WO2022233093A1 - Microfocus field emission electron source based on carbon nanotube, and preparation method therefor - Google Patents

Microfocus field emission electron source based on carbon nanotube, and preparation method therefor Download PDF

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WO2022233093A1
WO2022233093A1 PCT/CN2021/108337 CN2021108337W WO2022233093A1 WO 2022233093 A1 WO2022233093 A1 WO 2022233093A1 CN 2021108337 W CN2021108337 W CN 2021108337W WO 2022233093 A1 WO2022233093 A1 WO 2022233093A1
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carbon nanotube
microfocus
electron source
field emission
nickel
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PCT/CN2021/108337
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Chinese (zh)
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董长昆
祝维
钱维金
黄卫军
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温州大学
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/02—Details
    • H01J37/04—Arrangements of electrodes and associated parts for generating or controlling the discharge, e.g. electron-optical arrangement, ion-optical arrangement
    • H01J37/06—Electron sources; Electron guns
    • H01J37/073—Electron guns using field emission, photo emission, or secondary emission electron sources
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
    • H01J9/02—Manufacture of electrodes or electrode systems
    • H01J9/022—Manufacture of electrodes or electrode systems of cold cathodes
    • H01J9/025—Manufacture of electrodes or electrode systems of cold cathodes of field emission cathodes

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  • the invention relates to a field emission electron source, in particular to a microfocus field emission electron source based on carbon nanotubes and a preparation method thereof.
  • Carbon nanotubes have excellent physical, chemical, structural and other properties, and are ideal field emission cathode materials. Compared with traditional metal tip (usually tungsten or molybdenum) emitters, they have tips that are almost close to the theoretical limit. Surface area, its tip size is only a few nanometers to tens of nanometers, it has a low field emission voltage (can be less than 100 volts), it can transmit extremely large current densities, and the current is stable and has a long service life, so it is very suitable as an excellent
  • the point electron source is used in the electron emission components of scanning electron microscope (Scanning Electron Microscope), transmission electron microscope (Transmission Electron Microscope), microfocus X-ray imager and other equipment.
  • the composite structure of graphene and CNT also showed certain advantages in improving the emission performance.
  • all kinds of CNT cold cathodes have good emission stability under the vacuum degree of less than 10 -6 Pa, stable emission under high pressure (P>10 -6 Pa) and high current is always a challenge.
  • micro-focus X-ray sources have appeared.
  • the micro-focus can prevent the blurring of X-ray images and provide sharp magnified images, which are used in X-ray non-destructive testing and other fields.
  • Microfocus ray sources have smaller focal sizes down to the micron level, minimizing image geometric unsharpness at high geometric magnifications to achieve resolutions up to micron level.
  • the focal point size of microfocus X-ray sources is still far from being small enough.
  • the purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art, and to provide a micro-focus field emission electron source based on carbon nanotubes and a preparation method thereof, the micro-focus field emission electron source has good strong current emission and high voltage Strong and stable characteristics.
  • the first object of the present invention is to provide a preparation method of a micro-focus field emission electron source based on carbon nanotubes.
  • the technical solution of the present invention is a preparation method of a carbon nanotube-based micro-focus field emission electron source, the cathode of which comprises the following steps:
  • a metal platinum layer is plated on the surface of the nickel substrate
  • a pulsed laser is used to ablate the surface of the nickel substrate coated with metal platinum with negative defocusing.
  • the laser focus is inside the nickel substrate, so that the internal nickel metal is melted. , which flows to the surface of the nickel substrate under the driving action of the nickel metal vapor and forms a spherical shell after cooling;
  • the carbon nanotube cathode film was directly grown on the spherical shell formed by laser ablation of the nickel substrate by chemical vapor deposition.
  • step (3) there is also a step (4): depositing graphene on the carbon nanotube cathode film by electrophoresis, and performing vacuum high temperature annealing.
  • the carbon nanotube cathode film is a multi-wall carbon nanotube cathode film.
  • pulsed laser ablation with negative defocus parameters wavelength 1064 nm, frequency 3 Hz, output current 50-150 A, and negative defocus distance at 0.00-0.50 In the mm range, this has a greater impact on the diameter and shape of the spherical shell.
  • the second object of the present invention is to provide a carbon nanotube-based microfocus field emission electron source prepared by the method.
  • the inner nickel metal flows to the surface to form a spherical shell with tiny dots protruding from the surface.
  • the material of the spherical shell is nickel, which has a catalytic effect, because chemical vapor deposition can form a carbon nanotube cathode film on the surface of the spherical shell of the nickel material, and the platinum layer on the edge of the spherical shell does not grow carbon nanotubes because it has no catalytic effect.
  • a thin film is formed, thereby forming carbon nanotubes with a controllable size, and by utilizing the field emission effect of the carbon nanotubes, the formed electron source has the effect of micro-focus technology with small size.
  • the micro-focus electron source of the technical solution of the present application has the advantages of low turn-on electric field ( ⁇ 1 V/ ⁇ m) and high current density ( ⁇ 1 A/cm 2 ).
  • ⁇ 1 V/ ⁇ m low turn-on electric field
  • ⁇ 1 A/cm 2 high current density
  • Figure 1 Decomposed schematic diagram of the preparation steps of the present invention, in which Figure 1 (a) magnetron sputtering platinum (b) laser ablation molten state (c) laser ablation solidified state (d) covered area of CNT thin film after growth by CVD ;
  • FIG. 3 Field emission test diagram, in which Fig. 3(a) E-J curve of field emission, (b) F-N curve, (d) imaging diagram of field emission emission site;
  • Fig. 4 is the test data graph of field emission stability under different pressures
  • Figure 6 is a side view of the field emission of the preferred embodiment of the present invention, wherein Figure 6 (a) field emission E-J curve, (b) F-N curve;
  • FIG. 7 is a data diagram of field emission stability test under different pressures according to the preferred embodiment of the present invention.
  • a layer of platinum metal was first plated on the surface of the nickel substrate by magnetron sputtering (vacuum degree: 9 Pa, sputtering current: 30 mA, sputtering time: 600 s), as shown in Figure 1 (a).
  • the nickel substrate was then point ablated with a pulsed laser at negative defocus (wavelength: 1064 nm, frequency: 3 Hz, output current: 50-150 A, negative defocus distance: 0.00-0.50 mm). Pulsed laser ablation can melt the internal particles of nickel metal and eject them to the surface to form spherical shells, as shown in Figures 1b and 1c.
