High-energy Oxygen Ions Research Articles

Thickness dependent structural and electrical properties of pulsed laser deposited Y0.95Ca0.05MnO3 thin films and the effect of high energy oxygen ion irradiation

Thickness dependent structural and electrical properties of pulsed laser deposited Y0.95Ca0.05MnO3 thin films and the effect of high energy oxygen ion irradiation

Exploring negative ion behaviors and their influence on properties of DC magnetron sputtered ITO films under varied power and pressure conditions

Abstract We deposited indium-tin-oxide (ITO) films on silicon and quartz substrates by magnetron sputtering technology in pure argon. Using electrostatic quadrupole plasma diagnostic technology, we investigate the effects of discharge power and discharge pressure on the ion flux and energy distribution function of incidence on the substrate surface, with special attention to the production of high-energy negative oxygen ions, and elucidate the mechanism behind its production. At the same time, the structure and properties of ITO films are systematically characterized to understand the potential effects of high energy oxygen ions on the growth of ITO films. Combining with the kinetic property analysis of sputtering damage mechanism of transparent conductive oxide (TCO) thin films, this study provides valuable physical understanding of optimization of TCO thin film deposition process.

Paticularities of radiation defect formation in ceramic barium cerate

The results of the investigations are presented on the effect of irradiation with electrons, ions of inert gases (Ne, Ar, Kr) and oxygen on the structure and properties of Nd-doped barium cerate by the methods of X-ray diffraction analysis, scanning electron and atomic force microscopy, thermal desorption spectroscopy. It is shown that the low-energy irradiation with Ne and Ar ions stimulates the blistering processes on the surface, whereas the high energy ion irradiation by Ne, Ar, Kr ions the cerate surface undergoes the following stages of the spherulite growth - nucleation, growth (view of cauliflower), formation of spherulitic crust, correspondingly. The similar structures were not observed in the case of irradiation with high-energy oxygen ions. It is noticed that the irradiation of cerates with electrons leads to the formation of nano-sized acicular structures on the surface. The radiation of lowenergy ions of inert gases led to the conversion of most of the neodymium into a tetravalent state, as has been shown, accompanied by an increase in oxygen release and a decrease in water compared to non-irradiated cerate, as well as the independence of the amount of gases from the type of ions. Based on the data on thermal desorption of water and oxygen molecules from the irradiated barium cerate it was assumed that the irradiation stimulates the oxidation to Nd4+.

Flux of High-Energy Positive Oxygen Ions from Plasma to a Substrate in a Pulsed Magnetron Discharge with a Hot Target

Flux of High-Energy Positive Oxygen Ions from Plasma to a Substrate in a Pulsed Magnetron Discharge with a Hot Target

Flow of high-energy positive oxygen ions from plasma onto the substrate in a pulsed magnetron discharge with a hot target.

A group of high-energy positive O^+ ions was detected in a plasma flowhigh-current pulsed magnetron discharge with a hot target in an Ar/O_2 gas mixture. The mechanism for the formation of accelerated O^+ ions may be the conversion of accelerated ones in the cathode layer of negative ions O^– → O^+ in the processes of charge exchange or ionization by electron impact.

Ultra-low stress high reflective film by dual-ion-beam sputtering deposition

The correlation between the process parameters of auxiliary ion source and the SiO2 film stress was systematically studied using dual-ion-sputtering deposition. Spectrophotometer and ellipsometer were used to measure the SiO2 film’s transmittance spectrum and reflection ellipsometry. The refractive index and thickness of SiO2 film were obtained by total spectrum inversion calculation. The laser interferometer measures the substrate surface shape to obtain film stress. The experimental result shows that film stress is related to sputtering energy during deposition, high-energy oxygen ion assisted deposition can significantly reduce it and the assisted ion beam voltage plays an important role in controlling it by data normalization analysis. Ultra-low stress high reflective film was prepared by dual-ion-beam sputtering deposition, where stress was 70% lower than traditional film. At the same time, this film can ensure sufficiently high optical quality to keep it reliable and stable in high-precision laser systems.

