Electron Yield Research Articles

Secondary electron yield (SEY) evolution of laser processed oxygen-free high conductivity copper induced by different ultrasonic cleaning durations

Laser treated material surface has highly regular curves and greatly reduces the secondary electron yield of surface. As one of the most typically used materials in the vacuum system of particle accelerators, the surface of oxygen-free high conductivity copper (OFHC) is processed by laser. Moreover, ultrasonic cleaning can effectively remove powders and impurities produced by laser ablation. The secondary electron yield (SEY), surface morphology and surface composition of laser treated oxygen-free copper samples before and after ultrasonic cleaning were compared. Experiments were conducted by using the secondary electron yield test device, X-ray diffractometer, X-ray photoelectron spectroscopy, and scanning electron microscope to characterize the SEY, crystal structures, surface composition and surface morphology of laser-treated oxygen-free copper samples, respectively. The SEY evolution of the samples was investigated and analyzed at electron doses of 7.6 × 10−6 C mm−2: after 15-min ultrasonic cleaning, the δmax of sample #1, #2 and #3 increased from 1.09, 1.23, and 1.38 to 1.19, 1.2, and 1.63, respectively, with the maximum increase of 18.12 %. Ultrasonic cleaning could greatly reduce the accumulation of spherical particles and the fibrous or flocculent structures produced by laser processing, thereby reducing the capture of secondary electrons.

Fabrication and structure analysis of freestanding BaTiO3–CeO2 epitaxial nanocomposite membranes

Vertically aligned nanocomposite films hold the promise of making a significant contribution to the performance enhancement and multifunctional integration of flexible thin-film devices but are hindered by the difficulty of direct epitaxial growth on flexible substrates. In this work, freestanding BaTiO3–CeO2 epitaxial nanocomposite membranes were prepared by using water-soluble Sr3Al2O6 as the sacrificial buffer during film deposition. The membrane's lattice parameters as well as their epitaxial relationship, before and after its removal from the single-crystal substrates, were quantitatively measured and analyzed by combining x-ray diffraction and TEM. In addition, synchrotron soft x-ray absorption spectroscopy reveals the discrepancy in the surface and internal electron states of Ce and Ti via comparative studies in total electron yield mode and transmission mode, respectively. This work exemplified that freestanding membranes provide a convenient platform for (1) the study of in-plane lattice information of epitaxial oxide films via TEM and for (2) the comparative study of surface and internal electron band information of epitaxial oxide films.

Detection of carbon contamination in EUV multilayer mirrors based on secondary electrons

The issue of carbon contamination on the surface of extreme ultraviolet (EUV) optical elements needs to be addressed urgently. In the process of removing carbon contamination, it is necessary to detect the thickness of the carbon contaminated layer in order to avoid damage to EUV multilayer mirrors (MLMs) by overcleaning. The yield of secondary electrons (SEY) generated by the excitation of EUV photons and primary electrons has been proved to be correlated with the thickness of the carbon layer, and thus the cutoff point for carbon layer cleaning can be found by detecting the SEY. In this study, the spatial distribution and motion state of secondary electrons (SEs) in the vacuum cavity of the EUV system during the cleaning process are described, utilizing the Particle-in-cell model and Monte Carlo method, and the variation relationship between SEY and the thickness of the carbon layer is obtained. The results show that under the set conditions, the SEY generated by EUV photons is very low, but it will generate primary electrons that are 1.05 times as numerous as itself, of which 24% bombarded to the carbon layer, resulting in SEs which amount to 16% of primary electrons generation. Moreover, as the carbon layer thickness decreases to 2 nm or below, SEY increases significantly, ranging from 0.55 to 0.71. The present work is of great significance in realizing the accurate detection of the carbon layer thickness of EUV multilayer film mirrors and the recovery of the reflectivity of MLMs.

