Low Energy Electron Beam Irradiation Research Articles

Isolated single-photon emitters with low Huang–Rhys factor in hexagonal boron nitride at room temperature

The development of stable room-temperature bright single-photon emitters using atomic defects in hexagonal boron nitride flakes (h-BN) provides significant promise for quantum technologies. However, an outstanding challenge in h-BN is the creation and detection of isolated, stable single-photon emitters with high emission rates and with very low Huang–Rhys (HR) factor. Here, we discuss the quantum photonic properties of a single, isolated, stable quantum emitter that emits single photons with a high emission rate and a low HR value of 0.6 ± 0.2 at room temperature. A scanning confocal image confirms the presence of a deserted, single-quantum emitter with a prominent zero-phonon line at ∼578 nm with a well-separated phonon sideband at 626 nm. The second-order intensity-intensity correlation measurement shows an anti-bunching dip of ∼0.25 with an emission lifetime of 2.46 ± 0.1 ns, reinforcing distinct features of the single-photon emitter. The importance of low-energy electron beam irradiation and subsequent annealing is emphasized to achieve stable, reproducible single-photon emitters.

Electron beam irradiation-induced atomically thin domes of two-dimensional materials: Graphene and MoS[formula omitted]

The local strain-induced indirect-to-direct band gap transition in bulk transition metal dichalcogenides (TMDCs) holds great potential for optoelectronic applications. The formation of domes on the topmost layer of a multilayered flake through hydrogen ion H+ irradiation is an effective technique for tuning the band gap locally via molecular hydrogen (H2) confinement. In this work, we present an alternative robust, simpler, and faster technique for concurrently forming and visualizing dome-like structures of two-dimensional (2D) materials through low-energy electron beam irradiation. We investigated the growth mechanism and dynamics of the domes under exposure to electron beams at different energy levels. The simultaneous production and imaging of atomically thin domes of 2D materials has several practical and fundamental applications, such as mass storage and transport, single photon emission, nano/micro-electromechanical sensors, strain engineering, etc.

Novel liquid dosimeters for low-energy electron beam irradiation in low and medium dose ranges

Low-energy electron beam irradiation, which refers to the treatment of matter with accelerated electrons at energies below 300 keV, is gaining attention for many applications in life sciences. In the scope of vaccine production, low-energy electron irradiation is an efficient and chemical free technology to inactivate viruses. Low-energy electron beam irradiation has also been proposed to be a powerful technique for its use in biotechnological processes. As biotechnological applications operate in an aqueous environment, there is an urgent need for accurate dose quantification in liquids, especially for low (< 500 Gy) and medium doses (500–5000 Gy). This study investigated dye solutions of xylenol orange tetrasodium, 1,9-dimethylmethylene blue, resazurin sodium, and tartrazine for their suitability as radiochromic liquid dosimeters. The solutions were evaluated regarding their dose–response characteristics and storage stability prior to irradiation over a range of pH values and concentrations. The radiochromic dosimeters were irradiated with electrons with maximal energies of 200 keV and dose rates of 6.5 Gy/s to 45 Gy/s. Then, the absorbance was measured and response curves were plotted. The dye solutions of 1,9-dimethylmethylene blue and resazurin sodium covered a low to medium dose range from 100–1500 Gy and 100–1000 Gy, respectively. Tartrazine at pH 4 was suitable for quantification of doses from 100 Gy to 3500 Gy, which covers a wide dose range of biotechnological applications.

In vivo application of a glutaraldehyde-free, UVA/riboflavin cross-linked bovine pericardium confirms suitability for cardiovascular substitutes

Glutaraldehyde (GA)-treated bovine pericardium is still the gold standard for the fabrication of bioprostheses needed for the surgical treatment of valvular malfunction. Although excellent stability and low immunogenicity are accomplished, the application of GA is considered to be causal for structural valve deterioration, diminishing the long-term durability of bioprosthetic tissue. The novel GA-free SULEEI-treatment of bovine pericardium combines decellularization, riboflavin/UVA-cross-linking, and low-energy electron beam irradiation. In the present study, we initiated an in vivo application. We used a subcutaneous rat model to compare the immune and tissue responses, calcification propensity, and biomechanical properties of the alternatively prepared SULEEI bovine pericardial tissue with standard glutaraldehyde-fixed and industrially produced bovine pericardial patch material. SULEEI pericardium evokes a similar immune reaction and tissue response as the control standard bovine patch material. The calcification propensity of SULEEI tissue was low, and biomechanical analysis revealed a heterogeneous but similar pattern in tissue stiffness compared to the control patch. The results of this study highlight the potential of SULEEI-treated bovine pericardial tissue as a candidate for cutting-edge cardiovascular and valvular biomaterials in reconstructive surgery.

