E-beam Research Articles

Defects evolution in n-type 4H-SiC induced by electron irradiation and annealing

Radiation damage produced in 4H-SiC by electrons of different doses is presented by using multiple characterization techniques. Raman spectra results indicate that SiC crystal structures are essentially impervious to 10 MeV electron irradiation with doses up to 3000 kGy. However, irradiation indeed leads to the generation of various defects, which are evaluated through photoluminescence (PL) and deep level transient spectroscopy (DLTS). The PL spectra feature a prominent broad band centered at 500 nm, accompanied by several smaller peaks ranging from 660 to 808 nm. The intensity of each PL peak demonstrates a linear correlation with the irradiation dose, indicating a proportional increase in defect concentration during irradiation. The DLTS spectra reveal several thermally unstable and stable defects that exhibit similarities at low irradiation doses. Notably, after irradiating at the higher dose of 1000 kGy, a new stable defect labeled as R 2 (Ec − 0.51 eV) appeared after annealing at 800 K. Furthermore, the impact of irradiation-induced defects on SiC junction barrier Schottky diodes is discussed. It is observed that high-dose electron irradiation converts SiC n-epilayers to semi-insulating layers. However, subjecting the samples to a temperature of only 800 K results in a significant reduction in resistance due to the annealing out of unstable defects.

Kinetics of Carrier Lifetime Degradation in High‐Temperature 1 MeV Electron‐Irradiated Cz n‐Si Associated with the Formation of Divacancy‐Oxygen Defects

Kinetics of degradation of the nonequilibrium charge carrier lifetime (τ) in Czochralski‐grown (Cz) n‐Si irradiated with 1 MeV electrons at different temperatures in the range from 20 to 285 °C are experimentally and theoretically investigated. It is established that changes in τ are qualitatively and quantitatively determined by the temperature of electron irradiation. Analysis of experimental data using the Shockley‐Read‐Hall (SRH) theory shows that the formation of recombinationally active divacancy‐oxygen (V2O) and vacancy‐oxygen (VO) complexes is the main mechanism of τ degradation in this experiment.

The Effect of Long-Term Electron Irradiation on Trap Distribution Characteristics of Polyimide

The Effect of Long-Term Electron Irradiation on Trap Distribution Characteristics of Polyimide

CHARACTERISTICS OF ENDOCRINE COMPONENT OF PANCREAS AFTER ADMINISTRATION OF N-ACETYLCYSTEINE IN THE MODEL OF ACUTE RADIATION-INDUCED PANCREATITIS

Studies of radiation-induced pancreatic lesions after irradiation with charged particles (electrons, protons) are rare. The effectiveness of certain antioxidants to reduce pancreatic radiation-induced damage is proved. However, the mechanisms of radiation-induced pancreatic damage have not been fully disclosed, and studies of its endocrine component after electron irradiation are rare. The aim of the paper is to assess insulin and glucagon expression in pancreatic islets after administration of N-acetylcysteine in the model of acute post-radiation pancreatitis. Materials and Methods. Wistar rats (Rattus Wistar; n=60) were divided into four experimental groups: Group 1 (n=10) – control; Group 2 (n=20) – fractional local electron irradiation; Group 3 (n=20) – N-acetylcysteine before electron irradiation; Group 4 (n=10) – N-acetylcysteine. All animals were removed from the experiment a week after the last fraction. Pancreatic fragments were prepared for morphological and immunohistochemical (with insulin and glucagon antibodies) studies. Analysis of variance was used for comparison. Statistical analysis of the obtained data was performed according to the Kruskal–Wallis test and a Bonferroni-corrected Mann-Whitney U test. Results. In an immunohistochemical study, a week after electron irradiation (total radiation dosage – 25 Gy), decreased expression levels of insulin (2 points) and glucagon (1 point) were observed compared with the control group. In the group of pre-irradiation administration of N-acetylcysteine, a week after electron irradiation, the number of immunopositive insulocytes (2–3 points) and glucagonocytes (2 points) was close to control values. Conclusion. Seven-day local irradiation with electrons (total radiation dosage – 25 Gy) leads to a decrease in the endocrine activity of insulocytes and glucagonocytes, which is partially preserved after pre-irradiation administration of N-acetylcysteine, indicating its protective effect.

