We successfully demonstrate for the first-time field emission (FE) from and to the two-dimensional electron gas (2DEG) formed in AlGaN/GaN heterojunction based lateral nanoscale vacuum emission diodes. In addition, we demonstrate FE with an AlGaN/GaN cathode and metallic anode. Our FE measurements demonstrate that these vacuum diodes with AlGaN/GaN and metallic anodes can deliver emission current in the range of microamps to milliamps, respectively, when biased within a range from 5 to 30 V.
In this work, we describe a testbed for studying free-electron photon interactions in a 1 to 20-keV scanning electron microscope. The setup includes an ultrafast emitter, optical modulators for structuring the electron beam, a nanostructured interaction zone, and electron and optical spectrometers with time-tagging electronics to characterize these interactions. Through this work we aim to understand these interactions at electron energies orders-of-magnitude lower than used in most previous work, enabling their more widespread adoption and potentially leading to chip-scale technologies.
We have developed a thermal radiation (blackbody emission) hyperspectroscopy apparatus with a spectral range of ~ 1–7 µm and a spatial resolution of ~10 µm, with the sample held in an ultra-high vacuum chamber. This system enables the detailed analysis of thermal photon emission from nanomaterials/structures and temperature mapping up to thermionic electron emission temperatures under high thermal gradients and with high spectral fidelity. It is thus a useful characterization tool for studying the role of low-dimensional physics in thermal transport and emission and related phenomena such as heat localization in nanotubes.
This study explores the potential of using a multi-beam system with carbon nanotubes (CNTs) as field emission X-ray sources for next-generation medical and industrial imaging and diagnosis techniques like tomosynthesis. CNTs' ability to withstand high temperatures and digital properties make them ideal for the multi-beam system. Using the multi-beam system with multiple CNT X-ray tubes can achieve faster image acquisition, reduced patient dose, and 3D reconstructed image. Overall, this study demonstrates the need and the advantages of using a multi-beam system with CNT-based X-ray sources for advanced imaging and therapy techniques.
The purpose of this study was to evaluate the effect of electrical aging on the cold cathode electron beam (C-beam). This experiment is performed by the vertically aligned carbon nanotube in which it is established that the applied bias for efficient electrical aging and defined the bias voltage as the voltage at which joule heating occurred. A long-term stable field electron emission from carbon nanotube arrays can be achieved through an aging process at high emission current. Additionally, x-ray imaging and dose measurement were used to assess the Focal Spot Size (FSS) of the tungsten cross wire used as a standard resolution testing object (EN 12543–5). We found that the aging had no significant effect on the FSS, but the x-ray dose rate enhanced from 0.45 mGy/sec to 1.1 mGy/sec.
A flat-format vacuum light source using cathodoluminescent phosphors has been designed, modeled, and fabricated. It is found applicable to general and specialty lighting.
Here, we discuss how existing results for drag in the vacuum might be extended to the case of lone finite-chord slender body transiting the vacuum. We also present, qualitatively, a model of the vacuum that can support within it boundary films, near wakes, wake shear zones, etc. Finally, we discuss Hohman transfers, Bohr's model of the atom, Planck, etc.
This paper presents a novel approach to the development of a MEMS-based Quadrupole Mass Spectrometer. The instrument consists of a 3D-printed, compact chip-like package containing MEMS components required to perform the gas analysis. Obtained mass range between 1 and 150 u and a resolution of 45, makes it ideal for a range of applications which does not require high-end performance. Our work demonstrates that MEMS technology in conjunction with novel 3Dp fabrication techniques offers a feasible route to developing compact mass spectrometers, providing an opportunity for researchers to create portable, yet potent instruments for a range of applications, opening new possibilities for on-site, real-time analysis in many different fields.
We analyze the emission of density-modulated electron beams of different temporal shapes under the excitation of a combined radio frequency (RF) field and a continuous wave or pulsed laser field, using an exact quantum model for photo/field-emission.
We study charged-particle guiding structures based on periodic arrangements of microfabricated electrostatic lenses. Specifically, we analyze such electrostatic guiding structures via a transfer matrix approach, and we uncover the stability criteria and the beam transport properties of these guides. Furthermore, we present a planar guide design that is amenable to modern microfabrication, and we demonstrate, via simulation, that this guide is capable of confining energetic, keV-scale electron beams over extended lengths.
