Electron Beam Reduction Research Articles

High Resolution Surface Modification of WS2 via Plasma Oxidation and Electron Beam Reduction

High Resolution Surface Modification of WS2 via Plasma Oxidation and Electron Beam Reduction

Degradation of hexavalent chromium and naphthalene by electron beam irradiation: Degradation efficiency, mechanisms, and degradation pathway

Heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) in industrial wastewater have attracted much attention due to their damage to the environment and the human body. Studies have shown that there may be interactions between PAHs and HMs, leading to enhanced toxicity of both pollutants. It has been shown that traditional methods are difficult to treat a combination of PAHs and HMs simultaneously. This paper presented an innovative method for treating PAHs and HMs compound pollutants by electron beam irradiation and achieved the removal of the compound pollutants using a single means. Experiments showed that the absorbed dose at 15 kGy could achieve 100% degradation of NAP and 90% reduction of Cr (Ⅵ). This article investigated the effects of electron beam removal of PAHs and HMs complex contaminants in various water environmental matrices. The experimental results showed that the degradation of NAP followed the pseudo-first-order dynamics, and the degradation of NAP was more favorable under neutral conditions. Inorganic ions and water quality had little effect on NAP degradation. For electron beam reduction of Cr (Ⅵ), alkaline conditions were more conducive to reducing Cr (Ⅵ). Especially, adding K2S2O8 or HCOOH achieved 99% reduction of Cr (Ⅵ). Experiments showed that •OH achieve the degradation of NAP, and eaq− achieve the reduction of Cr (Ⅵ). The results showed that the degradation of NAP was mainly achieved by benzene ring opening, carboxylation and aldehyde, which proved that the degradation of NAP was mainly caused by •OH attack. The toxicity analysis results showed that the electron beam could significantly reduce the toxicity of NAP, and the toxicity of the final product was much lower than NAP, realizing the harmless treatment of NAP. The experimental results showed that electron beam irradiation has faster degradation rates and higher degradation efficiency for NAP and Cr (Ⅵ) compared to other reported treatment methods.

Quantitative, Spectro-kinetic Analysis of Oxygen in Electron-Beam Sensitive, Multimetallic Oxide Nanostructures.

The oxygen stoichiometry of hollandite, KxMnO2-δ, nanorods has been accurately determined from a quantitative analysis of scanning-transmission electron microscopy (STEM) X-Ray Energy Dispersive Spectroscopy (XEDS) experiments carried out in chrono-spectroscopy mode. A methodology combining 3D reconstructions of high-angle annular dark field electron tomography experiments, using compressed-sensing algorithms, and quantification through the so-called ζ-factors method of XEDS spectra recorded on a high-sensitivity detector has been devised to determine the time evolution of the oxygen content of nanostructures of electron-beam sensitive oxides. Kinetic modeling of O-stoichiometry data provided K0.13MnO1.98 as overall composition for nanorods of the hollandite. The quantitative agreement, within a 1% mol error, observed with results obtained by macroscopic techniques (temperature-programmed reduction and neutron diffraction) validate the proposed methodology for the quantitative analysis, at the nanoscale, of light elements, as it is the case of oxygen, in the presence of heavy ones (K, Mn) in the highly compromised case of nanostructured materials which are prone to electron-beam reduction. Moreover, quantitative comparison of oxygen evolution data measured at macroscopic and nanoscopic levels allowed us to rationalize beam damage effects in structural terms and clarify the exact nature of the different steps involved in the reduction of these oxides with hydrogen.

Characterization of the Native Oxide Shell of Copper Metal Powder Spherical Particles.

