Low-energy Ion Beam Research Articles

Low-energy ion beam erosion of Si with simultaneous co-deposition of metallic surfactants: Experimental and simulated data

Ion beam erosion of Si under co-deposition circumstances supports the formation of surface patterns on the nano- and micrometer scale. To evaluate the effect of surfactant sputtering within a setup relevant for ultra precision surface finishing, this work is presented. We present data for samples prepared with Ar ion beam erosion, at low ion energy. Al, Cu, steel, Cr, Ni, Mo, Ti, Ta, Zn and Si were chosen as co-deposition material. Simultaneous irradiation of the co-deposition material and the Si samples were performed with a broad beam ion source. The structuring and pattern formation are discussed with SEM and AFM measurements. It was shown that the evolution of structures on the substrate is induced by the silicide-forming metals. This corresponds with a higher surface roughness. Whereas the non-silicide-forming metals did not show patterning, and accordingly, lower surface roughness. Measurements regarding the Si removal rate showed, that it depends on the co-deposition material. Supporting simulation data proposed that the effect of the co-deposition material on the Si removal is determined by the combination of sputtering and scattering properties of the co-deposition material. The ratio of scattered Ar ions to sputtered metal particles describes the effect on the removal change. For metals which tend to higher scattering, the removal is enhanced. This applies for most of the metals with higher atomic number. Whereas the metals with lower atomic number favor self-sputtering, which results in an decreased Si removal.

Defect-engineered MnO2 nanoparticles by low-energy ion beam irradiation for enhanced electrochemical energy storage applications

Defect-engineered MnO2 nanoparticles by low-energy ion beam irradiation for enhanced electrochemical energy storage applications

Review of Gas Dynamic RF-Only Funnel Technique for Low-Energy and High-Quality Ion Beam Extraction into a Vacuum.

This paper reviews the development and present status of a novel gas dynamic RF-only funnel technique for low-energy ion beam extraction into vacuum. This simple and original technique allows for the production of high-quality continuous and pulsed ion beams in a wide range of masses, which have a very small transverse and longitudinal emittance.

ON THE POSSIBILITY OF OBTAINING A BEAM OF HEAVY IONS IN THE FORM OF AN “OPEN UMBRELLA” WITH SUBSEQUENT DEPOSITION IN THE SEPARATOR MANIFOLD

The study of SNF reprocessing is impossible without obtaining and studying a multicomponent, low-energy and complex ion beam of an “umbrella” shape. The beam is obtained from a plasma flow created in a plasma source (PS) with a magnetic field of about 3 T, flowing along the axis into a weak magnetic field, at a level of 0.1…0.5 T. At the same time, its density decreases, and the entire energy of the plasma is converted into a jet directed along the axis. To randomize the particles of the jet plasma, a reflecting magnetic field is further placed on the axis. Without changing direction, the plasma flows in a hollow magnetic force tube around a solenoid with a reverse magnetic field. In this region, ions are drawn out in the radial direction towards the annular hole of the “pocket”. The target ions, M (230-277) follow umbrella trajectories and, being neutralized, are deposited in the “pocket” on the inner walls, the remaining ~ 3% are scattered and remain on the walls of the separator.

Ultralow-energy amorphization of contaminated silicon samples investigated by molecular dynamics.

Ion beam processes related to focused ion beam milling, surface patterning, and secondary ion mass spectrometry require precision and control. Quality and cleanliness of the sample are also crucial factors. Furthermore, several domains of nanotechnology and industry use nanoscaled samples that need to be controlled to an extreme level of precision. To reduce the irradiation-induced damage and to limit the interactions of the ions with the sample, low-energy ion beams are used because of their low implantation depths. Yet, low-energy ion beams come with a variety of challenges. When such low energies are used, the residual gas molecules in the instrument chamber can adsorb on the sample surface and impact the ion beam processes. In this paper we pursue an investigation on the effects of the most common contaminant, water, sputtered by ultralow-energy ion beams, ranging from 50 to 500 eV and covering the full range of incidence angles, using molecular dynamics simulations with the ReaxFF potential. We show that the expected sputtering yield trends are maintained down to the lowest sputtering yields. A region of interest with low damage is obtained for incidence angles around 60° to 75°. We also demonstrate that higher energies induce a larger removal of the water contaminant and, at the same time, induce an increased amorphization, which leads to a trade-off between sample cleanliness and damage.

