analysis methodology that involves a “clean-up” process using sputtering with an argon gas cluster ion source to remove the FIB induced damage. The methodology is evaluated for two additive manufactured devices, an encapsulated strain sensor containing silver tracks embedded in a polymeric material and a copper track on a flexible polymeric substrate created using a novel nanoparticle sintering technique.
关键词： FIB,additive manufacturing,hybrid interfaces,ToF-SIMS,polymer,Argon cluster,milling
更新于2025-09-23 15:22:29
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Sustainable thermionic emission in CO2, helium and argon surroundings
摘要： Thermionic materials are commonly used in high vacuum (< 10?5 mbar). We measured thermionic emission of different doped metal-oxides cathodes – Zr doped Gd2O3 and Nb doped SrTiO3 (1 1 1) – in a CO2 surrounding, at T = 1300 °C and ～10?4 mbar ≤ p ≤ 300 mbar. Experimental setup validation and reference data were provided by measurements using cathodes made of CeB6, a commercial thermionic material, and by using either helium or argon as the surrounding gas. The study’s results could be used when examining enhancement of CO2 reduction to CO using vibration’s excitation. The thermionic emission of all cathodes decreased gradually as the pressure increased, as expected, but the exposure to CO2 did not cause a deterioration of the Zr doped Gd2O3 cathodes. They retained a reasonable emission, of ～60% and ～40% of the current in vacuum, at a CO2 pressure of 50 mbar and 300 mbar, respectively, over 20 operation hours. The data suggest that in the presence of significant gas pressure in the cathodes surrounding, the electric dipole of CO2 molecules and the cathode’s surface roughness may induce several mechanisms, which could affect the current emission.
关键词： Surface,CO2 helium argon,CO2 reduction,Thermionic emission
更新于2025-09-23 15:22:29
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Optical analysis during reduction of nitric oxide in microwave-induced plasma promoted by activated cokes at atmospheric pressure
摘要： Emission from microwave (MW)-induced argon plasma promoted by a bed of activated coke granules was analyzed spectroscopically during non-catalytic reduction of nitric oxide (NO) at atmospheric pressure. The spectral analysis with a high resolution revealed that strong 5 peaks were recognized in a similar wavelength region to N2+ first negative band when NO molecules were included in argon plasma. The strongest peak is caused by the Ar(II) ions excited with energy corresponding to 388.033 nm in the progress of atomic transition 3s23p4(3P)4d 4D1/2 → 3s23p4(3P)4p 4D°1/2. This transition must be enhanced by an interaction with any intermediates or radical species yielded during NO reduction reactions. The plasma temperatures were determined by Boltzmann plots from intensities of any two peaks in the spectral band. The temperature was significantly different dependently on choice of two peaks, whose fact is implying non-equilibrium plasma. The maximum temperature was recognized at a high level of 40,000 K due to the activation during the reactions. The images of the plasma observed by high-speed camera showed dynamic features so that MW discharge like streamer was generated frequently in the reactor. The reaction rate could be correlated with the ratio of the area dominated by dynamic plasma to the cross section in the reactor.
关键词： High-speed camera images,Argon plasma,Microwave discharge,Spectroscopic measurement,de-NOx
更新于2025-09-23 15:22:29
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Homogeneous Large-area Quasi-freestanding Monolayer and Bilayer Graphene on SiC
摘要： In this study, we first show that the argon flow during epitaxial graphene growth is an important parameter to control the quality of the buffer and the graphene layer. Atomic force microscopy (AFM) and low-energy electron diffraction (LEED) measurements reveal that the decomposition of the SiC substrate strongly depends on the Ar mass flow rate while pressure and temperature are kept constant. Our data are interpreted by a model based on the competition of the SiC decomposition rate, controlled by the Ar flow, with a uniform graphene buffer layer formation under the equilibrium process at the SiC surface. The proper choice of a set of growth parameters allows the growth of defect-free, ultra-smooth and coherent graphene-free buffer layer and bilayer-free monolayer graphene sheets which can be transformed into large-area high-quality quasi-freestanding monolayer and bilayer graphene by hydrogen intercalation. AFM, scanning tunneling microscopy, Raman spectroscopy and electronic transport measurements underline the excellent homogeneity of the resulting quasi-freestanding layers. Electronic transport measurements in four-point probe configuration reveal a homogeneous low resistance anisotropy on both μm- and mm scales.
