Electron Irradiation Dose Research Articles

Generation, relaxation and annealing of Si/SiO2 charges induced by low-energy electron beam

Silicon oxide based, aluminum gated MOS structures fabricated on n-type silicon were subjected to a low energy electron beam irradiation in the scanning electron microscope. The induced interface states and the oxide charges were studied by the high frequency capacitance–voltage technique as a function of the electron beam energy, irradiation dose, annealing time, temperature and electric field. Strong initial increase and subsequent saturation of the donor-like interface state density with the irradiation dose was observed for all electron beam energies used. Besides, shallow positively charged traps were found to be formed in the silicon oxide after irradiation, while at the initial stage of irradiation the formation of a negative charge was established. The irradiation induced interface states and the positively charged shallow oxide traps demonstrated notable reduction at room temperature. Zero bias annealing at the temperatures of about 250–300 °C resulted in a complete removal of the interface states and partial compensation or elimination of the oxidation induced positive fixed charge, presumably due to remaining negative charge in oxide.

Determination of chemical and microbiological characteristics of meat products treated by radiation

Radiation treatment of food products carried out to increase their shelf life can result in chemical transformations initiated by free radicals. Volatile compounds (alcohols, aldehydes, ketones, etc.) formed, in particular, as a result of lipid oxidation, impair the organoleptic properties of products. Method of gas chromatography-mass spectrometry (GC-MS) makes it possible to identify the fact of food processing by detection of volatile marker compounds: in the case of meat products, the existing standard brings under regulation detection of 2-alkylcyclobutanones, however, the products with a reduced fat content, such as turkey and chicken, require an alternative marker. The results of GKh-MS study revealed the dependence of microbiological parameters and the content of various volatile organic substances in chilled turkey meat on the dose of electron radiation. It is shown that the total amount of alcohols, ketones and aldehydes (11 compounds) decreases exponentially with an increase in the absorbed dose. An increase in the radiation dose leads to a higher content of carbonyl compounds (aldehydes and acetone), which results in a specific taste and smell of the irradiated products. At the same time, the acetone concentration increases linearly with the absorbed dose, which makes it possible to use acetone as a potential marker of the degree of irradiation of low-fat meat products. Irradiation in the «working» doses (0.5 – 1 kGy) significantly suppresses the pathogenic microflora and keeps the organoleptic properties of the product.

The Structure and Mechanical Properties of Hemp Fibers-Reinforced Poly(ε-Caprolactone) Composites Modified by Electron Beam Irradiation

The need for the development of new biodegradable materials and modification of the properties the current ones possess has essentially increased in recent years. The aim of this study was the comparison of changes occurring in poly(ε-caprolactone) (PCL) due to its modification by high-energy electron beam derived from a linear electron accelerator, as well as the addition of natural fibers in the form of cut hemp fibers. Changes to the fibers structure in the obtained composites and the geometrical surface structure of sample fractures with the use of scanning electron microscopy were investigated. Moreover, the mechanical properties were examined, including tensile strength, elongation at break, flexural modulus and impact strength of the modified PCL. It was found that PCL, modified with hemp fibers and/or electron radiation, exhibited enhanced flexural modulus but the elongation at break and impact strength decreased. Depending on the electron radiation dose and the hemp fibers content, tensile strength decreased or increased. It was also found that hemp fibers caused greater changes to the mechanical properties of PCL than electron radiation. The prepared composites exhibited uniform distribution of the dispersed phase in the polymer matrix and adequate adhesion at the interface between the two components.

