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 is arranged on the end face of the light emitting end of the perforated optical fiber and at least comprises an electron excitation layer, and the electron excitation layer covers one end, located on the end face of the light emitting end, 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 particularly to an electron source, a preparation method thereof, 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 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 material surface to form vacuum electrons. Field emission electron sources mainly select metal tips, and under the action of a strong electric field applied externally, a tip discharge effect is generated. A photoemission electron source uses a metal material as a photocathode, and laser irradiation is used 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 thereof, an electron gun, and an application of the electron source.

[0005] According to a 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 provided on the end face of the light emitting end of the holey optical fiber and including at least an electron excitation layer, the electron excitation layer covering one end of the light guiding hole located on the end face of the light emitting end;

[0008] Wherein, the laser emitted by the holey optical fiber can directly irradiate the electron emission layer, so that the electron excitation layer is excited by the laser emitted by the holey optical fiber and emits electrons;

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

[0010] In one embodiment, 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, a noble gas, or a functional liquid;

[0011] The material of the functional liquid includes a nonlinear optical polymer material.

[0012] In one embodiment, the thickness of the electron excitation layer is less than or equal to 50 nm.

[0013] In one embodiment, the 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°.

[0014] In one embodiment, the electron excitation layer includes at least two two-dimensional materials stacked in sequence along the laser emission direction; or

[0015] The electron excitation layer includes at least two two-dimensional materials with different materials connected to each other in the same plane.

[0016] In one embodiment, the material in the electron excitation layer includes one-dimensional material and zero-dimensional material provided at the end and / or side of the one-dimensional material.

[0017] In one embodiment, the electron excitation layer includes zero-dimensional material and two-dimensional material, and the zero-dimensional material is provided on the surface of the two-dimensional material.

[0018] In one embodiment, the electron excitation layer includes one-dimensional material and two-dimensional material, and the one-dimensional material is provided on the surface of the two-dimensional material.

[0019] In one embodiment, the electron source further includes a conductive connection layer provided on the outer surface of the holey optical fiber;

[0020] The conductive connection layer is electrically connected to the electron excitation layer.

[0021] In one embodiment, the electron excitation layer includes a first part and a second part that are provided on the end face of the light-emitting end of the holey optical fiber and are connected to each other;

[0022] The first part covers one end of the light guiding hole located on the end face of the light-emitting end;

[0023] The second part is arranged around the first part and is electrically connected to the conductive connection layer.

[0024] In one embodiment, the conductive connection layer includes a first conductive part provided on the end face of the light-emitting end of the holey optical fiber, and a second conductive part connected to the first conductive part and provided on the circumferential side surface of the holey optical fiber;

[0025] Wherein, the first conductive part overlaps with the second part of the electron excitation layer.

[0026] In one embodiment, the conductive connection layer includes a first metal layer and a second metal layer stacked;

[0027] The adhesion of the first metal layer is greater than that of the second metal layer.

[0028] In one embodiment, the electron emission layer further includes an auxiliary layer, and the auxiliary layer is stacked on one side of the end face of the electron excitation layer close to the light output end; or,

[0029] The auxiliary layer is stacked on one side of the end face of the electron excitation layer away from the light output end.

[0030] In one embodiment, the auxiliary layer satisfies at least one of the following conditions:

[0031] (1) The auxiliary layer includes at least one of a conductive support layer and a heat dissipation support layer;

[0032] (2) The thickness of the auxiliary layer is 0.1 nm to 10 nm, and the light transmittance is more than 10%.

[0033] In one embodiment, the auxiliary layer includes a conductive support layer, and the conductive support layer is electrically connected to the conductive connection layer.

[0034] 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.

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

[0036] Providing a holey optical fiber; wherein, the holey optical fiber has a light guiding hole;

[0037] Forming an electron emission layer on the end face of the light output end of the holey optical fiber, the electron emission layer at least includes an electron excitation layer, and the electron excitation layer covers one end of the light guiding hole located on the end face of the light output end;

[0038] Wherein, the laser emitted by the holey optical fiber can directly irradiate on the electron emission layer, so that the electron excitation layer is excited by the laser emitted by the holey optical fiber 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 end face of the light output end of the holey optical fiber, the method for preparing the electron source further includes:

[0041] A conductive connection layer is formed on the outer surface of the porous 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 porous 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 end face of the light-emitting end of the porous optical fiber, wherein the core protection layer covers one end of the light-guiding hole located on the end face of the light-emitting end;

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

[0045] The core protection layer and the part of the conductive material layer disposed 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 end face of the light-emitting end of the porous optical fiber specifically includes:

[0047] The electron excitation layer and the end face of the light-emitting end of the porous optical fiber are arranged opposite to each other and parallel to each other in a first direction;

[0048] The optical fiber is driven to move in the first direction to contact the electron excitation layer;

[0049] The electron excitation layer is attached to the end face of the light-emitting end of the porous optical fiber at a preset temperature.

[0050] According to a third aspect of the present application, an electron gun is provided, which includes a housing, a grid, an anode, and the electron source according to any one of the above embodiments;

[0051] 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.

[0052] According to a fourth aspect of the present application, an application of the electron source according to any one of the above embodiments is provided, and the application of the electron source includes at least one of an electron microscope, an electron beam lithography machine, a free electron laser, an electron diffraction device, an electron accelerator, an X-ray tube, and a display.

[0053] In the technical solution of the present application, the laser transmitted in the holey optical fiber can be transmitted toward the end face of the light output end of the holey optical fiber. Since the electron excitation layer is provided on the end face of the light output end of the holey optical fiber, during the process that the laser transmitted in the holey optical fiber is transmitted to the end face of the light output end of the holey optical fiber and exits, 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. 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 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 high melting points, are not easily damaged, 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 high optical nonlinear effects and discrete electron energy levels, 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 can be directly integrated with the optical fiber. The optical fiber transmits the 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 degree. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 FIG. shows a side view of an electron source according to an embodiment of the present application.

