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

Abstract

The invention relates to an electron source, a preparation method of the electron source, an electron gun and application of the electron source. The electron source comprises an optical fiber and an electron emission layer, the optical fiber comprises a fiber core used for transmitting laser and a wrapping layer wrapping the fiber core, and the end face of the light outlet end of the optical fiber and the extending direction of the fiber core are arranged at an angle. The electron emission layer is arranged on the end face of the light emitting end of the optical fiber, and the electron emission layer at least comprises an electron excitation layer covering the fiber core. The electron excitation layer comprises at least one of a zero-dimensional material, a one-dimensional material and a two-dimensional material. Low-dimensional materials such as zero-dimensional materials, one-dimensional materials or two-dimensional materials are adopted as materials of the electron excitation layer, the low-dimensional materials have the atomic-scale thickness, back-incident electrons can be emitted without in-vivo transmission, and the electron emission efficiency is high; and the low-dimensional material has the characteristics of no dangling bond, stable property, high melting point, difficulty in damage, good stability, long service life and the like.

Description

Technical Field

[0001] The present application relates to the technical field of electron sources, and in particular, to an electron source, a preparation method of the electron source, an electron gun, and an application of the electron source. Background Art

[0002] An electron source is a device that generates vacuum electrons. Traditional electron sources are mainly classified into thermionic 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. Under the action of a strong electric field applied from the outside, a tip discharge effect is generated. A photoemission electron source uses a metal material as a photocathode, and uses laser irradiation to excite the photocathode material to generate electrons.

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

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

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

[0006] An optical fiber, including a core for transmitting laser and a cladding layer wrapped around the core, wherein an end face of the light-emitting end of the optical fiber is disposed at an angle with respect to the extending direction of the core; and

[0007] An electron emission layer, disposed on the end face of the light-emitting end of the optical fiber, and the electron emission layer at least includes an electron excitation layer covering the core; the laser emitted from the core can directly irradiate the electron emission layer, so that the electron excitation layer is excited by the laser emitted from the core and emits electrons;

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

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

[0010] In one embodiment, the axial direction of the one-dimensional material in the electron excitation layer forms an angle of 0 to 90° with the emission direction of the emitted laser.

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

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

[0013] In one embodiment, the material in the electron excitation layer includes a one-dimensional material and a zero-dimensional material disposed at the end and / or side of the one-dimensional material.

[0014] In one embodiment, the electron excitation layer includes a zero-dimensional material and a two-dimensional material, and the zero-dimensional material is disposed on the surface of the two-dimensional material.

[0015] In one embodiment, the electron excitation layer includes a one-dimensional material and a two-dimensional material, and the one-dimensional material is disposed on the surface of the two-dimensional material.

[0016] In one embodiment, the electron source further includes a conductive connection layer, and the conductive connection layer is disposed at least on the end face of the light-emitting end of the optical fiber and is electrically connected to the electron excitation layer.

[0017] In one embodiment, the electron excitation layer includes a first part and a second part disposed on the end face of the light-emitting end and connected to each other, the first part covers the core of the optical fiber, the second part is disposed around the first part, and is electrically connected to the conductive connection layer.

[0018] In one embodiment, the conductive connection layer includes a first conductive part disposed on the end face of the light-emitting end, and a second conductive part disposed on the circumferential side surface of the optical fiber;

[0019] wherein, the first conductive part is connected to the second conductive part, and the first conductive part overlaps with the second part of the electron excitation layer.

[0020] In one embodiment, the conductive connection layer includes a first metal layer and a second metal layer stacked;

[0021] the adhesion of the first metal layer is greater than the adhesion of the second metal layer.

[0022] 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-emitting end; or,

[0023] the auxiliary layer is stacked on one side of the end face of the electron excitation layer away from the light-emitting end.

[0024] In one embodiment, the auxiliary layer satisfies at least one of the following conditions:

[0025] (1) The auxiliary layer includes at least one of a conductive support layer and a heat dissipation support layer;

[0026] (2) The thickness of the auxiliary layer is 0.1 nm - 100 nm, and the light transmittance is more than 10%.

[0027] In one embodiment, the auxiliary layer includes a conductive support layer, and the conductive support layer is electrically connected to the conductive connection layer.

[0028] In one embodiment, the auxiliary layer includes a conductive support layer, the material of the conductive support layer includes a conductive metal, the laser wavelength in the optical fiber is 200 nm to 10 μm, the pulse power is 1 nw to 1 w, and the repetition frequency is 0 Hz to 10 GHz.

[0029] According to the second aspect of the present application, a method for preparing an electron source is provided, including:

[0030] Providing an optical fiber; wherein, the optical fiber includes a core for transmitting laser and a cladding layer wrapped around the core, and the end face of the light-emitting end of the optical fiber is arranged at an angle with the extending direction of the core;

[0031] Forming an electron emission layer on the end face of the light-emitting end of the optical fiber;

[0032] Wherein, the electron emission layer at least includes an electron excitation layer covering the core, and the laser emitted from the core directly irradiates on the electron emission layer, so that the electron excitation layer is excited by the laser emitted from the core and emits electrons; the electron excitation layer includes at least one of a zero-dimensional material, a one-dimensional material, and a two-dimensional material.

[0033] In one embodiment, before or after forming the electron emission layer on the end face of the light-emitting end of the optical fiber, the method for preparing the electron source further includes:

[0034] Forming a conductive connection layer on the end face of the light-emitting end of the optical fiber, so that the conductive connection layer overlaps with the electron excitation layer.

[0035] In one embodiment, forming the conductive connection layer on the end face of the light-emitting end of the optical fiber so that the conductive connection layer overlaps with the electron excitation layer specifically includes:

[0036] Forming a core protection layer on the end face of the light-emitting end of the optical fiber, and the core protection layer covers the core of the optical fiber;

[0037] Forming a conductive material layer covering the core protection layer on the optical fiber;

[0038] Remove the core protective layer and the part of the conductive material layer disposed on the core protective layer to form the conductive connection layer.

[0039] In one embodiment, forming an electron emission layer on the end face of the light-emitting end of the optical fiber specifically includes:

[0040] Dispose the electron excitation layer opposite to and parallel to the end face of the light-emitting end of the optical fiber along a first direction;

[0041] Drive the optical fiber to move along the first direction to contact the electron excitation layer;

[0042] Attach the electron excitation layer to the end face of the light-emitting end of the optical fiber at a preset temperature.

