Electron source, electron gun and application of electron source

Abstract

The invention relates to an electron source, an electron gun and application of the electron source, the electron source comprises an optical fiber, a conductive connection layer and an electron emission layer, and the conductive connection layer is arranged on the outer surface of the optical fiber; the electron emission layer at least comprises an electron excitation layer electrically connected with the conductive connection layer, the electron emission layer is arranged on a laser emission path of the optical fiber, and laser emitted by the optical fiber can directly irradiate the electron emission layer, so that the electron excitation layer is excited by the laser and emits electrons; the electron excitation layer comprises a one-dimensional material, and the included angle between the axial direction of the one-dimensional material in the electron excitation layer and the laser emitting direction is larger than 0 degree and smaller than or equal to 90 degrees; the electron source can realize line emission, and is high in electron emission efficiency and good in stability.

Description

Technical Field

[0001] The present application relates to the technical field of electron sources, and particularly to an electron source, an electron gun, and an application of the electron source. Background Art

[0002] An electron source is a device capable of emitting an electron beam. Electron sources are mainly classified into thermionic electron sources, field emission electron sources, and photoemission electron sources according to the excitation method. Traditional thermionic electron sources mainly select materials with metallic properties such as tungsten filaments and lanthanum hexaboride. When heated to thousands of degrees Celsius, electrons are thermally excited to escape from the material surface to form vacuum electrons. Traditional field emission electron sources mainly select metal tips such as tungsten. Under the action of a strong electric field applied externally, a tip discharge effect is generated. Traditional photoemission electron sources use a metal material as a photocathode, and a laser is used to irradiate and excite the photocathode material to generate electrons. However, the electron emission efficiency of the above traditional electron sources is relatively low and the stability is poor. Therefore, how to improve the electron emission efficiency and the stability of the electron source in the electron source is a technical problem that needs to be solved urgently at present. Summary of the Invention

[0003] Based on this, the present application provides an electron source, an electron gun, and an application of the electron source, aiming to improve the electron emission efficiency and the stability of the electron source in the electron source.

[0004] In a first aspect of the present application, an electron source is provided. The electron source includes an optical fiber, a conductive connection layer, and an electron emission layer. The conductive connection layer is disposed on the outer surface of the optical fiber;

[0005] The electron emission layer at least includes an electron excitation layer electrically connected to the conductive connection layer. The electron emission layer is disposed on the laser emission path of the optical fiber, and the laser emitted by the optical fiber can directly irradiate the electron emission layer, so that the electron excitation layer is excited by the laser and emits electrons;

[0006] The electron excitation layer contains one-dimensional materials, and the axial direction of the one-dimensional materials in the electron excitation layer forms an angle greater than 0° and less than or equal to 90° with the emission direction of the laser.

[0007] In some embodiments, the axial direction of the one-dimensional materials in the electron emission layer forms an angle of 45° - 90° with the emission direction of the laser.

[0008] In some embodiments, the length of the one-dimensional materials is 1 μm - 200 μm, and can be optionally 10 μm - 30 μm.

[0009] In some embodiments, the diameter of the one-dimensional materials is 1 nm - 20 nm.

[0010] In some embodiments, the one-dimensional material includes one or more of nanotubes, nanowires, and nanoribbons.

[0011] In some embodiments, the nanotubes include one or more of carbon nanotubes and molybdenum disulfide nanotubes.

[0012] In some embodiments, the nanowires include one or more of gold nanowires, semiconductor nanowires, and tellurium quantum wires.

[0013] In some embodiments, the nanoribbons include one or more of carbon nanoribbons and molybdenum disulfide nanoribbons.

[0014] In some embodiments, the laser wavelength in the optical fiber is 200 nm to 2000 nm, and the pulse power is 1 nW to 1 W.

[0015] In some embodiments, the electron emission layer further includes an auxiliary layer, and the auxiliary layer is stacked on the side of the electron excitation layer close to the optical fiber; or,

[0016] The auxiliary layer is stacked on the side of the electron excitation layer away from the optical fiber.

[0017] In some embodiments, the thickness of the auxiliary layer is 0.1 nm to 100 nm, and the light transmittance of the auxiliary layer is ≥10%.

[0018] In some embodiments, the auxiliary layer has conductivity, and the auxiliary layer is electrically connected to the conductive connection layer.

[0019] In some embodiments, the material of the auxiliary layer includes one or more of graphene and conductive metals.

[0020] In some embodiments, the optical fiber is a solid-core optical fiber, a tip optical fiber, a side-cut optical fiber, or a porous optical fiber.

[0021] In a second aspect of the present application, an electron gun is provided. The electron gun includes a housing, a grid, an anode, and the electron source according to the first aspect of the present application. The electron source is fixed in the housing, and the grid and the anode are sequentially arranged on the electron emission side of the electron source.

