Heavy Irradiation Research Articles

Electronic structure engineering of 2-D MoS2 sputtered thin films under ion beam irradiation: Induced by controlled defect generation

TMDs (Transition-metal dichalcogenides) come out in contemporary years as a remarkable class of two-dimensional (2D) materials and have allured enormous consideration. In the class of TMD materials, Molybdenum disulfide (MoS 2 ) has unveiled encouraging applications in the domain of photonics, electronics, electrochemistry and energy. Specifically, the defects originated in MoS 2 play a significant role in modifying the magnetic, electronic, catalytic and optical peculiarities of MoS 2 , depicting an applicable way in modifying the efficiency of MoS 2 based devices. The course through which lattice defects influence the MoS 2 peculiarities are unresolved. In the present work, we present comprehensively how lattice defects impact the electronic structure of MoS 2. We have probed the prospect to employ swift heavy ion irradiation for nano-structuring of sputtered 2D MoS 2 thin films. Our extensive study of ion instigated structural, optical and morphological alterations in MoS 2 thin films manifests that resting on the parameters of irradiation profusion of defects can be established. Theoretically, the optical bandgap also has been determined using Density functional theory (DFT). We grow the thin films of MoS 2 by the sputtering method and induced the defect in MoS 2 thin films by ion irradiation. We evaluated how these defects impact the electronic structure of MoS 2 thin films by measurements taken from Raman, X-ray photoelectron spectroscopy (XPS), photoluminescence spectroscopy (PL), UV–visible spectroscopy, Atomic force microscopy (AFM), X-ray diffraction (XRD) and Rutherford backscattering spectroscopy (RBS).

Integrated high-throughput research in extreme environments targeted toward nuclear structural materials discovery

Arguably one of the most important factors in the fast deployment of advanced nuclear reactors, with major improvements in safety, is the development and qualification of radiation and corrosion tolerant materials, that serve as the structural components in reactor cores. However, the discovery, improvement, and assessment of materials resistant to radiation and corrosion in the advanced reactors’ extreme environments is quite demanding, time-consuming, and costly, which represents a significant barrier to materials innovation and qualification for nuclear energy. This short review highlights a novel, integrated, high-throughput (HTP) research framework to develop understanding and predictive models for irradiation at high doses and molten salt corrosion responses of structural Compositionally Complex Alloys (CCAs), with the objective to accelerate materials discovery for high-temperature nuclear structural applications. Using a novel in situ alloying technique, arrays of additively manufactured bulk CCAs are processed, heat-treated, and characterized, while still attached to the build plate. Leveraging recent development in automation of heavy-ion irradiation experiments at the University of Wisconsin Ion Beam Laboratory, arrays of CCAs can be rapidly irradiated to hundreds of dpa up to 800 °C. An innovative droplet corrosion method is also used to test molten salt corrosion behavior of CCAs arrays. Automated and rapid characterization methods are used to assess the irradiation and molten salt corrosion resistance of CCAs. Finally, a brief discussion of the results is presented considering future use of machine-learning-based methods to develop useful trends and highlight features of importance. Using this novel HTP approach, a robust and reliable database containing literally hundreds of data points for irradiation and corrosion responses of CCAs can be established within a year, which is considered a significant increase in the pace of nuclear structural materials research and discovery.

Characterization of single-event transients induced by high LET heavy ions in 16 nm bulk FinFET inverter chains

Single-event transient (SET) distributions and cross-sections are characterized for 16 nm bulk FinFET inverters with different threshold voltages and driving strengths using the heavy ion 181Ta with the energy of 1.07GeV and the Linear Energy Transfer (LET) of 85 MeV·cm2/mg. Lower threshold voltage makes shorter SET pulses and smaller cross-section, and reduces the upper limit of the SET pulse width, which is advantageous to harden the FinFET gates against the high LET heavy ion irradiation. Enhancing the driving strength changes the layout topology, leading to complicated impact on the radiation sensitivity for FinFET inverters. The source region is laid at one side of the drain region in P or N type transistor of the inverter with driving strength X1 (INV1), while there are two source regions at both sides of the drain region in P or N type transistor in the inverter with driving strength X2 (INV2), which makes INV2 is more SET tolerant than INV1. There are interdigitated two drain regions and three source regions in P or N type transistor of the inverter with driving strength X4 (INV4), which expands the sensitive area and cross-section. The test results indicate that the max SET pulse width is approximately proportional to the ratio of sensitive area to driving strength for the FinFET inverters, that is the max SET pulse width of INV4 is between INV1 and INV2.