Characteristic features of relief formation on the surface of Ni3Al and Ni3Al-TiC composites as a result of low-energy high-current electron beam irradiation

Using scanning electron microscopy and roughness measurements we studied the relief appeared on the surface of TiC-free Ni3Al and Ni3Al-TiC composites (TiC content was 10 and 30 vol%) as a result of low-energy high-current electron beam irradiation (the surface energy density was in the interval of 8–18.0 J/cm2, the accelerating voltage was 30 kV, the pulse duration was 3.2 μs, the number of pulses was 10 and 30). Using the same materials differing in the content of non-metallic particles for investigation enabled clarification of the role of non-metallic inclusions in the relief formation. The effect of the particles size, surface energy density and number of pulses was also analyzed. Three types of dimples forming the relief were revealed. Each of the type appeared following to its own formation mechanism. The applicability of the models existing in literature to explain relief formation was discussed.

The effect of low-energy high-current pulsed electron beam irradiation on the structure, phase composition and mechanical properties of Ni3Al and Ni3Al-TiC composites

Using scanning and transmission electron microscopy, X-ray diffraction, indentation and bending tests we studied the evolution of microstructure, phase composition and mechanical properties of TiC-free Ni3Al and Ni3Al-TiC composites (TiC content was 10 and 30 vol%) fabricated by self-propagating high-temperature synthesis (SHS) under pressure induced by low-energy high-current pulsed electron beam (LEHCEB) irradiation with the surface energy density of 8, 12 and 18 J/cm2. It was found that the irradiation results in the improvement of phase composition of the near-surface layer by way of the increase of yield of SHS reaction. LEHCEB irradiation enables formation of nanocomposite structure in the near-surface layer of Ni3Al-TiC composites with decreased grain size of Ni3Al matrix, refined TiC particles and increased volume fraction of TiC. This structure leads to the increase of microhardness but decrease of strength under bending. Two mechanisms of TiC particles refining are suggested. The effect of surface energy density on the manifestation degree of the found phenomena is discussed. The contribution of different hardening mechanisms to the overall hardening is considered.

Increasing Bending Strength of Polycarbonate Reinforced by Carbon Fiber Irradiated by Electron Beam.

In an interlayered carbon fiber-reinforced polycarbonate polymer (CFRPC) composite composed of three sized of CF plies, alternating between four PC sheets, designated [PC]4[CF]3, and a new process of activating CF cross-weave cloth plies directly on both sides with homogeneous low-energy electron beam irradiation (HLEBI) before lamination assembly and hot pressing at 6.0 MPa and 537 K for 8 min was produced. Experimental results show that a dose of 215 kGy of HLEBI raised the bending strength, σb, at each experimental accumulative probability, Pa, with the σb at a median Pa of 0.50, increasing by 25% over that of the untreated sample. Three-parameter Weibull analysis showed that when quality can be controlled, a dose of 215 kGy of HLEBI can raise the statistically lowest bending strength, σs, at Pa = 0 (94.3 Mpa), with a high correlation coefficient. This is because, although it had a higher bending strength than that in the other experimental conditions, the weakest sample of the 215 kGy data set had a much lower σb value than that of the others. Electron spin resonance (ESR) of the CF showed that naturally occurring dangling bonds in CF were increased at 215 kGy. Charge transfer to the PC occurs, apparently generating stronger bonds, which are possibly covalent, resulting in enhanced adhesion at the CF-PC interface.

