Electron source, preparation method of electron source, electron gun and application of electron source

Abstract

The invention relates to an electron source, a preparation method of the electron source, an electron gun and application of the electron source. The electron source comprises an optical fiber and an electron emission layer, the light emitting end of the optical fiber is provided with a tip part, the electron emission layer at least comprises an electron excitation layer, and the electron excitation layer covers the surface of the tip part of the optical fiber. The electron excitation layer comprises at least one of a zero-dimensional material, a one-dimensional material and a two-dimensional material. Low-dimensional materials such as zero-dimensional materials, one-dimensional materials or two-dimensional materials are adopted as materials of the electron excitation layer, the low-dimensional materials have the atomic-scale thickness, back-incident electrons can be emitted without in-vivo transmission, and the electron emission efficiency is high; the low-dimensional material is free of dangling bonds, stable in property, high in melting point and not prone to damage, can be suitable for high-power excitation scenes and has the advantages of being good in stability, long in service life and the like.

Description

Technical Field

[0001] This application relates to the technical field of electron sources, and particularly to an electron source, a preparation method of the electron source, an electron gun, and an application of the electron source. Background Art

[0002] An electron source is a device that generates vacuum electrons. Traditional electron sources are mainly divided into thermionic electron sources, field emission electron sources, and photoemission electron sources according to the excitation method. Thermionic electron sources mainly select metal materials. When heated to thousands of degrees Celsius, electrons are thermally excited to escape from the surface of the material to form vacuum electrons. Field emission electron sources mainly select metal tips. Under the action of a strong electric field applied from the outside, a tip discharge effect is generated. A photoemission electron source uses a metal material as a photocathode, and uses laser irradiation to excite the photocathode material to generate electrons.

[0003] However, the electron sources in traditional technologies cannot balance the emission efficiency and stability. How to provide an electron source with high electron emission efficiency and good stability has become an urgent technical problem to be solved at present. Summary of the Invention

[0004] Based on this, in view of the problem that the electron sources in traditional technologies cannot balance the emission efficiency and stability, it is necessary to provide an electron source, a preparation method of the electron source, an electron gun, and an application of the electron source.

[0005] According to the first aspect of the present application, an electron source is provided, including:

[0006] An optical fiber, the light-emitting end of the optical fiber is provided with a pointed end; and

[0007] An electron emission layer, the electron emission layer at least includes an electron excitation layer, and the electron excitation layer covers the surface of the pointed end of the optical fiber;

[0008] Wherein, the optical fiber includes a core for transmitting laser, and the laser emitted from the core can directly irradiate on the electron emission layer, so that the electron excitation layer is excited by the laser emitted from the core and emits electrons;

[0009] The electron excitation layer includes at least one of zero-dimensional materials, one-dimensional materials, and two-dimensional materials.

[0010] In one embodiment, the thickness of the electron excitation layer is less than or equal to 50 nm.

[0011] In one embodiment, the axial direction of the one-dimensional material in the electron excitation layer forms an angle of 0 to 90° with the emission direction of the emitted laser.

[0012] In one embodiment, the electron excitation layer includes at least two two-dimensional materials stacked in sequence along the laser emission direction; or,

[0013] the electron excitation layer includes at least two two-dimensional materials with different materials connected to each other in the same plane.

[0014] In one embodiment, the materials in the electron excitation layer include one-dimensional materials and zero-dimensional materials disposed at the ends and / or sides of the one-dimensional materials.

[0015] In one embodiment, the electron excitation layer includes zero-dimensional materials and two-dimensional materials, and the zero-dimensional materials are disposed on the surface of the two-dimensional materials.

[0016] In one embodiment, the electron excitation layer includes one-dimensional materials and two-dimensional materials, and the one-dimensional materials are disposed on the surface of the two-dimensional materials.

[0017] In one embodiment, the electron source further includes a conductive connection layer disposed on the outer surface of the optical fiber and electrically connected to the electron excitation layer.

[0018] In one embodiment, the electron excitation layer includes a first part;

[0019] The projection of the first part in the target plane perpendicular to the core extension direction covers the projection of the core in the target plane;

[0020] The first part is electrically connected to the conductive connection layer.

[0021] In one embodiment, the electron excitation layer further includes a second part connected to the first part; the projection of the second part in the target plane is located on the periphery of the projection of the first part in the target plane; and the second part overlaps with the conductive connection layer.

[0022] In one embodiment, the conductive connection layer includes a first conductive part disposed at the tip of the optical fiber and a second conductive part connected to the first conductive part and disposed on the circumferential side surface of the optical fiber;

[0023] The first conductive part overlaps with the second part.

[0024] In one embodiment, the electron emission layer further includes an auxiliary layer, and the auxiliary layer is stacked on one side of the surface of the electron excitation layer close to the tip; or,

[0025] the auxiliary layer is stacked on one side of the surface of the electron excitation layer away from the tip.

[0026] In one embodiment, the auxiliary layer satisfies at least one of the following conditions:

[0027] (1) The auxiliary layer includes at least one of a conductive support layer and a heat dissipation support layer;

[0028] (2) The thickness of the auxiliary layer is 0.1 nm - 100 nm, and the light transmittance is more than 10%.

[0029] In one embodiment, the auxiliary layer includes a conductive support layer, and the conductive support layer is electrically connected to the conductive connection layer.

[0030] In one embodiment, the auxiliary layer includes a conductive support layer, the material of the conductive support layer includes a conductive metal, the laser wavelength in the optical fiber is 200 nm to 10 μm, the pulse power is 1 nw to 1 w, and the repetition frequency is 0 Hz to 10 GHz.

[0031] In one embodiment, along the extending direction of the core, the size of the tip portion is L1, and the size of the electron excitation layer is L2,

[0032] wherein, L1 is greater than L2.

[0033] In one embodiment, the size of the tip portion and the size of the electron excitation layer satisfy the following relationship:

[0034] L2 > 1 / 2 * L1.

[0035] According to the second aspect of the present application, a method for preparing an electron source is provided, including:

[0036] Providing an optical fiber; wherein, a tip portion is provided at the light-emitting end of the optical fiber;

[0037] Forming an electron emission layer on the tip portion of the optical fiber; wherein, the electron emission layer at least includes an electron excitation layer, and the electron excitation layer covers the surface of the tip portion of the optical fiber;

[0038] wherein, the optical fiber includes a core for transmitting laser, and the laser emitted from the core can directly irradiate on the electron emission layer, so that the electron excitation layer is excited by the laser emitted from the core and emits electrons;

[0039] The electron excitation layer includes at least one of a zero-dimensional material, a one-dimensional material, and a two-dimensional material.

[0040] In one embodiment, before or after forming the electron emission layer on the tip portion of the optical fiber, the method for preparing the electron source further includes:

[0041] A conductive connection layer is formed on the outer surface of the optical fiber so that the conductive connection layer overlaps with the electron excitation layer.

[0042] In one embodiment, the forming of the conductive connection layer on the outer surface of the optical fiber so that the conductive connection layer overlaps with the electron excitation layer specifically includes:

[0043] A core protection layer is formed on the tip of the optical fiber, wherein the core protection layer covers the projection of the core in a target plane perpendicular to the core extension direction within the target plane;

[0044] A conductive material layer covering the core protection layer is formed on the outer surface of the optical fiber;

[0045] The core protection layer and the part of the conductive material layer provided on the core protection layer are removed to form the conductive connection layer.

[0046] In one embodiment, the forming of the electron emission layer on the tip of the optical fiber specifically includes:

[0047] The electron excitation layer is formed on the tip of the optical fiber by means of dipping, direct growth or coating.

[0048] According to the third 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 any one of the above embodiments;

[0049] 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.