The native oxide layer that forms on copper (Cu) metal spherical particle surfaces under ambient handling conditions has been shown to have a significant effect on sintering behavior during microwave heating in a previous study, where an abnormal expansion was observed and characterized during sintering of Cu compacts using reducing gases. Because microwave (MW) heating is selective and depends greatly on the dielectric properties of the materials, this thin oxide layer will absorb MW energy easily and can consequently be heated drastically starting from room temperature until the reduction process occurs. In the current study, this oxide ceramic layer was qualitatively and quantitatively characterized using the carrier gas hot extraction (CGHE) method, Auger electron spectroscopy (AES), and a dual-beam focused ion beam (FIB)/scanning electron microscope (SEM) system that combines both FIB and SEM in one single instrument. Two different commercial gas-atomized spherical Cu metal powders with different particle sizes were investigated, where the average oxygen content of the powders was found to be around 0.575 wt% using the CGHE technique. Furthermore, AES spectra along with depth profile measurements were used to qualitatively characterize this oxide layer, with only a rough quantitative thickness approximation due to method limitations and the electron beam reduction effect. For the dual-beam FIB-SEM system, a platinum (Pt) coating was first deposited on the Cu particle surfaces prior to any characterization in order to protect and to preserve the oxide layer from any possible beam-induced reduction. Subsequently, the Pt-coated Cu particles were then cross-sectioned in the middle in situ using an FIB beam, where SEM micrographs of the resulted fresh sections were characterized at a 36° angle stage tilt with four different detector modes. Quantitative thickness characterization of this native oxide layer was successfully achieved using the adapted dual-beam FIB-SEM setup with more accuracy. Overall, the native Cu oxide layer was found to be inhomogeneous over the particles, and its thickness was strongly dependent on particle size. The thickness ranged from around 22–67 nm for Cu powder with a 10 µm average particle size (APS) and around 850–1050 nm for one with less than 149 µm.

Environment-Dependent Electron Beam Reduction of Rutile Nanocrystals at High Temperatures

Environment-Dependent Electron Beam Reduction of Rutile Nanocrystals at High Temperatures

Electron Beam Effects on Oxide Thin Films-Structure and Electrical Property Correlations.

In situ transmission electron microscope (TEM) characterization techniques provide valuable information on structure-property correlations to understand the behavior of materials at the nanoscale. However, understanding nanoscale structures and their interaction with the electron beam is pivotal for the reliable interpretation of in situ/ex situ TEM studies. Here, we report that oxides commonly used in nanoelectronic applications, such as transistor gate oxides or memristive devices, are prone to electron beam induced damage that causes small structural changes even under very low dose conditions, eventually changing their electrical properties as examined via in situ measurements. In this work, silicon, titanium, and niobium oxide thin films are used for in situ TEM electrical characterization studies. The electron beam induced reduction of the oxides turns these insulators into conductors. The conductivity change is reversible by exposure to air, supporting the idea of electron beam reduction of oxides as primary damage mechanism. Through these measurements we propose a limit for the critical dose to be considered for in situ scanning electron microscopy and TEM characterization studies.

Electron beam reduction induced self-assembly growth of Co/CoO nanocomposite materials

Electron beam irradiation (EBI) technology has been widely used in industrial fields during the welding process, and the instantaneous high temperature produced during this process is a significant advantage for the synthesis of metallic materials. Here, we report a method to manufacture metal/oxide nanocomposite materials by EBI using oxide films. The CoO films are first prepared by a pulsed-laser deposition technique, and the as-prepared films are treated by EBI with different electron doses. CoO can be controllably reduced to metallic Co, and a Co/CoO nanocomposite is produced with a large number of oxygen vacancies after EBI. The self-assembled well-dispersed Co nanoparticles are formed on the film surface, and their sizes can be controlled by the electron dose and irradiation time. The obtained Co/CoO composited nanoparticle films exhibit an exchange bias effect, and their blocking temperature can be modified by variations in the electron dose and time.

Localized conductive patterning via focused electron beam reduction of graphene oxide

We report on a method for “direct-write” conductive patterning via reduction of graphene oxide (GO) sheets using focused electron beam induced deposition (FEBID) of carbon. FEBID treatment of the intrinsically dielectric graphene oxide between two metal terminals opens up the conduction channel, thus enabling a unique capability for nanoscale conductive domain patterning in GO. An increase in FEBID electron dose results in a significant increase of the domain electrical conductivity with improving linearity of drain-source current vs. voltage dependence, indicative of a change of graphene oxide electronic properties from insulating to semiconducting. Density functional theory calculations suggest a possible mechanism underlying this experimentally observed phenomenon, as localized reduction of graphene oxide layers via interactions with highly reactive intermediates of electron-beam-assisted dissociation of surface-adsorbed hydrocarbon molecules. These findings establish an unusual route for using FEBID as nanoscale lithography and patterning technique for engineering carbon-based nanomaterials and devices with locally tailored electronic properties.