[0022] In a third aspect of the present application, an application of the electron source according to the first aspect of the present application is provided. The application of the electron source includes at least one of an electron microscope, an electron beam lithography machine, an X-ray tube, a free electron laser, and a display.

[0023] Compared with the prior art, the above electron source, electron gun, and application of the electron source have at least the following beneficial effects:

[0024] In the above electron source, the included angle between the axis of the one-dimensional material and the laser emission direction is greater than 0° and less than or equal to 90°, which can achieve line emission, improve the emission area and efficiency. When the above electron source works, the laser is directly transmitted through the optical fiber, without involving complex and unstable external space optical paths, greatly improving the structural simplicity and operation convenience of the electron source, reducing the interference of the external space on the electron beam stability, and enabling the electron source to have ultra-high stability and integration; the one-dimensional material has an atomic-level diameter, strong interaction with the light field and electric field, and high electron emission efficiency, which is very suitable for an ultrafast electron source with a narrow pulse width; moreover, the one-dimensional material has no dangling bonds, stable properties, high melting point, and is not easily damaged, and can be applied to scenarios with high-power excitation. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 FIG. is a schematic structural diagram of the electron source according to Embodiment 1 of the present application, where 110a - optical fiber; 1101a - core; 1102a - cladding; 121a - electron excitation layer; 130a - conductive connection layer.

[0026] Figure 2 is Figure 1 an enlarged view of position A in FIG.

[0027] Figure 3 is Figure 1 a cross-sectional view taken along the B - B direction in FIG.

[0028] Figure 4 FIG. is a schematic structural diagram of the electron source according to Embodiment 2 of the present application, where 110b - optical fiber; 1101b - core; 1102b - cladding; 120b - electron emission layer; 121b - electron excitation layer; 122b - auxiliary layer; 130b - conductive connection layer.

[0029] Figure 5 is Figure 4 a cross-sectional view taken along the C - C direction in FIG.

[0030] Figure 6 FIG. is a schematic internal structure diagram of an electron gun according to an embodiment of the present application, where 100 - electron source; 200 - grid; 300 - anode. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] In order to make the above objects, features, and advantages of the present application more obvious and understandable, the following detailed description of the specific embodiments of the present application is provided. Many specific details are set forth in the following description in order to fully understand the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0032] In this application, terms such as "first aspect", "second aspect", "third aspect", etc. are only for descriptive purposes and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly specifying the importance or quantity of the indicated technical features. Moreover, "first", "second", "third", etc. only serve the purpose of non-exhaustive enumerative description and should be understood not to constitute a closed limitation on quantity.

[0033] In this application, "optionally", "optional", "option" mean either available or not, that is, any one of the two alternative options of "having" or "not having". If the term "optional" appears multiple times in a technical solution, without special instructions and without contradictions or mutual constraints, each "optional" is independent of each other.

[0034] In this application, regarding numerical ranges, unless otherwise specified, the above numerical ranges are considered continuous and include the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when the range refers to integers, it includes every integer between the minimum and maximum values of the range. In addition, when multiple ranges are provided to describe features or characteristics, these ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0035] In this application, for technical features described in an open-ended manner, it includes closed technical solutions composed of the listed features, as well as open technical solutions containing the listed features.

[0036] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by those skilled in the technical field to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used in this application includes any and all combinations of one or more of the related listed items. The meaning of the term "multiple" in this application is at least two, such as two, three, etc., unless otherwise specifically defined.

[0037] In this application, unless otherwise clearly specified and limited, terms such as "install", "connect", "join", "fix", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two components or the interaction relationship between two components, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0038] Electron sources can be mainly divided into thermionic electron sources, field emission electron sources, and photoemission electron sources according to the excitation method. Traditional thermionic electron sources and traditional field emission electron sources lack effective modulation of physical parameters such as the energy, momentum, deflection state, and spatio-temporal distribution of electrons. Their operating modes and working environments mostly fall within the scope of electron beam applications with continuous time and Gaussian spatial distribution, and it is difficult to meet the research related to particle interactions and ultrafast time resolution in modern physics. Moreover, whether it is a thermionic electron source or a field emission electron source, the regulation of electron emission properties is limited, and it is impossible to balance coherence, pulsed nature, emission efficiency, and stability.

[0039] Some traditional photoemission electron sources open an optical window on the side of the electron gun and focus free laser light on the surface of the metal tip to excite electrons. However, this method requires modification of the instrument itself and is sensitive to environmental factors such as vibration, and its long-term stability is poor. Some other traditional photoemission electron sources perform electron emission on the surface of the metal layer at the tip or end face of the optical fiber. However, since the distance between the metal bottom layer that directly interacts with the laser and the metal surface layer where electron emission occurs is relatively far, the electrons generated by the action of the bottom layer are easily affected by lattice scattering during the process of passing through the metal layer, which affects the emission efficiency. Moreover, when the thickness of the metal layer is thinned, the melting point of the metal decreases, it is easily damaged, and the electron emission efficiency and stability are affected.