[0055] Figure 2 FIG. shows Figure 1 an enlarged schematic view of part A of

[0056] Figure 3 FIG. shows Figure 1 a front view of the electron source of the embodiment shown in

[0057] Figure 4 FIG. shows a circuit block diagram of an electron source and an anode according to an embodiment of the present application.

[0058] Figure 5 FIG. shows a side view of an electron source according to another embodiment of the present application.

[0059] Figure 6 FIG. shows Figure 5 an enlarged schematic view of part B of

[0060] Figure 7 FIG. shows a side view of an electron source according to still another embodiment of the present application.

[0061] Figure 8The flowchart shows the preparation method of an electron source according to an embodiment of the present application.

[0062] Figure 9 The process diagram shows the preparation method of an electron source according to an embodiment of the present application.

[0063] Figure 10 The structural diagram shows an electron gun according to an embodiment of the present application.

[0064] Reference numerals:

[0065] 100, electron source;

[0066] 110, fiber optic with holes; 111, core; 112, annular light guide tube body; k, side wall of light guide hole;

[0067] 1101, light input end; 1102, light output end; 11021, end face;

[0068] 120, electron emission layer; 121, electron excitation layer; 1211, first part; 1212, second part; 122, auxiliary layer;

[0069] 130, conductive connection layer; 131, first conductive part; 132, second conductive part;

[0070] 200, gate; 210, second electron channel; 300, anode; 310, first electron channel;

[0071] 20, temporary substrate

[0072] 30, glass slide with holes;

[0073] 40, annular heating sheet. Detailed implementation manners

[0074] To make the above objects, features, and advantages of the present application more apparent and understandable, the following will describe the detailed implementation manners of the present application with reference to the accompanying drawings. Many specific details are set forth in the following description to facilitate a thorough 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 spirit of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0075] In the description of the present application, it should be understood that if there are 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., the orientation or positional relationship indicated by these terms is based on the orientation or positional relationship shown in the drawings. These are 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 to the present application.

[0076] In addition, if there are terms such as "first" and "second", 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 such feature. In the description of the present application, if there is a term "plurality", the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0077] In the present application, unless otherwise clearly defined and limited, if there are terms such as "mounted", "connected", "coupled", "fixed", etc., these terms should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may 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.

[0078] In the present application, unless otherwise clearly defined and limited, if there is a description such as a first feature being "on" or "under" a second feature, the meaning may 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 may mean that the first feature is directly above or obliquely above the second feature, or simply indicates 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 may be that the first feature is directly below or obliquely below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0079] 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 any, the terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used in this application are only for illustrative purposes and do not represent the only implementation.

[0080] 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, the 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 electron emission properties is limited, and it is impossible to balance the emission efficiency and stability.

[0081] 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 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, the metal material is easily damaged under high-power laser irradiation, affecting the service life of the electron emission layer, and thus affecting the emission efficiency and stability of electrons.

[0082] In the traditional technology, there is also a case where the photoemission electron source excites electrons by the external laser incident on the surface of the metal tip, and 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.

[0083] 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 Q-switching and mode-locking of lasers, or for sensing detection by adjusting the laser spectrum using graphene. 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 graphene saturable absorber mainly utilizes the situation where the light absorption rate (or transmittance) of graphene increases (or decreases) as the incident light power increases, and finally reaches the saturation threshold. It is mainly applied in lasers to generate laser pulses. For example, in the ring fiber resonator of an optical 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. Based on this, it is necessary to provide an electron source that can balance the electron emission efficiency and stability.

[0084] In this application, low-dimensional materials such as zero-dimensional materials, one-dimensional materials, or two-dimensional materials are used 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.

[0085] Figure 1 FIG. shows a schematic structural diagram of an electron source 100 in an embodiment of this application.

[0086] Please refer to Figure 1 and, in combination with referring to Figure 2 and Figure 3 An electron source 100 provided in an embodiment of this application includes a holey optical fiber 110 and an electron emission layer 120.

[0087] The holey optical fiber 110 has a light guiding hole. Among them, the holey optical fiber 110 is a transmission medium for laser light and a carrier for low-dimensional materials. The holey optical fiber 110 can include a hollow holey optical fiber, and the hollow holey optical fiber can be a single-hole or multi-hole hollow optical fiber; of course, the holey optical fiber 110 can also include a solid-core holey optical fiber, and the solid-core holey optical fiber can be a single-hole or multi-hole solid-core optical fiber, which is not specifically limited here. Figure 1 An example of the holey optical fiber 110 being a single-hole hollow optical fiber is given.

[0088] Specifically, as in Figure 1In the illustrated embodiment, a core 111 made of air is provided in the light guiding hole. The perforated 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 can be borosilicate, glass, quartz, etc. More specifically, the perforated optical fiber 110 is a capillary optical fiber.

[0089] The perforated optical fiber 110 has an incident light end 1101 and an end face 11021 of the outgoing light end. 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 perforated optical fiber 110. Among them, the laser source can be a laser.

[0090] Whether it is a hollow perforated optical fiber or a solid perforated optical fiber, the laser emitted by the laser source can be transmitted through the perforated optical fiber 110 to the outgoing light end 1102 of the perforated optical fiber 110.

[0091] An electron emission layer 120 is provided on the end face 11021 of the outgoing light end 1102 of the perforated optical fiber 110, and the electron emission layer 120 at least includes an electron excitation layer 121, and the electron excitation layer 121 covers one end of the light guiding hole located at the end face 11021 of the outgoing light end 1102. The laser emitted by the perforated optical fiber 110 can directly irradiate on the electron emission layer 120, so that the electron excitation layer 121 is excited by the laser emitted by the perforated optical fiber 110 and emits electrons.