Relative efficiency of radiophotoluminescent glass detectors in low energy ion beams

In heavy charged particle dosimetry, the luminescence efficiency strongly depends on linear energy transfer (LET) and characterization of the detectors' efficiency as a function of the particle LET is very important. Available literature data for the efficiency of radiophotoluminescent (RPL) glass detectors are scarce and especially for low energy range no data was found. In this study, detectors made of the most widely known RPL material (silver activated phosphate glass) were exposed to various low energy ion beams (1H, 7Li, and 12C). For every ion beam, the linear dose (fluence) response of the RPL glass detectors was confirmed for the investigated dose (fluence) range and the RPL efficiency relative to 60Co gamma rays was evaluated. The relative efficiency decreased as LET increased but not as a unique function of LET, where the relative efficiency (expressed for doses in RPL glass) decreased from 0.85 ± 0.06 for the 5 MeV 1H ion beam (LETw = 8.1 keV/μm) to 0.017 ± 0.001 for the 15 MeV 12C ion beam (LETw = 673.8 keV/μm). More experimental data are still needed but results obtained in this study may motivate the application and testing of microdosimetric models for RPL glass detectors.

Ultra-thin silver films grown by sputtering with a soft ion beam-treated intermediate layer

Silver thin films have wide-ranging applications in optical coatings and optoelectronic devices. However, their poor wettability to substrates such as glass often leads to an island growth mode, known as the Volmer–Weber mode. This study demonstrates a method that utilizes a low-energy ion beam (IB) treatment in conjunction with magnetron sputtering to fabricate continuous silver films as thin as 6 nm. A single-beam ion source generates low-energy soft ions to establish a nominal 1 nm seed silver layer, which significantly enhances the wettability of the subsequently deposited silver films, resulting in a continuous film of approximately 6 nm with a resistivity as low as 11.4 µΩ.cm. The transmittance spectra of these films were found to be comparable to simulated results, and the standard 100-grid tape test showed a marked improvement in adhesion to glass compared to silver films sputter-deposited without the IB treatment. High-resolution scanning electron microscopy images of the early growth stage indicate that the IB treatment promotes nucleation, while films without the IB treatment tend to form isolated islands. X-ray diffraction patterns indicate that the (111) crystallization is suppressed by the soft IB treatment, while growth of large crystals with (200) orientation is strengthened. This method is a promising approach for the fabrication of silver thin films with improved properties for use in optical coatings and optoelectronics.

RAPTOR: A new collinear laser ionization spectroscopy and laser-radiofrequency double-resonance experiment at the IGISOL facility

RAPTOR, Resonance ionization spectroscopy And Purification Traps for Optimized spectRoscopy, is a new collinear resonance ionization spectroscopy device constructed at the Ion Guide Isotope Separator On-Line (IGISOL) facility at the University of Jyväskylä, Finland. By operating at beam energies of under 10keV, the footprint of the experiment is reduced compared to more traditional collinear laser spectroscopy beamlines. In addition, RAPTOR is coupled to the JYFLTRAP Penning trap mass spectrometer, opening a window to laser-assisted nuclear-state selective purification, serving not only the mass measurement program, but also supporting post-trap decay spectroscopy experiments. Finally, the low-energy ion beams used for RAPTOR will enable high-precision laser-radiofrequency double-resonance experiments, resulting in spectroscopy with linewidths below 1 MHz. In this contribution, the technical layout of RAPTOR and a selection of ion-beam optical simulations for the device are presented, along with a discussion of the current status of the commissioning experiments.