  • the laser focus is inside the material, which melts the internal nickel metal, flows to the surface of the material under the driving action of nickel metal vapor, and forms a spherical shell after cooling, and protects the nickel from oxidation by high-purity nitrogen.
  • the morphology of the microfocus electron source was characterized by scanning electron microscopy.
  • the field emission test adopts a two-level structure, the anode is a metal molybdenum with a small thermal expansion coefficient, and the distance between the two poles is 300 ⁇ m.
  • a Keithley 248 power supply was used to supply voltage to the two electrodes.
  • high-purity nitrogen gas with a purity of 99.999 % was injected into the vacuum system through the inflation valve to change the pressure in the system, and the voltage was adjusted under different pressures to make the initial emission current 600 mA (443 mA/cm 2 ), Then keep the voltage unchanged and record the current data of continuous emission for 6 h.
  • the multi-layer graphene oxide of Suzhou Tanfeng Technology was selected and prepared into 0.01 g/l, 0.05 g/l, 0.10 g/l, 0.15 g/l, 0.20 g/l graphene suspension.
  • Graphene was plated on the top of CNTs by DC electrophoresis (electrophoresis time was 1 min), and then annealed at 750 °C under rough vacuum. Its morphology was characterized by scanning electron microscopy. Finally, I-V test and stability test were performed on the samples coated with different concentrations of graphene to measure the stability under different pressures.
  • the covered area of the multi-walled carbon nanotubes prepared by this method is a spherical shell surface with a diameter of about 350 ⁇ m, as shown in Fig. 2(a).
  • the surface area of the covered area of the multi-walled carbon nanotubes was calculated using the measurement data of the cross-sectional view in Figure 2(b), and the average surface area was 0.135 mm 2 by averaging multiple sets of data.
  • Nickel metal can form a dense oxide film at room temperature, which hinders the contact between nickel and carbon source gas, which is not conducive to the growth of carbon nanotubes. Platinum plating can further inhibit the growth of carbon nanotubes on the surface.
  • the unoxidized nickel particles on the surface of the spherical shell can catalyze the growth of carbon nanotubes, forming an electron point source cathode with a diameter of about 350 ⁇ m.
  • the diameter of CNT is directly related to the type of catalyst and particle diameter.
  • the nickel particles at the edge of the spherical shell become smaller and aggregated after melting, and the diameter of the catalytically grown carbon nanotubes is smaller ( ⁇ 10 nm) and form bundles, called bundled carbon nanotube regions.
  • the top of the spherical shell is formed by the solidification and agglomeration of completely melted nickel, so the carbon nanotubes catalyzed and grown in this area are evenly distributed, which is called the carbon nanotube thin film area.
  • the ITO imaging of the emission site under different emission currents is shown in Figure 3c.
  • the emission is enhanced from left to right, and all are relatively uniform circular images, indicating that the emission area of the cathode is concentrated in the micro-scale spherical shell part.
  • the field emission IV test data are shown in Fig. 3a, the threshold electric field of the first test was less than 1 V/ ⁇ m, and the threshold electric field of the second and third IV tests increased to 3 V/ ⁇ m compared with the first test.
  • the field emission current density reaches 400 mA/cm 2 .
  • the possible reason for the low field strength of the first emission is that the effective work function of CNTs is reduced due to gas adsorption, which increases the field emission current.
  • Figure 4 shows the stability of the continuous emission of the electron source for 6 h under the pressures of 3.7 ⁇ 10 -7 Pa, 2.9 ⁇ 10 -6 Pa and 4.3 ⁇ 10 -5 Pa and the initial current of 600 mA (443 mA/cm 2 ).
  • the current showed an upward trend after the second hour, and the current increased by 5.8% at the sixth hour.
  • the current increased by 7.5% in the first 2 h, and then decreased slowly to the initial current of 443 mA/cm 2 in 2 h-6 h.
  • the current continuously decayed by 68.9% for 6 h.
  • Figure 6 shows the I-V characteristics of CNTs after plating with 0.10 g/l graphene and annealing at 750 °C under high temperature vacuum.
  • the emission turn-on electric field is ⁇ 1 V/ ⁇ m; the threshold electric field is 2.3 V/ ⁇ m for the first time and 3.5 V/ ⁇ m for the second and third times.
  • the first and last two curves are closer compared to when no graphene is plated. It shows that the deposition of graphene reduces the influence of gas adsorption on the emission, which is beneficial to improve the emission stability.
  • Figure 7 shows the emission stability of the samples coated with 0.10 g/l graphene and annealed at 750 °C under different pressures and 600 ⁇ A emission (443 mA/cm 2 ).
  • the graphene-coated samples had a current decay of 14% after 6 h of testing, which was much lower than the 68.9% before untreated.
  • this CNT field emission cathode exhibits better emission stability at high current density at a pressure of 10 -5 Pa.
  • the emission stability of other CNT cathodes is generally carried out at a low pressure of ⁇ 10 -6 Pa, and the test at a pressure of 10 -5 Pa shows a large current decay.
  • Graphene has high electrical conductivity, thermal stability and excellent mechanical strength.
  • the larger bulk graphene covers the top of the CNT, which weakens the field-enhancing effect and leads to a higher turn-on electric field.
  • the graphene on the top of the CNT can prevent the direct bombardment of the CNT by charged particles during high electric field emission, resulting in the degradation of the cathode performance. This may be one of the main reasons why coating graphene can enhance the stability of CNTs under high pressure.
  • the addition of graphene increases the thermal conductivity in the radial direction of the CNT, which disperses the heat conduction at the emission site in time to protect the emission site.
  • vacuum high-temperature annealing at 750 °C can promote the defect repair of CNTs and improve the crystallinity.
  • the combination of graphene coating on CNT films and vacuum high temperature annealing at 750 °C can effectively improve the stability of the microfocus electron source under high pressure.
  • the present invention uses pulsed laser to ablate the nickel substrate to melt the internal nickel particles and spray them out to form micro-scale spherical shells, and uses the CVD method to directly grow MWNTs to obtain micro-focus CNT field emission cathodes.
  • the microfocus electron source has the advantages of low turn-on electric field ( ⁇ 1 V/ ⁇ m) and high current density ( ⁇ 1 A/cm 2 ).