Chemical reactions in H2O:CO interstellar ice analogues promoted by energetic heavy-ion irradiation

ABSTRACT H2O:CO, at concentrations of (3:2) and (10:1), was condensed on CsI substrate at 15 K and irradiated with 46-MeV 58Ni11 + ion beam. Radiolysis induced by fast heavy ions was analyzed by infrared spectroscopy (FTIR). The formation of nine molecular species: CO2, H2O2, HCOOH, HCO, H2CO, 13CO2, CH3OH, O3, and C3O2 was observed. For both concentrations, carbon dioxide (CO2), formaldehyde (H2CO), formic acid (HCOOH), and hydrogen peroxide (H2O2) are the most abundant products species, and tricarbon dioxide (C3O2) is much less abundant. Precursor destruction cross-sections and formation cross-sections of products are determined. The CO destruction cross-section for the (3:2) concentration is almost five times higher than that of water, while those for the (10:1) concentration are practically the same. Atomic sputtering yields are estimated for the two ice films, the total mass sputtered is approximately 2.5 × 106 u per impact. These results contribute to figure out the chemical pathways of compounds synthesized from the two most abundant organic species (H2O and CO) observed in the ices of grain mantles of the circumstellar envelopes and interstellar medium. In additional, the finding results reveal that molecular astronomical percentages are comparable to those obtained after 15 eV molec−1 of deposited dose in current experiments compared with the relative concentration of molecules in solid phase observed in MYSO, LYSO, BG Stars, and Comets.

Evaluation of the Saline-Alkaline Tolerance of Rice (Oryza sativa L.) Mutants Induced by Heavy-Ion Beam Mutagenesis.

Simple SummarySoil salinization is one of the important obstacles restricting agricultural development. Cultivating new varieties of saline–alkaline-tolerant rice can increase the yield of rice. It is possible to minimize breeding costs and shorten the breeding period through heavy ion beam irradiation mutation breeding. Our research evaluated and screened saline–alkaline-tolerant rice mutants induced by heavy ion beams. The results show that heavy ion beam radiation is an effective method for breeding new saline–alkaline-tolerant rice cultivars, and the selected mutant lines have excellent production performance under saline–alkaline stress. Our research results provide new theoretical and practical insights that can be used to help develop new saline–alkaline-tolerant rice cultivars.Soil salinity is a widespread and important abiotic factor impeding rice production by adversely affecting seed germination, seedling growth, and plant productivity. In this study, the rice cultivar TH899 was treated with 200 Gy of heavy-ion beam irradiation, and 89 mutant lines with stable phenotypes were selected using the pedigree method based on continuous assessment over six years. The seed germination performance of these mutants was tested under different saline–alkaline concentrations. Five highly tolerant lines were further evaluated in a series of experiments at the seedling stage and in the field. During the seedling stage, the reduction of seedling length, root length, fresh weight, and dry weight were dramatically lower in these five mutants than those in TH899 under saline–alkali stress. The K+/Na+ ratio was higher in these five mutants than in TH899. In the field experiment, the grain yield of mutant lines was higher than that of TH899. In addition, the grain yield of mutant line M89 was higher than that of the local cultivar in actual production. These mutant lines are expected to increase grain yield in soda saline–alkaline regions in northeast China.

200 MeV Ag ion irradiation mediated green synthesis and self assembly of silver nanoparticles into dendrites for enhanced SERS applications

In this paper, we report green and controlled synthesis of silver nanoparticles in water with spherical, hetrogeneously shaped and extended chain like networks using pristine Bergenia ciliata root extracts and the extracts irradiated with Ag15+ swift heavy ion irradiation. The ion fluence on the thin layer of extract modifies the phytomolecules responsible for the reduction and capping of the silver ion and thus changing the morphologies and sizes of the resultant nanoparticles. In addition, the irradiation assists the nanoparticles to agglomerate via surface oxidation providing a core for the growth of dendritic assemblies. Optical, crystallographic and morphological studies reveal surface oxidation of silver nanoparticles is enhanced upon the irradiation of the phytomolecules due to which the surface chemistry of the nanoparticles changes. In addition, these silver nanoparticles and their dendritic assembly exhibit high SERS enhancement factors for methylene blue analyte. The effects of irradiation promote the dendritic assemblies, roughened surfaces over the nanoparticle clusters and hence offer higher enhancement factors as compared to those which have been synthesized using pristine plant extracts.

