High-energy Argon Ions Research Articles

Reduction of graphene oxide film on glass substrate using argon ion beam irradiation: A systematic study with X-ray photoelectron spectroscopy analysis

In our research, we explored a novel and eco-friendly method of utilizing argon ion beam irradiation to thin down graphene oxide (GO) films on glass substrates, aiming to enhance their mechanical, electrical, and optical properties. By employing high-energy argon ions, we developed a groundbreaking, environmentally conscious technique that not only permits micro-patterning directly on GO films but also facilitates concurrent material characterization. Varying the energy levels (1000, 2000, and 3000 eV) and exposure times (0 to 80 s, in 20-second increments), we meticulously examined the impact on carbon and oxygen atomic ratios of the GO using X-ray photoelectron spectroscopy (XPS) for in-depth analysis. Our findings revealed that increasing the argon ion beam energy to 2000 eV and extending the irradiation time significantly reduced oxygen content while increasing the carbon atomic ratio, indicating effective GO surface reduction. However, further increasing the energy to 3000 eV resulted in a slight increase in oxygen content and a decrease in the carbon atomic ratio compared to the energy 2000 eV, suggesting a decrease in reduction efficacy. This method's simplicity, eco-friendliness, and precision mark a significant advancement over traditional chemical reduction methods, offering a solid understanding of high-energy argon ion beam irradiation's effectiveness in GO reduction. Our comprehensive analysis, including survey and high-resolution C 1s and O 1s XPS spectra, highlights the surface chemistry modifications induced by this treatment, demonstrating the versatility of argon ion beam irradiation in producing reduced graphene oxide (rGO) for various applications.

Features of cluster ion treatment of the surface of KGd(WO<sub>4</sub>)<sub>2</sub>:Nd single crystal

The features of the surface treatment of single crystals of potassium gadolinium tungstate doped with neodymium ions with low- and high-energy cluster argon ions are considered. Two radically different treatment modes were used: low-energy for more efficient surface smoothing and high-energy for more efficient target etching. Using atomic force microscopy, the topography of the target surface was analyzed before and after cluster ion treatment. Treatment in a low-energy mode was shown to smooth out irregularities on the target surface formed by chemical-mechanical polishing at an etching depth of less than 100 nm. The root-mean-square roughness and maximum height difference of the initial and treated surfaces of potassium gadolinium tungstate doped with neodymium ions were compared. Survey X-ray photoelectron spectra of the initial surface of a KGd(WO4)2:Nd single crystal and after the cluster ion treatment in different modes are presented. The intensities of the potassium and gadolinium peaks were shown to decrease after cluster ion treatment in both modes. A significant decrease in the concentration of potassium atoms in the subsurface layer of the target is explained by the predominant sputtering of potassium as a lighter chemical element. The mutual decrease in the concentrations of gadolinium and potassium atoms can be explained by the weak bonds of these atoms in the lattice of the KGd(WO4)2:Nd single crystal.

Regulating the vacancies of nitrogen-doped carbon nanohorns for high-performance electromagnetic wave absorption.

Single-walled carbon nanohorns (SWCNHs), which are sealed on one side with a conical cap and can self-aggregate, are aggregates with spherical morphology ranging from 30 to 100 nm and include dahlia, bud, and seed structures. These SWCNHs are suitable for electromagnetic wave absorption (EMWA) due to their conductivity loss. However, conductivity loss, which is part of three primary loss mechanisms, leads to SWCNHs suffering from impedance mismatching and a narrow effective absorption bandwidth (EAB). In this work, the content of vacancy-type defects in "dahlia-like" nitrogen-doped single-walled carbon nanohorns (NSWCNHs) is regulated by dielectric barrier discharge (DBD) plasma with argon to adjust their polarization and impedance matching. The high-energy argon ions from the plasma impact the bonds between the carbon atoms and adsorbed oxygen, leading to the sputtering of oxygen atoms from the surface and resulting in an increase in surface disorder and defect content. Vacancy-type defects improved polarization loss and optimized impedance matching, leading to the satisfactory EMWA performance of NSWCNHs. The NSWCNHs exhibit an outstanding minimum reflection loss (RLmin) of -57.94 dB when subjected to argon DBD treatment for 5 minutes, achieving this remarkable result at a thickness of 1.9 mm. Additionally, the effective absorption bandwidth (EAB) can cover 4.78 GHz after a treatment period of 1 minute. These results suggest that NSWCNHs have great potential as high-efficiency EMWA materials and demonstrate a new approach for designing high-performance EMWA absorbers.

