Employing Electron Beam Research Articles

A novel approach for enhancing the mechanical behavior of additively manufactured metal matrix composite structures: Preliminary investigation

Additive Manufacturing is a promising technique for expanding the boundaries of Metal Matrix Composites. In this study, Powder Bed Fusion (PBF) technique, employing Electron Beam as the heat source, was used to print Ti6Al4V metal matrix in different geometric shapes with a new approach for MMC fabrication. Yttria Stabilized Zirconia (YSZ) powder was then incorporated into these pattern shapes, compacted, and sintered to bind the powder particles together. The findings showed that successful sintering was achieved, resulting in the formation of a flexible interface region, with the circular design achieving the best interface region among all pattern designs. Regarding the mechanical performance evaluation of the developed Metal Matrix Composites, it was found that the mechanical strength was significantly increased with the hexagonal and circular patterns achieving the best results. Future research should pay more attention to further design development for the metal matrix model to achieve outstanding performance and create a new field for Metal Matrix Composites using the developed method.

Electron beam induced graft polymerized anti oil-fouling biaxial polypropylene membrane with harsh environment tolerance

The intrinsic hydrophobic behavior of biaxial-oriented polypropylene microporous membrane limits its broad application area by leading serious membrane fouling. An environment-friendly, practical, and facile to large-scale prepared surface modification process is designed to enhance the membrane wettability and oil-fouling. By employing electron beam radiation, acrylic acid, and polyvinyl alcohol in the pre-irradiation-induced graft polymerization process, a micro-nano structure was developed and the surface roughness was increased from 66.5 nm to 99.3 nm. Enhancing the grafting ratio further reduces the pore size of the final modified membrane from 54 nm to 25 nm, which is significantly smaller than the size of the emulsified oil droplet. By modifying the morphological and structural characteristics of the grafted membrane, excellent oil-fouling resistance features are attained with UWOCA value 161° and separation efficiency of 99.3 %. Moreover, the theoretical explanations for hydrophilicity and oil-fouling resistance of modified membranes are also developed using DFT calculations and the Hermia model, which shows alignment with experimental data. Consequently, considerable improvements in wettability, thermal and mechanical behavior are obtained by this facial surface modification approach, which could further broaden the modified membrane's applications area in membrane separation technology while lengthening its service life.

Atomically self-healing of structural defects in monolayer WSe2

Abstract Minimizing disorder and defects is crucial for realizing the full potential of two-dimensional transition metal dichalcogenides (TMDs) materials and improving device performance to desired properties. However, the methods in defect control currently face challenges with overly large operational areas and a lack of precision in targeting specific defects. Therefore, we propose a new method for the precise and universal defect healing of TMD materials, integrating real-time imaging with scanning transmission electron microscopy (STEM). This method employs electron beam irradiation to stimulate the diffusion migration of surface-adsorbed adatoms on TMD materials grown by low-temperature molecular beam epitaxy (MBE), and heal defects within the diffusion range. This approach covers defect repairs ranging from zero-dimensional vacancy defects to two-dimensional grain orientation alignment, demonstrating its universality in terms of the types of samples and defects. These findings offer insights into the use of atomic-level focused electron beams at appropriate voltages in STEM for defect healing, providing valuable experience for achieving atomic-level precise fabrication of TMD materials.

Controlling Nanoparticle Distance by On-Surface DNA-Origami Folding.

DNA origami is a flexible platform for the precise organization of nano-objects, enabling numerous applications from biomedicine to nano-photonics. Its huge potential stems from its high flexibility that allows customized structures to meet specific requirements. The ability to generate diverse final structures from a common base by folding significantly enhances design variety and is regularly occurring in liquid. This study describes a novel approach that combines top-down lithography with bottom-up DNA origami techniques to control folding of the DNA origami with the adsorption on pre-patterned surfaces. Using this approach, tunable plasmonic dimer nano-arrays are fabricated on a silicon surface. This involves employing electron beam lithography to create adsorption sites on the surface and utilizing self-organized adsorption of DNA origami functionalized with two gold nanoparticles (AuNPs). The desired folding of the DNA origami helices can be controlled by the size and shape of the adsorption sites. This approach can for example be used to tune the center-to-center distance of the AuNPs dimers on the origami template. To demonstrate this technique's efficiency, the Raman signal of dye molecules (carboxy tetramethylrhodamine, TAMRA) coated on the AuNPs surface are investigated. These findings highlight the potential of tunable DNA origami-based plasmonic nanostructures for many applications.

