Heavy Irradiation Research Articles

Short-range order structural response of CdSe nanocrystals under 120 MeV swift heavy ions irradiation: A pair distribution function analysis

Swift heavy ion (SHI) irradiation deposits large amount of energy in the target material which thereby influences the structural features of the sample. In this work, the structural response of CdSe material has been studied under high energetic 120 MeV SHI irradiation. The long-range structural modifications of CdSe under SHI have been analyzed using Rietveld study. On the other hand, the short-range behavior of SHI irradiated CdSe has been studied using Pair distribution function (PDF), which can be interpreted as a distance map between two atoms in terms of a PDF peak. The small-box structural refinement of the samples has been performed using the PDFgui package for the study of modifications in the atomic arrangement after the SHI irradiation. In addition to this, structural characteristics such as unit cell parameters as determined from long-range (Rietveld) refinement are compared to that obtained from short-range (small-box) refinement. Moreover, atomic displacement factor for CdSe also has been determined to study the atomic disorder in the nanocrystal under the influence SHI irradiation. Finally, impact of SHI induced stress generated on the CdSe sample and its influence also has been studied based on the width of the PDF peak.

Delayed fragmentation of isolated nucleobases induced by MeV ions.

We evaluated the dissociation of isolated gas-phase nucleobase molecules induced by mega electron volt (MeV)-energy ions to gain fundamental insights into the reactions of nucleobases upon fast ion irradiation. We studied five nucleobase molecules-adenine, guanine, cytosine, thymine, and uracil-as gas-phase targets. We compared the fragmentation patterns obtained from carbon ion impacts with those obtained from proton impacts to clarify the effect of heavy ion irradiation. We also compared the results with electron impact and photoionization results. In addition, we identified several delayed fragmentation pathways by analyzing the correlation between fragment pairs generated from singly and doubly charged intermediate ions. To determine the lifetimes of delayed fragmentation from singly charged intermediate ions, we evaluated the detection efficiencies of the microchannel plate detector for the neutral fragment HCN as a function of kinetic energy using a new methodology. As the first demonstration of this method, we estimated the lifetimes of C5H5N5+ generated by 1.2-MeV C+ and 0.5-MeV H+ collisions to be 0.87 ± 0.43 and 0.67 ± 0.09 µs, respectively. These lifetimes were approximately one order of magnitude longer than those of the doubly charged intermediate ion C5H5N52+.

Comparison of Monte Carlo Tools for Displacement Calculations for Protons and Heavy Ions Irradiation on Iron and EUROFER97

Abstract Ion irradiation of structural materials for the current and future generation nuclear reactors is a widespread technique used to simulate neutron irradiation in the context of material science research. During the designing phase of irradiation experiments Monte Carlo transport codes are often employed to quantify the radiation exposure, by estimating the displacements per atom (dpa) quantity. From the available displacement calculation codes, four popular choices were selected: cern-fluka, mcnp, phits, and srim. These codes will be used to simulate the irradiation effects of proton and Fe ions on pure iron (G379) and EUROFER97 alloy (a common material in fusion applications) targets. Results coming from the different software are presented in the form of damage profiles and of number of displacements as a function of the primary beam energy. This study identifies discrepancies between the codes' outputs and provides optimized simulation setup parameters.

Modeling swift heavy ion irradiation of substrate-supported two-dimensional material via two-temperature molecular dynamics simulations

This study employs two-temperature molecular dynamics simulations to investigate swift heavy ion irradiation of SiO2 substrate-supported two-dimensional material graphene. Material-dependent electronic and thermal properties are integrated into each region to model the energy transfer between the electronic and atomic subsystems of the studied materials. Simulations of interactions with Xe heavy ions are performed with ion kinetic energies ranging from 0.5 to 25 GeV with electronic stopping powers from ∼2.6 to 17.7 keV/nm. With the studied ion energy range, nanopores with a diameter of up to 5 nm can be formed in graphene due to the thermally driven sputtering effect, while amorphization occurs along the ion track in the SiO2 substrate. The coupling between the substrate and two-dimensional material significantly impacts the structural change due to heat transfer and atomic interactions among different layers of materials. The method applied in this work provides a valuable tool for modeling and understanding the structural modifications induced by ion irradiation in layered structures.