[0092] Specifically, in the illustrated embodiment Figure 1 a core 111 made of air is provided in the light guiding hole, and the electron excitation layer 121 covers the core 111 of the perforated optical fiber 110. It can be that the electron excitation layer 121 directly covers the core 111 of the perforated optical fiber 110, or it can be that the electron excitation layer 121 indirectly covers the core 111 of the perforated optical fiber 110, and no specific limitation is made here.

[0093] Among them, the electron excitation layer 121 includes at least one of a zero-dimensional material, a one-dimensional material, and a two-dimensional material.

[0094] The electron excitation layer 121 can include a zero-dimensional material. A zero-dimensional material refers to a material whose size in the three-dimensional spatial scale direction is in the nanometer scale, 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. The zero-dimensional material has typical discrete energy levels. Under the action of laser excitation, electrons are mainly excited by tunneling from the discrete energy levels, so that the electron beam tunneling and emitting from the electron excitation layer 121 has the characteristics of concentrated energy and small energy dispersion.

[0095] 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 output end 1102 of the holey optical fiber 110, it is beneficial for the electrons emitted by the electron source 100 to be efficiently emitted along the extension direction of the holey optical fiber 110. The one-dimensional materials have the characteristics of a small radius of curvature (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.

[0096] The one-dimensional materials can be nanotubes, nanorods or nanowires, nanobelts or coaxial nanocables, etc.

[0097] The nanotubes can be carbon nanotubes. Carbon nanotubes 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 and nitrogen co-doped carbon nanotubes (BCN nanotubes), tungsten disulfide (WS2) nanotubes, molybdenum disulfide (MoS2) nanotubes or titanium dioxide (TiO2) nanotubes, etc.

[0098] 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.

[0099] The nanobelts 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 nanobelts can be oxides, such as tin oxide (SnO) or zinc oxide (ZnO), etc.

[0100] The coaxial nanocables can be graphite / boron nitride (C / BN) coaxial nanocables or silicon carbide / sulfur dioxide (CSi / SiO2) coaxial nanocables, etc.

[0101] 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-emitting end 1102 of the holey optical fiber 110, in this way, it is beneficial for the electrons emitted by the electron source 100 to be efficiently emitted along the extending direction of the holey optical fiber 110. Moreover, 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 material are more discrete, and the energy of the electron beam emitted by tunneling is more concentrated and the energy dispersion is smaller.

[0102] 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 scattering inside the material, ensuring the purity of the emitted electron properties and an extremely narrow pulse width.

[0103] The two-dimensional material can be graphene, transition metal sulfide, two-dimensional perovskite, two-dimensional diamond, boron nitride, etc.

[0104] Taking graphene as an example of the two-dimensional material for illustration, the carbon atoms of 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 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.

[0105] 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.

[0106] Thus, when the electron source 100 is in use, the laser transmitted in the holey optical fiber 110 can be transmitted toward the end face 11021 of the light output end of the holey optical fiber 110. Since the electron excitation layer 121 is provided on the end face 11021 of the light output end of the holey optical fiber 110 and covers one end of the light guiding hole located on the end face 1102 of the light output end 1102, during the process that the laser transmitted in the holey optical fiber 110 propagates to the end face 11021 of the light output end and exits, 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 to 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 holey optical fiber 110 to realize the excitation of electrons, abandoning the complex spatial light coupling structure set due to the introduction of external laser, and also abandoning the high-magnification microscope set to solve the alignment problem of the metal tip, which can reduce the process cost of the electron gun.

[0107] 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 lower 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 excited 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 applicable 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 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 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.

[0108] In addition, the low-dimensional material and the holey 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 applicable to different application scenarios, and does not require a complex optical path, and has characteristics such as small volume and high integration.

[0109] 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 visible light - near-infrared - ultraviolet range. 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 visible light - near-infrared - ultraviolet range, and no specific limitation is made here.

[0110] 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, rare gas, or functional liquid, and the material of the functional liquid includes a nonlinear optical polymer material.

[0111] The light guiding medium can be air, or can be a rare gas or a functional liquid. By using the rare gas or the functional liquid, a nonlinear optical effect can be generated, and thus the light 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 a super broadband supercontinuum spectrum can be generated, which is also beneficial to better exciting the electrons in the electron excitation layer 121 to emit electrons outward.

[0112] In some embodiments, the thickness of the electron excitation layer 121 is less than or equal to 50 nm.

[0113] 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. In this way, it is more beneficial to reduce the process of in-body transmission of the excited electrons in the electron excitation layer 121, and it is more beneficial to improve the electron emission efficiency and emission power. Furthermore, the electron source 100 can be used to realize an electron beam with ultrashort pulses.

[0114] 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°.

[0115] 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. Herein, 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 can be 1, 2, or 3.

[0116] In some embodiments, the axial direction of the one-dimensional material has an included angle with the emission direction of the laser, and the included angle can be a right angle or an acute angle.

[0117] In some embodiments, the electron excitation layer 121 includes at least one layer of two-dimensional material.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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 the characteristics of concentrated energy, small energy dispersion, and high emission efficiency.

[0122] In some embodiments, the electron excitation layer 121 includes zero-dimensional materials and two-dimensional materials, and the zero-dimensional materials are disposed on the surface of the two-dimensional materials.

[0123] 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.

[0124] 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°.

[0125] 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.

[0126] In some embodiments, the zero-dimensional materials, one-dimensional materials, or two-dimensional materials independently include doping elements.

[0127] 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 low-dimensional materials.

[0128] Optionally, the doping element includes at least one of boron, nitrogen, phosphorus, lithium, and potassium.

[0129] 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.

[0130] 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.

[0131] It should be added that the projection of the conductive connection layer 130 on the end face 11021 of the light-emitting end 1102 of the holey optical fiber is staggeredly arranged with the projection of the fiber core 111 on the end face 11021 of the light-emitting end 1102 of the holey optical fiber.

