Electron Emission Research Articles

Electron emission efficiency of graphene/h-BN/2D-semiconductor heterostructure: thermotical analysis and experimental verification

Abstract Metal-insulator-semiconductor (MIS) heterostructures have important applications in vacuum microelectronic devices. Among these, graphene-insulator-semiconductor (GIS) heterostructure field electron emitters are among the most widely utilized. Improving the electron emission performance is a major challenge for GIS heterostructure field emitters. A comprehensive theoretical model is needed to predict the electron emission process from such a structure. In this work, a theoretical calculation was carried out on the electron emission current from an GIS heterostructure structure based on a tunneling model that considers the density of states of the semiconductor, scattering of the insulation layer, and hot-hole-induced Auger emission process. Using graphene/h-BN/MoS2 as an example, we obtain the band structure of the MoS2 using first principle calculation, simulate the scattering in h-BN with the Monte Carlo method, and calculate the emission current density using the modified Fowler-Nordheim equation. The results indicate that h-BN thickness and Auger coefficient are key factor affecting emission current density and emission efficiency. To validate our model, a few-layer graphene/h-BN/MoS2 heterostructure device was prepared and the field emission results validate the calculation results. The theoretical model can be expanded to other GIS heterostructures and is useful for designing a high-performance electron source using a GIS tunneling junction.

Additive engineering of nonlinear optical properties of all-inorganic halide perovskites

Abstract In this study, ligand-assisted reprecipitation was used as a cost-effective and room-temperature synthesis method to produce CsPbBr3 and CsPbBr2I all-inorganic halide perovskites. CaCl2 were doped at four different concentrations into the nanocrystals to effectively engineer their nonlinear optical properties. The nonlinear responses of the prepared samples were investigated using the Z-scan technique under irradiation with a 632.8 nm He–Ne laser. Initially, the Z-scan method was examined theoretically, followed by both open- and closed-aperture Z-scan techniques to measure the nonlinear refractive index (n2) and nonlinear absorption coefficient (β), respectively. The cubic perovskite nanoparticle morphology was observed via field emission electron microscopy (FE-SEM). The size variation due to doping was analyzed using dynamic light scattering (DLS) analyses. The particle sizes increased from 35 to 250 nm for CsPbBr3 and from 30 to 330 nm for doped CsPbBr2I. The self-defocusing nonlinear refractive (NLR) coefficient decreased from 9.3 to 4.8×10-8 cm2/W for CsPbBr3 and increased from 5 to 13×10-8 cm2/W for CsPbBr2I with the addition of Ca2+ ions. The nonlinear absorption (NLA) coefficient increased for both nanocrystals with higher doping levels. The enhanced saturable absorbing properties of doped halide perovskites suggest their potential application in Q-switching and mode-locking lasers.

Photoelectron Circular Dichroism in the Photodetachment of Deprotonated 1-Phenylethanol.

Photoelectron circular dichroism (PECD) is a chiroptical effect that manifests in the angle-dependent photoemission of an electron upon irradiation of a chiral molecule by circularly polarized light. Studies of this chiroptical effect can aid in our fundamental understanding of electron dynamics, as this effect is acutely sensitive to the probed molecular state and electron emission conditions. Photodetachment of anions is a photoemission regime that has historically been understudied in conjunction with PECD. Through comparisons to electronic structure calculations, the photoelectron spectrum of deprotonated 1-phenylethanol is assigned to a single electronic transition of a single conformer. This allows for the investigation of the dependence of PECD on the electron kinetic energy and vibrational state of the molecule. PECD in the photodetachment of the deprotonated 1-phenylethanol anion is measured at different photon energies from 3.59 to 2.38 eV, showing a change in the resulting PECD value for a given transition with differing electron kinetic energies.

Functional groups control of metal by electron beam irradiation and its application to superhydrophobic surface

Since electron beam irradiation tended to increase metal wettability, significantly decreasing surface wettability remained difficult. In this paper, low-energy electron beam irradiation was used to significantly decrease the surface wettability of 316 L stainless steel, and the mechanism of modifying functional groups was revealed. The experimental results demonstrated that the hydrophilic functional groups C-O-C, O-C=O, and -OH had a significant decrease in contents, and the hydrophobic C-C/C-H group contents increased dramatically. The contact angle increased from 50° to 91°. This was due to the interaction of excited secondary electrons with precursor molecules, as well as fragmented carbon radicals and other fragments adsorbed on the surface, which generated new chemical bonds. The effects of various metal materials and microtextures on secondary electron emission were investigated. It was observed that a higher excitation coefficient for secondary electrons corresponds to a greater increase in the contact angle. The addition of different types of precursor molecules has the effect of controlling the wettability of electron beam irradiation. Nitrogen reduced the effect of electron beam irradiation modification, and hydrocarbon molecules increased the effect. A superhydrophobic surface with a contact angle of 160° and a sliding angle of 6° was successfully prepared by combining a pitting texture with hydrocarbon molecules. It has excellent wear resistance, high temperature resistance, and ultraviolet radiation resistance.

