Nanomaterials

Research

12 pages, 5113 KiB

Open AccessArticle

Construction of CNT-MgO-Ag-BaO Nanocomposite with Enhanced Field Emission and Hydrogen Sensing Performances

by Xingzhen Liu, Weijin Qian, Yawei Chen, Mingliang Dong, Taxue Yu, Weijun Huang and Changkun Dong

Nanomaterials 2023, 13(5), 885; https://doi.org/10.3390/nano13050885 - 27 Feb 2023

Cited by 3 | Viewed by 1646

Abstract

CNTs and CNT-MgO, CNT-MgO-Ag, and CNT-MgO-Ag-BaO nanocomposites were grown on alloy substrates using an electrophoretic deposition method and their field emission (FE) and hydrogen sensing performances were investigated. The obtained samples were characterized by SEM, TEM, XRD, Raman, and XPS characterizations. The CNT-MgO-Ag-BaO [...] Read more.

CNTs and CNT-MgO, CNT-MgO-Ag, and CNT-MgO-Ag-BaO nanocomposites were grown on alloy substrates using an electrophoretic deposition method and their field emission (FE) and hydrogen sensing performances were investigated. The obtained samples were characterized by SEM, TEM, XRD, Raman, and XPS characterizations. The CNT-MgO-Ag-BaO nanocomposites showed the best FE performance with turn-on and threshold fields of 3.32 and 5.92 V.μm⁻¹, respectively. The enhanced FE performances are mainly attributed to the reductions of the work function, and the enhancement of the thermal conductivity and emission sites. The current fluctuation of CNT-MgO-Ag-BaO nanocomposites was only 2.4% after a 12 h test at the pressure of 6.0 × 10⁻⁶ Pa. In addition, for the hydrogen sensing performances, the CNT-MgO-Ag-BaO sample showed the best increase in amplitude of the emission current among all the samples, with the mean I_N increases of 67%, 120%, and 164% for 1, 3, and 5 min emissions, respectively, under the initial emission currents of about 1.0 μA. Full article

(This article belongs to the Special Issue The Research Related to Nanomaterial Cold Cathode)

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14 pages, 2323 KiB

Open AccessArticle

Simulation and Optimization of CNTs Cold Cathode Emission Grid Structure

by Yang Zhang, Xinchuan Liu, Liye Zhao, Yuanxun Li and Zhenjun Li

Nanomaterials 2023, 13(1), 50; https://doi.org/10.3390/nano13010050 - 22 Dec 2022

Cited by 6 | Viewed by 2205

Abstract

Carbon nanotubes (CNTs) show significant advantages in the development of cold cathode X-ray tubes due to their excellent field emission performance; however, there are still some problems, such as short lifetime and the low emission current of large-area CNTs. In this paper, a [...] Read more.

Carbon nanotubes (CNTs) show significant advantages in the development of cold cathode X-ray tubes due to their excellent field emission performance; however, there are still some problems, such as short lifetime and the low emission current of large-area CNTs. In this paper, a front-grid carbon nanotube array model was established, and the electric field intensity near the tip of the CNTs’ electric field enhancement factor was analytically calculated. A simulation model of a CNT three-dimensional field emission electron gun was established by using computer simulation technology (CST). The effects of grid wire diameter, grid aperture shape, and the distribution of grid projection on the cathode surface on the cathode current, anode current, and electron transmission efficiency were analyzed. The aperture ratio was used to evaluate the grid performance, and the simulation results show that the ideal aperture ratio should be between

65 %

and

85 %

. A grid structure combining a coarse grid and a fine grid was designed, which can make the electric field intensity around the grid evenly distributed, and effectively increased the cathode emission current by

24.2 %

compared with the structure without the fine grid. The effect of grid aperture ratio on the electron transmission efficiency was tested. The simulation results and optimized structure can provide a reference for the grid design of cold cathode emission X-ray tubes. Full article

(This article belongs to the Special Issue The Research Related to Nanomaterial Cold Cathode)