[0132] 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 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.

[0133] Exemplarily, as Figure 4 shown, when the electron source 100 is applied to the electron gun 10, the electron gun 10 further includes an anode 300. The anode 300 has a first electron channel 310 for the electrons emitted from the electron excitation layer 121 to pass through. There is a preset voltage between the anode 300 and the conductive connection layer 130, so that a preset electric field is formed between the anode 300 and the conductive connection layer 130. Thus, 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 there is a preset voltage 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 extension direction of the holey optical fiber 110. In this way, it is beneficial to form a uniform electric field along the extension direction of the holey optical fiber 110 by using the anode 300, and it is more beneficial for the electrons to perform linear acceleration along the extension direction of the holey optical fiber 110 and pass through the first electron channel 310.

[0134] In some embodiments, refer to Figures 1 - 3 The electron excitation layer 121 includes a first part 1211 and a second part 1212 that are disposed on the end face 11021 of the light output end 1102 and are connected to each other. The first part 1211 covers one end of the light guiding hole located on the end face 11021 of the light output end 1102, and the second part 1212 is disposed around the first part 1211 and is electrically connected to the conductive connection layer 130.

[0135] The first part 1211 may directly cover the core 111 of the perforated optical fiber 110, or the first part 1211 may indirectly cover the core 111 of the perforated optical fiber 110, and no specific limitation is made here.

[0136] Specifically, the second part 1212 may be directly in electrical contact with the conductive connection layer 130 to be electrically connected to the conductive connection layer 130; the second part 1212 may also be electrically connected to the conductive connection layer 130 through other conductive structures.

[0137] In this way, by electrically connecting the conductive connection layer 130 to the second part 1212 of the electron excitation layer 121, and combining the second part 1212 disposed around the first part 1211, the conductive connection layer 130 can supplement electrons to the electron excitation layer 121 without affecting the interaction between the laser transmitted in the perforated optical fiber 110 and the electron excitation layer 121, which is beneficial for the electron excitation layer 121 to continuously emit electrons outward under the excitation of the laser.

[0138] In some embodiments, refer to Figure 1 The conductive connection layer 130 includes a first conductive part 131 disposed on the end face 11021 of the light output end 1102, and a second conductive part 132 connected to the first conductive part 131 and disposed on the circumferential side surface of the perforated optical fiber 110. The first conductive part 131 overlaps with the second part 1212 of the electron excitation layer 121.

[0139] In this way, the conductive connection layer 130 can cover more of the perforated optical fiber 110, improve the bonding strength between the conductive connection layer 130 and the optical fiber, and is also beneficial for better using the conductive connection layer 130 to supplement electrons to the electron excitation layer 121.

[0140] In some embodiments, the conductive connection layer 130 includes a first metal layer and a second metal layer that are stacked, and the adhesion of the first metal layer is greater than the adhesion of the second metal layer.

[0141] Exemplarily, the material of the first metal layer is titanium, palladium or chromium, and the material of the second metal layer is gold.

[0142] Thus, by using the first metal layer with higher adhesion, the conductive connection layer 130 can be better adhered to the porous optical fiber 110, improving the bonding strength between the conductive connection layer 130 and the porous optical fiber 110, and also contributing to increasing the service life of the conductive connection layer 130.

[0143] In some embodiments, referring to Figures 5 - 7 , the electron emission layer 120 further includes an auxiliary layer 122, and the auxiliary layer 122 is stacked on one side of the end face 11021 of the electron excitation layer 121 close to the light output end 1102, or referring to Figure 7 , the auxiliary layer 122 is stacked on one side of the end face 11021 of the electron excitation layer 121 far from the light output end 1102. Figures 5 - 7 An example is given in which the auxiliary layer 122 is stacked on one side of the end face 11021 of the electron excitation layer 121 close to the light output end 1102.

[0144] 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 disposed 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 electron excitation layer 121 and the conductive connection layer 130 are electrically conducted through the auxiliary layer 122.

[0145] Optionally, the auxiliary layer 122 includes at least one of a conductive support layer and a heat dissipation support layer.

[0146] 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.

[0147] Optionally, the light transmittance of the auxiliary layer 122 is 10% or more. Specifically, the light transmittance is 10% - 98%. For example, the light transmittance is 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or 98%.

[0148] Optionally, the auxiliary layer 122 includes a conductive support layer, and the conductive support layer is electrically connected to the conductive connection layer 130.

[0149] In some embodiments, referring 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 porous 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.

[0150] In this application, the auxiliary layer 122 is made of a conductive metal, and the laser parameters are controlled to avoid the problem of melting caused by laser irradiation of the conductive metal, ensuring that the auxiliary layer has the functions of support and conduction.

[0151] The auxiliary layer 122 may also include a conductive support layer, such as Figure 5 and Figure 6 As shown, the electron excitation layer 121 is disposed on the end face 11021 of the light output end 1102 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 selected as a non-light-transmitting material, and the auxiliary layer 122 has an annular structure, and the orthographic projection of the auxiliary layer 122 on the end face 11021 of the light output end 1102 is located outside the core 111 of the holey optical fiber 110.

[0152] In this way, on the one hand, the bearing plane of the auxiliary layer 122 can be used to make the electron excitation layer 121 more flatly disposed on the end face 11021 of the light output end 1102, and on the other hand, it will not affect the interaction between the electron excitation layer 121 and the laser transmitted in the holey optical fiber 110, which is beneficial to the formation of an electron beam with concentrated energy and small energy dispersion from the electrons tunneling and emitting from the electron excitation layer 121.