  • ⁇ 1 V/ ⁇ m low turn-on electric field
  • ⁇ 1 A/cm 2 high current density
  • graphene was coated on the top of CNT by DC electrophoresis and annealed at 750 °C in high temperature vacuum, the high-voltage strong emission performance of the micro-focus cathode was improved, and it had good working stability at 10 -5 Pa.
  • the anti-ion bombardment performance of graphene and Excellent thermal conductivity plays an important role.
  • the invention provides an effective means for the development of microscale (focus) field emission cathodes.

Abstract

A microfocus field emission electron source based on a carbon nanotube, and a preparation method therefor. The method comprises the following steps: (1) applying a metal platinum layer onto the surface of a nickel substrate; (2) under the protection of a protective gas, performing, by using a pulse laser and in a negative defocusing mode, point ablation on the surface of the nickel substrate that is plated with metal platinum, wherein the focus of the laser is inside the nickel substrate during negative defocusing ablation, so that internal nickel metal is melted, flows to the surface of the nickel substrate under a pushing force of nickel metal vapor, and forms a spherical shell after being cooled; and (3) directly growing, by using a chemical vapor phase deposition method, a carbon nanotube cathode film on the spherical shell, which is formed by means of laser ablation, of the nickel substrate. The microfocus electron source has the advantages of a low turn-on electric field (<1 V/μm), a high current density (~ 1 A/cm2), good high-pressure emission operation stability, etc.

Description

一种基于碳纳米管的微焦点场发射电子源及其制备方法A kind of micro-focus field emission electron source based on carbon nanotubes and preparation method thereof 技术领域technical field
本发明涉及一种场发射电子源，具体是指一种基于碳纳米管的微焦点场发射电子源及其制备方法。The invention relates to a field emission electron source, in particular to a microfocus field emission electron source based on carbon nanotubes and a preparation method thereof.
背景技术Background technique
碳纳米管（CNT）具有优异的物理、化学、结构等性质，是较为理想的场发射阴极材料，与传统金属尖端(通常是钨或钼)发射体相比，其具有几乎接近理论极限的尖端表面积，它的尖端尺寸只有几纳米至几十纳米，具有低场发射电压(可小于100伏)，可传输极大的电流密度，并且电流稳定，使用寿命长，因而 非常适合作为一种极佳的点电子源，应用在扫描电子显微镜(Scanning Electron Microscope)、透射电子显微镜(Transmission Electron Microscope)、微焦点X射线成像仪等设备的电子发射部件中。Carbon nanotubes (CNTs) have excellent physical, chemical, structural and other properties, and are ideal field emission cathode materials. Compared with traditional metal tip (usually tungsten or molybdenum) emitters, they have tips that are almost close to the theoretical limit. Surface area, its tip size is only a few nanometers to tens of nanometers, it has a low field emission voltage (can be less than 100 volts), it can transmit extremely large current densities, and the current is stable and has a long service life, so it is very suitable as an excellent The point electron source is used in the electron emission components of scanning electron microscope (Scanning Electron Microscope), transmission electron microscope (Transmission Electron Microscope), microfocus X-ray imager and other equipment.
通过检索，现有技术有以下文献有关碳纳米管场发射电子的研究：Through the search, the prior art has the following documents related to the research on carbon nanotube field emission electrons:
（1）      Thong等制备了CNT阵列阴极，参考文献THONG J, OON C H, ENG W K, et al. High-current field emission from a vertically aligned carbon nanotube field emitter array [J]. Applied Physics Letters, 2001, 79(17): 2811-3，该阴极在压强小可以于10 -6 Pa的真空度下20 h内电流（I=0.46 mA, J=128 mA/cm 2）仅衰减了1.5 %。但是短时间波动幅度约为61.5%，在高压强下场发射性能更差。 (1) Thong et al. prepared a CNT array cathode, reference THONG J, OON CH, ENG WK, et al. High-current field emission from a vertically aligned carbon nanotube field emitter array [J]. Applied Physics Letters, 2001, 79 (17): 2811-3, the current (I=0.46 mA, J=128 mA/cm 2 ) of the cathode attenuates only 1.5% within 20 h under the vacuum of 10 -6 Pa under the low pressure. However, the short-term fluctuation range is about 61.5%, and the field emission performance is worse under high pressure.
（2） Semet等通过等离子体增强化学气相沉积法（PECVD）制备垂直排列阵列的单根CNT，其在10 -6-10 -7 Pa的压强下场发射电流波动小于10 %。Di等在碳纳米纤维上制备CNT发射体，参见文献SEMET V, BINH V T, VINCENT P, et al. Field electron emission from individual carbon nanotubes of a vertically aligned array [J]. Applied Physics Letters, 2002, 81(2): 343-5；YUNSONG, DI, MEI, et al. Large and stable emission current from synthesized carbon nanotube/fiber network [J]. Journal of Applied Physics, 2014, 115(6): 1-5.该阴极在10 -6 Pa下能达30 mA（J=333 mA/cm 2）发射电流，而在5.05-15.04 mA（J=56-167 mA/cm 2）区间电流波动小于3 %。 (2) Semet et al. prepared vertically aligned single CNTs by plasma-enhanced chemical vapor deposition (PECVD), and the field emission current fluctuation was less than 10% under the pressure of 10 -6 -10 -7 Pa. Di et al. prepared CNT emitters on carbon nanofibers, see literature SEMET V, BINH VT, VINCENT P, et al. Field electron emission from individual carbon nanotubes of a vertically aligned array [J]. Applied Physics Letters, 2002, 81 ( 2): 343-5; YUNSONG, DI, MEI, et al. Large and stable emission current from synthesized carbon nanotube/fiber network [J]. Journal of Applied Physics, 2014, 115(6): 1-5. The cathode The emission current can reach 30 mA (J=333 mA/cm 2 ) at 10 -6 Pa, while the current fluctuation is less than 3% in the interval of 5.05-15.04 mA (J=56-167 mA/cm 2 ).