[0040] Based on this, an embodiment of the present application provides an electron source, which includes an optical fiber, a conductive connection layer, and an electron emission layer. The conductive connection layer is disposed on the outer surface of the optical fiber;

[0041] The electron emission layer at least includes an electron excitation layer electrically connected to the conductive connection layer. The electron emission layer is disposed on the laser emission path of the optical fiber, and the laser emitted by the optical fiber can directly irradiate the electron emission layer, so that the electron excitation layer is excited by the laser and emits electrons;

[0042] The electron excitation layer contains one-dimensional materials, and the axial direction of the one-dimensional materials in the electron excitation layer forms an angle greater than 0° and less than or equal to 90° with the laser emission direction.

[0043] In the above electron source, the axial direction of the one-dimensional materials forms an angle greater than 0° and less than or equal to 90° with the laser emission direction, which can achieve linear emission and improve the emission area and efficiency. When the above electron source works, the laser is directly transmitted through the optical fiber, without involving complex and unstable external spatial optical paths, greatly improving the structural simplicity and operation convenience of the electron source, reducing the interference of the external space on the electron beam stability, and enabling the electron source to have ultra-high stability and integration; the one-dimensional materials have an atomic-level diameter, have a strong interaction with the light field and electric field, and have a high electron emission efficiency, and are very suitable for ultrafast electron sources with narrow pulse widths; moreover, the one-dimensional materials have no dangling bonds, are stable in nature, have a high melting point, are not easily damaged, and can be applied to scenarios with high-power excitation.

[0044] It is understandable that the angle between the axial direction of the one-dimensional material and the laser emission direction includes, but is not limited to: 1°, 5°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°, 60°, 70°, 80°, 90°. There can be multiple one-dimensional materials in the electron excitation layer. In this case, the angles between the axial directions of different one-dimensional materials and the laser emission direction can be different. For example, there are 10 one-dimensional materials in the electron excitation layer, among which the axial directions of 3 one-dimensional materials are all 45° with the laser emission direction, the axial directions of 2 one-dimensional materials are all 60° with the laser emission direction, and the axial directions of 5 one-dimensional materials are all 80° with the laser emission direction. To balance the difficulty of the manufacturing process, the angles between the axial directions of the one-dimensional materials in the electron excitation layer and the laser emission direction are the same.

[0045] It should be noted that the laser light-emitting path of the optical fiber in this application refers to the path where the laser irradiates in the optical fiber. Taking a solid-core optical fiber as an example, the laser emission position of the solid-core optical fiber is at the core end face, that is, the electron emission layer can be arranged at the core; taking a side-cut optical fiber as an example, the laser emission position of the side-cut optical fiber is on the side-cut side of the side-cut optical fiber, that is, the electron emission layer can be arranged at the side-cut. It can be understood that in this application, the electron excitation layer can be in direct contact with the laser emission surface of the optical fiber, or can be supported by other structural layers. That is to say, the laser emitted from the optical fiber can directly irradiate on the electron emission layer, so that the electron excitation layer is excited by the laser and emits electrons.

[0046] It also should be noted that the purpose of the electrically conductive connection layer being electrically connected to the electron excitation layer in this application is to connect the one-dimensional materials in the electron excitation layer to the external circuit to form a complete circuit and realize charge replenishment and electric field control. As an implementation manner, the electrically conductive connection layer in this application can be directly connected to the electron excitation layer. In other implementation manners, the electrically conductive connection layer and the electron excitation layer can also be electrically connected through other conductive structures. By way of example, taking a solid-core optical fiber as an example, the electrically conductive connection layer is arranged on the side of the solid-core optical fiber, the electron excitation layer is arranged at the core of the solid-core optical fiber, and the electrically conductive connection layer and the electron excitation layer are electrically connected, and there is no electrically conductive connection layer at the core.

[0047] In some implementation manners, the one-dimensional material also includes doping elements. Optionally, the doping elements include one or more of alkali metal elements, alkaline earth metal elements, transition metal elements, rare earth elements, halogen elements, and light elements. Among them, the light elements include at least one of B, C, N, and O. The doping elements can improve the conductivity of the one-dimensional material, change the work function, and adjust the electron emission performance. For example, alkali metal elements and alkaline earth metal elements can improve the conductivity of the one-dimensional material, and at the same time can reduce the work function of the one-dimensional material to increase the emission beam current; elements such as B, C, N, O, F, and rare earth can create discrete energy levels to obtain an electron beam with a narrow energy.

