This work demonstrates wafer-scale fabricated on-chip thermionic electron sources utilizing a microscale Y2O3-Ir filament designed for robust operation in rough vacuum. By integrating electroplated Ir filaments on a glass wafer with a thermally evaporated Y2O3 layer, we achieve a maximum emission current density of 46.0 A/cm2. The devices demonstrate exceptional robustness in rough vacuum, sustaining stable electron emission for nearly 4 hours at vacuum level of 100 Pa. They exhibit lifetime improvements of 24 times and orders of magnitude, respectively, when compared with their counterparts based on pure Ir and W filaments. Our devices are promising for applications in on-chip vacuum electronic devices working in poor vacuum.

The atomic vapor cell is the core component of quantum sensing systems, enabling precise measurements through stable atomic reference transitions. While the optical path length of conventional wafer-level fabricated atomic vapor cells is typically less than 2 mm, this research presents wafer-level fabricated, all-glass micromachined atomic vapor cells with a significantly extended optical path length of 9 mm by ultrafast laser welding. An array of 24 such vapor cells with dimensions of 6 x 6 x 11.2 mm(3) was successfully fabricated on a 2-inch wafer. The atomic vapor cells were characterized using a compact optical frequency standard system based on modulation transfer spectroscopy (MTS), achieving a frequency stability of 5 x 10(-13) at 1 s. These results highlight the advantages of ultrafast laser welding in overcoming the optical path length limitations of traditional wafer-level fabricated vapor cells, providing a scalable solution for compact optical frequency standards and miniaturized quantum sensors.

Tunneling electron sources provide promising electron emitters for on-chip applications due to its low working voltage and high tolerance to low vacuum, but encounter the main challenges of low emission efficiency and low emission density. We discovered a new way of tunneling electron emission from horizontal tunneling diodes formed in electroformed silicon oxide. Here, we will present a review on the tunneling electron emission devices, including device structures, emission mechanism, realization methods, emission performances, and on-chip electron emitter arrays.

We report a wafer-level fabrication method for silicon oxide tunneling electron sources (SiOx TESs) based on electroburning. Using only 2-μm-precision UV lithography, we achieved 2-inch wafer-scale batch fabrication of arrayed SiOx TESs with ~100 nm nanogaps. A 15×15 array exhibits a maximum emission current of 57.9 μA at a collection voltage of 210 V, demonstrating good electron emission performance. This approach overcomes the electron beam lithography bottleneck and provides a scalable route for SiOx TES production.

Room-temperature direct wafer bonding is a key technology in integrated circuit manufacturing. However, existing technologies heavily rely on atomically flat, clean, and highly activated surfaces. Obtaining these conditions requires stringent wafer pretreatments and ultrahigh vacuum, which result in complex process flow, high equipment costs, and reduced yield. Herein, we report a room-temperature and atmospheric-pressure direct wafer bonding technology based on a front-expanding strategy for ultrafast laser bonding. This strategy enables the direct wafer bonding with tolerance to micron-scale air gaps, surface roughness, and wafer warpage by cyclically recognizing and bonding regions in quasi-optical contact. Direct bonding of a 6-inch borosilicate glass wafer to a silicon wafer is achieved, with a defect rate as low as 0.27%, bonding strength of up to 45.5 MPa, and a leak rate below 5 × 10 -11 Pa·m 3 /s. The ultrafast laser bonding technique is applicable to both homo- and heterogeneous bonding of various wafer materials including Si, borosilicate glass, quartz, sapphire, LiNbO 3 and SiC. Its utility is further demonstrated through the wafer-scale fabrication of MEMS rubidium atomic vapor cells. The elimination of stringent pretreatments, the capability for atmospheric-pressure bonding, and applicability to diverse wafer materials make the proposed method a promising and cost-effective route for room-temperature direct wafer bonding.

New types of miniature vacuum electron tubes are under intense study. Previously, planar nanoscale vacuum channel transistors (NVCTs) with resistive-switching (RS) SiOx electron sources have been developed, in which the current collected by the Collector electrode-and thus the ON/OFF state-can be well controlled by the voltage applied to the Grid electrode. In this work, the application potential of RS-based NVCTs for logic operations was explored. The Si substrate was utilized as the Back Grid electrode, and its modulation of the Collector current was studied. The subthreshold swing of the NVCT decreased as the Back Grid voltage was varied from algebraically low levels to algebraically high levels. A negative Back Grid voltage turned off the device when its magnitude was sufficiently large. A large number of electrons flowed to the Collector only when a large negative voltage was applied to the Grid and, simultaneously, a voltage of algebraically high level was applied to the Back Grid. As a result, a properly designed circuit centered on a dual-grid NVCT could work as a 'material-implication' logic gate. With the voltage on the Back Grid treated as the antecedent, p, and that on the Grid as the consequent, q, the voltage on the Collector behaved as the logic function 'p implies q'.