Synergistically enhanced interface stability by graphene assisted copper surface reconstruction

Graphene (Gr)/Copper (Cu) composites have shown great potential in thermal-management and information-transport applications. The influences of interface related characteristics, such as orientation, adhesion energy and localized strain are of great importance, however, rarely reported. In this work, by conducting heavy ions irradiation and thermal boundary conductance characterization (by time-domain thermoreflectance technique), we examined the intrinsic relationship between microstructural characteristics and interface stability of various Gr/Cu interfaces, such as Gr/{100} Cu, Gr/{111} Cu, and Gr/{111}/{100} Cu. Here we report: (1) compared to Gr/{111} Cu interfaces, Gr/{100} Cu interfaces exhibit higher defect sink capability, and (2) Gr/{111}/{100} Cu interfaces possess both high defect sink capability and good interface stability. Our atomistic simulations suggest higher interface volumetric stress of Gr/{100} Cu interface. The synergistic enhancement of Gr/{111} Cu and {111}/{100} Cu interfaces is attributed to coherent interface generated by Gr assisted Cu surface reconstruction. The present findings may provide more insight to understand the interface characteristics-stability relation of carbon/metal composites.

Characterisation of silicon oxynitride thin films and their response to swift heavy-ion irradiation

Silicon oxynitrides (a-SiO x N y ) are materials whose composition ranges between two binary materials: a-SiO2 and a-Si3N4. In this work, we present a systematic study of the fine structure of the damaged regions produced by swift heavy-ions (SHIs), or ‘ion-tracks’ and quantify the density variation profiles with respect to composition. Thin films were deposited by plasma-enhanced chemical vapor deposition (CVD), where thickness, density, stoichiometry and bond configuration were initially determined. The fine structure and radial size of the ion tracks was determined using small angle x-ray scattering. The tracks exhibit a core–shell cylindrical geometry, with an under-dense core surrounded by an over-dense shell with a smooth transition between the two regions. We observed two trends with composition: a constant increasing ion track radius is observed when the O/Si ratio is below one (. And saturation of the radial dimensions above this value, being similar to a-SiO2. The IR spectra allowed to quantify the bond configuration and its evolution with fluence. After irradiation, the energy deposited by the SHI irradiation leads to a preferential damage of Si–N bonds. IR spectroscopy also showed the formation of new Si–H bonds with increasing fluences and resulting in a rather complex ion-induced structural modification of the a-SiO x N y network.

A 15 V-Tolerant and Radiation-Hardened MOSFET Driver With Positive and Negative References

Radiation-hardened and high-voltage power circuits are key components in aerospace applications. However, when working at high voltages, the effects of the total ionizing dose (TID) and the single event limit the application of power driving circuits in a radiation environment. A 15 V-tolerant radiation-hardened MOSFET driver was designed. The circuit architecture, which is based on positive and negative references, can reduce the gate source voltage of the transistors to less than 5&#x00A0;V, allowing the selection of thin-gate oxide high-voltage transistors. On this basis, adopting enclosed layout transistor (ELT) N-channel metal oxide semiconductor (NMOS) transistors helps the driver to obtain a good resilience to TID hardness. Additionally, this work optimized the layout of high-voltage N-type laterally diffused metal oxide semiconductor (LDMOS) transistors in the driver to effectively improve the single-event burnout (SEB) threshold. Three chips with different N-type drift region lengths were designed and fabricated in a 0.35&#x00A0;<inline-formula><tex-math notation="LaTeX">$\mu m$</tex-math></inline-formula> BCD process. The test results showed that the TID hardening capability of these chips with ZENER references and ELT NMOS transistors all exceeded 100 krad (Si). In addition, this driver was tested under heavy ion irradiation with linear energy transfer (LET) exceeding 75 MeV&#x00B7;<inline-formula><tex-math notation="LaTeX">$\dot\mathrm{{c}}{\mathrm{{m}}^{2}}\mathrm{{/mg}}$</tex-math></inline-formula>. The results show that this driver with a 6.6&#x00A0;<inline-formula><tex-math notation="LaTeX">$\mu m$</tex-math></inline-formula> drift region length had no single event latchup (SEL), single event gate rupture (SEGR), or single event burnout (SEB) sensitivity.

Latent track formation and recrystallization in swift heavy ion irradiation.

