keV Oxygen Ions Research Articles

Low energy ion irradiation effects in MgO: Optical property study

Irradiation of MgO pellets with ion beams results in the formation of vacancies and their aggregates. The irradiated MgO pellets are characterized by optical absorption and photoluminescence studies. 100 keV helium ion irradiation of MgO pellets results in the formation of F or F+ defects, F22+ defects, and F2 type defects. When irradiated with 100 keV oxygen ion beam, surface oxygen vacancies and F22+ defects are formed in the MgO lattice. Various PL emission peaks occur in the irradiated sample and in particular, emissions at 3.1 and 2.79 eV are found to be related to oxygen vacancies created by ion irradiation in the MgO target. The surface morphology of the irradiated samples is investigated with scanning electron microscopy.

K X-ray Emission for Slow Oxygen Ions Approaching a Copper Metal Surface

We report on the K X-ray emission for 9–140 keV oxygen ions with initial charge states from 3 to 7 approaching a copper surface. The peak center of the measured X-ray spectrum slightly shifts towards higher energies with the increasing of the initial charge state of the incident ions. For the collisions of oxygen ions with no K-vacancies (q = 3–6), the X-ray yield per incident ion increases gradually with the projectile’s kinetic energy, while for the O7+ ions (with a K-vacancy) it is nearly independent of the energy. The K-shell ionization cross-sections for the oxygen ions with no K-vacancies obtained from the experiments are well consistent with the calculations of the binary encounter approximation model when the collision energy is larger than 30 keV, whereas they are several times larger than the theoretical values at collision energies of less than 30 keV.

Loss of Energetic Ions Comprising the Ring Current Populations of Jupiter's Middle and Inner Magnetosphere

AbstractThe low‐altitude, polar orbit of the Juno mission allows the Jupiter Energetic Particle Detector Instrument to view into, and resolve, the loss cone of energetic ions comprising the low‐altitude extension of Jupiter's ring current ions. For regions mapping from just inside Ganymede's orbit to well beyond Ganymede's orbit, energetic ions (>50 keV H+ and >130 keV Oxygen and Sulfur ions) are strongly scattered into the loss cone and lost to the magnetosphere at the “strong diffusion limit” at essentially all times. We conclude, by arguing against magnetic curvature scattering, that the cause is waves, perhaps associated with Alfvénic variations previously documented in this equatorial region. Scattering is generally weak or nonexistent near the orbits of the moons Europa and Io, except for the regions just downstream of the corotating plasmas. For Io, we sometimes observe moderate, but not saturated, scattering within roughly 60° downstream. Significantly, scattering is weak or nonexistent just upstream of Io's position, an asymmetry echoed in some previous wave observations. A preliminary accounting of the total (longitude‐averaged) scattering losses near Io's orbit yields loss rates of order 4%–5% of the strong diffusion limit for H+ and 5%–7% for heavy ions (O + S). We conclude that near Io's orbit, charge exchange losses likely dominate over scattering losses for heavy ions and for the lower energy H+ ions (roughly <200 keV).

Creation of functional nanostructures under ion irradiation

The paper describes a method developed in National Research Centre "Kurchatov Institute" for creating different functional nanostructures using ion beam irradiation. As an example, the formation of an integrated resistive elements in a low-temperature NbN superconductor nanowire is demonstrated. The possibility of producing an insulating layer of aluminum oxide with a thickness of 15 nm on the aluminum surface at room temperature under 0.2 keV oxygen ions irradiation was shown. Keywords: Ion irradiation, NbN thin superconducting films, integrated cryogenic resistors, creation of dielectric layers under irradiation.