Performance evaluation of a single microchannel plate with large length-to-diameter ratio

The conventional microchannel plate (MCP) detector has found widespread application in various fields. This article focuses on investigating the performance of a single MCP with a large length-to-diameter ratio (L/D) of 80:1, particularly for single electron counting. To enhance MCP performance, alumina with a high secondary electron yield (SEY) is coated onto the MCP using atomic layer deposition (ALD). The SEYs of alumina thin films with different thicknesses are measured using a pulsing electron beam method. The 80:1 L/D MCPs operate in electron counting mode, and the optimal alumina thickness is determined through a comparative study of MCP performance before and after coating. The relationships between maximum SEY, primary electron energy, gain, peak-to-valley ratio (P/V), and pulse height resolution (PHR) are analyzed. After alumina coating, the single 80:1 MCP exhibits improved gain, P/V and PHR. The optimal P/V and PHR of a single MCP as functions of the primary electron energy align with the relationship between the SEY of the alumina coating and the primary electron energy. Additionally, the variation of DC gain with extracted charge is investigated. This article provides valuable insights for parameter selection in achieving the optimal working state of MCP and explores the potential application of single electron counting using a single MCP.

Suppression of dielectric surface flashover induced by strong electromagnetic field at multiple spatial scales based on above/sub-surface discharge development mechanisms

Spacecraft charging and electrostatic discharging (ESD) are prone to occur in harsh space environments. In particular, in the case of coupling strong electromagnetic field (EMF), ESD damages may occur at a low charging potential, posing a serious threat to on-orbit spacecraft missions. To investigate the mechanism and the pertinent suppression method for vacuum surface discharge induced by EMF, a specially-designed platform for EMF-induced surface discharge was set up. Surface structures with various spatial scales were created separately by using different surface engineering strategies, including direct fluorination, mechanical polishing, and 3D-printed grooving. The resulting surface physicochemical characteristics of the samples were examined. Furthermore, the surface discharge characteristics for different methods induced by strong EMF were systematically analyzed, considering the surface trap state distribution and secondary electron yield (SEY). The findings indicate that the proposed surface treatment methods demonstrate varying levels of improvement in mitigating EMF-induced discharge. Direct fluorination was found to produce lower SEY and to accelerate surface charge dissipation due to an elevated shallow trap density, making it favorable for suppressing the EMF-induced discharge. In addition, suitable surface roughness and groove size can effectively impede the development of the multipactor, thereby preventing EMF-induced discharge. This research is expected to provide valuable insights into the protection design of EMF-induced discharge on spacecraft.

Pulse Duration Dependence of Infrared Laser-Induced Secondary Electron Yield Reduction of Copper Surfaces

Pulse Duration Dependence of Infrared Laser-Induced Secondary Electron Yield Reduction of Copper Surfaces

XAS studies of vanadium pentoxide thin films

Thin films of 200 nm of VOx RF magnetron sputtered on the SiO2 glass and Si substrates were studied with X-ray Absorption Spectroscopy in the XANES range of the oxygen K and vanadium L2,3 edges. The total electron yield (TEY) detection mode was used. The spectra were collected at several temperatures between room temperature and 300 °C for the unpolarized and linearly polarized beam to study polarization effects. The experimental data were compared with the theoretical model based on DFT-ROCIS (Density Functional Theory, Restricted Open shell Configuration Interaction with Singles) from the literature. Changes in the spectra with temperature, particularly visible at the oxygen K edge are attributed to the loss of surface oxygen and the corresponding changes of population of the single- double- and triple vanadium coordinated oxygen. The corresponding decrease of the surface stoichiometry leads to formation lower than V5+ valency of vanadium ions such as V4+ or V3+ i.e., containing d-electrons. It gives a tentative explanation for the occurrence of metallicity attributed in the literature to a metal–insulator transition (MIT).