[0153] The auxiliary layer 122 may also include a heat dissipation support layer. Exemplarily, the material of the auxiliary layer 122 can be hexagonal boron nitride. Of course, the material of the auxiliary layer 122 can also be selected as 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 end face 11021 of the light output end 1102. In this way, the heat dissipation efficiency of the electron excitation layer 121 can be increased by using the auxiliary layer 122, enabling the electron excitation layer 121 to emit a larger electron beam current.

[0154] Please refer to Figure 8 , according to the second aspect of this application, a method for preparing an electron source 100 is provided, including the following steps:

[0155] S210. Provide a holey optical fiber 110. Among them, the holey optical fiber 110 has a light guiding hole.

[0156] Optionally, an appropriate length of the holey optical fiber 110 can be intercepted, the end coating 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 a light output end 1102. Forming the light output end 1102 by cutting can make the cross section where the end face 11021 of the light output end 1102 is located relatively flat, which is beneficial to forming a flat electron excitation layer 121 on the end face 11021 of the light output end 1102.

[0157] S220. An electron emission layer 120 is formed on the end face 11021 of the light-emitting end 1102 of the holey optical fiber 110. The electron emission layer 120 includes at least an electron excitation layer 121. The electron excitation layer 121 covers one end of the light guiding hole located on the end face 11021 of the light-emitting end 1102. The electron excitation layer 121 includes at least one of zero-dimensional materials, one-dimensional materials, and two-dimensional materials. The laser emitted by the holey optical fiber 110 can directly irradiate the electron emission layer 120, so that the electron excitation layer 121 is excited by the laser emitted by the holey optical fiber 110 and emits electrons.

[0158] The electron excitation layer 121 can be formed by at least one of dry transfer, wet transfer, and direct growth.

[0159] In some embodiments, the electron excitation layer 121 is prepared by dry transfer. The preparation method includes: transferring zero-dimensional materials, one-dimensional materials, and / or two-dimensional materials to a tape by mechanical exfoliation, and transferring the zero-dimensional materials, one-dimensional materials, and / or two-dimensional materials to the end face 11021 of the light-emitting end 1102 of the holey optical fiber 110.

[0160] Taking two-dimensional materials as an example, the preparation process of forming the electron excitation layer 121 by dry transfer is as follows:

[0161] (1) The two-dimensional material can be thinned by mechanical exfoliation until an electron excitation layer 121 with a preset thickness is formed. Specifically, the two-dimensional material is adhered to a highly viscous tape A, and a low-viscosity tape B can be used to mechanically exfoliate along the crystal cleavage plane of the two-dimensional material repeatedly until an electron excitation layer 121 with a preset thickness is formed.

[0162] (2) Transfer the electron excitation layer 121 with the preset thickness to a temporary substrate 20, and remove the tape B on the electron excitation layer 121. Specifically, the tape B can be melted by heating to peel the tape B from the electron excitation layer 121.

[0163] (3) Transfer the electron excitation layer 121 on the temporary substrate 20 to the end face 11021 of the light-emitting end 1102 of the holey optical fiber 110.

[0164] Optionally, the electron excitation layer 121 is selected as a two-dimensional material, and the material of the temporary substrate 20 can be selected as a polycarbonate propylene film.

[0165] Of course, the present application is not limited thereto. The dry transfer method can also be combined with the direct growth method (such as chemical vapor deposition). For example, an electron excitation layer 121 with a preset thickness is grown on the substrate to be peeled off, and then the electron excitation layer 121 is transferred from the substrate to be peeled off to the temporary substrate 20 by means of acid etching to remove the substrate to be peeled off or manual tearing, and then the electron excitation layer 121 on the temporary substrate 20 is transferred to the end face 11021 of the light-emitting end 1102 of the porous optical fiber 110. Among them, the substrate to be peeled off can be a metal or other material that can be etched by acid or torn by hand.

[0166] In some other embodiments, the electron excitation layer 121 is prepared by means of wet transfer. The preparation method 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 end face 11021 of the light-emitting end 1102 of the porous 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 end face 11021 of the light-emitting end 1102 of the porous optical fiber 110.

[0167] In still some other embodiments, the electron excitation layer 121 is prepared by means of direct growth. The preparation method includes: directly preparing the electron excitation layer 121 on the end face 11021 of the light-emitting end 1102 of the porous optical fiber 110 by at least one of chemical vapor deposition, physical vapor deposition, molecular beam epitaxy and liquid filling.

[0168] Optionally, before or after forming the electron emission layer 120 on the end face 11021 of the light-emitting end 1102 of the porous optical fiber 110, the preparation method of the electron source 100 further includes:

[0169] S230. Form a conductive connection layer 130 on the outer surface of the porous optical fiber 110 so that the conductive connection layer 130 overlaps with the electron excitation layer 121.

[0170] It should be noted that the outer surface of the porous optical fiber 110 includes the circumferential side surface of the porous optical fiber 110 and the end face 11021 of the light-emitting end 1102 of the porous optical fiber 110.

[0171] 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 light.

[0172] Optionally, a conductive connection layer 130 is formed on the outer surface of the holey optical fiber 110 so that the conductive connection layer 130 overlaps with the electron excitation layer 121. Specifically, it includes:

[0173] S231. A core protection layer is formed on the end face 11021 of the light output end 1102 of the holey optical fiber 110, and the core protection layer covers one end of the light guiding hole located on the end face 11021 of the light output end 1102.

[0174] It can be understood that the core protection layer covers the core 111 of the holey optical fiber 110. It can be that the core protection layer directly covers the core 111 of the holey optical fiber 110, or it can be that the core protection layer indirectly covers the core 111 of the holey optical fiber 110, and no specific limitation is made here.

[0175] Optionally, a polymer microsphere solution can be coated on the end face 11021 of the light output end 1102 of the holey optical fiber 110 to form a core protection layer covering the core 111. Exemplarily, the polymer microsphere solution is a polymethyl methacrylate suspension.

[0176] S232. A conductive material layer covering the core protection layer is formed on the outer surface of the holey optical fiber 110.