（3） Kim等设计了一种基于多壁CNT纺织纱线的微焦点X射线管阴极，参见文献Kim H S, Castro E J D, Lee C H. Design of a carbon-nanotube yarn field emitter for micro-focus X-ray generation [J]. Journal of the Korean Physical Society, 2016, 69(3): 297-303.该阴极具有较低的开启电场和较高的场增强因子，制成的X射线管加入反馈电路稳定电流后寿命延长。(3) Kim et al. designed a microfocus X-ray tube cathode based on multi-walled CNT textile yarns, see Kim H S, Castro E J D, Lee C H. Design of a carbon-nanotube yarn field emitter for micro-focus X-ray generation [J]. Journal of the Korean Physical Society, 2016, 69(3): 297-303. The cathode has a lower turn-on electric field and a higher field enhancement factor, and the X-ray tube made by adding a feedback circuit to stabilize the current has a longer life.
（4） 同时，石墨烯与CNT的复合结构也在改善发射性能上展现了一定优势。虽然各类CNT冷阴极在小于10 -6 Pa的真空度下具有良好的发射稳定性，但是高压强（P>10 -6 Pa）、大电流下稳定发射始终是一个挑战。 (4) At the same time, the composite structure of graphene and CNT also showed certain advantages in improving the emission performance. Although all kinds of CNT cold cathodes have good emission stability under the vacuum degree of less than 10 -6 Pa, stable emission under high pressure (P>10 -6 Pa) and high current is always a challenge.
近些年来，由于半导体器件制备技术的发展，出现微焦点X射线源，微小焦点能防止x射线图像的模糊，并提供明锐的放大图像，从而被应用到X射线无损检测等领域。微焦点射线源的焦点尺寸更小，可以达到微米级别，在高几何放大倍数下，将图像几何不清晰度降至最低，以实现高达微米级的分辨率。然而比起碳纳米管的尖端尺寸而言，微焦点X射线源的焦点尺寸仍然远远不够小。In recent years, due to the development of semiconductor device fabrication technology, micro-focus X-ray sources have appeared. The micro-focus can prevent the blurring of X-ray images and provide sharp magnified images, which are used in X-ray non-destructive testing and other fields. Microfocus ray sources have smaller focal sizes down to the micron level, minimizing image geometric unsharpness at high geometric magnifications to achieve resolutions up to micron level. However, compared to the tip size of carbon nanotubes, the focal point size of microfocus X-ray sources is still far from being small enough.
技术问题technical problem
本发明的目的是为了克服现有技术存在的缺点和不足，而提供一种基于碳纳米管的微焦点场发射电子源及其制备方法，该微焦点场发射电子源具有良好强流发射和高压强稳定的特性。The purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art, and to provide a micro-focus field emission electron source based on carbon nanotubes and a preparation method thereof, the micro-focus field emission electron source has good strong current emission and high voltage Strong and stable characteristics.
技术解决方案technical solutions
为实现上述目的，本发明的第一个目的是提供一种基于碳纳米管的微焦点场发射电子源的制备方法。In order to achieve the above object, the first object of the present invention is to provide a preparation method of a micro-focus field emission electron source based on carbon nanotubes.
为实现上述目的，本发明的技术方案是一种基于碳纳米管的微焦点场发射电子源的制备方法，其阴极包括以下步骤：In order to achieve the above object, the technical solution of the present invention is a preparation method of a carbon nanotube-based micro-focus field emission electron source, the cathode of which comprises the following steps:
（1）在镍基片表面镀上金属铂层；(1) A metal platinum layer is plated on the surface of the nickel substrate;
（2）在保护气体保护下，利用脉冲激光以负离焦对镍基片镀有金属铂的表面进行点烧蚀，负离焦烧蚀时激光焦点在镍基片内部，使内部镍金属融化，在镍金属蒸汽的推动作用下流向镍基片表面冷却后形成球壳；(2) Under the protection of protective gas, a pulsed laser is used to ablate the surface of the nickel substrate coated with metal platinum with negative defocusing. During the ablation with negative defocusing, the laser focus is inside the nickel substrate, so that the internal nickel metal is melted. , which flows to the surface of the nickel substrate under the driving action of the nickel metal vapor and forms a spherical shell after cooling;
（3）利用化学气相沉积法在镍基底的激光烧蚀形成的球壳上直接生长碳纳米管阴极薄膜。(3) The carbon nanotube cathode film was directly grown on the spherical shell formed by laser ablation of the nickel substrate by chemical vapor deposition.
进一步设置是所述的步骤（3）之后，还设置有步骤（4）：通过电泳法在碳纳米管阴极薄膜上沉积石墨烯，并进行真空高温退火。It is further provided that after the step (3), there is also a step (4): depositing graphene on the carbon nanotube cathode film by electrophoresis, and performing vacuum high temperature annealing.
进一步设置是所述的碳纳米管阴极薄膜为多壁碳纳米管阴极薄膜。It is further provided that the carbon nanotube cathode film is a multi-wall carbon nanotube cathode film.
进一步设置是脉冲激光以负离焦烧蚀的参数为：波长1064 nm、频率3 Hz、输出电流50-150 A以及负离焦距离在0.00-0.50 mm范围内，这个对球壳的直径和形貌影响较大。Further settings are pulsed laser ablation with negative defocus parameters: wavelength 1064 nm, frequency 3 Hz, output current 50-150 A, and negative defocus distance at 0.00-0.50 In the mm range, this has a greater impact on the diameter and shape of the spherical shell.
本发明的第二个目的是提供一种如所述方法所制备的基于碳纳米管的微焦点场发射电子源。The second object of the present invention is to provide a carbon nanotube-based microfocus field emission electron source prepared by the method.
有益效果beneficial effect
本发明的创新原理和有益效果是：The innovative principle and beneficial effects of the present invention are:
通过在镍基片表面镀上铂层，并利用脉冲激光以负离焦方式进行点烧蚀，从而使得内部的镍金属流向表面形成凸起于表面的点状的微小尺寸的球壳，而该球壳的材料为镍，具有催化效应，因为利用化学气相沉积可以在该镍材料的球壳表面形成碳纳米管阴极薄膜，而球壳边缘的铂层由于不具有催化效应而没有生长碳纳米管薄膜，从而形成尺寸可控的碳纳米管，利用该碳纳米管的场发射效应，所形成电子源具有尺寸小的微焦点技术效果。By plating a platinum layer on the surface of the nickel substrate, and performing point ablation with a pulsed laser in a negative defocusing manner, the inner nickel metal flows to the surface to form a spherical shell with tiny dots protruding from the surface. The material of the spherical shell is nickel, which has a catalytic effect, because chemical vapor deposition can form a carbon nanotube cathode film on the surface of the spherical shell of the nickel material, and the platinum layer on the edge of the spherical shell does not grow carbon nanotubes because it has no catalytic effect. A thin film is formed, thereby forming carbon nanotubes with a controllable size, and by utilizing the field emission effect of the carbon nanotubes, the formed electron source has the effect of micro-focus technology with small size.