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12 pages, 3595 KiB

Open AccessArticle

Patterning of Silicon Substrate with Self-Assembled Monolayers Using Vertically Aligned Carbon Nanotube Electron Sources

by Yi Yin Yu, Alfi Rodiansyah, Jaydip Sawant and Kyu Chang Park

Nanomaterials 2022, 12(24), 4420; https://doi.org/10.3390/nano12244420 - 11 Dec 2022

Cited by 2 | Viewed by 2146

Abstract

We introduce a novel patterning technique based on e-beam lithography using vertically aligned carbon nanotube (VACNT) emitters with self-assembled monolayers (SAMs). A 20 μm line width of silicon wafer patterning was successfully demonstrated using octadecyl trichlorosilane (OTS) as a photoresist. To investigate surface [...] Read more.

We introduce a novel patterning technique based on e-beam lithography using vertically aligned carbon nanotube (VACNT) emitters with self-assembled monolayers (SAMs). A 20 μm line width of silicon wafer patterning was successfully demonstrated using octadecyl trichlorosilane (OTS) as a photoresist. To investigate surface modification by the irradiated electrons from the emitters, both contact angle measurement and energy dispersive X-ray (EDX) analysis were conducted. The patterning mechanism of the electron beam irradiated on OTS-coated substrate by our cold cathode electron beam (C-beam) was demonstrated by the analyzed results. The effect of current density and exposure time on the OTS patterning was studied and optimized for the Si wafer patterning in terms of the electronic properties of the VACNTs. The authors expect the new technique to contribute to the diverse applications to microelectromechanical (MEMS) technologies owing to the advantages of facile operation and precise dose control capability based on field electron emission current from the VACNT emitter arrays. Full article

(This article belongs to the Special Issue The Research Related to Nanomaterial Cold Cathode)

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14 pages, 3776 KiB

Open AccessArticle

Beam Trajectory Analysis of Vertically Aligned Carbon Nanotube Emitters with a Microchannel Plate

by Bishwa Chandra Adhikari, Bhotkar Ketan, Ju Sung Kim, Sung Tae Yoo, Eun Ha Choi and Kyu Chang Park

Nanomaterials 2022, 12(23), 4313; https://doi.org/10.3390/nano12234313 - 5 Dec 2022

Cited by 8 | Viewed by 2497

Abstract

Vertically aligned carbon nanotubes (CNTs) are essential to studying high current density, low dispersion, and high brightness. Vertically aligned 14 × 14 CNT emitters are fabricated as an island by sputter coating, photolithography, and the plasma-enhanced chemical vapor deposition process. Scanning electron microscopy [...] Read more.

Vertically aligned carbon nanotubes (CNTs) are essential to studying high current density, low dispersion, and high brightness. Vertically aligned 14 × 14 CNT emitters are fabricated as an island by sputter coating, photolithography, and the plasma-enhanced chemical vapor deposition process. Scanning electron microscopy is used to analyze the morphology structures with an average height of 40 µm. The field emission microscopy image is captured on the microchannel plate (MCP). The role of the microchannel plate is to determine how the high-density electron beam spot is measured under the variation of voltage and exposure time. The MCP enhances the field emission current near the threshold voltage and protects the CNT from irreversible damage during the vacuum arc. The high-density electron beam spot is measured with an FWHM of 2.71 mm under the variation of the applied voltage and the exposure time, respectively, which corresponds to the real beam spot. This configuration produces the beam trajectory with low dispersion under the proper field emission, which could be applicable to high-resolution multi-beam electron microscopy and high-resolution X-ray imaging technology. Full article

(This article belongs to the Special Issue The Research Related to Nanomaterial Cold Cathode)

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11 pages, 1965 KiB

Open AccessArticle

High Responsivity Vacuum Nano-Photodiode Using Single-Crystal CsPbBr₃ Micro-Sheet

by Xiangjun Zeng, Shasha Li, Zairan Liu, Yang Chen, Jun Chen, Shaozhi Deng, Fei Liu and Juncong She

Nanomaterials 2022, 12(23), 4205; https://doi.org/10.3390/nano12234205 - 26 Nov 2022

Cited by 2 | Viewed by 1769

Abstract

Field electron emission vacuum photodiode is promising for converting free-space electromagnetic radiation into electronic signal within an ultrafast timescale due to the ballistic electron transport in its vacuum channel. However, the low photoelectric conversion efficiency still hinders the popularity of vacuum photodiode. Here, [...] Read more.