Doping-induced Ti3+ state and oxygen vacancies in TiO2: A single-chip combinatorial investigation

TiO2 is widely recognized as a high performance photocatalyst for photocatalytic applications. Oxygen vacancies (VO) and titanium defects are known to make a significant contribution to the enhanced photocatalytic efficiency of TiO2, accordingly control of these two centers is pivotal to optimizing the surface photochemical activity. In this work, the formation of VO and Ti3+ ions induced by n-type doping of TiO2 with Nb is demonstrated using a combinatorial investigation approach. Chemical Beam Vapour Deposition (CBVD) is used to fabricate Nb concentration-graded (NbxTi1-x)O2 anatase films with 0.009 ≤ x ≤ 0.033 over a 5 mm length on a single chip. Cathodoluminescence (CL) microanalysis shows the luminescence intensity decreases with increasing Nb concentration; however, the presence of a self-trapped exciton (STE) emission, characteristic of anatase TiO2, indicates that the Nb incorporation does not affect the structural properties of TiO2. Notably, the introduction of Nb donors induces the formation of the signature luminescence bands of VO and Ti3+ at 2.05 and 2.60 eV at 80 K, respectively, and their intensities rise by up to 28% with increasing Nb content. The formation of VO and Ti3+ is attributed to the effect of excess electrons locally produced by Nb donor doping. The thermal activation energies for the STE and defect-related emissions are found to be identical at 32 ± 4 meV, suggesting that the recombination kinetics is mediated by Nb donors. Significantly, we demonstrate that the near-surface VO density can be further increased by two different post-growth treatment approaches: (i) remote hydrogen plasma and (ii) low-energy electron beam irradiation (LEEBI), without effecting the valence state of Ti. Our results open opportunities to optimize the photocatalytic properties of TiO2 by defect engineering.

An Experimental Study of Dislocation Dynamics in GaN.

The dynamics of dislocations introduced through indentation or scratching at room temperature into a few GaN layers that were grown using the HVPE, MOCVD and ELOG methods and had different dislocation densities were studied via the electron-beam-induced current and cathodoluminescence methods. The effects of thermal annealing and electron beam irradiation on dislocation generation and multiplication were investigated. It is shown that the Peierls barrier for dislocation glide in GaN is essentially lower than 1 eV; thus, it is mobile even at room temperature. It is shown that the mobility of a dislocation in the state-of-the-art GaN is not entirely determined by its intrinsic properties. Rather, two mechanisms may work simultaneously: overcoming the Peierls barrier and overcoming localized obstacles. The role of threading dislocations as effective obstacles for basal plane dislocation glide is demonstrated. It is shown that under low-energy electron beam irradiation, the activation energy for the dislocation glide decreases to a few tens of meV. Therefore, under e-beam irradiation, the dislocation movement is mainly controlled by overcoming localized obstacles.

Ti-based surface alloy formed on AISI 316 L austenite steel surface using low-energy high-current electron beam

Titanium and Ti-based alloys possess good biocompatibility and excellent corrosion resistance. This paper is devoted to an effort to create Ti-based surface alloy on specimens made of the AISI 316 L austenite steel. The Ti-based surface alloy is created by the Ti film deposition using the magnetron sputtering method followed by the low-energy high-current electron beam irradiation of the Ti film–316 L steel substrate system surface. Transmission electron microscopy shows that the surface alloy consists of several sublayers having different structures and phase compositions. In particular, these are α-Ti; TiSi2; FeTi and Fe2Ti; Fe2SiTi; Fe2Ti3O9 phases and more complex Cr13Fe35Ni3Ti7, Cr12Fe32Mo7Ni7, Cr12Fe36Mo10, Mo5Cr6Fe18 phases nearby the substrate. Phase compositions of the surface alloy layers are determined by the change in the chemical composition of the titanium–steel system and the heat depth distribution. It is shown that the formation of the Ti-based surface alloy on the AISI 316 L austenite steel surface, provides the increase in the polar component of the free surface energy from 3.2% to 34.5%.

Evolution of morphology, microstructure and phase composition of zirconia thin coating on copper as a result of low energy high current pulsed electron beam irradiation

Using X-ray diffraction, scanning and transmission electron microscopy we studied the evolution of the morphology, microstructure and phase composition in the near-surface layer of copper covered with thin (2.8 μm) ZrO2 coating induced by low-energy high-current pulsed electron beam irradiation (the surface energy density was in the interval of 5.0–18.0 J/cm2, the accelerating voltage was 30 kV, the pulse duration was 3.2 μs, the number of pulses was 10). The variation of adhesion of the coating to substrate was evaluated using scratch testing. The evaporation of the upper part of the coating during irradiation was found and the thickness of the coating nonlinearly decreased with the increase of the energy density. We discussed the reasons for the surface cracking taking into account microstructural changes in the near-surface layer of the material. The irradiation was found to transfer most of monoclinic ZrO2 phase in the as-deposited coating to tetragonal and, possibly, cubic one. The factors influencing the adhesive strength of the coating were revealed and a potential for the increase of adhesion was demonstrated. We showed that irradiation with enhanced surface energy density was required to obtain copper-based composite hardened with zirconia nanoparticles in the near-surface layer. The thickness of the composite layer may be as much as 6 μm.

