Electron source and method of making and using the same

Abstract

The application provides an electron source and a preparation method and application thereof. The electron source comprises an optical fiber, a conductive connecting layer and an electron emission layer. The conductive connecting layer is arranged on the outer surface of the optical fiber. The electron emission layer comprises an electron excitation layer electrically connected with the conductive connecting layer. The electron excitation layer comprises at least one layer of two-dimensional material. The electron excitation layer is arranged on the laser emission path of the optical fiber, and the laser emitted by the optical fiber can directly irradiate on the electron excitation layer, so that the electron excitation layer is excited by the laser and emits electrons. The two-dimensional material as the material of the electron emission layer has the characteristics of good stability and long service life. Moreover, the two-dimensional material can be directly integrated with the optical fiber. The optical fiber can provide a stable excitation source with adjustable wavelength, polarization and optical mode, and can be applied to different application scenarios.

Description

Technical Field

[0001] This invention relates to the field of electronic source technology, and in particular to an electronic source, its preparation method, and its application. Background Technology

[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 their excitation methods. Thermionic electron sources mainly use metallic materials. When heated to several thousand degrees Celsius, electrons are thermally excited and detach from the material surface to form vacuum electrons. Field emission electron sources mainly use metal needle tips. Under the influence of a strong electric field applied externally, a tip discharge effect is generated. Photoemission electron sources use metallic materials as photocathodes and use laser irradiation to excite the photocathode material, thereby generating electrons.

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

[0004] Therefore, it is necessary to provide an electron source with high electron emission efficiency and good stability, as well as its preparation method and application.

[0005] In a first aspect, this application provides an electronic source, which includes an optical fiber, a conductive connection layer and an electron emission layer, wherein the conductive connection layer is disposed on the outer surface of the optical fiber;

[0006] The electron emission layer includes an electron excitation layer electrically connected to the conductive connection layer, and the electron excitation layer includes at least one layer of two-dimensional material;

[0007] The electron excitation layer is disposed on the laser emission path of the optical fiber, and the laser emitted from the optical fiber can directly irradiate the electron excitation layer, so that the electron excitation layer is excited by the laser and emits electrons.

[0008] In some embodiments, the thickness of the electron excitation layer is 0.1 nm to 100 nm.

[0009] In some embodiments, the thickness of the two-dimensional material is 0.1 nm to 50 nm.

[0010] In some embodiments, the two-dimensional material includes at least one selected from graphene, transition metal chalcogenides, two-dimensional perovskites, two-dimensional diamond, and boron nitride.

[0011] In some embodiments, the electron excitation layer comprises at least two layers of two-dimensional material stacked sequentially along the laser emission direction of the optical fiber, wherein the two-dimensional material is a conductive two-dimensional material.

[0012] In some implementations, the two-dimensional materials in adjacent layers may be the same or different.

[0013] In some embodiments, the crystal axis angle between two adjacent layers of the two-dimensional material is 0° to 360°.

[0014] In some embodiments, the electron excitation layer is formed by splicing together at least two two-dimensional materials of different materials, and the laser of the optical fiber irradiates the splice of adjacent two-dimensional materials.

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

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

[0017] In some embodiments, the auxiliary layer includes a transparent support layer, the material of which includes at least one selected from boron nitride, mica, and diamond.

[0018] In some embodiments, the thickness of the transparent support layer is 0.1 nm to 1000 nm, and the light transmittance is ≥10%.

[0019] In some embodiments, the auxiliary layer includes a conductive support layer, and the electron excitation layer is electrically connected to the conductive connection layer through the conductive support layer.

[0020] In some embodiments, the material of the conductive support layer includes at least one of a conductive metal and graphene.

[0021] In some embodiments, the thickness of the conductive support layer is 0.1 nm to 100 nm.

[0022] In some embodiments, the optical fiber is a solid fiber, a needle-tip fiber, a side-cut fiber, or a perforated fiber.

[0023] Secondly, this application provides a method for preparing an electron source as described in the first aspect, the method comprising:

[0024] An electron source is prepared by forming an electron excitation layer composed of at least one two-dimensional material along the laser emission path of the optical fiber, and forming a conductive connection layer electrically connected to the electron excitation layer on the outer surface of the optical fiber.

[0025] Thirdly, this application provides an electron gun, the electron gun including a housing, a gate, an anode and an electron source as described in the first aspect;

[0026] The electron source is fixed inside the housing, and the gate and the anode are sequentially arranged on the electron emission side of the electron source.

[0027] Fourthly, this application provides an application of the electronic source as described in the first aspect, the application of which includes at least one of an electron microscope, an electron beam irradiator, an X-ray tube, a free-electron laser, and a display.