Evidence for Nonadiabatic Oxygen Energization in the Near‐Earth Magnetotail From MMS

AbstractWe present Magnetospheric Multiscale (MMS) mission observations of substorm‐related ion injections at magnetotail positions between ∼7.5 RE and 8.5 RE. Energization of supra‐thermal ions (50 keV–1,000 keV) is strongly species dependent, with oxygen reaching significantly higher peak energies than protons. Using a previously established correlation technique, we confirm that the highest energy (>400 keV) oxygen ions are multiply charged of solar wind origin, enabling them to reach high energies in rough proportion to their charge states. Significantly, we conclude that oxygen ions between 130 keV and 330 keV are singly charged, and that they sometimes achieve higher energizations relative to protons, that is, higher than expected based on their charge states. We conclude that nonadiabatic processes can boost the energies of the oxygen ions. The technique does not depend on “before injection” and “after injection” spectral comparisons, and therefore likely represents the most definitive test yet of nonadiabaticity.

Создание функциональных наноструктур под действием ионного облучения

The paper describes a method developed in National Research Centre “Kurchatov Institute” for creating different functional nanostructures using ion beam irradiation. As an example, the formation of an integrated resistive elements in a low-temperature NbN superconductor nanowire is demonstrated. The possibility of producing an insulating layer of aluminum oxide with a thickness of 15 nm on the aluminum surface at room temperature under 0.2 keV oxygen ions irradiation was shown.

Processing of 72-K water-rich ices by keV and MeV oxygen ions: implications for the Saturnian moon Enceladus

ABSTRACT The processing of H2O:CO2:CH4 (10:1:1) and H2O:CO2:CH4:NH3 (10:1:1:1) ices at 72 K by oxygen ions was studied in an attempt to simulate the physicochemical effects induced by energetic ions on the surface of Enceladus (or similar cold surfaces in the outer Solar System). The experiments were carried out at the Grand Accélérateur National d’Ions Lourds (GANIL) in Caen/France. The samples were irradiated with 15.7-MeV O5+ at the IRRadiation SUD (IRRSUD) beamline and with 108-keV O6+ at the Accélérateurs pour les Recherches avec les Ions de Basses Energies (ARIBE) beamline. The frozen samples were monitored by Fourier Transform Infrared Spectroscopy (FTIR) spectroscopy (4000–650 cm−1, 2.5–15.4 μm, at 1 cm−1 resolution). The identified molecular species formed during irradiation were CO, OCN−, CH3OH, HCN, CN−, H2CO3, HNCO, HCO and CO3. The effective formation cross-sections for the synthesis of new species and the effective molecular destruction cross-sections of the parent species in the experiments with MeV ions were found to be of the order of 10−14–10−13 cm2. For the keV ion experiments, these values were of the order of 10−16–10−15 cm2. The fluence at which the sample reaches chemical equilibrium and the molecular abundances in this region (equilibrium branching ratios) were estimated. These experiments suggest that the chemical inventory on the surface of Enceladus can be influenced by the incidence of charged particles on to the moon’s surface.

Кремниевые светодиоды с люминесценцией (113) дефектов

Silicon light-emitting diodes with luminescence associated with (113) defects have been fabricated using implantation of 350 keV oxygen ions at the dose of 3.7∙1014 cm-2 and subsequent annealing at 700ᵒC for 1 h in a chlorine-containing atmosphere. Electroluminescence was studied in wide ranges of temperature and an excitation power. The line associated with (113) defects dominates in all the spectra. The temperature dependence of the line intensity depends on the excitation power in the range of low temperatures: an increase of the intensity with activation energy of 25 meV is observed at low current density and, with the increasing current density, a rise of the intensity is not observed. At higher temperatures, a decrease of the intensity with activation energy of 59 meV occurs regardless of a current density. With the increasing temperature, the peak of the line shifts by the same energy as the forbidden gap width, while the half width of the line grows linearly.

Ion Heating by Electromagnetic Ion Cyclotron Waves and Magnetosonic Waves in the Earth's Inner Magnetosphere

AbstractElectromagnetic ion cyclotron (EMIC) waves and magnetosonic waves are commonly observed in the Earth's magnetosphere associated with enhanced ring current activity. Using wave and ion measurements from the Van Allen Probes, we identify clear correlations between the hydrogen‐ and helium‐band EMIC waves with the enhancement of trapped helium and oxygen ion fluxes, respectively. We calculate the diffusion coefficients of different ion species using quasi‐linear theory to understand the effects of resonant scattering by EMIC waves. Our calculations indicate that EMIC waves can cause pitch angle scattering loss of several keV to hundreds of keV ions, and heating of tens of eV to several keV helium and oxygen ions by hydrogen‐ and helium‐band EMIC waves, respectively. Moreover, we found that magnetosonic waves can cause the resonant heating of thermal protons. Our study indicates the importance of energy transfer from the EMIC and magnetosonic waves to ions with different species at thermal energies.

