High-energy Ion Beam Irradiation Research Articles

Resistive Gas Sensors Based on 2D TMDs and MXenes.

ConspectusGas sensors are used in various applications to sense toxic gases, mainly for enhanced safety. Resistive sensors are particularly popular owing to their ability to detect trace amounts of gases, high stability, fast response times, and affordability. Semiconducting metal oxides are commonly employed in the fabrication of resistive gas sensors. However, these sensors often require high working temperatures, bringing about increased energy consumption and reduced selectivity. Furthermore, they do not have enough flexibility, and their performance is significantly decreased under bending, stretching, or twisting. To address these challenges, alternative materials capable of operating at lower temperatures with high flexibility are needed. Two-dimensional (2D) materials such as MXenes and transition-metal dichalcogenides (TMDs) offer high surface area and conductivity owing to their unique 2D structure, making them promising candidates for realization of resistive gas sensors. Nevertheless, their sensing performance in pristine form is typically weak and unacceptable, particularly in terms of response, selectivity, and recovery time (trec). To overcome these drawbacks, several strategies can be employed to enhance their sensing properties. Noble-metal decoration such as (Au, Pt, Pd, Rh, Ag) is a highly promising method, in which the catalytic effects of noble metals as well as formation of potential barriers with MXenes or TMDs eventually contribute to boosted response. Additionally, bimetallic noble metals such as Pt-Pd and Au/Pd with their synergistic properties can further improve sensor performance. Ion implantation is another feasible approach, involving doping of sensing materials with the desired concentration of dopants through control over the energy and dosage of the irradiation ions as well as creation of structural defects such as oxygen vacancies through high-energy ion-beam irradiation, contributing to enhanced sensing capabilities. The formation of core-shell structures is also effective, creating numerous interfaces between core and shell materials that optimize the sensing characteristics. However, the shell thickness needs to be carefully optimized to achieve the best sensing output. To reduce energy consumption, sensors can operate in a self-heating condition where an external voltage is applied to the electrodes, significantly lowering the power requirements. This enables sensors to function in energy-constrained environments, such as remote or low-energy areas. An important advantage of 2D MXenes and TMDs is their high mechanical flexibility. Unlike semiconducting metal oxides that lack mechanical flexibility, MXenes and TMDs can maintain their sensing performance even when integrated onto flexible substrates and subjected to bending, tilting, or stretching. This flexibility makes them ideal for fabricating flexible and portable gas sensors that rigid sensors cannot achieve.

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.

Influence of 120 MeV Au Ion Irradiation on Phase Transition, Surface, and Optical Properties of Lead‐Free (K,Na)NbO3 Films

High energy ion beam irradiation is an important tool to engineer the properties of multifunctional materials for diverse applications. The present study reports the impact of 120 MeV Au ion beam irradiation on structural and luminescence properties of (K,Na)NbO3 (KNN) films. The increase in ion fluence has resulted in crystalline‐to‐crystalline and crystalline‐to‐amorphous phase transitions at room temperature. The dense grain‐like morphology of crystalline films gets transformed into clusters of nano‐sized grains after irradiation, and the grain boundaries are diffused at higher fluence. X‐ray photoelectron spectroscopy results indicate the evaporation of K‐species from the surface after irradiation. The relative elemental ratio and film's thickness were estimated using Rutherford backscattering spectrometry, and subsequently, KNN/Si interface analysis was also carried out. The increase in optical band gap after irradiation is correlated to the suppression of extended band tails. An intense photoluminescence emission in the UV region is observed, and the intensity increases abruptly after the crystalline‐to‐amorphous phase transition, where the grain boundaries merge with nearby ones. The impact of high electronic energy loss in KNN enhanced the probability of radiative recombination. The obtained results demonstrate the possible use of KNN for optoelectronic applications.

Defects engineering and enhancement in optical and structural properties of 2D-MoS2 thin films by high energy ion beam irradiation