Linear-energy-transfer-independent nanoclay radio-fluorogenic gel dosimeter under energetic ion beams of 28Si14+, 40Ar18+, 56Fe26+, 132Xe54+, and 12C6+

Recently, a radio-fluorogenic gel dosimeter that can evaluate the depth–dose distribution of high-energy carbon ion beams within a radio-therapeutic dose range was reported. This study performed a detailed characterization of this gel dosimeter using five types of ion beams (high-energy carbon, silicon, argon, iron, and xenon ion beams). In addition, this paper explains the mechanism of linear-energy-transfer (LET)-independent sensitivity by evaluating the effect of the composition conditions and contribution of water-decomposed molecules and radicals. Thus, it was observed that the dosimeter could be used to evaluate the dose distribution of various high-energy heavy ion beams in bioequivalent materials. The LET range was 25–8000 eV/nm. Additionally, it was suggested that this feature was caused by two mechanisms, i.e., an increase in the reaction by hydrogen peroxide and a decrease in the contribution of OH radicals by degassing.

Optimization of Ion Energy for the Treatment of Cancerous Tumors

Background & Objectives: For over 60 years, proton beams and heavy ions have been a powerful ion therapy method for treating cancerous tumors. It is an inherent ability of high-energy ions to discharge their energy at a certain depth with high doses, which is impossible for other beams such as X-rays, gamma rays, and electron beams. Moreover, it is an excellent way to protect healthy tissues in ion therapy.
 Materials & Methods: Scientists have used radio frequency (RF) accelerators to generate high-energy ions. However, due to the high price and large devices, laser-plasma accelerators have received much attention. This paper has studied the best conditions for producing high-energy argon ions. For this purpose, the interaction of high-intensity laser pulses with argon nanoclusters is simulated. This simulation is based on the nanoplasma model by the particle in cell method (PIC).
 Results: The simulation results show that the ion energy is dependent on the parameters of the irradiated laser and the parameters of the target cluster.
 Conclusions: The energy of the ions increases with the intensity of the laser and the duration of the laser pulse. Access to higher energy ions is also possible by changing the radius of the cluster. The density of the initial atoms of the cluster is also an important parameter that influences the energy of ions.

Angular distribution measurement of high-energy argon neutral and ion in a 13.56 MHz capacitively-coupled plasma

Angular distributions of high energy neutrals and ions, impinging on an RF-biased electrode in a 13.56 MHz capacitively-coupled argon plasma were investigated. Ions and neutrals were introduced into a drift chamber that was directly connected to the RF electrode. A two-dimensional beam image was measured by a micro-channel plate. Neutral and ion beams were separated by an electrostatic deflector in the drift chamber. Angular distribution widths for ion and neutral were less than 1° at self-bias voltages above 300 V and monotonically decreased with increasing the self-bias voltage. Neutral angular distribution width was larger than that of ion, irrespective of self-bias voltage.

High energy density pulsed argon plasma synthesized nanostructured tungsten for damage mitigation under fusion relevant energetic he ion irradiation

Tungsten (W) is considered as one of the promising candidates for plasma facing components in fusion reactors since it has high threshold energy, high melting point, low threshold shock resistance, and resistance against formation of co-deposits with tritium. Despite these commendable features, helium ions produced during fusion reaction are known to alter the microstructure of tungsten. In this work, dense plasma focus (DPF) device is used to study the effect of helium ion flux on double forged tungsten samples delivering a heat load of 6.27×104J/m2 per shot. The irradiation of virgin W samples is carried out at 5, 10, and 15 DPF helium shots. High heat loads resulted in blisters and micro-cracks on the sample surface. With an increase in the number of shots, the density of the blisters increased and craters on the W surface burst followed by re-solidification of the melted and sputtered surface. Surface nano-structurization, with nanoparticle formation, of W samples (nano-W) is realized by high-energy argon ion exposure of virgin samples in an argon filled DPF device. The average size of nanoparticles is found to increase with the number of shots and also leads to particle agglomeration. At 10 shots, uniformly distributed highly dense nanoparticles of 20–50 nm size have been synthesized. The nano-W samples are then irradiated by instability-accelerated high-energy helium ions in helium filled DPF device for 5, 10, and 15 shots to simulate fusion relevant conditions. The presence of the trapped helium bubbles in virgin-W and nano-W are examined by BSE imaging and XRD, respectively. The nanostructured tungsten shows improved structure and surface properties against Helium ion irradiation.