[0043] According to a third aspect of the present application, an electron gun is provided. The electron gun includes a housing, a grid, an anode, and the electron source according to any one of the above embodiments;

[0044] 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.

[0045] 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. 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 accelerator, an electron diffraction device, an X-ray tube, and a display.

[0046] In the technical solution of the present application, when the electron source is in use, the laser can be transmitted along the core of the optical fiber, so that the laser transmitted in the core can propagate to the light-emitting surface and exit, and interact with the electron excitation layer, so that the electrons in the electron excitation layer absorb the photons of the laser and undergo an energy transition to escape outside the electron excitation layer, 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 an atomic-level thickness, and the back-incident electrons can be emitted without passing through in-body transmission, and the electron emission efficiency is high; moreover, the low-dimensional materials have no dangling bonds, are stable in nature and have a high melting point, are not easily damaged, and can be applied to high-power excitation scenarios, and have characteristics such as good stability and high service life; in addition, the low-dimensional materials also have a high optical nonlinear effect and a rich electron bandgap, enabling the laser to better interact with the electron excitation layer 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, 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. Description of the Drawings

[0047] Figure 1 Shows a side view of the electron source according to an embodiment of the present application.

[0048] Figure 2 Shows an end view of the electron source according to an embodiment of the present application.

[0049] Figure 3 Shows a circuit block diagram of the electron source and the anode according to an embodiment of the present application.

[0050] Figure 4 Shows a side view of the electron source according to another embodiment of the present application.

[0051] Figure 5 Shows Figure 4 An enlarged schematic view of part A of

[0052] Figure 6 Shows a schematic flow chart of the preparation method of the electron source according to an embodiment of the present application.

[0053] Figure 7 Shows a schematic structural diagram of an optical fiber, a fixture and a moving platform according to an embodiment of the present application.

[0054] Figure 8 Shows a schematic process diagram of the preparation method of the electron source according to an embodiment of the present application.

[0055] Figure 9 The structural schematic diagram of an electron gun according to an embodiment of the present application is shown.

[0056] Reference numerals:

[0057] 10. Electron gun;

[0058] 100. Electron source;

[0059] 110. Optical fiber; 111. Core; 112. Cladding; 1101. Light incident end; 1102. Light output end; 11021. End face;

[0060] 120. Electron emission layer; 121. Electron excitation layer; 1211. First part; 1212. Second part; 122. Auxiliary layer;

[0061] 130. Conductive connection layer; 131. First conductive part; 132. Second conductive part;

[0062] 200. Gate; 210. Second electron channel;

[0063] 300. Anode; 310. First electron channel;

[0064] 20. Temporary substrate

[0065] 30. Perforated glass slide;

[0066] 40. Annular heating sheet;

[0067] 50. Fixture;

[0068] 60. Moving platform; 61. Linear drive mechanism; 62. Rotary drive mechanism. Detailed implementation manners

[0069] In order to make the above objects, features and advantages of the present application more obvious 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 in order to fully understand the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0070] 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 thus should not be construed as a limitation on the present application.

[0071] 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 and clearly defined.

[0072] In the present application, unless otherwise clearly specified and limited, if there are terms such as "installation", "connection", "coupling", "fixation", 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.

[0073] In the present application, unless otherwise clearly specified 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 indirectly in 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 merely indicates that the first feature has a higher horizontal height 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 merely indicates that the first feature has a lower horizontal height than the second feature.

[0074] 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 the purpose of illustration and do not represent the only implementation.

[0075] 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 externally, 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 low brightness and poor coherence. The electron beam of the field emission electron source has high brightness and good coherence, but has high requirements for vacuum degree and is very sensitive to vibration. 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.

[0076] 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 more than 50 nm, even reaching hundreds of nanometers. However, the inventors of this application have found through research that the electron emission layer made of metal materials has a relatively large thickness, and the distance between the bottom layer directly interacting with the laser and the surface layer for electron emission is relatively far (50 nm to hundreds of nanometers). During the process of electrons excited from the bottom layer passing through the electron emission layer, they are easily affected by metal lattice scattering, thereby affecting the emission efficiency. Moreover, metal materials are prone to damage under high-power laser irradiation, affecting the service life of the electron emission layer, and thus affecting the emission efficiency and stability of electrons.

[0077] In the traditional technology, there is also a case where the photoemission electron source excites electrons by an external laser incident on the surface of a 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, and the system is sensitive to vibration and the electron emission beam current is unstable.

[0078] In addition, in traditional technologies, graphene is used as a saturable absorber. Graphene has broadband saturable absorption characteristics and a fast recovery time, and is used in the Q-switching and mode-locking of lasers, or the laser spectrum is adjusted by graphene to achieve sensing detection. However, there are obvious differences between graphene laser regulation and graphene electron emission. Graphene electron emission is based on the photoelectric effect, while graphene laser regulation is based on the principle of light absorption. For the graphene saturable absorber described above, it mainly utilizes the situation where the light absorption rate (or transmittance) of graphene increases (or decreases) with the increase of the incident light power and finally reaches the saturation threshold. It is mainly applied in lasers to generate laser pulses. For example, in the ring fiber resonator of a fiber laser, when the light power passing through the graphene saturable absorber exceeds its saturation absorption threshold during the circulation of light in the resonator, due to the saturable absorption effect, the light intensity in the cavity will instantaneously drop below the saturation absorption threshold, and this part of the dropped light energy is output in the form of pulses from the optical splitter of the cavity.

[0079] Based on this, it is necessary to provide an electron source that can take into account both electron emission efficiency and stability.

[0080] In this application, low-dimensional materials such as zero-dimensional materials, one-dimensional materials, or two-dimensional materials are used as the materials of 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.

[0081] Figure 1 The structural schematic diagram of an electron source 100 in an embodiment of this application is shown.

[0082] Please refer to Figure 1 and, in combination with referring to Figure 2 According to the first aspect of this application, an electron source 100 is provided, including an optical fiber 110 and an electron emission layer 120.