Nanofabricated high turn-density spiral coils for on-chip electromagneto-optical conversion

Circuit-integrated electromagnets are fundamental building blocks for on-chip signal transduction, modulation, and tunability, with specific applications in environmental and biomedical micromagnetometry. A primary challenge for improving performance is pushing quality limitations while minimizing size and fabrication complexity and retaining spatial capabilities. Recent efforts have exploited highly involved three-dimensional synthesis, advanced insulation, and exotic material compositions. Here, we present a rapid nanofabrication process that employs electron beam dose control for high-turn-density diamond-embedded flat spiral coils; these coils achieve efficient on-chip electromagnetic-to-optical signal conversion. Our fabrication process relies on fast 12.3 s direct writing on standard poly(methyl methacrylate) as a basis for the metal lift-off process. Prototypes with 70 micrometer overall diameters and 49–470 nm interturn spacings with corresponding inductances of 12.3–12.8 nH are developed. We utilize optical micromagnetometry to demonstrate that magnetic field generation at the center of the structure effectively correlates with finite element modeling predictions. Further designs based on our process can be integrated with photolithography to broadly enable optical magnetic sensing and spin-based computation.

Novel Nano-Electroplating-Based Plasmonic Platform for Giant Emission Enhancement in Monolayer Semiconductors.

Two-dimensional semiconductors such as monolayer MoS2 have attracted considerable attention owing to their exceptional electronic and optical characteristics. However, their practical application has been hindered by the limited light absorption resulting from atomically thin thickness and low quantum yield. A highly effective approach to address these limitations is by integrating subwavelength plasmonic nanostructures with monolayer semiconductors. In this study, we employed electron beam lithography and nanoelectroplating techniques to develop a gold nanodisc (AuND) array plasmonic platform. Monolayer MoS2 transferred on top of the AuND array yields up to 150-fold photoluminescence enhancement compared to a gold film without normalization with respect to plasmonic hot spots. In addition, the unique protocol of nanoelectroplating helps to get flat-top cylindrical discs which enable less tear during the delicate wet transfer of monolayer MoS2. We explain our experimental findings based on electromagnetic simulations.

From design to realization of high diffraction efficiency Littrow configuration diffraction gratings based on multilayer dielectric mirrors patterned with electron beam lithography

Diffraction efficiency (DE) and laser-induced damage threshold of Chirped pulse amplification (CPA) system diffraction gratings (DGs) are one of the main limiting factors for the anticipated progress of high peak power lasers. Optimization of a high reflectivity dielectric multilayer ZrO2/SiO2 stack mirror with a DG etched in the top SiO2 layer was carried out employing the Rigorous coupled wave analysis method. Two families of solutions possessing DE > 0.99 over the bandwidth of the 1030 nm wavelength ultrashort laser and withstanding different fabrication margins were identified for the Littrow configuration. DGs were produced and verified experimentally. Structures permitting variation in both the depth of the DG and filling factor without loss in DE were obtained for the 690 nm thick SiO2 layer. While the 770 nm thick layer permitted separation of the two parameters requiring either rigorous control of the DG depth or filling factor. DG realization technology was proposed employing electron beam lithography and inductively coupled plasma reactive ion etching. Measurements of the fabricated structures demonstrated 0.91 DE for the first diffraction order over the 60 nm bandwidth and under a 6° mounting error from the Littrow configuration. Spectral angular reflectance DE simulations and respective measurements indicated quantitative agreement. The work provides an integrated overview of high DE periodic structure numerical optimization and manufacturing roadmap which could be applied for the high-peak-power laser CPA system development.