Comparative wettability study of bulk and thin film of polytetrafluoroethylene after low energy ion irradiation

A comparative wettability study was carried out on bulk polytetrafluoroethylene (PTFE) and physical vapor deposited PTFE-like thin films using low-energy Argon ion beam irradiation. Both bulk PTFE and PTFE-like thin film surfaces were irradiated with the beam energy of 300 and 800 eV for 5 min. The angle of incidence of the ion beam was varied from 0° to 70° with respect to the surface normal. Ion beam irradiation produced the tilted sharp-edged microstructures on PTFE sheets elongated in the direction of the beam. After irradiation with 800 eV at 20°, the bulk PTFE sheet became superhydrophobic, the water contact angle increased from 105° to 157°, and again decreased to 132° after irradiation at 70° Whereas nanoripple-like patterns formed on PTFE-like thin films after ion beam irradiation. The maximum wavelength of such ripples was found to be 212 nm for an 800 eV irradiated surface at an angle of 50° Beyond this angle, a clear transition from ripple to facet-like patterns was observed. The contact angles of the irradiated thin film were found to be varying from 105° to 112° up to 30° irradiation and again decreased to 83° after irradiation at 70° PTFE thin film showed strong anisotropic wettability behavior with a variation of 12° of contact angle values perpendicular to the ion beam direction, and water droplets did not roll off from the surface like in the case of bulk PTFE. X-ray photoelectron spectroscopy revealed that the bulk PTFE had C−C, and CF2 bonding on the surface, whereas PTFE thin films formed additional CF, CF‒CFn, and CF3 bonding, which was not observed in the bulk PTFE. After irradiation, additional CF-CFn and CF3 bonding in bulk PTFE were observed. However, in the case of thin films, ion irradiation causes severe chain scission, crosslinking, and defluorination of the surface.

Ion beam engineering of implanted ZnO thin films for solar cell and lighting applications

Ion beam modification is a one-of-a-kind approach for engineering nanomaterials to change their chemical and physical properties. Ion beam engineering of metal oxide semiconductor nanoparticles has been performed to improve their optoelectronic properties considering their energy applications. Zinc Oxide (ZnO) is one of these developing wide band gap semiconductor materials with remarkable optoelectronic features that has piqued the scientific community's curiosity for a number of energy applications. Through the implantation of distinct ions at varied parameters, the low energy ion beam approach has been widely used to modify the structural, morphological, and optoelectronic features of ZnO thin film-based devices (i.e. dose, energy etc.). It offers a promising approach for controlling implantation-induced defects and associated emission in ZnO thin films. On the one hand, inert ion bombardment causes consistent surface patterning to form on ZnO, while on the other, it creates nucleation centers for the creation of nanostructures. Due to the significant radiation resistance of ZnO thin films, tuning of different properties can be studied with little to no irreparable damage to the crystal lattice. In this context, rare earth metal ion implantation in ZnO thin films represents an alternate option for study in the realm of luminescent-based applications, such as solar cells and lighting. This paper focuses on the utility of such ion implantation procedures in optoelectronic devices such as solid-state lighting and solar cells, using ZnO as a prototype material. A correlation amongst the ion implantation induced defects, conductivity and optical behaviour has also been highlighted for in-depth understanding of implantation related effects in ZnO thin film based optoelectronic devices for solar cells and lighting applications.