Deuterium retention in MeV ion-irradiated beryllium

Beryllium , as the material of choice for the ITER first wall, will be subject to high energy neutrons during the operation of the fusion device. Such irradiation will create displacement damage in the crystal lattice , which is known to influence hydrogen isotope retention, e.g. in iron and tungsten . In our study, we irradiated beryllium samples with high-energy oxygen ions up to various dpa levels (0.01 dpa, 0.1 dpa, and 1 dpa) and subsequently exposed the samples to deuterium plasma at 370 K and 573 K. The amount of retained deuterium was measured by thermal desorption spectroscopy and nuclear reaction analysis and was found to decrease by about 18% in the samples damaged up to 0.1 dpa compared to the undamaged ones. Further damaging up to 1 dpa did not show any additional effects on deuterium retention. Transmission electron microscopy was used to check for the existence of bubbles after plasma exposure.

Understanding the role of energetic particles during the growth of TiO2 thin films by reactive magnetron sputtering through multi-scale Monte Carlo simulations and experimental deposition

In this paper, a previously established 3D multi-scale simulation chain of plasma deposition process, based on a combination of a direct simulation Monte Carlo (gas phase) algorithm and a kinetic Monte Carlo (kMC) (film growth) code, is improved by the addition of a particle-in-cell Monte Carlo collision algorithm in order to take into account and clarify the role of charged particles. The kinetic Monte Carlo code is also extended with a binary collision approximation algorithm to handle charged particles. This modelling strategy is successfully applied to the growth of TiO2 thin films by means of reactive magnetron sputtering. In order to highlight the effects of negative oxygen ions, two substrate locations are selected: one in the median plane of the targets and another one off the median plane. The model efficiently predicts the densities and fluxes of both charged and neutral particles towards the substrate. Typical results such as particle densities, the discharge current density and ion flux onto the target, and the various substrate locations are calculated. The angular distribution and energy distribution of all involved particles are sampled at these very same substrate locations and the nanoscale modelling (NASCAM) code, implementing the kMC approach, uses these results to explain the morphology of the experimentally deposited coatings. The changes throughout the transition from metallic deposition to stoichiometric TiO2 of the columnar structure of the deposited films is explained by the suppression of the atom diffusion on the growing film due to Ti oxidation. Moreover, the high-energy negative atomic oxygen ions originating from the targets are identified as the origin of the abnormally low inclination of the columnar structure experimentally observed for the oxide mode coatings. Measurements of the normalized energy flux (energy per deposited atom) are experimentally investigated to support and highlight the important role of energetic particles during film growth.

Прискорення ресурсних випробувань полімерів космічних апаратів на стійкість до тривалої дії атомарного кисню в іоносфері Землі

The procedure of accelerated resource tests of spacecraft polymers for their resistance to the long-term influence of atomic oxygen (AO) in the Earth's ionosphere at altitudes from 200 to 700 km has been developed. The procedure involves irradiation of polymers with high-energy ions of atomic oxygen and the use of a kapton-H polyimide as reference material. The condition of equivalence of the " atomic oxygen - polymer" interaction in the ionosphere and on the laboratory set is the equality of tested material mass loss. The basis for substantiating the procedure of accelerated tests is the result: when irradiating the kapton-H polymer with high-energy atomic oxygen ions in the energy range from 30 to 80 eV, the degradation of polyimide is determined by the process of chemical etching of the material. To substantiate the procedure of accelerating resource tests of polymeric structural materials of spacecraft for resistance to long-term action of atomic oxygen flows, the dependences of mass loss and volumetric mass loss factor (reactivity) of kapton-H polyimide and Teflon FEP-100A on fluence and energy of the atomic oxygen ions have been obtained. It is shown that when irradiating kapton-H polyimide with atomic oxygen ions with the energy of 30 to 80 eV, the material mass loss due to chemical etching is about an order of magnitude greater than the mass loss due to kinetic sputtering. When the kapton-H polymer is irradiated with high-energy atomic oxygen ions, the coefficient of acceleration of the resource tests and the fluence of atomic oxygen are about two orders of magnitude greater than the coefficient of acceleration obtained using atomic oxygen ions with an energy of 5 eV.

High-Energy (>10 MeV) Oxygen and Sulfur Ions Observed at Jupiter From Pulse Width Measurements of the JEDI Sensors.