High-brightness betatron emission from the interaction of a sub picosecond laser pulse with pre-ionized low-density polymer foam for ICF research

Direct laser acceleration (DLA) of electrons in plasmas of near-critical density (NCD) is a very advancing platform for high-energy PW-class lasers of moderate relativistic intensity supporting Inertial Confinement Fusion research. Experiments conducted at the PHELIX sub-PW Nd:glass laser demonstrated application-promising characteristics of DLA-based radiation and particle sources, such as ultra-high number, high directionality and high conversion efficiency. In this context, the bright synchrotron-like (betatron) radiation of DLA electrons, which arises from the interaction of a sub-ps PHELIX laser pulse with an intensity of 1019 W/cm2 with pre-ionized low-density polymer foam, was studied. The experimental results show that the betatron radiation produced by DLA electrons in NCD plasma is well directed with a half-angle of 100–200 mrad, yielding (3.4 ± 0.4)·1010 photons/keV/sr at 10 keV photon energy. The experimental photon fluence and the brilliance agree well with the particle-in-cell simulations. These results pave the way for innovative applications of the DLA regime using low-density pre-ionized foams in high energy density research.

Dosimetric studies of e-, γ-, n- Irradiation fields of the M-30 microtron (18.5 mev)

The results of the implementation and study of the radiation characteristics of high-energy electron (e-), gamma (γ-), and neutron (n-) radiation fields of the M-30 microtron with a maximum energy of 18.5 MeV are presented. Dosimetric characteristics were studied using the method of thermally stimulated luminescence (TSL) and using samples TLD-100H (LiF: Mg,Cu,P) and TLD-500K (Al2O3:C). Three e-, γ-, and n-experiments were performed at the same M-30 electron flux; the dosimetric indicators Yγ,n;e = Dγ,n/De, where Dγ,n is the intensity of the dosimetric peaks of TSL after γ- or n-irradiation, and De is, respectively, e-irradiation. We discuss the relative stability of these dosimeters' Yγ,e parameters at gamma irradiations and the presence of a partial correlation of Yn,e values in neutron fields. The latter is associated with the peculiarity of radiation defect formation in the material of dosimeters when interacting with nuclear particles of different types. The research results confirm the general ideas about the physics of electron radiation conversion into beams of nuclear particles of different natures. The data obtained are important in developing methods for dosimetric support of radiation technologies that use beams of mixed high-energy nuclear radiation, particularly for radiation therapy.

Defects analysis of radiation damage mechanism for IMM triple-junction solar cell under 1 MeV electron irradiation

Inverted metamorphic (IMM) GaInP/GaAs/InGaAs rigid triple-junction solar cells under 1 MeV electron irradiation at various fluences were investigated theoretically. By fitting the electrical and optical parameters of solar cells with experimental results at the fluence ranging from 1 × 1014 e cm−2 to 1 × 1015 e cm−2, basic trap information was obtained, and then the minority carrier lifetime and trap concentration of sub-cells at various fluences were also calculated. The defects analysis of IMM triple-junction solar cell presented in this work could help understanding the radiation damage mechanism of 1 MeV electron irradiation.

Accelerated Electron Ionization-Induced Changes in the Myenteric Plexus of the Rat Stomach.

The influence of accelerated electrons on neuronal structures is scarcely explored compared to gamma and X-rays. This study aims to investigate the effects of accelerated electron radiation on some pivotal neurotransmitter circuits (cholinergic and serotonergic) of rats' myenteric plexus. Male Wistar rats were irradiated with an electron beam (9 MeV, 5 Gy) generated by a multimodality linear accelerator. The contractile activity of isolated smooth muscle samples from the gastric corpus was measured. Furthermore, an electrical stimulation (200 μs, 20 Hz, 50 s, 60 V) was performed on the samples and an assessment of the cholinergic and serotonergic circuits was made. Five days after irradiation, the recorded mechanical responses were biphasic-contraction/relaxation in controls and contraction/contraction in irradiated samples. The nature of the contractile phase of control samples was cholinergic with serotonin involvement. The relaxation phase involved ACh-induced nitric oxide release from gastric neurons. There was a significant increase in serotonergic involvement during the first and second contractile phases of the irradiated samples, along with a diminished role of acetylcholine in the first phase. This study demonstrates an increased involvement of serotonergic neurotransmitter circuits in the gastric myenteric plexus caused by radiation with accelerated electrons.

