Direct Electron Beam Research Articles

Nanoscale Electron Beam Patterning of PEDOT:PSS Free‐Standing Films for Enhanced Thermoelectric Performance

The growing demand for flexible, lightweight, and highly processable electronic devices makes high‐functionality conducting polymers such as poly (3,4‐ethylene dioxythiophene): polystyrene sulfonate (PEDOT:PSS) an attractive alternative to conventional inorganic materials for various applications including thermoelectrics. However, considerable improvements are necessary to make conducting polymers a commercially viable choice for thermoelectric applications. This study explores nanopatterning as an effective and unique strategy for enhancing polymer functionality to optimize thermoelectric parameters, such as electrical conductivity, Seebeck coefficient, and thermal conductivity. Introducing nanopatterning into thermoelectric polymers is challenging due to intricate technical hurdles and the necessity for individually manipulating the interdependent thermoelectric parameters. Here, array nanopatterns with different pattern spacings are imposed on free‐standing PEDOT:PSS films using direct electron beam irradiation, thereby achieving selective control of electrical and thermal transport in PEDOT:PSS. Electron beam irradiation transformed PEDOT:PSS from a highly ordered quinoid to an amorphous benzoid structure. Optimized pattern spacing resulted in a remarkable 70% reduction in thermal conductivity and a 60% increase in thermoelectric figure of merit compared to non‐patterned PEDOT:PSS. The proposed nanopatterning methodology demonstrates a skillful approach to precisely manipulate the thermoelectric parameters, thereby improving the thermoelectric performance of conducting polymers, and promising utilization in cutting‐edge electronic applications.

Direct electron beam writing of silver using a β-diketonate precursor: first insights.

Direct electron beam writing is a powerful tool for fabricating complex nanostructures in a single step. The electron beam locally cleaves the molecules of an adsorbed gaseous precursor to form a deposit, similar to 3D printing but without the need for a resist or development step. Here, we employ for the first time a silver β-diketonate precursor for focused electron beam-induced deposition (FEBID). The used compound (hfac)AgPMe3 operates at an evaporation temperature of 70-80 °C and is compatible with commercially available gas injection systems used in any standard scanning electron microscope. Growth of smooth 3D geometries could be demonstrated for tightly focused electron beams, albeit with low silver content in the deposit volume. The electron beam-induced deposition proved sensitive to the irradiation conditions, leading to varying compositions of the deposit and internal inhomogeneities such as the formation of a layered structure consisting of a pure silver layer at the interface to the substrate covered by a deposit layer with low silver content. Imaging after the deposition process revealed morphological changes such as the growth of silver particles on the surface. While these effects complicate the application for 3D printing, the unique deposit structure with a thin, compact silver film beneath the deposit body is interesting from a fundamental point of view and may offer additional opportunities for applications.

Mass Flows in Expanding Coronal Loops

An expansion of the cross-sectional area directly impacts the mass flow along a coronal loop and significantly alters the radiative and hydrodynamic evolution of that loop as a result. Previous studies have found that an area expansion from the chromosphere to the corona significantly lengthens the cooling time of the corona and appears to suppress draining from the corona. In this work, we examine the fluid dynamics to understand how the mass flow rate, the energy balance, and the cooling and draining timescales are affected by a nonuniform area. We find that in loops with moderate or large expansion (cross-sectional area expansion factors of 2, 3, 10, 30, 100 from the photosphere to the apex), impulsive heating, for either direct thermal heating or electron beam heating, induces a steady flow into the corona, so that the coronal density continues to rise during the cooling phase, whereas a uniform loop drains during the cooling phase. The induced upflow carries energy into the corona, balancing the losses from thermal conduction, and continues until thermal conduction weakens enough so that it can no longer support the radiative losses of the transition region. As a result, the plasma cools primarily radiatively until the onset of catastrophic collapse. The speed and duration of the induced upflow both increase in proportion to the rate of area expansion. We argue that observations of blueshifted spectral lines, therefore, could place a constraint on a loop’s area expansion.

Hot isostatic pressing as an alternative thermo-mechanical treatment for metallic full-arch implant-supported frameworks obtained by additive and subtractive manufacturing technology: Vertical and horizontal fit, screw removal torque, and stress analysis.

