Energy Xe Ions Research Articles

Dynamics of nanoscale triangular features on Ge surfaces

Ion beam sputtering, known as potential technique for producing nanoripple on various surfaces having wide range of applications. Along with nanoripple, triangular features are also superimposed, limiting their use for some potential applications. Here we are reporting evolution of triangular features on Ge (100) surfaces under low energy (300–1000 eV) Xe ion irradiation at room temperature for angles of incidence (61°–80°) and ion fluences of (5.34 × 1017−8.01 × 1018 ions cm−2). Triangular features appear with the onset of ripple formation and disappear when the ripple periodicity is lost. These features formation depend not only on material but also depend on the ratio of the ion/target mass. In comparison with numerical simulations based on modified anisotropic Kuramoto-Sivanshinsky equation, we find good agreement for the evolution of base angle and lateral length for the triangular features with ion incidence angle. The dynamics of triangular feature with ion incidence angle and ion fluence have been reported. Ion-incidence angle dependency is adequately replicated in numerical simulations. Experimentally the base angle and lateral length increases with increase in ion incidence angle, similar trend is observed in numerical simulation.

Optimized deceleration characteristics of multicharged ion beams from electron cyclotron resonance ion source

At present it is necessary the satellite lifetime 10-15 years for operating in space. Xenon is used as fuel for ion engines of satellites. There are problems of accumulated damages at irradiation and sputtering by low energy Xe ion from the engine. It is required to construct database of sputtering yield of ion beams in the low energy region from a hundred eV to 1keV. We are trying to investigate experimentally sputtering yield on satellite component by irradiating the low energy Xe q+ ion beams. We use the electron cyclotron resonance ion source (ECRIS) in the irradiation experiments. We decelerate the beam energy to several hundred eV after extraction at high voltage 10kV. It is found we cannot neglect the contribution of the space potential of the plasma in the ECRIS of several tens eV. We measured the plasma parameters and ion beam deceleration characteristics in operating conditions on ECRIS. As the results, it was found in operating ECRIS condition of low charge state ion being dominant that the space potential of the ECRIS has an effect of 10∼20% at the beam energy at about 100eV in conducting irradiation experiments on satellite component materials.

Memristive FG-PVA Structures Fabricated with the Use of High Energy Xe Ion Irradiation.

A new approach based on the irradiation by heavy high energy ions (Xe ions with 26 and 167 MeV) was used for the creation of graphene quantum dots in the fluorinated matrix and the formation of the memristors in double-layer structures consisting of fluorinated graphene (FG) on polyvinyl alcohol (PVA). As a result, memristive switchings with an ON/OFF current relation ~2–4 orders of magnitude were observed in 2D printed crossbar structures with the active layer consisting of dielectric FG films on PVA after ion irradiation. All used ion energies and fluences (3 × 1010 and 3 × 1011 cm−2) led to the appearance of memristive switchings. Pockets with 103 pulses through each sample were passed for testing, and any changes in the ON/OFF current ratio were not observed. Pulse measurements allowed us to determine the time of crossbar structures opening of about 30–40 ns for the opening voltage of 2.5 V. Thus, the graphene quantum dots created in the fluorinated matrix by the high energy ions are a perspective approach for the development of flexible memristors and signal processing.

Improving transport and optimizing deceleration of ion beams from electron cyclotron resonance multicharged ion sources.

Electron cyclotron resonance ion sources (ECRISs) are widely applied for ion beam applications, e.g., plasma processing, cancer therapy, and ion engine of an artificial satellite. In our ECRIS, we aim at producing and extracting various ion beams from this device, in particular, Xeq+ ion beams at low energy. In the aerospace engineering field, there are problems of accumulated damages on various component materials caused by low energy of Xe ions from the engine. There are not enough experimental sputtering data for satellite materials at the Xeq+ in the low energy region. Then, we are trying to investigate the sputtering yield experimentally by irradiating the low energy Xe ion beams. To perform this experiment, it is necessary to acquire a certain amount of beam current with low energy. Then, we generate the low energy ion beams by the following steps: First, the ion beams are extracted from the ECRIS at high voltage. Next, these are transported to an ion beam irradiation system (IBIS). Finally, the ion beams are decelerated by the deceleration voltage in the IBIS. We adjusted the beamline. We measure the characteristics of the transport efficiency and decelerated ion beam currents. In this paper, we describe the experimental setup using an existing ECRIS for decelerated heavy ion beams and the results of decelerated ion beam currents.