[0050] According to the fourth aspect of the present application, an application of the electron source according to any one of the above embodiments is provided. The application of the electron source includes at least one of an electron microscope, an electron beam lithography machine, a free electron laser, an X-ray tube, an electron accelerator, an electron diffraction device and a display.

[0051] In the technical solution of this application, when the electron source is in use, the laser transmitted in the core of the optical fiber can be transmitted toward the light-emitting end of the optical fiber. Since the light-emitting end is provided with a pointed end portion, the electron excitation layer covers the surface of the pointed end portion of the optical fiber, and the electron excitation layer is located on the light-emitting path of the core. Therefore, during the process that the laser transmitted in the core of the optical fiber is transmitted to the pointed end portion and emitted, this part of the laser can interact with the electron excitation layer, so that the electrons in the electron excitation layer absorb the photons of the laser and undergo energy transition to escape outside the electron excitation layer, thereby realizing the excitation of electrons. This application uses low-dimensional materials such as zero-dimensional materials, one-dimensional materials or two-dimensional materials as the materials of the electron excitation layer. The low-dimensional materials have an atomic-level thickness, and the back-incident electrons can be emitted without passing through in-body transmission, and the electron emission efficiency is high; moreover, the low-dimensional materials have no dangling bonds, are stable in nature and have a high melting point, are not easily damaged, and can be applied to the scenario of high-power excitation, and have characteristics such as good stability and long service life; in addition, the low-dimensional materials also have a high optical nonlinear effect and a rich electron bandgap, enabling the laser to better interact with the electron excitation layer to generate energy resonance and excite the electrons in the electron excitation layer. These electrons are excited and detached into the vacuum, and an electron beam can be formed, and the electron beam tunneling and emitting from the electron excitation layer has the characteristics of concentrated energy and small energy dispersion. In addition, the low-dimensional materials and the optical fiber can be directly integrated. The optical fiber transmits the laser and serves as the carrier of the low-dimensional materials, and can provide a stable excitation source with adjustable wavelength, polarization and optical mode, can be applied to different application scenarios, and does not require a complex optical path, and has characteristics such as small volume and high integration degree. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 FIG. shows a schematic structural diagram of an electron source according to an embodiment of this application.

[0053] Figure 2 FIG. shows Figure 1 an enlarged schematic diagram of part A of

[0054] Figure 3 FIG. shows a circuit block diagram of an electron source and an anode according to an embodiment of this application.

[0055] Figure 4 FIG. shows a schematic structural diagram of an electron source according to another embodiment of this application.

[0056] Figure 5 FIG. shows Figure 4 an enlarged schematic diagram of part B of

[0057] Figure 6 FIG. shows a schematic flow diagram of a preparation method of an electron source according to an embodiment of this application.

[0058] Figure 7 FIG. shows a schematic structural diagram of an electron gun according to an embodiment of this application.

[0059] Reference Signs:

[0060] 10. Electron gun;

[0061] 100. Electron source;

[0062] 110. Optical fiber; 111. Core; 112. Cladding layer;

[0063] 1101. Light incident end; 1102. Light exit end; j. Tip; j1. Surface;

[0064] 120. Electron emission layer; 121. Electron excitation layer; 1211. First part; 1212. Second part; 122. Auxiliary layer;

[0065] 130. Conductive connection layer; 131. First conductive part; 132. Second conductive part;

[0066] 200. Gate; 210. Second electron channel;

[0067] 300. Anode; 310. First electron channel. Detailed Embodiments

[0068] In order to make the above objects, features, and advantages of the present application more obvious and understandable, the following will describe in detail the specific embodiments of the present application with reference to the accompanying drawings. 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.

[0069] In the description of the present application, it should be understood that if terms such as "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. appear, the orientation or positional relationship indicated by these terms is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present application.

[0070] In addition, if the terms "first" and "second" appear, these terms are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In the description of this application, if the term "plurality" appears, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0071] In this application, unless otherwise clearly specified and defined, if terms such as "installed", "connected", "joined", "fixed", etc. appear, these terms 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 communication inside two elements or the interaction relationship between two elements, unless otherwise clearly defined. 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.

[0072] In this application, unless otherwise clearly specified and defined, if there is a description such as a first feature being "on" or "under" a second feature, the meaning can be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "over", and "on top of" the second feature can mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is at a higher horizontal level than the second feature. The first feature being "under", "beneath", and "underneath" the second feature can be that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is at a lower horizontal level than the second feature.

[0073] It should be noted that if an element is referred to as "fixed to" or "disposed on" another element, it can be directly on the other element or there may also be an intermediate element. If an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. If so, the terms "vertical", "horizontal", "up", "down", "left", "right" and similar expressions used in this application are only for the purpose of illustration and do not represent the only implementation.

[0074] In traditional technologies, tungsten filaments, lanthanum hexaboride and other materials with metallic properties are mainly selected as thermionic electron sources. When heated to thousands of degrees Celsius, electrons are thermally excited to escape from the material surface to form vacuum electrons. Field emission electron sources mainly select metal tips such as tungsten. Under the action of a strong external electric field, the tip discharge effect occurs. Among them, the electron beam emitted by the thermionic electron source can work in a relatively poor vacuum environment, has good environmental adaptability and stability, but has a low brightness and poor coherence. The electron beam of the field emission electron source has a high brightness and good coherence, but has high requirements for vacuum degree and is very sensitive to vibrations. 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 the emission efficiency and stability.

[0075] In traditional technologies, for photoemission electron sources, metal materials such as Au are used as the materials for the electron emission layer, with a thickness of more than 50 nm, and even reaching hundreds of nanometers. However, the inventors of the present application have found through research that the electron emission layer of the metal material has a relatively large thickness, and the distance between the bottom layer directly interacting with the laser and the surface layer for electron emission is relatively far (50 nm to hundreds of nanometers). During the process of electrons excited from the bottom layer passing through the electron emission layer, they are easily affected by metal lattice scattering, thereby affecting the emission efficiency. Moreover, metal materials are prone to damage under high-power laser irradiation, which affects the service life of the electron emission layer, and thus affects the electron emission efficiency and stability.

[0076] In traditional technologies, there is also a type of photoemission electron source that excites electrons by the external laser incident on the surface of a metal tip. The size of the metal tip is in the nanometer range, resulting in a relatively high difficulty in aligning the laser spot to the metal tip. If a high-magnification microscope is set up to align the external laser to the metal tip, it will lead to an increase in the overall cost, and the system is sensitive to vibrations and the electron emission beam current is unstable.

[0077] In addition, in traditional technologies, graphene is used as a saturable absorber. Graphene has broadband saturable absorption characteristics and a fast recovery time, and is used in the Q-switching and mode-locking of lasers, or the laser spectrum is adjusted by graphene to achieve sensing detection. However, there are obvious differences between graphene laser regulation and graphene electron emission. Graphene electron emission is based on the photoelectric effect, while graphene laser regulation is based on the principle of light absorption. The described graphene saturable absorber mainly utilizes the situation where the light absorption rate (or transmittance) of graphene increases (or decreases) with the increase in the incident light power and finally reaches the saturation threshold. It is mainly applied in lasers to generate laser pulses. For example, in the ring fiber resonator of a fiber laser, when the light power passing through the graphene saturable absorber exceeds its saturation absorption threshold during the circulation of light in the resonator, due to the saturable absorption effect, the light intensity in the cavity will instantaneously drop below the saturation absorption threshold, and this part of the dropped light energy is output in the form of pulses from the beam splitter of the cavity.

[0078] Based on this, it is necessary to provide an electron source that can balance electron emission efficiency and stability.