Influence of annealing treatment on performance of 4H–SiC SBD irradiated by heavy ions under room temperature and low temperature

The influence of the annealing treatment on the performance of commercial 4H–SiC Schottky barrier diodes (SBDs) subjected to heavy ion irradiation under room temperature (RT) and low temperature (LT) are presented. Experimental results confirm that annealing treatment effectively eliminates defects and interface states caused by heavy ion irradiation, particularly for 4H–SiC SBD under LT irradiation. Increasing the annealing temperature leads to the slight improvement in forward current, leakage current and breakdown voltage. However, the annealing process may result in the formation of Ti and Si compounds at the interface between the Schottky metal and SiC, as well as a significant number of vacancies. Combined with Technology Computer Aided Design (TCAD) simulations, it is concluded that the interface trap charge concentrations exceeding 1 × 1012 cm−2 significantly impact the breakdown characteristics of 4H–SiC SBDs.

Synergistic Effects of Total Ionizing Dose and Single-Event Upset in 130 nm 7T Silicon-on-Insulator Static Random Access Memory

The exposure of spaceborne devices to high-energy charged particles in space results in the occurrence of both a total ionizing dose (TID) and the single-event effect (SEE). These phenomena present significant challenges for the reliable operation of spacecraft and satellites. The rapid advancement of semiconductor fabrication processes and the continuous reduction in device feature size have led to an increase in the significance of the synergistic effects of TID and SEE in static random access memory (SRAM). In order to elucidate the involved physical mechanisms, the synergistic effects of TID and single-event upset (SEU) in a new kind of 130 nm 7T silicon-on-insulator (SOI) SRAM were investigated by means of cobalt-60 gamma-ray and heavy ion irradiation experiments. The findings demonstrate that 7T SOI SRAM is capable of maintaining normal reading and writing functionality when subjected to TID irradiation at a total dose of up to 750 krad(Si). In general, the TID was observed to reduce the SEU cross-section of the 7T SOI SRAM. However, the extent of this reduction was influenced by the heavy ion LET value and the specific writing data pattern employed. Based on the available evidence, it can be proposed that TID preirradiation represents a promising avenue for enhancing the resilience of 7T SOI SRAMs to SEU.

Effect of Au ion irradiation on microstructure, mechanical, and lead‐bismuth eutectic corrosion properties of Cr/ZrO2 coatings

AbstractThe effect of ion irradiation on the microstructure, mechanical, and corrosion properties of Cr/ZrO2 coating was investigated. The monoclinic to tetragonal phase transition is observed under heavy ion irradiation, and the tetragonal phase is stabilized by the irradiation‐induced defect clusters. With increasing irradiation fluence, grain growth, and irradiation‐induced hardening effects are observed. After lead‐bismuth eutectic (LBE) corrosion at 650°C for 1000 h, the irradiated coatings can still maintain structural integrity and protect the substrate from lead/bismuth corrosion. However, in contrast to the unirradiated coating, the irradiation‐induced defects provide a channel for the rapid inward diffusion of oxygen atoms from the LBE, leading to the formation of a thicker Cr‐rich oxide layer beneath the ZrO2 coating. This study also provides insight into how irradiation‐induced microstructural changes affect zirconia's properties as a corrosion protection layer.