Field electron emission vacuum photodiode is promising for converting free-space electromagnetic radiation into electronic signal within an ultrafast timescale due to the ballistic electron transport in its vacuum channel. However, the low photoelectric conversion efficiency still hinders the popularity of vacuum photodiode. Here, we report an on-chip integrated vacuum nano-photodiode constructed from a Si-tip anode and a single-crystal CsPbBr₃ cathode with a nano-separation of ~30 nm. Benefiting from the nanoscale vacuum channel and the high surface work function of the CsPbBr₃ (4.55 eV), the vacuum nano-photodiode exhibits a low driving voltage of 15 V with an ultra-low dark current (50 pA). The vacuum nano-photodiode demonstrates a high photo responsivity (1.75 AW⁻¹@15 V) under the illumination of a 532-nm laser light. The estimated external quantum efficiency is up to 400%. The electrostatic field simulation indicates that the CsPbBr₃ cathode can be totally depleted at an optimal thickness. The large built-in electric field in the depletion region facilitates the dissociation of photoexcited electron–hole pairs, leading to an enhanced photoelectric conversion efficiency. Moreover, the voltage drop in the vacuum channel increases due to the photoconductive effect, which is beneficial to the narrowing of the vacuum barrier for more efficient electron tunneling. This device shows great promise for the development of highly sensitive perovskite-based vacuum opto-electronics. Full article

(This article belongs to the Special Issue The Research Related to Nanomaterial Cold Cathode)

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10 pages, 3738 KiB

Open AccessArticle

Extreme Ultraviolet Lighting Using Carbon Nanotube-Based Cold Cathode Electron Beam

by Sung Tae Yoo and Kyu Chang Park

Nanomaterials 2022, 12(23), 4134; https://doi.org/10.3390/nano12234134 - 23 Nov 2022

Cited by 9 | Viewed by 1919

Abstract

Laser-based plasma studies that apply photons to extreme ultraviolet (EUV) generation are actively being conducted, and studies by direct electron irradiation on Sn for EUV lighting have rarely been attempted. Here, we demonstrate a novel method of EUV generation by irradiating Sn with [...] Read more.

Laser-based plasma studies that apply photons to extreme ultraviolet (EUV) generation are actively being conducted, and studies by direct electron irradiation on Sn for EUV lighting have rarely been attempted. Here, we demonstrate a novel method of EUV generation by irradiating Sn with electrons emitted from a carbon nanotube (CNT)-based cold cathode electron beam (C-beam). Unlike a single laser source, electrons emitted from about 12,700 CNT emitters irradiated the Sn surface to generate EUV and control its intensity. EUV light generated by direct irradiation of electrons was verified using a photodiode equipped with a 150 nm thick Zr filter and patterning of polymethyl methacrylate (PMMA) photoresist. EUV generated with an input power of 6 W is sufficient to react the PMMA with exposure of 30 s. EUV intensity changes according to the anode voltage, current, and electron incident angle. The area reaching the Sn and penetration depth of electrons are easily adjusted. This method could be the cornerstone for advanced lithography for semiconductor fabrication and high-resolution photonics. Full article

(This article belongs to the Special Issue The Research Related to Nanomaterial Cold Cathode)

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10 pages, 4675 KiB

Open AccessEditor’s ChoiceArticle

Achieving High Current Stability of Gated Carbon Nanotube Cold Cathode Electron Source Using IGBT Modulation for X-ray Source Application

by Yajie Guo, Junfan Wang, Baohong Li, Yu Zhang, Shaozhi Deng and Jun Chen

Nanomaterials 2022, 12(11), 1882; https://doi.org/10.3390/nano12111882 - 31 May 2022

Cited by 8 | Viewed by 2644

Abstract

The cold cathode X-ray source has potential application in the field of radiotherapy, which requires a stable dose. In this study, a gated carbon nanotube cold cathode electron gun with high current stability was developed by using Insulated Gate Bipolar Transistor (IGBT) modulation, [...] Read more.