[0083] The optical fiber 110 includes a core 111 for transmitting laser light and a cladding layer 112 wrapped around the core 111. The refractive index of the cladding layer 112 is lower than that of the core 111. Therefore, the laser light can be confined in the core 111 by using the cladding layer 112 for propagation. A coating layer is also provided on the outer surface of the cladding layer 112 to protect the cladding layer 112 and the core 111.

[0084] The optical fiber 110 has a light incident end 1101 and a light output end 1102. The light incident 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 core 111 of the optical fiber 110. The end face 11021 of the light output end 1102 of the optical fiber 110 is arranged at an angle α with the extending direction of the core 111. Among them, the laser source can be a laser. The optical fiber 110 is a transmission medium of laser and a carrier of low-dimensional materials. The optical fiber 110 can be a single-mode optical fiber, a multi-mode optical fiber, a polarization-maintaining optical fiber, a multi-core optical fiber, etc. The angle α is selected between 0 and 90 degrees.

[0085] The electron emission layer 120 is arranged on the end face 11021 of the light output end 1102 of the optical fiber 110, and the electron emission layer 120 at least includes an electron excitation layer 121 covering the core 111. The laser emitted from the core 111 of the optical fiber 110 directly irradiates on the electron emission layer 120, so that the electron excitation layer 121 is excited by the laser emitted from the core 111 and emits electrons. Among them, the electron excitation layer 121 includes at least one of zero-dimensional materials, one-dimensional materials and two-dimensional materials.

[0086] The electron excitation layer 121 can directly cover the core 111 of the optical fiber 110 or indirectly cover the core 111 of the optical fiber 110, and no specific limitation is made here.

[0087] The electron excitation layer 121 can include zero-dimensional materials. Zero-dimensional materials refer to materials whose dimensions in the three-dimensional space scale direction are in the nanoscale, such as nanoparticles, atomic clusters and quantum dots, etc., which are generally composed of a small number of atoms and molecules. There are many zero-dimensional carbon nanomaterials, such as carbon black, nanodiamond, diamond color center, nanometer fullerene C 60 or carbon-coated nanometal particles, etc. Zero-dimensional materials have typical discrete energy levels. Under the action of laser excitation, electrons are mainly 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 energy concentration and small energy dispersion.

[0088] The electron excitation layer 121 can also include one-dimensional materials. The electrons in one-dimensional materials can be transmitted along the linear chain of the one-dimensional materials. Combining with the fact that the electron excitation layer 121 is arranged on the end face 11021 of the light output end 1102 of the optical fiber 110, it is beneficial for the electrons emitted by the electron source 100 to be emitted efficiently along the extending direction of the optical fiber 110. One-dimensional materials have the characteristics of small radius of curvature (nanoscale), can enhance the interaction between light and matter and provide a large field enhancement factor, ensure multi-photon emission, light field emission, etc., and are applied to scenarios requiring high-brightness electron sources.

[0089] The one-dimensional materials can be nanotubes, nanorods or nanowires, nanobelts or coaxial nanocables, etc.

[0090] The nanotubes can be carbon nanotubes, which can be regarded as seamless tubular structures formed by winding single-layer or multi-layer graphite according to certain rules. The nanotubes can also be silicon (Si) nanotubes, selenium (Se) nanotubes, tellurium (Te) nanotubes, bismuth (Bi) nanotubes, boron nitride (BN) nanotubes, boron and nitrogen co-doped carbon nanotubes (BCN nanotubes), tungsten disulfide (WS2) nanotubes, molybdenum disulfide (MoS2) nanotubes, titanium dioxide (TiO2) nanotubes, etc.

[0091] 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.

[0092] There are significant differences between the nanoribbons and the above two nanoscale structures (nanotubes and nanowires). The cross-section of the nanoribbons is different from the nearly circular shape of the nanotubes or nanowires, but presents as a quadrilateral, and the aspect ratio distribution range is generally from several to more than a dozen. The material of the nanoribbons can be oxides, such as tin oxide (SnO) or zinc oxide (ZnO), etc.

[0093] The nanocoaxial cables can be graphite / boron nitride (C / BN) nanocoaxial cables or silicon carbide / sulfur dioxide (CSi / SiO2) nanocoaxial cables, etc.

[0094] The electron excitation layer 121 can also include two-dimensional materials. The electrons in the two-dimensional materials can be transmitted along the two-dimensional plane. Combining with the fact that the electron excitation layer 121 is arranged on the end face 11021 of the light-emitting end 1102 of the optical fiber 110, in this way, it is beneficial for the electrons emitted by the electron source 100 to be emitted efficiently along the extending direction of the optical fiber 110; and compared with setting a thinner 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-current electron sources 100. In addition, the energy levels of the two-dimensional materials are more discrete, and the energy of the electron beam emitted by tunneling is more concentrated and the energy dispersion is smaller.

[0095] The two-dimensional materials have the characteristic of atomic layer thickness. The thickness of the two-dimensional materials can be the thickness of a single atomic layer or the thickness of multiple atomic layers. During the interaction between the laser and the two-dimensional materials, it hardly affects the 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 properties of the emitted electrons and an extremely narrow pulse width.

[0096] The two-dimensional material can be graphene, transition metal sulfide, two-dimensional perovskite, two-dimensional diamond, boron nitride, etc.

[0097] Taking graphene as an example of the selected 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 an atomic thickness of about 0.34 nanometers; the electron excitation layer 121 can also have several or dozens of atomic thicknesses.

[0098] Of course, this application is not limited thereto, and the electron excitation layer 121 also includes two or more of zero-dimensional materials, one-dimensional materials, and two-dimensional materials.

[0099] In this way, when the electron source 100 is used, the laser can be transmitted along the core 111 of the optical fiber 110, so that the laser transmitted in the core 111 can propagate to the end face 11021 of the light output end 1102 and exit, and interact with the electron excitation layer 121, so that the electrons in the electron excitation layer 121 absorb the photons of the laser and undergo an 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 arranges the electron excitation layer 121 on the optical fiber 110 to realize the excitation of electrons, abandoning the complex spatial light coupling structure set due to the introduction of external lasers, and also abandoning the high-magnification microscope set to solve the alignment problem of metal tips, which can reduce the process cost of the electron gun and increase stability.