TEM Study of ODS Alloy Doped with Helium Ions and Re-irradiated with Swift Xe Ions

Oxide dispersion strengthened (ODS) alloys are considered as candidates for fuel assembly claddings, since nano-oxides, among other things, contribute to the gas swelling suppression. However, it is still unknown that how oxides will behave in this capacity under the exposure to fission fragments. Transmission electron microscopy has been applied to study helium porosity in a ferritic EP450ODS alloy doped with helium by the ion implantation and re-irradiated with high energy Xe ions, which is used for simulating fission fragments at room temperature followed by annealing. It has been shown that helium bubbles mainly decorate the structural defects and grain boundaries both in helium doped only and in re-irradiated with Xe samples. Furthermore, we have found that there was not significant changes in the size distributions of helium bubbles in ferritic matrix due to the re-irradiation with Xe. The only effect of irradiation with swift Xe ions on the alloy structure is the amorphization of dispersed oxides in it. But, as a result of amorphization of dispersed oxides, helium bubbles were detected at the oxide-matrix (O-M) interfaces as well as inside amorphous oxides, while they have not been observed inside crystalline nano-oxides and seldom connecting to the O-M interface in the He-doped only samples. That means the nano-oxides amorphized by fission fragments can promote the better helium bubbles pinning in actual operation of the fuel assembly cladding in a nuclear reactor.

Comparison of hardness variation of ion irradiated borosilicate glasses with different projected ranges

Abstract Borosilicate glass has potential application for vitrification of high-level radioactive waste, which attracts extensive interest in studying its radiation durability. In this study, sodium borosilicate glass samples were irradiated with 4 MeV Kr 17+ ion, 5 MeV Xe 26+ ion and 0.3 MeV P + ion, respectively. The hardness of irradiated borosilicate glass samples was measured with nanoindentation in continuous stiffness mode and quasi continuous stiffness mode, separately. Extrapolation method, mean value method, squared extrapolation method and selected point method are used to obtain hardness of irradiated glass and a comparison among these four methods is conducted. The extrapolation method is suggested to analyze the hardness of ion irradiated glass. With increasing irradiation dose, the values of hardness for samples irradiated with Kr, Xe and P ions dropped and then saturated at 0.02 dpa. Besides, both the maximum variations and decay constants for three kinds of ions with different energies are similar indicates the similarity behind the hardness variation in glasses after irradiation. Furthermore, the hardness variation of low energy P ion irradiated samples whose range is much smaller than those of high energy Kr and Xe ions, has the same trend as that of Kr and Xe ions. It suggested that electronic energy loss did not play a significant role in hardness decrease for irradiation of low energy ions.

Conicity of latent tracks in the near surface region as a factor affecting the correct evaluation of track size

AbstractThe difference in track parameters recorded in some oxides at the same energy loss and different ion velocity, the so called “velocity effect”, have been corroborated by various experimental methods. Most of the corresponding data on damage cross section and then on the track radii were found by means of indirect techniques such as Rutherford backscattering spectroscopy in channelling geometry. The contribution of transmission electron microscopy results in the whole data array remains very limited. In this report we present an analysis of existing TEM results related to the “velocity effect” and consider how the conical shape of latent tracks observed in the subsurface region of swift heavy ion irradiated oxides may affect the correct determination of the track size as well as the critical electronic energy loss for track formation. The discussion is based on our cross sectional TEM studies of high energy Bi and Xe ion induced latent tracks in TiO2 and Al2O3 single crystals. To our knowledge there have been no reported cross sectional TEM analyses on Y3Fe5O12, Bi4Ge3O12 and YBa2Cu3O7‐δ in order to verify the cylindrical track assumption. If similar conicity exists in the near surface regions of these materials it may cast some doubt on the validity of the velocity effect. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Defect studies of zirconia implanted by high energy Xe ions

In the present work positron lifetime spectroscopy was employed for characterization of radiation-induced defects in yttria stabilized zirconia (YSZ) implanted by 167 MeV Xe ions. Positron lifetime data were interpreted with aid of ab-initio theoretical modelling of defects in YSZ lattice. Damage caused by Xe implantation was investigated in two YSZ samples with different microstructure: (i) single crystal and (ii) sintered ceramic. The virgin YSZ single crystal exhibits single component spectrum with lifetime of ≈ 180 ps. Similar lifetime component was found also in the virgin sample of sintered YSZ ceramic. Since this lifetime is significantly higher than the YSZ bulk lifetime the virgin YSZ crystal and the sintered ceramic both contain vacancy-like defects. Xe implantation leads to appearance of additional defect component with longer lifetime ≈ 370 ps which comes obviously from vacancy clusters fonned by agglomeration of irradiation induced vacancies. A broad absorption band with peak absorption at ≈ 518 nm was found in Xe-implanted crystal by optical measurements.

