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 a perforated optical fiber and an electron emission layer, and the perforated optical fiber is provided with a light guide hole. The electron emission layer at least comprises an electron excitation layer, and the electron excitation layer is at least arranged on the side wall of the light guide hole and extends in the extending direction of the light guide hole. Wherein 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, excited 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 in particular, 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 classified into thermionic emission electron sources, field emission electron sources, and photoemission electron sources according to the excitation method. Thermionic emission electron sources mainly select metal materials. 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, and 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, most of the reported photoemission electron sources adopt the form of laser side irradiation of metal tips, which has disadvantages such as high operation difficulty of the irradiation method. 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] A holey optical fiber having a light guiding hole; and

[0007] An electron emission layer, the electron emission layer at least includes an electron excitation layer, the electron excitation layer is at least provided on the side wall of the light guiding hole, and extends along the extending direction of the light guiding hole;

[0008] Wherein, the electron excitation layer includes at least one of zero-dimensional materials, one-dimensional materials, and two-dimensional materials.

[0009] In one embodiment, the thickness of the electron excitation layer is less than or equal to 50 nm.

[0010] 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.

[0011] In one embodiment, the electron excitation layer includes at least two layers of two-dimensional materials stacked in sequence along the laser emission direction; or,

[0012] The electron excitation layer includes at least two two-dimensional materials with different materials connected to each other in the same plane.

[0013] In one embodiment, the materials in the electron excitation layer include one-dimensional materials and zero-dimensional materials provided at the ends and / or sides of the one-dimensional materials.

[0014] In one embodiment, the electron excitation layer includes zero-dimensional materials and two-dimensional materials, and the zero-dimensional materials are provided on the surface of the two-dimensional materials.

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

[0016] In one embodiment, the electron source further includes a conductive connection layer provided on the outer surface of the holey optical fiber;

[0017] The conductive connection layer is electrically connected to the electron excitation layer.

[0018] In one embodiment, the electron excitation layer includes a first part that completely covers the side wall of the light guiding hole, and a second part provided on the end face of the light output end of the holey optical fiber;

[0019] The second part is connected to the first part and is electrically connected to the conductive connection layer.

[0020] In one embodiment, the conductive connection layer includes a first conductive part provided on the end face of the light output end of the holey optical fiber, and a second conductive part provided on the circumferential side surface of the holey optical fiber;

[0021] Wherein, the first conductive part is connected to the second conductive part and overlaps with the second part of the electron excitation layer.

[0022] In one embodiment, the conductive connection layer includes a first metal layer and a second metal layer stacked;

[0023] The adhesion of the first metal layer is greater than the adhesion of the second metal layer.

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

[0025] The auxiliary layer is stacked on one side of the electron excitation layer far from the side wall of the light guiding hole.

[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 0.31 nm to 10 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 holey 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, the holey optical fiber includes a hollow holey optical fiber, a light guiding medium is provided in the light guiding hole, and the light guiding medium includes air or a noble gas.

[0032] According to the second aspect of the present application, a method for preparing an electron source is provided, including:

[0033] Providing a holey optical fiber; wherein, the holey optical fiber has a light guiding hole;

[0034] Forming an electron emission layer on the side wall of the light guiding hole;

[0035] Wherein, the electron emission layer at least includes an electron excitation layer, the electron excitation layer is at least provided on the side wall of the light guiding hole and extends along the extension direction of the light guiding hole, and the electron excitation layer includes at least one of a zero-dimensional material, a one-dimensional material, and a two-dimensional material.

[0036] In one embodiment, before or after forming the electron emission layer on the side wall of the light guiding hole, the method for preparing the electron source further includes:

[0037] Forming a conductive connection layer on the outer surface of the holey optical fiber so that the electron excitation layer overlaps with the conductive connection layer.

[0038] In one embodiment, forming the conductive connection layer on the outer surface of the holey optical fiber so that the electron excitation layer overlaps with the conductive connection layer specifically includes:

[0039] Forming a core protection layer on the light output end of the holey optical fiber, wherein the core protection layer covers one end of the light guiding hole located at the end face of the light output end;

[0040] Forming a conductive material layer covering the core protection layer on the outer surface of the holey optical fiber;

[0041] 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.

[0042] In one embodiment, forming an electron emission layer on the sidewall of the light guiding hole specifically includes:

[0043] Form the electron excitation layer by a direct growth method or a coating method.

[0044] According to a third aspect of the present application, there is provided an electron gun, which includes a housing, a grid, an anode, and the electron source according to any one of the above embodiments;

[0045] 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.

[0046] According to a fourth aspect of the present application, there is provided an application of the electron source according to any one of the above embodiments. The application of the electron source includes at least one of an electron microscope, an electron beam exposure machine, a free electron laser, an electron diffraction device, an electron accelerator, an X-ray tube, and a display.

[0047] In the technical solution of the present application, during the transmission of laser in the holey optical fiber, an evanescent wave can be generated at the sidewall of the light guiding hole. Since the electron excitation layer is disposed on the sidewall of the light guiding hole, the laser can interact with the electron excitation layer through the evanescent wave, so that the electrons in the electron excitation layer absorb the energy of the evanescent wave and transition. These electrons can escape outside the electron excitation layer, and thus the excitation of electrons can be realized. The present 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 excited 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 discrete electron energy levels, so that the laser can 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 to form an electron beam, and the electron beam tunneling-emitted from the electron excitation layer has the characteristics of energy concentration and small energy dispersion. In addition, the low-dimensional materials can be directly integrated with the optical fiber. The optical fiber transmits laser and serves as the carrier of the low-dimensional materials, 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. Description of the Drawings

[0048] Figure 1 Shows a schematic structural diagram of an electron source according to an embodiment of the present application.