The cold cathode X-ray source has potential application in the field of radiotherapy, which requires a stable dose. In this study, a gated carbon nanotube cold cathode electron gun with high current stability was developed by using Insulated Gate Bipolar Transistor (IGBT) modulation, and its application in X-ray source was explored. Carbon nanotube (CNTs) films were prepared directly on stainless steel substrate by chemical vapor deposition and assembled with control gate and focus electrodes to form an electron gun. A maximum cathode current of 200 μA and approximately 53% transmission rate was achieved. An IGBT was used to modulate and stabilize the cathode current. High stable cathode current with fluctuation less than 0.5% has been obtained for 50 min continuous operation. The electron gun was used in a transmission target X-ray source and a stable X-ray dose rate was obtained. Our study demonstrates the feasibility of achieving high current stability from a gated carbon nanotube cold cathode electron source using IGBT modulation for X-ray source application. Full article

(This article belongs to the Special Issue The Research Related to Nanomaterial Cold Cathode)

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12 pages, 3344 KiB

Open AccessArticle

Effects of Substrates on Nucleation, Growth and Electrical Property of Vertical Few-Layer Graphene

by Tianzeng Hong, Chan Guo, Yu Zhang, Runze Zhan, Peng Zhao, Baohong Li and Shaozhi Deng

Nanomaterials 2022, 12(6), 971; https://doi.org/10.3390/nano12060971 - 15 Mar 2022

Cited by 6 | Viewed by 2063

Abstract

A key common problem for vertical few-layer graphene (VFLG) applications in electronic devices is the solution to grow on substrates. In this study, four kinds of substrates (silicon, stainless-steel, quartz and carbon-cloth) were examined to understand the mechanism of the nucleation and growth [...] Read more.

A key common problem for vertical few-layer graphene (VFLG) applications in electronic devices is the solution to grow on substrates. In this study, four kinds of substrates (silicon, stainless-steel, quartz and carbon-cloth) were examined to understand the mechanism of the nucleation and growth of VFLG by using the inductively-coupled plasma-enhanced chemical vapor deposition (ICPCVD) method. The theoretical and experimental results show that the initial nucleation of VFLG was influenced by the properties of the substrates. Surface energy and catalysis of substrates had a significant effect on controlling nucleation density and nucleation rate of VFLG at the initial growth stage. The quality of the VFLG sheet rarely had a relationship with this kind of substrate and was prone to being influenced by growth conditions. The characterization of conductivity and field emissions for a single VFLG were examined in order to understand the influence of substrates on the electrical property. The results showed that there was little difference in the conductivity of the VFLG sheet grown on the four substrates, while the interfacial contact resistance of VFLG on the four substrates showed a tremendous difference due to the different properties of said substrates. Therefore, the field emission characterization of the VFLG sheet grown on stainless-steel substrate was the best, with the maximum emission current of 35 µA at a 160 V/μm electrostatic field. This finding highlights the controllable interface of between VFLG and substrates as an important issue for electrical application. Full article

(This article belongs to the Special Issue The Research Related to Nanomaterial Cold Cathode)

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10 pages, 3767 KiB

Open AccessArticle

Pixelated Vacuum Flat Panel Detector Using ZnS Photoconductor and ZnO Nanowires Cold Cathode

by Delin Hu, Xingpeng Bai, Chengyun Wang, Zhipeng Zhang, Xiaojie Li, Guofu Zhang, Shaozhi Deng and Jun Chen

Nanomaterials 2022, 12(5), 884; https://doi.org/10.3390/nano12050884 - 7 Mar 2022

Viewed by 2473

Abstract

Vacuum flat panel detectors (VFPDs) using cold cathode have important applications in large-area photoelectric detection. Based on the electron-bombardment-induced photoconductivity (EBIPC) mechanism, the photoconductor-type VFPDs achieved high detection sensitivity. However, pixelated imaging devices have not yet been developed. In this paper, we fabricate [...] Read more.