Swift heavy ions (SHI) irradiation is a complex coupled multiphysics phenomenon with applications in studying the effects of fission fragments, nano-patterning, and material modification. However, existing models are oversimplified, e.g., inelastic thermal spike, or complicated with inherent size limitations, e.g., hybrid Monte Carlo molecular dynamic. Here, we present a phase-field inelastic thermal spike (PF-iTS) approach to predict the amorphization, recrystallization, and stress generation in a single-impact SHI scenario. Our model quantitatively predicts the latent track radius, which agrees with experiments. Also, the PF-iTS calculates superheating temperature, stress generation, and recrystallization that cannot be obtained with classical i-TS. The appearance of mean compressive stress at the center of the latent track explains the hillock and void formation in TiO2, showing the importance of mechanical stresses in forming latent tracks during SHI irradiation.

Novel Radiation Hardened SOT-MRAM Read Circuit for Multi-Node Upset Tolerance

The rapid transistor scaling and threshold voltage reduction pose several challenges such as high leakage current and reliability issues. These challenges also make VLSI circuits more susceptible to soft-errors, particularly when subjected to harsh environmental conditions. Hybrid spintronic/CMOS technology has emerged as one of the promising techniques to achieve low leakage power and non-volatility. Moreover, the spintronic memories are inherently resistant to the radiation effects such as heavy-ion irradiation and total ionizing dose. However, its CMOS peripheral circuitry is more susceptible to radiation-induced single-event upset (SEU) and double-node upset (DNU). In this paper, a new radiation-hardened read circuit for SOT magnetic random access memory (MRAM) on 45nm technology has been presented. The proposed circuit is highly resistant to all the probable SEUs and DNUs when compared to the previously reported designs. The results show that it can tolerate 4.5X, 11X, 9X, and 10.5X more critical charge as compared to the cross-coupled CMOS transistor, 11T, 13T, and 11T radiation hardened circuits, respectively. Moreover, the recovery time of the proposed circuit is improved by 20% when compared to cross-coupled CMOS transistor circuits.

Effect of swift heavy silicon ion irradiation on TiO2 thin film prepared by micro arc oxidized technique

Titanium dioxide (TiO2) thin films were fabricated via a micro arc oxidized process and its surface was modified using 100 MeV Swift Heavy Si7+ ion (SHI) irradiation. GIXRD analysis confirmed both the phases of rutile and anatase. Additionally, the analysis showed a gradual decrease in intensity which coincided with a rise in ion fluence at up to 5 × 1012 ions/cm2, whereas; at higher fluence (1 × 1013 ions/cm2), the intensity was enhanced. SEM images showed agglomerated particles in the range 0.1–9 µm for pristine whereas; at higher fluences (1 × 1012 and 1 × 1013 ions/cm2) the particle dimensions reduced to a range within 0.1–3 µm. AFM exhibited uniform agglomerates with reduced particle size in the range 0.1–0.5 µm for fluences>1 × 1012 ions/cm2. Enhancement in reflectance was observed for irradiated samples than what was seen in pristine. Irradiation led to a decrease in band gap to 1.4 eV (1 × 1013 ions/cm2) from 1.8 eV (pristine) due to an increase in the defects’ energy level. Surface wettability, roughness, in vitro bioactivity, and irradiated film attachment to the cells are enhanced. Hence, these analytical results demonstrate that the irradiated film is an excellent implant and would be useful in orthopedic applications.

Performance of 4h-Sic Radiation Detector after High Flux Proton and Fe13+ Heavy Ion Beam Irradiation

Performance of 4h-Sic Radiation Detector after High Flux Proton and Fe13+ Heavy Ion Beam Irradiation

Effects of radical scavengers on nanocomposite Fricke gel for heavy ion beam irradiation

NC-FG (nanocomposite Fricke gel) dosimeter is a 3D dosimeter for heavy ion beam without LET dependence. In this study, we evaluate the effects of silver perchlorate, a radical scavenger, on NC-FG. We find that radiological properties of NC-FG are changed by small amounts of silver perchlorate. Especially, dose response at high LET enhanced.

Heavy Ion Irradiation Induced Modifications in N-Type In2(Te1-Xsex)3 Thin Films and Their Enhanced Thermoelectric Properties

Heavy Ion Irradiation Induced Modifications in N-Type In2(Te1-Xsex)3 Thin Films and Their Enhanced Thermoelectric Properties

SAXS data modelling for the characterisation of ion tracks in polymers.