Secondary electron yield reduction by femtosecond pulse laser-induced periodic surface structuring

The electron-cloud phenomenon is one cause of beam instabilities in high intensity positive particle accelerators. Among the proposed techniques to mitigate or control this detrimental effect, micro-/nano-geometrical modifications of vacuum chamber surfaces are promising to reduce the number of emitted secondary electrons. Femtosecond laser surface structuring readily allows the fabrication of Laser Induced Periodic Surface Structures (LIPSS) and is utilized in several fields, but has not yet been tested for secondary electron emission reduction. In this study, such treatment is carried out on copper samples using linearly and circularly polarized femtosecond laser pulses. The influence of the formed surface textures on the secondary electron yield (SEY) is studied. We investigate the morphological properties as well as the chemical composition by means of SEM, AFM, Raman and XPS analyses. Surface modification with linearly polarized light is more effective than using circularly polarized light, leading to a significant SEY reduction. Even though the SEY maximum is only reduced to a value of ~1.7 compared to standard laser-induced surface roughening approaches, the femtosecond-LIPSS process enables to limit material ablation as well as the production of undesired dust, and drastically reduces the number of redeposited nanoparticles at the surface, which are detrimental for applications in particle accelerators. Moreover, conditioning tests reveal that LIPSS processed Cu can reach SEY values below unity at electron irradiation doses above 10−3 C/mm2.

B0AT1 Amino Acid Transporter Complexed With SARS-CoV-2 Receptor ACE2 Forms a Heterodimer Functional Unit: In Situ Conformation Using Radiation Inactivation Analysis.

The SARS-CoV-2 receptor, angiotensin-converting enzyme-2 (ACE2), is expressed at levels of greatest magnitude in the small intestine as compared with all other human tissues. Enterocyte ACE2 is coexpressed as the apical membrane trafficking partner obligatory for expression and activity of the B0AT1 sodium-dependent neutral amino acid transporter. These components are assembled as an [ACE2:B0AT1]2 dimer-of-heterodimers quaternary complex that putatively steers SARS-CoV-2 tropism in the gastrointestinal (GI) tract. GI clinical symptomology is reported in about half of COVID-19 patients, and can be accompanied by gut shedding of virion particles. We hypothesized that within this 4-mer structural complex, each [ACE2:B0AT1] heterodimer pair constitutes a physiological “functional unit.” This was confirmed experimentally by employing purified lyophilized enterocyte brush border membrane vesicles exposed to increasing doses of high-energy electron radiation from a 16 MeV linear accelerator. Based on radiation target theory, the results indicated the presence of Na+-dependent neutral amino acid influx transport activity functional unit with target size molecular weight 183.7 ± 16.8 kDa in situ in intact apical membranes. Each thermodynamically stabilized [ACE2:B0AT1] heterodimer functional unit manifests the transport activity within the whole ∼345 kDa [ACE2:B0AT1]2 dimer-of-heterodimers quaternary structural complex. The results are consistent with our prior molecular docking modeling and gut–lung axis approaches to understanding COVID-19. These findings advance understanding the physiology of B0AT1 interaction with ACE2 in the gut, and thereby contribute to translational developments designed to treat or mitigate COVID-19 variant outbreaks and/or GI symptom persistence in long-haul postacute sequelae of SARS-CoV-2.

Research Investigation of Deformation Characteristics of Thin Polymer Films at Different Doses of Electron Irradiation

The study of the deformation characteristics of thin polymer films has established 2 stages of increasing strain with increasing stress: the first stage in the elastic region is slow linear; the second stage is sharply exponential. The dependence of deformation (ε) on stress (σ) in polytetrafluoroethylene at various exposure doses has been experimentally investigated. Irradiation of the fluoroplastic films under study with electrons doses of 1, 3, 5, 7, and 10 kGy leads to significant changes in their mechanical properties, while the samples lose their plasticity and begin to break at a lower strain, which is associated with the formation of nanodefects in the structure of the material. A significant decrease in elongation is observed compared with unirradiated material. The reason for this is the degradation of the main chains of the fluoroplastic. With an increase in the absorbed dose, the Young's modulus increases exponentially, which is associated with a decrease in the distance between atoms in the structure of the sample. The resulting effect can be used in industry. The curves obtained for both non-irradiated and irradiated material are satisfactorily described in the exponential model.