In-gas-jet laser spectroscopy with S[formula omitted]-LEB

The Super Separator Spectrometer-Low Energy Branch (S3-LEB) is a low-energy radioactive ion beam experiment under commissioning as part of the GANIL-SPIRAL2 facility. It will be used for the production and study of exotic nuclei by in-gas laser ionization and spectroscopy (IGLIS), decay spectroscopy, and mass spectrometry. We report recent results from the off-line commissioning of S3-LEB, including first laser spectroscopy measurements in both the gas cell and the supersonic gas jet, the determination of the transport efficiency of laser ions from the gas cell through the RFQ chain, and time-of-flight measurements with the multi-reflection time-of-flight mass spectrometer PILGRIM. The measurements were performed using erbium, introduced by evaporation from a heated filament in the gas environment. The reported laser spectroscopy results include a characterization of the pressure broadening in the gas cell, proof-of-principle isotope shift measurements, and hyperfine-structure measurements.

Towards ordered Si surface nanostructuring: role of an intermittent ion beam irradiation approach

The dynamical characteristics of surface nanopatterning using low-energy ion beams remains a central theme within ion beam sputtering. Most previous studies have focused on nanostructure evolution by bombarding surfaces using a continuous ion beam. Here, we study the effect of sputtering from an intermittent ion beam on nanopatterning of a Si surface, using a 900 eV or (mostly) 500 eV Ar+ ion beam at an incident angle of 67°, up to a total fluence of 10 × 1019 ions cm−2. Nanoripples are predominantly found on the irradiated surfaces, alongside a hierarchical triangular morphology at the lower energy condition. Ripple ordering is superior for intermediate values of the sputtering interval used in the intermittent sputtering approach. The area of the triangular structures also depends on the intermittent sputtering time intervals. At larger length scales than the ripple wavelength or the triangular structures, all surfaces display strong height fluctuations with a well-defined roughness exponent. Our results can be rationalized via known properties of the nonlinear regime of evolution for surfaces that become amorphous under irradiation and relax stress via ion-induced viscous flow, as borne out from numerical simulations of a continuum model previously proven to provide a significant description of the present class of experiments.

Defect-Engineered 3D Nanostructured MoS2 for Detection of Ammonia Gas at Room Temperature

Recent studies on nanostructured MoS2 show promising performance in the detection of reducing gases like ammonia (NH3). However, this material in the pristine form possesses limitations in terms of response, recovery, and repeatability over a long duration of time. Several attempts have been made to overcome these shortcomings by modifying it chemically to make a hybrid form or direct doping with other atoms. In this work, we demonstrate that suitable defect engineering of 3D nanostructured MoS2 induced by a low energy ion beam can lead to a significantly improved performance of sensing NH3 compared to the as-prepared one. Significant decreases in response and recovery times have been demonstrated at room temperature for the modified MoS2 compared to its pristine form, which shows its best response only at a higher temperature of about 200 °C. A 3D nanoflower-like structure of MoS2 was synthesized hydrothermally, which was coated on substrates, and then irradiated with 5 keV argon ions at different doses. While the ion beam-induced morphological modifications are observed via electron microscopic study, the surface defects are apparent in X-ray diffraction, Raman scattering, and X-ray spectroscopic studies. The ion beam-modified MoS2 shows a higher electrical conductivity and water-repelling nature compared to the pristine one, which are complementary properties for better sensing performance. While Monte Carlo-based 3D ion-solid interaction simulation was used to support the morphological modifications and defect developments after ion irradiation, the sensing mechanism and change in conductivity were successfully explained using density functional theory-based simulations.

Study of the characteristics of the system: Ion source-ion decelerator.