[0079] This application uses low-dimensional materials such as zero-dimensional materials, one-dimensional materials, or two-dimensional materials as the materials for the electron excitation layer. The low-dimensional materials generate electrons through the photoelectric effect under laser irradiation. The low-dimensional materials have atomic-level thickness, no dangling bonds, and stable properties, thus having characteristics such as good stability and high service life. Moreover, the low-dimensional materials can be directly integrated with the optical fiber, and the optical fiber can provide a stable excitation source with adjustable wavelength, polarization, and optical mode, and can be applied to different application scenarios.

[0080] Figure 1 The schematic structural diagram of the electron source 100 in an embodiment of this application is shown.

[0081] Please refer to Figure 1 and, in combination with referring to Figure 2 According to the first aspect of this application, an electron source 100 is provided, which includes an optical fiber 110 and an electron emission layer 120.

[0082] The optical fiber 110 includes a core 111 for transmitting laser light and a cladding layer 112 wrapped around the core 111. The refractive index of the cladding layer 112 is lower than that of the core 111. Therefore, the laser light can be confined within the core 111 by the cladding layer 112 for propagation. A coating layer is also provided on the outer surface of the cladding layer 112 for protecting the cladding layer 112 and the core 111.

[0083] The optical fiber 110 has an incident end 1101 and an output end 1102. The incident end 1101 is used to couple to a laser source so that the laser light emitted by the laser source can be transmitted through the core 111 of the optical fiber 110. Among them, the laser source can be a laser. The optical fiber 110 is a transmission medium for laser light and a carrier for low-dimensional materials. The optical fiber 110 can be a single-mode optical fiber, a multi-mode optical fiber, a polarization-maintaining optical fiber, or a multi-core optical fiber, etc.

[0084] The output end 1102 of the optical fiber 110 is provided with a pointed end j. The electron emission layer 120 at least includes an electron excitation layer 121. The electron excitation layer 121 covers the surface j1 of the pointed end j of the optical fiber 110. The laser light emitted from the core 111 can directly irradiate the electron emission layer 120, so that the electron excitation layer 121 is excited by the laser light emitted from the core 111 and emits electrons. That is to say, the electron excitation layer 121 is located on the light output path of the core 111 so that the electron excitation layer 121 can receive the laser light emitted from the core 111. Among them, the electron excitation layer 121 includes at least one of zero-dimensional materials, one-dimensional materials, and two-dimensional materials.

[0085] The electron excitation layer 121 can directly cover the surface j1 of the tip j of the optical fiber 110, or can indirectly cover the surface j1 of the tip j of the optical fiber 110, and no specific limitation is made here.

[0086] The electron excitation layer 121 can include zero-dimensional materials. Zero-dimensional materials refer to materials whose dimensions in the three spatial dimensional directions are at the nanoscale, such as nanoparticles, atomic clusters, and quantum dots, etc., which are generally composed of a small number of atoms and molecules. There are many zero-dimensional carbon nanomaterials, such as carbon black, nanodiamond, diamond color center, nanometer fullerene C 60 or carbon-coated nanometal particles, etc. Zero-dimensional materials have typical discrete energy levels. Under the action of laser excitation, electrons are mainly tunneling-excited from the discrete energy levels, so that the electron beam tunneling-emitted from the electron excitation layer 121 has the characteristics of energy concentration and small energy dispersion.

[0087] The electron excitation layer 121 can also include one-dimensional materials. The electrons in one-dimensional materials can be transmitted along the linear chain of the one-dimensional materials. Combined with the electron excitation layer 121 covering the surface j1 of the tip j of the optical fiber 110, it is beneficial for the electrons emitted by the electron source 100 to be emitted efficiently along the extension direction of the optical fiber 110. One-dimensional materials have the characteristics of a small radius of curvature (nanoscale), can enhance the interaction between light and matter and provide a large field enhancement factor, ensure multi-photon emission, light field emission, etc., and are applied to scenarios requiring a high-brightness electron source.

[0088] One-dimensional materials can be nanotubes, nanorods or nanowires, nanoribbons or coaxial nanocables, etc.

[0089] The nanotube can be a carbon nanotube. A carbon nanotube can be regarded as a seamless tubular structure formed by winding single-layer or multi-layer graphite according to certain rules. The nanotube can also be a silicon (Si) nanotube, a selenium (Se) nanotube, a tellurium (Te) nanotube, a bismuth (Bi) nanotube, a boron nitride (BN) nanotube, a boron-nitrogen co-doped carbon nanotube (BCN nanotube), a tungsten disulfide (WS2) nanotube, a molybdenum disulfide (MoS2) nanotube or a titanium dioxide (TiO2) nanotube, etc.

[0090] The material of the nanowire can be silicon (Si) or germanium (Ge); the nanowire can also be an oxide nanowire, such as tin oxide (SnO) or zinc oxide (ZnO), etc.; of course, the nanowire can also be a nitride nanowire, such as gallium nitride (GaN) or silicon nitride (Si3N4), etc.; the nanowire can also be a sulfide nanowire, such as cadmium sulfide (CdS) and zinc sulfide (ZnS), etc.; the nanowire can also be a ternary compound nanowire, such as barium titanate (BaTiO3) and lead titanate (PbTiO3), etc.

[0091] Nanoribbons are quite different from the above two nanostructures (nanotubes and nanowires). Their cross-sections are not nearly circular like those of nanotubes or nanowires, but rather quadrilateral, and the aspect ratio generally ranges from a few to more than a dozen. The material of the nanoribbons can be an oxide, such as tin oxide (SnO) or zinc oxide (ZnO), etc.

[0092] The nanocoaxial cable can be a graphite / boron nitride (C / BN) nanocoaxial cable or a silicon carbide / silicon dioxide (CSi / SiO2) nanocoaxial cable, etc.

[0093] The electron excitation layer 121 can also include two-dimensional materials. The electrons in the two-dimensional materials can be transmitted along the two-dimensional plane. Combining with the fact that the electron excitation layer 121 covers the surface j1 of the tip portion j of the optical fiber 110, in this way, it is beneficial for the electrons emitted by the electron source 100 to be efficiently emitted along the extension direction of the optical fiber 110; and compared with setting a thin metal layer on the optical fiber, it will cause the melting point of the metal layer to decrease, and then lead to the problem that the metal layer is easily damaged. The two-dimensional material selected in this application has no dangling bonds, is relatively stable, has a high melting point, is not easily damaged, and is suitable for high-power excitation and high-beam-current electron sources 100. In addition, the energy levels of the two-dimensional materials are more discrete, and the energy of the electron beam emitted by tunneling is more concentrated and the energy dispersion is smaller.

[0094] The two-dimensional materials have the characteristic of atomic layer thickness. The thickness of the two-dimensional materials can be the thickness of a single atomic layer or the thickness of multiple atomic layers. During the interaction between the laser and the two-dimensional materials, it hardly affects the optical transmission mode, and has high stability; moreover, the excited electrons can be directly emitted without scattering inside the material, ensuring the purity of the properties of the emitted electrons and an extremely narrow pulse width.

[0095] The two-dimensional materials can be graphene, transition metal sulfides, two-dimensional perovskites, two-dimensional diamonds or boron nitride, etc.

[0096] Taking the two-dimensional material selected as graphene as an example for illustration, the carbon atoms in graphene are bonded in the plane in the form of covalent bonds to form a hexagonal honeycomb planar structure. The electron excitation layer 121 can have an atomic thickness of about 0.34 nanometers; the electron excitation layer 121 can also have several or dozens of atomic thicknesses.

[0097] Of course, this application is not limited to this. The electron excitation layer 121 also includes two or more of zero-dimensional materials, one-dimensional materials and two-dimensional materials.