Secondary electron emission enhancement of MgO-Au composite film by SiO2 doping in MgO surface layer

The secondary electron emission (SEE) properties of MgO-Au composite film deposited by magnetron sputtering was improved by SiO2 doping with a Si/Mg ratio of 14 % in its MgO surface layer. Compared to the conventional electronic material MgO/(MgO-Au) film, the SiO2-doped MgO/(MgO-Au) film achieved a secondary electron yield (SEY) of 7.69 with an increase of 9.2 % at the primary electron energy (Ep) of 300 eV and the maximum SEY of 11.4 eV with an increase of 12.9 % at the Ep of 700 eV, and it kept relatively high SEY consistently under the continuous bombardment of the incident electrons with the Ep of 200 eV. This SEE enhancement is attributed to the reductions of both the band gap and work function of MgO crystal as well as the grain enlargement and surface roughness decrease of MgO surface layer induced by SiO2 doping. This scheme of SiO2 doping in the MgO surface layer of MgO-Au film provides a new idea for the preparation of high performance MgO-based SEE material.

Gadolinium-Based Nanoparticles Sensitize Ovarian Peritoneal Carcinomatosis to Targeted Radionuclide Therapy.

Ovarian cancer (OC) is the most lethal gynecologic malignancy (5-y overall survival rate, 46%). OC is generally detected when it has already spread to the peritoneal cavity (peritoneal carcinomatosis). This study investigated whether gadolinium-based nanoparticles (Gd-NPs) increase the efficacy of targeted radionuclide therapy using [177Lu]Lu-DOTA-trastuzumab (an antibody against human epidermal growth factor receptor 2). Gd-NPs have radiosensitizing effects in conventional external-beam radiotherapy and have been tested in clinical phase II trials. Methods: First, the optimal activity of [177Lu]Lu-DOTA-trastuzumab (10, 5, or 2.5 MBq) combined or not with 10 mg of Gd-NPs (single injection) was investigated in athymic mice bearing intraperitoneal OC cell (human epidermal growth factor receptor 2-positive) tumor xenografts. Next, the therapeutic efficacy and toxicity of 5 MBq of [177Lu]Lu-DOTA-trastuzumab with Gd-NPs (3 administration regimens) were evaluated. NaCl, trastuzumab plus Gd-NPs, and [177Lu]Lu-DOTA-trastuzumab alone were used as controls. Biodistribution and dosimetry were determined, and Monte Carlo simulation of energy deposits was performed. Lastly, Gd-NPs' subcellular localization and uptake, and the cytotoxic effects of the combination, were investigated in 3 cancer cell lines to obtain insights into the involved mechanisms. Results: The optimal [177Lu]Lu-DOTA-trastuzumab activity when combined with Gd-NPs was 5 MBq. Moreover, compared with [177Lu]Lu-DOTA-trastuzumab alone, the strongest therapeutic efficacy (tumor mass reduction) was obtained with 2 injections of 5 mg of Gd-NPs/d (separated by 6 h) at 24 and 72 h after injection of 5 MBq of [177Lu]Lu-DOTA-trastuzumab. In vitro experiments showed that Gd-NPs colocalized with lysosomes and that their radiosensitizing effect was mediated by oxidative stress and inhibited by deferiprone, an iron chelator. Exposure of Gd-NPs to 177Lu increased the Auger electron yield but not the absorbed dose. Conclusion: Targeted radionuclide therapy can be combined with Gd-NPs to increase the therapeutic effect and reduce the injected activities. As Gd-NPs are already used in the clinic, this combination could be a new therapeutic approach for patients with ovarian peritoneal carcinomatosis.

Dynamic Physiological Responses of Cinnamomum camphora with Monoterpene Protection under High Temperature Shock