Electrical breakdown characteristics of microscale low-pressure air gaps within narrow quartz tubes are studied by an experimental methodology with the air pressure in the narrow tubes well adjusted and determined. Air breakdown in microscale narrow tubes is found to show a much higher breakdown voltage than that predicted by traditional Paschen's law. In contrast with traditional Paschen's law, the breakdown voltage of narrow air gap strongly depends on the dimensions of the tubular air gap with a higher breakdown voltage for larger gap-to-radius ratio. The deviations from traditional Paschen's law are attributed to electron loss from discharge space due to electron absorption by narrow tube walls. A theoretical model incorporating electron loss in tube walls is formulated to well describe air breakdown characteristics within narrow quartz tubes. The results provide a theoretical model for describing gas discharge of microscale narrow air gaps and a helpful guide for enhancing high-voltage robustness in microscale vacuum electronic devices.

Due to iridium (Ir) unique properties, it has been explored on several occasions as a functional material in high-tech fields. Herein, we utilized vertical electrodeposition process to deposit Ir films onto the micro-scale confined surfaces of 2-inch wafer from an aqueous electrolyte, achieving uniform coverage for on-chip cathode applications. The deposited films were systematically characterized using scanning electron microscopy, transmission electron microscopy, X-ray energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy to evaluate their microstructure, morphology, chemical composition, interface properties, and uniformity. Characteristically, the as-deposited Ir films exhibited a smooth and relatively dense surface morphology, with no obvious pores observed in the AFM images, and a root-mean-square roughness of approximately 5.9 nm, indicating a compact surface structure with an amorphous microstructure, maintaining predominantly metallic Ir character. Moreover, the films showed excellent continuity and uniformity across the wafer, with well-defined interfaces and homogeneous elemental distribution. Furthermore, thickness measurements revealed consistent deposition, with film thickness ranging from 856 to 1174 nm after 1 hour of wafer-level electrodeposition, corresponding to a thickness uniformity of 16.5%. Cumulatively, the current findings establish a reliable and scalable process for producing high-quality Ir films at the micro-scale confined surfaces of wafer scale, with precise control over film thickness and microstructure toward future advanced field applications.

Higher resolution and higher throughput are the relentless pursuits of lithography technologies for continued downscaling of semiconductor devices 1 . While the cutting-edge lithography technique for semiconductor manufacturing has evolved into extreme ultraviolet lithography (EUVL) 2, 3 , there is still no foreseeable lithography techniques for post-EUVL 4 . Electron lithography, as a candidate for post-EUVL, exhibits higher resolution (down to sub-2 nm 5-7 ) than that of EUVL, but encounters the main challenge of low throughput due to the trade-off between resolution and throughput resulting from the adoption of electron optics systems 8, 9 . Here, we report a diffuse electron projection lithography (DEPL) by adopting a wide diffuse electron beam in air as the exposure source and patterned monolayers of Au nanoparticles as the contact mask. Without the adoption of electron optics systems, the resolution and throughput of DEPL are decoupled and can be optimized independently. A minimum feature size of 4 nm and a throughput of 15 4-inch wafers per hour have been demonstrated by DEPL, with a potential throughput up to 532 12-inch wafers per hour. The outstanding features of high resolution, high throughput, and freedom from electron optics and ultrahigh vacuum systems make DEPL a promising and cost-effective lithography technique for post-EUVL.

This paper reports wafer-scale fabricated on-chip thermionic electron sources based on Y2O3-Ir filaments, which exhibit exceptional robustness in rough vacuum. The devices achieve a high emission current density of 46.0 A/cm2 and maintain stable operation for nearly 4 hours at 100 Pa. Compared to pure Ir and W filament-based counterparts, they demonstrate lifetime improvements of 24 times and orders of magnitude, respectively. This work provides a promising path toward robust, on-chip vacuum electronics operable in poor vacuum conditions.

Achieving high structural stability in on-chip electron sources is a critical breakthrough for practical implementations of miniaturized vacuum electronic devices. Here, we developed a novel thermionic electron sources fabricated via microfabrication techniques on BF33 glass wafers, demonstrating excellent dimensional uniformity. Unlike conventional suspended structures, our design adopts a substrate-contacted Y2O3-W filament architecture, which not only simplifies the fabrication processes but also significantly enhances mechanical robustness. The Y2O3 coating substantially improves emission performance, reducing the activation voltage by 0.5 V (from 2.1 V to 1.6 V) while achieving orders-ofmagnitude increase in emission current at identical filament voltages.