而通过下面的实施例的实验数据，本申请的技术方案该微焦点电子源具有开启电场低（<1 V/μm）、电流密度高（~1 A/cm 2）等优点。利用直流电泳法在CNT顶端镀石墨烯并经高温真空退火后，微焦点阴极的高压强发射性能得到改善，在10 -5 Pa具有较好的工作稳定性，石墨烯的抗离子轰击性能和优良的导热性能等起到了重要的作用。 According to the experimental data of the following examples, the micro-focus electron source of the technical solution of the present application has the advantages of low turn-on electric field (<1 V/μm) and high current density (~1 A/cm 2 ). After graphene was plated on the top of CNT by DC electrophoresis and annealed in high temperature vacuum, the high-voltage strong emission performance of the micro-focus cathode was improved, and it had good working stability at 10 -5 Pa. The anti-ion bombardment performance of graphene and excellent Thermal conductivity plays an important role.
附图说明Description of drawings
为了更清楚地说明本发明实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本发明的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动性的前提下，根据这些附图获得其他的附图仍属于本发明的范畴。In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention, and for those of ordinary skill in the art, obtaining other drawings according to these drawings still belongs to the scope of the present invention without any creative effort.
图1 本发明的制备步骤分解示意图，其中图1（a）磁控溅射镀铂（b）激光烧蚀熔融状态（c）激光烧蚀凝固状态（d）通过CVD生长后CNT薄膜的覆盖区域；Figure 1. Decomposed schematic diagram of the preparation steps of the present invention, in which Figure 1 (a) magnetron sputtering platinum (b) laser ablation molten state (c) laser ablation solidified state (d) covered area of CNT thin film after growth by CVD ;
图 2 微焦点电子源阴极SEM图；Figure 2 SEM image of the cathode of the microfocus electron source;
图3 场发射测试图，其中图 3（a）场发射E-J曲线，（b）F-N曲线，（d）场发射发射位点成像图；Fig. 3 Field emission test diagram, in which Fig. 3(a) E-J curve of field emission, (b) F-N curve, (d) imaging diagram of field emission emission site;
图4 为在不同压强下场发射稳定性测试数据图；Fig. 4 is the test data graph of field emission stability under different pressures;
图5 镀石墨烯后微焦点场发射电子源的SEM图；Fig. 5 SEM image of microfocus field emission electron source after graphene coating;
图6 本发明优选实施例的场发射侧视图，其中图6（a）场发射E-J曲线，（b）F-N曲线；Figure 6 is a side view of the field emission of the preferred embodiment of the present invention, wherein Figure 6 (a) field emission E-J curve, (b) F-N curve;
图7 本发明优选实施例的不同压强下场发射稳定性测试数据图。FIG. 7 is a data diagram of field emission stability test under different pressures according to the preferred embodiment of the present invention.
本发明的最佳实施方式BEST MODE FOR CARRYING OUT THE INVENTION
为使本发明的目的、技术方案和优点更加清楚，下面将结合附图对本发明作进一步地详细描述。In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.
制备实施例：Preparation Examples:
在碳纳米管阴极制备中，首先通过磁控溅射在镍基片表面镀上一层金属铂（真空度：9 Pa、溅射电流：30 mA、溅射时间：600 s），如图1（a）。然后利用脉冲激光以负离焦对镍基片进行点烧蚀(波长：1064 nm、频率：3 Hz、输出电流：50-150 A、负离焦距离：0.00-0.50 mm)。脉冲激光负离焦烧蚀可使镍金属内部颗粒融化喷发至表面形成球壳，如图1b和 1c所示。负离焦烧蚀时激光焦点在材料内部，使内部镍金属融化，在镍金属蒸汽的推动作用下流向材料表面冷却后形成球壳，并通过高纯氮气保护镍不被氧化。最后以C 2H 2为碳源气体、Ar为保护气体通过CVD法（C 2H 2：Ar=1：4、温度：750 ℃、压强：8 Torr、时间：10 min）在激光烧蚀的位置直接生长多壁碳纳米管电子源阴极，如图1d。利用扫描电子显微镜对微焦点电子源进行了形貌表征。 In the preparation of carbon nanotube cathodes, a layer of platinum metal was first plated on the surface of the nickel substrate by magnetron sputtering (vacuum degree: 9 Pa, sputtering current: 30 mA, sputtering time: 600 s), as shown in Figure 1 (a). The nickel substrate was then point ablated with a pulsed laser at negative defocus (wavelength: 1064 nm, frequency: 3 Hz, output current: 50-150 A, negative defocus distance: 0.00-0.50 mm). Pulsed laser ablation can melt the internal particles of nickel metal and eject them to the surface to form spherical shells, as shown in Figures 1b and 1c. During negative decoking ablation, the laser focus is inside the material, which melts the internal nickel metal, flows to the surface of the material under the driving action of nickel metal vapor, and forms a spherical shell after cooling, and protects the nickel from oxidation by high-purity nitrogen. Finally, C 2 H 2 was used as carbon source gas and Ar as protective gas by CVD method (C 2 H 2 : Ar=1:4, temperature: 750 ℃, pressure: 8 Torr, time: 10 min) in laser ablation site to directly grow multi-walled carbon nanotubes at the electron source cathode, as shown in Figure 1d. The morphology of the microfocus electron source was characterized by scanning electron microscopy.
该实施例仅仅是制备的参考实施例，本领域技术人员在不经创造性思考利用本领域的公知技术应用上述制备方法所获得的技术方案，也应属于本申请相同的构思，应落入本申请的保护范围。This embodiment is only a reference example for preparation, and the technical solutions obtained by those skilled in the art by applying the above-mentioned preparation method without creative thinking by using the known technology in the art should also belong to the same concept of the present application and should fall into the present application. scope of protection.