[0177] 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 holey optical fiber 110.

[0178] S233. 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 130.

[0179] Optionally, a solvent that can dissolve the core protection layer and does not interact with the conductive material layer can be used to remove the core protection layer. Specifically, the light output end 1102 of the holey optical fiber 110 can be soaked in acetone so that the core protection layer (polymer microspheres) dissolves, and the part of the conductive material layer provided on the core protection layer (part of the metal coating) flakes off to obtain the conductive connection layer 130.

[0180] It can be understood that the core protection layer can be used to stagger the orthographic projection of the conductive connection layer 130 on the end face 11021 of the light output end 1102 and the orthographic projection of the core 111 of the holey optical fiber 110 on the end face 11021 of the light output end 1102, so that the laser transmitted in the core 111 of the holey optical fiber 110 can better interact with the electron excitation layer 121 provided on the end face 11021 of the light output end 1102.

[0181] In some embodiments, the step S220 of forming the electron emission layer 120 on the end face 11021 of the light-emitting end 1102 of the porous optical fiber 110 specifically includes the following steps. Specifically, the specific steps of transferring the electron excitation layer 121 on the temporary substrate 20 to the end face 11021 of the light-emitting end 1102 of the porous optical fiber 110 are as follows:

[0182] S221. Oppositely arrange the electron excitation layer 121 and the end face 11021 of the light-emitting end 1102 of the porous optical fiber 110 along the first direction F1 and set them parallel to each other.

[0183] Specifically, observe the end face 11021 of the light-emitting end 1102 of the porous optical fiber 110 and the electron excitation layer 121 under a microscope, and oppositely arrange the electron excitation layer 121 and the end face 11021 of the light-emitting end 1102 of the porous optical fiber 110 along the first direction F1 and set them parallel to each other, and make the center connection line of the two extend along the first direction F1.

[0184] S222. Drive the porous optical fiber 110 to move along the first direction F1 to contact the electron excitation layer 121.

[0185] S223. Make the electron excitation layer 121 adhere to the end face 11021 of the light-emitting end 1102 of the porous optical fiber 110 at a preset temperature.

[0186] In this way, the center of the electron excitation layer 121 can be aligned with the center of the end face 11021 of the light-emitting end 1102 of the porous optical fiber 110 by using a microscope, and the two are adhered to each other at a certain temperature, so that the electron excitation layer 121 and the end face 11021 of the light-emitting end 1102 of the porous optical fiber 110 can be closely adhered under the action of van der Waals force, improving the bonding fastness of the electron excitation layer 121 on the porous optical fiber 110, and also facilitating the electron excitation layer 121 to completely cover the core 111 of the porous optical fiber 110, so that the laser transmitted by the core 111 can better interact with the electron excitation layer 121.

[0187] In some specific embodiments, the step S220 of forming the electron emission layer 120 on the end face 11021 of the light-emitting end 1102 of the porous optical fiber 110 specifically includes the following steps. Specifically, the specific steps of transferring the electron excitation layer 121 on the temporary substrate 20 to the end face 11021 of the light-emitting end 1102 of the porous optical fiber 110 are as follows:

[0188] S2201. Please refer to Figure 9, attach a circular heating sheet 40 to the back of the perforated slide 30 of the microscope, fix the temporary substrate 20 with the electron excitation layer 121 to the bottom side of the circular heating sheet 40 (the temporary substrate 20 can be fixed to the bottom side of the circular heating sheet 40 by an adhesive fixing method), and arrange the electron excitation layer 121 on the temporary substrate 20 facing downwards, and fix the perforated optical fiber 110 below the electron excitation layer 121, so that the central axis of the objective lens of the microscope, the central axis of the perforated slide 30, the central axis of the circular heating sheet 40, the center of the electron excitation layer 121 and the center of the fiber core 111 coincide, and the objective lens of the microscope, the perforated slide 30, the circular heating sheet 40, the electron excitation layer 121 and the optical fiber 110 are arranged in sequence from top to bottom.

[0189] Optionally, a fixture can be used to fix the perforated optical fiber 110 on the moving platform, and arrange the end face 11021 of the light-emitting end 1102 of the perforated optical fiber 110 facing upwards. The moving platform is used to adjust the position of the perforated optical fiber 110 along the first direction F1, and to adjust the angle of the end face 11021 of the light-emitting end 1102 of the perforated optical fiber 110 relative to the horizontal plane to make it horizontally set.

[0190] Optionally, the fixture can be a pneumatic gripper or an electric gripper.

[0191] Optionally, the moving platform can be a six-degree-of-freedom platform. The moving platform can also include a linear drive mechanism and a rotary drive mechanism connected to the linear drive mechanism. The output end of the rotary drive mechanism is connected to the fixture to drive the fixture and the perforated optical fiber 110 clamped by the fixture to rotate around an axis parallel to the horizontal plane, so that the end face 11021 of the light-emitting end 1102 is horizontally set. The linear drive mechanism is used to drive the rotary drive mechanism, the fixture and the perforated optical fiber 110 to move along the first direction F1.

[0192] Among them, the linear drive mechanism can be a motor or a cylinder, and the rotary drive mechanism can be a motor or a rotary cylinder.

[0193] S2202. Observe the end face 11021 of the light-emitting end 1102 of the perforated optical fiber 110 and the electron excitation layer 121 under the microscope, and arrange the electron excitation layer 121 and the end face 11021 of the light-emitting end 1102 of the perforated optical fiber 110 to be relatively arranged and parallel to each other along the first direction F1, and make the center connection line of the two extend along the first direction F1.

[0194] The central alignment of the end face 11021 of the light-emitting end 1102 and the electron excitation layer 121 can be completed with the aid of the microscope.