Two-dimensional (2D) materials with van der Waals stacking have been reported to have extraordinary mechanical and electromechanical properties, which give them revolutionary potential in various fields. However, due to the atomic-scale thickness of these 2D materials, their fascinating properties cannot be effectively characterized in many cases using conventional measurement techniques. Based on typical microscopy techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM), a range of in situ microscopy techniques have been developed to systematically quantify the mechanical and electromechanical properties of 2D materials. This review highlights the advancements of in situ microscopy techniques for studying elasticity and fracture, adhesion and separation, structural superlubricity, as well as c-axis piezoresistivity and rotation angle-related transport of 2D materials. The methods and results of various microscopy experiments, including nanoindentation using AFM, pressurized bubble tests, self-retraction experiments, pull-to-peel methods and so on, are compared, and their respective advantages and limitations are discussed. Finally, we summarize the current challenges in these microscopy techniques and outline development opportunities.

On-chip electron emission sources are essential for advancing miniaturized and integrated vacuum electronic devices. In this work, we present a novel on-chip electron source utilizing thermionic electron emission from a suspended Y2O3/TiN filament. These thermionic electron sources are batch-fabricated on silicon wafers using microfabrication technologies. Leveraging the low work function of Y2O3, our on-chip thermionic sources achieve an emission current of up to 1 mA and an emission density of up to 19.3 A/cm2 at a relatively low temperature of 1990 K. This performance significantly surpasses previously reported on-chip thermionic sources based on tungsten (W) and carbon nanomaterial filaments, which require higher temperatures for similar emission performance.

Achieving high structural stability in on-chip electron sources is a critical breakthrough for practical implementations of miniaturized vacuum electronic devices. Here, we developed a novel thermionic electron sources fabricated via microfabrication techniques on BF33 glass wafers, demonstrating excellent dimensional uniformity. Unlike conventional suspended structures, our design adopts a substrate-contacted $\mathrm{Y}_2 \mathrm{O}_3-\mathrm{W}$ filament architecture, which not only simplifies the fabrication processes but also significantly enhances mechanical robustness. The $\mathrm{Y}_2 \mathrm{O}_3$ coating substantially improves emission performance, reducing the activation voltage by 0.5 V (from 2.1 V to 1.6 V) while achieving orders-of-magnitude increase in emission current at identical filament voltages.

Ionic wind has shown promising applications in many fields, but it still encounters the challenges of low wind velocity and high discharge voltage. Here we propose a method of enhancing the velocity of ionic wind at given discharge voltages by Joule-heating the discharge electrode in a wire-grid corona discharge scheme. Ionic wind velocity is found to increase with the temperature of the discharge electrode with an enhancement by a magnitude of more than one order at low discharge voltages. Despite of additional energy consumption for Joule-heating, the overall energy efficiency of ionic wind production can be simultaneously enhanced. Numerical simulations indicate that the enhancement of ionic wind velocity is attributed to the increase of the mean free path of electron-molecule collisions and thus ion density near the hot electrode. Furthermore, we get a further ionic wind velocity enhancement by several times via covering the hot discharge electrode with Y2O3 film to increase electron density near the hot electrode by thermionic electron emission.

Constructing separate Li-ion and electron conduction pathways enabled high interfacial charge transfer kinetics, stability, and superior cycling stability.

The letter presents a MEMS-type ionization vacuum sensor fabricated in batch on 4-in wafers based on through glass via (TGV) technology. The utilization of TGV technology enables the sensor to exhibit a compact three-layer stacked structure, where an yttrium oxide thermionic electron emitter and an ion collector are assembled in the same TGV layer. In addition to the compact dimensions of only 14 x 9 x 3.6 mm(3), the wafer-scale fabricated sensors exhibit a wide measurement range from 1 x 10(-4) Pa to 40 Pa, an improved sensitivity of 0.019 Pa-1 and a production yield of 94%. All these results imply the promising applications of our sensors for vacuum measurement, especially for in-situ vacuum monitoring in vacuum electronic devices.

resistive switching (RS) offers promising applications in a variety of areas. In particular, silicon oxide (SiOx) under RS can serve as electron sources in new types of miniature vacuum electron tubes. In this work, planar nanoscale vacuum channel transistors (NVCTs) with graphene electrodes and RS SiOx electron sources were developed. With the gate voltage (VG) sweeping from 0 to −20 V, the obtained subthreshold swing (SS) of 76 mV/dec was quite close to the theoretical limit of the SS of a field effect transistor at room temperature (60 mV/dec). The largest ON/OFF ratio was of the order of 106. Furthermore, the back gate has good controllability over the collector current (IC). These results demonstrate the application potential of RS-NVCTs as either switching devices or amplifiers.