关键词： SiC terrace steps,polymer assisted sublimation growth,Epitaxial graphene,freestanding bilayer graphene,argon gas flow,graphene buffer layer,monolayer graphene,resistance anisotropy,large-scale graphene growth,freestanding monolayer graphene
更新于2025-09-23 15:22:29
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Analysis of helium used as protective gas in Laser Metal Deposition of Ti6Al4V highly reactive material
摘要： Laser Material Deposition (LMD) is an additive manufacturing near-net-shape process. Metal powder particles are molten by means of a laser heat source and added to a substrate creating geometries. This technology offers the possibility of generating coatings, repairing damaged high-added-value parts, and manufacturing components with complex 3D geometries. Many industrial sectors, including aerospace and die and mold industries, are interested in this process due to its capabilities and the wide range of materials that can be used with it. Previous works aimed to develop a protective gas module to be able to process highly reactive materials without the necessity of a complete inert atmosphere inside the machine. Additionally, the influence of a mixture of argon and helium on the LMD process for other non-highly reactive alloys was evaluated. Hence, the present work aims to broaden the understanding of how the combination of these two factors may affect the LMD process, combining these previous studies and evaluating the phenomenon for a highly reactive alloy like Ti6Al4V. The study involves the melt-pool temperature measurement and characterization of the deposited clads variating not only the composition of the protective gas but also the flow rates.
关键词： LMD,Ti6Al4V,Helium,Titanium,Shielding gas,protective atmosphere,He,Laser Metal Deposition,Argon,Ar
更新于2025-09-23 15:21:01
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Argon clustering in silicon under low-energy irradiation: Molecular dynamics simulation with different Ar–Si potentials
摘要： In this paper, the authors carried out a molecular dynamics simulation of crystal and amorphous silicon sputtering by low-energy (200 eV) Ar ions at normal incidence. The gradual damage of silicon caused by the ion bombardment was taken into account in order to study the dynamics of argon accumulation and clustering. For describing interatomic Ar–Si interaction, they used three different potentials: two binary screened Coulomb potentials (Molière and Ziegler–Biersack–Littmark) and the potential developed on the basis of density functional theory. The obtained results demonstrated the substantial influence of the chosen Ar–Si potential on calculated sputtering yields and on the processes of argon accumulation and clustering.
关键词： silicon sputtering,molecular dynamics simulation,Ar–Si potentials,argon clustering,low-energy irradiation
更新于2025-09-23 15:21:01
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Direct measurement of the ionization source rate and closure of the particle balance in a helicon plasma using laser induced fluorescence
摘要： A detailed study of the ?ows of ion and neutral argon populations in a helicon plasma was carried out. Understanding the principle ion sinks and sources of neutral fueling is essential to understanding the ability of helicon wave heating to create high density plasmas. This heating mechanism and the neutral fueling required to sustain it and perhaps manipulate the axial density pro?le in long cylindrical plasmas are an active research topic for advanced plasma wake?eld accelerator concepts. Using laser induced ?uorescence (LIF) of ion and neutral argon species, an ion ?ux of up to 2:5 (cid:2) 1021 m(cid:3)2 s(cid:3)1 was measured leaving the core of a helicon plasma with a peak electron density of 4:0 (cid:2) 1018 m(cid:3)3. Taking the divergence of the axial ion ?ux pro?le yields a minimum ionization rate estimate of 2 (cid:2) 1021 m(cid:3)3 s(cid:3)1, and including the radial divergence increases the estimated ionization rate to approximately 1022 m(cid:3)3 s(cid:3)1. Neutral ?ow velocities measured using LIF reveal a circulatory fueling and loss mechanism with distinct zones where radial or axial sources and sinks dominate.
关键词： laser induced fluorescence,ionization source rate,argon,helicon plasma,particle balance
更新于2025-09-23 15:19:57
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Thermometry in a Gas Discharge Cell of an Optical Wavelength Calibrator
摘要： Temperature and pressure in a sealed Ar cell of an optical wavelength calibrator are measured using diode laser spectroscopy. The values of the thermodynamic parameters allowed determination of the fluctuations of the shift of the argon line at 811.5 nm. The expected fluctuation amplitude appears lower than ±15 MHz. The result obtained indicates the applicability of the studied calibrator as an optical reference and the correctness of previous measurements of pressure shift coefficients of the 811.5 nm argon line.
关键词： thermometry,diode-laser spectroscopy,optical calibrator,low pressure RF discharge,spectral line pressure shift,argon
更新于2025-09-19 17:15:36