Rolling temperature effects on linear current range of secondary electron emission properties of an activated Cu–3.0Be alloy

Rolling temperature effects on linear current range of secondary electron emission properties of an activated Cu–3.0Be alloy

Photon-stimulated desorption from laser-etched vacuum structural materials of accelerators

Abstract The electron multipacting (EM) and the electron cloud (e-cloud) can have detrimental impact on the operation of the high energy or high current intensity particle accelerators. The enhanced performance of new generation particle accelerators has necessitated the development of advanced structural materials and vacuum systems. The EM and e-cloud effect have emerged as significant challenges which cannot be ignored during the design and construction of these advanced accelerators. Laser-etching technique represents a promising approach for the suppression of secondary electron emission from materials, which can lower the secondary electron yield (SEY) of the structural materials to below 1. Nevertheless, the deployment of laser-etching technique in the next generation of large particle accelerators requires a comprehensive investigation into its vacuum performance. In this work, a photo-stimulated desorption (PSD) experimental beamline was constructed on the Hefei Light Source II. The PSD yields of the structural materials (oxygen-free copper, chrome zirconium copper, stainless steel, and aluminum alloy) with and without laser-etching of the vacuum chambers were tested at normal incidence using the throughput method. The main gases desorbed from all sample surfaces are H2, CO, CO2, CH4, and H2O. The initial PSD yield of laser-etched material is higher than that of unetched material. However, the PSD yield of the laser-etched material decreases at a faster rate, and after a certain photon dose, the PSD yield of the laser-etched material is in the same order of magnitude as that of the unetched material.

Development of an Electron Emitter via Seamless Shaping of a 3D‐Printed Ceramic Cone With Carbon Nanotube Mesh Film as an Alternative to Polymer‐Based Materials

AbstractThis paper focuses on electron emitters formed using seamless hybrid shaping of the ceramic 3D‐printed cone (as a supporting structure) and a conductive emitting film obtained from the suspension of dispersed carbon nanotubes (CNT). The ceramic cone is post‐process fired to achieve a pure ceramic cone that is coated with emitting CNT mesh film. Meanwhile, a cone‐based polymer emitter is evaluated. The resulting emitter exhibits non‐linear current‐voltage characteristics reaching maximum 0.6 mA anode current with a turn‐on‐field voltage below 1 Vµm−1 and minimal current fluctuation over time. Additionally, the ceramic emitter arrays fabricated using the same technique are demonstrated: if the tip angle and shape in a microscale have tunability in emission is confirmed, meanwhile, the type of volatile gases released during the emission is confirmed using a residual gas analyzer (RGA). The motivation and challenge are to use 3D printing to enable freedom in designing and forming the emitter tip shape and angle and to present the perspective and challenges to use the 3D printing technique combined with the seamless shaping for the CNT mesh film to tune the emitter performance. Especially as this technique and 3D‐printed materials have not been previously employed for electron emitters.

Bleaching effect of radiation-induced darkening in Yb3+-doped large mode area photonic crystal fiber based on deuterium and hydrogen loading.

We report the radiation-induced darkening (RD) effect caused by X-ray radiation and the bleaching effect caused by D2/H2/N2 loading in self-developed Yb3+-doped large mode-area photonic crystal fibers (LMA PCFs). The decrease in the slope efficiency caused by irradiation decays exponentially with an increase in the X-ray radiation doses, and the radiation-induced gain variation (RIGV) showed a linear decay trend with increasing irradiation doses. The slope efficiency of Yb3+-doped LMA PCF, which significantly degraded from 71.00% to 50.42% after 50 Gy irradiation, can be significantly restored after D2 loading to 97.21% of the slope efficiency of pristine fiber. However, the slope efficiency of the PCF loaded by H2 can be recovered to 88.54% that of the pristine. These results suggest that D2 loading has a more pronounced bleaching ability than H2, while N2 does not exhibit any bleaching effect. Based on the all-fiber modular amplification experiment, an average amplified output power of 41.4 W at the pump power of 62.3 W was achieved from Yb3+-doped LMA PCFs irradiated with 50 Gy followed by D2 loading. The slope efficiency (with respect to the pump power) was 69.05%, with the laser beam quality factor M2 of 1.2. No obvious power decaying of the laser output was observed for about 10 h. RD and bleaching effects of the Yb3+-doped LMA PCF core glass have been thoroughly investigated using the absorption, radiation-induced attenuation (RIA), continuous wave electron paramagnetic resonance (CW-EPR), emission, Raman, and Fourier transform infrared (FTIR) spectra.