High-Voltage 4H-SiC Schottky Diodes with Field-Plate Edge Termination

High-voltage (2000V) 4H-SiC Schottky diodes are fabricated. To suppress the premature breakdown at the edge of diode structures, a field plate is formed as the edge termination. In this plate, an insulator layer is formed via the self-aligned implantation of high-energy (53 MeV) argon ions into 4H-SiC. To mask the active region of the diodes, 10–12-μm-thick nickel columns with vertical walls are grown on Schottky contacts by local electrochemical deposition. A comparison of the current–voltage characteristics of terminated and nonterminated diodes shows that the forward current–voltage characteristics barely degrade after implantation, whereas the reverse current–voltage characteristics are greatly improved. Both the forward and reverse current–voltage characteristics of terminated diodes are well described in terms of the classical thermionic emission model if lowering of the Schottky-barrier height with increasing bending of energy bands is taken into account.

On the formation of temperature-induced defects at the surface of TEM specimens prepared from TiAl using high-energy Gallium and low-energy Argon ions

ABSTRACT Specimens for transmission electron microscopic (TEM) investigations were prepared from γ titanium aluminide alloys with Gallium and Argon ions using a focused ion beam (FIB) and a precision ion polishing system (PIPS). Preparation to electron transparency by Gallium ions alone leads to the formation of crystalline platelets of the α titanium phase at the specimen surfaces, revealed through conventional and high resolution (HR) TEM analysis. The platelets are assumed to precipitate from priorly formed amorphous layers. The required crystallisation temperature of about 480°C is generated through the ion bombardment implying that the γ titanium aluminides can be heated substantively during sputtering. The primary reason for this is the restricted transfer of heat away from the beam impact point when the specimen thickness comes close to the beam diameter. The formation of the platelets can be avoided by terminating the Gallium ion treatment prior to that, while providing for a sufficient thermal bonding of the specimen to the grid as well and polishing off the remaining material by Argon ions, which are much less focused and less energetic, so that the local heat peaks are reduced.

MODIFICATION OF YSZ PROPERTIES BY HIGH ENERGY IONS OF ARGON AND OXYGEN

The influence of high-energy oxygen and argon ions irradiation on the structure and conductive properties of YSZ of various composition has been studied. It was shown that irradiation with YSZ ions causes minor failures in the structure of the near-surface regions of complex oxide, but does not cause any change in the type of crystal lattice. Apparently, the latter is due to the fact that both defects and implanted ions are mainly located quite deep from the surface of YSZ. Along with this, high radiation resistance of YSZ near-surface layers with the concentration of Y2O3 of 10 and 15 mol. %, is apparently due to the high concentration of oxygen vacancies in the initial unirradiated materials, which act as effective recombination centers for defects formed during irradiation. In the samples of ZrO2 + 3 mol. % Y2O3 composition, the concentration of vacancies is lower, and during irradiation there is a notable yield of oxygen from YSZ along with recombination. This leads to decrease in oxygen concentration and increase in zirconium concentration on the surface of the complex oxide. The values of the activation energies of the oxygen-ionic conductivity of the studied materials have been determined. It was noted that irradiation of YSZ with heavy ions in some cases can cause the improvement in the oxygen-ionic conductivity of these materials.

The Influence of Heat Treatment on the Electrical Characteristics of Semi-Insulating SiC Layers Obtained by Irradiating n-SiC with High-Energy Argon Ions

Irradiation of crystalline n-type silicon carbide (n-SiC) with high-energy (53-MeV) argon ions was used to create near-surface semi-insulating (i-SiC) layers. The influence of subsequent heat treatment on the electrical characteristics of i-SiC layers has been studied. The most high-ohmic ion-irradiated i-SiC layers with room-temperature resistivity of no less than 1.6 × 1013 Ω cm were obtained upon the heat treatment at 600°C, whereas the resistivity of such layers heat-treated at 230°C was about 5 × 107 Ω cm.

Влияние термообработки на электрические характеристики полуизолирующих слоев, полученных с помощью облучения n-SiC высокоэнергетическими ионами аргона

AbstractIrradiation of crystalline n -type silicon carbide ( n -SiC) with high-energy (53-MeV) argon ions was used to create near-surface semi-insulating ( i -SiC) layers. The influence of subsequent heat treatment on the electrical characteristics of i -SiC layers has been studied. The most high-ohmic ion-irradiated i -SiC layers with room-temperature resistivity of no less than 1.6 × 10^13 Ω cm were obtained upon the heat treatment at 600°C, whereas the resistivity of such layers heat-treated at 230°C was about 5 × 10^7 Ω cm.