Monoterpenes can protect plants against high temperature, but the early events of protection are still unknown. In this study, the dynamic variations in reactive oxygen species metabolism, photosynthetic capacity, and related gene expression in linalool, eucalyptol, and camphor chemotypes of Cinnamomum camphora with and without monoterpene emission under 6 h high-temperature stress were investigated. With respect to the control (28 °C), 40 °C and Fos + 40 °C (fosmidomycin inhibited monoterpene biosynthesis under 40 °C) treatments increased H2O2 and thiobarbituric acid reactive substance levels in the three chemotypes, but without significant differences between the two treatments after 2 h. Compared with the 40 °C treatment, the Fos + 40 °C treatment further aggravated the increase after 4 h, with increases of 13.8%, 12.3%, and 12.3% in H2O2 levels as well as 16.5%, 17.4%, and 9.1% in thiobarbituric acid reactive substance levels, respectively, in linalool, eucalyptol, and camphor chemotypes. When the three chemotypes were treated with 40 °C and Fos + 40 °C, the ascorbic acid content was gradually decreased during the 2 h treatment. After 4 h, the Fos + 40 °C treatment further aggravated the decrease in ascorbic acid content, with decreases of 10.6%, 9.8%, and 20.1%, respectively, in the eucalyptol, linalool, and camphor chemotypes. This could be caused by the further down-regulation of the key gene GGP in antioxidant biosynthesis. Meanwhile, two genes (VTE3 and 4CL) in other non-enzymatic antioxidant formation were also further down-regulated in Fos + 40 °C treatment for 4 h. These might lead to the further increase in reactive oxygen species levels in Fos + 40 °C treatment lacking non-enzymatic antioxidants. The photosynthetic electron yield and transfer (φPo, Ψo and φEo) in the three chemotypes were significantly (p < 0.05) decreased under the 40 °C and Fos + 40 °C treatments for 0.5 h, and the photosynthetic rate was significantly (p < 0.05) decreased in the two treatments for 1 h. After 4 h, the Fos + 40 °C treatment aggravated the decrease, as the genes encoding the components of photosystem II (psbP and psbW) and ribulose-1,5-bisphosphate carboxylase/oxygenase (rbcS and rbcL) were further down-regulated. These dynamic variations in the early events suggested that monoterpenes should act as signaling molecules to improve plant thermotolerance, as blocking monoterpene biosynthesis did not cause immediate effects on the physiological responses in contrast to the monoterpene-emitting plants during the 2 h high temperature stress, but resulted in serious damages after 4 h for suppressing related gene expression. This not only provides new proof for the isoprenoid thermotolerance mechanism by serving a signaling function, but also promotes the utilization of monoterpenes as anti-high-temperature agents, and the cultivation of high-temperature tolerance varieties with abundant monoterpene emission.

Picosecond pulsed 532nm laser system for roughening and secondary electron yield reduction of inner surfaces of up to 15m long tubes.

Laser-induced surface structuring is a promising method to suppress electron mulitpacting in the vacuum pipes of particle accelerators. Electrons are scattered inside the rough surface structure, resulting in a low Secondary Electron Yield (SEY) of the material. However, laser processing of internal pipe surfaces with a large aspect ratio is technologically challenging in terms of laser beam guidance and focusing. We present a 532nm ultrashort-pulse laser setup to process the inner parts of 15m long beam vacuum tubes of the Large Hadron Collider (LHC). Picosecond pulses at a repetition rate of 200kHz are guided through an optical fiber toward an inchworm robot traveling inside the beam pipe. The system was installed, characterized, and tested for reliability. First surface treatments achieved the required scan precision. Cu2O-dominated nano-features were observed when processing at high average laser power (5 W) and slow scanning speed (5mms-1) in nitrogen flow, and the maximum SEY of copper was decreased from 2.1 to 0.7.

Plasmonic effects in the neutralization of slow ions at a metallic surface

AbstractSecondary electron emission is an important process that plays a significant role in several plasma‐related applications. As measuring the secondary electron yield experimentally is very challenging, quantitative modelling of this process to obtain reliable yield data is critical as input for higher‐scale simulations. Here, we build upon our previous work combining density functional theory calculations with a model originally developed by Hagstrum to extend its application to metallic surfaces. As plasmonic effects play a much more important role in the secondary electron emission mechanism for metals, we introduce an approach based on Poisson point processes to include both surface and bulk plasmon excitations to the process. The resulting model is able to reproduce the yield spectra of several available experimental results quite well but requires the introduction of global fitting parameters, which describe the strength of the plasmon interactions. Finally, we use an in‐house developed workflow to calculate the electron yield for a list of elemental surfaces spanning the periodic table to produce an extensive data set for the community and compare our results with more simplified approaches from the literature.

