Insulated gate bipolar transistor (IGBT) is a kind of power switching device owns the advantage of gate voltage control and high power capacity, while remaining the problem of potential catastrophic failures in high voltage. A novel structure of IGBT combined with a vacuum field emission transistor (VFET) and a bipolar junction transistor (BJT) was introduced which exhibits high blocking voltage, high frequency characteristics and excellent robustness toward catastrophic failure such as latch-up and gate oxide breakdown. A pulsing current overshooting effect due to the gate-cathode capacitance of VFET was observed to expedite the switching process, offering a novel approach to shorten the switching time of IGBT. Benefit from this, the field emission IGBT (FE-IGBT) was capable of operating over a broad frequency range from DC to 100 kHz. The static and dynamic characteristics of the device were reported, including a blocking voltage of 800 V, a maximum output current of 0.5 A. This work presented a new route to bloom the performance of IGBT and also created a feasibility to connect vacuum electronics device with solid-state semiconductor devices.

Carbon nanotube fibers (CNTFs) have emerged as promising field emission material and demonstrated excellent field emission characteristics. The collective field emission behavior at the fiber tip, especially the nanoscale dynamic morphological evolution is key to its high current density field emission performance. In this study, we perform in-situ transmission electron microscopy (TEM) to directly visualize the morphological evolution of clustered CNTs at the CNTF tip during field emission. Following cap removal and height reduction, the emission current increased markedly from 865 nA to 15,030 nA in a single CNTF. Fowler-Nordheim analysis reveals a 3fold decrease in field enhancement factor, accompanied by a 322-fold increase in effective emission area. It is attributed to a transition from tip-dominated to collective emission, driven by electric field homogenization which also suppressed the hotspot and enhanced the temperature distribution uniformity. These findings provide crucial insights into the dynamic collective behavior of clustered CNTs and offer guidance for carbon-based cold cathodes and CNT assemblies.

Facing the precising X-ray imaging applications such as medical and integrated circuit industry, high resolution micro-focal spot X-ray source is in urgent need. In this work, a novel carbon nanotube fiber (CNTF) was introduced as the microscale cold cathode for the X-ray source. The precising fabrication and field emission characteristics of CNTF cathode were carried out. The apex of the CNTF exhibited a cone-like structure with a diameter of 3.2 mu m, which gives an extremely high current density of 3632.6 A/cm2, high reduced brightness of 1.14 x 1010 A m- 2 center dot sr- 1 center dot V-1, low semi-angle of divergence of 11.3 degrees, and low current fluctuation of 0.97 %. Benefit from the microscale CNTF cathode, a transmission type micro-focal spot X-ray source was assembled using a simple electrooptical structure. The measured X-ray FSS was 15.6 mu m and the imaging resolution of 8.0 lp/mm was achieved at the anode voltage of 45 kV and anode current of 31.8 mu A. The results demonstrated that the CNTF cold cathode based micro-focal spot X-ray source is a convenient and low-cost device solution which have a great potential in the applications of microscale object and biological tissue imaging.

To enhance the light response flexibility of field emission cold cathodes, this study developed a photo-assisted field emission platform using silicon nanopillar arrays. Periodic arrays were fabricated via standard lithography to leverage ultraviolet (UV) local field enhancement. FDTD simulations revealed significant near-field enhancement factors of approximately 26–27 under 325 nm excitation. Experimental results at a 65 V/μm bias field showed that UV irradiation (~1.5W/cm2) remarkably boosted emission currents: from 0 to 80 nA for Sample 1 and 55 to 161 nA for Sample 2. These findings confirm a strong correlation between geometric design and optical resonance, providing a scalable, CMOS-compatible platform for high-efficiency, tunable vacuum nanoelectronics.

We investigate the energy spectrum characterization on gated p-type Si-tip field electron emitters with sharp-tips (5 nm radius) and blunt-tips (50 nm flat-end). Both the two types of emitters showed single-peak energy spectrum with similar energy spread (FWHM of ~1 eV) at a similar emission current of 1 nA, while the central peak-energy showed a shift of ~11 eV for the sharp-tip versus ~1 eV for the blunt-tip. The identical single-peak structure with a consistent energy spread is governed by energy relaxation during bulk transport and surface-state-mediated emission, with inelastic scattering in surface and oxide defect states determining the spectral broadening, independent of tip geometry and band bending. Thermal-sharping induces boron segregation, yielding a lower doping concentration (~2.97×1013 cm−3) in the sharp-tip than in the blunt-tip (~3.07×1014 cm−3), which results in a wider depletion region and a higher voltage drop, thereby causing a significant peak-shift. This work establishes a physical basis for the design and uniformity control of gated p-type Si-tip field emitter devices through modulation of depletion regions to control the peak energy, together with surface modification to suppress inelastic scattering and narrow the energy spread.