[0049] Figure 2 shows Figure 1 a sectional view taken along line A-A of

[0050] Figure 3 shows Figure 1 an enlarged schematic view of B of

[0051] Figure 4 shows a circuit block diagram of an electron source and an anode according to an embodiment of the present application.

[0052] Figure 5 shows a schematic structural view of an electron source according to another embodiment of the present application.

[0053] Figure 6 shows Figure 5 an enlarged schematic view of C of

[0054] Figure 7 shows a schematic flow chart of a method for preparing an electron source according to an embodiment of the present application.

[0055] Figure 8 shows a schematic structural view of an electron gun according to an embodiment of the present application.

[0056] Reference numerals:

[0057] 10, electron gun;

[0058] 100, electron source;

[0059] 110, optical fiber; 111, optical fiber; 112, annular light guide tube body;

[0060] 1101, light incident end; 1102, light exit end; 11021, end face; k, side wall of light guide hole;

[0061] 120, electron emission layer; 121, electron excitation layer; 1211, first part; 1212, second part; 122, auxiliary layer;

[0062] 130, conductive connection layer; 131, first conductive part; 132, second conductive part;

[0063] 200, gate; 210, second electron channel;

[0064] 300, anode; 310, first electron channel. Detailed embodiments

[0065] To make the above objects, features, and advantages of the present application more apparent and understandable, the following provides a detailed description of the specific embodiments of the present application in conjunction with the accompanying drawings. Many specific details are set forth in the following description to facilitate a full understanding of 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.

[0066] 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. These are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present application.

[0067] In addition, if terms such as "first" and "second" appear, these terms are only used for descriptive purposes 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 of such features. In the description of the present application, if the term "plurality" appears, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise specifically and clearly defined.

[0068] In the present application, unless otherwise clearly defined and limited, if terms such as "install", "connect", "join", "fix", 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 limited. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0069] In this application, unless otherwise clearly specified and defined, when a first feature is described as being "on" or "under" a second feature or the like, it may mean 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" or "on top of" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" or "underneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or simply indicates that the first feature has a lower horizontal height than the second feature.

[0070] It should be noted that if an element is referred to as being "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.

[0071] In the traditional technology, the thermionic electron source mainly selects materials with metallic properties such as tungsten wire and lanthanum hexaboride. When heated to thousands of degrees Celsius, electrons are thermally excited to escape from the material surface to form vacuum electrons. The field emission electron source mainly selects metal tips such as tungsten. Under the action of a strong electric field applied from the outside, a tip discharge effect is generated. Among them, the electron beam emitted by the thermionic electron source can work in a relatively poor vacuum environment, has good adaptability to the environment and good 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 the vacuum degree and is very sensitive to vibrations. Whether it is a thermionic electron source or a field emission electron source, the regulation of the electron emission properties is limited, and it is impossible to balance the emission efficiency and stability.

[0072] In the traditional technology, the photoemission electron source uses metal materials such as Au as the material of the electron emission layer, and the thickness is above 50 nm, even reaching hundreds of nanometers. However, the inventors of this application have found through research that the electron emission layer made of metal materials 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 emission efficiency and stability of electrons.

[0073] In the traditional technology, there is also a type of photoemission electron source where electrons are excited by an external laser incident on the surface of a metal tip. Since the size of the metal tip is in the nanometer range, it is difficult to align 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.

[0074] In addition, in the traditional technology, graphene is used as a saturable absorber. Graphene has broadband saturable absorption characteristics and a fast recovery time. It is used in the Q-switching and mode-locking of lasers, or graphene is used to adjust the laser spectrum for 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. For the described graphene saturable absorber, it 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 optical splitter of the cavity.

[0075] Based on this, it is necessary to provide an electron source that can balance the electron emission efficiency and stability.

[0076] 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 emit electrons under laser irradiation due to the photoelectric effect. 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 optical fibers, and the optical fibers can provide a stable excitation source with adjustable wavelength, polarization, and optical mode, and can be applied to different application scenarios.

[0077] Figure 1 The structural schematic diagram of the electron source 100 in an embodiment of this application is shown.

[0078] Please refer to Figure 1 and, in combination with referring to Figure 2 and Figure 3 According to the first aspect of this application, an electron source 100 is provided, including a holey optical fiber 110 and an electron emission layer 120.

[0079] The porous optical fiber 110 has a light guiding hole. Among them, the porous optical fiber 110 is a transmission medium for laser and a carrier for low-dimensional materials. The porous optical fiber 110 may include a hollow porous optical fiber, and the hollow porous optical fiber may be a single-hole or multi-hole hollow optical fiber; of course, the porous optical fiber 110 may also include a solid-core porous optical fiber, and the solid-core porous optical fiber may be a single-hole or multi-hole solid-core optical fiber, which is not specifically limited herein. Figure 1 An example is given where the porous optical fiber 110 is a single-hole hollow optical fiber.

[0080] Specifically, such as Figure 1 In the illustrated embodiment, a core 111 composed of air is provided in the light guiding hole. The porous optical fiber 110 further includes an annular light guiding tube body 112 surrounding the core 111, and the side wall k of the light guiding hole is formed on the inner side wall of the annular light guiding tube body 112. Specifically, the material of the annular light guiding tube body 112 may be high borosilicate, glass or quartz, etc. More specifically, the porous optical fiber 110 is a capillary optical fiber.

