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When subjected to swift heavy ion (SHI) irradiation, a lattice acquires sufficient energy to induce desirable flaws in the material. In this study, the physiochemical properties of Sn-doped V2O5 (SVO) synthesized by a sol–gel process were thoroughly examined following irradiation with Ni+11 ions at 150 MeV energy and fluence of 2.51 × 1011 ions/cm2. The successful doping of Sn in V2O5 was confirmed by an increase in tensile strain, as revealed by the x-ray diffraction (XRD) spectrum, and the presence of characteristic peaks of constituent elements detected in the energy-dispersive x-ray (EDX) spectrum. Atomic force microscopy (AFM) and field-emission scanning microscopy (FESEM) images revealed an increase in surface roughness and transformation to an amorphous state, respectively. The Tauc plot indicated an increase in the electronic bandgap post-irradiation. Fourier transform infrared (FTIR) spectroscopy analysis revealed a peak shift in the fingerprint region indicating a change in the vibrational energy of the involved molecular bonds. These findings highlight the potential of SHI irradiation for the tuning of material properties, paving the way for a wide range of functional applications of the material. [ABSTRACT FROM AUTHOR]

Track radii Re induced by swift heavy ions are studied. The experimental track data are analyzed in Gd2Ti2O7 pyrochlore in the range Se = 6−54 keV nm−1 (Se: electronic stopping power), including irradiations by low‐ and high‐velocity ions. The Analytical Thermal Spike Model (ATSM) is applied, whose main features are reviewed. The track data of Gd2Ti2O7 exhibit scaling features which mean simple quantitative relationships with track sizes of other insulators controlled only by a single materials parameter (MP), the melting temperature Tm. The Re2−Se track evolution curve is described in the whole range of Se without the application of any individual fitting parameter and MPs apart from Tm; the thresholds for track formation are Set = 6.1 and 14.4 keV nm−1 for E < 2 MeV/nucleon and E > 8 MeV/nucleon, respectively. The unique role of Tm is a highly important limitation for the mechanism of track formation. The practical consequences of the results are discussed with respect to the estimation of irradiation parameters. [ABSTRACT FROM AUTHOR]

Track radii Re induced by swift heavy ions are studied. The experimental track data are analyzed in Gd2Ti2O7 pyrochlore in the range Se = 6−54 keV nm−1 (Se: electronic stopping power), including irradiations by low‐ and high‐velocity ions. The Analytical Thermal Spike Model (ATSM) is applied, whose main features are reviewed. The track data of Gd2Ti2O7 exhibit scaling features which mean simple quantitative relationships with track sizes of other insulators controlled only by a single materials parameter (MP), the melting temperature Tm. The Re2−Se track evolution curve is described in the whole range of Se without the application of any individual fitting parameter and MPs apart from Tm; the thresholds for track formation are Set = 6.1 and 14.4 keV nm−1 for E < 2 MeV/nucleon and E > 8 MeV/nucleon, respectively. The unique role of Tm is a highly important limitation for the mechanism of track formation. The practical consequences of the results are discussed with respect to the estimation of irradiation parameters. [ABSTRACT FROM AUTHOR]

The sources of heavy cluster ions (Au, Bi) used in modern mass spectrometers suggest that the emission of secondary ions is predominantly performed in the thermal spike mode, unlike the previous generation of spectrometers operating with atomic cesium ions and oxygen ions. Here, we verify this assumption using the example of the emission of 11 implanted elements from GaAs upon sputtering by bismuth ions with an energy of 30 keV. The obtained data on the relative sensitivity factors are analyzed using semiconductor-band theory and the assumption of melt production in the case of the formation of thermal spikes. [ABSTRACT FROM AUTHOR]

The effect of the target temperature on sputtering by gas cluster ions was investigated using molecular dynamics simulation. The temperature of <111> copper target was set in range from 300 K to 1100 K, and bombarding 10 keV argon clusters had the size from 50 to 500 atoms. Sputter yield was found to increase with the temperature. The increase depended on the cluster size, and its value was much higher than it had been considered previously for nonlinear sputtering. Differential characteristics of the process, such as angular, energy, and time distributions of the sputtered atoms, as well as their initial positions, were obtained to promote understanding of the mechanisms involved. The dynamics of the collision crater size and its shape were described. The concept of temperature inside the collision area was used to explain the results. • Gas cluster ion beams impacts on copper investigated by molecular dynamics. • Sputter yield increases significantly with target temperature increase. • The increase is higher for large clusters. • Peculiarities of energy transfer from cluster to surface can explain the results. • The effect is significant enough for experimental observation. [ABSTRACT FROM AUTHOR]