Total electron yield (TEY) efficiency of sp2 and sp3 carbon atoms in the TEY-X-ray absorption near-edge structure (XANES) of 1,4,7,10-alkyltetracenes.

X-ray absorption near-edge structure (XANES) in the CK region of 1,4,7,10-alkyltetracenes, which are composed of sp2-C atoms in the tetracene ring and sp3-C atoms in the alkyl-chains, are measured using the total electron yield (TEY) and theoretically analyzed by DFT calculations to quantitatively investigate the π* and σ* peak intensities in the TEY-CK-XANES. The calculated π*/σ* peak intensity ratios are well approximated by the linear functions passing through the origin as a function of the sp2-C fraction, which is expressed as sp2-C/(sp2-C + sp3-C). In contrast, the measured π*/σ* peak intensity ratios are well approximated by curve functions passing through the origin, considering the TEY efficiency between sp2-C and sp3-C. The approximated curve functions indicate that the TEY efficiency of sp3-C is lower than that of sp2-C even in molecules. This confirms that the TEY efficiency of sp2-C and sp3-C should be considered in quantitative discussions on the sp2-C and sp3-C fractions from TEY-CK-XANES of carbon materials.

Suppression of Secondary Electron Emission from Nickel Surface by Graphene Composites Based on First-Principles Method.

Secondary electron emission (SEE) is a fundamental phenomenon of particle/surface interaction, and the multipactor effect induced by SEE can result in disastrous impacts on the performance of microwave devices. To suppress the SEE-induced multipactor, an Ni (111) surface covered with a monolayer of graphene was proposed and studied theoretically via the density functional theory (DFT) method. The calculation results indicated that redistribution of the electron density at the graphene/Ni (111) interface led to variations in the work function and the probability of SEE. To validate the theoretical results, experiments were performed to analyze secondary electron yield (SEY). The measurements showed a significant decrease in the SEY on an Ni (111) surface covered with a monolayer of graphene, accompanied by a decrease in the work function, which is consistent with the statistical evidence of a strong correlation between the work function and SEY of metals. A discussion was given on explaining the experimental phenomenon using theoretical calculation results, where the empty orbitals lead to an electron trapping effect, thereby reducing SEY.

(Invited) Core-Shell Fe3O4@CoFe2O4 Spinel Nanoparticles for the Oxygen Evolution Reaction in Alkaline Media