Transition metal dichalcogenides (TMDs) like molybdenum disulfide (MoS2) have extra-ordinary physical and chemical peculiarities which can be additionally modified by ion beam irradiation. In the present work, we illustrate the tailoring of MoS2 thin films by employing ion beam irradiation. Silicon ion beam with 100 MeV energy was used to have an apparent impact on structural, morphological and optical properties of MoS2 thin films. Sputtered MoS2 films were irradiated with 100 MeV Si8+ ion beam with a fluence of 1E13 ions/cm2. The X-ray diffraction (XRD) technique validates the structural analysis of MoS2 films with hexagonal phase and reduction in the crystallinity is observed after irradiation owing to the generation of defects by high energy ion beam irradiation. MoS2 thin films display Raman modes at ⁓378 cm−1 and ⁓411 cm−1 corresponding to the one molybdenum atom and two sulfur atoms of the same layer vibrates in the converse in-plane and out-of-plane direction respectively. Intensity of Raman peaks is reduced after the employment of ion beam irradiation. Slight reduction in transmittance is observed after irradiation. The intensity of broad PL emission spectra observed at 360 nm showed the enhancement in PL intensity after ion beam irradiation. Rutherford backscattering spectroscopy (RBS) substantiated the presence of molybdenum (Mo) and sulfur (S) elements and 440 nm thickness of the samples. The investigation of the thickness and atomic fraction of the specimen was also governed by simulating the RBS spectrum using SIMNRA software. To demonstrate the changes occur in grain size and surface roughness parameters in ion irradiated and pristine MoS2 thin films were analyzed by AFM (atomic force microscopy). The alterations of binding energy of Mo 3d and S 2p region of MoS2 pristine and ion irradiated thin films were analyzed by X-ray photoelectron spectroscopy (XPS).

Hydrophilicity Improvement of Polymer Surfaces Induced by Simultaneous Nuclear Transmutation and Oxidation Effects Using High-Energy and Low-Fluence Helium Ion Beam Irradiation.

Two commodity polymers, polystyrene (PS) and high-density polyethylene (HDPE), were irradiated by high-energy He ion beams at low fluence to examine the wettability changes at different fluences. The water contact angles of the PS and HDPE surfaces were reduced from 78.3° to 46.7° and 81.5° to 58.5°, respectively, upon increasing the fluence from 0 to 1 × 1013 He2+/cm2 for irradiation durations ≤4 min. Surface analyses were performed to investigate these wettability changes. Surface texture evaluations via scanning electron and atomic force microscopies indicated non-remarkable changes by irradiation. However, the chemical structures of the irradiated polymer surfaces were notable. The high-energy He ions induced nuclear transmutation of C to N, leading to C–N bond formation in the polymer chains. Further, C–O and C=O bonds were formed during irradiation in air because of polymer oxidation. Finally, amide and ester groups were generated by irradiation. These polar groups improved hydrophilicity by increasing surface energies. Experiments with other polymers can further elucidate the correlation between polymer structure and surface wettability changes due to high-energy low-fluence He ion irradiation. This method can realize simple and effective utilization of commercial cyclotrons to tailor polymer surfaces without compromising surface texture and mechanical integrity.

A novel method to enhance the catalytic activity of PtRu on the support using CeO2 by high-energy ion-beam irradiation

As a novel method for the preparation of highly-active anode catalysts for direct methanol fuel cells (DMFCs), the effect of high-energy ion irradiation on the CeO2 embedded carbon nanofiber support (CECNF) of the PtRu/CECNF catalyst, that has been reported as a very active catalyst, on the methanol oxidation activity as well as the crystalline structure of the support materials were investigated. PtRu/CECNFs were prepared using the CECNFs that were irradiated by high-energy ion-beams under the different conditions, i.e., using 127 MeV Ar ions, 310 MeV Kr ions and 350 MeV Xe ions with different ion-fluences from 5 × 1011 ions cm−2 to 1 × 1013 ions cm−2. A change in the activity was observed at the low electrode potentials below 0.7 V vs RHE. An almost two times higher current density at 0.6 V vs RHE compared to that without irradiation was obtained by the Ar ion irradiation with the ion-fluence at around 5 × 1011 ions cm−2, while a higher ion-fluence reduced the activity. The reduction of the CeO2 crystalline size with the increase in the ion-fluence was observed by XRD measurements. The change in the catalytic activity roughly correlated with the increase in the lattice distance of CeO2 suggesting that the generated oxygen atom vacancies enhanced the activity.

Facile preparation of fluorescent nanodiamond based polymer nanoparticles via ring-opening polymerization and their biological imaging.