Field emission study on atomically heterogeneous micro-metallic emitters produced by ion beam from inert gas plasmas

Abstract High doses of irradiation in extreme environments, such as space or fusion reactors, cause significant substrate modifications, requiring systematic experimental data to understand the underlying processes. This study explores the effects of ion irradiation on aluminum and titanium sheets used in spacecraft, with fluence levels ranging from 3.8 to 4.0 × 1018 cm-2, employing 2 keV ions of argon and krypton generated by 2.45 GHz microwave plasma to investigate surface modifications and atomic heterogeneity induced by ion implantation, while minimizing complications from chemical bond formation. This experimental investigation is further extended to understand the impact of implanted ions and surface modifications on electron emission properties in high electric fields. Notable field emission improvements are observed: for Kr-irradiated Al, turn-on potential is 2.3 ± 0.6 kV, a maximum current is 3.4 ± 0.3 nA, and enhancement factor is 1059, with Kr incorporation at 76.9 %; for Ar-irradiated Ti, turn-on potential is 1.6 ± 0.2 kV, a maximum current is 9.8 ± 0.8 nA, and enhancement factor is 2540, with Ar content at 88.5 %. This study thus systematically discusses the discernible variations in field emission properties with the morphological changes, ion implantation percentages, and local work function measurements, providing valuable insights into the effects of inert gas ion irradiation on metallic substrates.

Superior charge storage performance of optimized nickel cobalt carbonate hydroxide hydrate nanostructures for supercapacitor application

In our work, we report superior electrochemical performance of optimized 3D nanostructured, nickel-cobalt carbonate hydroxide hydrate (Ni3 − xCox-CHH (1 ≤ x ≤ 2)) materials with flower like morphology synthesised via one-step hydrothermal methods. A Ni rich sample (x = 1) demonstrate better specific capacitance and the improvement is attributed to more oxygen deficient neighbourhood of Ni compared to that of Co. The structural, morphological and electronic properties of the samples were investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), High resolution transmission electron microscopy (HRTEM), field emission electron microscopy (FESEM), Energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). A comprehensive characterization was used for physicochemical properties-electrochemical performance correlation. Cyclic voltammetry (CV), Galvanostatic charging and discharging (GCD) shows the supercapacitor feature of the samples for the composition containing the highest nickel concentration achieving a specific capacitance of 1649.51 F g− 1 at a current density of 1 A g− 1 and excellent rate capability of 1610.30 F g− 1 at a high current density of 5 A g− 1. The sample shows high cyclic stability of 80.86% after 3000 cycles. Improved specific capacitance is attributed to the synergy effect of bimetallic transition metals as well as improved surface area of flower like morphology. These findings show that Ni2Co-CHH electrode material demonstrates great potential as electrode material for supercapacitor device fabrication.

Higher-order effects and validity of the point-dipole approximation for conjugated extended molecular emitters near plasmonic nanostructures.

Rapid advancements in nanotechnology have allowed for the characterization of single molecules by placing them in the vicinity of nanoplasmonic structures that are known to confine light to sub-molecular scales. In this study, we introduce a theoretical framework that captures higher-order effects, and we explore the limits of the standard description of a molecular emitter as a point-dipole. We particularly focus on the role played by the emitter chain length and electron conjugation. Strong deviations are observed from the point-dipole approximation, demonstrating that higher-order effects are essential to fully capture the emission rate of extended molecules in the vicinity of nanoparticles. This deviation strongly depends on the orientation of the conjugated chain relative to the nanoplasmonic structure. Finally, we propose a simple rationalization that qualitatively assesses the difference from the point-dipole approximation.

Tetrahedral Al20O30 Cage: A Superchalcogen Atom.