[0081] The porous optical fiber 110 has an incident light end 1101 and an outgoing light end 1102 which are oppositely arranged. The incident light end 1101 is used to be coupled to a laser source so that the laser emitted by the laser source can be transmitted through the porous optical fiber 110. Among them, the laser source may be a laser.

[0082] The electron emission layer 120 at least includes an electron excitation layer 121. The electron excitation layer 121 is at least provided on the side wall k of the light guiding hole, and the electron excitation layer 121 extends along the extending direction of the light guiding hole. The electron excitation layer 121 includes at least one of zero-dimensional materials, one-dimensional materials and two-dimensional materials.

[0083] It may be that the entire electron excitation layer 121 is provided on the side wall k of the light guiding hole; or it may be that a part of the electron excitation layer 121 is provided on the side wall k of the light guiding hole. This is not specifically limited herein.

[0084] The electron excitation layer 121 may include zero-dimensional materials. Zero-dimensional materials refer to materials whose dimensions in the three spatial scale directions are in 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 C60 or carbon-coated nanometer metal particles, etc. Zero-dimensional materials have typical discrete energy levels. Under the action of laser excitation, electrons are mainly tunnel-excited from the discrete energy levels, so that the electron beam tunnel-emitted from the electron excitation layer 121 has the characteristics of energy concentration and small energy dispersion.

[0085] The electron excitation layer 121 may also include one-dimensional materials. The electrons in the one-dimensional materials can be transported along the linear chain of the one-dimensional materials. Combining with the fact that the electron excitation layer 121 is disposed on the end face 11021 of the light-emitting end 1102 of the optical fiber 110, it is beneficial for the electrons emitted by the electron source to be emitted efficiently along the extending direction of the optical fiber 110. The one-dimensional materials have the characteristics of small curvature radius (nanoscale), which can enhance the light-matter interaction and provide a large field enhancement factor, ensuring multi-photon emission, optical field emission, etc., and are applied to scenarios requiring a high-brightness electron source.

[0086] The one-dimensional materials can be nanotubes, nanorods or nanowires, nanoribbons or coaxial nanocables, etc.

[0087] The nanotubes can be carbon nanotubes, which can be regarded as seamless tubular structures formed by winding single-layer or multi-layer graphite according to certain rules. The nanotubes can also be silicon (Si) nanotubes, selenium (Se) nanotubes, tellurium (Te) nanotubes, bismuth (Bi) nanotubes, boron nitride (BN) nanotubes, boron-nitrogen co-doped carbon nanotubes (BCN nanotubes), tungsten disulfide (WS2) nanotubes, molybdenum disulfide (MoS2) nanotubes or titanium dioxide (TiO2) nanotubes, etc.

[0088] The material of the nanowires can be silicon (Si) or germanium (Ge); the nanowires can also be oxide nanowires, such as tin oxide (SnO) or zinc oxide (ZnO), etc.; of course, the nanowires can also be nitride nanowires, such as gallium nitride (GaN) or silicon nitride (Si3N4), etc.; the nanowires can also be sulfide nanowires, such as cadmium sulfide (CdS) and zinc sulfide (ZnS), etc.; the nanowires can also be ternary compound nanowires, such as barium titanate (BaTiO3) and lead titanate (PbTiO3), etc.

[0089] The nanoribbons are quite different from the above two nanoscale structures (nanotubes and nanowires). Their cross-sections are different from the nearly circular shapes of nanotubes or nanowires, but are quadrilateral, and the aspect ratio distribution range is generally from several to more than a dozen. The material of the nanoribbons can be oxides, such as tin oxide (SnO) or zinc oxide (ZnO), etc.

[0090] The coaxial nanocables can be graphite / boron nitride (C / BN) coaxial nanocables or silicon carbide / sulfur dioxide (CSi / SiO2) coaxial nanocables, etc.

[0091] The electron excitation layer 121 may also include a two-dimensional material. The electrons in the two-dimensional material can be transmitted along a two-dimensional plane. Considering that the electron excitation layer 121 is disposed on the end face 11021 of the light output end 1102 of the optical fiber 110, this is conducive to the efficient emission of the electrons emitted by the electron source 100 along the extension direction of the optical fiber 110. Moreover, compared with setting a thin metal layer on the optical fiber, it will cause a decrease in the melting point of the metal layer, which will further lead to the problem of easy damage of the metal layer. 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 material are more discrete, and the energy of the electron beam emitted by tunneling is more concentrated and the energy dispersion is smaller.

[0092] The two-dimensional material has the characteristic of atomic layer thickness. The thickness of the two-dimensional material 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 material, it hardly affects the light transmission mode and has high stability. Moreover, the excited electrons can be directly emitted without internal scattering in the material, ensuring the purity of the properties of the emitted electrons and an extremely narrow pulse width.

[0093] The two-dimensional material can be graphene, transition metal sulfide, two-dimensional perovskite, two-dimensional diamond, boron nitride, etc.

[0094] Taking graphene as an example of the two-dimensional material for illustration, the carbon atoms in graphene are bonded in the form of covalent bonds in the plane to form a hexagonal honeycomb planar structure. The electron excitation layer 121 can have a thickness of one atomic layer, about 0.34 nanometers; the electron excitation layer 121 can also have a thickness of several or dozens of atomic layers.