[0048] In some embodiments, the angle between the axis of the one-dimensional material in the electron excitation layer and the laser emission direction is 45° to 90°. Thereby, it can not only ensure strong interaction between the laser and the one-dimensional material, but also ensure that electrons are emitted from the side of the one-dimensional material, which can further improve the emission efficiency and stability of the electron source.

[0049] In some embodiments, the length of the one-dimensional material is 1 μm to 200 μm. If the length of the one-dimensional material is too long, it is difficult to fabricate; if the length of the one-dimensional material is too short, the emission length is short, the electron emission efficiency is low, and it is difficult for the one-dimensional material in the electron excitation layer to contact the conductive connection layer. It can be understood that the length of the one-dimensional material includes but is not limited to: 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 20 μm, 30 μm, 50 μm, 70 μm, 100 μm, 130 μm, 150 μm, 180 μm, 200 μm. Further, the length of the one-dimensional material is 10 μm to 30 μm.

[0050] In some embodiments, the diameter of the one-dimensional material is 1 nm to 20 nm. When the diameter of the one-dimensional material is within the above range, the emission efficiency and stability of the electron source can be further improved. If the diameter of the one-dimensional material is too large, the electric field enhancement factor of the one-dimensional material is not large enough, and the electron emission efficiency is low. It can be understood that the diameter of the one-dimensional material includes but is not limited to: 1 nm, 3 nm, 5 nm, 7 nm, 10 nm, 13 nm, 15 nm, 17 nm, 20 nm.

[0051] In some embodiments, the one-dimensional material includes one or more of nanotubes, nanowires, and nanoribbons. Selecting the one-dimensional materials of the above types is beneficial to further improving the emission efficiency and stability of the electron source.

[0052] In some embodiments, the nanotubes include one or more of carbon nanotubes and molybdenum disulfide nanotubes. Selecting the nanotubes of the above types is beneficial to further improving the emission efficiency and stability of the electron source.

[0053] In some embodiments, the nanowires include one or more of gold nanowires, semiconductor nanowires, and tellurium quantum wires (Te quantum wires). Selecting the nanotubes of the above types is beneficial to further improving the emission efficiency and stability of the electron source. Optionally, the semiconductor nanowires include GaAs nanowires.

[0054] In some embodiments, the nanoribbons include one or more of carbon nanoribbons and molybdenum disulfide nanoribbons. Thereby, the emission efficiency and stability of the electron source can be further improved.

[0055] In some embodiments, the laser wavelength in the optical fiber is 200 nm to 2000 nm, and the pulse power is 1 nW to 1 W. Controlling the laser wavelength and pulse power within the above ranges can avoid the problem of melting caused by laser irradiation of the conductive metal, and ensure that the auxiliary layer has the functions of support and conductivity. It can be understood that the laser wavelength in the optical fiber includes but is not limited to: 200 nm, 300 nm, 500 nm, 700 nm, 900 nm, 1100 nm, 1300 nm, 1500 nm, 1700 nm, 1900 nm, 2000 nm; the pulse power includes but is not limited to: 1 nW, 10 -8 W, 10 -7 W, 10 -6 W, 10 -5 W, 10 -4 W, 10 -3 W, 0.01 W, 0.1 W, 1 W.

[0056] In some embodiments, the conductive connection layer is provided with electrodes. Optionally, the conductive connection layer can completely cover the outer surface of the optical fiber. Of course, it can also partially cover the outer surface of the optical fiber, and there is no conductive connection layer on the light output path of the laser.

[0057] In some embodiments, the thickness of the conductive connection layer is 0.1 nm to 100 nm.

[0058] In some embodiments, the material of the conductive connection layer includes one or more of metals, graphite, and low-dimensional materials. Metals include, for example, but are not limited to gold, and low-dimensional materials include at least one of zero-dimensional materials, one-dimensional materials, and two-dimensional materials. The zero-dimensional material can be, for example, a quantum dot, the one-dimensional material can be, for example, a carbon nanotube, and the two-dimensional material can be, for example, graphene.

[0059] In some embodiments, the electron emission layer further includes an auxiliary layer, and the auxiliary layer is stacked on the side of the electron excitation layer close to the optical fiber; or,

[0060] The auxiliary layer is stacked on the side of the electron excitation layer far from the optical fiber.

[0061] The auxiliary layer in the above embodiments can play a role in structurally supporting the electron excitation layer, that is, the electron excitation layer is disposed on the auxiliary layer; or when the electron excitation layer cannot be directly connected and conducted with the conductive connection layer, it can be connected to the conductive connection layer through the conductive auxiliary layer, so that the electron excitation layer and the conductive connection layer achieve electron conduction by using the auxiliary layer.

