Crossed-field space-charge limited current (CF-SCLC) represents the maximum stable current that can be produced in crossed-field devices (CFDs); prominent CFDs include magnetrons and cyclotrons, critical technologies in vacuum electronics. While planar crossed-field geometries have the most developed theoretical models, cylindrical geometries are far more common and useful in practical applications. CFDs are characterized by the strength of the externally applied magnetic field $B$ , orthogonal (crossed) to the electric field; this is often normalized to the magnetic insulation condition, the Hull cutoff field $B_H$ . We apply variational calculus to derive a new theoretical model for CF-SCLC for planar and cylindrical devices below and above $B_H$ . The variational model offers a concise derivation for planar results without transforming to the time domain and gives the first analytic results from first principles for cylindrical CF-SCLC. We implement a fully three-dimensional simulation in CST Particle Studio which, in addition to additional derived simple theoretical models, explains the often overlooked experimental current scaling $\propto {\left[1-{\left(B/B_H\right)}^2\right]}^{1/2}$ which decreases to zero current as $B\to B_H^{-}$ . These additional simple models reduce the maximum mismatch magnitude between theory and experiments or simulations by up to 68% compared to the variational model, with the most improvement at the critical limit $B\to B_H^{-}$ . Justification for the variational model and future applications are discussed.

Silicon field emitter arrays (Si FEAs) are being explored as an electron source for vacuum channel transistors for high temperature electronics. Arrays of 1000 × 1000 silicon tip based gated field emitters were studied by measuring their electrical characteristics up to 40 V of DC gate bias with a 1.3 mA emission current at different temperatures from 25 to 400 °C. At ∼350 °C, residual gas analyzer measurements show that water desorption and carbon dioxide partial pressures increase significantly, the gate to emitter leakage current decreases by more than ten times, and the collector current increases by more than ten times. These improvements remained after heat-treatment but were then lost once the device was exposed to the atmosphere for several days. The improvements could be recovered upon additional baking suggesting that adsorbates (primarily water) on the surface affected field emission and surface leakage. It was also found that after heat-treatment, the electrical characteristics of the devices exhibited <3% variation in collector current at 40 V, which (without exposure to the atmosphere) can be termed as a weak temperature dependence. These results suggest that Si FEAs could be viable as a high temperature transistor.

An analysis of the effects of electromagnetic pulses from a high-power microwave (HPM) radiation technique is conducted using a relativistic backward-wave oscillator (RBWO) which uses relativistic electron beams in vacuum circuits. The application described here is based on a relativistic electron device and uses relativistic electron beams to generate high-power electromagnetic radiation. The RBWO was fabricated to operate in a relativistic region with a gamma factor (γ) of 2 at an acceleration voltage of 500 kV. A mode-converted relativistic back-wave oscillator with an antenna that converts TM₀₁ to TE₁₁ was designed and fabricated because the electric field of the center in the RBWO circuit is null. The effects on electronic devices by HPM radiation and exposure were assessed. The effects on electronic devices exposed to HPMs, the failure of information equipment, and modulation of and interference with the received signal through a theoretical model of the threshold power relative to the influence on the target were confirmed in a high-output microwave exposure environment. Particularly, information devices containing semiconductors can undergo serious failures and breakdowns due to the thermal secondary breakdown caused by the high-output transient electromagnetic waves, and it is a theoretical consideration that reverse voltage occurs due to the generation of surge current when caught in the PN-junction region. Finally, the range of power regarding the effectiveness of the electromagnetic coupling of electronics exposed to HPM radiation was estimated.

The performance of silicon gated field emission arrays (GFEAs) was characterized before and after ultraviolet (UV) light exposure. Emission and gate leakage currents were measured on 1000 × 1000 tip arrays by sweeping the gate voltage to 40 V DC with a fixed DC collector voltage of 100 V DC. UV light exposure was used to desorb water molecules from the GFEA surfaces. It was found that, before UV exposure, the gate current was 6 mA at 40 V, whereas after 70 min of UV exposure, the gate current decreased to 0.46 mA, indicating a more than ten times reduction in leakage current between the gate and the emitter. Similarly, the observed collector current was 94 μA at 40 V before exposure, and after UV exposure, the collector current increased to 1.33 mA, indicating an improvement of more than 14 times. During the experiments with UV light, residual gas analyzer measurements showed that the partial pressure for water increased by greater than ten times after 60 min of exposure and then decreased by 1 order of magnitude after 100 min of exposure. The emission and leakage current changes remained even after turning off the UV lamps for several tens of minutes; however, upon the exposure to the atmosphere for a few days, those changes reversed. The enhancement could again be observed after additional UV exposure indicating that the adsorbates (mainly water along with others) on the surface affected the leakage between gate and emitter and field emission. Based on analysis of the IV characteristics before and after UV exposure, the work function of the emitter surfaces increases while the portion of the array tips that emits expands resulting in a decrease in the calculated array tip sharpness as duller tips now emit.

A complementary vacuum field emission device structure is proposed, and its operation is analyzed by multiphysics simulation. A freely moving double-clamped cantilever, which balances the electrostatic attraction force and elastic restoration force, is used as the source electrode while the drain electrode is fixed. The electron-emitting cathode is formed on the source for the n-type device and on the drain for the p-type. Thus, complementary current–voltage characteristics are obtained only with Fowler–Nordheim tunneling electron transport. The impact of various design parameters such as vacuum gap, cantilever beam thickness, gate width, and tip offset on the drain and gate leakage currents is investigated. Inverter logic operation is verified successfully using complementary devices.

The field emission properties of the controlled emission edge of a vertically aligned graphene-based thin film are presented. A current and current density of above 7 mA and 200 A/cm², respectively, with uniform electron emission, are achieved. Uniform high current and current density emissions can be realized by the pre-mechanical shaping and post electrical conditioning of reduced graphene oxide (rGO) film emission, owing to the robustness, thinness (<1 μm), and well-defined uniform film thickness. Field emission luminance demonstrates uniform emission over the entire emission area with a high aspect ratio. Along with a high current emission, the rGO film exhibits excellent emission stability, long-term. This offers prospects for various applications in field emission displays, electron microscopy, and particularly for the realization of miniaturized terahertz vacuum electronic devices, which require electron sources with uniform high currents and current densities, such as long-lifetime cold cathodes.