[0095] 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.

[0096] In this way, when the electron source 100 is in use, during the transmission of the laser in the perforated optical fiber 110, an evanescent wave can be generated at the side wall k of the light guiding hole. Since the electron excitation layer 121 is disposed on the side wall k of the light guiding hole, the laser can interact with the electron excitation layer 121 through the evanescent wave, so that the electrons in the electron excitation layer 121 absorb the energy of the evanescent wave and transition. These electrons can escape from the electron excitation layer 121, and thus the excitation of electrons can be realized.

[0097] It should be noted that whether it is a hollow-core holey fiber or a solid-core holey fiber, the laser emitted by the laser source can be transmitted through the holey fiber 110 to the light-emitting end 1102 of the holey fiber 110. During the transmission of the laser in the holey fiber 110, an evanescent wave can be generated at the side wall k of the light-guiding hole. The laser can interact with the electron excitation layer 121 through the evanescent wave, so that the electrons in the electron excitation layer 121 absorb the energy of the evanescent wave and transition. These electrons can escape outside the electron excitation layer 121, and thus the excitation of electrons can be realized.

[0098] 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. It abandons the complex spatial light coupling structure set due to the introduction of external lasers, and also abandons the high-magnification microscope set to solve the alignment problem of metal tips, which can reduce the process cost of the electron gun.

[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 (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 material has an atomic thickness, and the excited electrons can be emitted without passing through in-body transmission, with a high electron emission efficiency; moreover, the low-dimensional material has no dangling bonds, is stable in nature and has a high melting point, is not easily damaged, and can be applied to high-power excitation scenarios, with characteristics such as good stability and high service life; in addition, the low-dimensional material also has a high optical nonlinear effect and discrete electron energy levels, 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 an electron beam can be formed, 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, the low-dimensional material and the optical fiber 110 can be directly integrated. The optical fiber transmits the laser and serves as the carrier of the low-dimensional material, which 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, with characteristics such as small volume and high integration.

[0101] It should be noted that the wavelength of the laser can be a wavelength that enables electrons in the electron excitation layer 121 to absorb a photon and transition. For example, the wavelength is in the range of visible light - near-infrared - ultraviolet. The wavelength of the laser can also be a wavelength that enables electrons in the electron excitation layer 121 to absorb multiple photons and transition. For example, the wavelength is outside the range of visible light - near-infrared - ultraviolet, and no specific limitation is made here.

[0102] In some embodiments, the holey optical fiber includes a hollow core holey optical fiber, and a light guiding medium is provided in the light guiding hole. The light guiding medium includes air or rare gas.

[0103] The light guiding medium can be air or rare gas. Using rare gas can generate nonlinear optical effects, and thus the optical pulse output by the holey optical fiber 110 can be transformed from a single wavelength to the ultraviolet to infrared band or the terahertz band, and even generate an ultra-wideband supercontinuum spectrum, which is also beneficial to better exciting the electron excitation layer 121 to emit electrons outward.

[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 of magnitude and the thickness of the electron excitation layer 121 is small. Thus, it is more beneficial to reduce the process of the excited electrons performing in-body transmission in the electron excitation layer 121, and it is more beneficial to improve the electron emission efficiency and emission power. Furthermore, an electron beam with ultrashort pulses can be realized by using the electron source 100.

[0106] In some embodiments, the included 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 realized 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 realized. Here, the low density refers to the number of one-dimensional materials per unit line segment. For example, a density less than n pieces / nm is a low density, and a density greater than n pieces / nm is a high density, where n is 1, 2 or 3.

[0108] In some embodiments, the axial direction of the one-dimensional material and the emission direction of the laser have an included angle, and the included 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 in 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 in the same plane, thereby forming a vertical heterojunction or a planar heterojunction. The heterojunction structure can enhance the interaction between light and two-dimensional materials, achieve efficient electron emission under 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 materials in the electron excitation layer 121 include one-dimensional materials and zero-dimensional materials disposed at the ends and / or sides of the one-dimensional materials.

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

[0114] In some embodiments, 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.

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

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

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

[0118] In some embodiments, the zero-dimensional materials, one-dimensional materials or two-dimensional materials independently include doping elements.

[0119] In this application, element doping is performed on low-dimensional materials to improve the conductivity and electron emission performance of the low-dimensional materials. For example, doping with boron can improve the conductivity and electron emission performance of the low-dimensional materials.

[0120] Optionally, the doping element includes at least one of boron, nitrogen, phosphorus, lithium, and potassium.

[0121] In some embodiments, at least a part of the electron excitation layer 121 completely covers the side wall k of the light guiding hole.

[0122] It may be that the electron excitation layer 121 completely covers the side wall k of the light guiding hole; or it may be that a part of the electron excitation layer 121 completely covers the side wall k of the light guiding hole, and no specific limitation is made here.

[0123] In this way, the laser transmitted in the holey optical fiber 110 can better interact with the electron excitation layer 121 and excite the electron excitation layer 121 to emit electrons outward.

[0124] In some embodiments, the electron source 100 further includes a conductive connection layer 130 provided on the outer surface of the holey optical fiber 110, and the conductive connection layer 130 is electrically connected to the electron excitation layer 121.

[0125] 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.

[0126] 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, electrons can be supplied to the electron excitation layer 121 by the power supply, 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.