Engineering strain and conductivity of MoO3 by ion implantation

α-MoO3 lamellar crystals are implanted with 170 keV oxygen ions at room temperature and with fluences between 1 × 1012 cm−2 and 1 × 1017 cm−2, in order to modify the electrical and structural properties of the crystals. A controllable and significant increase of the electrical conductivity, over several orders of magnitude, is observed after implantation at high fluences. Based on high resolution X-ray diffraction (HRXRD) and micro-Raman spectroscopy measurements, this effect is attributed to the formation of donor-type defect complexes and new phases more conductive than the α-MoO3 orthorhombic phase. A significant expansion of the b lattice parameter, increasing with fluence, is observed as a response to the defects created by implantation. Strain build-up occurs in several steps and in distinct depth regions within the implanted layer. Contrary to the typical values reported for other implanted oxide materials, an unusually high maximum perpendicular deformation of ∼3% is verified.

Hydrophobicity Recovery of Polydimethylsiloxane Treated with Oxygen Plasma and Ion Implantation

One of a few disadvantage properties of polymethylsiloxane (PDMS) is its hydrophobicity which can hinder its fluidic applications. Oxygen plasma treatment on PDMS surfaces is a conventional method in rendering them hydrophilic, however hydrophobicity returns within days after treatment. This study proposes oxygen ion implantation at the micrometer scale inside PDMS structures to ensure lasting hydrophilicity. The PDMS slabs were treated with 20 keV oxygen ion with 1 × 1015 ions/cm2 fluence and inductively coupled oxygen plasma generated at a power of 28 W and frequency of 13.56 MHz. The chemical composition of the treated PDMS surface was monitored by X-ray photoelectron spectroscopy (XPS) and it was found that oxygen concentration remain high after three days of oxygen plasma treatment on the PDMS. Although the surface oxygen concentration in the oxygen ion implanted PDMS was not as high as that oxygen plasma treated PDMS, the oxygen concentration level was remained higher than that of the untreated PDMS surface for four weeks.

Nanocrystalline SnO2 formation by oxygen ion implantation in tin thin films

Metallic tin thin films of thickness 100 nm are deposited on fused silica substrates by thermal evaporation technique. These films are implanted with 45 keV oxygen ions at fluences ranging from 5 × 1015 to 5 × 1016 ions cm−2. The energy of the oxygen ions is calculated using SRIM in order to form embedded phases at the film-substrate interface. Post-implantation, films are annealed using a tube furnace for nanocrystalline tin oxide formation. These films are characterized using x-ray diffraction, Raman spectroscopy, UV–vis spectroscopy and photoluminescence spectroscopy. XRD and Raman spectroscopy studies reveal the formation of single rutile phase of SnO2. The size of the nanocrystallites formed decreases with an increase in the ion fluence. The nanocrystalline SnO2 formation is also confirmed by UV–vis and photoluminescence spectroscopy.

Comparative study of 150 keV Ar+ and O+ ion implantation induced structural modification on electrical conductivity in Bakelite polymer

A comparative study of 150 keV argon (Ar+) and oxygen (O+) ion implantation induced microstructural modifications in Bakelite Resistive Plate Chamber (RPC) detector material at different implantation fluences have been studied using Positron Annihilation Lifetime Spectroscopy (PALS). Positron lifetime parameters viz., o-Ps lifetime (τ3) and its intensity (I3) upon lower implantation fluences can be interpreted as the cross-linking and the increased local temperature induced diffusion followed by trapping of ions in the interior polymer voids. The increased o-Ps lifetime (τ3) at higher O+ ion implantation fluences indicates chain scission owing to the oxidation and track formation. This is also justified by the X-Ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) results. The modification in the microstructure and electrical conductivity of Bakelite materials are more upon implantation of O+ ions than Ar+ ions of same energy and fluences. The reduced electrical conductivity of Bakelite polymer material upon ion implantation of both the ions is correlated to the conducting pathways and cross-links in the polymer matrix. The appropriate energy and fluence of implanting ions might reduce the leakage current and hence improve the performance of Bakelite RPC detectors.