The Jovian polar regions produce X‐rays that are characteristic of very energetic oxygen and sulfur that become highly charged on precipitating into Jupiter's upper atmosphere. Juno has traversed the polar regions above where these energetic ions are expected to be precipitating revealing a complex composition and energy structure. Energetic ions are likely to drive the characteristic X‐rays observed at Jupiter (Haggerty et al., 2017, https://doi.org/10.1002/2017GL072866; Houston et al., 2018, https://doi.org/10.1002/2017JA024872; Kharchenko et al., 2006, https://doi.org/10.1029/2006GL026039). Motivated by the science of X‐ray generation, we describe here Juno Jupiter Energetic Particle Detector Instrument (JEDI) measurements of ions above 1 MeV and demonstrate the capability of measuring oxygen and sulfur ions with energies up to 100 MeV. We detail the process of retrieving ion fluxes from pulse width data on instruments like JEDI (called “puck's”; Clark, Cohen, et al., 2016, https://doi.org/10.1002/2017GL074366; Clark, Mauk, et al., 2016, https://doi.org/10.1002/2015JA022257; Mauk et al., 2013, https://doi.org/10.1007/s11214-013-0025-3) as well as details on retrieving very energetic particles (>20 MeV) above which the pulse width also saturates.

Reactive sputter deposition of WO3 films by using two deposition methods

Tungsten-trioxide (WO3) films were deposited using two types of sputtering systems: a planar magnetron sputtering system and a facing-target sputtering (FTS) system. The structure and gasochromic properties of the resulting films were compared, and film uniformity and gasochromic properties were found to be significantly improved when using FTS because the incidence of high-energy negative oxygen ions on the substrate during sputtering was significantly suppressed. The authors confirmed that the deposition rate of WO3 films increased by hundreds of times with an increase of the sputtering voltage from 500 to 800 V in the FTS system, and a deposition rate above 100 nm/min was easily achieved. The authors clarified that the deposition rate of the WO3 film strongly depends on the sputtering voltage under the condition of a constant sputtering current.

High-temperature superconducting nano-meanders made by ion irradiation

In this article, we report on the fabrication of very long nanowires in a meander shape patterned in a -capped thin film by high-energy oxygen ion irradiation. DC and RF characterizations outline the good superconducting properties of the nanowires whose geometry approaches the one used in single photon detectors. Their inductance, which mainly sets the maximum speed of these devices, has been measured on a wide range of temperature by mean of a resonant method. The extracted values are in agreement with the ones calculated from the geometry of the meanders and from the known London penetration depth in thin films.

Characterization of equipment for shaping and imaging hadron minibeams

For the feasibility studies of spatially fractionated hadron therapy prototypes of the equipment for hadron minibeams shaping and monitoring have been designed, built and tested. The collimators design was based on Monte Carlo simulations (Gate v.6.2). Slit and matrix collimators were used for minibeams shaping. Gafchromic films, micropixel detectors Timepix in a hybrid as well as metal mode were tested for measuring hadrons intensity distribution in minibeams. An overall beam profile was measured by the metal microstrip detector. The performance of a mini-beams shaping and monitoring equipment was characterized exploring low energy protons at the KINR Tandem generator as well as high energy carbon and oxygen ion beams at HIT (Heidelberg). The results demonstrate reliable performance of the tested equipment for shaping and imaging hadron mini-beam structures.

Formation of thin oxide layer on surface of copper caused by implantation of high-energy oxygen ions

Combination of neutron and X-ray reflectometry was used to study the vertical structure of 100 nm-thin copper films with implanted oxygen ions of energy E = [10-30] keV and doses D=[0.2-5.4]x$10^{16}$ $cm^{-2}$. The study shows that oxygen ion implantation with an energy of E = 30 keV leads to the formation of a 3 nm thick layer on the surface. Density and copper/oxygen stoichiometry of the observed surface layer are close to $Cu_2O$ oxide. We attribute the $Cu_2O$ oxide formation to highly mobilized copper atoms generated by stimulated ion implantation.