Unveiling microstructural damage for leakage current degradation in SiC Schottky diode after heavy ions irradiation under 200 V

Single-event burnout and single-event leakage current (SELC) in silicon carbide (SiC) power devices induced by heavy ions severely limit their space application, and the underlying mechanism is still unclear. One fundamental problem is lack of high-resolution characterization of radiation damage in the irradiated SiC power devices, which is a crucial indicator of the related mechanism. In this Letter, high-resolution transmission electron microscopy (TEM) was used to characterize the radiation damage in the 1437.6 MeV 181Ta-irradiated SiC junction barrier Schottky diode under 200 V. The amorphous radiation damage with about 52 nm in diameter and 121 nm in length at the Schottky metal (Ti)–semiconductor (SiC) interface was observed. More importantly, in the damage site the atomic mixing of Ti, Si, and C was identified by electron energy loss spectroscopy and high-angle annular dark-field scanning TEM. It indicates that the melting of the Ti–SiC interface induced by localized Joule's heating is responsible for the amorphization and the possible formation of titanium silicide, titanium carbide, or ternary phases. The mushroom-like hillock in the Ti layer can be attributed to Rayleigh–Taylor instability, as another evidence for ever-happened localized melting near the Schottky interface. These modifications at nanoscale in turn cause localized degradation of the Schottky contact, resulting in permanent increase in leakage current. This experimental study provides very valuable clues for a thorough understanding of the SELC mechanism in SiC diodes.

Au ion irradiation induces ultralow thermal conductivity in GaN

Gallium nitride (GaN) is widely considered as a crucial semiconductor for the nuclear industry and space explorations due to its superior radiation hardness. Despite extensive studies of the electronic and optical properties of irradiated GaN, the effects of particle irradiation on the thermal properties remain largely unexplored. Here, we begin with single-crystalline GaN and employ an accelerator equipped with heavy gold ions (Au2+) as the radiation source in order to imitate extreme environments and maximize lattice damages. Eight different irradiated samples are prepared with the fluence of Au2+ spanning four orders of magnitude from 1011 to 1015 cm−2. The thermal conductivity (κ) of the ion-affected regions is measured using the laser pump–probe technique of frequency-domain thermoreflectance. We find that κ decreased consistently and notably with increasing irradiation fluence and observe a transition from crystal to glass-like thermal transport. Remarkably, the room-temperature κ of the GaN sample with the highest Au2+ fluence of 1 × 1015 cm−2 reaches about 1 Wm−1 K−1, which is two orders of magnitude lower than the κ of pristine GaN and approaches the theoretical minimum. A Callaway-type model captures the phonon–point defect scattering in samples with relatively low ion fluences. At higher fluences, the increased defect types and densities, together with the formation of nitrogen bubbles, further suppress phonon transport. Our findings are instrumental in fundamentally understanding the impact of heavy-ion irradiation on thermal transport and may prove useful for the application of GaN-based devices in radiation-intense environments.

Quantum emitters in aluminum nitride induced by heavy ion irradiation

The integration of solid-state single-photon sources with foundry-compatible photonic platforms is crucial for practical and scalable quantum photonic applications. This study explores aluminum nitride (AlN) as a material with properties highly suitable for integrated on-chip photonics and the ability to host defect-center related single-photon emitters. We have conducted a comprehensive analysis of the creation of single-photon emitters in AlN, utilizing heavy ion irradiation and thermal annealing techniques. Subsequently, we have performed a detailed analysis of their photophysical properties. Guided by theoretical predictions, we assessed the potential of Zirconium (Zr) ions to create optically addressable spin defects and employed Krypton (Kr) ions as an alternative to target lattice defects without inducing chemical doping effects. With a 532 nm excitation wavelength, we found that single-photon emitters induced by ion irradiation were primarily associated with vacancy-type defects in the AlN lattice for both Zr and Kr ions. The density of these emitters increased with ion fluence, and there was an optimal value that resulted in a high density of emitters with low AlN background fluorescence. Under a shorter excitation wavelength of 405 nm, Zr-irradiated AlN exhibited isolated point-like emitters with fluorescence in the spectral range theoretically predicted for spin-defects. However, similar defects emitting in the same spectral range were also observed in AlN irradiated with Kr ions as well as in as-grown AlN with intrinsic defects. This result is supportive of the earlier theoretical predictions, but at the same time highlights the difficulties in identifying the sought-after quantum emitters with interesting properties related to the incorporation of Zr ions into the AlN lattice by fluorescence alone. The results of this study largely contribute to the field of creating quantum emitters in AlN by ion irradiation and direct future studies emphasizing the need for spatially localized Zr implantation and testing for specific spin properties.