Ultrasensitive self-powered heterojunction ultraviolet photodetector of p-GaN nanowires on Si by halide chemical vapour deposition

In this study, we report the fabrication of quasi-aligned p-GaN nanowires (NWs) on n-Si (1 1 1) substrate by halide chemical vapour deposition (HCVD) using MgCl2 precursor and followed by low-energy electron beam irradiation to activate the Mg acceptor doping in GaN NWs. We aimed to attain a comprehensive understanding of p-doping in GaN NWs growth, extensive characterizations and fabrication of UV photodetector (PDs) based on p-GaN NWs/n-Si heterojunction. To realize the efficient UV photodetectors, we measure the current–voltage (I–V) characteristics of heterojunction PDs under dark and illuminated conditions and the I–V curve demonstrates good rectifying behaviours with 0.2 V turn-on voltage. At zero bias, the heterojunction PDs show a reverse photocurrent of 1.27 × 10−6 A with a very low dark current of 2.35 × 10−9 A under 325 nm UV illumination. Besides, the significance of the self-powered operation of UV PDs and the charge transfer mechanism are discussed with the aid of the energy band diagram. The substantial photocurrent increment with varying applied potential leads to narrowing the photo potential in the interface. The excitonic bound states present in p-GaN NWs/n-Si heterojunction is further elucidated. As a result, the heterojunction PDs demonstrate the high responsivity, detectivity, and external quantum efficiency of 134 mA W−1, 3.73 × 1013 Jones, and 51% respectively, at 0.1 V low applied potential under the reverse bias condition. The proposed work provides an archetype for Mg doping in GaN NWs ensembles, which will help to facilitate the heterojunction with n-Si to unleash the potential of self-powered UV PDs.

Strengthening Process by Electron Beam to Carbon Fiber for Impact Strength Enhancement of Interlayered Thermoplastic-Polypropylene Carbon Fiber Composite.

Strong adhesion between recyclable thermoplastic (TP) polymer and carbon fiber (CF) has always been highly sought after. Therefore, for an interlayered CF reinforced TP polypropylene (CFRTPP) composite composed of 3 sized CF plies, alternating between 4 PP sheets, designated [PP]4[CF]3, a process of activating CF plies directly on both sides with homogeneous low energy electron beam irradiation (EBI) under N2 gas, prior to lamination assembly and hot press of 4.0 MPa at 493 K for 3 min was carried out. Experimental results showed EBI dose of 43.2, 129, or 216 kGy significantly raised Charpy impact values, auc at all fracture probabilities, Pf. The 129 kGy dose appeared to be at or near optimum increasing auc 103%, 83%, and 65% at low-, median-, and high-Pf = 0.07, 0.50, and 0.93; while raising statistically lowest impact value, as at Pf = 0 calculated by 3-dimensional Weibull equation about 110%, indicating increased safety and reliability. It is assumed dangling bonds generated by the EBI rapidly form covalent bonds CF:C:O:C:PP and CF:C:C:PP at the interface, along with cross-linking in the PP near the CF. This is by charge transfer from CF to PP.

Influence of low-energy electron beam irradiation on the quality and shelf-life of vacuum-packaged pork stored under chilled and superchilled conditions

This study aimed to explore the effects of different levels (0, 8, and 12 kGy) of low-energy electron beam (LEEB; 0.2 MeV) on the quality and shelf-life of vacuum-packaged pork stored under chilled and superchilled conditions for 30 days. LEEB irradiation promoted lipid and protein oxidation, regardless of the levels used. Combined 8 kGy LEEB irradiation with superchilled storage significantly elevated a* values and preserved acceptable sensory characteristics of pork until day 30, unlike the other treatment combinations. This synergistic treatment also significantly reduced total viable counts and total volatile basic nitrogen contents, and thus extended the shelf-life of vacuum-packaged pork to >30 days, which may be due to the antibacterial effects on Photobacterium, Carnobacterium and Lactobacillus. In conclusion, it is recommended that the 8 kGy LEEB irradiation level be applied to pork and that it should be used in combination with superchilled storage to preserve meat quality and extend the shelf-life of vacuum-packaged pork.