Comparing the efficacy of γ- and electron-irradiation of PBMCs to promote secretion of paracrine, regenerative factors

Cell-free secretomes represent a promising new therapeutic avenue in regenerative medicine, and γ-irradiation of human peripheral blood mononuclear cells (PBMCs) has been shown to promote the release of paracrine factors with high regenerative potential. Recently, the use of alternative irradiation sources, such as artificially generated β- or electron-irradiation, is encouraged by authorities. Since the effect of the less hazardous electron-radiation on the production and functions of paracrine factors has not been tested so far, we compared the effects of γ- and electron-irradiation on PBMCs and determined the efficacy of both radiation sources for producing regenerative secretomes. Exposure to 60 Gy γ-rays from a radioactive nuclide and 60 Gy electron-irradiation provided by a linear accelerator comparably induced cell death and DNA damage. The transcriptional landscapes of PBMCs exposed to either radiation source shared a high degree of similarity. Secretion patterns of proteins, lipids, and extracellular vesicles displayed similar profiles after γ- and electron-irradiation. Lastly, we detected comparable biological activities in functional assays reflecting the regenerative potential of the secretomes. Taken together, we were able to demonstrate that electron-irradiation is an effective, alternative radiation source for producing therapeutic, cell-free secretomes. Our study paves the way for future clinical trials employing secretomes generated with electron-irradiation in tissue-regenerative medicine.

Optimization of the coherence properties of diamond samples with an intermediate concentration of NV centers

The sensitivity of the nitrogen-vacancy (NV) color centers in diamond-based magnetometers strongly depends on the number of NV centers involved in the measurement. Unfortunately, an increasing concentration of NV centers leads to a decrease in their dephasing and coherence times if the nitrogen content exceeds a certain threshold level (approximately 1017cm-3 or 0.6 ppm). Here, we demonstrate that this increased dephasing can be efficiently compensated for by optimizing the electron irradiation dose in postprocessing procedures in the vicinity of the threshold concentration, thus extending the range of possible useful concentrations of NV centers in diamonds with a natural carbon content.

The effects of different doses of electron radiation on the electrical characteristics of ZnO interfacial Zn/n-Si junction

In this work, we have investigated the electrical characteristics of Zn/ZnO/n-Si/Au-Sb Schottky diodes before and after different doses (25 and 50 Gray) of electron-irradiation at room temperature. Initially, the ohmic contact has been made on n-Si semiconductor with Au-Sb alloy. After this process the ZnO thin film was grown on n-Si semiconductor by using RF magnetron sputtering system, and then the contact area is determined by sputtered Zn metal to surface of ZnO in DC sputtering system at about 10-6 Torr. The characteristic parameters of the junction such as ideality factor and barrier height values are calculated from I to V measurements and the carrier concentration, Fermi energy, diffusion potential, and barrier height values are calculated from reverse bias C-2–V measurements at various frequencies and room temperature. The I–V and C–V measurements of these diodes performed at room temperature and in dark. Experimental results showed that the values of the ideality factor increased and barrier height from forward-bias I–V measurements decreased and diffusion potential and the values of the barrier height obtained from reverse-bias C–V measurements decreased after electron-irradiation. However, changes in the characteristic parameters of the ZnO interfacial layer diode in 25 Gray of electron-irradiation were found to be less than those of the 50 Gray of electron-irradiation.

Examination of characteristic parameters of Zn/n-Si junction depending on electron radiation applied at different doses

In this work, we have studied the electrical characteristics of Zn/n-Si/Au-Sb Schottky diodes before and after different doses (25, 50 and 75 Gray) of electron-irradiation at room temperature. The ohmic contact has been made on n-Si crystal with Au-Sb alloy. The rectifier contact was sputtered Zinc metal on n-Si by using DC magnetron sputtering. The I–V measurements of these diodes performed by the use of a KEITLEY 487 Picoammeter/Voltage Source and the C–V measurements were performed with HP 4192A (50–13 MHz) LF Impedance Analyzer at room temperature and in dark. Experimental results showed that the values of the ideality factor obtained from I to V measurements increased and the values of the barrier height obtained from I to V and C–V measurements decreased after electron-irradiation.