Superatoms are stable clusters that mimic the chemical behavior of individual atoms in the periodic table. Many endeavors have been devoted to the design and characterization of various superatoms, while engineering superatoms to mimic the chemistry of chalcogens remains a challenge. In this paper, we present a new superchalcogen by evaluating a hollow tetrahedral Al20O30 cluster with theoretical calculations. By comparing the Al20O30 with its daughter dianion (Al20O30)2- in terms of stability, aromaticity, electronic properties, and chemical behavior in compounds, we find that this cluster tends to get two additional electrons to reach a more stable electronic state, which is the origin of the identity of superchalcogens. The adaptive natural density partitioning (AdNDP) analysis illustrates that this Al20O30 cluster accommodates two electrons by a 4-center-2-electron bond formed between the four face-centered Al atoms. Moreover, the Al20O30 cluster has exothermic first and second adiabatic electron affinity (EA), indicating that the dianion (Al20O30)2- is stable against spontaneous electron emission and fragmentation in the gas phase. This reflects the size advantage of superchalcogens when compared with chalcogens. Interestingly, we further study a cluster with one more electron than the superchalcogen Al20O30, namely, H@(Al20O30) and find that it is a superhalogen due to its large vertical and adiabatic EA.

Radiocobalt-Labeling of a Polypyridylamine Chelate Conjugated to GE11 for EGFR-Targeted Theranostics.

The overexpression of the epidermal growth factor receptor (EGFR) in certain types of prostate cancers and glioblastoma makes it a promising target for targeted radioligand therapy. In this context, pairing an EGFR-targeting peptide with the emerging theranostic pair comprising the Auger electron emitter cobalt-58m (58mCo) and the Positron Emission Tomography-isotope cobalt-55 (55Co) would be of great interest for creating novel radiopharmaceuticals for prostate cancer and glioblastoma theranostics. In this study, GE11 (YHWYGYTPQNVI) was investigated for its EGFR-targeting potential when conjugated using click chemistry to N1-((triazol-4-yl)methyl)-N1,N2,N2-tris(pyridin-2-ylmethyl)ethane-1,2-diamine (TZTPEN). This chelator is suitable for binding Co2+ and Co3+. With cobalt-57 (57Co) serving as a surrogate radionuclide for 55/58mCo, the novel GE11-TZTPEN construct was successfully radiolabeled with a high radiochemical yield (99%) and purity (>99%). [57Co]Co-TZTPEN-GE11 showed high stability in PBS (pH 5) and specific uptake in EGFR-positive cell lines. Disappointingly, no tumor uptake was observed in EGFR-positive tumor-bearing mice, with most activity being accumulated predominantly in the liver, gall bladder, kidneys, and spleen. Some bone uptake was also observed, suggesting in vivo dissociation of 57Co from the complex. In conclusion, [57Co]Co-TZTPEN-GE11 shows poor pharmacokinetics in a mouse model and is, therefore, not deemed suitable as a targeting radiopharmaceutical for EGFR.

Emission of electrons and photons and formation of cascade ions during the decay of 125I radionuclide

Emission of electrons and photons and formation of cascade ions during the decay of 125I radionuclide

Electron emission performance analysis and application of carbon nanotube cold cathode prepared by cold pressing process

In this work, a carbon nanotube (CNT) cold cathode electron emitter fabricated by the cold pressing process was developed and studied. The electron emission performance was investigated and the application of pulse x-ray emission and imaging was explored by this cold cathode. The results indicated that the electron emission performance was excellent with electric intensities of turn-on and threshold of 0.47 and 1.17 V/μm@1 mA/cm2, respectively, and the field enhancement factor reached 17 514. The application research results showed that the pulse x-ray waveform has a great corresponding well with the grid voltage, and the imaging of a screw was clear, whose thread and pitch could be seen clearly. This article proposed a cold pressing process prepared for the CNT cold cathode, providing a new technical approach for the development of field emission cold cathode preparation processes.

Enhanced field electron emission of formamidine lead triiodide induced by strong electric field assisted morphology reconstruction

Enhanced field electron emission of formamidine lead triiodide induced by strong electric field assisted morphology reconstruction

Investigation of the effects of temperature cycling on the leakage mechanism of Through-Silicon Via (TSV) insulation layer