Silicon Nanocrystals Synthesized from Silicon Tetrachloride Using Electron Beam Reduction Reaction#

Silicon nanocrystals (Si NCs) were synthesized by the electron beam reduction reaction (EBRR). Silicon tetrachloride (SiCl4 ), isopropyl alcohol (IPA), and toluene were used as the silicon source, radical scavenger, and solvent, respectively. Three types of sample were prepared: from a solution of SiCl4 and IPA under irradiation by an electron beam (e‐beam) with energy, current, and dose of 1 MeV, 0.2 mA, and 300 kGy, respectively, and from the reactants (SiCl4 ‐only or SiCl4 + IPA) under no e‐beam irradiation. New features in the ultraviolet–visible absorption and photoluminescence spectroscopies for the case of e‐beam irradiation were attributed to the formation of the Si NCs, as confirmed by fast Fourier transform processed image in field‐emission transmission electron microscopy analysis. The possibility of the formation of the Si NCs was also validated by the Gibbs free energy calculations of the proposed reaction mechanism for EBRR of the SiCl4 precursor.

Mechanoluminescence of Persistent Luminescent SrAl$lt;inf$gt;2$lt;/inf$gt;O$lt;inf$gt;4$lt;/inf$gt;: (Eu$lt;sup$gt;2+$lt;/sup$gt;, Dy$lt;sup$gt;3+$lt;/sup$gt;) Material Prepared by Electron Beam Reduction

Long persistent luminescent SrAl2O4: (Eu, Dy) was prepared by electron beam reduction. The asprepared material was mechanically ball-milled into fine powder, and the powder was mixed with wear resistant epoxy resin. Then, the epoxy resin mixed persistent luminescent was coated on quartz glass plate by screen printing with thickness of about 1000 nm. The mechanoluminescent properties of the as-persistent luminescence film was characterized by falling ball impact technique with a homemade device for measuring mechanoluminescence intensity based on a single avalanche diode and a pico-amper meter. It is found that electron beam reduced SrAl2O4: (Eu, Dy) shows strong mechanoluminescence with high signal/background ratio of 1.25 and high signal/noise ratio. Further study found that intensity of the mechanoluminescence produced was proportional to exponential of the initial height of the ball (i.e., the final kinetic energy of the ball before impact) before falling down, and a decay curve was similar to that of persistent photoluminescence. These results indicate that mechanoluminescence is caused by impact energy of the ball which promotes electrons into traps, and then release via normal long persistent luminescent.

Electron Beam Reduction Method for Preparing the Catalyst Layer in the Growth of Carbon Nanotubes

In this paper, electron beam (e-beam) reduction method is applied for the catalyst layer preparation in the growth of carbon nanotubes (CNTs). A hot cathodic electron beam facility was employed to electron bombarding of catalyst layer before stage of CNTs growth. This new method leads to reducing the diameter of particles via sputtering and evaporating the surface of catalyst. The growth of CNTs was performed on the Fe catalyst layer with SiO2 substrate in an environment of different mixed gases (H2, NH3 and C2H2) by thermal chemical vapor deposition (TCVD) system. The morphology of the electron beam reduced catalyst particles were probed by atomic force microscopy (AFM). All samples were analyzed by scanning electron microscopy (SEM) before and after growth of CNTs. SEM analyses clarified that the catalyst grains have been smaller under effect of electron beam bombardment.

Direct in situ determination of the mechanisms controlling nanoparticle nucleation and growth.