Novel phenomenon of negative permittivity in silicon-based PiN diodes induced by electron irradiation

The negative permittivity of silicon-based PiN diodes is investigated experimentally in the frequency range from 1 Hz to 10 MHz, where electron irradiations and annealing thermal treatments are carried out. The permittivity is found be greatly affected by electron irradiations. In addition, the dispersion-free region is found be occurred in the samples irradiated by electron dose≥5.4646 × 10 14 e/cm 2 . Besides, annealing treatments also have an effect on the permittivity. It is interesting to find that, the annealing treatments lead to more negative platform (i.e., dispersion-free region) values of permittivity for samples irradiated by electron dose≥5.4646 × 10 14 e/cm 2 , and the negative platform values under 350 °C annealing treatment are lower than that under 150 °C annealing treatment when the electron irradiation dose is higher than 1.0929 × 10 15 e/cm 2 . The novel phenomenon found in this work may provide new ideas for the application of semiconductor devices in information transmission, storage and processing. • The negative permittivity of silicon-based PiN diodes induced by electron irradiation is investigated experimentally. • The negative permittivity in silicon-based PiN diodes can be induced by the electron irradiation. • Annealing treatments can recovery recovery the permittivity in the case with a relatively low electron dose. • The negative permittivity phenomenon in PiN diodes is considered be caused by defects induced by the electron irradiation.

Atomic-scale microstructure of metal halide perovskite.

Hybrid organic-inorganic perovskites have high potential as materials for solar energy applications, but their microscopic properties are still not well understood. Atomic-resolution scanning transmission electron microscopy has provided invaluable insights for many crystalline solar cell materials, and we used this method to successfully image formamidinium lead triiodide [CH(NH2)2PbI3] thin films with a low dose of electron irradiation. Such images reveal a highly ordered atomic arrangement of sharp grain boundaries and coherent perovskite/PbI2 interfaces, with a striking absence of long-range disorder in the crystal. We found that beam-induced degradation of the perovskite leads to an initial loss of formamidinium [CH(NH2)2 +] ions, leaving behind a partially unoccupied perovskite lattice, which explains the unusual regenerative properties of these materials. We further observed aligned point defects and climb-dissociated dislocations. Our findings thus provide an atomic-level understanding of technologically important lead halide perovskites.

Influence of electron irradiation on mechanical properties of epoxy polymers

The effect of different absorbed doses of electron irradiation with the energy of 12 MeV and heat treatment on the mechanical properties of ED-20 epoxy-dianic resin with hardener PEPA (11, 12 and 13 parts by weight per 100 parts by weight of epoxy resin) was investigated. Heat treatment of irradiated epoxy resin samples was performed in two modes: before or after electron irradiation. It is shown that the optimal choice of the content of hardener PEPA and using electron irradiation with the energy of 12 MeV in the integrated combination with heat treatment allow significantly improve the mechanical properties of epoxy-dianic resin.It was established that for the content of the hardener 12 parts by weight and absorbed doses of 10–20 kGy, the boundary of strength increases in 3 times, and additional heat treatment both before and after irradiation reduces this figure through the thermal destruction. Only for the content of hardener 11 and 13 parts by weight and these absorbed doses heat treatment of irradiated samples of epoxy resin leads to an increase in the boundary of strength. In doing so, the hardness increases regardless of the content of hardener for the absorbed doses greater than 50 kGy.