Here, we present new models to fit small angle X-ray scattering (SAXS) data for the characterization of ion tracks in polymers. Ion tracks in polyethylene terephthalate (PET), polycarbonate (PC), polyimide (PI) and polymethyl methacrylate (PMMA) were created by swift heavy ion irradiation using 197Au and 238U with energies between 185 MeV and 2.0 GeV. Transmission SAXS measurements were performed at the Australian Synchrotron. SAXS data were analysed using two new models that describe the tracks by a cylindrical structure composed of a highly damaged core with a gradual transition to the undamaged material. First, we investigate the 'Soft Cylinder Model', which assumes a smooth function to describe the transition region by a gradual change in density from a core to a matrix. As a simplified and computational less expensive version of the 'Soft Cylinder Model', the 'Core Transition Model' was developed to enable fast fitting. This model assumes a linear increase in density from the core to the matrix. Both models yield superior fits to the experimental SAXS data compared with the often-used simple 'Hard Cylinder Model' assuming a constant density with an abrupt transition.

Damage in InGaN/GaN bilayers upon Xe and Pb swift heavy ion irradiation.

350 nm and 550 nm thick InGaN/GaN bilayers were irradiated with different energies (from ∼82 to ∼38 MeV) of xenon (129Xe) ions and different fluences of 1.2 GeV lead (208Pb) ions, respectively. The radiation effects of the swift heavy ions' (SHIs) bombardment were investigated using Rutherford Backscattering Spectrometry in Channeling mode (RBS/C), X-Ray Diffraction (XRD), and micro-Raman spectroscopy. To assess damage profiles, the RBS/C analysis was followed by Monte Carlo simulations using the McChasy code, revealing that InGaN is more susceptible to irradiation damage than GaN. Moreover, the simulations suggest that both randomly displaced atoms (possibly due to partial amorphization) and dislocation loops are formed. The elastic response to radiation was estimated by measuring the expansion of the c-lattice parameter. XRD revealed the presence of strain even in low fluence samples where only a small fraction of the sample volume suffered direct SHI impacts. Micro-Raman suggests that for low defect concentrations, it is dominantly biaxial, while for high defect concentrations, the simultaneous increase of hydrostatic and biaxial occurs. As a driving force of the lattice expansion, we point out the Poisson effect resulting from the pressure exerted by the SHI tracks on the surrounding undamaged crystal structure.

Fabrication, thermal analysis, and heavy ion irradiation resistance of epoxy matrix nanocomposites loaded with silane-functionalized ceria nanoparticles

This paper describes a detailed understanding of how nanofillers function as radiation barriers within the polymer matrix, and how their effectiveness is impacted by factors such as composition, size, loading, surface chemistry, and dispersion. We designed a comprehensive investigation of heavy ion irradiation resistance in epoxy matrix composites loaded with surface-modified ceria nanofillers, utilizing tandem computational and experimental methods to elucidate radiolytic damage processes and relate them to chemical and structural changes observed through thermal analysis, vibrational spectroscopy, and electron microscopy. A detailed mechanistic examination supported by FTIR spectroscopy data identified the bisphenol A moiety as a primary target for degradation reactions. Results of computational modeling by the Stopping Range of Ions in Matter (SRIM) Monte Carlo simulation were in good agreement with damage analysis from surface and cross-sectional SEM imaging. All metrics indicated that ceria nanofillers reduce the damage area in polymer nanocomposites, and that nanofiller loading and homogeneity of dispersion are key to effective damage prevention. The results of this study represent a significant pathway for engineered irradiation tolerance in a diverse array of polymer nanocomposite materials. Numerous areas of materials science can benefit from utilizing this facile and effective method to extend the reliability of polymer materials.

Study of destruction processes of mechanical properties of the near-surface layer of SiC ceramics exposed to heavy ion irradiation

Study of destruction processes of mechanical properties of the near-surface layer of SiC ceramics exposed to heavy ion irradiation

Research on Ion Distribution and Stoping Power for Au Ions Irradiation Si, SiC

In order to predict the effect of heavy ion irradiation more accurately, the ion distribution and stoping power of Au irradiated silicon (Si) and silicon carbide (SiC) under various energy conditions were calculated by using SRIM program, and compared with the experimental values. It was found that the projeced range and divergence predicted by SRIM were significantly smaller, and the stopping power was significantly larger by about 25%. Therefore, the method of reducing the target density parameters was tried to make corrections. It was found that the gold ion distribution became deeper after the density decreased, the stopping power became smaller, and the curve was closer to the experiment with an error of only ~5%. The density reduction coefficient is introduced since there is no definite conclusion on how much density decreases. Based on a large number of previous experimental data, SRIM was used to calculate the density reduction coefficient values under different energy conditions repeatedly, and found that there is a corresponding relationship between the values and energy values. Finally, the polynomial regression fitting method was used to obtain their functional expressions, which laid a foundation for the prediction of Si and SiC irradiated by heavy ions.