[0098] Thus, when the electron source 100 is in use, the laser transmitted in the core 111 of the optical fiber 110 can be transmitted toward the light-emitting end 1102 of the optical fiber 110. Since the light-emitting end 1102 is provided with a pointed end portion j, the electron excitation layer 121 covers the surface j1 of the pointed end portion j of the optical fiber 100, and the electron excitation layer 121 is located on the light-emitting path of the core 111. Therefore, during the process that the laser transmitted in the core 111 of the optical fiber 110 is transmitted to the pointed end portion j and then emitted, this part of the laser can interact with the electron excitation layer 121, so that the electrons in the electron excitation layer 121 absorb the photons of the laser, and undergo energy transition and escape outside the electron excitation layer 121, thereby realizing the excitation of electrons. The laser can be transmitted along the core 111 of the optical fiber 110, so that the laser transmitted in the core 111 can be propagated to the light-emitting end 1102 and emitted, and interact with the electron excitation layer 121, so that the electrons in the electron excitation layer 121 absorb the photons of the laser, and undergo energy transition and escape outside the electron excitation layer 121, realizing the excitation of electrons. The electron source 100 uses low-dimensional materials such as zero-dimensional materials, one-dimensional materials or two-dimensional materials as the material of the electron excitation layer 121, and the electron excitation layer 121 is arranged on the optical fiber 110 to realize the excitation of electrons, abandoning the complex spatial light coupling structure set due to the introduction of external lasers, and also abandoning the high-magnification microscope set to solve the alignment problem of metal tips, which can reduce the process cost of the electron gun and increase the stability.

[0099] Compared with setting a metal layer on the optical fiber tip and directly interacting the laser transmitted in the optical fiber with the metal layer to excite electrons (the electrons are easily affected by lattice scattering during the process of passing through the metal layer, resulting in a low electron emission efficiency. In addition, the conduction band of the metal material is a half-filled band, resulting in a wide energy distribution of the electrons emitted by the excited metal layer), this application uses low-dimensional materials such as zero-dimensional materials, one-dimensional materials or two-dimensional materials as the material of the electron excitation layer 121. The low-dimensional materials have an atomic-level thickness, and the back-incident electrons can be emitted without passing through in-body transmission, with a high electron emission efficiency; moreover, the low-dimensional materials have no dangling bonds, are stable in nature and have a high melting point, are not easily damaged, can be applied to the scenario of high-power excitation, and have characteristics such as good stability and high service life; in addition, the low-dimensional materials also have a high optical nonlinear effect and a rich electron bandgap, enabling the laser to better interact with the electron excitation layer 121 to generate energy resonance, and excite the electrons in the electron excitation layer 121. These electrons are excited and detached into the vacuum, and can form an electron beam, and the electron beam tunneling and emitting from the electron excitation layer 121 has the characteristics of concentrated energy and small energy dispersion.

[0100] In addition, low-dimensional materials can be directly integrated with the optical fiber 110. The optical fiber transmits laser light and serves as a carrier for the low-dimensional materials, capable of providing a stable excitation source with adjustable wavelength, polarization, and optical mode. It can be applied to different application scenarios without the need to provide a complex optical path, and has the characteristics of small volume and high integration.

[0101] Optionally, along the extending direction of the core 111, the radial dimension of the tip portion j gradually decreases.

[0102] The electron excitation layer 121 of the present application is disposed on the tip portion j of the optical fiber 110 and covers the surface j1 of the tip portion j of the optical fiber 110. Since the tip portion j of the optical fiber 110 has a geometric structure similar to a needle tip, the field emission enhancement factor is increased, and an electron source 100 with higher brightness can be obtained.

[0103] It should be noted that the wavelength of the laser can be the wavelength at which electrons in the electron excitation layer 121 absorb a photon and transition, for example, the wavelength is in the visible light-near infrared-ultraviolet range. The wavelength of the laser can also be the wavelength at which electrons in the electron excitation layer 121 absorb multiple photons and transition, for example, the wavelength is outside the visible light-near infrared-ultraviolet range, and no specific limitation is made here.

[0104] In some embodiments, the thickness of the electron excitation layer 121 is less than or equal to 50 nm.

[0105] It can be understood that the thickness of the electron excitation layer 121 is in the nanometer order and the thickness of the electron excitation layer 121 is small. Thus, it is more beneficial to reduce the process of in-body transmission of the excited electrons in the electron excitation layer 121, more beneficial to improve the electron emission efficiency and emission power, and then an electron beam with ultra-short pulses can be realized by using the electron source 100.

[0106] In some embodiments, the angle between the axial direction of the one-dimensional material in the electron excitation layer 121 and the emission direction of the emitted laser is 0 to 90°, for example, it can be 0°, 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80°, or 90°.

[0107] In some embodiments, the axial direction of the one-dimensional material is the same as the emission direction of the laser, so that point emission of the electron source 100 can be achieved and the resolution is high. If a low-density arrangement of one-dimensional materials is adopted, the energy dispersion of the emitted electrons is low and the brightness is high. If a high-density arrangement of one-dimensional materials is adopted, a large beam current of the electron source can be achieved. Among them, low density refers to the number of one-dimensional materials per unit area. For example, a density less than 1 / nm 2 is low density, and greater than 1 / nm 2 is high density.

[0108] In some embodiments, the axis of the one-dimensional material forms an angle with the emission direction of the laser, and the angle can be a right angle or an acute angle. Laser excitation of the one-dimensional material can generate a linear electron source.

[0109] In some embodiments, the electron excitation layer 121 includes at least one layer of two-dimensional material.

[0110] Optionally, the electron excitation layer 121 includes at least two layers of two-dimensional materials stacked in sequence along the laser emission direction, or the electron excitation layer 121 includes at least two two-dimensional materials with different materials connected to each other on the same plane.

[0111] In some embodiments, at least two layers of two-dimensional materials are stacked, or the electron excitation layer 121 includes at least two two-dimensional materials with different materials connected to each other on the same plane, thereby forming a vertical heterojunction or a planar heterojunction. The heterojunction structure can enhance the interaction between light and the two-dimensional material, achieve efficient electron emission under the laser power, and the heterojunction has the function of interfacial energy band regulation. Through material design and twist angle regulation, special interfacial states can be obtained to achieve high-brightness and low-energy-dispersion electron emission.

[0112] In some embodiments, the material in the electron excitation layer 121 includes a one-dimensional material and a zero-dimensional material disposed at the end and / or side of the one-dimensional material.

[0113] In this application, by combining the zero-dimensional material with the one-dimensional material and disposing the zero-dimensional material at the end and / or side of the one-dimensional material, that is, using the zero-dimensional material to modify the surface structure of the one-dimensional material. Both the zero-dimensional material and the one-dimensional material have typical discrete energy levels. Under the action of the laser, electrons are mainly excited by tunneling from the discrete energy levels, and the emitted electrons have the characteristics of concentrated energy, small energy dispersion, and high emission efficiency.

[0114] In some embodiments, the electron excitation layer 121 includes a zero-dimensional material and a two-dimensional material, and the zero-dimensional material is disposed on the surface of the two-dimensional material.

[0115] In this application, the zero-dimensional material is disposed on the surface of the two-dimensional material. The two-dimensional material can not only serve as a support layer for carrying the zero-dimensional material, but also avoid the addition of the following conductive connection layer 130 by using a conductive two-dimensional material, that is, the two-dimensional material can serve as an auxiliary layer for the zero-dimensional material to achieve the functions of support and conduction.