Probing charge carrier compensation in high energy ion irradiated III-V semiconductor by Raman spectroscopy and Hall measurements

Raman spectroscopy and Hall measurements have been carried out to investigate the differences in near‐surface charge carrier modulation in high energy (~100 MeV) silicon ion (Si8+) and oxygen ion (O7+) irradiated n‐GaAs. In the case of O ion irradiation, the observed decrease in carrier concentration with increase in ion fluence could be explained in the view of charge compensation by possible point defect trap centers, which can form because of elastic collisions of high energy ions with the target nuclei. In Si irradiated n‐GaAs one would expect the carrier compensation to occur at a fluence of 2.5 × 1013 ions/cm2, if the same mechanism of acceptor state formation, as in case of O irradiation, is considered. However, we observe the charge compensation in this system at a fluence of 5 × 1012 ions/cm2. We discuss the role of the complex defect states, which are formed because of the interaction of the primary point defects, in determining carrier concentration in a Si irradiated n‐GaAs wafer. The above results are combined with the reported data from the literature for high energy silver ion irradiated n‐GaAs, in order to illustrate the effect of both electronic and nuclear energy loss on trap creation and charge compensation. Copyright © 2016 John Wiley & Sons, Ltd.

Top-gated field-effect LaAlO3/SrTiO3 devices made by ion-irradiation

We present a method to fabricate top-gated field-effect devices in a LaAlO3/SrTiO3 two-dimensional electron gas (2-DEG). Prior to the gate deposition, the realisation of micron size conducting channels in the 2-DEG is achieved by an ion-irradiation with high-energy oxygen ions. After identifying the ion fluence as the key parameter that determines the electrical transport properties of the channels, we demonstrate the field-effect operation. At low temperature, the normal state resistance and the superconducting Tc can be tuned over a wide range by a top-gate voltage without any leakage. A superconductor-to-insulator quantum phase transition is observed for a strong depletion of the 2-DEG.

Influence of ionisation zone motion in high power impulse magnetron sputtering on angular ion flux and NbOx film growth

The ion energies and fluxes in the high power impulse magnetron sputtering plasma from a Nb target were analysed angularly resolved along the tangential direction of the racetrack. A reactive oxygen-containing atmosphere was used as such discharge conditions are typically employed for the synthesis of thin films. Asymmetries in the flux distribution of the recorded ions as well as their energies and charge states were noticed when varying the angle between mass-energy analyser and target surface. More positively charged ions with higher count rates in the medium energy range of their distributions were detected in than in direction, thus confirming the notion that ionisation zones (also known as spokes or plasma bunches) are associated with moving potential humps. The motion of the recorded negatively charged high-energy oxygen ions was unaffected. Nb thin films at different angles and positions were synthesised and analysed as to their structure and properties in order to correlate the observed plasma properties to the film growth conditions. The chemical composition and the film thickness varied with changing deposition angle, where the latter, similar to the ion fluxes, was higher in than in direction.

Influence of oxygen on luminescent properties of ZnWO4 crystals surface

The results of studies of emission properties of oxygen-containing ZnWO4 crystals are presented. Oxygen is incorporated into single crystals in two ways: annealing of crystals at 900 C in an oxygen atmosphere and implantation of high energy (28 MeV) oxygen ions. The observed variation of the photoluminescence intensity and excitation spectrum of emission at 2.6 eV are interpreted as the occurrence of a concentration gradient of emission centers in the crystal bulk under hearting of crystals and the dependence of the photons mean penetration depth in a crystal on their energy. In order to gain better insight into the nature of the phenomenon, time-resolved luminescence measurements were carried out.

Effect of the surface on luminescence properties of ZnWO4 crystals

The paper presents the investigation results on the effect of the oxygen incorporation modes on spectroscopic properties of ZnWO4 crystals. Oxygen is incorporated into single crystals in two ways: in annealing at 900°C in oxygen atmosphere and implantation of high energy (28MeV) oxygen ions. It was found that the changes in the state of the crystal surface under different treatments lead to interesting differences in the emitting properties of the material. In order to gain better insight into the nature of the phenomenon, time-resolved luminescence measurements were carried out.

Manganite based memristors: Influence of the electroforming polarity on the electrical behavior and radiation hardness

We report on the fabrication and characterization of La2/3Ca1/3MnO3 manganite-based memristive devices. Polycrystalline manganite thin films were grown by Pulsed Laser Deposition, while metallic electrodes were deposited by sputtering. We show that, depending on the polarity of the initial electroforming, both clockwise and anti-clockwise current–voltage curves can be obtained. We attribute this behavior to the coexistence of different resistive switching mechanisms. We finally evaluate the electrical behavior of our devices after irradiation with high energy oxygen ions. We find no significant difference in the dielectric breakdown voltages between irradiated and non-irradiated devices, indicating that they may present radiation hardness and could be therefore appropriate for space or nuclear applications.