Mechanical properties of degraded OFE copper subjected to electron irradiation

• SPT specimens of OFE copper are subjected to electron irradiation in accelerator. • Experimental results are used to get mechanical properties as a function of dose. • Fracture toughness indicates a sharp drop in ductility beyond 62.5 MGy. • Such observation is validated by variation of YS, biaxial-fracture-strain and specimen energy. • A New correlation between biaxial-fracture-strain and specimen energy is derived. The mechanical and fracture properties of aged materials degrade due to metallurgical and micro- structural changes during service life. Miniaturized specimen testing methodology has been evolved over the years to quantify such degradation mechanisms. Oxygen Free Electronic (OFE) Copper has wide applications in nuclear industry, particularly in fusion reactors and accelerators. Such material when subjected to nuclear irradiation during service life experiences degradation of ductility and fracture toughness. In the present study, linear accelerator is used to irradiate OFE Copper specimens up to varying dose of irradiation. Specimens are subjected to electron irradiation dose which varies from 11 MGy to 91.5 MGy. The specimens are then tested, and the load-displacement curves thus generated are used to quantify changes in mechanical and fracture properties, viz. yield stress, ultimate stress, specimen energy at fracture, bi-axial fracture strain and fracture initiation toughness of irradiated specimens. It is observed that there is a loss of ductility of OFE copper beyond 62.5 MGy irradiation dose as indicated by decrease in biaxial fracture strain, specimen energy and fracture initiation toughness. Such changes should be taken into consideration for calculating service life during the design of components made up of OFE Copper subjected to irradiation.

Electrical Behavior of Graphene/SiO<sub>2</sub>/Silicon Material Irradiated by Electron for Field Effect Transistor (FET) Applications

In this paper, the detail study of electrical conductivity of single layer graphene (SLG) on silicon dioxide (SiO2)/Silicon substrate irradiated by high energy (MeV) electron is presented. The SLG samples prepared by Chemical Vapor Deposition (CVD) were irradiated by 50 kGy, 100 kGy and 200 kGy doses of electron radiation at energy voltage of 3 MeV. Current-Voltage (I-V) characteristics and conductivity of the pristine and irradiated graphene samples were measured and analysed using I-V measurement at room temperature. The non-linear I-V curves were clearly observed as the voltage reach to 2.0 V for non-irradiated and irradiated samples. This may be attributed to the non-uniform charges by high energy electron irradiation and poor metal contact of the sample. Hysteresis loop form at 2.0 V probably due to the to the charge trapping occurs at the interface of the graphene and SiO2. The reaction of high energy particles lead to creation of more carrier charges that contribute to the increment of conductivity compare to the small number of atom displacement of knock-on collisions with the nuclei of carbon atoms at higher dose. This study provides significant findings on the graphene electrical characteristics when irradiated with high energy (MeV) electron.

Comparative Results of Low Temperature Annealing of Lightly Doped N-Layers of Silicon Carbide Irradiated by Protons and Electrons

The influence of low-temperature (up to 400°С) annealing on the current-voltage and capacitance–voltage characteristics of Schottky diodes irradiated with protons with an energy of 15 MeV compared with the results of annealing of structures after irradiation with electrons with an energy of 0.9 MeV has been studied. It was shown that in case of proton irradiation with a dose of 4E13 cm-2 and electron irradiation with a dose of 1E16 cm-2, only partial carrier compensation occurs and the differential resistance is completely determined by the number of carriers in the epitaxial layer. The irradiation method has almost no effect on the direct current dependence on the voltage in the exponential segment. The ideality coefficient remains almost unchanged within 1.03 ÷ 1.04. During annealing after proton irradiation, a large activation energy of the process is required. The temperature of the beginning of annealing process during proton irradiation shifts to a larger value, from 150 °C to 250 °C when compared with electron irradiation. It has been demonstrated that at low doses of proton irradiation, the low-temperature annealing leads to the return to the conduction band of up to 65% of the removed charge carriers. After electron irradiation, low-temperature annealing returns up to 90% of the removed charge carriers to the conduction band. This indicates that at room temperature both proton irradiation as well as electron irradiation introduce both stable and unstable defects but in different proportions.

Modifying the Dielectric Properties of the TlGaS2 Single Crystal by Electron Irradiation