Fluorescent nanodiamond (ND) has been regarded as one of the most promising fluorescent nanoprobes owing to their chemical inert, biocompatibility, optical properties, and rich surface chemistry. The fluorescent ND has been mainly fabricated through high-energy ion beam irradiation of type Ib diamonds and subsequent thermal annealing. The generation of nitrogen-vacancy centers is the reason for the fluorescence. However, the physical method is relatively complicated and it need to expensive equipment as well as high cost. On the other hand, the resultant fluorescent ND particles are lack of functional groups and difficult to be dispersed in aqueous solution. Therefore, the development of facile methods to direct preparation of fluorescent ND and surface modification with functional polymers is of great research interest for expanding the biomedical applications of fluorescent ND. In this report, a facile strategy was reported for the first time to prepare hydrophilic polymers functionalized fluorescent ND (named as ND-PhE-PETOx) composites through the ring-opening polymerization and simultaneous simple nucleophilic substitution reaction using the non-fluorescent detonation ND as the raw material. The obtained fluorescent ND composites were characterized by various characterization techniques in details. The as-obtained ND-PhE-PETOx composites exhibit high water dispersibility, low toxicity and strong fluorescence intensity. Cell uptake results indicating that the fluorescent ND based composites can be effectively internalized by cells. Taken together, we have developed a novel and simple method for the preparation of fluorescent ND based composites, which show excellent physicochemical properties and great potential for biomedical applications.

Dense electronic excitation induced modifications in nanocrystalline zirconium oxide thin films: Detailed analysis of optical and surface topographical

Ion irradiation is known to create structural disorder and crystallization improvement in the material. In the present study, focus is on the effect of high energy ion beam irradiation on the optical, surface morphological and structural properties of ZrO2 thin films of 200 nm grown on Si and glass substrate by RF sputtering technique. The prepared thin films were annealed at 600 °C and irradiated with swift heavy ions (SHI) of 120 MeV Ti9+ ion beam with varied fluences ranging from 5E11 to 2E13 ions/cm2. SRIM simulation reveals that the electronic energy losses (Se) dominate over the nuclear energy losses (Sn) and the projected range of the Ti ions was found to be 13.64 μm. Optical properties were studied by using UV-Vis and Photoluminescence (PL) spectroscopy. The transmittance of the ZrO2 samples lies in the range of (46–79%) and the Tauc's plot was used to calculate the optical band gap. PL spectroscopy demonstrates the emission spectrum using the excitation wavelength of 310 nm. The influence of SHI irradiation on the surface morphology of ZrO2 thin films was examined by Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscopy (FESEM). The sectional analysis of AFM images reveals that the grain size decreases with increasing the ion fluences and lies in the range of 51-29 nm. The structural analysis of pristine and irradiated samples was done by using X-ray diffraction (XRD) technique. The crystallite size increases for the lower fluence up to 1E12 ions/cm2 and decreases at higher fluence due to the development of fragmentation by the effect of SHI irradiation. XRD patterns were used to calculate strain, stress, dislocation density and texture coefficient of the ZrO2 samples. Rutherford Backscattering Spectrometry (RBS) ensures the presence of Zr and O elements with the atomic fraction of 1: 2 and thickness (200 nm) of the samples was confirmed by simulating the RBS spectrum. The modifications induced in the properties of the ZrO2 thin films were mainly due to the electronic energy losses through the inelastic collision in the target material.

Analysis of grid electrode assisted plasma based ion implantation system and application to ion beam assisted deposition for insulator substrates

A grid electrode assisted plasma based ion implantation system, which was originally designed only for ion implantation on insulator substrates, was investigated as a system of sputter deposition with high energy ion beam irradiation. When pulses of negative high voltage were applied to grid electrodes immersed in argon plasmas, high energy ions were observed to bombard the surface of the grid electrodes during the rise and plateau times of the pulses, using particle-in-cell (PIC) simulations. The resulting sputter deposition of atoms on the substrate from the stainless steel grid electrodes was confirmed by X-ray photoelectron spectroscopy. During the fall time of the pulses, PIC simulations indicated high energy ion beams of pseudowaves bombarded the surface of the substrate. Thus we verified that by using grid electrodes, ion beams can irradiate the insulator substrate after the sputter deposition within the time scale of a single pulse. In the proposed configuration, problems due to high voltage on insulator can be avoided because the insulator substrates float in plasmas for the entire process. Finally, we discuss potential application of the system for ion beam assisted deposition as a compact plasma based ion implantation and deposition system, which does not require a separate sputtering system.

Effects of high-energy ion-beam irradiation on structural and optical properties of (Mg0.95Co0.05)TiO3 thin films

ABSTRACTWe report the structural and optical properties of high-energy ion-beam irradiated Co-doped magnesium titanate thin films. (Mg0.95Co0.05)TiO3 (MCT) thin films were deposited on quartz substrates using radio frequency magnetron sputtering. Subsequently, the films were annealed for crystallinity and were irradiated with 100 MeV Ag ions by varying the ion fluence. The X-ray diffraction patterns of the films before and after the irradiation were refined using the Rietveld refinement and the variations in the lattice parameters were correlated with the ion fluence. Although, annealing of thin films results in an enhancement in refractive index and optical bandgap, the ion fluence induces significant changes in the refractive index and optical bandgap. Atomic force microscopy is employed to study the surface morphology of the films. The impact of ion fluence on structural and optical properties of MCT thin films has been investigated.