[0116] In some embodiments, the electron excitation layer 121 includes a one-dimensional material and a two-dimensional material, and the one-dimensional material is disposed on the surface of the two-dimensional material; optionally, the angle between the axis of the one-dimensional material and the surface of the two-dimensional material is 0 to 90°.

[0117] In the present application, a one-dimensional material is disposed on the surface of a two-dimensional material. The two-dimensional material can not only serve as a support layer for carrying the one-dimensional material, but also avoid the addition of the following conductive connection layer 130 by using a conductive two-dimensional material, that is, the two-dimensional material can serve as an auxiliary layer for the one-dimensional material to achieve the functions of support and conduction.

[0118] In some embodiments, the zero-dimensional material, one-dimensional material or two-dimensional material independently includes a doping element.

[0119] In the present application, by doping elements into the low-dimensional material, the conductivity of the low-dimensional material is improved, the work function is changed, and the electron emission performance is adjusted. For example, alkali metal and alkaline earth metal elements can improve the conductivity of the low-dimensional material, and at the same time can reduce the work function of the low-dimensional material to enhance the emission beam current. Elements such as B, C, N, O, F, and rare earths can create discrete energy levels to obtain an electron beam with a narrow energy.

[0120] Optionally, the doping element includes at least one of alkali metals, alkaline earth metals, transition metals, rare earth elements, halogen elements, and light elements (B, C, N, O, F).

[0121] In some embodiments, the electron source 100 further includes a conductive connection layer 130, and the conductive connection layer 130 is at least disposed on the outer surface of the optical fiber 110 and is electrically connected to the electron excitation layer 121.

[0122] Specifically, the outer surface of the optical fiber 110 includes the circumferential side surface of the optical fiber 100 and the surface j1 of the tip end portion j of the optical fiber 100.

[0123] The conductive connection layer 130 can be a conductive thin film. Specifically, the conductive connection layer 130 can be a metal thin film, a graphite thin film, or a low-dimensional material thin film, etc.

[0124] It should be added that the projection of the conductive connection layer 130 in the target plane perpendicular to the extending direction of the fiber core 111 is staggered from the projection of the fiber core 111 in the target plane, that is, the conductive connection layer 130 is not disposed on the light exit path of the laser emitted from the fiber core 111.

[0125] In this way, the electron excitation layer 121 can be electrically connected to the negative electrode of the power supply through the conductive connection layer 130. On the one hand, the power supply can be used to supplement electrons to the electron excitation layer 121, which is beneficial for the electron excitation layer 121 to continuously emit electrons under the excitation of the laser. On the other hand, the direction and convergence of the electrons emitted from the electron excitation layer 121 can be regulated by the voltage applied to the conductive connection layer 130 by the power supply.

[0126] Exemplarily, such as Figure 3As shown, an electron source 100 is applied to an electron gun 10, and the electron gun 10 further includes an anode 300. The anode 300 has a first electron channel 310 for allowing electrons emitted from the electron excitation layer 121 to pass through. A preset voltage is provided between the anode 300 and the conductive connection layer 130, so as to form a preset electric field between the anode 300 and the conductive connection layer 130. As a result, the electrons emitted from the electron excitation layer 121 are emitted towards the first electron channel 310 of the anode 300 under the drive of the preset electric field and pass through the first electron channel 310. Specifically, the electron excitation layer 121 is electrically connected to the negative electrode of the power supply through the conductive connection layer 130, and the anode 300 is electrically connected to the positive electrode of the power supply, so that a preset voltage is provided between the anode 300 and the conductive connection layer 130, and the electron excitation layer 121 and the anode 300 are arranged at intervals along the extending direction of the optical fiber 110. In this way, it is beneficial to form a uniform electric field along the extending direction of the optical fiber 110 by using the anode 300, which is more conducive to the linear acceleration of electrons along the extending direction of the optical fiber 110 and passing through the first electron channel 310.

[0127] In some embodiments, the electron excitation layer 121 includes a first part 1211. The projection of the first part 1211 in a target plane perpendicular to the extending direction of the core 111 covers the projection of the core 111 in the target plane, and the first part 1211 is electrically connected to the conductive connection layer 130.

[0128] It may be that the first part 1211 is directly electrically connected to the conductive connection layer 130, or it may be that the first part 1211 is indirectly electrically connected to the conductive connection layer 130. No specific limitation is made here.

[0129] In this way, the first part 1211 of the electron excitation layer 121 can be located on the light-emitting path of the core 111, so that the electron excitation layer 121 can receive the laser emitted from the core 111 and then emit electrons outward under the excitation of the laser.

[0130] In this embodiment, the electron excitation layer 121 further includes a second part 1212 connected to the first part 1211. The projection of the second part 1212 in the target plane is located on the periphery of the projection of the first part 1211 in the target plane, and the second part 1212 overlaps with the conductive connection layer 130.

[0131] In this way, by electrically connecting the conductive connection layer 130 to the second part 1212 of the electron excitation layer 121, and considering that the projection of the second part 1212 in the target plane is located on the periphery of the projection of the first part 1211 in the target plane, the conductive connection layer 130 can supplement electrons to the electron excitation layer 121 without affecting the interaction between the core 111 and the electron excitation layer 121, which is beneficial to the continuous outward emission of electrons from the electron excitation layer 121 under the excitation of the laser.

[0132] In some embodiments, the conductive connection layer 130 includes a first conductive portion 131 provided at the tip end j of the optical fiber 110, and a second conductive portion 132 connected to the first conductive portion 131 and provided on the circumferential side surface of the optical fiber 110. The first conductive portion 131 overlaps with the second portion 1212 of the electron excitation layer 121.

[0133] In this way, the conductive connection layer 130 can cover more of the optical fiber 110, improving the bonding strength between the conductive connection layer 130 and the optical fiber, and also facilitating better use of the conductive connection layer 130 to supply electrons to the electron excitation layer 121.

[0134] In some embodiments, the conductive connection layer 130 includes a first metal layer and a second metal layer stacked thereon, and the adhesion of the first metal layer is greater than that of the second metal layer.

[0135] Exemplarily, the material of the first metal layer is titanium, and the material of the second metal layer is gold.

[0136] In this way, the first metal layer with higher adhesion can make the conductive connection layer 130 better adhere to the optical fiber 110, improving the bonding strength between the conductive connection layer 130 and the optical fiber 110, and also facilitating improving the service life of the conductive connection layer 130.

[0137] In some embodiments, the electron emission layer 120 further includes an auxiliary layer 122. The auxiliary layer 122 is stacked on one side of the surface j1 of the electron excitation layer 121 close to the tip end j, or the auxiliary layer 122 is stacked on one side of the surface j1 of the electron excitation layer 121 far from the tip end j. Figure 4 and Figure 5 An example is given where the auxiliary layer 122 is stacked on one side of the surface j1 of the electron excitation layer 121 close to the tip end j.

[0138] In this application, the auxiliary layer 122 is added. When the electron excitation layer 121 requires structural support, the auxiliary layer 122 is used to provide structural support for the electron excitation layer 121, that is, the electron excitation layer 121 is provided on the auxiliary layer 122; or, when the electron excitation layer 121 cannot be directly connected and conducted with the conductive connection layer 130, the conductive auxiliary layer 122 is used to connect with the conductive connection layer 130, and the auxiliary layer 122 is used to achieve electron conduction between the electron excitation layer 121 and the conductive connection layer 130.

[0139] Optionally, the auxiliary layer 122 includes at least one of a conductive support layer and a heat dissipation support layer.

[0140] Optionally, the thickness of the auxiliary layer 122 is 0.1 nm to 100 nm.

[0141] Optionally, the light transmittance of the auxiliary layer 122 is 10% or more, such as 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or 100%.