Vacuum flat panel detectors (VFPDs) using cold cathode have important applications in large-area photoelectric detection. Based on the electron-bombardment-induced photoconductivity (EBIPC) mechanism, the photoconductor-type VFPDs achieved high detection sensitivity. However, pixelated imaging devices have not yet been developed. In this paper, we fabricate a 4 × 7 pixel vacuum flat panel detector array made of ZnS photoconductor and ZnO nanowires cold cathode for an imaging application. The responsivity of the device and the pixel current uniformity are studied, and imaging of the patterned objects is achieved. Our results verify the feasibility of VFPDs for imaging. Full article

(This article belongs to the Special Issue The Research Related to Nanomaterial Cold Cathode)

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9 pages, 21548 KiB

Open AccessArticle

Field Emission of Multi-Walled Carbon Nanotubes from Pt-Assisted Chemical Vapor Deposition

by Hongbin Tang, Ruizi Liu, Weijun Huang, Wei Zhu, Weijin Qian and Changkun Dong

Nanomaterials 2022, 12(3), 575; https://doi.org/10.3390/nano12030575 - 8 Feb 2022

Cited by 6 | Viewed by 2223

Abstract

Multi-walled carbon nanotubes (MWNTs) were grown directly on a metal substrate with the assistance of Pt using a chemical vapor deposition method. In addition, the growth mechanism of Pt-assisted catalytic CNT was discussed. MWNTs were characterized by SEM, TEM, AFM, Raman, and EDS, [...] Read more.

Multi-walled carbon nanotubes (MWNTs) were grown directly on a metal substrate with the assistance of Pt using a chemical vapor deposition method. In addition, the growth mechanism of Pt-assisted catalytic CNT was discussed. MWNTs were characterized by SEM, TEM, AFM, Raman, and EDS, and the field emission (FE) properties were investigated, comparing with the direct grown MWNTs. The results showed that CNTs could not been synthesized by Pt particles alone under the experimental condition, but Pt may accelerate the decomposition of the carbon source gas, i.e., assisting MWNT growth with other catalysts. The Pt-assisted MWNTs were longer with larger diameters of around 80 nm and possessed better structural qualities with very few catalyst particles inside. Improved field emission properties were demonstrated for the Pt-assisted MWNTs with lower turn-on fields (for 0.01 mA·cm⁻² current density) of 2.0 V·μm⁻¹ and threshold field (for 10 mA·cm⁻² current density) of 3.5 V·μm⁻¹, as well as better stability under a long-term test of 80 h (started at 3.0 mA for the Pt-assisted emitter and 3.25 mA for the direct grown emitter). This work demonstrated a promising approach to develop high performance CNT field emitters for device applications. Full article

(This article belongs to the Special Issue The Research Related to Nanomaterial Cold Cathode)

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11 pages, 4029 KiB

Open AccessArticle

Investigation of the Pulsing Characteristic of a Carbon Nanotube Emitter

by Helin Zhu, Jejin Jang, Gyuwan Im, Hyungsoo Mok, Jehwang Ryu and Kyung-Seo Kim

Nanomaterials 2022, 12(3), 522; https://doi.org/10.3390/nano12030522 - 2 Feb 2022

Cited by 2 | Viewed by 1950

Abstract

The carbon nanotube (CNT) field emitter is suitable for the high frequency pulsing of X-ray. Pulsing reduces 49% of the dose in grid-controlled fluoroscopy and improves the image of moving objects. Various structures and manufacturing processes are being studied. However, more studies on [...] Read more.