Transition metal oxides have attracted much attention as promising anode materials for anion exchange membrane water electrolysis (AEMWE). Herewith we introduce core-shell nanoparticles comprised of a Fe3O4 core and a CoFe2O4 shell as prospective catalysts for the oxygen evolution reaction (OER) at the cathode of an AEMWE. We show that confining the active component in a thin (~1-2 nm) shell and taking advantage from the core-shell synergistic interaction allows one to reach an exceptional OER activity of 2800 A at 1.65 V vs. RHE per gram of cobalt [1]. We further show that to correctly determine the OER activity, it is necessary to study the OER in a wide interval of the catalyst loadings [2].To shed light of the origin of the aforementioned synergistic effect between the core and the shell, the Fe3O4@CoFe2O4 nanoparticles were investigated using operando near edge X-ray absorption fine structure (NEXAFS) spectroscopy in a total electron yield (TYE) detection mode, under potential and during the OER conditions [3] . We documented a strong influence of the Fe3O4 core on the redox behavior of the CoFe2O4 shell under the OER conditions. Contrary to the previously studied Co3O4 anode, whose surface at high potentials has been shown to transform into CoOOH [4], the shell of the Fe3O4@CoFe2O4 nanoparticles maintains its spinel structure with Co(II) stabilized by the Fe(III) of the core. The results suggest the occurrence of a cation-redox OER mechanism involving cooperative redox behavior between Co and Fe atoms. It is remarkable that the core-shell structure is essentially preserved under the OER conditions.Figure 1. Left-hand side: cartoon showing the composition of the core-shell nanoparticle and charge transfer from Co to Fe occurring under positive polarization. Right-hand side: Fe L-edge difference spectra acquired at 1.2, 1.4 and 1.8 V vs RHE (the reference itself taken at 1.0 V vs. RHE). Reproduced from Ref. [3].Finally, we study the influence of the shell composition by replacing Co by Ni on the OER activity and stability of core-shell nanoparticles. Acknowledgements The authors are indebted to S. Hettler and R. Arenal of INMA (Zaragoza, Spain), S. Holdcroft of SFU (Vancouver, Canada) and J. Velasco-Vélez of Alba Synchrotron facility (Spain) for their cooperation. We thank the HZB für Materialien und Energie for the allocation of synchrotron radiation beamtime. Financial support from Jean-Marie-Lehn foundation is gratefully acknowledged.REFERENCES[1] L. Royer, S. Hettler, R. Arenal, T. Asset, B. Rotonnelli, A. Bonnefont, E. Savinova, B. Pichon, submitted.[2] L. Royer, J. Guehl, M. Zilbermann, T. Dintzer, C. Leuvrey, B. Pichon, E. Savinova, A. Bonnefont, submitted.[3] L. Royer, A. Bonnefont, T. Asset, B. Rotonnelli, J. Velasco-Vélez, S. Holdcroft, S. Hettler, R. Arenal, B. Pichon, E. Savinova, ACS Catalysis, https://doi.org/10.1021/acscatal.2c04512.[4] F. Reikowski, F. Maroun, I. Pacheco, T. Wiegmann, P. Allongue, J. Stettner, O. Magnussen, ACS Catal. 2019, 9 (5), 3811–3821; https://doi.org/10.1021/acscatal.8b04823. Figure 1

Influence of the composition of the cumulative lattice during thermal diffusion chromiing on the depth of the diffusion layer

Presents the results of experiments on improving the technology of thermal diffusion chromium plating of structural steels through the use of an internal emission field created in the technological backfill during heating. To create a field in the separating part of the technological backfill, aluminum oxide was completely replaced by mixtures of two compositions: a mixture of scheelite (CaWO4) and serpentine (Mg3Si2O7); a mixture of scheelite (CaWO4), serpentine (Mg3Si2O7), MgO, dicalcium silicate (γ-2•CaO•SiO2). The choice of these materials was based on the results of preliminary experiments on measuring the thermionic current in them. Saturation of samples of steel 35CrNi2-3 with chromium was carried out at a temperature of 1000°C for 24 hours. For both variants of technological fillings, the ab-sence of sintering and good knockout of parts were noted. The chemical composition of the diffusion layer on metal samples was controlled using a JEOL JSM-6460LV universal scanning (scanning) electron microscope. The micro-hardness of the coatings was measured using an FM-800 microhardness tester. The results show that the additional use of cumulative lattices of nickel and nichrome for thermal diffusion chromium plating provides an increase in the depth of chromium diffusion by 1.5 times when saturated in the backfill of the same composition. In this case, the lattice material has little effect on the depth of chromium diffusion, but it influences the intensity of surface microalloying with nickel. The electron yield work of nichrome X20H80, equal to 4.5 eV, has been determined. It was found that the hardness of the diffusion layers formed on the surface correlates with the content of chromium and nickel in them. The hardness of the chrome layer is 790±10 HV and 820±10 HV, using nickel and nichrome cumulative lattices, respective-ly. In the case of saturation without grids, the hardness is 50 and 20 HV respectively lower.

The Role of Hydrogen Incorporation into Amorphous Carbon Films in the Change of the Secondary Electron Yield.