The features of the method for the formation of dense low-energy ion beams in the system consisting of ion source-ion decelerator are considered. According to this method, a wide ion beam is formed using an ion source with an ion energy of 500eV and higher, and then the ions are decelerated just before landing on the substrate surface by an electric field created in the ion decelerator. In the considered ion decelerator, the electric field that slows down the ions is created in a gas discharge in E × B fields due to the Hall effect. The decelerated electrode imitating the substrate is located in the field of action of a magnetic field with an induction of 0.45T. The ion decelerator is characterized as a Hall magnetohydrodynamic converter of the ion beam kinetic energy into electrical energy. The analysis of plasma processes in the converter has been carried out on the basis of the model of the ion-vacuum regime of a discharge in E × B fields for estimating the expected properties of the converter and their verification based on experimental results. In experiments, an ion source of the Kaufman type formed an argon ion beam with a density of 0.5-2 mA/cm2 and ion energy of 300-1500eV was used. The voltage-current characteristics of the converter are given. The ratio of electron and ion components of the current in the circuit of the decelerated electrode was determined when the beam space charge neutralizer in the form of a heated filament was switched on and off. Using a Langmuir probe and a thermionic probe, the distributions of the ion beam current density and the potential of the plasma surrounding the ion beam in the beam transport space has been studied. A significant influence of the potential of the decelerator electrode on the plasma potential in the region of ion beam transport is shown. The features of the discharge in a specific design of the ion decelerator for a deceleration degree of ions to an energy of 50-75eV are revealed.

Design and experimental validation of differential pumped vacuum system for HINEG windowless gas target

High Intensity Neutron Generator (HINEG) is a facility aiming for neutronics design validation, materials and components irradiation test, nuclear waste transmutation and nuclear technology applications, etc. A high-pressure windowless gas target system is adopted for HINEG to achieve a higher neutron yield. Therefore, a three-stage differential vacuum system has been developed to couple the pressure transition of 6 orders of magnitude to the 300 kV/50 mA high-intensity beam transport in a series of large-diameter pipes. A suitable pumping system has been developed to increases the target pressure which is used to generate D-T neutron yield of 2.1 × 1013 n/s. A windowless pressure transition from high gas pressure (1 × 103 Pa) in the gas target chamber to high vacuum (3 × 10−3 Pa) in the accelerator is reached. In this paper, a new differential pumped vacuum system is designed for HIENG. Innovatively, the newly designed differential vacuum system can not only meet the transport requirements of the high-current low-energy deuteron beam, but also couple the pressure transition of 6 orders of magnitude, which can solve the contradiction of the large-diameter pipe required for high-intensity beam transport and the small diameter pipe needed for the high-pressure difference.The experimental validation and design optimization of differential pumped vacuum system is introduced. The experiment results indicate the validity of the theoretical calculation. Compared to molecular pumps, roots pumps might be more suitable for windowless differential vacuum system coupled to large-diameter apertures and pipes. The design could be used for reference in other windowless gas target systems coupled to accelerator with high-current low-energy ion beam.

Electron Capture by Proton Beam in Collisions with Water Vapor

In low energy ion-molecule collisions, electron capture is one of the most important channels. A new experimental setup was developed to study the electron capture process using low-energy ion beams extracted from an electron cyclotron resonance (ECR) plasma-based ion accelerator. Experiments were carried out with the proton beam colliding with water vapor in the energy range of 70–300 keV. Capture events were detected using a position-sensitive detection system comprising micro channel plates (MCPs) and a delay line detector (DLD). These e-capture events can be a result of pure capture reactions as well as transfer ionization. The capture cross section was found to decrease sharply with the beam energy and agreed well with previous measurements. The setup was also used to detect the events that gave rise to the single and multiple e-capture (integrated over all recoil-ion charge states) of C4+ ions. The capture cross-sections for one, two, three, and four electrons were measured for 100 keV C4+ ions. The ratio of multielectron capture yield to that for single e-capture decreased with the number of captured electrons.