We demonstrate an on-chip integrated vacuum nanodiode with a CsPbBr3 sheet-cathode for direct electron detection. Under 5 keV electron irradiation at a beam current of 100 pA, the device achieves an on/off ratio of 248 at a cathode-anode bias of 15 V, enabling high contrast detection due to the low dark current of ~100 pA. At a bias of 23.5 V, the detection efficiency reaches 141%, exceeding the theoretical gain from impact ionization and thus enabling high sensitivity detection. This work extends vacuum nanodiodes to direct electron detection. The high responsivity and on‑chip integrability make the device promising for detector arrays in high-throughput multi-beam scanning electron microscopy.

On-chip integrated field-emission vacuum transistors (FEVTs) have attracted significant interest owing to their potential robustness in harsh environments. However, their miniaturization involves a fundamental trade-off. Specifically, a narrower cathode-anode separation lowers the operating voltage but allows the anode electric field to influence the cathode surface barrier, thereby hindering output current saturation. A narrower cathode-gate separation enhances gate control but increases electron interception at the gate, which degrades anode collection efficiency and limits the output current. In this work, we demonstrate an on-chip integrated vertical Si-tip FEVT that alleviates this trade-off via a synergistic structural design. The design synergistically optimizes the gate height, gate aperture radius, and anode aperture radius to shield the cathode from the anode field. Simultaneously, an integrated ultra-sharp Si tip provides highly collimated electron emission, which mitigates electron interception by the gate and thereby maintains an anode collection efficiency above 80%. The optimized single Si-tip FEVT exhibits clear current saturation, achieves an on/off ratio of 9.6 × 104, and delivers an anode current of 1.24 μA at a gate voltage of 100 V. Furthermore, a 40 × 40 Si-tip array FEVT leverages current superposition from multiple tips to achieve enhanced performance. The array delivers 1.24 μA (comparable to the single-tip device) at a gate voltage of only 50 V, and reaches 7.57 μA with an on/off ratio of 1.06 × 106 at a gate voltage of 80 V. This work provides a design strategy for linear-mode vacuum microelectronic devices.

Two-dimensional transition metal dichalcogenides (2D TMDCs) have attracted considerable research interest as key materials for next-generation integrated photonic and optoelectronic devices. However, the atomic layer materials are vulnerable to environmental influences. In addition, their ultimate thinness limits the effective length of light-matter interaction, restricting their emission intensity. Although bulk and few-layer TMDCs exhibit better environmental robustness, they typically suffer from indirect bandgap transitions, resulting in reduced optoelectronic efficiency. In this work, we report an in situ processing strategy to induce direct-bandgap exciton emission from few-layer (2-4 layers) MoS2. A combined approach of mild oxygen plasma treatment and subsequent laser irradiation is employed to modify the few-layer MoS2. Following the treatments, we observed pronounced photoluminescence (PL) emission in the suspended few-layer MoS2, in contrast to the PL quenching effect detected in substrate-supported areas. Such a large difference in PL intensity is attributed to thermally driven interlayer decoupling of the few-layer MoS2, which occurs exclusively in the suspended regions due to their significantly elevated temperature. According to the molecular dynamics simulation study, plasma treatment is essential for interlayer decoupling by injecting oxygen ions into the van der Waals gaps. These oxygen ions can potentially form oxygen molecules under laser-induced heat, leading to the expansion of van der Waals gaps. These findings demonstrate the potential for spatially selective PL enhancement in few-layer MoS2. As a proof of concept, high-contrast PL patterns in bilayer MoS2 were prepared, showcasing its promising application in anti-counterfeiting labeling. Furthermore, this work provides high-performance light-emitting materials for diverse photonic and optoelectronic applications.

Non-stoichiometric molybdenum trioxide (MoO3-x) thin films are promising electrochromic materials owing to their abundant oxygen vacancies that enhance ion storage and redox activity. However, translating these intrinsic properties into superior device performance critically depends on the film microstructure, which governs ion transport kinetics and interfacial electrochemistry. In this study, we achieved effective regulation of MoO3-x thin film microstructure by manipulating critical process parameters during thermal evaporation. A phase-field theoretical model was established, successfully elucidating the fundamental conditions governing the formation of typical crystalline and amorphous MoO3-x films. Our findings demonstrate that, compared to the crystalline structures, the isotropic three-dimensional ion migration channels provided by the continuous and dense amorphous MoO3-x films significantly reduce ion intercalation barriers and effectively buffer volume strain during lithium-ion insertion and extraction, thereby exhibiting superior electrochromic properties and cycling stability. This research not only presents amorphous MoO3-x thin films as a promising candidate for high-performance electrochromic electrode materials, but also establishes structure-property relationships that provide effective guidance for the structural design of related electrode materials.