场发射性能测试实验例Field Emission Performance Test Example
场发射性能在分子泵高真空***中测试。首先通过阳极涂有荧光粉ITO的二级式结构对上述实施例所制备的微焦点电子源的阴极发射位点进行表征。两级间距为300 μm，阳极紧贴陶瓷支架以获得最佳散热效果。在10 -7 Pa的真空度下，用200 mA/cm 2的电流发射10 min对碳纳米管和阳极ITO进行除气。然后利用工业相机记录不同发射电流下ITO的发光信息。 Field emission performance was tested in a molecular pump high vacuum system. First, the cathode emission sites of the microfocus electron sources prepared in the above examples were characterized by the secondary structure of the anode coated with phosphor ITO. The distance between the two stages is 300 μm, and the anode is close to the ceramic support for best heat dissipation. The carbon nanotubes and anode ITO were degassed with a current emission of 200 mA/cm 2 for 10 min under a vacuum of 10 -7 Pa. Then, an industrial camera was used to record the luminescence information of ITO under different emission currents.
场发射测试采用二级式结构，阳极为热膨胀系数小的金属钼，两极间距为300 μm。用350 ℃对真空腔体烘烤10 h冷却至室温后，利用Keithley 248电源为两极提供电压。稳定性测试中，通过充气阀向真空***中冲入纯度为99.999 %的高纯氮气改变***中的压强，分别在不同压强下调节电压使初始发射电流为600 mA (443 mA/cm 2)，然后保持电压不变记录连续发射6 h的电流数据。 The field emission test adopts a two-level structure, the anode is a metal molybdenum with a small thermal expansion coefficient, and the distance between the two poles is 300 μm. After the vacuum chamber was baked at 350 °C for 10 h and cooled to room temperature, a Keithley 248 power supply was used to supply voltage to the two electrodes. In the stability test, high-purity nitrogen gas with a purity of 99.999 % was injected into the vacuum system through the inflation valve to change the pressure in the system, and the voltage was adjusted under different pressures to make the initial emission current 600 mA (443 mA/cm 2 ), Then keep the voltage unchanged and record the current data of continuous emission for 6 h.
在沉积石墨烯改善稳定性实验中，选用苏州碳丰科技的多层氧化石墨烯，分别配制成0.01 g/l、0.05 g/l、0.10 g/l、0.15 g/l、0.20 g/l的石墨烯悬浊液。利用直流电泳法将石墨烯镀在CNT顶端（电泳时间为1 min），然后在粗真空下进行750 ℃高温退火。利用扫面电子显微镜对其形貌表征。最后对镀有不同浓度石墨烯的样品进行I-V测试和稳定性测试，测量不同压力下的稳定性。In the experiment of improving stability by depositing graphene, the multi-layer graphene oxide of Suzhou Tanfeng Technology was selected and prepared into 0.01 g/l, 0.05 g/l, 0.10 g/l, 0.15 g/l, 0.20 g/l graphene suspension. Graphene was plated on the top of CNTs by DC electrophoresis (electrophoresis time was 1 min), and then annealed at 750 °C under rough vacuum. Its morphology was characterized by scanning electron microscopy. Finally, I-V test and stability test were performed on the samples coated with different concentrations of graphene to measure the stability under different pressures.
测试结果说明：Test result description:
1、形貌表征分析：1. Morphological characterization analysis:
该方法制备的多壁碳纳米管覆盖区域为直径约350 μm的球壳表面，如图2（a）所示。利用图2（b）截面图的测量数据计算出多壁碳纳米管覆盖区域表面积，将多组数据求平均值得出平均表面积为0.135 mm 2。多壁碳纳米管覆盖区域主要有两类形貌：直径约10 nm的多壁碳纳米管组成的管束和直径约为30 nm的多壁碳纳米管组成的薄膜区域，如图2（c）所示。 The covered area of the multi-walled carbon nanotubes prepared by this method is a spherical shell surface with a diameter of about 350 μm, as shown in Fig. 2(a). The surface area of the covered area of the multi-walled carbon nanotubes was calculated using the measurement data of the cross-sectional view in Figure 2(b), and the average surface area was 0.135 mm 2 by averaging multiple sets of data. There are two main types of morphologies in the covered area of MWCNTs: the tube bundle composed of MWCNTs with a diameter of about 10 nm and the thin film region composed of MWCNTs with a diameter of about 30 nm, as shown in Figure 2(c) shown.
镍金属在常温下可生成致密的氧化膜，阻碍镍与碳源气体接触不利于碳纳米管生长，镀铂可进一步抑制表面碳纳米管的生长。球壳表面镍颗粒未氧化可催化生长碳纳米管，形成直径约为350 μm的电子点源阴极。而CNT的直径与催化剂的种类和颗粒直径直接相关，球壳边缘的镍颗粒经过融化后颗粒直径变小而聚集在一起，催化生长的碳纳米管直径较小（~10 nm）并形成束状，称为束状碳纳米管区域。球壳顶部是由完全融化的镍凝固结块而成，因此该区域催化生长的碳纳米管分布均匀，称为碳纳米管薄膜区域。Nickel metal can form a dense oxide film at room temperature, which hinders the contact between nickel and carbon source gas, which is not conducive to the growth of carbon nanotubes. Platinum plating can further inhibit the growth of carbon nanotubes on the surface. The unoxidized nickel particles on the surface of the spherical shell can catalyze the growth of carbon nanotubes, forming an electron point source cathode with a diameter of about 350 μm. The diameter of CNT is directly related to the type of catalyst and particle diameter. The nickel particles at the edge of the spherical shell become smaller and aggregated after melting, and the diameter of the catalytically grown carbon nanotubes is smaller (~10 nm) and form bundles, called bundled carbon nanotube regions. The top of the spherical shell is formed by the solidification and agglomeration of completely melted nickel, so the carbon nanotubes catalyzed and grown in this area are evenly distributed, which is called the carbon nanotube thin film area.