Irradiation and Alterations in Hippocampal DNA Methylation.

The response of the brain to radiation is important for cancer patients receiving whole or partial brain irradiation or total body irradiation, those exposed to irradiation as part of a nuclear accident or a nuclear war or terrorism event, and for astronauts during and following space missions. The mechanisms mediating the effects of irradiation on the hippocampus might be associated with alterations in hippocampal DNA methylation. Changes in cytosine methylation involving the addition of a methyl group to cytosine (5 mC) and especially those involving the addition of a hydroxy group to 5 mC (hydroxymethylcytosine or 5 hmC) play a key role in regulating the expression of genes required for hippocampal function. In this review article, we will discuss the effects of radiation on hippocampal DNA methylation and whether these effects are associated with hippocampus-dependent cognitive measures and molecular measures in the hippocampus involved in cognitive measures. We will also discuss whether the radiation-induced changes in hippocampal DNA methylation show an overlap across different doses of heavy ion irradiation and across irradiation with different ions. We will also discuss whether the DNA methylation changes show a tissue-dependent response.

Influence of swift heavy ions irradiation on optical and luminescence properties of Y3Al5O12 single crystals

Optical and luminescence properties of Y3Al5O12 (YAG) single crystals preliminary irradiated by swift heavy ions were studied. Swift heavy Xe ions with fluences ranging from 6·1010 to 2·1012 ions/cm2 were utilized for the irradiation of nominally undoped YAG single crystals. A stable strong induced absorption observed in the 200–600 nm spectral range correlates with the irradiation fluence. It is suggested that several centers are responsible for this induced absorption in YAG single crystals and their possible origin (F-type centers) is proposed and discussed. The swift heavy ions irradiation strongly modifies the luminescence properties of YAG, namely, the excitonic emission at liquid helium temperature is drastically suppressed in heavily irradiated crystals.

Ion Beam-Induced modification in the optical properties of the bilayer of nano-structured amorphous selenium and multi-walled carbon Nanotubes: A study by 70 MeV Ni Ions

In this study, we report improved physical properties of selenium with multi-walled carbon nanotubes (MWCNTs) resulting from a homogeneous mixture of CNT-Se bi-layer thin film by using swift heavy ion irradiation. FESEM micrographs clearly showed the inter-diffusion of Se nanoparticles into MWCNTs following swift heavy ion (SHI) irradiation, EDX validates the elemental composition. The existence of different phonon modes (LO mode and D, G, G' bands) has been found in the Raman spectra of the investigated bi-layer thin films. UV–Visible spectroscopic analysis of pristine CNT-Se thin films show two sharp absorption edges at ∼670 nm and ∼340 nm. After swift heavy ion irradiation, the sharp absorption edge at ∼670 nm exhibits a blue shift, whereas the absorption edge at ∼340 nm exhibits a red shift, confirming the homogeneous mixing of two layers. These remarkable shifts found in the optical properties of CNT-Se bi-layer make the investigated material feasible for many optoelectronic device applications.