The optical emission spectra of pure metals Fe, Zr, Ta and W are measured during their irradiation with Ar+, Kr+ and Xe+ ions (5, 10, 15 and 20 keV). It is found out that the energy and ion type in this energy range do not appreciably affect the thermal emission spectral profile of these targets and hence do not influence the thermal spike temperature formed in the zones of passing dense cascades of atomic displacements. It is shown that a constant temperature regime of the thermal peaks (T = const) is fulfilled in the case where the average radius R of the cascade region is proportional to the square root of the incident ion energy R ∼ E , and the major part of the thermal energy is released at the cascade periphery of a fixed length. As a result, the energy per atom of the medium, released in this region, does not vary with the ion energy and cascade radius. It is also shown that the thermal spike temperature for all ion types essentially depends on the target material. [ABSTRACT FROM AUTHOR]

We report on the first observation of fine structure of latent tracks in rutile TiO 2 , which changes from cylinder to dumbbell-shape and then to sandglass-shape as a function of the ion path length. Moreover, the cone length of the track was found to be dependent on electronic energy loss. The results indicate that outflow of the thermal spike-induced molten phase produces the hillocks on surface and the void-rich zone near surface after epitaxial recrystallization due to material deficit, while at a deep depth, the lack of efficient outflow and recrystallization result in the absence of tracks. We propose that the various morphologies of tracks in rutile TiO 2 are a consequence of the molten phase outflow and recrystallization during rapid cooling down. [ABSTRACT FROM AUTHOR]

Tungsten carbide (WC) is an important material to study for various applications in extreme environments due to its radiation-resistant properties and high mechanical strength. Due to its excellent properties such as high hardness, strength, and wear resistance, it is also being considered lately as a plasma facing component in nuclear fusion reactors. To study the response of this material in extreme radiation environments, WC films prepared using RF sputtering technique were irradiated with 100 MeV Ag8+ ions in the present work. The irradiation was carried out at three different fluences: 3 × 1012, 1 × 1013, and 3 × 1013 ions/cm2. Rutherford Backscattering Spectrometry (RBS) was performed to determine the stoichiometry and thickness of the pristine film. To study the irradiation-induced modifications, glancing angle X-ray diffraction (GAXRD), field emission scanning electron microscopy (FE-SEM), High Resolution Transmission Electron Microscopy (HRTEM), and Raman spectroscopy were performed on the pristine and irradiated samples. GAXRD of the pristine and irradiated samples revealed grain size reduction accompanied with reduced crystallinity with increasing ion fluence which was further manifested in HRTEM measurements and Raman spectroscopy measurements. Change in surface morphology due to the ion irradiation was observed in FE-SEM. These modifications have been explained using thermal-spike and TRIM simulations which showed that although the swift heavy ions irradiation did not result in track formation in the WC films, it caused radiation damage which may be attributed to the synergistic effect of electronic and nuclear energy loss mechanisms. These results might be crucial for a fundamental understanding of the radiation resistance of WC thin films and its application in different radiation environments. • Study examines 100 MeV Ag8+ ion impact on WC films. • Higher ion fluence reduces grain size, and crystallinity (GAXRD, HRTEM, Raman). • Thermal-spike simulations show no ion tracks, but damage occurs. • TRIM estimates lower radiation damage than observed experimentally. • Damage attributed to combined effects of electronic excitations (S e) and ballistic collisions (S n). [ABSTRACT FROM AUTHOR]

Abstract Ion track formation in amorphous SiO 2 was investigated using infrared spectroscopy. For comparison, one set of samples was also irradiated using 1.25 MeV gamma rays. An increase of 1044 cm−1 peak and decrease of 1078 cm−1 peak was observed in all cases. Experimental results were analysed using an analytical thermal spike model and non-standard model parameters were found. This finding is attributed to the amorphous structure of the material. Highlights • Damage kinetics in a-SiO 2 due to swift heavy ion and gamma ray irradiation was measured using infrared spectroscopy. • Ion track cross sections were compared to the predictions of the analytical thermal spike model. • Available literature data on ion tracks in a-SiO 2 was analysed using analytical thermal spike model. [ABSTRACT FROM AUTHOR]

