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257 results on '"Wei, Xianlong"'

1. A Cascade Electron Source Based on Series Horizontal Tunneling Junctions

Author

Li, Zhiwei and Wei, Xianlong

Subjects
Physics - Applied Physics
Abstract

On-chip electron sources have wide potential applications in miniature vacuum electronic devices and emission efficiency is one of their performance benchmarks. A cascade electron source based on series metal-insulator-metal horizontal tunneling junctions is proposed, where free electrons are additively extracted from each tunneling junction. A cascade electron source with n horizontal tunneling junctions shows a theoretical emission efficiency of approximately {\eta}(n)=1-(1-{\eta}_0 )^n, with {\eta}_0 being the efficiency of a single tunneling junction. Experimentally, a cascade electron source with three Si-SiOx-Si tunneling junctions is demonstrated, achieving an emission efficiency as high as 47.6%. This work provides a new way of realizing highly efficient on-chip electron sources., Comment: 4 pages, 3 figures

Published
2020
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3. Silicon Oxide Electron-Emitting Nanodiodes

Author

Wu, Gongtao, Li, Zhiwei, Tang, Zhiqiang, Wei, Dapeng, Zhang, Gengmin, Chen, Qing, Peng, Lian-Mao, and Wei, Xianlong

Subjects
Physics - Applied Physics, Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science
Abstract

Electrically driven on-chip electron sources that do not need to be heated have been long pursued because the current thermionic electron sources show the problems of high power consumption, slow temporal response, bulky size, etc., but their realization remains challenging. Here we show that a nanogap formed by two electrodes on a silicon oxide substrate functions as an electron-emitting nanodiode after the silicon oxide in the nanogap is electrically switched to a high-resistance conducting state. A nanodiode based on graphene electrodes can be turned on by a voltage of ~7 V in ~100 ns and show an emission current of up to several microamperes, corresponding to an emission density of ~10^6 A cm^-2 and emission efficiency as high as 16.6%. We attribute the electron emission to be generated from a metal-insulator-metal tunneling diode on the substrate surface formed by the rupture of conducting filaments in silicon oxide. An array of 100 nanodiodes exhibits a global emission density of 5 A cm^-2 and stable emission with negligible current degradation over tens of hours under modest vacuum. The combined advantages of a low operating voltage, fast temporal response, high emission density and efficiency, convenient fabrication and integration, and stable emission in modest vacuum make silicon oxide electron-emitting nanodiodes a promising on-chip alternative to thermionic emission sources., Comment: 15 pages, 3 figures, supporting informations, submitted to Advanced Electronic Materials on March 6th 2018

Published
2018
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9. Tunable Electron Emission From Back-Gated SiOx Tunneling Diodes for Addressable Devices

Author

Zhan, Fangyuan, Zhu, Taoyuan, Hu, Zhenyu, Zhang, Yan, Li, Zhiwei, Wang, Yuwei, and Wei, Xianlong

Abstract

Tunable electron emission from microemitters is highly desired for large-scale addressable vacuum devices. Here, we report tunable electron emission from both a single back-gated silicon tunneling diode (STD) and parallel back-gated STD arrays. Emission current of a back-gated STD emitter can be repeatedly tuned by six orders of magnitude with a subthreshold slope (SS) of 2.5 V/dec and negligible gate leakage current. The tunability of electron emission from STDs is mainly attributed to the bending of the energy band of STDs by the back gate. These results suggest that back-gated STDs are promising for applications in large-scale addressable vacuum devices.

Published
2024
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19. An On-Chip Microscale Vacuum Chamber with High Sealing Performance Using Graphene as Lateral Feedthrough.