[0100] 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 relatively low electron emission efficiency. In addition, the conduction band of the metal material is a half-filled band, resulting in a wide energy distribution of the electrons emitted by the excited metal layer), this application uses low-dimensional materials such as zero-dimensional materials, one-dimensional materials, or two-dimensional materials as the material of the electron excitation layer 121. The low-dimensional material has an atomic-level thickness, and the back-incident electrons can be emitted without passing through in-body transmission, with a high electron emission efficiency; moreover, the low-dimensional material has no dangling bonds, is stable in nature and has a high melting point, is not easily damaged, and can be applied to the scenario of high-power excitation, with characteristics such as good stability and high service life; in addition, the low-dimensional material also has a high optical nonlinear effect and a rich electron bandgap, enabling the laser to better interact with the electron excitation layer 121 to generate energy resonance and excite the electrons in the electron excitation layer 121. These electrons are excited and detached into the vacuum, and can form an electron beam, and the electron beam tunneling and emitting from the electron excitation layer 121 has the characteristics of concentrated energy and small energy dispersion.

[0101] In addition, low-dimensional materials can be directly integrated with the optical fiber 110. The optical fiber transmits laser light and serves as a carrier for the low-dimensional materials, capable of providing a stable excitation source with adjustable wavelength, polarization, and optical mode. It can be applied to different application scenarios without the need to provide a complex optical path, and has the characteristics of small size and high integration.

[0102] Since the end face 11021 of the light-emitting end 1102 of the optical fiber 110 is arranged at an angle ɑ with the extending direction of the fiber core 111, in this way, the oblique incidence on the electron excitation layer 121 can be realized, and an optical and electric field perpendicular to the end face 11021 of the light-emitting end 1102 can be achieved. The emission angle of electrons can be changed by changing the angle ɑ, and the emission angle of electrons can also be adjusted by adjusting the polarization state of the laser in the optical fiber 110, which is beneficial to broadening the application range of the electron source 100.

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

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

[0105] It can be understood that the thickness of the electron excitation layer 121 is in the nanometer order 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 emission efficiency and emission power of electrons. Furthermore, an electron beam with ultra-short pulses can be realized by using this electron source 100.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[0121] In some embodiments, the electron source 100 further includes a conductive connection layer 130, and the conductive connection layer 130 is at least disposed on the end face 11021 of the light-emitting end 1102 of the optical fiber 110 and is electrically connected to the electron excitation layer 121.

[0122] 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.

[0123] It should be added that the conductive connection layer 130 is not disposed on the light-emitting path of the laser emitted from the fiber core 111.

[0124] In this way, the electron excitation layer 121 can be electrically connected to the negative electrode of the power supply through the conductive connection layer 130. On the one hand, the power supply can be used to supplement electrons to the electron excitation layer 121, which is beneficial for the electron excitation layer 121 to continuously emit electrons under the excitation of the laser. On the other hand, the direction and convergence of the electrons emitted from the electron excitation layer 121 can be regulated by the voltage applied to the conductive connection layer 130 by the power supply.

[0125] Exemplarily, such as Figure 3As shown, the electron source 100 is applied to the electron gun 10. The electron gun 10 further includes an anode 300 which has a first electron channel 310 for electrons emitted from within the electron excitation layer 121 to pass through. A preset voltage is provided between the anode 300 and the conductive connection layer 130, such that a preset electric field is formed between the anode 300 and the conductive connection layer 130. As a result, the electrons emitted from within the electron excitation layer 121 are emitted towards the first electron channel 310 of the anode 300 under the drive of the preset electric field and pass through the first electron channel 310 and are emitted. Specifically, the electron excitation layer 121 is electrically connected to the negative electrode of the power supply through the conductive connection layer 130, and the anode 300 is electrically connected to the positive electrode of the power supply, so that a preset voltage is provided between the anode 300 and the conductive connection layer 130, and the electron excitation layer 121 and the anode 300 are arranged at intervals along the extending direction of the optical fiber 110. Thus, it is beneficial to form a uniform electric field along the extending direction of the optical fiber 110 by using the anode 300, and it is more beneficial for the electrons to be linearly accelerated along the extending direction of the optical fiber 110 and pass through the first electron channel 310.

[0126] In some embodiments, the electron excitation layer 121 includes a first portion 1211 and a second portion 1212 which are disposed on the end face 11021 of the light-emitting end 1102 and are connected to each other. The first portion 1211 covers the core 111 of the optical fiber 110, and the second portion 1212 is disposed around the first portion 1211 and is electrically connected to the conductive connection layer 130.

[0127] The first portion 1211 may directly cover the core 111 of the optical fiber 110, or the first portion 1211 may indirectly cover the core 111 of the optical fiber 110, and no specific limitation is made here.

[0128] Specifically, the second portion 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 portion 1212 may also be electrically connected to the conductive connection layer 130 through other conductive structures.

[0129] Thus, by using the conductive connection layer 130 to be electrically connected to the second portion 1212 of the electron excitation layer 121, and combining the second portion 1212 being disposed around the first portion 1211, it enables the conductive connection layer 130 to supply electrons to the electron excitation layer 121 while not affecting the interaction between the core 111 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.

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

[0131] In this way, the conductive connection layer 130 can cover the optical fiber 110 more, improving the bonding strength between the conductive connection layer 130 and the optical fiber, and also being beneficial to better using the conductive connection layer 130 to supply electrons to the electron excitation layer 121.

[0132] In some embodiments, the conductive connection layer 130 includes a first metal layer and a second metal layer arranged in a stacked manner, and the adhesion of the first metal layer is greater than that of the second metal layer.

[0133] Exemplarily, the material of the first metal layer is titanium, and the material of the second metal layer is gold.

[0134] In this way, the first metal layer with higher adhesion can make the conductive connection layer 130 better adhere to the optical fiber 110, improving the bonding strength between the conductive connection layer 130 and the optical fiber 110, and also being beneficial to improving the service life of the conductive connection layer 130.

[0135] In some embodiments, please refer to Figure 4 and Figure 5 , the electron emission layer 120 further includes an auxiliary layer 122, and the auxiliary layer 122 is arranged in a stacked manner on one side of the end face 11021 of the electron excitation layer 121 close to the light emitting end 1102, or the auxiliary layer 122 is arranged in a stacked manner on one side of the end face 11021 of the electron excitation layer 121 far from the light emitting end 1102. Figure 4 and Figure 5 gives an example where the auxiliary layer 122 is arranged in a stacked manner on one side of the end face 11021 of the electron excitation layer 121 close to the light emitting end 1102.