Fabrication of nanoporous Si electrocathode by high-energy argon ion irradiation for improved electrocatalytic hydrogen production

Developing a cost-effective material to replace Pt catalysts for hydrogen evolution reaction (HER) holds great promising for clean energy technologies. In this work, we developed a simple way to prepare nanoporous Si by argon ion irradiation at 90 keV to fluences of 0.5, 1, 2 × 1017 ions/cm2. After post-irradiation annealing at 700 °C in vacuum (2 × 10−4 pa) for 5 h, the nanoporous Si was formed which displays largely enhanced electrocatalytic water splitting compared with the unirradiated Si. We also investigated the influence of fluence on morphology and the HER performance of the electrocathodes. It was found that 1 × 1017 Ar+ ions/cm2 irradiated Si showed the highest HER performance. The largely enhanced HER activity comes from the unique morphology which results by Ar+ ions irradiation and post-irradiation annealing. We further fabricated electrocathodes by coating Ni film on the nanoporous Si, significant improvement of the HER performance compared with Ni coated planar Si was found. Using the ion irradiation technology, we developed a new method to fabricate electrocathode with large specific surface area for largely enhanced hydrogen evolution reaction activities.

The Effects of HZE Particles, γ and X-ray Radiation on the Survival and Genetic Integrity of Halobacterium salinarum NRC-1, Halococcus hamelinensis, and Halococcus morrhuae.

Three halophilic archaea, Halobacterium salinarum NRC-1, Halococcus hamelinensis, and Halococcus morrhuae, have been exposed to different regimes of simulated outer space ionizing radiation. Strains were exposed to high-energy heavy ion (HZE) particles, namely iron and argon ions, as well as to γ radiation (60Co) and X-rays, and the survival and the genetic integrity of the 16S rRNA gene were evaluated. Exposure to 1 kGy of argon or iron ions at the Heavy Ion Medical Accelerator in Chiba (HIMAC) facility at the National Institute for Radiological Sciences (NIRS) in Japan did not lead to a detectable loss in viability; only after exposure to 2 kGy of iron ions a decline in survival was observed. Furthermore, a delay in growth was manifested following exposure to 2 kGy iron ions. DNA integrity of the 16S rRNA was not compromised up to 1 kGy, with the exception of Hcc. hamelinensis following exposure to argon particles. All three strains showed a high resistance toward X-rays (exposed at the DLR in Cologne, Germany), where Hcc. hamelinensis and Hcc. morrhuae displayed better survival compared to Hbt. salinarum NRC-1. In all three organisms the DNA damage increased in a dose-dependent manner. To determine a biological endpoint for survival following exposure to γ radiation, strains were exposed to up to 112 kGy at the Beta-Gamma-Service GmbH (BGS) in Germany. Although all strains were incubated for up to 4 months, only Hcc. hamelinensis and Hcc. morrhuae recovered from 6 kGy of γ radiation. In comparison, Hbt. salinarum NRC-1 did not recover. The 16S rRNA gene integrity stayed remarkably well preserved up to 48 kGy for both halococci. This research presents novel data on the survival and genetic stability of three halophilic archaea following exposure to simulated outer space radiation. Key Words: Halophilic archaea-Radiation-Survival. Astrobiology 17, 110-117.

Semi-insulating 4H-SiC layers formed by the implantation of high-energy (53 MeV) argon ions into n-type epitaxial films

It is shown that 9-μm-thick semi-insulating surface layers can be formed in moderately doped n-type silicon carbide (donor concentration 2 × 1016 cm–3) via the comparatively low-dose (7 × 1011 cm–2) implantation of high-energy (53 MeV) argon ions. The free-carrier removal rate is estimated at ~104 cm–1. The resistivity of the semi-insulator is no less than 7 × 1012 Ω cm. Analysis of the monopolar current of electron injection into the semi-insulator shows that the impurity-conductivity compensation is due to radiationinduced defects pinning the equilibrium Fermi level at a depth of 1.16 eV below the conduction-band bottom. The density of defect states at the Fermi level is 2.7 × 1016 cm2 eV–1.

Reconsideration of metal surface sputtering due to bombardment of high-energy argon ion particles: a molecular dynamics study

Some interesting aspects of metal surface sputtering phenomenon are numerically investigated in this work using the molecular dynamics approach. Along with that, we have carried out a critical analysis of the interaction potentials typically used for modeling. Two metallic surfaces, viz., copper, Cu(100), and nickel, Ni(100), are chosen for study that are bombarded by argon ions at various energies and angles of projection. The sputtering yield is calculated by performing molecular dynamics simulations, and the same is compared with experiments and theoretical predictions wherever possible. Furthermore, other interesting parameters like the kinetic energy, velocity, and scattering angle distribution for sputtered and incident atoms are presented and discussed. Through different case studies, the present work emphasizes on the importance of interaction model used for metal surface modeling for a realistic numerical reproduction of the complex metal surface sputtering process.