Ion implantation as an approach for tuning of electronic structure, optical, morphological and electrical transport properties of sputtered molybdenum disulfide thin films

Molybdenum disulfide (MoS2) thin films have acquired increasing consideration in the field of low-dimensional electronics as device-active layers and also in hydrogen evolution reaction (HER) as catalysts in distinct electrochemical processes. Thus, for distinct applications, extensive scalable fabrication techniques with tunable MoS2 properties are significant. To possess tunable efficiency of various device applications at nanoscale it is significant to acquire control over the density of defects, although attaining with direct growth techniques remains a significant issue. Here we illustrate a robust and effective approach to tailor the density of defects using Au ion implantation. In the present work, we illustrate the scalable technique i.e. magnetron sputtering for the fabrication of MoS2 thin films, subsequently, ion implantation with 80 keV Au ions at a distinct fluence of 1 × 1015 and 5 × 1015 ions/cm2 was carried out. Striking deviations were remarked in nanostructure and depth distributions of the resultant thin films of MoS2. Pristine and ion implanted thin films were characterized to comprehend the morphological, electrical transport and electronic structure properties. The surface micrographs’ results revealed noteworthy alterations in the thin films’ surface roughness. The modifications induced by low energy Au ion implantation in core-level electronic structure and atomic bonding was probed by XPS and Raman spectroscopy technique. The electrical properties of these films were studied to demonstrate the scattering and conduction mechanisms. The present work contributes to the significant passage of tailoring 2D MoS2 thin films’ electronic structure, optical and morphological properties through doping and defects formation by low energy ion beam implantation to extend their practical device applications.

Design and simulation of a low-energy single ion irradiation system for micro/nano-biosample investigation

A low-energy single ion irradiation system is developed in its initiation in Thailand to follow one of the trends in novel ion beam technology exploitation. Single ion irradiation of materials is a highly technological development of ion beam technology. The developed single ion irradiation systems worldwide are primarily in the MeV-energy range and for single cell studies, and recently the trend has been extended to the low-energy range (< 100 keV) but focused on microelectronic applications. Based on our previous research on low-energy ion beam irradiation of biological cells and DNA, we design and simulate a low-energy single ion implantation system, aiming at eventual construction of such a novel ion beam apparatus for applications to the biological studies. In the system, the ion energy is decreased to orders < 1 keV by the existing deceleration lens, then the low-energy ion beam passes through µm slits, and finally, low-energy single ions are obtained by beam scanning with appropriate frequencies from scanner plates and detected by a single ion detection device. Conceptual design, calculation and simulation of this single ion system are presented.

Transverse emittance measurement in 2D and 4D performed on a Low Energy Beam Transport line: benchmarking and data analysis

2D and 4D transverse phase-space of a low-energy ion-beam is measured with two of the most common emittance scanners. The article covers the description of the installation, the setup, the settings, the experiment and the benchmark of the two emittance meters. We compare the results from three series of measurements and present the advantages and drawbacks of the two systems. Coupling between phase-space planes, correlations and mitigation of deleterious effects are discussed. The influence of background noise and aberrations of trace-space figures on emittance measurements and RMS calculations is highlighted, especially for low density beams and halos. A new data analysis method using noise reduction, filtering, and reconstruction of the emittance figure is described. Finally, some basic concepts of phase-space theory and application to beam transport are recalled.

Tuning optical and optoelectronic properties of polycrystalline lead selenide via low-energy assisted ion beam

Tuning the optical and optoelectronic properties of materials is attractive for solar energy and infrared sensing applications. Here, we proposed an ion beam co-growth preparation method that can continuously tune the optical band gap and absorption and thus optoelectronic properties of lead selenide. The optical band gap of the material can be effectively tuned by ion energy and beam current, varying continuously from 0.79 to 1.03 eV. The tuning mechanism of ion beam on optical and optoelectronic properties was revealed by orthogonal range analysis. The results of range analysis on optical properties show that ion energy and beam current play the key role in adjusting the optical band gap and absorptivity. Ion beam regulation also reduces the Urbach energy of the material, suggesting low thermal disorder and structural defects of the resulting material. The photoresponsivity and specific detectivity of thin film devices can also be effectively tuned by the ion energy and beam current. The material is sensitive to mid-infrared radiation, and the preliminary photoresponsivity is up to 0.61 A/W at 3 µm, which is better than those of traditional thermal diffusion in oxygen atmosphere.