Effects of low-energy electron beam irradiation on the shelf-life and quality of vacuum-packaged beef steaks during chilled storage

This study evaluated the effects of different doses (0, 4, 8, 12, 16 kGy) of low-energy electron beam (LEEB; 0.2 MeV) on the quality changes of vacuum-packaged beef steaks during chilled storage for 21 days. LEEB irradiation at a low dose (4 and 8 kGy) significantly elevated the L* values of steaks, and did not deteriorate the a* values, the oxidation of lipid and protein (P > 0.05) compared to non-irradiated samples. LEEB irradiation (4 and 8 kGy) also significantly reduced the bacterial loads compared with non-irradiated steak, which may be due to the inactivation effect on Acinetobacter, Brochothrix thermosphacta, Carnobacterium divergens, Leuconostoc and Serratia during storage. Albeit all doses retained more acceptable sensory characteristics compared to non-irradiated samples, LEEB irradiation with >8 kGy significantly reduced the L* values and promoted protein oxidation. Overall, the LEEB irradiation with 4–8 kGy could be used as a promising innovative technology for extending the shelf-life of vacuum-packaged chilled beef steaks.

Densification of SiO2 films via low-energy electron-beam irradiation

Flat and dense SiO2 (the most widely used oxide material in integrated circuit (IC) technology) films could facilitate the rapid scaling down of semiconductor devices. Herein, a DC power of 1-kV was used for the electron-beam irradiation (EBI) of sputtered-SiO2 films on glass. Within 5 min of EBI treatment, at room temperature, the SiO2 films exhibited 10% increase in density, and 25% decrease in surface roughness compared to as-sputtered SiO2. XPS results indicated that 1-kV EBI modulated the density and surface roughness of SiO2 films, without affecting their chemical bonding and atomic ratio. Therefore, low-energy EBI could be used as an efficient method to enhance the characteristics of SiO2 thin films for semiconductor applications.

О порогах плавления системы «пленка - подложка» при облучении низкоэнергетическим сильноточным электронным пучком

The effect of film material thermal conductivity on the melting threshold of the film-substrate system depending on the film thickness during a low-energy high-current electron beam (LEHCEB) irradiation was analyzed based on the numerical solution of the one-dimensional unsteady heat equation with a volumetric thermal source. Experimentally obtained oscillograms of the beam current at the collector and the accelerating voltage were used to simulate the heating source. Numerical variations of the film thermal conductivity were carried out within a wide range, overlapping the entire range for real materials. The dependence of the melting threshold of a homogeneous material on thermal conductivity was determined. The general regularities of the behavior of film and substrate melting thresholds depending on the film thickness were also established.

Use of low-energy electron-beam in the treatment of special food products with a high protein content

Special high-protein foods suitable for diabetics must be treated to ensure the complete absence of microorganisms and bacteria. It is also important to achieve that this treatment does not change the nutritional value of the product. Among the new decontamination technologies, low-energy electron-beam treatment has proven to be an effective technique for inactivating bacteria with minimal impact on food quality. The paper aims to analyze the influence of low-energy electron-beam irradiation on the microbiological properties and nutritional value of high-protein foods.

Depth dose curve and surface dose measurement with a μm thin dosimetric layer

In a former work inorganic phosphor particles NaYF4:Yb3+, Er3+ were found to exhibit a radiation dose dependency of their luminescence decay time upon near-infrared excitation. This material is now presented in the form of an ultra-thin dosimeter to measure depth dose curves. They were derived by electron beam irradiation of 1.6 μm thin dosimeters through a stepped stack of absorber polymer films followed by optical decay time evaluation. The suitability of the phosphor dosimeters for depth curve measurement is proven by good agreement in normalized dose results with film dosimeter (Risø B3 strips) after medium-energy electron-beam irradiation. But the approach qualifies especially for use at low-energies, where original measurement results from as close as 3–4 μm (water equivalent) from the surface are obtained for 80, 140 and 200 keV e-beam irradiations. They align well with results from Monte Carlo simulations. Thus, an approach is proposed for discussion which may allow the experimental evaluation of the first μm of depth dose curves after low-energy electron beam irradiation.

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.