Author

Yu, Panpan, Zhan, Fangyuan, Rao, Weidong, Zhao, Yanqing, Fang, Zheng, Tu, Zidong, Li, Zhiwei, Guo, Dengzhu, and Wei, Xianlong

Subjects
VACUUM chambers, GRAPHENE, BREAKDOWN voltage, ELECTRONIC equipment, BOND ratings, MONOMOLECULAR films
Abstract

On-chip microscale vacuum chambers with high sealing performance and electrical feedthroughs are highly desired for microscale vacuum electronic devices and other MEMS devices. In this paper, we report an on-chip microscale vacuum chamber which achieves a high sealing performance by using monolayer graphene as lateral electrical feedthrough. A vacuum chamber with the dimensions of π × 2 mm × 2 mm × 0.5 mm is fabricated by anodically bonding a glass chip with a through-hole between two Si chips in a vacuum, after monolayer graphene electrodes have been transferred to the surface of one of the Si chips. Benefiting from the atomic thickness of monolayer graphene, the leak rate of Si–glass bonding interface with a monolayer graphene feedthrough is measured at less than 2 × 10−11 Pa·m3/s. The monolayer graphene feedthrough exhibits a minor resistance increase from 22.5 Ω to 31 Ω after anodic bonding, showing good electrical conductance. The pressure of the vacuum chamber is estimated to be 185 Pa by measuring the breakdown voltage. Such a vacuum is found to maintain for more than 50 days without obvious degradation, implying a high sealing performance with a leak rate of less than 1.02 × 10−16 Pa·m3/s. [ABSTRACT FROM AUTHOR]

Published
2023
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21. Efficient and Dense Electron Emission from a SiO2 Tunneling Diode with Low Poisoning Sensitivity

Author

Li, Zhiwei, primary, Zhang, Zhengfeng, additional, Tian, Jiamin, additional, Wu, Gongtao, additional, He, Yidan, additional, Yu, Bocheng, additional, Zhan, Fangyuan, additional, Wang, Yuwei, additional, Sun, Mei, additional, Yang, Wei, additional, Li, Zhihong, additional, Chen, Qing, additional, Yan, Pengfei, additional, and Wei, Xianlong, additional

Published
2022
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27. A Miniaturized Ionization Vacuum Sensor Based on Thermionic Electron Emission From Carbon Nanotubes

Author

Wang, Yuwei, He, Yidan, Mao, Shuyu, Zhao, Zhenzheng, Yang, Wei, Liu, Peng, and Wei, Xianlong

Abstract

Traditional hot-cathode ionization vacuum sensor (IVS) has long suffered from bulky size and integration difficulties. Here, to overcome these problems, a hot-cathode IVS is scaled down to nail size by utilizing micro-electromechanical system (MEMS) technology and exploiting carbon nanotubes (CNTs) as microscale filaments for the first time. Silicon-based grid and ion collector are bonded vertically on the hot-cathode chip to form a compact and scalable MEMS-type device with dimensions of $13\times 9\times2.7$ mm. The ratio of ion current ( ${I}_{i}$ ) to emission current ( ${I}_{e}$ ) shows measurement linearity from 0.05 to 6.50 Pa. Also, benefiting from the good reproducibility of the CNT thermionic electron emission, a minor variation (< 10%) is observed when the vacuum level is toggled repeatedly between 0.02 and 1.00 Pa. All these features make our miniaturized hot-cathode IVS a promising device for vacuum detection.

Published
2023
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28. Pressure Sensitivity of Electron Emission from SiOx Tunneling Diodes and their Outstanding Emission Performance under Rough Vacuum.

Author

Zhan, Fangyuan, Li, Zhiwei, Yang, Wei, and Wei, Xianlong

Subjects
TUNNEL diodes, PARTIAL pressure, ELECTRON sources, ELECTRON emission, ELECTRONIC equipment, AIR pressure, FIELD emission, DIODES
Abstract

On‐chip electron sources with low pressure‐sensitivity and outstanding emission performances under rough vacuum are highly desired for developing miniature fully encapsulated vacuum electronic devices. Here, the sensitivity of electron emission from SiOx tunneling diodes formed in electroformed SiOx to the variation of ambient vacuum pressure from ≈10−4 to ≈102 Pa is explored. Electron emission from SiOx tunneling diodes is found to be insensitive to pressure variation when the pressure is lower than ≈10−1 Pa and exhibits fast degradation above the pressure, showing much lower pressure sensitivity than field emission sources. Despite emission current degradation above ≈10−1 Pa, SiOx tunneling diodes exhibit stable and reproducible electron emission under fixed rough vacuum up to 8 Pa, and good restorability after being repeatedly exposed to air pressure. By analyzing transport current of SiOx tunneling diodes under varying ambient vacuum pressure, the degradation of emission current above ≈10−1 Pa is attributed to the widening of insulating SiOx channel in the diode due to the transformation of Si conducting filament to SiOx with increasing oxygen partial pressure. [ABSTRACT FROM AUTHOR]

Published
2022
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29. SiO x Tunneling Diode Arrays With Uniform Electron Emission.