Comparing the DNA-damage RBE of intraoperative and conventional electron beams using a hybrid simulation approach

Purpose Employing electron beam for radiotherapy purposes now has been established as one of the standard cancer treatment modalities. Both dedicated intraoperative and conventional electron beams can be employed in patient irradiation. Due to the differences between accelerating structure and electron beam delivery of dedicated intraoperative radiotherapy (IORT) machines and conventional ones, the initial energy spectra of the produced electron beam by these machines may be different. Accordingly, this study aims to evaluate whether these spectral differences can affect the relevant relative biological effectiveness (RBE) values of intraoperative and conventional electron beams. Materials and methods A hybrid Monte Carlo simulation approach was considered. At first, the head LIAC12 machine (as an IORT accelerator) and Varian 2100C/D (as a conventional accelerator) were simulated by MCNPX code and electron energy spectra at different depths and off-axis distances were scored for two nominal electron energies of 6 and 12 MeV at the field sizes of 6 and 10 cm. Then, the calculated spectra were imported to MCDS code to estimate the induced DNA-damage RBE values. Finally, the obtained RBE values for intraoperative and conventional electron beams were compared together. Results The results showed that the RBE values of the intraoperative electron beam are superior to those obtained for conventional electron beam at the same energy/field size combination. Variations of the depth can regularly affect the RBE value for both conventional and intraoperative electron beams, while no ordered variation trend was observed for RBE with changing the off-axis distance. Variations of electron energy and field size can also influence the RBE value for both types of studied electron beams. Conclusions From the results, it can be concluded the structural differences between the dedicated IORT and conventional Linacs can lead to distinct initial electron energy spectra for intraoperative and conventional electron beams. These physical differences can finally lead to different RBE values for intraoperative and conventional electron beams at the same energy and field size.

Tuning interactions in nanopore arrays with charges on the pore walls

Physiological processes at the cellular level are regulated by nanoconfined ionic transport. Protein channels regulate the passage of specific ions into and out of the cell, and biological systems rely on the concerted function of many channels embedded in their membranes. For instance, the propagation of an action potential down an axon is moderated by the coordinated transport of sodium and potassium ions across neuronal membranes. Beyond its ubiquity in biological systems, transport across nanoporous devices has industrial applications such as single-molecule sensing, energy storage, and water desalination. While single nanopore systems have been thoroughly studied in both biological and industrial contexts, systems containing an array of multiple nanopores are of increasing interest. Due to the close proximity of channels in an array, local environmental changes at the interface of one channel may influence the transport properties of neighboring channels. In this work, we fabricated nanopore arrays with tunable geometries and surface chemistries to probe this cross-talk between nanopores. We employed electron beam sculpting of silicon nitride membranes to fabricate arrays containing two and three nanopores. This method allowed us to engineer devices of varying interpore distances to probe neighboring interactions as a function of interpore distance. Using electrochemical methods, we characterized the current-voltage response of each array at varying sizes of the electric double layer to probe the nature of interpore interactions. Furthermore, we explored surface modifications to create nanopores with bipolar surface charge distributions, which effectively act as ionic diodes. Our results are also complemented by computational modeling. An exploration of the electrokinetic phenomena of these arrays will deepen our understanding of the interplay between neighboring channels, elucidating the mechanisms behind ionic sieving on the scale of an entire network of nanopores.

Development of substrate engineered Si-/[100] Patterned Features by anisotropic wet etching with Pt/Pt3Si mask

In the current article, a substrate engineered patterned array of square-shaped features of size 1.5 μm × 1.5 μm comprising of <111>/[100]-planes of p-Si substrate has been developed by employing electron beam lithography assisted selective anisotropic wet etching. The etching of such planes is performed by combining the effect of KOH as the chemical etchant and Pt/Pt3Si as the mask with its catalyzing properties for the etching reaction. The regular array of exposed <111>/[100]-planes is confirmed by FESEM imaging and X-ray diffraction study. The formation of a ‘virtual hetero-junction’ at <111>/[100] interface is characterized by in-situ current-voltage measurement within the FESEM chamber. Such surface engineered Si-substrates can be utilized for multifaceted applications by fabricating different types of electronic, optoelectronic and bio-sensing devices.