[0136] In this application, the auxiliary layer 122 is added. When the electron excitation layer 121 needs 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 arranged on the auxiliary layer 122; or, when the electron excitation layer 121 cannot be directly connected and conducted with the conductive connection layer 130, it is connected to the conductive connection layer 130 through the conductive auxiliary layer 122, and the auxiliary layer 122 is used to achieve electron conduction between the electron excitation layer 121 and the conductive connection layer 130.

[0137] Optionally, the auxiliary layer 122 includes at least one of a conductive support layer and a heat dissipation support layer.

[0138] Optionally, the thickness of the auxiliary layer 122 is 0.1 nm to 100 nm.

[0139] Optionally, the light transmittance of the auxiliary layer 122 is 10% or more, such as 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or 100%.

[0140] Optionally, the auxiliary layer 122 includes a conductive support layer, and the conductive support layer is electrically connected to the conductive connection layer 130.

[0141] In some embodiments, the auxiliary layer 122 includes a conductive support layer, the material of the conductive support layer includes a conductive metal, the laser wavelength in the optical fiber 110 is 200 nm to 10 μm, the pulse power is 1 nW to 1 W, and the repetition frequency is 0 Hz to 10 GHz.

[0142] In this application, the auxiliary layer 122 uses a conductive metal and controls the laser parameters, thereby avoiding the problem of melting caused by laser irradiation of the conductive metal and ensuring that the auxiliary layer has the functions of support and conduction.

[0143] The auxiliary layer 122 may also include a conductive support layer, such as Figure 4 and Figure 5 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.

[0144] The auxiliary layer 122 may be a light-transmitting material; the auxiliary layer 122 may 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 optical fiber 110.

[0145] In this way, both 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 the interaction between the electron excitation layer 121 and the core 111 of the optical fiber 110 will not be affected, which is beneficial to the formation of an electron beam with concentrated energy and small energy dispersion from the electrons tunneling and emitting within the electron excitation layer 121.

[0146] The auxiliary layer 122 may also include a heat dissipation support layer. Exemplarily, the material of the auxiliary layer 122 may be hexagonal boron nitride. Of course, the material of the auxiliary layer 122 may also be 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, so that the electron excitation layer 121 can emit a larger electron beam current.

[0147] Please refer to Figure 6 , according to the second aspect of the present application, a method for preparing an electron source 100 is provided, including the following steps:

[0148] S210. Provide an optical fiber 110. The optical fiber 110 includes a core 111 for transmitting laser light and a cladding layer 112 wrapped around the core 111. The end face 11021 of the light-emitting end 1102 of the optical fiber 110 is arranged at an angle α with the extending direction of the core 111.

[0149] Optionally, an appropriate length of the optical fiber 110 can be intercepted, the end coating layer of the optical fiber 110 can be removed, and one end of the optical fiber 110 can be cut to form the light-emitting end 1102. Specifically, a cutting mechanism can be used to cut one end of the optical fiber 110 to form the light-emitting end 1102. By using the cutting method to form the light-emitting end 1102, the cross section where the end face 11021 of the light-emitting end 1102 is located can be relatively flat, which is beneficial to forming a flat electron excitation layer 121 on the end face 11021 of the light-emitting end 1102.

[0150] S220. Form an electron emission layer 120 on the end face 11021 of the light-emitting end 1102 of the optical fiber 110. The electron emission layer 120 at least includes an electron excitation layer 121. The electron excitation layer 121 covers the core 111 of the optical fiber 110 so that the electron excitation layer 121 is located on the light-emitting path of the laser light emitted from the core 111. The electron excitation layer 121 includes at least one of zero-dimensional materials, one-dimensional materials, and two-dimensional materials.

[0151] The electron excitation layer 121 can be formed by at least one of dry transfer, wet transfer, and direct growth.

[0152] 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 optical fiber 110.

[0153] Taking two-dimensional materials as an example for illustration, the preparation process of forming the electron emission layer 120 by dry transfer is as follows:

[0154] (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 adhesive tape A, and a low-adhesive 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.

[0155] (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 more easily peeled off by heating to peel the tape B from the electron excitation layer 121.

[0156] (3) Transfer the electron excitation layer 121 on the temporary substrate 20 to the end face 11021 of the light output end 1102 of the optical fiber 110.

[0157] Optionally, the electron excitation layer 121 is made of a two-dimensional material, and the material of the temporary substrate 20 can be a polycarbonate propylene ester film.

[0158] 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 etching the substrate to be peeled off with acid or tearing it by hand, and then the electron excitation layer 121 on the temporary substrate 20 is transferred to the end face 11021 of the light output end 1102 of the optical fiber 110. Among them, the substrate to be peeled off can be a metal or other material that can be etched with acid or torn by hand.

[0159] In some other embodiments, the electron excitation layer 121 is prepared by a wet transfer method. 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 output end 1102 of the optical fiber 110 into contact with the zero-dimensional materials, one-dimensional materials or two-dimensional materials on the liquid surface, and drying the zero-dimensional materials, one-dimensional materials and / or two-dimensional materials on the end face 11021 of the light output end 1102 of the optical fiber 110.

[0160] In still some other embodiments, the electron excitation layer 121 is prepared by a direct growth method. The preparation method includes: directly preparing the electron excitation layer 121 on the end face 11021 of the light output end 1102 of the optical fiber 110 by at least one of chemical vapor deposition, physical vapor deposition, molecular beam epitaxy and liquid filling.

[0161] Optionally, before or after forming the electron emission layer 120 on the end face 11021 of the light output end 1102 of the optical fiber 110, the preparation method of the electron source 100 further includes:

[0162] S230. Form a conductive connection layer 130 on the end face 11021 of the light output end 1102 of the optical fiber 110 so that the conductive connection layer 130 overlaps with the electron excitation layer 121.

[0163] 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 by the electron excitation layer 121 under the excitation of laser.