To assess vertical and horizontal fit, screw removal torque, and stress analysis (considered biomechanical aspects) of full-arch implant frameworks manufactured in Ti-6Al-4V through milling, and additive manufacturing Direct Metal Laser Sintering (DMLS) and Electron Beam Melting (EBM), and the effect of the thermo-mechanical treatment Hot Isostatic Pressing (HIP) as a post-treatment after manufacturing. Maxillary full-arch implant frameworks were made by milling, DMLS, and EBM. The biomechanical assessments were screw removal torque, strain-gauge analyses, and vertical and horizontal marginal fits. The vertical fit was assessed by the single-screw test and with all screws tightened. All frameworks were submitted to a standardized HIP cycle (920°C, 1000bar pressure, 2h), and the tests were repeated (α = 0.05). At the initial time, milled frameworks presented higher screw removal torque values, and DMLS and EBM frameworks presented lower levels of strain. Using the single-screw test, milled and DMLS frameworks presented higher vertical fit values, and with all screws tightened and horizontally, higher fit values were found for milled frameworks, followed by DMLS and EBM. After HIP, milling and EBM frameworks presented higher screw removal torque values; the lowest strain values were found for EBM. Using the single-screw test, milled and DMLS frameworks presented higher vertical fit values, and with all screws tightened and horizontally no differences were found. DMLS and EBM full-arch frameworks presented adequate values of screw removal torque, strain, and marginal fit, although the worst values of marginal fit were found for EBM frameworks. The HIP cycle enhanced the screw removal torque of milled and EBM frameworks and reduced the strain values of milled frameworks. The HIP represents a reliable post-treatment for Ti-6Al-4V dental prostheses produced by milling and EBM technologies.

Agresija NATO-a na SRJ 1999. godine - provera efikasnosti novih borbenih sredstava

Introduction/purpose: During the 1999 NATO attack on Yugoslavia, three new weapons were used and tested for the first time. The first is the strategically invisible B-2 bomber, the second is the new JDAM (Joint Direct Attack Ammunition) and the third is the "soft bomb", or the blackout bomb, made of thin electrically conductive fibers. The aim of the paper is to present the new combat devices used during the aggression on the FRY and to quantitatively detect the elements of electrically conductive fibers. The paper also presents the lawsuit of the Federative Republic of Yugoslavia (FRY) to the International Criminal Tribunal for the former Yugoslavia (ICTY) in The Hague. The lawsuit was rejected Methods: Physical and chemical analyzes of the fibers were performed. An electron microscope, SEM JSM Jeol 6610LV, was used to analyze the physicochemical characteristics of electrically conductive fibers. It provides the information on the morphology of the sample surface, resulting in a high-resolution image. The microscope is equipped with an X-ray detector (Oxford Instrumets X-Max 20 mm2) for EDS analysis (Energy Dispersive Spectroscopy). It enables the determination of the chemical composition of the material in the analyzed sample volume, based on the interaction between the directed electron beam and the sample atom. Results: The characteristics of the B-2 stealth aircraft used to bomb the FRY are shown. The JDAM bomb is an improved ordinary MK bomb with electronic devices added to guide the bomb via satellites. A semiquantitative analysis of the fibers was performed on the SEM, confirming that the metal layer of the fiber predominantly consists of aluminum, and the non-metallic layer has the highest proportion of silicon dioxide. The fiber is carcinogenic. Conclusion: In 1999, the territory of Yugoslavia was a testing ground for new combat weapons of NATO aviation - B-2 and JDAM guided bombs. Blackout bombs were dropped on the electrical power systems of Yugoslavia leaving the whole Serbia without electricity for hours. Not only was the bombing-caused environmental pollution radiological and chemical but it was also caused by glass-aluminum electrically conductive fibers as pollutants.

Fabrication of palladium-enriched metallic structures by direct focused He+ and Ne+ beam nanowriting from organometallic thin films: a comparison with Ga+ and e- beams.