Electron Beam Welding and Post Heat Treatment of a New Near-Beta High-Strength Ti-4Al-5Mo-5V-5Cr-1Nb Alloy

Ti-4Al-5Mo-5V-5Cr-1Nb (wt.%) is a new type of high-strength (~1300 MPa) titanium (Ti) alloy developed for aerospace applications. Until now, the research on its welding and subsequent heat treatment is barren. Herein, we employed electron beam welding (EBW) to a solutionized Ti-4Al-5Mo-5V-5Cr-1Nb with a phase constituent of α + β and investigated its microstructure and mechanical properties in both as-welded (AW) and post-weld aging treated (PWAT) conditions. Results showed that due to the thermal input of the welding process, the α phase in the original microstructure of base material (BM) transformed into the β phase in the fusion zone (FZ). Similar microstructural evolution was observed for the heat-affected zone (HAZ) near the FZ (Near-HAZ), whereas the HAZ far away from FZ (Far-HAZ) contained a small amount of round α phase (ghost α) due to its slower cooling rate. Such a microstructural change resulted in poor tensile strength (~780 Mpa) for the as-welded joint. After PWAT, a large number of acicular α precipitated in the FZ and HAZ and its size (S) in different zones followed the order of SFar-HAZ &lt; SFZ ≈ SNear-HAZ &lt; SBM. The presence of αs precipitates remedied the tensile strength of the weld joint almost to the same as that of the BM. The present findings established the foundation of the application of this high-strength Ti alloy.

Atomic-Scale Tracking of Dynamic Nucleation and Growth of an Interfacial Lead Nanodroplet.

Revealing the evolutional pathway of the nucleation and crystallization of nanostructures at the atomic scale is crucial for understanding the complex growth mechanisms at the early stage of new substances and spices. Real-time discrimination of the atomic mechanism of a nanodroplet transition is still a formidable challenge. Here, taking advantage of the high temporal and spatial resolution of transmission electron microscopy, the detailed growth pathway of Pb nanodroplets at the early stage of nucleation was directly observed by employing electron beams to induce the nucleation, growth, and fusion process of Pb nanodroplets based on PbTiO3 nanowires. Before the nucleation of Pb nanoparticles, the atoms began to precipitate when they were irradiated by electrons, forming a local crystal structure, and then rapidly and completely crystallized. Small nanodroplets maintain high activity and high density and gradually grow and merge into stable crystals. The whole process was recorded and imaged by HRTEM in real time. The growth of Pb nanodroplets advanced through the classical path and instantaneous droplet coalescence. These results provide an atomic-scale insight on the dynamic process of solid/solid interface, which has implications in thin-film growth and advanced nanomanufacturing.

Tuning microstructure and enhancing corrosion property of Ti-6Al-3Nb-2Zr-1Mo alloy through electron beam surface melting

Herein, we employ electron beam surface melting (EBSM) technology to process Ti-6Al-3Nb-2Zr-1Mo alloys and compare their microstructure and corrosion performance with wrought counterparts. The mechanism of microstructural evolution has been illustrated. The EBSM sample exhibits a better corrosion resistance than the wrought one, which can be ascribed to the formation of a relatively more stable passive film due to a higher fraction of phase boundaries induced by the fine α′-phase, and the alleviated heterogeneous distribution of compositions between α (α′)- and β-phases stemming from rapid cooling during EBSM process, further leading to the absence of strong galvanic-corrosion between different phases.