Tuning critical current density properties of YBa2Cu3O y thin films under longitudinal magnetic field by using heavy-ion irradiation

We attempted to improve the critical current density J c under a longitudinal magnetic field (LMF) by using columnar defects (CDs) tilted toward the transport current, where the CDs were produced with 80 MeV Xe ions at an incident angle(s) up to φ i = 87.5° relative to the c-axis of YBa2Cu3O y thin films. The formation of CDs extending throughout the film was confirmed by cross-sectional transmission electron microscopy. The CDs tilted at φ i = 87.5° weakened the magnetic field dependence of J c under the LMF, providing a J c higher than that of the unirradiated film in a high magnetic field. This is the first study to demonstrate that CDs and/or irradiation defects contribute to flux pinning under the LMF in high-T c superconductors. In addition, the J c under LMF was sensitive to the tilt angle of the CDs: the J c was reduced by CDs tilted not only at φ i = 0°, but also at a slightly larger angle relative to the ab-plane, i.e. φ i = 85°. The introduction of CDs rather disturbs the LMF effect because of the large volume passing through the film thickness, unless the tilt angles of the CDs are within the narrow angular region effective for the LMF effect.

In-situ TEM investigation of recovery mechanisms in ion-irradiated ITER-grade tungsten

The annealing of irradiation defects in tungsten was investigated under in-situ observations conducted using transmission electron microscopy (TEM). ITER-specification tungsten was exposed to heavy-ion irradiation by 10 MeV Au+ ions to 0.5 and 1 dpa at room temperature to generate defects. Subsequently, the thermal stability and recovery mechanisms of the generated defects are investigated by in-situ TEM at 600 °C, 800 °C, 900 °C and 1000 °C. The obtained TEM data are used to visualize and quantify the defect characteristics such as loops and voids as well as for observing the evolution of the microstructure and defect diffusion/recovery mechanisms. Focus is made on specific spatial phenomena such as loop-loop interaction, loop-dislocation and loop-grain boundary decoration, loop pinning, entanglement, formation of raft and transformation of loops into a dislocation network. The obtained results are in line with earlier obtained data for pure recrystallized tungsten, still, present results provide important information such as radiation-induced defect characteristics and recovery mechanisms under high temperature for the ITER-specification tungsten.

Characterization of Vacancy Defects Using TEM in Heavy-Ion-Irradiated Tungsten Foils

The nature and type of defects formed due to heavy-ion irradiation in tungsten foils are analyzed using transmission electron microscopy. The recrystallized tungsten foils were irradiated by 80 MeV gold ions at room temperature for a fluence of 1.3 ×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes $$\\end{document} 1014\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{14}$$\\end{document} ions/cm2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^2$$\\end{document} that amounts to a net displacement per atom (dpa) of 0.22. The defect structures were analyzed using bright-field and weak-beam dark field imaging at two different depths to understand the depth profile of the defects. It is found that the defect clusters formed during the irradiation, both at the near-surface and at 2 μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mu $$\\end{document}m depth are of vacancy type that is confirmed by the local strain analysis and supports the findings of vacancy clusters in positron lifetime measurements. The analysis also shows that the dislocation-lines were of pure edge, pure screw and mixed. The fraction of mixed dislocation is found to increase during irradiation at the expense of pure edge and screw dislocations.

A Critical Look at Heavy Ion Beam Irradiation for Vaccine Development.

Recent studies offer valuable insights into viral inactivation for vaccine development. Schulze et al. have demonstrated the potential of heavy ion beam irradiation to create effective vaccines, which is particularly relevant in the context of airborne pandemics. Notably, the success in immunizing mice via intranasal administration with the inactivated influenza virus is encouraging, especially given the genetic similarities between influenza and SARS-CoV-2. However, the study raises important considerations. While heavy ion treatment shows advantages, there are concerns about viral inactivation completeness and the potential for surviving viruses, albeit at extremely low levels. Prolonged irradiation times and the risk of selective pressure leading to the evolution of resistant variants are highlighted. Biosafety concerns regarding accidental lab escape of resistant strains are crucial, emphasizing the need for caution during experiments. Moreover, limitations in Monte Carlo simulations of virus irradiation are discussed, pointing out the need for more comprehensive studies to assess the impact of secondary particles on virus inactivation under realistic irradiation conditions. Given these considerations, while the study presents a promising approach for vaccine development, further research is essential to address potential drawbacks and optimize the method for safe and effective application.