The dielectric properties and ac conductivity of an electronically irradiated layered TlGaS2 single crystal are studied in the frequency range of 5 × 104–3.5 × 107 Hz. It is established that electron irradiation of TlGaS2 single crystal samples with doses of 2 × 10l2 to 2.4 × 1013 e/cm2 leads to a decrease in the real component (e') of the complex dielectric permittivity in a high-frequency region (f > 106 Hz) and an increase in its imaginary component (e''), the dielectric loss tangent (tanδ), and ac conductance (σac) across the layers in the entire studied frequency range. At irradiation doses of 2 × 10l2 to 2.4 × 1013 e/cm2, losses in the reach-through conductivity of TlGaS2 occur, and, as the electron irradiation dose accumulates, the dispersion of e'' and tanδ increases significantly. In the frequency range of f = 5 × 104–2 × 107 Hz, in the irradiated TlGaS2 samples, the ac conductivity changes according to the law σac ~ fn (where n = 0.7–0.8), which is typical of the hopping mechanism of charge transfer via localized states near the Fermi level. The parameters of localized states in TlGaS2 (the density of the states near the Fermi level and their energy spread) are estimated versus the electron irradiation dose.

Introduction rates of radiation defects in electron irradiated semiconductor crystals of n-Si and n-GaP

A study was made of the introduction rate of radiation defects ΔNdef/ΔD versus the fast electron irradiation dose (D) in semiconductor crystals of n-Si and n-GaP. We take the concentration of radiation defects concentration Ndef to be the difference between the carrier concentration of semiconductors before n0 and after irradiation n(D) at the dose D, delivered at room temperature. By application of an appropriate fitting function to the dose dependent curves of the Ndef(D), it was demonstrated that the empiric exponential law of the form Ndef=n0(1−exp(−D/D0)) gives the best agreement with the experimental data, irrespective of the electron energy and irradiation dose. D0 is the irradiation dose, at which the carrier concentration n(D) at a temperature T=300K decreases by a factor of e. The results showed that the formation of radiation defects in the samples studied is not a linear process and ΔNdef/ΔD are found to decrease exponentially with increasing irradiation dose, according to their particular character. Using the same fitting method, it was found that for certain samples, beyond a particular radiation dose level, the rate of carrier mobility versus radiation dose also decreased exponentially.

Comparison and study of the preparation methods for phosphor layer in nuclear battery

This work investigated the preparation and optimization of phosphor layer for radioluminescent nuclear battery, and analyzed the property change of the phosphor after irradiation. ZnS:(Cu, Al) with grain size of 5 μm was selected as the phosphor material, and AlGaInP semiconductor was used as the photovoltaic unit. Monte Carlo modeling was used to simulate energy deposition, absorbed dose, penetration of β particles in the phosphor. The optimized coupling scheme of radioisotope sources and phosphor layer was obtained based on comparison particle penetration depth and the output power of radioluminescent nuclear battery. The phosphor layer with 60Co γ-radiation enhanced the luminescence property up to 50% at the radiation dose of 871 kGy, which is considered as an optimized method of phosphor layer preparation. The radiation of 10 MeV electron was conducted to study the degradation based on the microscopic lattice characteristics, morphological changes, optical and electrical properties. Phosphors have excellent radiation resistance. The output power of nuclear batteries has only declined by 43% even when electron radiation dose reaches 8.56 MGy. The prospect for utilizing ZnS:(Cu, Al) phosphor as radiant energy conversion materials in nuclear battery was also discussed. Results provided an effective guideline for predict the service conditions of radioluminescent nuclear battery.

Effect of electron irradiation on some physical, chemical and digestion properties of pistachio by-products

In the present study pistachio by-products (PB) were treated with various doses of electron irradiation (10–100 kGy). The results indicated that applied doses of electron irradiation had no effect on organic matter (OM), crude protein (CP) and ether extract content of PB. Irradiation increased (P < 0.01) total phenol content; while decreased cell wall compartment, tannin (P = 0.05) and condensed tannin (P = 0.03) contents. Irradiation decreased (P = 0.04) water binding capacity (WBC), but increased (P < 0.05) solubility of dry mater (DM), OM and protein of PB with increasing in irradiation dose. Electron irradiation effectively increased rapidly degradable fraction (a) and decreased potentially degradable fraction (b) of DM and OM of PB in the rumen of sheep compared to the control. The FTIR spectra of samples revealed similar pattern without any changes in the functional group status with a decrease in relative transmittance of peaks in irradiated groups. In conclusion, this study showed that electron irradiating can effectively change physical and chemical; and digestive properties of PB.