[0164] Optionally, a conductive connection layer 130 is formed on the end face 11021 of the light output end 1102 of the optical fiber 110, so that the conductive connection layer 130 overlaps with the electron excitation layer 121. Specifically, it includes:

[0165] S231. A core protection layer is formed on the end face 11021 of the light output end 1102 of the optical fiber 110, and the core protection layer covers the core 111 of the optical fiber 110.

[0166] It may be that the core protection layer directly covers the core 111 of the optical fiber 110, or it may be that the core protection layer indirectly covers the core 111 of the optical fiber 110, and no specific limitation is made here.

[0167] Optionally, a polymer microsphere solution can be coated on the end face 11021 of the light output end 1102 of the optical fiber 110 to form a core protection layer covering the core 111. Exemplarily, the polymer microsphere solution is a polymethyl methacrylate suspension.

[0168] S232. A conductive material layer covering the core protection layer is formed on the optical fiber 110.

[0169] 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 optical fiber 110.

[0170] 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.

[0171] 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 optical fiber 110 can be soaked in acetone, so that the core protection layer (polymer microspheres) is dissolved, and the part of the conductive material layer provided on the core protection layer (part of the metal coating) flakes off to obtain the conductive connection layer 130.

[0172] It can be understood that the core protection layer can be used to make the orthographic projection of the conductive connection layer 130 on the end face 11021 of the light output end 1102 not coincide with the orthographic projection of the core 111 of the 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 optical fiber 110 can better interact with the electron excitation layer 121 covering the core 111 of the optical fiber 110.

[0173] In some embodiments, please refer to Figure 7 and Figure 8, step S220 of forming the electron emission layer 120 on the end face 11021 of the light-emitting end 1102 of the 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 optical fiber 110 are as follows:

[0174] S221. Oppositely arrange the electron excitation layer 121 and the end face 11021 of the light-emitting end 1102 of the optical fiber 110 in the first direction F1 and parallel to each other.

[0175] Specifically, observe the end face 11021 of the light-emitting end 1102 of the 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 optical fiber 110 in the first direction F1 and parallel to each other, and make the center connection line of the two extend in the first direction F1.

[0176] S222. Drive the optical fiber 110 to move in the first direction F1 to contact the electron excitation layer 121.

[0177] S223. Make the electron excitation layer 121 adhere to the end face 11021 of the light-emitting end 1102 of the optical fiber 110 at a preset temperature.

[0178] 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 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 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 optical fiber 110, and also facilitating the electron excitation layer 121 to completely cover the core 111 of the optical fiber 110, so that the laser transmitted by the core 111 can better interact with the electron excitation layer 121.

[0179] In some specific embodiments, step S220 of forming the electron emission layer 120 on the end face 11021 of the light-emitting end 1102 of the 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 optical fiber 110 are as follows:

[0180] S2201. Attach a ring-shaped 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 ring-shaped heating sheet 40 (the temporary substrate 20 can be fixed to the bottom side of the ring-shaped heating sheet 40 by bonding). And set the electron excitation layer 121 on the temporary substrate 20 downward, and fix the 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 ring-shaped 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 ring-shaped heating sheet 40, the electron excitation layer 121, and the optical fiber 110 are arranged in sequence from top to bottom.

[0181] Optionally, a fixture 50 can be used to fix the optical fiber 110 on the moving platform 60, and set the end face 11021 of the light-emitting end 1102 of the optical fiber 110 upward. The moving platform 60 is used to adjust the position of the 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 optical fiber 110 relative to the horizontal plane to make it horizontal.

[0182] Optionally, the fixture 50 can be a pneumatic gripper or an electric gripper.

[0183] Optionally, the moving platform 60 can be a six-degree-of-freedom platform. The moving platform 60 can also include a linear drive mechanism 61 and a rotary drive mechanism 62 connected to the linear drive mechanism 61. The output end of the rotary drive mechanism 62 is connected to the fixture 50 to drive the fixture 50 and the optical fiber 110 clamped by the fixture 50 to rotate around an axis parallel to the horizontal plane, so that the end face 11021 of the light-emitting end 1102 is horizontal. The linear drive mechanism 61 is used to drive the rotary drive mechanism 62, the fixture 50, and the optical fiber 110 to move along the first direction F1.

[0184] Among them, the linear drive mechanism 61 can be a motor or a cylinder, and the rotary drive mechanism 62 can be a motor or a rotary cylinder.

[0185] S2202. Observe the end face 11021 of the light-emitting end 1102 of the optical fiber 110 and the electron excitation layer 121 under the microscope, and set the electron excitation layer 121 and the end face 11021 of the light-emitting end 1102 of the optical fiber 110 opposite to each other 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.

[0186] 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 help of the microscope.

[0187] 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.

[0188] Optionally, the first preset voltage is 1V - 1.5V, and the preheating temperature is 50 - 60 °C.

[0189] S2204. Drive the 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-emitting end 1102 contact the electron excitation layer 121 to form Newton's rings.

[0190] S2205. At a preset temperature, make the electron excitation layer 121 closely adhere to the end face 11021 of the light-emitting end 1102 of the 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-emitting end 1102.

[0191] Optionally, the second preset voltage is 2.5V - 4V, and the preset temperature is 90 - 100 °C.

[0192] 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.

[0193] Optionally, the third preset voltage is 5.5V - 6V, and the melting temperature is 130 - 150 °C.

[0194] After the electron excitation layer 121 is closely arranged on the end face 11021 of the light-emitting 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 light-emitting end 1102 of the optical fiber 110, which is convenient for removing the remaining temporary substrate 20 on the electron excitation layer 121 subsequently. The part of the temporary substrate 20 not in contact with the annular heating sheet 40 remains on the electron excitation layer 121. The optical fiber 110 can be removed from the fixture 50 and the light-emitting end 1102 of the 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.

[0195] Please refer to Figure 9According to a 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 an electron source 100 according to any one of the above embodiments.

[0196] The electron source 100 is fixed in a housing, and a grid 200 and an anode 300 are sequentially arranged on the electron emission side of the electron source 100 .

[0197] It should be noted that in the present application, the gate 200 is used to limit the shape of the electron beam, and the anode 300 is used to accelerate the electrons. When the electrons are excited and emitted from the electron source 100, they will interact with the electrostatic field established by the gate 200 and the space charge of the electrons themselves, forming an electron beam with a certain shape, passing through the second electron channel 210 of the gate 200 and the first electron channel 310 of the anode 300 to be emitted for use.