Emission of quasi-monochromatic ultrasoft X-ray of multilayer target in the Bragg direction under 5.7 MeV electron irradiation

Previously, it was experimentally shown that VUV radiation generated in a periodic structure of a multilayer X-ray mirror by relativistic electrons exhibits a quasi-monochromatic spectrum depending on the angle of inclination of the target and the direction of emission of radiation inside the radiation cone. Here, we present new experimental results regarding the properties of angular density of radiation. A comparison between the measured radiation intensity over a wide range of target inclination angles and theoretical calculations is provided.

Morphological aspects of small intestinal mucosal injury and repair after electron irradiation.

Morphological evaluation of the small intestine mucosa and apoptosis activity (caspase-3) is necessary to assess the severity of damage to the small intestine. At the same time, proliferative index based on Ki-67 can be used to assess the regenerative potential of the small intestine. Fragments of small intestine of Wistar rats (n=60) of three groups: I) control (n=20); II) experimental group (n=20; local single electron irradiation at a dose of 2 Gy), III) experimental group (n=20; local single electron irradiation at a dose of 8 Gy) were studied by light microscopy using hematoxylin and eosin staining and immunohistochemical reactions with antibodies to Ki-67 and caspase-3. In all samples of the experimental groups, a decrease in all morphometric indices was observed on day 1 with a tendency to recover on day 3. Small intestinal electron irradiation led to disturbances in the histoarchitecture of varying severity, and an increase in cell apoptosis was observed (increased expression of caspase-3 and decrease in Ki-67). In addition, modulation of the PI3K/AKT and MAPK/ERK signaling pathways was detected. The most pronounced destructive changes were observed in the group of 8 Gy single electron irradiation. Local irradiation of the small intestine with electrons at a dose of 2 and 8 Gy results in a decrease in the number of enterocytes, mainly stem cells of the intestinal crypts.

H-BN layered material: A new frontier in radiation dosimetry

This study explores the potential of hexagonal boron nitride (h-BN) nanostructures for dosimetry of diverse ionizing radiation. We focus on the crucial thermoluminescence (TL) properties of h-BN, including glow curve, dose-response, reproducibility, sensitivity, and fading, within the conventional framework of TL dosimetry. The h-BN powder samples were exposed to different ionizing radiations, including 60Co gamma-rays with a mean energy of 1.25 MeV, electrons (6 MeV), and photons (6 MV), at levels of dose familiar in radiotherapy ranging from 2 Gy to 15 Gy. The h-BN's effective atomic number of 6.25, similar to human tissue, opens up exciting possibilities for applications in medical imaging and dosimetry. Notably, h-BN demonstrates a linear response within the dose range of interest, showcasing excellent sensitivity, particularly at low doses and low photon energies. Additionally, h-BN samples exhibit remarkable reproducibility, with a standard deviation of less than 2.4%, albeit accompanied by significant fading. Regarding the trapping parameters underpinning the manifestation of the glow curves of the irradiated samples, use was made of the peak shape method with different models to estimate the order of kinetics (b), activation energy (E), and frequency factor (s) or escape probability and trap lifetime (τ). The data suggest that the TL glow peaks of the h-BN obey general-order kinetics. These findings underscore the transformative potential of h-BN layered material in advancing radiation dosimetry, particularly in medical physics fields. The inherent characteristics of h-BN, coupled with its effective atomic number, excellent linearity over a wide range of radiation doses especially for electron irradiation and better reproducibility, positioned it as a suitable tool for precise and reliable dose measurement in medical imaging and therapy, heralding a new frontier in radiation dosimetry.