A turn-on field reduction of up to 59% was observed for field emission (FE) from carbon nanotube (CNT) forests that were grown on titanium nitride (TiN) coated substrates instead of on pristine ones. The FE properties of the CNTs were enhanced by the TiN films on the substrates-which were generated by plasma-enhanced atomic layer deposition (PEALD)-without a noticeable impact on the emitter morphology. These results are transferred from bulk to nanomembrane substrates revealing improved FE properties, which could potentially be used for future sensor applications.
A silicon field emission electron source consisting of a cathode and a grid electrode has been fabricated by laser micromachining. The cathode features 21×21 tips on an area of 4×4 mm 2 , With a self-aligning MEMS technology for the aperture grid, a high electron transmission (99 %) was achieved. Onset voltages of 50…70 V were observed for an emission current of 1 nA. A stable emission current of 1 mA ± 1.3 % at an extraction voltage of 250 V was observed during a 30-min operation.
Silicon nanowire field emission arrays (50 × 50 pillars) were fabricated on a silicon glass hybrid wafer. The glass acts both as the support for the whole structure and insulator between cathode and extraction grid. The extraction grid matches the emitter structures and is optically aligned and adhered to the emitter chip by a vacuum compatible epoxide adhesive. These chips exhibit an emission current of about 600 $\mu{\mathrm{A}}$ at an extraction voltage of 300 V. The electron transmission through the grid is above 80 %. 58-hour longtime measurements were conducted showing low degradation of the emission current and high stability of electron transmission.
Using a particle-based Monte Carlo modeling approach we study the characteristics of silicon field emitter devices. We use an unstructured mesh based on tetrahedral elements to describe the device geometry in three dimensions, and we treat silicon and vacuum on equal footing when tracking electrons in both regions. We compare several tunnel models by evaluating the current-voltage characteristics of a single field emitting silicon pillar. Then, we perform an initial model validation, comparing the simulated current-voltage characteristic the measured values for a gated silicon field emitter. Furthermore, we extend our simulation to field emitter arrays (FEAs) to study the screen effect for adjacent emitters.
This presentation is part of a long-term project to put field electron emission (FE) onto a better scientific basis, by seeking reliable quantitative agreement between theory and experiment, especially as regards emission-current values. The main paper aims are: (1) to respond to remarks made in recent papers [1,2]; (2) to restate the thinking behind our 2022 methodology [3] for choosing between different FE models using experiments; (3) to assess progress; and (4) to make further suggestions about improved approaches.
The miniaturization of mass spectrometers is a fast-growing new direction for the mass spectrometry (MS), enabling the transition of MS from laboratory to point of sample collection and and from experts to novice end users. During the past two decades, some major efforts have been put into this field which led significant advancements in both instrumentation as well as application. Here, we review the recent development in MS miniaturization and highlight the state-of-the-art systems as well as new technologies allowing some new capabilities for chemical and biological analysis.
This study reports the synthesis of carbon nanotubes (CNTs) using induction heating technology as a rapid, clean, and inexpensive method. CNTs were synthesized on a metal alloy substrate. The CNTs growth were purposed to optimize by controlling work pressure, growth temperature, and growth time in the high vacuum chamber with induction heater. The CNTs were characterized by scanning electron microscope ( SEM) for surface analysis and field emission properties were measured. Compared to traditional thermal chemical vapor deposition (CVD) synthesis methods with graphite heater, induction heating technology offers a more efficient and practical alternative for producing CNTs with potential applications in various fields.
We present a novel back-front double-gated triode electron gun (E-gun) structure that incorporates a 3D carbon nanotube (CNT) emitter. The E-gun includes three macrosize metal honeycomb meshes, with two serving as gates and one as a cathode, with directly grown CNTs on its surface. By biasing the two double gates simultaneously, a DC current of over 4.28 mA was achieved, almost double compared to the collective current when each gate was biased individually. This increase in current is attributed to the unique design of the E-gun structure, which allows maximum participation of CNTs and is also confirmed by the simulation.
The article presents imaging results performed using a MEMS electron microscope setup. Three different electron detectors were developed and tested. The detectors integrated with a scanning octupole system were placed inside the JEOL JSM IT-100 SEM sample chamber. Using the SEM electron beam, the test images were obtained, confirming the usefulness of all three detectors. Moreover, a comparison between images obtained using the JEOL microscope and MEMS EM setup is presented.
This study presents the design and characterization of a carbon nanotube (CNT)-based X-ray source. The physical and chemical properties of the directly synthesized CNT were thoroughly examined, and their field emission characteristics were confirmed. Furthermore, the functionality of the fabricated source was validated by acquiring the emitted dose using the digital drive mode at 160 kV. The results indicate that the developed CNT-based X-ray source holds significant promise for potential applications in the field of cell therapy.