Energetic particle loss through the magnetopause: A combined global MHD and test‐particle study

AbstractWe study the spatiotemporal characteristics of energetic particle losses from the magnetosphere using test‐particle trajectories in electromagnetic fields from a global magnetosphere magnetohydrodynamic (MHD) simulation. We use a dynamically evolving distribution of high‐resolution electromagnetic fields from the Lyon‐Fedder‐Mobarry global MHD model and trace large ensembles of 100 keV hydrogen and oxygen ions as well as electrons from a near‐Earth plasma sheet location through their escape from the magnetosphere. In agreement with recent MMS observations, we demonstrate that both ions and electrons have access to and escape throughout the dayside magnetopause, including magnetically drift‐shadowed regions. Also, in agreement with MMS observations, the depth of penetration and persistence of particles in the magnetosheath has a clear mass dependence, heavier particles penetrating further and lingering longer. We demonstrate both magnetic local time and latitude dependence of particles losses as manifested by their crossings of the open‐closed boundary and relate them to the complex field topology. Finally, we establish a significant role of Kelvin‐Helmholtz instability in facilitating particle losses at the magnetopause flanks.

PL and ESR study for defect centers in 4H-SiC induced by oxygen ion implantation

Radiation damage in 4H-SiC samples implanted by 70 keV oxygen ion beams was studied using photoluminescence and electron spin resonance techniques. ESR peak of g = 2.0053 and two zero-phonon lines were observed with the implanted samples. Combined with theoretical calculations, we found that the main defect in the implanted 4H-SiC samples was oxygen-vacancy complex. The calculated defect formation energies showed that the oxygen-vacancy centers were stable in n-type 4H-SiC. Moreover, the \( {\text{V}}_{\text{Si}} {\text{O}}_{\text{C}}^{ 0} \) and \( {\text{V}}_{\text{Si}} {\text{O}}_{\text{C}}^{ - 1} \) centers were optically addressable. The results suggest promising spin coherence properties for quantum information science.

IRRADIATION AND SILVER DEPOSITION FOR IMPROVEMENT OF NASOPHARYNGEAL AIRWAY MEDICAL DEVICE PROPERTIES

The thermal and mechanical properties of nasopharyngeal airway (NPA) samples are improved by irradiation using 4[Formula: see text]keV oxygen and nitrogen ion beams with different ion fluences varying from [Formula: see text] ions/cm2to [Formula: see text] ions/cm2. The thermal stability of NPA medical device increases with increasing nitrogen and oxygen ion fluences. The tensile strength increased from 48[Formula: see text]MPa for unirradiated sample to 74[Formula: see text]MPa for samples irradiated with nitrogen and to 58[Formula: see text]MPa for samples irradiated with oxygen ion, while the elongation at break decreases for irradiated samples. Silver thin films are deposited on NPA medical device samples using 4[Formula: see text]keV argon ion beam. The XRD spectra demonstrated that silver nanoparticles are deposited on NPA medical device substrate. The effects of Ag thin film on gram-positive and gram-negative bacteria are studied.