[0062] In some embodiments, the one-dimensional materials in the electron excitation layer are arranged in a low-density manner. At this time, the electron energy dispersion emitted by the electron excitation layer is low, and the brightness of the electron source is high. Low density means that the adjacent one-dimensional materials in the electron excitation layer do not contact and cannot achieve electron conduction.

[0063] In some embodiments, the one-dimensional materials in the electron excitation layer are arranged in a high-density manner. Thus, a large-beam electron source can be formed. High density means that adjacent one-dimensional materials in the electron excitation layer are in contact, enabling electron conduction.

[0064] In some embodiments, low density refers to the number of one-dimensional materials per unit area. For example, a density less than 1 per nm 2 is low density, and greater than 1 per nm 2 is high density.

[0065] In some embodiments, the thickness of the auxiliary layer is 0.1 nm to 100 nm, and the light transmittance of the auxiliary layer is ≥10%. When the thickness and light transmittance of the auxiliary layer are within the above ranges, the laser emitted from the optical fiber can pass through the auxiliary layer to reach the electron excitation layer, thereby further improving the electron emission efficiency in the electron source and the stability of the electron source. It is understandable that the thickness of the auxiliary layer includes but is not limited to: 0.1 nm, 0.5 nm, 1.5 nm, 5 nm, 10 nm, 15 nm, 25 nm, 35 nm, 45 nm, 55 nm, 65 nm, 75 nm, 85 nm, 95 nm, 100 nm; the light transmittance of the auxiliary layer includes but is not limited to: 10%, 15%, 25%, 35%, 45%, 50%, 55%, 65%, 75%, 85%, 95%, 99%, etc.

[0066] In some embodiments, the thickness of the auxiliary layer is 0.5 nm to 10 nm, and the light transmittance of the auxiliary layer is ≥50%. When the thickness and light transmittance of the auxiliary layer are within the above ranges, the laser emitted from the optical fiber can pass through the auxiliary layer to reach the electron excitation layer, thereby further improving the electron emission efficiency in the electron source and the stability of the electron source.

[0067] In some embodiments, the auxiliary layer has conductivity and is electrically connected to the conductive connection layer. On the one hand, the auxiliary layer can utilize its conductivity to connect all the one-dimensional materials in the electron excitation layer to the external circuit, and on the other hand, it can improve the heat dissipation performance of the electron excitation layer.

[0068] In some embodiments, the material of the auxiliary layer includes one or more of graphene, conductive metal, and semiconductor thin film. The auxiliary layer in the above embodiments can use a conductive metal, and by controlling the laser wavelength and pulse power in the optical fiber, the problem of laser irradiation causing melting of the conductive metal can be avoided, ensuring that the auxiliary layer has the functions of support and conductivity. Optionally, the laser wavelength is 200 nm to 2000 nm, and the pulse power is 1 nW to 1 W. Optionally, the conductive metal includes one or more of gold, silver, and copper.

[0069] In some embodiments, the electron excitation layer is located on one side in the longitudinal direction of the optical fiber. Thereby, the laser emitted from the optical fiber can reach the electron excitation layer, further improving the electron emission efficiency in the electron source and the stability of the electron source.

[0070] In some embodiments, the optical fiber is a solid-core optical fiber, a tip optical fiber, a side-cut optical fiber, or a holey optical fiber. Optionally, the optical fiber is a solid-core optical fiber. Further optionally, the solid-core optical fiber includes a single-mode optical fiber, a multi-mode optical fiber, a polarization-maintaining optical fiber, or a multi-core optical fiber.

[0071] In some embodiments, the optical fiber is a solid-core optical fiber. In this embodiment, the one-dimensional material can be directly placed on the end face of the optical fiber, and the optical field and the one-dimensional material directly interact with each other with a high interaction intensity to achieve high-brightness electron emission. In addition, different diameters of micro-nano optical fibers can be drawn to enable the interaction of light with different modes and intensities with the one-dimensional material to achieve precisely controlled electron emission parameters.

[0072] In some embodiments, the optical fiber is a tip optical fiber. In this embodiment, the electron emission layer is disposed on the tip optical fiber, and the tip geometric structure of the tip optical fiber can increase the field emission enhancement factor, thereby enabling a higher-brightness electron source to be obtained.

[0073] In some embodiments, the optical fiber is a side-cut optical fiber. In this embodiment, the electron emission layer is disposed on the side-cut surface of the side-cut optical fiber, and the evanescent wave leaking from the core interacts with the one-dimensional material in the electron excitation layer in the horizontal direction. The one-dimensional material in the electron excitation layer of this embodiment obtains the edge state of the zero-dimensional material at the side-cut, forming a new electron emission structure, which can endow the electron source with functions such as high brightness, low energy dispersion, and narrow pulse width.