2、场发射测试分析2. Field emission test analysis
不同发射电流下的发射位点ITO成像如图3c所示，从左至右发射增强，均为较均匀的圆形成像，说明该阴极的发射区域集中在微尺度球壳部分。场发射I-V测试数据如图3a所示，第一次测试阈值电场小于1 V/μm，第二次和第三次I-V测试与第一次相比阈值电场上升至3 V/μm。场发射电流密度达到400 mA/cm 2。第一次发射场强低可能的原因是气体吸附引起CNT有效功函数降低，使场发射电流增强。第一次I-V测试后焦耳加热使表面气体解吸，发射趋于本征发射。同时，F-N曲线可见第一次测量的F-N曲线斜率的绝对值比第二和第三次测量的F-N曲线斜率绝对值小，也说明气体吸附下功函数降低。 The ITO imaging of the emission site under different emission currents is shown in Figure 3c. The emission is enhanced from left to right, and all are relatively uniform circular images, indicating that the emission area of the cathode is concentrated in the micro-scale spherical shell part. The field emission IV test data are shown in Fig. 3a, the threshold electric field of the first test was less than 1 V/μm, and the threshold electric field of the second and third IV tests increased to 3 V/μm compared with the first test. The field emission current density reaches 400 mA/cm 2 . The possible reason for the low field strength of the first emission is that the effective work function of CNTs is reduced due to gas adsorption, which increases the field emission current. Joule heating after the first IV test desorbs the surface gas and the emission tends to be intrinsic. At the same time, it can be seen from the FN curve that the absolute value of the slope of the FN curve measured for the first time is smaller than the absolute value of the slope of the FN curve measured for the second and third times, which also indicates that the work function decreases under gas adsorption.
SEM表征和发射ITO成像均显示，除球壳以外的区域几乎没有碳纳米管生长。铂膜和基底表面氧化镍膜有效阻止CNT的生长，球壳部分生长的CNT场发射出电子，成功制备出平面型电子点源阴极。Both SEM characterization and emission ITO imaging show that there is almost no carbon nanotube growth in the region other than the spherical shell. The platinum film and the nickel oxide film on the surface of the substrate can effectively prevent the growth of CNTs. The CNTs growing in the spherical shell emit electrons in the field, and a planar electron point source cathode is successfully prepared.
图4展示了在3.7×10 -7 Pa、2.9×10 -6 Pa和4.3×10 -5 Pa压强、初始电流600 mA（443 mA/cm 2）下该电子源连续发射6 h的稳定性。在3.7×10 -7 Pa压强下，电流在第2h后呈上涨趋势，在第6 h时电流上涨了5.8 %。在2.9×10 -6 Pa压强下，电流在前2 h内上升了7.5 %，而在2 h-6 h内电流又缓慢下降至初始电流443 mA/cm 2。而在4.3×10 -5 Pa下持续发射6 h电流持续衰减了68.9 %。 Figure 4 shows the stability of the continuous emission of the electron source for 6 h under the pressures of 3.7×10 -7 Pa, 2.9×10 -6 Pa and 4.3×10 -5 Pa and the initial current of 600 mA (443 mA/cm 2 ). Under the pressure of 3.7×10 -7 Pa, the current showed an upward trend after the second hour, and the current increased by 5.8% at the sixth hour. Under the pressure of 2.9×10 -6 Pa, the current increased by 7.5% in the first 2 h, and then decreased slowly to the initial current of 443 mA/cm 2 in 2 h-6 h. However, at 4.3×10 -5 Pa, the current continuously decayed by 68.9% for 6 h.
优选实施例Preferred Embodiment
在上述实施例基础上，为提高电子源在10 -5 Pa下的稳定性，我们用电泳法在多壁碳纳米管上沉积石墨烯，并进行750 ℃真空高温退火，SEM形貌如图5所示。经过镀石墨烯和750 ℃真空退火处理后，CNT顶端附着了大块石墨烯，并且管壁上也镀有小颗粒状的石墨烯。部分CNT管束被石墨烯包覆。 On the basis of the above example, in order to improve the stability of the electron source at 10 -5 Pa, we used electrophoresis to deposit graphene on multi-walled carbon nanotubes, and annealed at 750 ℃ in vacuum at high temperature. The SEM morphology is shown in Figure 5 shown. After graphene plating and vacuum annealing at 750 °C, large pieces of graphene were attached to the top of the CNT, and small particles of graphene were also plated on the tube wall. Part of the CNT bundles are coated with graphene.
我们对镀不同浓度石墨烯的样品进行I-V测试和稳定性测试，结果发现镀0.10 g/l石墨烯的稳定性显著增强。图6为CNT经过镀0.10 g/l石墨烯和750 ℃高温真空退火后的I-V特性。发射开启电场< 1 V/μm；阈值电场第一次为2.3 V/μm，第二、三次为3.5 V/μm。与未镀石墨烯时相比，第一次和后两次曲线更接近。说明沉积石墨烯减小了气体吸附对发射的影响，有利于提高发射稳定性。We performed I-V tests and stability tests on samples plated with different concentrations of graphene, and found that the stability of 0.10 g/l graphene plating was significantly enhanced. Figure 6 shows the I-V characteristics of CNTs after plating with 0.10 g/l graphene and annealing at 750 °C under high temperature vacuum. The emission turn-on electric field is < 1 V/μm; the threshold electric field is 2.3 V/μm for the first time and 3.5 V/μm for the second and third times. The first and last two curves are closer compared to when no graphene is plated. It shows that the deposition of graphene reduces the influence of gas adsorption on the emission, which is beneficial to improve the emission stability.
镀0.10 g/l石墨烯和750 ℃退火样品在不同压强、600 μA发射（443 mA/cm 2）下的发射稳定性如图7所示。在10 -5 Pa，镀石墨烯样品在6 h测试后电流衰减14 %，远低于未处理之前68.9 %。与其他CNT阴极相比，该CNT场发射阴极在10 -5 Pa压强下展示了较好的大电流密度发射稳定性。而其它CNT阴极的发射稳定性一般在<10 -6 Pa的低压强中进行，在10 -5 Pa压强下的测试则出现较大幅度的电流衰减。 Figure 7 shows the emission stability of the samples coated with 0.10 g/l graphene and annealed at 750 ℃ under different pressures and 600 μA emission (443 mA/cm 2 ). At 10-5 Pa, the graphene-coated samples had a current decay of 14% after 6 h of testing, which was much lower than the 68.9% before untreated. Compared with other CNT cathodes, this CNT field emission cathode exhibits better emission stability at high current density at a pressure of 10 -5 Pa. The emission stability of other CNT cathodes is generally carried out at a low pressure of <10 -6 Pa, and the test at a pressure of 10 -5 Pa shows a large current decay.