[0127] Exemplarily, such as Figure 4As shown, the electron source 100 is applied to an electron gun, which further includes an anode 300. The anode 300 has a first electron channel 310 for electrons emitted from within the electron excitation layer 121 to pass through. A preset voltage is provided between the anode 300 and the conductive connection layer 130, such that a preset electric field is formed between the anode 300 and the conductive connection layer 130. As a result, the electrons emitted from within 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 and are emitted. 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 holey optical fiber 110. In this way, it is beneficial to use the anode 300 to form a uniform electric field along the axis direction of the holey optical fiber 110, which is more conducive to the electrons to be linearly accelerated along the axis direction of the holey optical fiber 110 and pass through the first electron channel 310.

[0128] In some embodiments, referring to Figure 3 , the electron excitation layer 121 includes a first portion 1211 that completely covers the side wall k of the light guiding hole, and a second portion 1212 provided on the end face 11021 of the light output end 1102 of the holey optical fiber 110. The first portion 1211 is connected to the second portion 1212, and the second portion 1212 is electrically connected to the conductive connection layer 130.

[0129] In this way, by using the conductive connection layer 130 to be electrically connected to the second portion 1212 of the electron excitation layer 121, on the one hand, the conductive connection layer 130 can supply electrons to the electron excitation layer 121, which is beneficial for the electron excitation layer 121 to continuously emit electrons under the excitation of laser. On the other hand, since the second portion 1212 is provided on the light output end 1102 of the holey optical fiber 110, during the process of the laser transmitted in the holey optical fiber 110 towards the light output end 1102, the laser can not only interact with the first portion 1211 of the electron excitation layer 121 through the evanescent wave, but also interact with the second portion 1212 on the light output end 1102, so that the electrons in the electron excitation layer 121 absorb the energy of photons and transition. These electrons can escape outside the electron excitation layer 121, and thus the electrons can be emitted efficiently along the axis direction of the holey optical fiber 110.

[0130] In some embodiments, the conductive connection layer 130 includes a first conductive portion 131 provided on the end face 11021 of the light output end 1102 of the holey optical fiber 110, and a second conductive portion 132 provided on the circumferential side surface of the holey optical fiber 110. The first conductive portion 131 is connected to the second conductive portion 132, and the first conductive portion 131 overlaps with the second portion 1212 of the electron excitation layer 121.

[0131] In this way, the conductive connection layer 130 can cover the porous optical fiber 110 more, improving the bonding strength between the conductive connection layer 130 and the porous optical fiber, and also facilitating better use of the conductive connection layer 130 to supply electrons to the electron excitation layer 121. Since the first conductive portion 131 overlaps with the second portion 1212, the first conductive portion 131 is in electrical contact with the second portion 1212, and the orthographic projection of the first conductive portion 131 on the light-emitting end 1102 is located outside the side wall k of the light-guiding hole.

[0132] In this way, while the conductive connection layer 130 can supply electrons to the electron excitation layer 121, it does not affect the interaction between the laser and the electron excitation layer 121.

[0133] In some embodiments, both the first portion 1211 and the second portion 1212 are in a ring structure, and the inner diameter of the first portion 1211 is less than or equal to the inner diameter of the second portion 1212.

[0134] In this way, it is beneficial for the laser to interact with the first portion 1211 of the electron excitation layer 121 through the evanescent wave. Combining with the fact that the laser can also interact with the second portion 1212 on the light-emitting end 1102, electrons in the electron excitation layer 121 absorb the energy of the evanescent wave and transition. These electrons can escape outside the electron excitation layer 121, and then high-efficiency electron emission can be achieved along the axis direction of the porous optical fiber 110.

[0135] In some embodiments, the conductive connection layer 130 includes a first metal layer and a second metal layer arranged in a stacked manner, and the adhesion of the first metal layer is greater than that of the second metal layer.

[0136] Exemplarily, the material of the first metal layer is titanium, palladium or chromium, and the material of the second metal layer is gold.

[0137] In this way, the first metal layer with higher adhesion can make the conductive connection layer 130 better adhere to the porous optical fiber 110, improving the bonding strength between the conductive connection layer 130 and the porous optical fiber 110, and also being beneficial to improving the service life of the conductive connection layer 130.

[0138] In some embodiments, the electron emission layer 120 further includes an auxiliary layer 122. The auxiliary layer 122 is arranged in a stacked manner on one side of the electron excitation layer 121 close to the side wall k of the light-guiding hole, or the auxiliary layer 122 is arranged in a stacked manner on one side of the electron excitation layer 121 far from the side wall k of the light-guiding hole. Figure 5 and Figure 6 An example is given where the auxiliary layer 122 is arranged on one side of the electron excitation layer 121 close to the side wall k of the light-guiding hole.

[0139] In this application, an 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 disposed on the auxiliary layer 122; or, when the electron excitation layer 121 cannot be directly connected and conductively connected to the conductive connection layer 130, it is connected to the conductive connection layer 130 through the conductive auxiliary layer 122, and the electron excitation layer 121 and the conductive connection layer 130 are electrically connected by using the auxiliary layer 122.

[0140] Optionally, the auxiliary layer 122 includes at least one of a conductive support layer and a heat dissipation support layer.

[0141] Optionally, the thickness of the auxiliary layer 122 is 0.1 nm - 100 nm. Specifically, the thickness of the auxiliary layer 122 is 0.3 nm - 10 nm.

[0142] Optionally, the light transmittance of the auxiliary layer 122 is 10% or more. Specifically, the light transmittance is 10% - 98%. Exemplarily, the light transmittance is 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or 98%.