Vacuum microelectronics using cold field electron emission and integrated circuit manufacturing techniques were previously explored to address limitations of vacuum tubes such as size and power consumption. However, their development and practical use have been constrained by the need for high-vacuum operating conditions. To address this challenge, we report a Si-based nanoscale vacuum electron diode with self-encapsulated channel, which is fabricated using a Si hyperbolic nanostructure and a rapid thermal oxidation process. The device is capable of operating in air, significantly reducing the requirement for a vacuum environment. It exhibits a turn-on voltage of 35.5 V and an Ion/Ioff ratio of 3.07×105. This work provides a new approach for developing micro/nano electronic devices capable of operating in air.

Bayard-Alpert (B-A) ionization gauge with gated Si-tip array cathode was established. The critical parameters including grid wire diameter and spacing were optimized through electron trajectory simulation to improve the detection sensitivity of the gauge. The gauge was constructed with on-chip large-scale multi-ring arranged Si-tip field emitter array. In an ultra-high vacuum (UHV) environment (2.5×10−7 Pa), an ion current of 150 pA was registered, which validates the functionality and operational feasibility of the gauge.

A vacuum electron device requires a high-performance electron source that provides high current and current density. A carbon nanotube (CNT) field emission cold cathode is the optimal choice. To achieve its higher emission current capacity, its macroscale and microscale structures should be combined. Here, a two-dimensional fin-shaped CNT field emission structure is proposed, integrating a macroscale CNT fin with billions of nanoscale nanotubes. The fin contributes two-dimensional heat dissipation paths, and the nanotubes provide a high field enhancement factor, both of which enhance the high-current field emission characteristics. A model combining macro- and microstructures was simulated to optimize the structure and fin-shaped array parameters. The calculation of the field enhancement factor of the compound structure is proposed. It was also determined that the fin-shaped array configuration can be densely arranged without field screen effects, thereby enhancing the emission area efficiency. The fin-shaped CNT emitter and array emitters with different parameters were fabricated by laser ablation, which demonstrated superior field emission characteristics. A 16.55 mA pulsing emission current, 1103.33 A/cm2 current density, and 6.13% current fluctuation were achieved in a single fin-shaped CNT emitter. An 87.29 mA pulsing emission current, 0.349 A/cm2 current density, and 1.9% current fluctuation were achieved in a fin-shaped CNT array. The results demonstrate that the high-current field emission electron source can be realized in a well-designed emission structure that bridges the nanoscale emitter and macroscale structure.

Field emission cold cathode has the advantages of room temperature operation, high current density and compact size. Facing to high current electron source application, it has to further raise the emission current and current density. One of the constraints is the low emitter area efficiency and the shielding effect. In this work, a double layer carbon nanotube cathode structure was proposed which comprises a primary cathode and a second cathode. The primary cathode is a traditional array type field emitter. The second cathode serves a dual function: acting as both a mesh stripe type field emitter and an electrode that applies voltage to drive the primary cathode field emission. The two electrodes complementally cover the whole cathode space. This design increases the effective emission area within the cathode space and gets rid of the shielding effect, thus increasing the emission current and enhancing the emission stability. Experimental results demonstrated that the structure attained an anode current of 12 mA at an anode voltage of 1600 V which is double of the traditional array emitter. The current fluctuation was 1.9 % over a 3-h test period. This method offers a feasible solution for achieving a high current electron source further push on the application of cold cathode on microwave/terahertz vacuum electronics devices.

Approaching the trend of scaling down, vacuum electronics device (VED) and its electron source is changing its bulk form to planar type on chip. Carbon nanotube (CNT) cold cathode has the advantage of microscale and exceptional emission current density which has catch attentions. However, the uncontrollable CNT growth and the compatibility to microfabrication significantly restrict its device application. Here we proposed a novel CNT integrated gate structure and a simple fabrication process. A vertical CNT film wafer was adopted as the emitter layer to reduce the fabrication difficulty and increase emission current. A thin silicon layer was adopted as the self-focusing electrode to modulate electron beam trajectory and increase electron transmission ratio on the gate. A flip-chip process was adopted to solve the problem of CNT contamination and height nonuniformity. The fabricated 22 x 22 emitter array exhibited a low turn-on voltage of 62 V and a maximum emission current of 945 mu A at 156 V, corresponding to an emission current density of 1.105 A/cm2 and a gate electron transmission ratio exceeding 97 %. This work offers a high-performance cold cathode electron source on chip using vertical CNT film wafer which facilitates the development of field emission electron source and the related VED on chip.