[0198] According to a fourth aspect of the present application, an application of the electron source 100 as in the first aspect is provided, and 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.

[0199] The embodiments of the present invention will be described in detail below in conjunction with examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods in the following examples that do not specify specific conditions are preferably referred to the guidance provided in the present invention, and can also be based on the experimental manual or normal conditions in this area, can also be based on the conditions recommended by the manufacturer, or refer to experimental methods known in the art.

[0200] Example 1

[0201] The optical fiber 110 is a single-mode optical fiber. The diameter of the core 111 of the optical fiber 110 is 8.2 μm, the diameter of the optical fiber 110 is 125 μm, and the angle ɑ is selected to be 30 degrees, that is, the bevel angle of the optical fiber 110 forms a 30-degree angle with the axis of the optical fiber 110. The wavelength of the laser transmitted in the optical fiber 110 is 1550 nm. The conductive connection layer 130 includes 4 nm of titanium and 50 nm of gold laminated on the optical fiber 110. Among them, the core 111 at the end face 11021 of the light output end 1102 is exposed (without being covered by the conductive connection layer 130). The electron excitation layer 121 is formed on the end face 11021 of the light output end 1102 by using the above dry transfer method. The electron excitation layer 121 is made of graphene two-dimensional material (the number of layers of the graphene two-dimensional material is 21 layers). The shape of the electron excitation layer 121 is not limited and can be a polygon, a circle, an ellipse, etc. The electron excitation layer 121 is arranged on the end face 11021 of the light output end 1102 of the optical fiber 110 and completely covers the core 111 of the optical fiber 110. Exemplarily, in the radial direction of the optical fiber 110, the size of the electron excitation layer 121 is 30 - 60 μm (much larger than the diameter of the core 111. In this embodiment, in the radial direction of the optical fiber 110, the size of the electron excitation layer 121 is 30 μm).

[0202] Example 2

[0203] The optical fiber 110 is a single-mode optical fiber. The diameter of the core 111 of the optical fiber 110 is 8.2 μm, the diameter of the optical fiber 110 is 125 μm, and the angle ɑ is selected to be 60 degrees, that is, the bevel angle of the optical fiber 110 forms a 60-degree angle with the axis of the optical fiber 110. The wavelength of the laser transmitted in the optical fiber 110 is 1550 nm. The conductive connection layer 130 includes 5 nm of titanium and 60 nm of gold laminated on the optical fiber 110. Among them, the core 111 at the end face 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 film is covered at the position of the core 111, and then the electron excitation layer 121 is formed on the hexagonal boron nitride film by using the above direct dry transfer method. 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). The shape of the electron excitation layer 121 is not limited and can be a polygon, a circle, an ellipse, etc. The electron excitation layer 121 is arranged on the end face 11021 of the light output end 1102 of the optical fiber 110 and completely covers the core 111 of the optical fiber 110. Exemplarily, in the radial direction of the optical fiber 110, the size of the electron excitation layer 121 is 30 - 60 μm (much larger than the diameter of the core 111. In this embodiment, in the radial direction of the optical fiber 110, the size of the electron excitation layer 121 is 50 μm).

[0204] Hexagonal boron nitride is an insulator that does not absorb light and can provide an atomically flat surface, which can improve the flatness of the electron excitation layer 121 and 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.

[0205] Example 3

[0206] Deposit and grow an auxiliary layer 122 with a thickness of 20 nm and a material of gold on the end face 11021 of the light-emitting end 1102 of the optical fiber 110. Then, use CVD to prepare carbon nanotubes on the surface of the auxiliary layer 122, with the axial direction of the carbon nanotubes perpendicular to the surface of the auxiliary layer 122. Then, use CVD to grow multiple quantum dots on the carbon nanotubes to form the electron excitation layer 121. The auxiliary layer 122 is electrically connected to the conductive connection layer 130 to obtain the electron source 100.

[0207] Example 4

[0208] Grow graphene with a thickness of 8 nm on the end face 11021 of the light-emitting end 1102 of the optical fiber 110 having a conductive connection layer 130. Then, use the CVD method to grow carbon nanotubes on the surface of the graphene, with the axial direction of the carbon nanotubes parallel to the plane of the graphene, to obtain the electron excitation layer 121 on the end face 11021 of the light-emitting end 1102 of the optical fiber 110. Among them, the graphene is electrically connected to the conductive connection layer 130 to obtain the electron source 100.

[0209] Comparative Example 1

[0210] Prepare an electron source according to the structure of Example 1, except that the electron excitation layer 121 in Example 1 is replaced with a gold layer with a thickness of 100 nm, and the gold layer is prepared by deposition.

[0211] Comparative Example 2

[0212] Prepare an electron source according to the structure of Comparative Example 1, except that the electron excitation layer 121 in Comparative Example 1 is replaced with a gold layer with a thickness of 8 nm (the same thickness as the graphene).

[0213] As Figure 9 shown, assemble the electron sources prepared by the above examples and comparative examples into an electron gun. The electron gun further includes a housing, a grid 200, and an anode 300. Perform performance tests on the prepared electron gun, and the test results are as follows in the table:

[0214] Table 1

[0215] Number Stability Lifetime Operating vacuum Example 1 1％ 2000 h 10 Pa Example 2 1％ 2500 h 10 Pa Example 3 5％ 500 h <![CDATA[10 -3 Pa]]> Example 4 2％ 1000 h 1 Pa Comparative Example 1 10％ 100 h <![CDATA[10 -5 Pa]]> Comparative Example 2 15％ 50 h <![CDATA[10 -5 Pa]]>

[0216] Among them, stability refers to when the excitation power of the electron source is 50% or more of the damage power and the vacuum degree is 2×10 -5At Pa, the continuous emission current is applied for 1 hour. After removing the defective points, the ratio of the difference between the maximum current and the minimum current to the average current is defined as the stability, which can reflect the working stability of the electron source. The lifetime refers to the continuous emission of current until the current decays to less than 10% of the initial value 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 defined as the lifetime. The working vacuum degree refers to the continuous emission of current when the excitation power of the electron source is 50% or more of the damage power. The vacuum degree gradually increases until a rapid decay of the current occurs (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 this application has good stability, long lifetime, and good working vacuum degree.