Author

Zhan, Fangyuan, Yang, Wei, Li, Zhiwei, He, Yidan, Yu, Panpan, Wang, Bingjie, and Wei, Xianlong

Subjects
ELECTRON emission, TUNNEL diodes, OPTICAL resolution, OPTICAL images, VISIBLE spectra, SPATIAL distribution (Quantum optics), TUNNEL design & construction, ELECTRON field emission
Abstract

Uniform electron emission (EE) from on-chip micro-emitter arrays based on SiOx tunneling diodes (STDs) in electroformed SiOx is reported. EE from STDs is found to be accompanied with visible light emission, which enables us to resolve the spatial distribution of EE from the micro-emitter arrays and emitter-to-emitter uniformity at the microscale resolution via optical imaging. Up to 99% micro-emitters in a 15 $\times15$ array is observed to work simultaneously with good emitter-to-emitter uniformity, showing an emission current of 0.56 mA and an emission density of 626 mA/cm2. The good uniformity is attributed to the insensitivity of EE from STDs to the microfabricated structures of micro-emitters. [ABSTRACT FROM AUTHOR]

Published
2022
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45. Efficient and Dense Electron Emission from a SiO2Tunneling Diode with Low Poisoning Sensitivity

Author

Li, Zhiwei, Zhang, Zhengfeng, Tian, Jiamin, Wu, Gongtao, He, Yidan, Yu, Bocheng, Zhan, Fangyuan, Wang, Yuwei, Sun, Mei, Yang, Wei, Li, Zhihong, Chen, Qing, Yan, Pengfei, and Wei, Xianlong

Abstract

We report a tunneling diode enabling efficient and dense electron emission from SiO2with low poisoning sensitivity. Benefiting from the shallow SiO2channel exposed to vacuum and the low electron affinity of SiO2(0.9 eV), hot electrons tunneling into the SiO2channel from the cathode of the diode are efficiently emitted into vacuum with much less restriction in both space and energy than those in previous tunneling electron sources. Monte Carlo simulations on the device performance show an emission efficiency as high as 87.0% and an emission density up to 3.0 × 105A/cm2. By construction of a tunneling diode based on Si conducting filaments in electroformed SiO2, an emission efficiency up to 83.7% and an emission density up to 4.4 × 105A/cm2are experimentally realized. Electron emission from the devices is demonstrated to be independent of vacuum pressure from 10–4to 10–1Pa without poisoning.

Published
2022
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50. Mechanical Properties of Si Nanowires as Revealed by in Situ Transmission Electron Microscopy and Molecular Dynamics Simulations

Author

Tang, Dai-Ming, Ren, Cui-Lan, Wang, Ming-Sheng, Wei, Xianlong, Kawamoto, Naoyuki, Liu, Chang, Bando, Yoshio, Mitome, Masanori, Fukata, Naoki, and Golberg, Dmitri

Abstract

Deformation and fracture mechanisms of ultrathin Si nanowires (NWs), with diameters of down to ∼9 nm, under uniaxial tension and bending were investigated by using in situ transmission electron microscopy and molecular dynamics simulations. It was revealed that the mechanical behavior of Si NWs had been closely related to the wire diameter, loading conditions, and stress states. Under tension, Si NWs deformed elastically until abrupt brittle fracture. The tensile strength showed a clear size dependence, and the greatest strength was up to 11.3 GPa. In contrast, under bending, the Si NWs demonstrated considerable plasticity. Under a bending strain of <14%, they could repeatedly be bent without cracking along with a crystalline-to-amorphous phase transition. Under a larger strain of >20%, the cracks nucleated on the tensed side and propagated from the wire surface, whereas on the compressed side a plastic deformation took place because of dislocation activities and an amorphous transition.

Published
2024
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