Abstract Scientific understanding of any kind of radiation effects starts from the primary damage, i.e. the defects that are produced right after an initial atomic displacement event initiated by a high-energy particle. In this Review, we consider the extensive experimental and computer simulation studies that have been performed over the past several decades on what the nature of the primary damage is. We review both the production of crystallographic or topological defects in materials as well as radiation mixing, i.e. the process where atoms in perfect crystallographic positions exchange positions with other ones in non-defective positions. All classes of materials except biological materials are considered. We also consider the recent effort to provide alternatives to the current international standard for quantifying this energetic particle damage, the Norgett-Robinson-Torrens displacements per atom (NRT-dpa) model for metals. We present in detail new complementary displacement production estimators ("athermal recombination corrected dpa", arc-dpa) and atomic mixing ("replacements per atom", rpa) functions that extend the NRT-dpa, and discuss their advantages and limitations. [ABSTRACT FROM AUTHOR]

In this paper, we have developed a model of radiation-induced densification of uranium-gadolinium fuel. The fuel is established to be in the brittle state under irradiation in the volume of uranium-gadolinium fuel pellet containing a burnable neutron absorber and in the plastic state out of this volume. The plastic zone volume increases during burnup of the neutron absorber. The relative change in a pellet volume or length of a fuel rod for uranium-gadolinium fuel is shown to be lower than that for uranium oxide nuclear fuel having the same microstructure and irradiated under the same conditions (the neutron flux). [ABSTRACT FROM AUTHOR]

The radiation hardness of amorphous Ge2Sb2Te5 phase-change random-access memory material has been elucidated by ab initio molecular-dynamics simulations. Ionizing radiation events have been modeled to investigate their effect on the atomic and electronic structure of the glass. Investigation of the short- and medium-range order highlights a structural recovery of the amorphous network after exposure to the high-energy events modeled in this study. Analysis of the modeled glasses reveals specific structural rearrangements in the local atomic geometry of the glass, as well as an increase in the formation of large shortest-path rings. The electronic structure of the modeled system is not significantly affected by the ionizing radiation events, since negligible differences have been observed before and after irradiation. These results provide a detailed insight into the atomistic structure of amorphous Ge2Sb2Te5 after irradiation and demonstrate the radiation hardness of the glass matrix. [ABSTRACT FROM AUTHOR]

Total currents of positive and negative particles arising under bombardment of metal surfaces with argon gas cluster ions were measured for the energy range 2–15 keV. Supposing that the negative current was defined by secondary electrons, and the positive current is the flow of the reflected argon ions, the possible mechanisms of electron emission and charge transfer are discussed. The discussion is supported by molecular dynamics simulations of cluster-surface collisions. • Yields of particles from metal surface under Ar clusters bombardment are studied. • The negative particles are considered to be electrons. • Electron emission is stimulated by the high local temperature in the impact area. • The positive particles are supposed to be reflected argon ions. • Charge transfer from a cluster to a surface is mediated by collision ionization. [ABSTRACT FROM AUTHOR]

The development of TEM-visible damage in materials under irradiation at cryogenic temperatures cannot be explained using classical rate theory modeling with thermally activated reactions since at low temperatures thermal reaction rates are too low. Although point defect mobility approaches zero at low temperature, the thermal spikes induced by displacement cascades enable some atom mobility as it cools. In this work a model is developed to calculate “athermal” reaction rates from the atomic mobility within the irradiation-induced thermal spikes, including both displacement cascades and electronic stopping. The athermal reaction rates are added to a simple rate theory cluster dynamics model to allow for the simulation of microstructure evolution during irradiation at cryogenic temperatures. The rate theory model is applied to in-situ irradiation of ZrC and compares well at cryogenic temperatures. The results show that the addition of the thermal spike model makes it possible to rationalize microstructure evolution in the low temperature regime. [ABSTRACT FROM AUTHOR]