The carbon nanotube (CNT) field emitter is suitable for the high frequency pulsing of X-ray. Pulsing reduces 49% of the dose in grid-controlled fluoroscopy and improves the image of moving objects. Various structures and manufacturing processes are being studied. However, more studies on the dynamic characteristic of a pulsing CNT and its application are needed. In this study, the combined dynamics including the field emission, MOSFET, and modified gate driver for MOSFET have been analyzed. In this configuration, between the cathode of the tube and ground, there is a MOSFET switch that turns the tube current on/off and a shunt resistor that measures the tube current. Due to the high impedance of the vacuum between the gate and cathode of the tube, about 85% of the gate voltage is still exerted between the Gate and cathode of the tube during the off-state of the MOSFET. Therefore, space charges are built during the off-state and then released at the beginning of the on-state of the MOSFET. The modified gate driver structure for MOSFET that we propose in this paper can limit the amount of current flow through the cathode. Tube current (boosted current) can be accurately controlled through a modified gate driver structure. Combining the boosted current and pulse control of MOSFET, the dynamic current performance of a CNT tube can be enhanced and the average tube current or dose can be accurately controlled. Experiments, simulation, and analysis have been conducted to study the combined dynamics and its applications. Full article

(This article belongs to the Special Issue The Research Related to Nanomaterial Cold Cathode)

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12 pages, 2217 KiB

Open AccessArticle

Subtractive Low-Temperature Preparation Route for Porous SiO₂ Used for the Catalyst-Assisted Growth of ZnO Field Emitters

by Stefanie Haugg, Carina Hedrich, Robert H. Blick and Robert Zierold

Nanomaterials 2021, 11(12), 3357; https://doi.org/10.3390/nano11123357 - 10 Dec 2021

Cited by 1 | Viewed by 2366

Abstract

The possibility to gradually increase the porosity of thin films facilitates a variety of applications, such as anti-reflective coatings, diffusion membranes, and the herein investigated tailored nanostructuring of a substrate for subsequent self-assembly processes. A low-temperature (<160 °C) preparation route for porous silicon [...] Read more.

The possibility to gradually increase the porosity of thin films facilitates a variety of applications, such as anti-reflective coatings, diffusion membranes, and the herein investigated tailored nanostructuring of a substrate for subsequent self-assembly processes. A low-temperature (<160 °C) preparation route for porous silicon oxide (porSiO₂) thin films with porosities of about 60% and effective refractive indices down to 1.20 is tailored for bulk as well as free-standing membranes. Subsequently, both substrate types are successfully employed for the catalyst-assisted growth of nanowire-like zinc oxide (ZnO) field emitters by metal organic chemical vapor deposition. ZnO nanowires can be grown with a large aspect ratio and exhibit a good thermal and chemical stability, which makes them excellent candidates for field emitter arrays. We present a method that allows for the direct synthesis of nanowire-like ZnO field emitters on free-standing membranes using a porSiO₂ template. Besides the application of porSiO₂ for the catalyst-assisted growth of nanostructures and their use as field emission devices, the herein presented general synthesis route for the preparation of low refractive index films on other than bulk substrates—such as on free-standing, ultra-thin membranes—may pave the way for the employment of porSiO₂ in micro-electro-mechanical systems. Full article

(This article belongs to the Special Issue The Research Related to Nanomaterial Cold Cathode)

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13 pages, 4084 KiB

Open AccessEditor’s ChoiceArticle

Nanocone-Shaped Carbon Nanotubes Field-Emitter Array Fabricated by Laser Ablation

by Jiuzhou Zhao, Zhenjun Li, Matthew Thomas Cole, Aiwei Wang, Xiangdong Guo, Xinchuan Liu, Wei Lyu, Hanchao Teng, Yunpeng Qv, Guanjiang Liu, Ke Chen, Shenghan Zhou, Jianfeng Xiao, Yi Li, Chi Li and Qing Dai

Nanomaterials 2021, 11(12), 3244; https://doi.org/10.3390/nano11123244 - 29 Nov 2021

Cited by 9 | Viewed by 2638

Abstract

The nanocone-shaped carbon nanotubes field-emitter array (NCNA) is a near-ideal field-emitter array that combines the advantages of geometry and material. In contrast to previous methods of field-emitter array, laser ablation is a low-cost and clean method that does not require any photolithography or [...] Read more.