[0217] Through testing, it is found 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.

[0218] In short, low-dimensional materials such as zero-dimensional materials, one-dimensional materials, and two-dimensional materials in this application have atomic-level dimensions. The back-incident electrons can be emitted into the vacuum without passing through in-body transmission, which is very suitable for ultrafast electron sources with narrow pulse widths; moreover, low-dimensional materials and different types of optical fibers can be directly integrated, bringing ultra-high stability and 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; low-dimensional materials and tips can be integrated to obtain very sharp optical fiber tips, with large optical field and electric field enhancement factors, providing a large emission beam current; there are many combinations of low-dimensional materials, suitable for optoelectronic sources with various properties. Finally, the optical fiber integrated low-dimensional material electron source and the 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, which can be applied to different application scenarios, and there is no need to provide a complex optical path, with the characteristics of small volume and high integration. When integrated with other devices, stable integration can be achieved without cracking and transforming the vacuum electron device.

[0219] In this application, the oblique cutting of the optical fiber 110 can achieve the oblique incidence of the laser relative to the electron excitation layer 121. By controlling the polarization state of the laser in the optical fiber 110, an optoelectronic field perpendicular to the end face 11021 of the light output end can be achieved to realize optical field emission. The coherence of the electron beam emitted by the electron source 100 is high, and an electron beam with ultrashort pulses can be achieved.

[0220] The electron excitation layer 121 has a nanoscale size, enabling electrons emitted from within the electron excitation layer 121 to be emitted into a vacuum without passing through in-body transmission, which is very suitable for fabricating an ultrafast electron source with a narrow pulse width.

[0221] The direct integration of the electron excitation layer 121 and the optical fiber 110 endows the electron source 100 with ultrahigh stability and integratability, which can broaden the applications of the electron source 100, such as in miniaturized scenarios.

[0222] 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-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features,

[0223] it should be considered as falling within the scope described in this specification.

[0224] The above-described embodiments merely represent several implementation manners of the present application. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all 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, The electron source includes: an optical fiber including a core for transmitting laser light and a cladding layer wrapping the core, wherein an end face of the light-emitting end of the optical fiber is disposed at an angle to the extending direction of the core; and an electron emission layer disposed on the end face of the light-emitting end of the optical fiber, and the electron emission layer at least includes an electron excitation layer covering the core; the laser light emitted from the core can directly irradiate on the electron emission layer, so that the electron excitation layer is excited by the laser light emitted from the core and emits electrons; the electron excitation layer includes at least one of zero-dimensional materials, one-dimensional materials, and two-dimensional materials.

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

3. The electron source according to claim 1, wherein The axial direction of the one-dimensional material in the electron excitation layer forms an angle of 0 to 90° with the emission direction of the emitted laser light.

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

5. The electron source according to claim 1, characterized in that, The materials in the electron excitation layer include one-dimensional materials and zero-dimensional materials disposed at the ends and / or sides of the one-dimensional materials.

6. The electron source according to claim 1, wherein The electron excitation layer includes zero-dimensional materials and two-dimensional materials, and the zero-dimensional materials are disposed on the surface of the two-dimensional materials.

7. The electron source according to claim 1, characterized in that, The electron excitation layer includes one-dimensional materials and two-dimensional materials, and the one-dimensional materials are disposed on the surface of the two-dimensional materials.

8. The electron source according to any one of claims 1-7, characterized in that, The electron source further includes a conductive connection layer, and the conductive connection layer is at least disposed on the end face of the light-emitting end of the optical fiber and is electrically connected to the electron excitation layer.

9. The electron source according to claim 8, characterized in that, The electron excitation layer includes a first part and a second part disposed on the end face of the light-emitting end and connected to each other, the first part covers the core of the optical fiber, the second part is disposed around the first part, and is electrically connected to the conductive connection layer.

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

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

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

13. The electron source according to claim 12, 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 - 100 nm, and the light transmittance is more than 10%.

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

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

16. A method for preparing an electron source, characterized in that, including: An optical fiber is provided; wherein, the optical fiber includes a core for transmitting laser and a cladding layer wrapped around the core, and an end face of the light-emitting end of the optical fiber is arranged at an angle with respect to the extending direction of the core; An electron emission layer is formed on the end face of the light-emitting end of the optical fiber; Wherein, the electron emission layer at least includes an electron excitation layer covering the core, and the laser emitted from the core directly irradiates on the electron emission layer, so that the electron excitation layer is excited by the laser emitted from the core and emits electrons; the electron excitation layer includes at least one of zero-dimensional materials, one-dimensional materials and two-dimensional materials.

17. The method for preparing an electron source according to claim 16, wherein Before or after forming the electron emission layer on the end face of the light-emitting end of the optical fiber, the preparation method of the electron source further includes: Forming a conductive connection layer on the end face of the light-emitting end of the optical fiber, so that the conductive connection layer is overlapped with the electron excitation layer.

18. The method for preparing an electron source according to claim 17, wherein Forming a conductive connection layer on the end face of the light-emitting end of the optical fiber, so that the conductive connection layer is overlapped with the electron excitation layer, specifically including: Forming a core protection layer on the end face of the light-emitting end of the optical fiber, and the core protection layer covers the core of the optical fiber; Forming a conductive material layer covering the core protection layer on the optical fiber; Removing the core protection layer and a part of the conductive material layer disposed on the core protection layer to form the conductive connection layer.

19. The method for preparing an electron source according to claim 16, wherein Forming the electron emission layer on the end face of the light-emitting end of the optical fiber, specifically including: Arranging the electron excitation layer and the end face of the light-emitting end of the optical fiber opposite to each other and parallel to each other in a first direction; Driving the optical fiber to move along the first direction to contact the electron excitation layer; Bonding the electron excitation layer to the end face of the light-emitting end of the optical fiber at a preset temperature.

20. 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 1-15; 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.

21. Use of the electron source according to any one of claims 1-15, characterized in that, The application of the electron source includes at least one of an electron microscope, an electron beam exposure machine, a free electron laser, an electron accelerator, an electron diffraction device, an X-ray tube and a display.

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