Characterization of high energy Xe ion irradiation effects in single crystal molybdenum with depth-resolved synchrotron microbeam diffraction

Microbeam X-ray diffraction experiments were conducted at beam line 34-ID of the Advanced Photon Source (APS) on fission fragment energy Xe heavy ion irradiated single crystal Molybdenum (Mo). Lattice strain measurements were obtained with a depth resolution of 0.7 μm, which is critical in resolving the peculiar heterogeneity of irradiation damage associated with heavy ion irradiation. Q-space diffraction peak shift measurements were correlated with lattice strain induced by the ion irradiations. Transmission electron microscopy (TEM) characterizations were performed on the as-irradiated materials as well. Nanometer sized Xe bubble microstructures were observed via TEM. Molecular Dynamics (MD) simulations were performed to help interpret the lattice strain measurement results from the experiment. This study showed that the irradiation effects by fission fragment energy Xe ion irradiations can be collaboratively understood with the depth resolved X-ray diffraction and TEM measurements under the assistance of MD simulations.

Erratum to: Raman Scattering in Natural Diamond Crystals Implanted with High-Energy Ions and Irradiated with Fast Neutrons

Raman scattering is studied in natural diamond crystals with radiation-induced defects produced by implantation of high energy Xe and Kr ions (ion kinetic energy >1 MeV/amu) and by irradiation with fast reactor neutrons (kinetic energy >100 keV). Confocal measurements of the Raman spectra along the surface of an oblique section of the ionimplanted diamonds are used to study the radiation damage profile. The evolution of the Raman scattering spectra with depth of the damaged layer in the ion-implanted diamonds, and as a function of annealing temperature of the neutron-irradiated diamond, is determined by spatial localization of phonons in the radiation disordered crystal lattice and by the formation of associations of intrinsic defects in the lattice.

Raman Scattering in Natural Diamond Crystals Implanted with High-Energy Ions and Irradiated with Fast Neutrons

Raman scattering is studied in natural diamond crystals with radiation-induced defects produced by implantation of high energy Xe and Kr ions (ion kinetic energy >1 MeV/amu) and by irradiation with fast reactor neutrons (kinetic energy >100 keV). Confocal measurements of the Raman spectra along the surface of an oblique section of the ionimplanted diamonds are used to study the radiation damage profile. The evolution of the Raman scattering spectra with depth of the damaged layer in the ion-implanted diamonds, and as a function of annealing temperature of the neutron-irradiated diamond, is determined by spatial localization of phonons in the radiation disordered crystal lattice and by the formation of associations of intrinsic defects in the lattice.

Influence of ion-beam bombardment on the physical properties of 100Cr6 steel

The effect of ion-beam bombardment with low energy Xe ions on the physical properties of 100Cr6 steel is reported. The modified region induced by the relative low energy ions (<1 keV) extends orders of magnitude deeper than the stopping length of the impacting ions. The energy dependence of the in-depth stress and the pattern formation is also verified. The formation of peculiar patterns on the treated surface is discussed by evoking the current model of surface instability produced by preferential sputtering and surface diffusion in metals.

TEM study of damage recovery in SiC by swift Xe ion irradiation

The microstructure of 4H–SiC samples subsequently irradiated with low energy He (10keV), Ti (220keV) and high energy (167MeV) Xe ions has been studied using cross-sectional transmission electron microscopy. It was found that xenon ions with fluences above 1013cm−2 restore crystallinity in a heavily damaged partially amorphous zone. No, or negligible damage recovery is observed in fully amorphized layers of silicon carbide.

1.2 MeV/amu Xe ion induced damage recovery in SiC

The microstructural changes of 4H-SiC samples dual irradiated with either low energy He (10keV) or Ti (220keV) and high energy (167MeV) Xe ions has been studied using cross-sectional transmission electron microscopy. It was found that xenon ions with fluences above 1013cm−2 restore crystallinity in a heavily damaged partially amorphous zone. No significant damage recovery was observed in fully amorphized layers of silicon carbide apart from a 5% reduction in the amorphous layer thickness.

Phase transformations in Y2O3 thin films under swift Xe ions irradiation

Yttrium oxide (Y2O3) thin films deposited on silicon (Si) by an ion beam sputtering technique have been irradiated by 92MeV xenon ions at room temperature. The microstructure of the irradiated thin film has been studied by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS). A complete structural conversion from the cubic C-type to a monoclinic B-type phase is obtained. These results were compared with the phase transformation obtained in Y2O3 thin films by medium energy Xe ion irradiation. In both cases the oxygen network behaviour under irradiation is the key parameter of the phase transformation.

Ion Impacts on Graphene/Ir(111): Interface Channeling, Vacancy Funnels, and a Nanomesh

By combining ion beam experiments and atomistic simulations we study the production of defects in graphene on Ir(111) under grazing incidence of low energy Xe ions. We demonstrate that the ions are channeled in between graphene and the substrate, giving rise to chains of vacancy clusters with their edges bending down toward the substrate. These clusters self-organize to a graphene nanomesh via thermally activated diffusion as their formation energy varies within the graphene moiré supercell.