This study proposes a power switch combining a vacuum field emission transistor (VFET) as a controlled transistor with a power bipolar Darlington transistor (DT) as an output transistor, termed the VFET–DT structure. Compared to the MOS–bipolar Darlington power switch, the VFET–DT structure achieves an extremely low off-state leakage current and high-voltage withstanding capability due to the field emission mechanism of the VFET. It can also avoid the Miller effect that results from incorporating the load resistance into the feedback loop. The high gain and high-power capacity can be achieved due to the cascade of DT. The device’s typical electrical characteristics were theoretically investigated by simulation. The VFET–DT structure exhibited a high-power capacity of 20 A and 400 V with a minimum conduction voltage drop of 1.316 V and a switching frequency of 100 kHz. The results demonstrated that the combination of a vacuum transistor and a solid-state transistor combines the advantages of both and benefits the performance of the power switch.

Integrated individual field electron nano-emitter array is severely desiderated in vacuum nanoelectronics devices. Electron beam modulation is essential for collimation in gated field electron sources. Herein, we report the fabrication of aligned MEMS-type apertures on the individual gated Si nanotip array. Simulations of electron trajectories were employed for optimizing the thickness and radius of the apertures to achieve well modulation of electron beam. Accurate optical alignment between single aperture and the individual gated nano-tip was carried out during anodic bonding. Field emission test shows a well control of electron transmission rate by the modulator voltage. The work provides an opportunity for developing fast switching, addressable and precisely adjustable nano-cathode for vacuum nano-electronic applications.

In this paper we report on an improved measurement and analysis method for determining the emission current distribution of field emitter arrays with CMOS sensors. It can also be used for field emission arrays where not all surfaces of the emitters are at the same electrical potential (e.g. for p-doped Si tips, where a strong current saturation occurs). To demonstrate the functionality of this method, a n-doped field emission array was measured using a variable external series resistance. Brightness variations in emission spots were analyzed to re-calculate the known series resistances for comparison. The re-calculated value is in good agreement with the actual value of the resistance. This method offers a quantitative approach to assess internal voltage drop effects on field emission using optical readout

Cold cathode vacuum flat panel photodetectors have the advantages of low dark current, high sensitivity and fast response. The performance degradations of photodetectors under high temperature are particularly crucial for use in various applications especially targeting harsh environmental scenarios. In this study, a vacuum flat panel photodetector formed by a ZnO nanowire field emitter array and a ZnS photoconductor was fabricated and achieved a high responsivity of 4.4 A/W for 365 nm light owing to the electron bombardment induced photoconductivity mechanism. The performance variation of the device was evaluated in the temperature range from room temperature to 150 °C. The devices demonstrated a highly stable dark current and an improved photo-detectivity, demonstrating cold cathode vacuum photodetector has good tolerance to high-temperature.

We demonstrate an on-chip vacuum nano-diode with a single-crystal CsPbBr3 cathode (thickness ~0.9 μm) and Si-tip anode (separation ~30 nm) for direct electron detection. At 15 V bias, it exhibits a dark current of 100 pA, current on/off ratio of 490 and electron efficiency of 33.1% under 10 keV electron-beam irradiation. Numerical simulations confirm full depletion of the cathode. The built-in field in the cathode facilitates rabid separation of electron-hole pairs generated by the injected electrons, while the generated electron supply for field emission. The vacuum diode shows promising potential for developing on-chip integrated diode array for ultrafast electron detection.

Precise active control of field electron emission was achieved by a p-type Si-tip integrated with vertically stacked two gates, i.e., modulation gate at the bottom and extraction gate at the top. The modulation gate voltage controls the carrier distribution and transport in the substrate and thus modulates the current supply, while the extraction gate voltage induces the electron emission from the Si-tip. The double-gated device was fabricated using IC-compatible process with self-aligned method. The emission current was well-controlled with a high I-on / I-off=747 by a V-m of - 9 similar to 6 V and V-e of 80 V. A precise on-state current control accuracy of 32.8 pA/mV with well stability was achieved. The device would greatly facilitate its applications in modern vacuum nanoelectronics.