石墨烯具有高的导电性、热稳定性和优异的机械强度。较大的块状石墨烯覆盖在CNT顶端，使场增强效应减弱从而导致开启电场有所升高。但CNT顶端的石墨烯可防止高电场发射时带电粒子直接轰击CNT导致阴极性能衰减。这可能是镀石墨烯能增强CNT在高压强下稳定性的主要原因之一。另一方面，石墨烯的加入增加了CNT径向的导热性，及时将发射位点的热量传导分散而保护发射位点。同时，750 ℃真空高温退火可以促进CNT的缺陷修复、改善晶体性。综上所述，将CNT薄膜镀石墨烯和750 ℃真空高温退火结合，能有效改善该微焦点电子源在高压强下的稳定性。Graphene has high electrical conductivity, thermal stability and excellent mechanical strength. The larger bulk graphene covers the top of the CNT, which weakens the field-enhancing effect and leads to a higher turn-on electric field. However, the graphene on the top of the CNT can prevent the direct bombardment of the CNT by charged particles during high electric field emission, resulting in the degradation of the cathode performance. This may be one of the main reasons why coating graphene can enhance the stability of CNTs under high pressure. On the other hand, the addition of graphene increases the thermal conductivity in the radial direction of the CNT, which disperses the heat conduction at the emission site in time to protect the emission site. At the same time, vacuum high-temperature annealing at 750 °C can promote the defect repair of CNTs and improve the crystallinity. In summary, the combination of graphene coating on CNT films and vacuum high temperature annealing at 750 °C can effectively improve the stability of the microfocus electron source under high pressure.
综上所述，本发明采用脉冲激光烧蚀镍基片使内部镍颗粒融化后喷出形成微尺度球壳，利用CVD法直接生长MWNT，获得微焦点CNT场发射阴极。该微焦点电子源具有开启电场低（<1 V/μm）、电流密度高（~1 A/cm 2）等优点。利用直流电泳法在CNT顶端镀石墨烯并经750 ℃高温真空退火后，微焦点阴极的高压强发射性能得到改善，在10 -5 Pa具有较好的工作稳定性，石墨烯的抗离子轰击性能和优良的导热性能等起到了重要的作用。本发明为微尺度（焦点）场发射阴极的研制提供了一种有效的手段。 To sum up, the present invention uses pulsed laser to ablate the nickel substrate to melt the internal nickel particles and spray them out to form micro-scale spherical shells, and uses the CVD method to directly grow MWNTs to obtain micro-focus CNT field emission cathodes. The microfocus electron source has the advantages of low turn-on electric field (<1 V/μm) and high current density (~1 A/cm 2 ). After graphene was coated on the top of CNT by DC electrophoresis and annealed at 750 ℃ in high temperature vacuum, the high-voltage strong emission performance of the micro-focus cathode was improved, and it had good working stability at 10 -5 Pa. The anti-ion bombardment performance of graphene and Excellent thermal conductivity plays an important role. The invention provides an effective means for the development of microscale (focus) field emission cathodes.
以上所揭露的仅为本发明较佳实施例而已，当然不能以此来限定本发明之权利范围，因此依本发明权利要求所作的等同变化，仍属本发明所涵盖的范围。The above disclosures are only preferred embodiments of the present invention, and of course, the scope of the rights of the present invention cannot be limited by this. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims (6)

  1. 一种基于碳纳米管的微焦点场发射电子源的制备方法，其特征在于包括以下步骤：A preparation method of a carbon nanotube-based microfocus field emission electron source, characterized in that it comprises the following steps:
    （1）在镍基片表面镀上金属铂层；(1) A metal platinum layer is plated on the surface of the nickel substrate;
    （2）在保护气体保护下，利用脉冲激光以负离焦对镍基片镀有金属铂的表面进行点烧蚀，负离焦烧蚀时激光焦点在镍基片内部，使内部镍金属融化，在镍金属蒸汽的推动作用下流向镍基片表面冷却后形成球壳；(2) Under the protection of protective gas, a pulsed laser is used to ablate the surface of the nickel substrate coated with metal platinum with negative defocusing. During the ablation with negative defocusing, the laser focus is inside the nickel substrate, so that the internal nickel metal is melted. , which flows to the surface of the nickel substrate under the driving action of the nickel metal vapor and forms a spherical shell after cooling;
    （3）利用化学气相沉积法在镍基底的激光烧蚀形成的球壳上直接生长碳纳米管阴极薄膜。(3) The carbon nanotube cathode film was directly grown on the spherical shell formed by laser ablation of the nickel substrate by chemical vapor deposition.
  2. 根据权利要求1所述的一种基于碳纳米管的微焦点场发射电子源的制备方法，其特征在于：所述的步骤（3）之后，还设置有步骤（4）：通过电泳法在碳纳米管阴极薄膜上沉积石墨烯，并进行真空高温退火。The method for preparing a carbon nanotube-based microfocus field emission electron source according to claim 1, characterized in that: after the step (3), a step (4) is further provided: electrophoresis on the carbon Graphene is deposited on the nanotube cathode film and annealed at high temperature in vacuum.
  3. 根据权利要求1所述的一种基于碳纳米管的微焦点场发射电子源的制备方法，其特征在于：所述的碳纳米管阴极薄膜为多壁碳纳米管阴极薄膜。The method for preparing a carbon nanotube-based microfocus field emission electron source according to claim 1, wherein the carbon nanotube cathode film is a multi-wall carbon nanotube cathode film.
  4. 根据权利要求1所述的一种基于碳纳米管的微焦点场发射电子源的制备方法，其特征在于：脉冲激光烧蚀的参数为：波长1064 nm、频率3 Hz、输出电流50-150 A以及负离焦距离在0.00-0.50 mm范围内。The method for preparing a carbon nanotube-based microfocus field emission electron source according to claim 1, wherein the parameters of the pulsed laser ablation are: wavelength 1064 nm, frequency 3 Hz, and output current 50-150 A As well as negative defocus distances in the range of 0.00-0.50 mm.
  5. 根据权利要求1所述的一种基于碳纳米管的微焦点场发射电子源的制备方法，其特征在于：所述的球壳的直径为≤350 μm。The method for preparing a carbon nanotube-based microfocus field emission electron source according to claim 1, wherein the diameter of the spherical shell is ≤350 μm.
  6. 一种如权利要求1所述方法所制备的基于碳纳米管的微焦点场发射电子源。A carbon nanotube-based microfocus field emission electron source prepared by the method of claim 1.
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