Gold and platinum nanoparticles of few-nm size were deposited on amorphous silicon oxide and amorphous silicon nitride films. These films were irradiated with 0.72 and 1.1 MeV C 60 3+ ions. Local heating of these films induced by the single ion impact was evaluated by observing desorption of the nanoparticles from the target surfaces upon ion impact. It was found that the local heating at the exit surface is very sensitive to the film thickness. For thinner films, the observed local heating at the exit surface is enhanced compared to the entrance surface while the result is opposite for thicker films. The observed result can be well explained by the unified thermal spike model taking account of the broadening of the spatial distribution of constituent carbon ions during the passage across the film. [ABSTRACT FROM AUTHOR]

Metal–graphene nanocomposites are expected to have excellent radiation resistance. The intrinsic role of the graphene layers (GrLs) in their performance has not been fully understood. Five copper–graphene nanocomposite (CGNC) systems were used to investigate the detailed mechanisms underpinning this behaviour by atomistic simulation. Results showed that GrLs can reduce the formation, growth, and intensity of the thermal spike of CGNC; this effect became more evident with the increasing number of layers of graphene. The role of the GrLs can be explained by three mechanisms: first, the ultra-strength C–C bonds of graphene hindered the penetration of high-energy atoms, second, the number of recoiled atoms decreased with the increasing number of layers of graphene, and third, the energy dissipation along the graphene planes also indirectly weakened the damage caused to the entire system. These mechanisms may provide a pathway to prevent material degradation in extreme radiation environments. [ABSTRACT FROM AUTHOR]

Crystalline and preamorphized isotope multilayers are utilized to investigate the dependence of ion beam mixing in silicon (Si), germanium (Ge), and silicon germanium (SiGe) on the atomic structure of the sample, temperature, ion flux, and electrical doping by the implanted ions. The magnitude of mixing is determined by secondary ion mass spectrometry. Rutherford backscattering spectrometry in channeling geometry, Raman spectroscopy, and transmission electron microscopy provide information about the structural state after ion irradiation. Different temperature regimes with characteristic mixing properties are identified. A disparity in atomic mixing of Si and Ge becomes evident while SiGe shows an intermediate behavior. Overall, atomic mixing increases with temperature, and it is stronger in the amorphous than in the crystalline state. Ion-beam-induced mixing in Ge shows no dependence on doping by the implanted ions. In contrast, a doping effect is found in Si at higher temperature. Molecular dynamics simulations clearly show that ion beam mixing in Ge is mainly determined by the thermal spike mechanism. In the case of Si thermal spike, mixing prevails at low temperature whereas ion beam-induced enhanced self-diffusion dominates the atomic mixing at high temperature. The latter process is attributed to highly mobile Si di-interstitials formed under irradiation and during damage annealing. [ABSTRACT FROM AUTHOR]

We report and provide justification for the consistently observed four experimental facts of mass spectrometric data of carbon cluster emission from the Cs+-irradiated single-walled carbon nanotubes (SWCNTs). Firstly, the diatomic carbon C2is the most abundant sputtered species. Secondly, monatomic carbon C1yield is Cs+energy dependent. Thirdly, at low caesium energies, only C2, C3and C4are emitted. Lastly, the normalised yield of C1monotonically increases while C2, C3and C4show gradual decrease leading to saturation. The experimental data for the normalised density of clusters and atoms follow the pattern >  >  > . A statistical thermal model is developed to explain the experimentally observed sputtering of clusters. The probability of a cluster Cxto be emitted is proportional to that for the creation of anx-member vacancy with formation energyExvat temperatureTsas {exp(Exv/kTS) + 1}−1. The energies of formation of vacancies from DFT calculations and the ratio of normalised experimental yields have been used to estimateTS. OnceTsis evaluated, the formation energies of tri- and quarto-vacancies are obtained using the ratios of normalised densitiesand. We show that by invoking thermal spikes, cluster emission from, and the multiple vacancy generation in, the Cs+-irradiated SWCNTs can be explained. [ABSTRACT FROM AUTHOR]