[0074] In some embodiments, the optical fiber is a holey optical fiber. The holey optical fiber in this embodiment is a type of optical fiber with microstructures or completely hollow, including photonic crystal fibers, anti-resonant fibers, or capillary fibers, etc. The one-dimensional material in the electron excitation layer can be disposed in the pores or pore walls of the holey optical fiber, enabling the laser to have a long interaction distance with the one-dimensional material, thereby achieving large beam current and high-brightness electron emission.

[0075] It should be noted that this application does not make specific requirements and special limitations on the size of the optical fiber, and those skilled in the art can reasonably select the size of the optical fiber according to actual usage requirements.

[0076] In some embodiments, the electron excitation layer is formed by at least one of dry transfer, wet transfer, and direct growth.

[0077] In some embodiments, the electron excitation layer is prepared by a dry transfer method. The preparation method includes: transferring the one-dimensional material to the tape by mechanical exfoliation, and transferring the one-dimensional material to the laser output side of the optical fiber through the tape.

[0078] In some embodiments, the electron excitation layer is prepared by a wet transfer method. The preparation method includes: directly preparing the one-dimensional material in a solution and floating it on the liquid surface, and contacting the material on the liquid surface with the optical fiber and drying.

[0079] In some embodiments, the electron excitation layer is prepared by a direct growth method. The preparation method includes: directly preparing the electron excitation layer on the laser output side of the optical fiber by at least one of chemical vapor deposition, physical vapor deposition, molecular beam epitaxy, and liquid filling.

[0080] Another embodiment of the present application provides an electron gun, which includes a housing, a grid, an anode, and the above-mentioned electron source of the present application. The electron source is fixed in the housing, and a grid and an anode are sequentially arranged on the electron output side of the electron source. The grid in the above-mentioned electron gun is used to limit the shape of the electron beam, and the anode is used to accelerate the electrons. When electrons are excited and emitted from the electron source, they will interact with the electrostatic field established by the grid and the space charge of the electrons themselves to form an electron beam with a certain shape and emit it from the anode for use.

[0081] Another embodiment of the present application provides an application of the above-mentioned electron source of the present application. The application of the electron source includes at least one of an electron microscope, an electron beam exposure machine, an X-ray tube, a free electron laser, and a display.

[0082] To further illustrate the present application, the technical solutions of the present application will be described in detail below in conjunction with specific embodiments. For those not specified in the embodiments, the techniques or conditions described in the literature in the art or according to the product specifications are followed. Those reagents or instruments not indicated by the manufacturer can be obtained as conventional products through commercial procurement.

[0083] In the following embodiments, the conductive connection layer is a metal layer covering the side surface of the optical fiber with a thickness of 60 nm. The conductive connection layer is in contact connection with the auxiliary layer or the electron excitation layer, and the material of the metal layer is elemental gold.

[0084] Example 1

[0085] Carbon nanotubes are grown on a silicon wafer by chemical vapor deposition and transferred to a polycarbonate film by acid etching.

[0086] Reference Figures 1 - 3 , the preparation method of the electron source includes the following steps:

[0087] (1) Remove the coating layer at the end of the single-mode solid optical fiber 110a and cut the cross-section of the optical fiber 110a to make it flat. Use a polymer ball to block one end of the fiber core 1101a. The diameter of the polymer ball is between the diameter of the fiber core 1101a and the diameter of the cladding 1102a. The diameter of the fiber core 1101a of the single-mode optical fiber 110a is 8.2 μm, and the diameter of the optical fiber 110a is 125 μm.

[0088] (2) Deposit gold on the optical fiber 110a by evaporation coating to ensure that the gold element is firmly deposited on the end face and the uncoated position at the end of the optical fiber 110a, forming a conductive connection layer 130a made of gold with a thickness of 54 nm. Soak the end of the blocked fiber core 1101a with acetone to dissolve the polymer ball and peel off the coating on the polymer ball, exposing the fiber core 1101a at the end face position of the optical fiber 110a, so as to form a relatively flat annular electrode at the electron emission end.

[0089] (3) Transfer the carbon nanotubes on the polycarbonate film to the front of the perforated glass slide and suspend them so that they can be observed under a microscope. Stick a circular heating sheet on the back. The heating sheet is connected to a power supply. The perforated glass slide is fixed on the microscope stage. Fix the prefabricated electrode optical fiber obtained in step (2) on the displacement stage under the stage, so that the objective lens, the hole in the heating sheet, the glass slide, the carbon nanotubes, and the end face of the prefabricated electrode optical fiber are collinear and arranged in sequence from top to bottom.