Cherenkov Maser Amplifier

A Cherenkov maser amplifier (CMA) for generating high-power levels over a wide frequency range is proposed, analyzed, and numerically simulated. The CMA is a wideband amplifier consisting of an annular relativistic electron beam in a cylindrical waveguide, having an inner conductor and outer layer of dielectric material all enclosed by an outer conductor. The interaction between the hybrid TEM/TM subluminal mode of the waveguide and the relativistic electron beam leads to amplification over a wide range of input frequencies in the gigahertz regime. The interaction is analyzed and simulated in the linear and nonlinear regimes. We show that conversion efficiencies can be enhanced by spatially tapering the dielectric waveguide. In addition, by premodulating the electron beam, efficiencies can be further enhanced and saturation distances reduced. Conversion efficiencies greater than 25% have been simulated by premodulating the electron beam and/or spatially tapering the dielectric waveguide over distances of a few meters. Simulation examples indicate that the ultrawideband CMA configuration operating in the gigahertz regime can generate power levels in the gigawatt range, employing electron beams in the multi-kiloampere and low megaelectronvolt range.

A Coaxial Wire-Feed Additive Manufacturing of Metal Components Using a Profile Electron Beam in Space Application

Despite the variety of different methods of metal 3D printing on Earth, only a few of them can be realized in space. Processes that employ electron beam as a heat source and wire as a consumable material is among the most promising methods for these applications. But to date, such processes still have not been implemented in actual space operation, mainly due to the low accuracy and resolution of these 3D printed products that require significant post-processing for their intended use. Large and heavy hardware employed in these processes is another significant problem. xBeam 3D Metal Printing is the electron beam DED-wire additive manufacturing technology that has already demonstrated the capability to produce high-quality parts with high productivity on terrestrial relatively lightweight and compact hardware. xBeam process employs a profile electron beam generated by low-voltage gas-discharge electron beam guns combined with the coaxial wire feed to provide excellent control of metallurgy processes in the melt pool and around it during deposition. Realized metallurgy conditions are the crucial factor in providing the combination of high accuracy and resolution with good metal structure and properties. Moreover, maintaining such metallurgy conditions does not require gravity—only cohesion/adhesion forces and surface tension forces are involved. This fact suggests good prospects for using the xBeam 3D Metal Printing in space applications. In addition, the method opens several unique technological opportunities that are important in space exploration, including the nonstick deposition technique allowing the production of "ready-to-use" parts, surface glazing able to substitute machining, recycling of the metal waste directly into wire for 3D printing, and others. The article presents technical solutions for implementing 3D printing and related processes in space conditions and analyzes the metallurgical aspects of the technology using titanium alloy Ti-6Al-4V as an example.

First demonstration of robust tri-gate β-Ga2O3 nano-membrane field-effect transistors

Nano-membrane tri-gate β-gallium oxide (β-Ga2O3) field-effect transistors (FETs) on SiO2/Si substrate fabricated via exfoliation have been demonstrated for the first time. By employing electron beam lithography, the minimum-sized features can be defined with the footprint channel width of 50 nm. For high-quality interface between β-Ga2O3 and gate dielectric, atomic layer-deposited 15 nm thick aluminum oxide (Al2O3) was utilized with tri-methyl-aluminum (TMA) self-cleaning surface treatment. The fabricated devices demonstrate extremely low subthreshold slope (SS) of 61 mV dec−1, high drain current (I DS) ON/OFF ratio of 1.5 × 109, and negligible transfer characteristic hysteresis. We also experimentally demonstrated robustness of these devices with current–voltage (I–V) characteristics measured at temperatures up to 400 °C.