Cluster ion beams are a perspective tool for surface structuring and analysis due to nonlinear processes occurring under cluster-surface interaction. We focused our attention on the experimental and molecular dynamics simulation study of gold sputtering with bismuth cluster ions. In addition, a copper target was also investigated where etched craters were examined. Non-additive behavior of sputter yields is discussed in terms of Sigmund and Claussen thermal spike models. These simulations have allowed us to compare penetration of atomic and cluster bismuth into the targets as well as studying the differential characteristics of sputtering. • Sputtering of Cu and Au targets by bismuths cluster ions. • Experimental and molecular dynamics simulation study of etched craters. • Non-additive sputter yields in terms of Sigmund and Claussen thermal spike models. • Comparing penetration of atomic and cluster bismuth ions into Cu and Au targets. [ABSTRACT FROM AUTHOR]

While gold nanoparticles (Au NPs) are widely used as surface-enhanced Raman spectroscopy (SERS) substrates, their agglomeration and dynamic movement under laser irradiation result in the major drawback in SERS applications, viz., the repeatability of SERS signals. We tune the optical and structural properties of size- and shape-modified Au NPs embedded in a thin silicon nitride (Si 3 N 4 ) matrix by intense electronic excitation with swift heavy ion (SHI) irradiation with the aim of overcoming this classical SERS disadvantage. We demonstrate the shape evolution of a single layer of Au NPs inserted between amorphous Si 3 N 4 thin films under fluences of 120 MeV Au 9+ ions ranging between 1 × 10 11 and 1 × 10 13 ions cm -2 . This shape modification results in the gradual blue shift of the localized surface plasmon resonance (LSPR) dip until 1 × 10 12 ions/cm 2 and then a sudden diminishment at 1 × 10 13 ions/cm 2 . Finite domain time difference (FDTD) simulations further justify our experimental optical spectra. The dynamical NP aggregation and dissolution, in addition to NP elongation and deformation at different fluences, are noted from 2D grazing incidence small-angle X-ray scattering (GISAXS) profiles, as well as cross-sectional transmission electron microscopy (X-TEM). The systematic shape evolution of metal NPs embedded in the insulating matrix is shown to be due to thermal spike-induced localized melting and a localized pressure hike upon SHI irradiation. Utilizing this specific control over the characteristics of Au NPs, viz ., shape, size, interparticle gap, and corresponding optical response via SHI irradiation, we demonstrate their applications as very stable SERS substrates, where the separation between NPs and analyte does not alter under laser illumination. Thus, these irradiated SERS active substrates with controlled NP size and gap provide the optimal conditions for creating localized electromagnetic hotspots that amplify the SERS signals, which do not alter with time or laser exposure. We found that the film irradiated with 1 × 10 11 exhibits the highest SERS intensity due to its optimal NP size distribution and shape. Thus, not only our study provides a SERS substrate for stable and repeatable signals but also the understanding depicted here opens new research avenues in designing SERS substrates, photovoltaics, optoelectronic devices, etc. with ion beam irradiation.

Influence of the swift heavy ions (SHIs) at various ion fluences in nanodimensional polycrystalline fluoride thin films (LiF, CaF 2 and BaF 2 ) were investigated by glancing angle X-ray diffraction (GAXRD), complemented by atomic force microscopy (AFM). Nano-grain fragmentation is observed with increasing ion fluences as evident from the increase of the peak width in GAXRD pattern. It is also observed that after certain fluence SHIs irradiation, there is a saturation in the nano-grain fragmentation. The track radius and damage cross section are deduced from peak width and area of the dominant diffraction. The track radii are 5.5 and 14.5 nm, 5.0 and 9.7 nm and 5.5 and 6.5 nm for BaF 2 , LiF, CaF 2 , deduced from width and area, respectively. It is noteworthy that the track radius is found to be higher than the previously estimated from sputtering studies of LiF thin films. [ABSTRACT FROM AUTHOR]

In the curing process of fiber-reinforced plastic accumulators, a thermal spike appears due to the exothermic reaction of the resin. It is necessary to accurately evaluate this thermal spike to guarantee quality and avoid using a trial and error approach to control the temperature. Thus, we developed a curing process simulator that is able to accurately evaluate the thermal spike of the thermosetting resin. A simplified mesoscale finite element model with the definite separation of fiber and resin is used in the simulation. In this study, the newly developed simulation system was examined by comparing its results with the experimental results from the curing process of fiber-reinforced plastic accumulators. [ABSTRACT FROM AUTHOR]