[0142] Optionally, the auxiliary layer 122 includes a conductive support layer, and the conductive support layer is electrically connected to the conductive connection layer 130.

[0143] In some embodiments, the auxiliary layer 122 includes a conductive support layer, the material of the conductive support layer includes a conductive metal, the laser wavelength in the optical fiber 110 is 200 nm to 10 μm, the pulse power is 1 nw to 1 w, and the repetition frequency is 0 Hz to 10 GHz.

[0144] In this application, the auxiliary layer 122 uses a conductive metal and controls the laser parameters, thereby avoiding the problem of melting caused by laser irradiation of the conductive metal and ensuring that the auxiliary layer has the functions of support and conduction.

[0145] The auxiliary layer 122 may also include a conductive support layer. The electron excitation layer 121 is disposed on the surface j1 of the tip j through the auxiliary layer 122, and the auxiliary layer 122 has a bearing plane for bearing the electron excitation layer 121. The auxiliary layer 122 can be a light-transmitting material; the auxiliary layer 122 can also be a non-light-transmitting material. For example, the auxiliary layer 122 is a non-light-transmitting material and does not have conductivity. In this way, the auxiliary layer 122 can be set in an annular structure, and the projection of the auxiliary layer 122 in the target plane is located outside the projection of the core 111 of the optical fiber 110 in the target plane.

[0146] In this way, not only can the bearing plane of the auxiliary layer 122 be used to make the electron excitation layer 121 more flatly disposed on the surface j1 of the tip j, but also the interaction between the electron excitation layer 121 and the core 111 of the optical fiber 110 is not affected, which is beneficial to the formation of an electron beam with concentrated energy and small energy dispersion from the electrons tunneling and emitting within the electron excitation layer 121.

[0147] The auxiliary layer 122 may also include a heat dissipation support layer. Exemplarily, the material of the auxiliary layer 122 may be hexagonal boron nitride. Of course, the material of the auxiliary layer 122 may also be other materials that can dissipate heat from the electron excitation layer 121 and enable the electron excitation layer 121 to be flatly disposed on the surface j1 of the tip j. In this way, the heat dissipation efficiency of the electron excitation layer 121 can be increased by using the auxiliary layer 122, so that the electron excitation layer 121 can emit a larger electron beam current.

[0148] In some embodiments, along the extension direction of the core 111, the size of the tip j is L1, and the size of the electron excitation layer 121 is L2, where L1 is greater than L2. Specifically, the size of the tip j and the size of the electron excitation layer 121 satisfy the following relationship: L2 > 1 / 2 * L1.

[0149] The electron excitation layer 121 covers the surface j1 of the tip portion j, and the electron excitation layer 121 is disposed around the tip portion j. Since L2 > 1 / 2 * L1, in this way, the contact area between the electron excitation layer 121 and the surface j1 of the tip portion j can be increased, the bonding strength between the electron excitation layer 121 and the optical fiber 110 can be improved, and it is also beneficial to use the laser transmitted by the core 111 to excite the electron excitation layer 121 to emit electrons outward.

[0150] Please refer to Figure 6 , according to the second aspect of the present application, a method for preparing an electron source 100 is provided, including the following steps:

[0151] S210. Provide an optical fiber 110. Among them, the light output end 1102 of the optical fiber 110 is provided with a tip portion j.

[0152] Optionally, two optical fibers (at least 40 cm long) can be respectively used with a Miller pliers to strip the coating layer near the end by about 4 cm, leaving the cladding layer 112 (made of quartz) and the core 111, and wiping off the remaining organic substances and impurities with alcohol. Then, use an optical fiber cutter to cut one end of the stripped coating layer to obtain two optical fibers with clean and flat light output ends. After fusing the end faces of the light output ends of the two optical fibers with a fusion splicer, displace the optical fiber axially under the control of the fusion splicer, align the arc area of the fusion splicer with the area 1 cm away from the fusion joint, and then use an appropriate arc power and axial tensile stress to taper the optical fiber in the molten state until it breaks. Finally, two optical fibers 110 with a tip portion j (similar to a needle tip structure) can be obtained.

[0153] S220. Form an electron emission layer 120 on the tip portion j of the optical fiber 110. Among them, the electron emission layer 120 at least includes an electron excitation layer 121, and the electron excitation layer 121 covers the surface j1 of the tip portion j. Among them, the optical fiber 110 includes a core 111 for transmitting laser, and the laser emitted by the core 111 can directly irradiate on the electron emission layer 120, so that the electron excitation layer 121 is excited by the laser emitted by the core 111 and emits electrons. That is to say, the electron excitation layer 121 is located on the light output path of the core 111, so that the electron excitation layer 121 can receive the laser emitted by the core 111, and the electron excitation layer 121 includes at least one of zero-dimensional materials, one-dimensional materials, and two-dimensional materials.

[0154] Optionally, forming the electron emission layer 120 on the tip portion j of the optical fiber 110 specifically includes:

[0155] Form the electron excitation layer 121 on the tip portion j of the optical fiber 110 by means of dipping, direct growth, or coating.

[0156] In some embodiments, the electron excitation layer 121 is formed on the tip portion j of the optical fiber 110 by dipping, which specifically includes: directly preparing zero-dimensional materials, one-dimensional materials or two-dimensional materials in a solution and floating them on the liquid surface, bringing the tip portion j of the optical fiber 110 into contact with the zero-dimensional materials, one-dimensional materials or two-dimensional materials on the liquid surface, and drying the zero-dimensional materials, one-dimensional materials and / or two-dimensional materials on the tip portion j of the optical fiber 110.

[0157] In other embodiments, the electron excitation layer 121 is prepared by a direct growth method, and the preparation method includes: directly preparing the electron excitation layer 121 on the tip portion j of the optical fiber 110 by at least one of chemical vapor deposition, physical vapor deposition, molecular beam epitaxy and liquid filling.

[0158] In still other embodiments, the electron excitation layer 121 can be formed on the tip portion j of the optical fiber 110 by coating.

[0159] Optionally, before or after forming the electron emission layer 120 on the tip portion j of the optical fiber 110, the preparation method of the electron source 100 further includes:

[0160] S230. Form a conductive connection layer 130 on the outer surface of the optical fiber 110 so that the conductive connection layer 130 overlaps with the electron excitation layer 121.

[0161] That is to say, the conductive connection layer 130 can be formed first and then the electron excitation layer 121; or the electron excitation layer 121 can be formed first and then the conductive connection layer 130; as long as the electron excitation layer 121 and the conductive connection layer 130 are electrically connected to each other, in this way, electrons can be supplied to the electron excitation layer 121 by means of the conductive connection layer 130, which is beneficial to the continuous emission of electrons from the electron excitation layer 121 under the excitation of laser.

[0162] Optionally, forming a conductive connection layer 130 on the outer surface of the optical fiber 110 so that the conductive connection layer 130 overlaps with the electron excitation layer 121 specifically includes:

[0163] S231. Form a core protection layer on the tip portion j of the optical fiber 110, and the projection of the core protection layer in the target plane perpendicular to the extension direction of the core 111 covers the projection of the core 111 in the target plane.

[0164] Optionally, the polymer microsphere solution can be coated on the surface j1 of the tip portion j of the optical fiber 110 to form the above-mentioned core protection layer. Exemplarily, the polymer microsphere solution is a polymethyl methacrylate suspension.

[0165] S232. Form a conductive material layer covering the core protection layer on the outer surface of the optical fiber 110.

[0166] The conductive material layer can be formed by vapor deposition. Specifically, a metal vapor deposition device can be used to form the conductive material layer on the outer surface of the optical fiber 110.

[0167] S233. Remove the core protective layer and the part of the conductive material layer disposed on the core protective layer to form the conductive connection layer 130.