[0195] S2203. Connect the external power supply to the annular heating sheet 40 to apply a first preset voltage to the annular heating sheet 40, and preheat the electron excitation layer 121 on the temporary substrate 20 (heat it to the preheating temperature), which is beneficial for the electron excitation layer 121 to be more flat.

[0196] Optionally, the first preset voltage is 1V - 1.5V, and the preheating temperature is 50 - 60 °C.

[0197] S2204. Drive the perforated optical fiber 110 to move along the first direction F1 to contact the electron excitation layer 121. It is possible to make the end face 11021 of the light output end 1102 contact the electron excitation layer 121 to produce Newton's rings.

[0198] S2205. At a preset temperature, make the electron excitation layer 121 closely adhere to the end face 11021 of the light output end 1102 of the perforated optical fiber 110. Specifically, apply a second preset voltage to the annular heating sheet 40, and heat the electron excitation layer 121 on the temporary substrate 20 to the preset temperature, which is beneficial for the electron excitation layer 121 to be more closely arranged on the end face 11021 of the light output end 1102.

[0199] Optionally, the second preset voltage is 2.5V - 4V, and the preset temperature is 90 - 100 °C.

[0200] S2206. Remove the temporary substrate 20. The temporary substrate 20 can be removed by a method combining melting heating and solvent immersion. Specifically, apply a third preset voltage to the annular heating sheet 40, and heat the temporary substrate 20 to the melting temperature until it melts. It should be noted that the melting point of the electron excitation layer 121 is much higher than that of the temporary substrate 20.

[0201] Optionally, the third preset voltage is 5.5V - 6V, and the melting temperature is 130 - 150 °C.

[0202] After the electron excitation layer 121 is closely arranged on the end face 11021 of the light output end 1102, the part of the temporary substrate 20 in contact with the annular heating sheet 40 can be melted by melting heating, and the electron excitation layer 121 can be separated from the annular heating sheet 40 and closely adhere to the end face 11021 of the perforated optical fiber 110, which is convenient for subsequent removal of the temporary substrate 20 remaining on the electron excitation layer 121. The part of the temporary substrate 20 not in contact with the annular heating sheet 40 still remains on the electron excitation layer 121. The perforated optical fiber 110 can be taken off the fixture and the light output end 1102 of the perforated optical fiber 110 can be immersed in acetone to dissolve the remaining temporary substrate 20 on the electron excitation layer 121 and completely remove the temporary substrate 20.

[0203] Please refer to Figure 10, 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 of the above embodiments.

[0204] The electron source 100 is fixed inside the housing. A grid 200 and an anode 300 are sequentially arranged on the electron-emitting side of the electron source 100.

[0205] 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 shoot out for use.

[0206] 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 electron accelerator, an electron diffraction device, an X-ray tube, and a display.

[0207] Hereinafter, the implementation schemes of the present invention will be described in detail in conjunction with 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.

[0208] Embodiment 1

[0209] Please refer to Figures 1 - 3, the porous optical fiber 110 is a capillary optical fiber. The diameter of the core 111 of the porous optical fiber 110 is 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. A conductive connection layer 130 is formed on the circumferential side surface and the end surface 11021 of the light output end 1102 of the porous optical fiber 110. The conductive connection layer 130 includes 4 nm of titanium and 50 nm of gold stacked. Among them, the core 111 at the end surface 11021 of the light output end is exposed (without being covered by the conductive connection layer 130). The electron excitation layer 121 is made of graphene two-dimensional material (the thickness of the graphene two-dimensional material is 50 nm). The shape of the electron excitation layer 121 is not limited and can be polygonal, circular, elliptical, etc. In this embodiment, the shape of the electron excitation layer 121 is quadrilateral. The electron excitation layer 121 is arranged on the end surface 11021 of the light output end of the porous optical fiber 110 and completely covers the core 111 of the porous optical fiber 110. Optionally, the side length of the electron excitation layer 121 is 30 - 60 μm (much larger than the diameter of the core 111). In this embodiment, the side length of the electron excitation layer 121 is 30 μm.

[0210] Example 2

[0211] Please refer to Figure 5 and Figure 6 , the porous optical fiber 110 is a capillary optical fiber. The diameter of the core 111 of the porous optical fiber 110 is 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 5 nm of titanium and 60 nm of gold stacked on the porous optical fiber 110. Among them, the core 111 at the end surface 11021 of the light output end is exposed (without being covered by the conductive connection layer 130). First, a 100 - nm - thick hexagonal boron nitride thin film is covered on the end surface 11021 of the light output end, and then the electron excitation layer 121 is formed on the hexagonal boron nitride thin film. Among them, the electron excitation layer 121 is made of graphene two - dimensional material (the number of layers of the graphene two - dimensional material is 6 layers, and the thickness is 2.04 nm). The electron excitation layer 121 is arranged on the end surface 11021 of the light output end of the porous optical fiber 110 and completely covers the core 111 of the porous optical fiber 110. Exemplarily, along the radial direction of the porous optical fiber 110, the size of the electron excitation layer 121 is 60 μm (much larger than the diameter of the core 111).

[0212] Hexagonal boron nitride is an insulator, does not absorb light, can provide an atomically flat surface, can improve the flatness of the electron excitation layer 121, and can also increase the heat dissipation efficiency of the electron excitation layer 121, enabling the electron excitation layer 121 to emit a larger electron beam current.

[0213] Example 3

[0214] Please refer toFigure 7 On the end face 11021 of the light-emitting end 1102 of the porous optical fiber 110 and on the circumferential side surface of the porous optical fiber 110, a conductive connection layer 130 is formed. Then, an auxiliary layer 122 with a thickness of 10 nm and a material of gold is deposited and grown on the end face 11021 of the light-emitting end 1102 of the porous optical fiber 110. 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, forming an electron excitation layer 121. Among them, the auxiliary layer 122 is electrically connected to the conductive connection layer 130, and the obtained electron source 100 is obtained.