A direct nanowriting procedure using helium- and neon-focused ion beams and spin-coated organometallic thin films is introduced and applied to the fabrication of Pd-enriched metallic structures in a single lithography step. This process presents significant advantages over multi-step resist-based lithography and focused beam-induced deposition using gaseous precursors, such as its simplicity and speed, respectively. The optimized process leads to Pd-rich structures with low electrical resistivity values of 141 and 152 μΩ cm under Ne+ or He+ fluences of 1000 and 5000 μC cm-2, respectively. These resistivity values correlate well with compositional and microstructural studies, indicating a high Pd metallic content in a dense structure with a few-nm grain size. The obtained results are compared to similar structures fabricated by direct electron and gallium beam nanowriting, demonstrating the full potential of nanopatterned Pd-based organometallic thin films under the most common focused charged beams. The practical applications of combining spin-coated organometallic thin films with focused beam nanowriting in micro- and nano-lithography modern procedures are also discussed in this contribution.

Lithium Dendrite Propagation in Anode-Free Lithium Metal Batteries: An in-Operando Scanning Electron Microscopic Study

In the current technological landscape, lithium metal batteries have significantly surpassed the energy density of conventional lithium-ion batteries. Therefore, The advent of anode-free lithium metal batteries (AFLMBs) offers higher energy densities.. They also provide advantages such as reduced process complexity and lower costs due to their design that eliminates the need for anode materials. Unlike the lithium-ion insertion and extraction reactions in traditional lithium-ion batteries. This makes them easier to lithium dendrite formation, which can puncture the separator or solid electrolytes, among other issues. In this work, we developed anin-operando electron microscopic technique with a unique vacuum square-cell design to ensure air-tight transfer of in-operandocells with vacuum protection into the SEM chamber. We significantly improved the imaging resolution with a windowless design, enabling the direct electron beam to focus on the electrode interfaces. Thus, real-time imaging of Li growth could be achieved via a stable current supply and controlled temperature. we systematically analyzed the Li growth and dendrite propagation behavior in AFLMBs using solid polymer electrolyte (SPE). In particular, we used polyethylene oxide (PEO)-based SPEs containing different lithium salts, namely 25wt% Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), Lithium difluoro (oxalateo)borate (LiDFOB), and Lithium bis(oxalate)borate (LiBOB), within a LiFePO4||Cu anode-free cell configuration. Under a fixed current density, Li deposition and stripping were conducted, in which the PEO-LiTFSI SPE exhibited uniform deposition with a mossy lithium dendrite morphology. In the subsequent deposition process, some branching lithium dendrites were observed. Meanwhile, PEO-LiBOB showed uneven Li deposition with needle-like dendritic formation, potentially disrupting the SPE/electrode interface and leading to safety hazards. Lastly, PEO-LiDFOB initially showed mossy lithium deposition. In contrast, a few dendritic lithium structures appeared as the deposition process continued into the intermediate and later stages. The study successfully established a novel in-situ electron microscopy observation platform isolating water and oxygen. This platform recreated the actual battery operating environment, enhancing the credibility of experimental results. Additionally, we successfully elucidated the growth mechanisms of lithium dendrites in SPE with different lithium salts in the LFP||Cu configuration. This in-situ microscope technology aims to observe the relevant mechanisms behind dynamic deposition. Understanding how this deposition affects battery performance and safety and combining it with advanced operational and ex-situ characterization techniques can further promote the development of all-solid -state batteries in the future.

The Effect of Direct Electron Beam Patterning on the Water Uptake and Ionic Conductivity of Nafion Thin Films

AbstractThe effect of electron‐beam patterning on the water uptake and ionic conductivity of Nafion films using a combination of X‐ray photoelectron spectroscopy, quartz crystal microbalance studies, neutron reflectometry, and impedance spectroscopy is reported. The aim is to further characterize the nanoscale patterned Nafion structures recently used as a key element in novel ion‐to‐electron transducers by Gluschke et al. To enable this, the electron beam patterning process is developed for large areas, achieving patterning speeds approaching 1 cm2 h−1, and patterned areas as large as 7 cm2 for the neutron reflectometry studies. It is ultimately shown that electron‐beam patterning affects both the water uptake and the ionic conductivity, depending on film thickness. Type‐II adsorption isotherm behavior is seen for all films. For thick films (≈230 nm), a strong reduction in water uptake with electron‐beam patterning is found. In contrast, for thin films (≈30 nm), electron‐beam patterning enhances water uptake. Notably, for either thickness, the reduction in ionic conductivity arising from electron‐beam patterning is kept to less than an order of magnitude. Mechanisms are proposed for the observed behavior based on the known complex morphology of Nafion films to motivate future studies of electron‐beam processed Nafion.