Although nanocrystal morphology is controllable using conventional colloidal synthesis, multiple characterization techniques are typically needed to determine key properties like the nucleation rate, induction time, growth rate, and the resulting morphology. Recently, researchers have demonstrated growth of nanocrystals by in situ electron beam reduction, offering direct observations of single nanocrystals and eliminating the need for multiple characterization techniques; however, they found nanocrystal morphologies consistent with two different growth mechanisms for the same electron beam parameters. Here we show that the electron beam current plays a role analogous to the concentration of reducing agent in conventional synthesis, by controlling the growth mechanism and final morphology of silver nanocrystals grown via in situ electron beam reduction. We demonstrate that low beam currents encourage reaction limited growth that yield nanocrystals with faceted structures, while higher beam currents encourage diffusion limited growth that yield spherical nanocrystals. By isolating these two growth regimes, we demonstrate a new level of control over nanocrystal morphology, regulated by the fundamental growth mechanism. We find that the induction threshold dose for nucleation is independent of the beam current, pixel dwell time, and magnification being used. Our results indicate that in situ electron microscopy data can be interpreted by classical models and that systematic dose experiments should be performed for all future in situ liquid studies to confirm the exact mechanisms underlying observations of nucleation and growth.

Sub-oxide-to-metallic, uniformly-nanoporous crystalline nanowires by plasma oxidation and electron reduction

Sub-oxide-to-metallic highly-crystalline nanowires with uniformly distributed nanopores in the 3 nm range have been synthesized by a unique combination of the plasma oxidation, re-deposition and electron-beam reduction. Electron beam exposure-controlled oxide → sub-oxide → metal transition is explained using a non-equilibrium model.

Electron-Beam-Induced Deposition of Platinum from a Liquid Precursor

We demonstrate here the first focused electron-beam-induced deposition (EBID) of nanostructures using a liquid precursor. We have deposited sub-50 nm platinum (Pt) wires and dots from a dilute, aqueous solution of chloroplatinic acid. Existing EBID processes rely on the electron-beam stimulated decomposition of gaseous precursors; as a result, the deposits are highly contaminated (up to 75 at. % carbon or 60 at. % phosphorus for Pt processes). In contrast, we show that deposition of platinum by electron-beam reduction of platinum ions from solution leads to high-purity deposits (approximately 10 at. % chlorine contamination) at rates at least ten times higher than those obtained with other platinum precursors. Liquid-phase EBID offers a new route to deterministic, three-dimensional, nanometer-scale structures composed of multiple materials without complex multistep processing. Thus, it may prove important for prototyping and low-volume production of nanoscale devices and for repair and modification of nanoscale masks and templates used in high-volume production.

Electrochemical Reduction of Uniformly Dispersed Pt and Ag Nanodots on Carbon Fiber Electrodes

Electrochemical characterization of the uniformly dispersed Pt and Ag nanodots synthesized after in situ scalable electron‐beam reduction on copper grid and carbon‐fiber electrode is demonstrated. By employing plasma pretreatment to produce functional organosilicon micronetworks‐based reaction sites on copper grid, the size and standard deviation of the electrochemically reduced metallic nanodots can be strictly confined. When detuning the accelerating voltage of electron‐beam from 3 to 120 kV, the reshaped nanodot diameter enlarges from 12.7 ± 0.8 to 18.3 ± 3.6 nm due to the gradual self‐aggregation. In comparison with sputtering method, the electroactivity of Pt nanodot covered carbon fiber electrode obtained after electron‐beam reduction exhibits a larger electroactive surface (Spt) of 16.56 cm2/mg. The electron‐beam reduction provides a better dispersion of the reduced Pt nanodots based catalysts on carbon‐fiber electrode, promoting the utilization efficiency of these nanoscale catalyst (defined as the ratio of electroactive to geometric area) from 2.5% to 7%.

Electron-beam reduction method for preparing electrocatalytic particles for membrane electrode assemblies (MEA)

A new method, the electron-beam (e-beam) reduction method, is presented for fuel cell electrocatalytic particle preparation. The method utilizes the idea of reducing ions of the catalyst species right on the carbon cloth fibers and the multi walled carbon nano tubes (MWNTs) via direct electron-beam bombardment. The morphology of the electron-beam reduced catalyst particles is presented to show that the catalyst particles were dispersed in an equal and homogeneous manner within the MWNTs/carbon cloth electrode carriers, and imply that the electroactive surface area of the e-beam reduced catalysts should assume a larger value than those from currently reported methods. With the Pt (catalyst) loadings being controlled, data obtained from electrochemical and polarization tests show that the electrodes and membrane electrode assemblies (MEA) prepared from the e-beam reduction have larger active surface areas and better working performances than those prepared from the sputtering method; the quantitative results show good consistency with the qualitative morphology images.