Mechanism of solute-enriched clusters formation in neutron-irradiated pressure vessel steels is proposed and developed in case of Fe-Cu model alloys. The suggested solute-drag mechanism is analogous to the well-known zone-refining process. We show that the obtained results are in good agreement with available experimental data on the parameters of clusters enriched with the alloying elements. Our model explains why the formation of solute-enriched clusters does not happen in austenitic stainless steels with fcc lattice structure. It also allows to quantify the method of evaluation of neutron irradiation dose for the process of RPV steels hardening. [ABSTRACT FROM AUTHOR]

AuFe alloy nanoparticles embedded in silica matrix are synthesized using atom beam sputtering technique and subsequently irradiated with 100 MeV Au ions at various fluences ranging from 1 × 10 13 to 6 × 10 13 ions/cm 2 . The X-ray diffraction, absorption spectroscopy, X-ray photo electron spectroscopy and transmission electron microscopy results show that swift heavy ion irradiation leads to decomposition of AuFe alloy nanoparticles from surface region and subsequent reprecipitation of Au and Fe nanoparticles occur. The process of phase decomposition and reprecipitation of individual element nanoparticles is explained on the basis of inelastic thermal spike model. [ABSTRACT FROM AUTHOR]

The generation, detection and measurement of laser-induced carbon plasma ions and their implantation effects on brass substrate have been investigated. Thomson parabola technique was employed to measure the energy and flux of carbon ions. The magnetic field of strength 80 mT was applied on the graphite plasma plume to provide an appropriate trajectory to the generated ions. The energy of carbon ions is 678 KeV for laser fluence of 5.1 J/cm2which was kept constant for all exposures. The flux of ions varies from 32 × 1011to 72 × 1014 ions/cm2for varying numbers of laser pulses from 3000 to 12,000. In order to explore the ion irradiation effects on brass, four brass substrates were irradiated by carbon ions of different flux. Scanning electron microscope (SEM) and X-ray diffractometer (XRD) are used to analyze the surface morphology and crystallographic structure of ion-implanted brass, respectively. SEM analysis reveals the formation and growth of nano-/micro-sized cavities, pores and pits for the various ion flux for varying numbers of laser pulses from 3000 to 12,000. By increasing ion flux by increasing the number of pulses up to 9000 shots, the dendritic structures initiate to grow along with cavities and pores. At the maximum ion flux for 12,000 shots, the unequiaxed dendritic structures become distinct and the distance between the dendrites is decreased, whereas cavities, pores and pits are completely finished. The XRD analysis reveals that a new phase of ZnC (0012) is formed in the brass substrate after ion implantation. Universal tensile testing machine and Vickers microhardness tester are used to explore the yield stress, ultimate tensile strength and microhardness of ion-implanted brass substrate. The mechanical properties monotonically increase by increasing the ion flux. Variations in mechanical properties are correlated with surface and structural modifications of brass. [ABSTRACT FROM PUBLISHER]

A simple radiation-damage model based on the Ising model for magnets is proposed to study the effects of radiation on the magnetism of permanent magnets. The model is studied in two dimensions using a Monte Carlo simulation, and it accounts for the radiation through the introduction of a localized heat pulse. The model exhibits qualitative agreement with experimental results, and it clearly elucidates the role that the coercivity and the radiation particle’s energy play in the process. A more quantitative agreement with experiment will entail accounting for the long-range dipole–dipole interactions and the crystalline anisotropy. [ABSTRACT FROM AUTHOR]

Ion induced R e track radii are derived from a universal relation Θ( r ) without involving any materials parameter apart from the melting point T m . The effect is related to the formation of identical ion-induced temperature distributions in track forming insulators for 〈 s e 〉 = S e / N = constant, where S e , and N are the electronic stopping power and the atomic density. Based on Θ( r ), an R e 2 - 〈 s e 〉 / ( T m - T ir ) plot is applied where the experimental curves coincide for various insulators without adjustable parameters ( T ir – temperature of irradiation). The analysis extends to all track-forming insulators studied up until now. The application of the equilibrium value of T m is justified in thermal spike calculations. The physical meaning of the condition 〈 s e 〉 = S e / N = constant is discussed. Θ( r ) may be valid in those insulators as well in which tracks are not induced. The Fourier equation is not valid under spike conditions. [ABSTRACT FROM AUTHOR]