Significantly enhanced photo response of hydrazine hydrate reduced graphene oxide films modified with swift heavy ion irradiation of silver (Ag8+) ions

In this paper, a multistep reduction process of graphene oxide (GO) is discussed. It is basically a two-step reduction process. In the first step, the GO sample is reduced by hydrazine hydrate. In the second step, it is further reduced by a swift heavy ion irradiation beam of silver (Ag8+) ions of 100 MeV energies. Ion beam irradiation causes defects in the hydrazine hydrate reduced graphene oxide (rGO) samples. FTIR study confirms the removal of oxygen containing functional groups. The pore volume and pore density of the samples seem to increase with increase in the ion irradiation doses. It is also seen that the electrical conductivity and specific surface area increases with dose of ion irradiation. The prepared samples were tested for photo response measurement and among all the sample, R5 had the highest photo response of 6.25 % at 30 mW/cm2. The photodetection response seems to increase with increase in intensity of light.

The Effect of 147 MeV 84Kr and 24.5 MeV 14N Ions Irradiation on the Optical Absorption, Luminescence, Raman Spectra and Surface of BaFBr Crystals

Today, BaFBr crystals activated by europium ions are used as detectors that store absorbed energy in metastable centers. In these materials, the image created by X-ray irradiation remains stable in the dark for long periods at room temperature. As a result, memory image plates are created, and they are extended to other types of ionizing radiation as well. Despite significant progress towards X-ray storage and readout of information, the mechanisms of these processes have not been fully identified to date, which has hindered the efficiency of this class of phosphors. In this study, using photoluminescence (PL), optical absorption (OA), Raman spectroscopy (RS), and atomic force microscopy (AFM), the luminescence of oxygen vacancy defects to BaFBr crystals irradiated with 147 MeV 84Kr and 24.5 MeV 14N ions at 300 K to fluences (1010–1014) ion/cm2 was investigated. BaFBr crystals were grown by the Shteber method on a special device. Energy-dispersive X-ray spectroscopy (EDX) analysis revealed the presence of Ba, Br, F, and O. The effect of oxygen impurities present in the studied crystals was considered. The analysis of the complex PL band, depending on the fluence and type of ions, showed the formation of three types of oxygen vacancy defects. Macrodefects (tracks) and aggregates significantly influence the luminescence of oxygen vacancy defects. The creation of hillocks and tracks in BaFBr crystals irradiated with 147 MeV 84Kr ions is shown for the first time. Raman spectra analysis confirmed that BaFBr crystals were amorphized by 147 MeV 84Kr ions due to track overlap, in contrast to samples irradiated with 24.5 MeV 14N ions. Raman and absorption spectra demonstrated the formation of hole and electron aggregate centers upon swift heavy ions irradiation.

Evaluation of a Simplified Modeling Approach for SEE Cross-Section Prediction: A Case Study of SEU on 6T SRAM Cells

Electrical models play a crucial role in assessing the radiation sensitivity of devices. However, since they are usually not provided for end users, it is essential to have alternative modeling approaches to optimize circuit design before irradiation tests, and to support the understanding of post-irradiation data. This work proposes a novel simplified methodology to evaluate the single-event effects (SEEs) cross-section. To validate the proposed approach, we consider the 6T SRAM cell a case study in four technological nodes. The modeling considers layout features and the doping profile, presenting ways to estimate unknown parameters. The accuracy and limitations are determined by comparing our simulations with actual experimental data. The results demonstrated a strong correlation with irradiation data, without requiring any fitting of the simulation results or access to process design kit (PDK) data. This proves that our approach is a reliable method for calculating the single-event upset (SEU) cross-section for heavy-ion irradiation.