Surface nanocrystallization on stainless steel with high hardness induced by electron beam direct irradiation

There remains a challenge to realize the 4Cr13 stainless steel with high hardness for surface strengthening. Herein, a novel method for surface nanocrystallization of 4Cr13 stainless steel by direct electron beam irradiation was proposed. Results revealed that nano-sized grains are homogeneously distributed in the modified layer, which the average grain size was approximately 30 nm. Surface microhardness remarkably enhanced from 230 HV to 720 HV, as tripled the substrate. The high hardness was attributed to the fine-grain and dispersion strengthening that benefited from surface nanocrystallization. This study can provide a worthy insight for the surface strengthening of next generation ultrastrong stainless steel.

Ligand Size and Carbon-Chain Length Study of Silver Carboxylates in Focused Electron-Beam-Induced Deposition.

Gas-assisted focused electron-beam-induced deposition is a versatile tool for the direct writing of complex-shaped nanostructures with unprecedented shape fidelity and resolution. While the technique is well-established for various materials, the direct electron beam writing of silver is still in its infancy. Here, we examine and compare five different silver carboxylates, three perfluorinated: [Ag2(µ-O2CCF3)2], [Ag2(µ-O2CC2F5)2], and [Ag2(µ-O2CC3F7)2], and two containing branched substituents: [Ag2(µ-O2CCMe2Et)2] and [Ag2(µ-O2CtBu)2], as potential precursors for focused electron-beam-induced deposition. All of the compounds show high sensitivity to electron dissociation and efficient dissociation of Ag-O bonds. The as-deposited materials have silver contents from 42 at.% to above 70 at.% and are composed of silver nano-crystals with impurities of carbon and fluorine between them. Precursors with the shortest carbon-fluorine chain ligands yield the highest silver contents. In addition, the deposited silver content depends on the balance of electron-induced ligand co-deposition and ligand desorption. For all of the tested compounds, low electron flux was related to high silver content. Our findings demonstrate that silver carboxylates constitute a promising group of precursors for gas-assisted focused electron beam writing of high silver content materials.

Experimental studies of circular attractors in the first rf-based electron cooler

In electron coolers, under certain conditions, a circular attractor (CA) can appear in either a longitudinal or a transverse phase space of cooled ion bunches. In the presence of an attractor, ions with small amplitudes of synchrotron or betatron oscillations are getting excited rather than being damped. This effect was observed at several nonrelativistic electron coolers with a direct current electron beam. Experimental studies of circular attractors at electron coolers utilizing rf-accelerated electron bunches, where this effect becomes particularly important, are lacking. We report CA studies at the low energy RHIC electron cooler (LEReC)---the first rf-based relativistic electron cooler. We derive formulas defining conditions for a CA appearance, perform dedicated experiments, and compare the measurements' results to the theoretical predictions.

Addressing key aspects of J × B driven MeV fast electron generation in ultra-short ultra-intense laser foil interaction

Applicability of J × B mechanism of MeV fast electron generation is clearly demonstrated through observation of directed electron beam along laser propagation direction (simultaneous emission also along laser polarization/transverse directions) in the interaction of ∼25 fs laser pulse with thin foil target at an intensity of 1–7 × 1019 W/cm2. Fast electron temperature is found to be lower (higher) than ponderomotive for shorter (longer) preplasma scale lengths. Role of pre-acceleration of electrons in the rising part of the laser pulse is suggested for observed efficient J × B acceleration for p-polarization case. 2D particle in cell simulation also supports the above-mentioned observations.

Effects of Different Titanium Surfaces Created by 3D Printing Methods, Particle Sizes, and Acid Etching on Protein Adsorption and Cell Adhesion, Proliferation, and Differentiation.