Through-silicon via (TSV), as a key technology for realizing interconnections in three-dimensional integrated circuits (3D ICs), critically depends on the integrity of its sidewall interfaces to maintain optimal leakage characteristics. This study conducted temperature cycling experiments, incorporating leakage current <i>I-V</i> testing, microstructural observations, and EDS elemental analysis to evaluate the effects of temperature cycling on the integrity of TSV sidewall interfaces and the leakage mechanisms in the insulation layer. The results indicate that, as the number of temperature cycles increases, the alternating cyclic loads progressively degrade the integrity of the TSV barrier layer, transitioning from an intact interface to the formation of micro-voids and micro-cracks. This results in a significant increase in leakage current. When through-thickness cracks appear at the interface, a sudden decrease in leakage current occurs. The TSV failure mode shifts from thermally induced leakage to mechanical cracking. The leakage mechanism of the insulation layer transitions from the Schottky emission mechanism (Cycle ≤ 60) to a combination of Schottky emission and Poole-Frenkel emission mechanisms (Cycle ≥ 90), and this shift becomes more pronounced under high electric field conditions. Further analysis of TSV interface integrity reveals that thermomechanical stress induced by temperature cycling generates defects at the interface between the TSV copper fill and the barrier layer. As thermally induced defects accumulate, the barrier height of the insulation layer continuously decreases, making it easier for electrons in the metal to overcome the Schottky barrier under thermal and electric field excitation, thereby forming leakage currents. Moreover, these defects facilitate the diffusion of copper atoms into the insulation layer, resulting in the formation of localized high electric field regions. These high-field regions in the insulation layer increase electron emission rates through the Poole-Frenkel emission mechanism, creating leakage paths. Therefore, copper diffusion emerges as one of the primary causes of dielectric performance degradation in the insulation layer.

Enhanced field emission performance of gold nanoparticle decorated Bi2S3 nanoflowers.

Au nanoparticles (NPs) are decorated on hydrothermally synthesized Bi2S3 nanorods (NRs) to enhance the field electron emission (FEE) performance as compared to bare Bi2S3 nanorods, resulting in reduction in turn-on field from 3.7 to 2.7 V μm-1 (at the current density of 1.0 μA cm-2) with significant increment in maximum emission current density from 138 to 604.8 μA cm-2 (at a field of 7.8 V μm-1) respectively. FESEM/TEM reveals that Bi2S3 nanoflowers are assembled from Bi2S3 NRs of a typical diameter of 120 ± 10 nm, and Au NPs of diameter about 5-10 nm are uniformly decorated onto the surface of NRs to form an Au/Bi2S3 composite. XRD analysis suggests that the as-synthesized product consists of orthorhombic Bi2S3 NRs decorated with face-centered cubic Au NPs. The XPS spectrum shows the elemental mapping of the as-synthesized Au/Bi2S3. Improvement in field emission properties is mainly attributed to a reduction in work function and increasing emitting sites due to Au NP decoration.

Selective laser processing of particle accelerator beam screen surfaces for electron cloud mitigation

Laser-induced surface roughening is a technique that facilitates the reduction of secondary electron emission (SEE) from materials, which is crucial for mitigating electron cloud (EC) formation in particle accelerators, that...

Comparison of [125I]I-labeled trastuzumab and pertuzumab for targeted Auger electron therapy of cancers overexpressing HER2 receptors

Objectives: The HER2 receptor is often overexpressed in various cancers, particularly in breast and ovarian cancers, and this overexpression significantly contributes to the growth and spread of these tumours. Trastuzumab (Herceptin) and pertuzumab (Perjeta) are widely used humanized monoclonal antibodies (mAbs) that have shown promise in treating patients with HER2-positive breast cancer. To enhance their effectiveness, mAbs have recently been combined with chemotherapeutic agents and radionuclides. The aim of our studies was to investigate the potential therapeutic use of trastuzumab and pertuzumab labelled with the Auger electron emitter - 125I. Methods: The radioimmunoconjugates synthesized using 125I and 131I were tested in various in vitro studies on SKOV-3 cells. These studies included tests for specificity, binding affinity, internalization, cytotoxicity (MTS assay), and confocal imaging. Results: The results confirmed that radioiodinated mAbs have high affinity and internalization properties in HER2+ cell line. In contrast to trastuzumab, significant localization of iodinated pertuzumab on the cell membrane was observed. MTS assay and spheroid studies demonstrated minor toxic effects from both radioconjugates, resulting from the combination of the mAbs' immunotoxic effect and the interaction of Auger electrons. However, [125I] I-pertuzumab exhibited higher cytotoxicity. Conclusions: Despite high internalization, both radiobioconjugates showed low cytotoxicity due to the lack of radionuclide localization in the cell nucleus. However, [125I] I-pertuzumab accumulated in the cell membrane, resulting in slightly higher cytotoxicity. To improve therapeutic efficacy, modifying [125I] I-trastuzumab and [125I] I-pertuzumab to transport them to the cell nucleus, e.g., using nuclear localization signal (NLS) peptides is crucial.