[0143] Optionally, the auxiliary layer 122 includes a conductive support layer, and the conductive support layer is electrically connected to the conductive connection layer 130.

[0144] In some embodiments, please refer to Figure 7 , 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 holey optical fiber 110 is 200 nm - 10 μm, the pulse power is 1 nw - 1 w, and the repetition frequency is 0 Hz - 10 GHz.

[0145] 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 122 has the functions of support and conduction.

[0146] The auxiliary layer 122 may also include a conductive support layer. The electron excitation layer 121 is disposed on the sidewall k of the light guiding hole through the auxiliary layer 122, and the auxiliary layer 122 is a light-transmitting material. In this way, the auxiliary layer 122 can be used to make the electron excitation layer 121 more flatly disposed on the sidewall k of the light guiding hole, 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, other materials that can dissipate heat for the electron excitation layer 121 and enable the electron excitation layer 121 to be flatly disposed on the side wall k of the light guiding hole may also be selected for the material of the auxiliary layer 122. 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] Please refer to Figure 7 , according to the second aspect of the present application, a method for preparing an electron source 100 is provided, including the following steps:

[0149] S210. Provide a holey optical fiber 110. Among them, the holey optical fiber 110 has a light guiding hole.

[0150] Optionally, an appropriate length of the holey optical fiber 110 can be intercepted, the end coating layer of the holey optical fiber 110 can be removed, and one end of the cut holey optical fiber 110 can be processed to form a light output end 1102. Specifically, a cutting mechanism can be used to cut one end of the cut holey optical fiber 110 to form the light output end 1102. By using the cutting method to form the light output end 1102, the end face 11021 of the light output end 1102 can be relatively flat, which is beneficial to forming a flat electron excitation layer 121 on the end face 11021 of the light output end 1102.

[0151] S220. Form an electron emission layer 120 on the side wall k of the light guiding hole, where the electron emission layer 120 at least includes an electron excitation layer 121, the electron excitation layer 121 is at least disposed on the side wall of the light guiding hole, and extends along the extension direction of the light guiding hole. Among them, the electron excitation layer includes at least one of zero-dimensional materials, one-dimensional materials, and two-dimensional materials.

[0152] Optionally, the step S220 of forming the electron emission layer 120 on the side wall k of the light guiding hole specifically includes:

[0153] The electron excitation layer 121 is formed by a direct growth method or a coating method.

[0154] The electron excitation layer 121 can be formed by a direct growth method. For example, the electron excitation layer 121 can be formed by chemical vapor deposition, or the electron excitation layer 121 can be formed by a coating method.

[0155] Optionally, the first part 1211 of the electron excitation layer 121 completely covers the side wall k of the light guiding hole, and the second part 1212 of the electron excitation layer 121 is disposed on the light output end 1102 of the holey optical fiber 110 and is electrically connected to the conductive connection layer 130.

[0156] Optionally, before or after forming the electron emission layer 120 on the side wall k of the light guide hole, the method for preparing the electron source further includes:

[0157] S230. Form a conductive connection layer 130 on the outer surface of the hole-containing optical fiber 110, so that the electron excitation layer 121 overlaps with the conductive connection layer 130.

[0158] That is to say, the conductive connection layer 130 can be formed first, and then the electron excitation layer 121 can be formed; or the electron excitation layer 121 can be formed first, and then the conductive connection layer 130 can be formed; 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 through 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.

[0159] Optionally, forming a conductive connection layer 130 on the outer surface of the hole-containing optical fiber 110, so that the electron excitation layer 121 overlaps with the conductive connection layer 130, specifically includes:

[0160] S231. Form a core protection layer on the light-emitting end 1102 of the hole-containing optical fiber 110, and the core protection layer covers one end of the light guide hole located at the end face 11021 of the light-emitting end 1102. That is to say, the outer contour of the orthographic projection of the core protection layer on the light-emitting end 1102 is located outside the side wall k of the light guide hole.

[0161] Optionally, a polymer microsphere solution can be coated on the light-emitting end 1102 of the hole-containing optical fiber 110 to form a core protection layer covering one end of the light guide hole located at the end face of the light-emitting end. Exemplarily, the polymer microsphere solution is a polymethyl methacrylate suspension.

[0162] S232. Form a conductive material layer covering the core protection layer on the outer surface of the hole-containing optical fiber 110.

[0163] The conductive material layer can be formed by evaporation coating. Specifically, a metal evaporation coating device can be used to form the conductive material layer on the outer surface of the hole-containing optical fiber 110.

[0164] S233. Remove the core protection layer and the part of the conductive material layer provided on the core protection layer to form the conductive connection layer 130.

[0165] Optionally, a solvent that can dissolve the core protection layer and does not interact with the conductive material can be used to remove the core protection layer. Specifically, the light-emitting end 1102 of the hole-containing optical fiber 110 can be soaked in acetone, so that the core protection layer (polymer microspheres) is dissolved, and the part of the conductive material layer provided on the core protection layer (part of the metal coating) is peeled off to obtain the conductive connection layer 130.

[0166] It can be understood that the core protection layer can be used to make the positive projection of the first conductive part 131 of the conductive connection layer 130 on the light-emitting end 1102 located outside the side wall k of the light guide hole, so that the laser transmitted in the holey optical fiber 110 can better interact with the electron excitation layer 121.

[0167] Please refer to Figure 8 , according to the third aspect of the present application, an electron gun 10 is provided, which includes the electron source 100 of any one of the above embodiments.