The nanocone-shaped carbon nanotubes field-emitter array (NCNA) is a near-ideal field-emitter array that combines the advantages of geometry and material. In contrast to previous methods of field-emitter array, laser ablation is a low-cost and clean method that does not require any photolithography or wet chemistry. However, nanocone shapes are hard to achieve through laser ablation due to the micrometer-scale focusing spot. Here, we develop an ultraviolet (UV) laser beam patterning technique that is capable of reliably realizing NCNA with a cone-tip radius of ≈300 nm, utilizing optimized beam focusing and unique carbon nanotube–light interaction properties. The patterned array provided smaller turn-on fields (reduced from 2.6 to 1.6 V/μm) in emitters and supported a higher (increased from 10 to 140 mA/cm²) and more stable emission than their unpatterned counterparts. The present technique may be widely applied in the fabrication of high-performance CNTs field-emitter arrays. Full article

(This article belongs to the Special Issue The Research Related to Nanomaterial Cold Cathode)

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11 pages, 4039 KiB

Open AccessArticle

Fully Vacuum-Sealed Diode-Structure Addressable ZnO Nanowire Cold Cathode Flat-Panel X-ray Source: Fabrication and Imaging Application

by Chengyun Wang, Guofu Zhang, Yuan Xu, Yicong Chen, Shaozhi Deng and Jun Chen

Nanomaterials 2021, 11(11), 3115; https://doi.org/10.3390/nano11113115 - 18 Nov 2021

Cited by 11 | Viewed by 2540

Abstract

A fully vacuum-sealed addressable flat-panel X-ray source based on ZnO nanowire field emitter arrays (FEAs) was fabricated. The device has a diode structure composed of cathode panel and anode panel. ZnO nanowire cold cathodes were prepared on strip electrodes on a cathode panel [...] Read more.

A fully vacuum-sealed addressable flat-panel X-ray source based on ZnO nanowire field emitter arrays (FEAs) was fabricated. The device has a diode structure composed of cathode panel and anode panel. ZnO nanowire cold cathodes were prepared on strip electrodes on a cathode panel and Mo thin film strips were prepared on an anode panel acting as the target. Localized X-ray emission was realized by cross-addressing of cathode and anode electrodes. A radiation dose rate of 10.8 μGy/s was recorded at the anode voltage of 32 kV. The X-ray imaging of objects using different addressing scheme was obtained and the imaging results were analyzed. The results demonstrated the feasibility of achieving addressable flat-panel X-ray source using diode-structure for advanced X-ray imaging. Full article

(This article belongs to the Special Issue The Research Related to Nanomaterial Cold Cathode)

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10 pages, 32911 KiB

Open AccessEditor’s ChoiceArticle

Stable Field Emission from Vertically Oriented SiC Nanoarrays

by Jianfeng Xiao, Jiuzhou Zhao, Guanjiang Liu, Mattew Thomas Cole, Shenghan Zhou, Ke Chen, Xinchuan Liu, Zhenjun Li, Chi Li and Qing Dai

Nanomaterials 2021, 11(11), 3025; https://doi.org/10.3390/nano11113025 - 11 Nov 2021

Cited by 8 | Viewed by 2632

Abstract

Silicon carbide (SiC) nanostructure is a type of promising field emitter due to high breakdown field strength, high thermal conductivity, low electron affinity, and high electron mobility. However, the fabrication of the SiC nanotips array is difficult due to its chemical inertness. Here [...] Read more.