Exciton Localization and Optical Properties Improvement in Nanocrystal-Embedded ZnO Core–Shell Nanowires

We present a comparative investigation of the morphological, structural, and optical properties of vertically aligned ZnO nanowires (NWs) before and after high energy argon ion (Ar(+)) milling. It is found that the outer regions of the as-grown sample change from crystalline to amorphous, and ZnO core-shell NWs with ZnO nanocrystals embedded are formed after Ar(+) milling. Optical properties of the ZnO NWs have been investigated systematically through power and temperature dependent photoluminescence measurements, and the phenomenon of exciton localization as well as the relevant favorable photoluminescence characteristics is elucidated. Interestingly, under high density optical pumping at room temperature, coherent random lasing action is observed, which is ascribed to exciton localization and strong scattering. Our results on the unique optical properties of localized exciton in ZnO core-shell nanostructures shed light on developing stable and high-efficiency excitonic optoelectronic devices such as light-emitting diodes and lasers.

Application of RF Argon Plasma to Enhance Hydrophobic Properties of Fluoropolymer Pre-deposited Paper

Tetrafluoroethane (TFE) pre-deposited paper substrates were exposed to an inert gas (argon) plasma environment in order to convert the hydrophilic to hydrophobic surfaces via grafting and/or cross-linking of the fluorinated layer on the surface of paper, while also improving coating uniformity. The XPS spectrum indicates changes in the nature and relative ratios of the surface functionalities. The application of 300 W RF-power argon plasma (at 10 min and 300 mTorr) created a very highly hydrophobic character (water contact angle, = 120°). A typical high resolution (HR) C1s XPS spectrum of argon-plasma treated TFE pre-deposited paper contains four distinct peaks at 285 (C–C), 285.7 (C–CF), 286.7 (C–O and C–CF2) and 291 eV (CF2–C) binding energies. The C1s region indicates narrowing of the spectrum and complete removal of the CF3–CF (292.5 eV) peak. This change in the shape of HR C1s spectrum also indicates loss of fluorine from the TFE pre-deposited paper with argon exposure compared to only TFE pre-deposited paper. The high-energy argon ions appear to etch the uppermost region, leading to micro-roughening of the paper surface. AFM micrographs reveal re-arrangement of the paper surface with argon plasma exposure. The water absorption of paper coated with TFE alone only decreased by 1.3%. However, after argonplasma treatment of the TFE pre-deposited paper, the water absorption was reduced aproximately by 22% compared to virgin paper.

Experimental study and simulation of the residual activity induced by high-energy argon ions in copper

Abstract The paper presents new experimental results and FLUKA-simulations of residual activation induced by high-energy argon ions in copper. It follows the previous residual activation studies performed at GSI Helmholtzzentrum fur Schwerionenforschung in Darmstadt with uranium ions as a preparatory work for constructing the FAIR facility. Copper samples were irradiated by 1 GeV/u and 500 MeV/u 40Ar ions and investigated by gamma-ray spectroscopy. The samples were irradiated in the stacked-foil geometry. The isotopes with dominating contribution to the total residual activity were identified and their partial activities were quantified. Depth-profiling of the partial residual activities of all identified isotopes was performed by measurements of individual target foils. The experimental results were compared with simulations by the FLUKA-code. A satisfactory agreement between the experiment and the simulations was observed.

Suppression of High-Energy Backscattered Particles in Magnetron Plasma Using Cylindrical Cathode

In a conventional argon magnetron source using a planar cathode (target), numerous backscattered high-energy (100–200 eV) argon atoms and ions impinge on a substrate, often causing damage in sputtered films. In order to reduce such energetic particles, a cylindrical magnetron source is proposed where most of the high-energy particles are confined inside a cylindrical cathode with low-energy particles impinge on the substrate outside the cylinder. Ar+ ion energy distributions of planar and cylindrical magnetron sources are measured using a mass spectrometer with an energy analyzer. In the cylindrical magnetron, a marked decrease in the energetic component is observed compared with that in the planar magnetron. A Monte Carlo code is developed to simulate energy distributions of Ar and Ar+ in the cylindrical magnetron source. Simulated Ar+ energy distributions are in good agreement with the measurements, reproducing the experimental results.