Development of high-energy ion-beam irradiation techniques for radiation applications

Development of high-energy ion-beam irradiation techniques for radiation applications

Fabrication of Pt nanoparticle incorporated polymer nanowires by high energy ion and electron beam irradiation

Polyvinylpyrrolidone (PVP)–Pt nanoparticles (NPs) hybrid nanowires were fabricated by high energy ion beam irradiation to PVP thin films including H2PtCl6. Single ion hitting caused crosslinking reactions of PVP and reduction of Pt ions within local cylindrical area along an ion trajectory (ion track); therefore, the PVP nanowires including Pt NPs were formed and isolated on Si substrate after wet-development procedure. The number of Pt NPs was easily controlled by the mixed ratio of PVP and H2PtCl6. However, increasing the amount of H2PtCl6 led to decreasing the radial size and separation of the hybrid nanowires during the wet-development. Additional electron beam irradiation after ion beam improved separation of the nanowires and controlled radial sizes due to an increase in the density of crosslinking points inner the nanowires.

Integration of nano-scale components and supports in micromachined 3D silicon structures

We have developed a process for the three-dimensional (3D) machining of p-type silicon on a micro- and nano-scale using high-energy ion beam irradiation with one or more energies and fluences, followed by electrochemical anodization in hydrofluoric acid. We present a study of the dependence of our fabricated structures on irradiating ion energies, fluences, geometries and wafer resistivity. All these factors determine whether the micro- and nano-scale features are properly connected to the supports in the 3D silicon structures. If wrongly chosen, any of these factors may cause a breakage at the connection through localized over-etching. Under optimum irradiation and anodization conditions, free-standing patterned membranes can be fabricated with feature dimensions of 100 nm over areas of many square millimeters. This investigation is based on silicon structures but is relevant to any electro-assisted etching process for 3D fabrication, paving the way for achieving free-standing silicon photonics, mechanical resonators and micro-/nano-electromechanical systems.

Effect of swift heavy ion irradiation on copper/polymethyl methacrylate nanocomposites

In this study, composite films were prepared by incorporating the copper nanoparticles in the insulating polymethyl methacrylate (PMMA) polymer matrix by the solution casting method. These films were irradiated with 120 MeV Si10+ ions at a fluence of 1×1012 ions/cm2. The radiation-induced changes in dielectric, structural and thermal properties of PMMA/Cu nanocomposites were studied using the impedance/gain phase-analyzer, X-ray diffraction (XRD), Fourier transform infra red (FTIR) spectroscopy and differential scanning calorimeter (DSC) techniques. The dielectric properties were observed to enhance with increase in metal nanoparticles’ concentration as well as with irradiation fluence. This may be due to the metal/polymer bonding and conversion of the polymeric structure into the hydrogen-depleted carbon network. Crystallite size and crystallinity of pristine and irradiated samples are observed to increase after irradiation as revealed from the XRD analysis. High-energy ion beam irradiation of the semicrystalline polymer nanocomposite changes its T g behavior as observed from the DSC analysis which is corroborated with XRD results. This might be attributed to the rupture of some polymeric bonds, which is also corroborated with the FTIR spectroscopic analysis.

Modifications induced by O+8 ion beam to Lexan polycarbonate

High-energy ion beam irradiation of polymer is an effective technique to enhance the optical, structural and mechanical properties. Lexan polycarbonate films were irradiated by oxygen ions (energy 100 MeV, charge state O+8) with fluence varying from 3×1010 to 3×1012 ions/cm2. Ion beam-induced optical and structural modifications were studied by ultraviolet–visible (UV–Vis), X-ray diffractometer and Fourier Transform Infrared (FTIR) spectroscopy. It is observed that optical absorption increases with increasing fluencies. The absorption edge was also found to shift from the UV region to the visible region. Value of band gap shows a decreasing trend with increasing ion fluences. The correlation between the optical band gap and number of carbon atoms inside the carbon clusters embedded in the network of Lexan has been discussed. X-ray Diffraction (XRD) analyses show the significant change in crystallinity with fluences. FTIR spectra show that the intensity of the absorption bands of Lexan polymer decreases after ion beam irradiation.