Silicon carbide (SiC) nanostructure is a type of promising field emitter due to high breakdown field strength, high thermal conductivity, low electron affinity, and high electron mobility. However, the fabrication of the SiC nanotips array is difficult due to its chemical inertness. Here we report a simple, industry-familiar reactive ion etching to fabricate well-aligned, vertically orientated SiC nanoarrays on 4H-SiC wafers. The as-synthesized nanoarrays had tapered base angles >60°, and were vertically oriented with a high packing density >10⁷ mm⁻² and high-aspect ratios of approximately 35. As a result of its high geometry uniformity—5% length variation and 10% diameter variation, the field emitter array showed typical turn-on fields of 4.3 V μm⁻¹ and a high field-enhancement factor of ~1260. The 8 h current emission stability displayed a mean current fluctuation of 1.9 ± 1%, revealing excellent current emission stability. The as-synthesized emitters demonstrate competitive emission performance that highlights their potential in a variety of vacuum electronics applications. This study provides a new route to realizing scalable field electron emitter production. Full article

(This article belongs to the Special Issue The Research Related to Nanomaterial Cold Cathode)

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10 pages, 3741 KiB

Open AccessArticle

Optically Induced Field-Emission Source Based on Aligned Vertical Carbon Nanotube Arrays

by Mengjie Li, Qilong Wang, Ji Xu, Jian Zhang, Zhiyang Qi and Xiaobing Zhang

Nanomaterials 2021, 11(7), 1810; https://doi.org/10.3390/nano11071810 - 12 Jul 2021

Cited by 7 | Viewed by 2451

Abstract

Due to the high field enhancement factor and photon-absorption efficiency, carbon nanotubes (CNTs) have been widely used in optically induced field-emission as a cathode. Here, we report vertical carbon nanotube arrays (VCNTAs) that performed as high-density electron sources. A combination of high applied [...] Read more.

Due to the high field enhancement factor and photon-absorption efficiency, carbon nanotubes (CNTs) have been widely used in optically induced field-emission as a cathode. Here, we report vertical carbon nanotube arrays (VCNTAs) that performed as high-density electron sources. A combination of high applied electric field and laser illumination made it possible to modulate the emission with laser pulses. When the bias electric field and laser power density increased, the emission process is sensitive to a power law of the laser intensity, which supports the emission mechanism of optically induced field emission followed by over-the-barrier emission. Furthermore, we determine a polarization dependence that exhibits a cosine behavior, which verifies the high possibility of optically induced field emission. Full article

(This article belongs to the Special Issue The Research Related to Nanomaterial Cold Cathode)

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11 pages, 2675 KiB

Open AccessArticle

A Cylindrical Triode Ultrahigh Vacuum Ionization Gauge with a Carbon Nanotube Cathode

by Jian Zhang, Jianping Wei, Detian Li, Huzhong Zhang, Yongjun Wang and Xiaobing Zhang

Nanomaterials 2021, 11(7), 1636; https://doi.org/10.3390/nano11071636 - 22 Jun 2021

Cited by 4 | Viewed by 2519

Abstract

In this study, a cylindrical triode ultrahigh vacuum ionization gauge with a screen-printed carbon nanotube (CNT) electron source was developed, and its metrological performance in different gases was systematically investigated using an ultrahigh vacuum system. The resulting ionization gauge with a CNT cathode [...] Read more.

In this study, a cylindrical triode ultrahigh vacuum ionization gauge with a screen-printed carbon nanotube (CNT) electron source was developed, and its metrological performance in different gases was systematically investigated using an ultrahigh vacuum system. The resulting ionization gauge with a CNT cathode responded linearly to nitrogen, argon, and air pressures in the range from ~4.0 ± 1.0 × 10⁻⁷ to 6 × 10⁻⁴ Pa, which is the first reported CNT emitter-based ionization gauge whose lower limit of pressure measurement is lower than its hot cathode counterpart. In addition, the sensitivities of this novel gauge were ~0.05 Pa⁻¹ for nitrogen, ~0.06 Pa⁻¹ for argon, and ~0.04 Pa⁻¹ for air, respectively. The trend of sensitivity with anode voltage, obtained by the experimental method, was roughly consistent with that gained through theoretical simulation. The advantages of the present sensor (including low power consumption for electron emissions, invisible to infrared light radiation and thermal radiation, high stability, etc.) mean that it has potential applications in space exploration. Full article

(This article belongs to the Special Issue The Research Related to Nanomaterial Cold Cathode)

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