The surfaces of 3D printed titanium prostheses have major impacts on the clinical performance of the prostheses. To investigate the surface effects of the products generated by 3D printed titanium on osseointegration, six surface types of titanium discs produced by the direct metal laser sintering (DMLS) and electron beam melting (EBM) methods, with two sizes of titanium particles and post-printing acid etching, were used to examine the surface topography and to explore the protein adsorption, pro-inflammatory cytokine gene expressions, and MC3T3-E1 cell adhesion, proliferation, and differentiation. The EBM-printed disc showed a stripy and smooth surface without evidence of the particles used, while the DMLS surface contained many particles. After acid etching, small particles on the DMLS surface were removed, whereas the large particles were left. Moreover, distinct proteins with low molecular weights were attached to the 3D printed titanium discs but not to the pre-printing titanium particles. The small titanium particles stimulated the highest TNF-α and IL-6 gene expressions at 24 h. The alizarin red content and osteocalcin gene expression at day 21 were the highest in the groups of acid-etched discs printed by DMLS with the small particles and by EBM. Therefore, the acid-treated surfaces without particles favor osteogenic differentiation. The surface design of 3D printed titanium prostheses should be based on their clinical applications.

Low-resistivity Pd nanopatterns created by a direct electron beam irradiation process free of post-treatment steps

The ability to create metallic patterned nanostructures with excellent control of size, shape and spatial orientation is of utmost importance in the construction of next-generation electronic and optical devices as well as in other applications such as (bio)sensors, reactive surfaces for catalysis, etc. Moreover, development of simple, rapid and low-cost fabrication processes of metallic patterned nanostructures is a challenging issue for the incorporation of such devices in real market applications. In this contribution, a direct-write method that results in highly conducting palladium-based nanopatterned structures without the need of applying subsequent curing processes is presented. Spin-coated films of palladium acetate were irradiated with an electron beam to produce palladium nanodeposits (PdNDs) with controlled size, shape and height. The use of different electron doses was investigated and its influence on the PdNDs features determined, namely: (1) thickness of the deposits, (2) atomic percentage of palladium content, (3) oxidation state of palladium in the deposit, (4) morphology of the sample and grain size of the Pd nanocrystals and (5) resistivity. It has been probed that the use of high electron doses, 30000 μC cm−2 results in the lowest resistivity reported to date for PdNDs, namely 145 μΩ cm, which is only one order of magnitude higher than bulk palladium. This result paves the way for development of simplified lithography processes of nanostructured deposits avoiding subsequent post-treatment steps.

Direct Patterning of Optoelectronic Nanostructures Using Encapsulated Layered Transition Metal Dichalcogenides.

Direct top-down nanopatterning of semiconductors is a powerful tool for engineering properties of optoelectronic devices. Translating this approach to two-dimensional semiconductors such as monolayer transition metal dichalcogenides (TMDs) is challenging because of both the small scales required for confinement and the degradation of electronic and optical properties caused by high-energy and high-dose electron radiation used for high-resolution top-down direct electron beam patterning. We show that encapsulating a TMD monolayer with hexagonal boron nitride preserves the narrow exciton linewidths and emission intensity typical in such heterostructures after electron beam lithography, allowing direct patterning of functional optical monolayer nanostructures on scales of a few tens of nanometers. We leverage this fabrication method to study size-dependent effects on nanodot arrays of MoS2 and MoSe2 as well as laterally confined electrical transport devices, demonstrating the potential of top-down lithography for nanoscale TMD optoelectronics.

Effect of V/Fe composite interlayer on the microstructure and mechanical properties of electron beam welded joints of Ta-10W and GH3128

Electron beam welding of Ta-10W and GH3128 superalloys without and with the addition of V/Fe composite interlayer was carried out to study the effect of the addition of V/Fe composite interlayer on the microstructure, mechanical properties and fracture characteristics of the welded joints. The results showed that both welded joints were well formed, with the addition of V/Fe composite interlayer having finer grains in each region. The fracture form of both welded joints are brittle fracture, fracture location are in the Ta-10W side. However, some ductile fracture features were present in the fracture of the added V/Fe composite interlayer. In direct electron beam welding, the Ta-10w side of the reaction layer there is a large number of Ta-Ni and other intermetallic compounds, which is the most important reason for its poor mechanical properties of the joint. the addition of V/Fe composite interlayer greatly reduces the tendency of intermetallic compound formation in the weld, changing the microstructure of the reaction layer, the tensile strength of the joint has been significantly increased, the maximum tensile strength of 362 MPa.