Ordering of oxygen vacancies in hydroxyapatite under electron irradiation

Understanding the mechanisms of radiation induced defect generation is essential for assessment of materials to be used in nuclear environments. In the current work, we investigate the effect of 10 MeV electron irradiation on the generation and possible ordering of defects/oxygen vacancies in hydroxyapatite (HAP) powders. Comprehensive analyses of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Electron Paramagnetic Resonance (EPR) and Raman spectra establish that (a) HAP has a high level of structural stability even after exposure to electron irradiation; (b) irradiation leads to the generation of surface defects/oxygen vacancy predominantly in the PO43− polyanion site, particularly in part of asymmetric bonding within the P–O bonds and (c) there is noticeable evidence for an ordered arrangement of oxygen vacancies within the HAP irradiated at 1 MGy dose. These radiation-induced defects, such as oxygen vacancies, can migrate within the HAP lattice, leading to formation of defect/oxygen vacancies clusters which ultimately results in the ordering tendency of oxygen vacancies within the lattice. The observed ordering, as evidenced by the photoluminescence intensities, aligns with the sequence HAP-1MGy > HAP-20MGy > HAP, providing further support for the presence of ordered oxygen vacancies.

Exploring electron energy dependencies in the formation of surface charge on ZnO crystals

This study delves into the phenomena surrounding the emergence of negative charge accumulation on the surface of zinc oxide (ZnO) crystals upon exposure to low-energy electron irradiation within the range of E = 0 ÷ 600 eV. We demonstrate the critical significance of the primary electron energy in dictating the initial processes initiated at the ZnO surface. Energy thresholds governing both the genesis and elimination of surface charge, along with the formation of oxygen vacancies on the ZnO surface, are elucidated. Our findings reveal that irradiation instigates distinct dissociative pathways contingent upon electron energy, engendering diverse physical and chemical transformations via bond dissociation, desorption, and atomic and molecular restructuring of the surface. These insights serve as pivotal groundwork towards advancing the fabrication of epitaxial films, facilitating the controlled generation of two-dimensional structures predicated on surface potential modulation.

MgGa2O4-based thermal control coating: An ultra-low solar absorption coating with high irradiation stability

In this study, the viability of MgGa2O4 as a pigment for thermal control coatings is discussed. Notably, the MgGa2O4 based coating exhibited excellent initial optical properties and irradiation stability. After irradiation with 40 keV proton at a dose of 1.4 × 1014 P/cm2, the optical performance of the coating remained essentially unchanged, while the solar absorption of the coating is still maintained below 0.10 after irradiation with 40 keV electron at a dose of 1.6 × 1016 e/cm2. Further, the mechanism of the optical changes induced by electron irradiation was elucidated through experimental and computational methods. In MgGa2O4 lattice, two different types of oxygen vacancies and a transition process of them were found. This process was accompanied by the leakage of some oxygen atoms from the lattice, leading to an increased number of color centers and the change in optical properties. Despite the solar absorption raised after electron irradiation, the MgGa2O4 based thermal control coating showed minimal change and low end-of-irradiation-life values, which suggests that they have excellent stability and promising applications.

In-situ imaging of heat-induced phase transition in a two-dimensional conjugated metal-organic framework

Atomically-resolved in-situ high-resolution transmission electron microscopy (HRTEM) imaging of the structural dynamics in organic materials remains a major challenge. This difficulty persists even with aberration-corrected instruments, as HRTEM images necessitate a high electron dose that is generally intolerable for organic materials. In this study, we report the in-situ HRTEM imaging of heat-induced structural dynamics in a benzenehexathiol-based two-dimensional conjugated metal-organic framework (2D c-MOF, i.e., Cu3(BHT)). Leveraging its hydrogen-free structure and high electrical conductivity, Cu3(BHT) exhibits high electron beam resistance. We demonstrate atomic resolution imaging at an 80 kV electron accelerating voltage using our Cc/Cs-corrected SALVE instrument. However, continuous electron irradiation eventually leads to its amorphization. Intriguingly, under heating in a MEMS holder, the Cu3(BHT) undergoes a phase transition to a new crystalline phase and its phase transition, occurring within the temperature range of 480 °C to 620 °C in dependence on the electron beam illumination. Using HRTEM and energy-dispersive X-ray mapping, we identify this new phase as CuS. Our findings provide insights into the mechanisms governing structural transitions in purposefully engineered structures, potentially pivotal for future endeavours involving the production of metal oxide/sulfide nanoparticles from MOF precursors.