[0168] Optionally, a solvent that can dissolve the core protective layer and does not interact with the conductive material layer can be used to remove the core protective layer. Specifically, the tip end j of the optical fiber 110 can be immersed in acetone, so that the core protective layer (polymer beads) is dissolved, and the part of the conductive material layer disposed on the core protective layer (part of the metal coating) flakes off to obtain the conductive connection layer 130.

[0169] It can be understood that the core protective layer can be used to stagger the projection of the conductive connection layer 130 in the target plane from the projection of the core 111 of the optical fiber 110 in the target plane, so that the laser transmitted in the core 111 of the optical fiber 110 can better interact with the electron excitation layer 121 disposed at the tip end j of the optical fiber 110.

[0170] Please refer to Figure 7 , according to the third aspect of the present application, an electron gun 10 is provided. The electron gun 10 includes a housing, a grid 200, an anode 300, and the electron source 100 of any one of the above embodiments.

[0171] The electron source 100 is fixed in the housing, and the grid 200 and the anode 300 are sequentially arranged on the electron emission side of the electron source 100.

[0172] It should be noted that in the present application, the grid 200 is used to limit the shape of the electron beam, and the anode 300 is used to accelerate the electrons. When electrons are excited and emitted from the electron source 100, they will interact with the electrostatic field established by the grid 200 and the space charge of the electrons themselves to form an electron beam with a certain shape, pass through the second electron channel 210 of the grid 200, and be emitted through the first electron channel 310 of the anode 300 for use.

[0173] According to the fourth aspect of the present application, an application of the electron source 100 as in the first aspect is provided. The application of the electron source 100 includes at least one of an electron microscope, an electron beam exposure machine, a free electron laser, an X-ray tube, an electron accelerator, an electron diffraction device, and a display.

[0174] The embodiments of the present invention will be described in detail below in conjunction with examples. It should be understood that these examples are only used to illustrate the present invention and not to limit the scope of the present invention. For the experimental methods without specific conditions in the following examples, the guidance given in the present invention is preferably referred to, and it can also be carried out according to the experimental manuals or conventional conditions in the art, or according to the conditions recommended by the manufacturers, or by referring to the experimental methods known in the art.

[0175] Example 1

[0176] As Figure 1 - Figure 2 shown, the optical fiber 110 is a single-mode optical fiber. The diameter of the fiber core 111 is 8.2 microns, and the diameter of the optical fiber 110 is 125 microns. The tip end j of the optical fiber 110 is conical, and the diameter gradually decreases to 500 nanometers. The excitation wavelength transmitted in the optical fiber is 1550 nm. Graphene with 6 layers can be mechanically peeled off from graphene using tape. Taking 6-layer graphene as a graphene unit, multiple graphene units can be suspended on the liquid surface. Then, the light input end 1101 of the optical fiber 110 is clamped, and the tip end j of the optical fiber 110 is inserted downward below the above-mentioned liquid surface to dip the graphene units floating on the liquid surface. The dipping times are 3 times, so that an electron excitation layer 121, that is, 18-layer graphene, about 6.12 nm, is provided on the tip end j of the optical fiber 110. Then, the above-mentioned conductive connection layer 130 is formed on the outer surface of the optical fiber 110 to obtain the electron source 100.

[0177] Example 2

[0178] The optical fiber 110 is a single-mode optical fiber. The diameter of the fiber core 111 is 8.2 microns, and the diameter of the optical fiber 110 is 125 microns. The tip end j of the optical fiber 110 is conical, and the diameter gradually decreases to 500 nanometers. The excitation wavelength transmitted in the optical fiber is 1550 nm. It is also possible to grow 5-layer graphene on a copper substrate by chemical vapor deposition method, and etch the metallic copper of the substrate in an etching solution (such as ammonium persulfate solution) to obtain 5-layer graphene suspended on the liquid surface. In this way, taking 5-layer graphene as a graphene unit, multiple graphene units can be suspended on the liquid surface. Then, the light input end 1101 of the optical fiber 110 is clamped, and the tip end j of the optical fiber 110 is inserted downward below the above-mentioned liquid surface to dip the graphene units floating on the liquid surface. The dipping times are 2 times, so that 10-layer graphene, about 3.4 nm, is provided on the tip end j of the optical fiber 110. Then, the above-mentioned conductive connection layer 130 is formed on the outer surface of the optical fiber 110 to obtain the electron source 100.

[0179] Example 3

[0180] On the basis of Embodiment 1, a layer of CdSe quantum dots is coated on the surface of graphene to form a composite structure of graphene + quantum dots, thereby obtaining the electron excitation layer 121 of this embodiment. The interaction between quantum dots and light is very strong, which can improve the light response degree of the overall structure, increase the beam current, and enhance the brightness of the electron source. Secondly, the energy levels of quantum dots are concentrated, enabling electron emission with a narrow energy linewidth.

[0181] Embodiment 4

[0182] The optical fiber 110 is a single-mode optical fiber. The diameter of the fiber core 111 is 8.2 micrometers, and the diameter of the optical fiber 110 is 125 micrometers. The tip end j of the optical fiber 110 is conical, with the diameter gradually shrinking to 500 nanometers. The excitation wavelength transmitted in the optical fiber is 1550 nm. Please refer to Figure 4 and Figure 5 , an auxiliary layer 122 with a thickness of 1 nm and made of graphene is deposited on the tip end j of the optical fiber 110; then, a plurality of nanotubes are deposited on the auxiliary layer 122, and the axial direction of the nanotubes is parallel to the extension direction of the fiber core 111, thereby obtaining the electron excitation layer 121; finally, the above-mentioned conductive connection layer 130 is formed on the outer surface of the optical fiber 110 to obtain the electron source 100. Among them, the first conductive part 131 of the conductive connection layer 130 is arranged on the surface j1 of the tip end j of the optical fiber 110 and overlaps with the auxiliary layer 122, and the second conductive part 132 of the conductive connection layer 130 is arranged on the circumferential side surface of the optical fiber 110.

[0183] Comparative Example 1

[0184] An electron source is prepared according to the structure of Embodiment 1, except that the electron excitation layer 121 in Embodiment 1 is replaced with a gold layer with a thickness of 100 nm, and the gold layer is prepared by deposition.

[0185] Comparative Example 2

[0186] An electron source is prepared according to the structure of Comparative Example 1, except that the electron excitation layer 121 in Comparative Example 1 is replaced with a gold layer with a thickness of 6.12 nm.

[0187] As Figure 7 shown, the electron sources prepared by the above-mentioned embodiments and comparative examples are assembled into an electron gun. The electron gun further includes a housing, a grid 200, and an anode 300. Performance tests are carried out on the obtained electron gun, and the test results are as follows in the table:

[0188] Table 1

[0189]

[0190]

[0191] Among them, stability refers to when the excitation power of the electron source is 50% or more of the damage power and the vacuum degree is 2×10 -5 Pa, continuously emit current for 1 hour. After removing the bad points, the ratio of the difference between the maximum current and the minimum current to the average current is the stability, and the stability can reflect the working stability of the electron source. Lifetime refers to when the excitation power of the electron source is 50% or more of the damage power and the vacuum degree is 2×10 -5 Pa, continuously emit current until the current decays to less than 10% of the initial value, which is defined as the lifetime. The working vacuum degree refers to when the excitation power of the electron source is 50% or more of the damage power, continuously emit current. The vacuum degree gradually increases until the current shows a rapid decay (the rapid decay is defined as the current decaying by more than 50% within 1 minute). The vacuum degree at this time is defined as the working vacuum degree. It can be seen from the above table that: the electron source of the present application has good stability, a long lifetime, and a good working vacuum degree.