Electrophysical and Optical Properties of 4H-SiC Irradiated with Xe Ions

A comparative research of the cathodoluminescence and electrical characteristics of the samples 4H-SiC irradiated with high energy Xe ions (167 MeV) in wide range fluencies 4x109 –1x1011 cm-2 at temperatures 250C and 5000C are presented. After irradiation these samples were thermal annealed at 5000C for 30 min. Far-action effect at a depth of more than one order of magnitude of stopping distance was observed under Xe ions irradiation in 4H-SiC. An increase of the ion Xe fluencies increased the concentration of radiation-induced defects that resulted in rise of the compensation effect of conductivity in samples. Irradiation of 4H-SiC by Xe ions at 5000C was accompanied with "dynamic annealing" some low-temperature radiation-induced defects, which led to a partial recovery of the electrical characteristics of devices. The thermal annealing of irradiated samples led to additional partial annealing of radiation defects, which increases the radiation resource of devices based on 4H-SiC.

Ion beam induced surface patterns due to mass redistribution and curvature-dependent sputtering

Recently it was reported that ion-induced mass redistribution would solely determine nano pattern formation on ion-irradiated surfaces. We investigate the pattern formation on amorphous carbon thin films irradiated with Xe ions of energies between 200 eV and 10 keV. Sputter yield as well as number of displacements within the collision cascade vary strongly as function of ion energy and allow us to investigate the contributions of curvature-dependent erosion according to the Bradley-Harper model as well as mass redistribution according to the Carter-Vishnyakov model. We find parallel ripple orientations for an ion incidence angle of 60\ifmmode^\circ\else\textdegree\fi{} and for all energies. A transition to perpendicular pattern orientation or a rather flat surface occurs around 80\ifmmode^\circ\else\textdegree\fi{} for energies between 1 keV and 10 keV. Our results are compared with calculations based on both models. For the calculations we extract the shape and size of Sigmund's energy ellipsoid (parameters $a$, \ensuremath{\sigma}, \ensuremath{\mu}), the angle-dependent sputter yield, and the mean mass redistribution distance from the Monte Carlo simulations with program SDTrimSP. The calculated curvature coefficients ${S}_{x}$ and ${S}_{y}$ describing the height evolution of the surface show that mass redistribution is dominant for parallel pattern formation in the whole energy regime. Furthermore, the angle where the parallel pattern orientation starts to disappear is related to curvature-dependent sputtering. In addition, we investigate the case of Pt erosion with 200 eV Ne ions, where mass redistribution vanishes. In this case, we observe perpendicular ripple orientation in accordance with curvature-dependent sputtering and the predictions of the Bradley-Harper model.

0.5 keV Xe+ ion beam nano smoothing of ULE® substrate after processing with 3.0–10.0 keV Xe+ ion beam

Ion beam figuring (IBF) is a suitable technology for the final shape correction of substrates used in the projection optics of EUVL tools. Generally the ULE® substrate with surface roughness of 0.060–0.080nm rms can be produced with mechanical machining methods. However, it is very difficult to obtain the shape accuracy of approximately 0.120nm rms using mechanical machining methods. Therefore, ion beam figuring (IBF) may be adapted for the final shape correction of the substrates. In this paper, we investigated a method in which a low energy 0.5keV Xe+ ion beam is used for smoothing of ULE® substrates which were first figured using high energy (3.0, 5.0, 7.0 and 10.0keV) Xe-ions beams (1mm diameter). The result shows that the ULE® substrate is roughened by 3.0–10.0keV Xe+ ion beam (first stage processing) can be smoothened by 0.5keV Xe+ ion beam (second stage processing) and reached to 0.120nm rms. Therefore, our proposed smoothing method is one of the best methods for the figure error correction of the ULE® substrate for EUVL projection optics.

Nanoindentation investigation of heavy ion irradiated Ti3(Si,Al)C2

Abstract Because of good damage tolerance, thermal stability and interesting mechanical properties, Ti3SiC2, belonging to Mn+1AXn phases, has been considered as a potential candidate material for applications in the future Gas Fast nuclear Reactors (GFR) such as components of fuel cladding working between 500 °C and 800 °C. However, the outstanding mechanical properties of Ti3SiC2 related to a layered microstructure could be impacted by irradiation. In this work, high energy Kr and Xe ion irradiated Ti3Si0.95Al0.05C2 and Ti3Si0.90Al0.10C2 samples, provided by IMR Shenyang, Chinese Academy of Science, were characterized by nanoindentation technique. After irradiation at room temperature, an increase in hardness with irradiation dose was highlighted. Nevertheless, some damage tolerance remained because of preservation of the typical MAX layered structure. Irradiations at 300 °C and 500 °C lead to less significant increase suggesting irradiation defect annealing. A complete recovery of the properties at 800 °C seems to be obtained.