Over the last few years, there has been increasing interest in the use of amorphous carbon thin films with low secondary electron yield (SEY) to mitigate electron multipacting in particle accelerators and RF devices. Previous works found that the SEY increases with the amount of incorporated hydrogen and correlates with the Tauc gap. In this work, we analyse films produced by magnetron sputtering with different contents of hydrogen and deuterium incorporated via the target poisoning and sputtering of CxDy molecules. XPS was implemented to estimate the phase composition of the films. The maximal SEY was found to decrease linearly with the fraction of the graphitic phase in the films. These results are supported by Raman scattering and UPS measurements. The graphitic phase decreases almost linearly for hydrogen and deuterium concentrations between 12% and 46% (at.), but abruptly decreases when the concentration reaches 53%. This vanishing of the graphitic phase is accompanied by a strong increase of SEY and the Tauc gap. These results suggest that the SEY is not dictated directly by the concentration of H/D, but by the fraction of the graphitic phase in the film. The results are supported by an original model used to calculate the SEY of films consisting of a mixture of graphitic and polymeric phases.

Measurements of secondary electron emission yield in the linear plasma simulator BPD-PSI

The secondary emission properties of the surface play one of the key roles in its interaction with plasma. This paper presents the first study of electron-induced electron emission yield performed in the linear plasma simulator BPD-PSI. To verify the applicability of the measurement technique used, a series of experiments was conducted to investigate the total secondary electron yield as a function of the energy of primary electrons for several pure elements, such as carbon, copper, and tungsten. Particular attention was paid to the latter as one of the essential plasma-facing materials, due to its ability to withstand moderate plasma loads. The change in the total secondary electron yield of tungsten was studied in-vacuo after each subsequent change in its surface morphology as a result of: annealing at 2770 K, exposure to pure helium plasma at 1250 K and annealing of plasma-modified tungsten surface at 2770 K. The growth of nanoscale structures, known as fuzz, on its surface caused a reduction in the total yield of secondary electrons by 10–18% compared to the clean surface. A non-monotonic relationship between total secondary electron yield and primary electron energy was observed. The interpretation of this phenomenon is given in the present work.

Enhanced interfacial charge transfer via in-situ construction of integrated NiO/NiCo2O4 heterojunction coupled with carbon layer for high-performance supercapacitor and photocatalysis

Constructing heterostructured composites presents a promising approach to enhance both electrochemical and photocatalytic performance. However, the low interfacial charge transfer efficiency caused by lattice mismatch severely hinders its potential application. Herein, integrated NiO/NiCo2O4 heterostructure with dodecahedral structure has been facilely prepared by a one-step in situ calcination method. In addition, to further promote the yield of photogenerated electrons and enhance electrochemical reaction kinetics, a carbon layer for charge transport is incorporated onto the outer shell of NiO/NiCo2O4 heterostructured. The elaborate designed and constructed integrated C1.0 @NiO/NiCo2O4 heterojunctions with efficient interfacial charge transfer channels exhibit an excellent gravimetric specific capacitance of 588 F g−1 at 1 Ag−1 for three electrode cell. Moreover, the C1.0 @NiO/NiCo2O4//AC supercapacitor has an excellent energy density of 68.13 Wh kg−1 at a high power density of 750 W kg−1, delivering a retention rate of capacitance exceeding 91.4% over 10000 cycles. The visible-light-induced degradation efficiency of rhodamine B (RhB) was determined to be 83.68% within a duration of 120 min. And a probable mechanism for its removal was proposed based on DFT calculations and experimental results of electrochemistry and photocatalysis. This work offers a novel perspective on the rational design of integrated heterostructured materials with enhanced interfacial charge transfer for high-performance supercapacitors and visible light-driven photocatalysis.

A search for chiral asymmetry in secondary electron emission from cysteine induced by longitudinally polarized electrons.

We performed experiments searching for chirality-dependent secondary electron emission for a 141eV longitudinally spin-polarized electron beam incident on a thick solid cysteine target. We determined the secondary electron yield by measuring the positive current produced when the cysteine target was negatively biased. No spin-dependent effects to a level of 10-3 were found for the secondary electron emission yield.