Influence of oxygen ion implantation on the free volume parameters and electrical conductivity of a polymer‐based bakelite RPC detector material

ABSTRACTWe have investigated the effect of ion implantation on structural modification and the electrical conductivity of Bakelite‐resistive plate chamber (RPC) detector material used in high energy physics experiments. Samples of Bakelite polymer were exposed to 100 keV and 150 keV oxygen ions in the fluence of 1012 to 1015 ions cm−2. Ion implantation induced microstructural changes have been studied using positron annihilation lifetime spectroscopy, X‐ray diffraction and Fourier transform infrared techniques. Positron lifetime parameters viz., o‐Ps lifetime and its intensity showed formation of radicals, secondary ions due to the creation of interior tracks by high‐energy ions followed by chain scission at lower fluence of 100 keV implantation. The decreased free volume size at 150 keV ion implantation is an indication of crosslinking and filling up of interior tracks by the implanted ions. Variation of ac conductivity with frequency obeys Jonscher power law at 100 keV and the conduction mechanism is explained by barrier hopping model. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44962.

Investigation on modification of ion implanted natural corundum by UV–Vis-NIR spectroscopy

Abstract Natural corundum, a crystalline form of aluminium oxide (Al 2 O 3 ) with impure elements, is an allochromatic mineral whose color varies based on the presence of impurities in the composition. Ion implantation technology can be utilized for enhancing the optical properties of corundum by selecting the implanted ion type leading to modification of the composition and defects. As for the appearance of corundum depending on many factors including brilliance, color, fire (light dispersion), and luster, this research attempted to find out an alternative method for improving the optical appearance and color enhancement of corundum by using ion implantation. Ion beam treatments with 70 keV nitrogen and argon ions and 23 keV oxygen ion at fluence of 10 17 ions/cm 2 were applied to ruby and sapphire from Thailand, Myanmar, Cambodia, Sri Lanka, Africa, and USA. Additionally, ion beam analysis techniques, i.e., particle-induced X-ray emission (PIXE), together with conventional gemological observations such as optical microscope and UltraViolet-Visible and Near Infrared (UV–Vis-NIR) spectroscopy were applied to understand the phenomena observed. The results revealed the possibility of color changing by ion beams resulting from variation in the ionic stage of trace elements as seen from UV–Vis-NIR absorption spectra. The advantages of ion implantation appear to be new and sustainable for improving corundum properties.

Anomalous Positive Ion Formation in Negative Ion Collisions with HOPG

Charge transfer on graphite, a typical substrate and one of the fusion first wall materials, is of great importance in the plasma–wall interaction, thin-film growth, and surface catalysis. We present an experimental study of 8.5–22.5 keV energy carbon, oxygen, and fluorine negative ions scattering from a highly oriented pyrolytic graphite (HOPG) surface at a scattering angle of 8°. It is found that the positive ion fraction decreases monotonically with the increase of both incident velocity and angle. In particular, these dependences are very different from those presented in previous studies. A molecular dynamics simulation reveals that, around the critical condition for planar surface channeling, a number of projectiles may penetrate into the subsurface and become energetic atoms when they emerge from the surface. Hence, an exponential scaling related to the penetration probability has been proposed to well describe the velocity and angle dependences of positive ion fractions.

Storm time impulsive enhancements of energetic oxygen due to adiabatic acceleration of preexisting warm oxygen in the inner magnetosphere

AbstractWe examine enhancements of energetic (>50 keV) oxygen ions observed by the Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) instrument on board the Van Allen Probes spacecraft in the inner magnetosphere (L ~ 6) at 22–23 h magnetic local time (MLT) during an injection event of the 6 June 2013 storm. Simultaneous observations by two Van Allen Probes spacecraft located close together (~0.5 RE) indicate that particle injections occurred in the premidnight sector (< ~24 h MLT). We also examine the evolution of the proton and oxygen energy spectra at L ~ 6 during the injection event. The spectral slope did not significantly change during the storm. The oxygen phase space density (PSD) was shifted toward higher PSD in a wide range of the first adiabatic invariant. The spectral evolution manifests the characteristics of adiabatic acceleration and density increase of oxygen ions. Warm (0.1–10 keV) oxygen measured by the Helium, Oxygen, Proton, and Electron (HOPE) instrument was enhanced prior to the storm mostly in magnetic field‐aligned directions. The most reasonable scenario of this event is that warm oxygen ions that preexisted in the inner magnetosphere were picked up and adiabatically transported and accelerated by spatially localized, temporarily impulsive electric fields.