Influence of electron irradiation on the band gap and microhardness of TlInS2, TlInSSe and TlIn0.99Cr0.01S2 single crystals

ABSTRACT This work investigated the effect of partial replacement of sulphur atoms with selenium atoms (TlInSSe) and indium atoms with chromium atoms (TlIn0.99Cr0.01S2) on the band gap and microhardness of TlInS2 single crystals irradiated with electrons with energy of 2 MeV and a fluence of up to 1.5 × 1017 el/cm2. The band gap from the measured absorption spectra was determined using the Tauc method. It has been established that this irradiation leads to a decrease in the band gap in TlInS2, TlInSSe and TlIn0.99Cr0.01S2 crystals. It has been shown that after electron irradiation the microhardness of these crystals increased due to an increase in the size of crystallites on their surface.

Extension of the scope of the photoluminescence method after electron irradiation for quantifying low-level carbon in silicon

We have extended the applicability of the photoluminescence method after electron irradiation for quantifying low-level C impurities in Si crystals. The intensity ratio of the G-line to the intrinsic emission normalized by the ratio of the reference sample is used as an index of the C concentration. The calibration curves have already been established for Czochralski-grown crystals with resistivity higher than 50 Ω·cm (n-type) and higher than 5 kΩ·cm (p-type). We showed that the method was extendable to the resistivity range down to 30 Ω·cm in n-type samples with the O concentration in the range 1–6 × 1017 cm−3. The extension to float-zone (FZ) crystals was realized by using the theoretical relationship between the C concentration and the G-line intensity ratio normalized by the ratio of the FZ reference sample. Regarding the extension to conductive p-type B-doped samples, the formation of B-related radiation-induced defects was found to be an obstacle.

The effect of medium doses electron irradiation on the scattering of charge carriers in YBa2Cu3O7-δ single crystal

The influence of electron irradiation with energies of 0.5–2.5 MeV with fluences up to 70 × 1018 cm–2 on the electrical resistivity in the basal plane of YBa2Cu3O7–δ single crystals in the temperature range from the superconducting transition, Tc, to 300 K has been studied. Such irradiation leads to the appearance of a significant number of defects that cause a decrease in anisotropy, an appreciable increase in phonon scattering, reduction of Tc, and broadening of the superconducting transition. Under the conditions specified, the temperature dependence of electrical resistivity is approximated with high accuracy by the charge carriers’ scattering on defects and phonons, and fluctuating conductivity in the Lawrence-Doniach (LD) model. The dependences of approximation parameters on fluence are discussed.

Development of silicon-on-insulator direct electron detector with analog memories in pixels for sub-microsecond imaging.

We have developed a high-speed recordable direct electron detector based on silicon-on-insulator technology. The detector has sixteen analog memories in each pixel to record sixteen images with sub-microsecond temporal resolution. A dedicated data acquisition system has also been developed to display and record the results on a personal computer. The performance of the direct electron detector as an image sensor is evaluated under electron irradiation with an energy of 30 keV in a low-voltage transmission electron microscope equipped with a photocathode electron gun. We demonstrate that the detector can record images at an exposure time of 100 ns and an interval of 900 ns.

Liquid dosimeter with sensitivity in low-kGy range for the characterization of a new module for EB wastewater treatment

Abstract In recent years, the use of low-energy electrons in various ecological and biotechnological applications has become increasingly relevant. One important application is the treatment of wastewater, wherein highly reactive species produced by water irradiation are used to oxidize pollutants. Low-energy electron irradiation has several advantages, such as minimal demands on radiation protection and electron beam (EB) source dimensions. However, to play into the main advantages of this technology and keep it economically viable, it is necessary to keep the absorbed dose as low as possible. This calls for a liquid dosimeter with sensitivity in the single digit kGy range. An extract from natural Hibiscus sabdariffa (Roselle) has been reported to show a radiochromic effect in this dose range. In the present work, Roselle dosimeter solutions were closely investigated and optimized to characterize a new module for EB wastewater treatment. Upon EB irradiation, the dosimeter solution demonstrated a dose-dependent fading in color, making it useful in the 0.3–7.5 kGy dose range.