Gold Nanoparticles Generated by Electron Beam Lithography of Gold(I)−Thiolate Thin Films

Patterned arrays of gold nanoparticles in two dimensions were prepared by the electron beam reduction and subsequent thermolysis of gold(I)−thiolate complexes on silicon surfaces. The array line widths are <50 nm and they are composed of small gold nanoparticles (average diameters from 2 to 4.5 nm). Variation in the electron beam dose allows for the variation of the interparticle distances in a given sample.

Determination of the uranium valence state in the brannerite structure using EELS, XPS, and EDX

In this study, the valence states of uranium in synthetic and natural brannerite samples were studied using a combination of transmission electron microscopy-electron energy loss spectroscopy, scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX), and X-ray photoelectron spectroscopy (XPS) techniques. We used a set of five (UO2, CaUO4, SrCa2UO6, UTi2O6, and Y0.5U0.5Ti2O6) U standard samples, including two synthetic brannerites, to calibrate the EELS branching ratio, M5/(M4 +M5), against the number of f electrons. The EELS data were collected at liquid nitrogen temperature in order to minimise the effects of electron beam reduction of U6+ and U5+. Test samples consisted of three additional synthetic brannerites (Th0.7U0.3Ti2O6, Ca0.2U0.8Ti2O6, and Th0.55U0.3Ca0.15Ti2O6) and three natural brannerites from different localities. The natural brannerite samples are all completely amorphous, due to cumulative alpha decay events over geological time periods (24–508 Ma). Our U valence calibration results are in reasonable agreement with previous work, suggesting possibly a non-linear relationship between the branching ratio and the number of f electrons (and hence the average valence state) of U in solids. We found excellent agreement between the nominal valence states of U and the average valence states determined directly by EELS and estimated by EDX analysis (with assumptions regarding stoichiometry) in two of the three synthetic brannerite test samples. The average U oxidation states of the five synthetic brannerite samples, as derived from XPS analyses, are also in good agreement with those determined by other techniques. The average valence states of U in three amorphous (metamict) natural brannerite samples with alpha decay doses ranging from 3.6×1016 to 6.9×1017 α/mg were found to be 4.4, 4.7, and 4.8, consistent with the presence of U5+ and/or U6+ as well as U4+ in these samples. These results are in general agreement with previous wet chemical analyses of natural brannerite. However, the average valence states inferred by SEM-EDX for two of the natural brannerite samples do not show satisfactory agreement with the EELS determined valence. This may be due to the occurrence of OH− groups, cation vacancies, anion vacancies, or excess oxygen in the radiation-damaged structure of natural brannerite.

Chemical and Electron Beam Reduction of Vanadium Oxides Monitored by EELS and NEXAFS

Abstract The application of modern transmission electron microscopes (TEM) in catalytic research has accelerated the progress in understanding the mechanism of catalytic reactions. For instance, using environmental TEM, the novel glide shear defect process was revealed as an efficient mechanism for the release of the structural oxygen of vanadyl pyrophosphate in the n-butane oxidation [1]. On the other hand, electron energy-loss spectroscopy (EELS), which is nowadays commercially available on modern TEM, appears unknown in the catalytic community. in fact, core-loss EELS is a powerful tool to identify the chemical state of elements and to study the modification of this sate in various compounds. Fig.l shows EELS-spectra of various vanadium oxides in which the oxidation state of vanadium varies from 2+ (VO) to 5+ (V2O5). The first two features, marked as V L3 and V L2 edges, are attributed to the excitations from V 2p3/2and V 2p1/2core levels to the unoccupied V 3dstates, respectively.

Electron beam reduction of sodium-containing glass surfaces

Abstract Soda-silicate and soda-lime silicate glass surfaces were irradiated by a 3 keV, 0.50 mA/cm2 electron beam and then characterized by X-ray photoelectron spectroscopy. Sodium is depleted from the bombarded surfaces and the non-bridging-to-bridging oxygen ratios also decrease, in agreement with previous studies. Metallic sodium forms on the surfaces of irradiated binary glasses, whereas no reduced sodium can be detected on electron bombarded CaO-containing glass surfaces.