Ion Beam Induced Modifications in Conducting Polymers

High energy ion beam induced modifications in polymeric materials is of great interest from the point of view of characterization and development of various structures and filters. Due to potential use of conducting polymers in light weight rechargeable batteries, magnetic storage media, optical computers, molecular electronics, biological and thermal sensors, the impact of swift heavy ions for the changes in electrical, structural and optical properties of polymers is desirable. The high energy ion beam irradiation of polymer is a sensitive technique to enhance its electrical conductivity, structural, mechanical and optical properties. Recent progress in the radiation effects of ion beams on conducting polymers are reviewed briefly. Our recent work on the radiation effects of ion beams on conductive polymers is described. The electrical, structural and optical properties of irradiated films were analyzed using V-I, X-Ray diffraction (XRD), scanning electron microscopy (SEM), UV-Visible spectroscopy and Fourier transform infrared spectroscopy methods.

An ion beam deceleration lens for ultra-low-energy ion bombardment of naked DNA

Study of low-energy ion bombardment effect on biological living materials is of significance. High-energy ion beam irradiation of biological materials such as organs and cells has no doubt biological effects. However, ion energy deposition in the ion-bombarded materials dominantly occurs in the low-energy range. To investigate effects from very-low-energy ion bombardment on biological materials, an ion beam deceleration lens is necessary for uniform ion energy lower than keV. A deceleration lens was designed and constructed based on study of the beam optics using the SIMION program. The lens consisted of six electrodes, able to focus and decelerate primary ion beam, with the last one being a long tube to obtain a parallel uniform exiting beam. The deceleration lens was installed to our 30-kV bioengineering-specialized ion beam line. The final decelerated-ion energy was measured using a simple electrostatic field to bend the beam to range from 10eV to 1keV controlled by the lens parameters and the primary beam condition. In a preliminary test, nitrogen ion beam at 60eV decelerated from a primary 20-keV beam bombarded naked plasmid DNA. The original DNA supercoiled form was found to change to relaxed and linear forms, indicating single or double strand breaks. The study demonstrated that the ion bombardment with energy as low as several-tens eV was possible to break DNA strands and thus potential to cause genetic modification of biological cells.

Fabrication of silicon nanowires by ion beam irradiation

ABSTRACTSilicon nanowires are becoming more important because of increasing requirements of the small scale and dense integration of devices. We report a top-down fabrication method for silicon nanowires using high-energy ion beam irradiation of bulk p-type silicon followed by electrochemical etching. Silicon nanowires with a diameter of ∼50nm have been fabricated and densely patterned nanowire arrays fabricated in different resistivity silicon wafers. With a suitable support structure, free standing silicon nanowires are also achieved. We investigate results depending on silicon wafer resistivity and location within the irradiated area.

Aging of porous silicon in physiological conditions: Cell adhesion modes on scaled 1D micropatterns

The surface properties of porous silicon (PSi) evolve rapidly in phosphate-buffered saline. X-ray photoelectron spectra indicate the formation of a Si-OH and C-O enriched surface, which becomes increasingly hydrophilic with aging time. Multiscale stripe micropatterns of Si and PSi have been fabricated by means of a high-energy ion-beam irradiation process. These micropatterns have been aged in physiological conditions and used to analyze human mesenchymal stem cell (hMSC) adhesion. The actin cytoskeleton of hMSCs orients following the uniaxial micropatterns. In the wider Si stripes, hMSCs are dominantly located on Si areas. However, for reduced Si widths, adhesion is avoided on PSi by a split assembly of the actin cytoskeleton on two parallel Si areas. These results confirm that nanostructured Si-OH/C-O-rich surfaces with hydrophilic character are specially adapted for the creation of cell adhesion surface contrasts.

Irradiation of Ethylene/Styrene Copolymers: Evidence of Sensitization of the Aromatic Moiety As Counterpart of the Radiation Protection Effect

Molecules containing aromatics systems are more stable in the presence of ionizing radiations than alkanes. In the same way, introducing aromatic rings into aliphatic compounds increases their stability. The protective effect is nonlocal and likely results from the transfer of energy and species from the aliphatic moiety to the aromatic one. For years, it was commonly assumed that the aromatic moiety, which is very radiation resistant, accommodates the extra energy remaining unaffected. The use of Fourier transform infrared spectroscopy, online with high energy ion beam irradiation of ethylene/styrene random copolymers, allows us to bring experimental evidence that the benzene rings are sensitized by transfer reactions and consequently that this effect is more important in polymers with low benzene ring molar content.