[0168] 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.

[0169] The electron source 100 is fixed inside the housing, and a grid 200 and an anode 300 are sequentially arranged on the electron emission side of the electron source 100.

[0170] 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 pass through the first electron channel 310 of the anode 300 and then emit for use.

[0171] 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 lithography machine, a free electron laser, an electron accelerator, an electron diffraction device, an X-ray tube, and a display.

[0172] The embodiments of the present invention will be described in detail below in conjunction with the embodiments. It should be understood that these embodiments 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 embodiments, 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 manufacturer, or referring to the experimental methods known in the art.

[0173] Embodiment 1

[0174] Please refer to Figures 1-3, the porous optical fiber 110 is a capillary optical fiber tube. The core 111 of the porous optical fiber 110 has a diameter of 10 μm, the diameter of the porous optical fiber 110 is 125 μm, and the wavelength of the laser transmitted in the porous optical fiber 110 is 1550 nm. The conductive connection layer 130 includes 4 nm of titanium and 50 nm of gold that are located on the periphery of the core 111 and are laminated on the porous optical fiber 110. The electron excitation layer 121 is formed on the sidewall k of the light guiding hole and the end face 11021 of the light output end 1102 of the porous optical fiber by CVD. The electron excitation layer 121 is made of graphene two-dimensional material (the thickness of the graphene two-dimensional material is 0.3 nm). Among them, the first part 1211 of the electron excitation layer 121 completely covers the sidewall k of the light guiding hole, and the second part 1212 of the electron excitation layer 121 is provided on the end face 11021 of the light output end 1102 of the porous optical fiber.

[0175] Example 2

[0176] The porous optical fiber 110 is a capillary optical fiber tube. The core 111 of the porous optical fiber 110 has a diameter of 10 μm, the diameter of the porous optical fiber 110 is 125 μm, and the wavelength of the laser transmitted in the porous optical fiber 110 is 1550 nm. The conductive connection layer 130 includes 4 nm of titanium and 50 nm of gold that are located on the periphery of the core 111 and are laminated on the porous optical fiber 110. The electron excitation layer 121 is formed on the sidewall k of the light guiding hole by CVD. The electron excitation layer 121 is made of graphene two-dimensional material (the thickness of the graphene two-dimensional material is 3 nm).

[0177] Example 3

[0178] Please refer to Figure 5 and Figure 6 , an auxiliary layer 122 with a thickness of 50 nm and a material of gold is deposited and grown on the sidewall k of the light guiding hole and the end face 11021 of the light output end 1102 of the porous optical fiber by CVD. Then, carbon nanotubes are prepared on the surface of the auxiliary layer 122 by CVD. The axial direction of the carbon nanotubes is perpendicular to the surface of the auxiliary layer 122 to form the electron excitation layer 121. The auxiliary layer 122 is electrically connected to the conductive connection layer 130 to obtain the electron source 100. In this embodiment, the auxiliary layer 122 overlaps with the first conductive part 131 of the conductive connection layer 130, and the second conductive part 132 of the conductive connection layer 130 is provided on the circumferential side surface of the optical fiber 110.

[0179] Example 4

[0180] The graphene with a thickness of 2 nm is deposited and grown on the side wall k of the light guide hole and the end face 11021 of the light-emitting end 1102 of the fiber with holes by means of CVD; then a carbon nanotube is coated on the surface of the graphene, and the axial direction of the carbon nanotube is parallel to the plane of the graphene. Then, a plurality of quantum dots are grown on the carbon nanotube by CVD method to obtain an electron excitation layer 121. Among them, the graphene is electrically connected to the conductive connection layer 130 to obtain an electron source 100.

[0181] Comparative Example 1

[0182] The electron source is prepared according to the structure of Example 1, and the difference is only that the electron excitation layer 121 in Example 1 is replaced by a gold layer with a thickness of 100 nm, and the gold layer is prepared by deposition.

[0183] Comparative Example 2

[0184] The electron source is prepared according to the structure of Comparative Example 1, and the difference is only that the electron excitation layer 121 in Comparative Example 1 is replaced by a gold layer with a thickness of 2 nm (the same thickness as the graphene).

[0185] As Figure 6 shown, the electron sources prepared by the above-mentioned examples and comparative examples are assembled into an electron gun. The electron gun further includes a housing, a grid 200 and an anode 300. The performance of the prepared electron gun is tested, and the test results are as follows in the table:

[0186] Table 1

[0187] Number Stability Lifetime Operating vacuum Example 1 2％ 1000h <![CDATA[10 -2 Pa]]> Example 2 2％ 1000 h <![CDATA[10 -2 Pa]]> Example 3 5％ 5000 h <![CDATA[10 -2 Pa]]> Example 4 5％ 5000 h <![CDATA[10 -2 Pa]]> Comparative Example 1 10％ 100 h <![CDATA[10 -5 Pa]]> Comparative Example 2 20％ 20 h <![CDATA[10 -5 Pa]]>

[0188] Among them, the 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, the continuous emission current is 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. The 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, the continuous emission 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, the continuous emission current. The vacuum degree gradually increases until the current shows a rapid decay (the rapid decay is defined as the current decays 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 better stability, longer lifetime, and better working vacuum degree.

[0189] Through testing, it is found that compared with the lifespan of the electron source prepared by the comparative example, the lifespan 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.