[0090] (4) Observe the position of the prefabricated electrode under the microscope and complete the horizontal alignment. Apply a voltage for preheating. Move the optical fiber displacement stage to make the annular electrode and the carbon nanotubes contact to form Newton's rings, and slowly increase the voltage to make the annular electrode and the carbon nanotubes contact more closely.

[0091] (5) After the annular electrode and the carbon nanotubes are completely attached, increase the heating voltage to completely melt the polycarbonate film. Remove the optical fiber and soak it in acetone to dissolve it.

[0092] In the electron source prepared in this embodiment, the carbon nanotubes form an electron excitation layer 121a. The included angle θ between the axial direction of the carbon nanotubes and the emission direction of the laser is 10°. The diameter of the carbon nanotubes is 1 nm, and the length is 200 μm.

[0093] Example 2

[0094] Grow carbon nanotubes on a silicon wafer by chemical vapor deposition method and transfer them to a polycarbonate film by acid etching.

[0095] Reference Figures 4 - 5 , the preparation method of the electron source includes the following steps:

[0096] (1) Remove the coating layer at the end of the single-mode solid fiber 110b and cut the cross-section of the fiber 110b to make it flat. Use a polymer ball to block one end of the fiber core 1101b. The diameter of the polymer ball is between the diameter of the fiber core 1101b and the diameter of the cladding 1102b. The diameter of the fiber core 1101b of the single-mode fiber 110b is 8.2 μm, and the diameter of the fiber 110b is 125 μm.

[0097] (2) Deposit gold on the fiber 110b by evaporation coating method to ensure that the elemental gold is firmly deposited at the end face and the uncoated position at the end of the fiber 110b, forming a conductive connection layer 130b made of gold with a thickness of 54 nm. Soak the end of the fiber core 1101b blocked by the polymer ball in acetone to dissolve the polymer ball and peel off the coating on the polymer ball, exposing the fiber core 1101b at the end face position of the fiber 110b, so as to form a relatively flat ring electrode at the electron emission end. Deposit an auxiliary layer 122b made of gold on the end face of the fiber 110b with the conductive connection layer 130b. The thickness of the auxiliary layer 122b is 10 nm, and the auxiliary layer 122b is electrically connected to the conductive connection layer 130b.

[0098] (3) Transfer the carbon nanotubes on the polycarbonate film to the front of the perforated glass slide and suspend them so that they can be observed under a microscope. Stick a ring-shaped heating sheet on the back. The heating sheet is connected to a power supply. The perforated glass slide is fixed on the microscope stage. Fix the prefabricated electrode fiber obtained in step (2) on the displacement stage under the stage, so that the objective lens, the hole in the heating sheet, the glass slide, the carbon nanotubes, and the end face of the prefabricated electrode fiber are collinear and arranged in sequence from top to bottom;

[0099] (4) Observe the position of the prefabricated electrode under the microscope and complete the horizontal alignment. Apply a voltage for preheating. Move the fiber displacement stage to make the ring electrode and the carbon nanotubes contact to form Newton's rings, and slowly increase the voltage to make the ring electrode and the carbon nanotubes contact more closely.

[0100] (5) After the ring electrode and the carbon nanotubes are completely attached, increase the heating voltage to completely melt the polycarbonate film. Remove the fiber and soak it in acetone to dissolve it.

[0101] In the electron source prepared in this embodiment, the carbon nanotubes form an electron excitation layer 121b. The included angle between the axial direction of the carbon nanotubes and the laser emission direction is 10°. The diameter of the carbon nanotubes is 1 nm, and the length is 200 μm. The electron excitation layer 121b and the auxiliary layer 122b constitute an electron emission layer 120b.

[0102] Example 3

[0103] Prepare an electron source according to the structure of Example 2, the difference is that: the included angle between the axial direction of the carbon nanotubes and the laser emission direction is 90°.

[0104] Example 4

[0105] Prepare an electron source according to the structure of Example 2, with the difference that the diameter of the carbon nanotubes is 3 nm.

[0106] Example 5

[0107] Prepare an electron source according to the structure of Example 1, with the difference that the carbon nanotubes in Example 1 are replaced by gold nanowires.

[0108] Comparative Example 1

[0109] Prepare an electron source according to the structure of Example 1, with the difference that the electron excitation layer in Example 1 is replaced by a gold layer with a thickness of 100 nm, and the gold layer is obtained by deposition.

[0110] As Figure 6 shown, the electron sources 100 prepared by the above examples and comparative examples are assembled into an electron gun. The electron gun further includes a housing, a grid 200, and an anode 300, and the performance of the prepared electron gun is tested.

[0111] Performance Test of Electron Gun

[0112] (1) Stability

[0113] When the excitation power is 50% of the damage power, the vacuum degree is 2×10 -5 Pa, continuously emit current for 1 h. After removing the bad points, calculate the difference between the maximum current and the minimum current and the average current, that is, the stability parameter = (maximum current - minimum current) / average current. The smaller the value of the stability parameter, the better the stability of the electron source of the electron gun.