[0192] It is found through testing that compared with the lifetime of the electron source prepared by the comparative example, the lifetime of the electron source prepared by Examples 1-4 is higher; compared with the stability of the electron source prepared by the comparative example, the stability of the electron source prepared by Examples 1-4 is better.

[0193] In summary, low-dimensional materials such as zero-dimensional materials, one-dimensional materials, and two-dimensional materials in the present application have atomic-scale sizes. The back-incident electrons can be emitted into the vacuum without passing through in-body transmission, which is very suitable for ultrafast electron sources with narrow pulse widths; moreover, low-dimensional materials and different types of optical fibers can be directly integrated, bringing ultra-high stability and integratability; in addition, low-dimensional materials have no dangling bonds, are stable, have a high melting point, and are not easily damaged, making them suitable for high-power-excited large-beam electron sources; low-dimensional materials and tips can be integrated to obtain very sharp optical fiber tips, with large optical field and electric field enhancement factors, providing a large emission beam current; there are many combinations of low-dimensional materials, suitable for optoelectronic sources with various properties. Finally, the fiber-integrated low-dimensional material electron source and low-dimensional material integration have significant advantages. The optical fiber can not only transmit laser light, but also, as a carrier of low-dimensional materials, provide a stable excitation source with adjustable wavelength, polarization, and optical mode, can be applicable to different application scenarios, and does not require a complex optical path, having the characteristics of small volume and high integration. When integrated with other devices, stable integration can be achieved without performing invasive modification on the vacuum electronic device.

[0194] 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 embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered to be within the scope described in this specification.

[0195] The above-described embodiments merely represent several implementation manners of the present application. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on 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 fall within 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.

Claims

1. An electron source, characterized in that, Comprising: An optical fiber, the light-emitting end of which is provided with a pointed end; And An electron emission layer, the electron emission layer at least includes an electron excitation layer, and the electron excitation layer covers the surface of the pointed end of the optical fiber; Wherein, the optical fiber includes a core for transmitting laser, and the laser emitted from the core can directly irradiate on the electron emission layer, so that the electron excitation layer is excited by the laser emitted from the core and emits electrons; The electron excitation layer includes at least one of a zero-dimensional material, a one-dimensional material, and a two-dimensional material.

2. The electron source according to claim 1, characterized in that, The thickness of the electron excitation layer is less than or equal to 50 nm.

3. The electron source according to claim 1, characterized in that, The included angle between the axial direction of the one-dimensional material in the electron excitation layer and the emission direction of the emitted laser is 0 to 90°.

4. The electron source according to claim 1, wherein The electron excitation layer includes at least two two-dimensional materials stacked in sequence along the laser emission direction; or, The electron excitation layer includes at least two two-dimensional materials with different materials connected to each other in the same plane.

5. The electron source according to claim 1, wherein The materials in the electron excitation layer include a one-dimensional material and a zero-dimensional material provided at the end and / or side of the one-dimensional material.

6. The electron source according to claim 1, wherein The electron excitation layer includes a zero-dimensional material and a two-dimensional material, and the zero-dimensional material is provided on the surface of the two-dimensional material.

7. The electron source according to claim 1, characterized in that, The electron excitation layer includes a one-dimensional material and a two-dimensional material, and the one-dimensional material is provided on the surface of the two-dimensional material.

8. The electron source according to any one of claims 1-7, characterized in that, The electron source further includes a conductive connection layer, which is provided on the outer surface of the optical fiber and is electrically connected to the electron excitation layer.

9. The electron source according to claim 8, characterized in that, The electron excitation layer includes a first part; The projection of the first part in the target plane perpendicular to the extension direction of the core covers the projection of the core in the target plane; The first part is electrically connected to the conductive connection layer.

10. The electron source according to claim 9, characterized in that, The electron excitation layer further includes a second part connected to the first part; the projection of the second part in the target plane is located on the periphery of the projection of the first part in the target plane; and the second part overlaps with the conductive connection layer.

11. The electron source according to claim 10, characterized in that, The conductive connection layer includes a first conductive part provided at the pointed end of the optical fiber, and a second conductive part connected to the first conductive part and provided on the circumferential side surface of the optical fiber; The first conductive part overlaps with the second part.

12. The electron source according to claim 8, wherein The electron emission layer further includes an auxiliary layer, and the auxiliary layer is stacked on one side of the surface of the electron excitation layer close to the pointed end; or, The auxiliary layer is stacked on one side of the surface of the electron excitation layer far from the pointed end.

13. The electron source according to claim 12, wherein The auxiliary layer satisfies at least one of the following conditions: (1) The auxiliary layer includes at least one of a conductive support layer and a heat dissipation support layer; (2) The thickness of the auxiliary layer is 0.1 nm - 100 nm, and the light transmittance is more than 10%.

14. The electron source according to claim 12, wherein The auxiliary layer includes a conductive support layer, and the conductive support layer is electrically connected to the conductive connection layer.

15. The electron source according to claim 12, characterized in that, The auxiliary layer includes a conductive support layer, the material of the conductive support layer includes a conductive metal, the laser wavelength in the optical fiber is 200 nm to 10 μm, the pulse power is 1 nw to 1 w, and the repetition frequency is 0 Hz to 10 GHz.

16. The electron source according to any one of claims 1-7, characterized in that, Along the extension direction of the core, the size of the pointed end is L1, and the size of the electron excitation layer is L2, Among them, L1 is greater than L2.

17. The electron source according to claim 16, characterized in that, The dimensions of the pointed end portion and the dimensions of the electron excitation layer satisfy the following relationship: L2 > 1 / 2 * L1.

18. A method for preparing an electron source, characterized in that, It includes: Providing an optical fiber; among them, a pointed end portion is provided at the light-emitting end of the optical fiber; Forming an electron emission layer on the pointed end portion of the optical fiber; among them, the electron emission layer at least includes an electron excitation layer, and the electron excitation layer covers the surface of the pointed end portion of the optical fiber; Among them, the optical fiber includes a core for transmitting laser light, and the laser light emitted from the core can directly irradiate the electron emission layer, so that the electron excitation layer is excited by the laser light emitted from the core and emits electrons; The electron excitation layer includes at least one of a zero-dimensional material, a one-dimensional material, and a two-dimensional material.

19. The method for preparing an electron source according to claim 18, wherein Before or after forming the electron emission layer on the pointed end portion of the optical fiber, the preparation method of the electron source further includes: Forming a conductive connection layer on the outer surface of the optical fiber so that the conductive connection layer overlaps with the electron excitation layer.

20. The method for preparing an electron source according to claim 19, wherein, The forming of the conductive connection layer on the outer surface of the optical fiber so that the conductive connection layer overlaps with the electron excitation layer specifically includes: Forming a core protection layer on the pointed end portion of the optical fiber, wherein the projection of the core protection layer in a target plane perpendicular to the extending direction of the core covers the projection of the core in the target plane; Forming a conductive material layer covering the core protection layer on the outer surface of the optical fiber; Removing the core protection layer and the part of the conductive material layer provided on the core protection layer to form the conductive connection layer.

21. The method for preparing an electron source according to claim 18, wherein, The forming of the electron emission layer on the pointed end portion of the optical fiber specifically includes: Forming the electron excitation layer on the pointed end portion of the optical fiber by means of dipping, direct growth, or coating.

22. 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 1-17; 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.

23. Use of the electron source according to any one of claims 1-17, characterized in that, The applications of the electron source include at least one of an electron microscope, an electron beam lithography machine, a free electron laser, an X-ray tube, an electron accelerator, an electron diffraction device, and a display.

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