[0190] In summary, low-dimensional materials such as zero-dimensional materials, one-dimensional materials, and two-dimensional materials in this application have atomic-scale sizes. The electrons excited do not need to be transmitted through the body and can be emitted into the vacuum, which is beneficial to improving the emission efficiency and emission power of electrons and is very suitable for ultrafast electron sources with narrow pulse widths. Moreover, the electron source 100 of this application uses low-dimensional materials as the materials for emitting electrons. Since low-dimensional materials have high optical nonlinear effects and discrete electron energy levels, the laser can 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 to 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. In addition, low-dimensional materials and different types of optical fibers can be directly integrated, bringing ultra-high stability and integration. At the same time, the electron excitation layer 121 at the nanometer scale does not affect the transmission mode of the porous optical fiber 110, so that the transmission mode of the electron source 100 is mainly determined by the porous optical fiber 110, enabling the electrons emitted by the electron source 100 to be efficiently emitted along the extension direction of the porous optical fiber 110, which provides great convenience for controlling the transmission mode of the electron source 100. Moreover, low-dimensional materials have no dangling bonds, are stable, have high melting points, are not easily damaged, and are suitable for high-power-excited large-beam electron sources. The integration of low-dimensional materials and the tip can obtain a very sharp optical fiber tip 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 integration of optical fiber and low-dimensional material electron source and the integration of low-dimensional materials 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, which can be applied to different application scenarios. Moreover, the electron source 100 abandons the complex spatial light coupling structure set due to the introduction of external laser light, has the characteristics of small volume and high integration, is convenient to be assembled into the shell of the electron gun, and when integrated with other devices, it is possible to achieve stable integration without performing invasive modification on the vacuum electronic device.

[0191] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of 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.

[0192] 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 to the scope of the patented 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: A holey optical fiber having a light guiding hole; And An electron emission layer, the electron emission layer at least includes an electron excitation layer, the electron excitation layer is at least disposed on the side wall of the light guiding hole and extends along the extending direction of the light guiding hole; Wherein, 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 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.

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, characterized in that, The materials in the electron excitation layer include a one-dimensional material and a zero-dimensional material disposed at the end and / or side of the one-dimensional material.

6. The electron source according to claim 1, characterized in that, The electron excitation layer 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.

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 disposed 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 disposed on the outer surface of the holey optical fiber; The conductive connection layer is electrically connected to the electron excitation layer.

9. The electron source according to claim 8, wherein, The electron excitation layer includes a first part that completely covers the side wall of the light guiding hole, and a second part disposed on the end face of the light emitting end of the holey optical fiber; The second part is connected to the first part and is electrically connected to the conductive connection layer.

10. The electron source according to claim 9, characterized in that, The conductive connection layer includes a first conductive part disposed on the end face of the light emitting end of the holey optical fiber, and a second conductive part disposed on the circumferential side surface of the holey optical fiber; Wherein, the first conductive part is connected to the second conductive part and overlaps with the second part of the electron excitation layer.

11. The electron source according to claim 8, wherein The conductive connection layer includes a first metal layer and a second metal layer stacked; The adhesion of the first metal layer is greater than the adhesion of the second metal layer.

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 electron excitation layer close to the side wall of the light guiding hole; or, The auxiliary layer is stacked on one side of the electron excitation layer away from the side wall of the light guiding hole.

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 to 10 nm, and the light transmittance is more than 10%.

14. The electron source according to claim 12, characterized in that, 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, wherein The auxiliary layer includes a conductive support layer, the material of the conductive support layer includes a conductive metal, the laser wavelength in the holey 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, The holey optical fiber includes a hollow core holey optical fiber, a light guiding medium is provided in the light guiding hole, and the light guiding medium includes air or a noble gas.

17. A method for preparing an electron source, characterized in that, Comprising: Providing a holey optical fiber; wherein, the holey optical fiber has a light guiding hole; An electron emission layer is formed on the side wall of the light guiding hole; wherein, the electron emission layer at least includes an electron excitation layer, the electron excitation layer is at least disposed on the side wall of the light guiding hole and extends along the extending direction of the light guiding hole; Wherein, the electron excitation layer includes at least one of a zero-dimensional material, a one-dimensional material, and a two-dimensional material.

18. The method for preparing an electron source according to claim 17, wherein Before or after forming the electron emission layer on the side wall of the light guiding hole, the preparation method of the electron source further includes: Forming a conductive connection layer on the outer surface of the porous optical fiber so that the electron excitation layer overlaps with the conductive connection layer.

19. The method for preparing an electron source according to claim 18, wherein The forming of the conductive connection layer on the outer surface of the porous optical fiber so that the electron excitation layer overlaps with the conductive connection layer specifically includes: Forming a core protection layer on the light emitting end of the porous optical fiber, wherein the core protection layer covers one end of the light guiding hole located at the end face of the light emitting end; Forming a conductive material layer covering the core protection layer on the outer surface of the porous optical fiber; Removing the core protection layer and the part of the conductive material layer disposed on the core protection layer to form the conductive connection layer.

20. The method for preparing an electron source according to claim 17, wherein The forming of the electron emission layer on the side wall of the light guiding hole specifically includes: Forming the electron excitation layer by a direct growth method or a coating method.

21. 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 1-16; 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.

22. Use of the electron source according to any one of claims 1-16, characterized in that, The application of the electron source includes at least one of an electron microscope, an electron beam exposure machine, a free electron laser, an electron accelerator, an electron diffraction device, an X-ray tube, and a display.

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