[0215] Comparative Example 1

[0216] An electron source is prepared according to the structure of Example 1, and the only difference is that the electron excitation layer in Example 1 is replaced with a gold layer with a thickness of 100 nm, and the preparation method of the gold layer is obtained by deposition.

[0217] Comparative Example 2

[0218] An electron source is prepared according to the structure of Example 1, and the only difference is that the electron excitation layer in Example 1 is replaced with a gold layer with a thickness of 2.04 nm (the same thickness as the graphene thickness).

[0219] As Figure 10 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:

[0220] Table 1

[0221] Number Stability Lifespan Operating vacuum Example 1 2％ 2000h 10 Pa Example 2 1％ 2000h 10 Pa Example 3 3％ 1000 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]]>

[0222] 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 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 better stability, longer lifetime, and better working vacuum degree.

[0223] 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.

[0224] 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 excited electrons can be directly emitted into the vacuum without internal scattering within the material, making them 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 integration. In addition, low-dimensional materials have no dangling bonds, are stable, have high melting points, and are not easily damaged, making them suitable for high-power-excited large-beam electron sources. Integrating low-dimensional materials with 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 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. It can be applied to different application scenarios without the need to provide a complex optical path, and has the characteristics of small size and high integration. When integrated with other devices, it can achieve stable integration without the need for invasive modification of vacuum electronic devices.

[0225] In this application, since the size of the electron excitation layer 121 is in the nanometer range, the process of in-body transmission of the excited electrons within the electron excitation layer 121 can be reduced, which is beneficial to improving the electron emission efficiency and emission power. Furthermore, an electron beam with ultrashort pulses can be realized using the electron source 100. The electron source 100 in this application uses low-dimensional materials as the electron-emitting materials. Due to the high optical nonlinear effect and discrete electron energy levels of low-dimensional materials, the laser can better interact with the electron excitation layer 121 to generate energy resonance and excite the electrons within the electron excitation layer 121. These electrons are excited and escape into the vacuum to form an electron beam, and the electron beam tunneling and emitting from the electron excitation layer 121 have the characteristics of concentrated energy and small energy dispersion. In addition, the electron excitation layer 121 with a nanometer-scale size does not affect the transmission mode of the holey optical fiber 110, so that the transmission mode of the electron source 100 is mainly determined by the holey optical fiber 110, enabling the electrons emitted by the electron source 100 to be emitted efficiently along the extension direction of the holey optical fiber 110, which provides great convenience for controlling the transmission mode of the electron source 100. Moreover, the electron source 100 abandons the complex spatial light coupling structure set due to the introduction of external laser light, facilitating assembly into the housing of the electron gun; it 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.

[0226] 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 as falling within the scope described in this specification.

[0227] The above-described embodiments merely represent several implementation manners of the present application. The description 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 belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. An electron source, characterized in that, Comprising: A holey optical fiber having a light guiding hole; And An electron emission layer provided on the end face of the light output end of the holey optical fiber, and at least including an electron excitation layer, the electron excitation layer covering one end of the light guiding hole located at the end face of the light output end; Wherein, the laser emitted by the holey optical fiber can directly irradiate on the electron emission layer, so that the electron excitation layer is excited by the laser emitted by the holey optical fiber 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, wherein The holey optical fiber includes a hollow holey optical fiber, a light guiding medium is provided in the light guiding hole, the light guiding medium includes air, a noble gas or a functional liquid; the material of the functional liquid includes a nonlinear optical polymer material.

3. The electron source according to claim 1, wherein The thickness of the electron excitation layer is less than or equal to 50 nm.

4. The electron source according to claim 1, wherein 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°.

5. 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.

6. 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.

7. 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 provided on the surface of the two-dimensional material.

8. 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.

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

10. The electron source according to claim 9, characterized in that, The electron excitation layer includes a first part and a second part provided on the end face of the light output end of the holey optical fiber and connected to each other; The first part covers one end of the light guiding hole located at the end face of the light output end; The second part is arranged around the first part and is electrically connected to 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 on the end face of the light output end of the holey optical fiber, and a second conductive part connected to the first conductive part and provided on the circumferential side face of the holey optical fiber; Wherein, the first conductive part overlaps with the second part of the electron excitation layer.

12. The electron source according to claim 9, 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.

13. The electron source according to claim 9, wherein The electron emission layer further includes an auxiliary layer, the auxiliary layer is stacked on one side of the electron excitation layer close to the end face of the light output end; or, The auxiliary layer is stacked on one side of the electron excitation layer far from the end face of the light output end.

14. The electron source according to claim 13, characterized in that, 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%.

15. The electron source according to claim 13, wherein, The auxiliary layer includes a conductive support layer, and the conductive support layer is electrically connected to the conductive connection layer.

16. The electron source according to claim 13, wherein The auxiliary layer includes a conductive support layer, and 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.

17. A method for preparing an electron source, characterized in that, Including: Providing a holey optical fiber; wherein, the holey optical fiber has a light guiding hole; Forming an electron emission layer on the end face of the light output end of the holey optical fiber, and the electron emission layer at least includes an electron excitation layer, and the electron excitation layer covers one end of the light guiding hole located on the end face of the light output end; Wherein, the laser emitted by the holey optical fiber can directly irradiate on the electron emission layer, so that the electron excitation layer is excited by the laser emitted by the holey optical fiber 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.

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

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

20. The method for preparing an electron source according to claim 17, wherein, The forming an electron emission layer on the end face of the light output end of the holey optical fiber specifically includes: Arranging the electron excitation layer and the end face of the light output end of the holey optical fiber opposite to each other and parallel to each other in a first direction; Driving the optical fiber to move in the first direction to contact the electron excitation layer; Making the electron excitation layer adhere to the end face of the light output end of the holey optical fiber at a preset temperature.

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 applications of the electron source include 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.

Images