Electron-only reconnection and associated electron heating and acceleration in PHASMA

Using incoherent Thomson scattering, electron heating and acceleration at the electron velocity distribution function (EVDF) level are investigated during electron-only reconnection in the PHAse Space MApping (PHASMA) facility. Reconnection arises during the merger of two kink-free flux ropes. Both push and pull type reconnection occur in a single discharge. Electron heating is localized around the separatrix, and the electron temperature increases continuously along the separatrix with distance from the X-line. The local measured gain in enthalpy flux is up to 70% of the incoming Poynting flux. Notably, non-Maxwellian EVDFs comprised of a warm bulk population and a cold beam are directly measured during the electron-only reconnection. The electron beam velocity is comparable to, and scales with, electron Alfvén speed, revealing the signature of electron acceleration caused by electron-only reconnection. The observation of oppositely directed electron beams on either side of the X-point provides “smoking-gun” evidence of the occurrence of electron-only reconnection in PHASMA. 2D particle-in-cell simulations agree well with the laboratory measurements. The measured conversion of Poynting flux into electron enthalpy is consistent with recent observations of electron-only reconnection in the magnetosheath [Phan et al., Nature 557, 202 (2018)] at similar dimensionless parameters as in the experiments. The laboratory measurements go beyond the magnetosheath observations by directly resolving the electron temperature gain.

Accurate Local Modulation of Graphene Terahertz Metamaterials by Direct Electron Beam Irradiation

Electrical gating has been typically used for Graphene-based devices to deliver high performance with superior electrical controllability. In this study, we utilize direct electron beam irradiation to attain the electrical controllability of graphene. The newly established system combines terahertz time-domain spectroscopy (TDS) with scanning electron microscopy (SEM). We experimentally demonstrate the precise localized tuning of graphene terahertz metamaterials, as the size and position of the electron beam generated by SEM are highly controllable. Furthermore, graphene metamaterials with different chemical potentials are simulated, and the results are highly consistent with the experiments.

Development of a direct point electron beam exposure system to investigate the biological functions of subcellular domains in a living biological cell

Electron microscopy studies have demonstrated that the diameter of a focused electron beam is small enough to probe or manipulate subcellular domains of a single biological cell. Here, we report the development of a direct point electron beam irradiation system to investigate the biological functions of subcellular domains in a living cell. Subcellular structures of a single living cell cultured on a thin film can be selectively irradiated by the point electron beam generated by our system. We have demonstrated controlled beam positioning capability to selectively irradiate 500 nm size structure with a point electron beam. We determined beam irradiation parameters that did not cause irreversible plasma membrane perforation after beam exposure and the irradiation caused intracellular Ca2+ elevation in an irradiated neuronal cell. Since the neuronal cell express fine subcellular structures such as neurites, we tried to position a beam on the structure and observed a Ca2+ wave originated from the intended point, which showed that our system had enough selectivity to target a subcellular structure. Point electron beam exposure is expected to be employed for various cellular stimulation protocols, and this enables the investigation of the biological functions of subcellular domains.

3D designing of resist membrane pores via direct electron beam lithography

Formation of fluidic channels with well-defined size and shape is of critical importance for reliable resistive pulse sensing of individual objects in electrolyte solution. Here we report on a method to fabricate a pore of 3D-controlled structure. We directly sculpted a hole in a polymer resist membrane of various thickness up to 6 µm by electron beam lithography. This procedure allowed to create diverse range of thickness-to-diameter aspect ratio channels of controllable shapes from concave to convex cone profiles via the varying proximity effects under different electron dose conditions. The lithographically-defined pores were utilized to detect nanoparticles by cross-membrane ionic current that revealed optimal membrane thickness for gaining larger resistive pulse signal intensities. The present technique provides a way to design single-particle sensors for cell sorting and viral screening.