[0114] (2) Lifetime

[0115] When the excitation power is 50% of the damage power, the vacuum degree is 2×10 -5 Pa, continuously emit current until the time when the current decays to less than 10% of the initial value is defined as the lifetime.

[0116] (3) Operating Vacuum Degree

[0117] When the excitation power is 50% of the damage power, continuously emit current, gradually increase the operating environment vacuum degree of the electron gun until the current shows a rapid decay (rapid decay is defined as the current decays by more than 50% within 1 min), and the vacuum degree at this time is defined as the operating vacuum degree. The higher the operating vacuum degree, the higher the electron emission efficiency in the electron source of the electron gun.

[0118] Among them, the damage power refers to the laser power when the material is damaged under the irradiation of a 100 fs pulsed laser. For example, the damage power of graphene is 0.25 J / cm2 , the damage threshold of gold is 0.1 J / cm 2 .

[0119] The test results are shown in Table 1.

[0120] Table 1

[0121]

[0122] As can be seen from Table 1, compared with the electron gun of Comparative Example 1, the working vacuum degree of the electron guns of Examples 1-5 is higher, the stability is better, and the service life is longer, indicating that Examples 1-5 provided in the present application effectively improve the electron emission efficiency in the electron source and the stability of the electron source.

[0123] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0124] The above-described embodiments only represent several implementation manners of the present application. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims, and the specification can be used to explain the content of the claims.

Claims

1. An electron source, characterized in that, The electron source includes an optical fiber, a conductive connection layer, and an electron emission layer. The conductive connection layer is disposed on the outer surface of the optical fiber; The electron emission layer at least includes an electron excitation layer electrically connected to the conductive connection layer. The electron emission layer is disposed on the laser emission path of the optical fiber, and the laser emitted from the optical fiber can directly irradiate the electron emission layer, so that the electron excitation layer is excited by the laser and emits electrons; The electron excitation layer contains one-dimensional materials, and the axial direction of the one-dimensional materials in the electron excitation layer forms an angle greater than 0° and less than or equal to 90° with the emission direction of the laser.

2. The electron source according to claim 1, characterized in that, The axial direction of the one-dimensional materials in the electron excitation layer forms an angle of 45° to 90° with the emission direction of the laser.

3. The electron source according to claim 1, wherein, The length of the one-dimensional material is 1 μm to 200 μm, and can be optionally 10 μm to 30 μm.

4. The electron source according to any one of claims 1 to 3, characterized in that, The diameter of the one-dimensional material is 1 nm to 20 nm.

5. The electron source according to any one of claims 1 to 3, characterized in that, The one-dimensional material includes one or more of nanotubes, nanowires, and nanoribbons; Optionally, the nanotubes include one or more of carbon nanotubes and molybdenum disulfide nanotubes; Optionally, the nanowires include one or more of gold nanowires, semiconductor nanowires, and tellurium quantum wires; Optionally, the nanoribbons include one or more of carbon nanoribbons and molybdenum disulfide nanoribbons.

6. The electron source according to any one of claims 1 to 3, characterized in that, The laser wavelength in the optical fiber is 200 nm to 2000 nm, and the pulse power is 1 nW to 1 W.

7. The electron source according to any one of claims 1 to 3, characterized in that, The electron emission layer further includes an auxiliary layer, and the auxiliary layer is stacked on the side of the electron excitation layer close to the optical fiber; or, The auxiliary layer is stacked on the side of the electron excitation layer away from the optical fiber.

8. The electron source according to claim 7, characterized in that, The thickness of the auxiliary layer is 0.1 nm to 100 nm, and the light transmittance of the auxiliary layer ≥ 10%.

9. The electron source according to claim 7, characterized in that, The auxiliary layer has conductivity, and the auxiliary layer is electrically connected to the conductive connection layer.

10. The electron source according to claim 7, wherein The material of the auxiliary layer includes one or more of graphene and conductive metals.

11. The electron source according to any one of claims 1 to 3, characterized in that, The optical fiber is a solid-core optical fiber, a tip optical fiber, a side-cut optical fiber, or a porous optical fiber.

12. An electron gun, characterized in that, The electron gun includes a housing, a grid, an anode, and the electron source according to any one of claims 1 to 11. The electron source is fixed in the housing, and the grid and the anode are sequentially arranged on the electron emission side of the electron source.

13. An application of the electron source according to any one of claims 1 to 11, characterized in that, The applications of the electron source include at least one of an electron microscope, an electron beam lithography machine, an X-ray tube, a free electron laser, and a display.

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