Dimensional constraints favour high temperature anatase phase stability in TiO2 nanorods

High temperature stable anatase phase TiO2 nanostructures have the potential to advance the fields such as photocatalysis, solar cells and batteries. However, it is challenging to grow TiO2 nanostructures that can retain the anatase phase at high temperatures. Here, we report slanted TiO2 nanorods grown on Si substrates by glancing angle deposition technique employing electron beam evaporation to showcase the anatase phase stability up to 800 °C. FESEM surface morphology shows that the nanorods started deforming above 600 °C and collapsed at 800 °C. We carried out image processing of the nanorods assembly and quantified the deformation with annealing temperature. The x-ray diffraction and Raman spectroscopy utilized for the phase information showed that the anatase phase is stable even at 800 °C. Further, we have studied the effect of deformation on wettability of the nanorods system and found that annealed samples are superhydrophilic. Remarkably, the annealed TiO2 nanorods have transformed to hydrophobic when kept in the dark storage due to the structural contribution to contact angle rather than surface energy. Notably, the hydrophobicity increases with time, which was studied for 25 months. The stable high temperature anatase phase could find application in the solar cells, photocatalysis, smart windows, self-cleaning coatings, etc.

Photodetecting properties of single CuO\u2013ZnO core\u2013shell nanowires with p\u2013n radial heterojunction

CuO–ZnO core–shell radial heterojunction nanowire arrays were obtained by a simple route which implies two cost-effective methods: thermal oxidation in air for preparing CuO nanowire arrays, acting as a p-type core and RF magnetron sputtering for coating the surface of the CuO nanowires with a ZnO thin film, acting as a n-type shell. The morphological, structural, optical and compositional properties of the CuO–ZnO core–shell nanowire arrays were investigated. In order to analyse the electrical and photoelectrical properties of the metal oxide nanowires, single CuO and CuO–ZnO core–shell nanowires were contacted by employing electron beam lithography (EBL) and focused ion beam induced deposition (FIBID). The photoelectrical properties emphasize that the p–n radial heterojunction diodes based on single CuO–ZnO core–shell nanowires behave as photodetectors, evidencing a time-depending photoresponse under illumination at 520 nm and 405 nm wavelengths. The performance of the photodetector device was evaluated by assessing its key parameters: responsivity, external quantum efficiency and detectivity. The results highlighted that the obtained CuO–ZnO core–shell nanowires are emerging as potential building blocks for a next generation of photodetector devices.

High current density electron emission from an electrodeposited metal nanowire array

High-current electron field emitters are of interest for many applications, but state-of-the-art devices suffer from limitations such as high turn-on macroscopic field, low macroscopic current density, poor emission stability, and short lifetime. Field emitter arrays with a high spatial density of uniform emitters have the potential to address these problems. This work presents the process development, fabrication, and testing of a novel field emitter array. The authors employed electron beam lithography and templated electrodeposition to fabricate a high spatial density array of metallic nanowires, resulting in electron emission with high macroscopic current density (2 A/cm2) and low turn-on macroscopic field (4.35 V/μm). Templated electrodeposition of metallic nanowire arrays is a promising method for producing high performance field emitters.

Enhanced physicochemical properties of ZnTe thin films as potential buffer layer in solar cell applications

The Cd-based solar cells possess rear contact problem in superstrate device architecture, which may be eliminated by inserting a suitable buffer layer of zinc telluride (ZnTe) films of appropriate thickness between CdTe absorber and Cu/Au metal contacts. The present work meticulously reports the influence of annealing on the physicochemical properties of ZnTe thin films where ZnTe films were grown employing electron beam thermal evaporation technique and subsequently annealed for 1 h in air ambient and vacuum in 100–300 °C temperature range with an interval of 100 °C. Structural analysis reveals that as-grown and air/vacuum annealed ZnTe films have (111) preferred reflection with zinc blende structure of cubic phase (except 300 °C air annealed films) and grain size is boosted from 22 to 40 nm with annealing. The direct optical energy band gap is estimated in range of 2.25–2.84 eV and 2.65–2.87 eV for air and vacuum annealing, respectively. The contacts between the film surface and the TCO layer showed ohmic behavior as revealed by the I–V characteristics. The EDS results confirmed ZnTe thin film deposition and FESEM micrographs of air annealed films demonstrated the grain growth. The AFM images of vacuum annealed films showed hill-like topographies where hill density and RMS surface roughness reduced with annealing. The findings warrant that 100 °C air annealed ZnTe thin films could be employed as an efficient buffer layer and rear contact material to the Cd-based solar cell devices.