[0028] Compared with traditional technologies, this application has at least the following beneficial effects:

[0029] This application employs at least one layer of two-dimensional material as the electron emission layer. The two-dimensional material has atomic-level thickness, allowing electrons excited by laser irradiation to be emitted into the vacuum without intralayer propagation, making it ideal for ultrafast electron sources with low energy dissipation, high brightness, and narrow pulse width. The two-dimensional material has no dangling bonds and possesses good stability and a high melting point, making it less prone to damage to high-power, high-current electron sources. Furthermore, the rich variety of two-dimensional materials and their homogeneous and heterogeneous structures provide extremely high degrees of freedom in electron emission properties, enabling pulsed electron sources and one-dimensional electron source emission. In addition, this application directly integrates the two-dimensional material with optical fiber. The optical fiber transmits the laser and serves as a low-dimensional material carrier, providing a stable excitation source with tunable wavelength, polarization, and optical mode, suitable for various application scenarios. It eliminates the need for complex optical paths and features small size and high integration. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of the electronic source provided in Embodiment 1 of this application, wherein 110a - solid optical fiber; 120a - electronic excitation layer; 130a - conductive connection layer.

[0031] Figure 2 This is a schematic diagram of the structure of the electronic source provided in Embodiment 2 of this application, wherein 110b - solid optical fiber; 120b - electronic excitation layer; 121b - first material layer; 122b - second material layer; 130b - conductive connection layer.

[0032] Figure 3 This is a schematic diagram of the structure of the electron source provided in Embodiment 3 of this application, wherein 110c-solid optical fiber; 120c-electron excitation layer; 130c-conductive connection layer; 140c-transparent support layer.

[0033] Figure 4 This is a schematic diagram of the structure of the electron source provided in Embodiment 4 of this application, wherein 110d is a solid optical fiber; 120d is an electron excitation layer; 130d is a conductive connection layer; and 150d is a conductive support layer.

[0034] Figure 5This is a schematic diagram of the structure of the electronic source provided in Embodiment 5 of this application, wherein 110e-solid optical fiber; 120e-electron excitation layer; 130e-conductive connection layer.

[0035] Figure 6 This is a schematic diagram of the laser emission end face structure of the electron source provided in Embodiment 5 of this application, wherein 120e-electron excitation layer; 121e-first material layer; 122e-second material layer; 130e-conductive connection layer.

[0036] Figure 7 This is a schematic diagram of the structure of the electronic source provided in Embodiment 6 of this application, wherein 110f - solid optical fiber; 120f - electronic excitation layer; 121f - first material layer; 122f - second material layer; 130f - conductive connection layer; 150f - conductive support layer.

[0037] Figure 8 This is a schematic diagram of the end face structure of the electron source provided in Embodiment 6 of this application, wherein 120f is an electron excitation layer; 121f is a first material layer; 122f is a second material layer; and 130f is a conductive connection layer.

[0038] Figure 9 This is a schematic diagram of the structure of the electronic source provided in Embodiment 7 of this application, wherein 110g - perforated optical fiber; 120g - electronic excitation layer; 121g - first material layer; 122g - second material layer; 130g - conductive connection layer.

[0039] Figure 10 This is a schematic diagram of the internal structure of an electron gun provided in one embodiment of this application, wherein 100-electron source; 200-gate; 300-anode. Detailed Implementation

[0040] The present invention will be further described in detail below with reference to embodiments and examples. These embodiments and examples are for illustrative purposes only and are not intended to limit the scope of the invention. The purpose of providing these embodiments and examples is to enable a more thorough and comprehensive understanding of the disclosure of the present invention. It should also be understood that the present invention can be implemented in many different forms and is not limited to the embodiments and examples described herein. Those skilled in the art can make various modifications or alterations without departing from the spirit of the present invention, and the equivalent forms obtained also fall within the protection scope of the present invention. Furthermore, numerous specific details are set forth in the following description to provide a fuller understanding of the present invention. It should be understood that the present invention can be implemented without one or more of these details.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0042] In this invention, "optionally," "optionally," and "optional" mean that they are optional, that is, they are selected from either "with" or "without." If multiple "options" appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "option" is independent.

[0043] In this invention, the terms "first aspect," "second aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0044] In this invention, the technical features described in an open-ended manner include both closed-ended technical solutions composed of the listed features and open-ended technical solutions that include the listed features.

[0045] In this invention, numerical intervals (i.e., numerical ranges) are involved. Unless otherwise specified, the distribution of selectable values ​​within the numerical interval is considered continuous, and includes the two endpoints of the numerical interval (i.e., the minimum and maximum values), as well as every value between these two endpoints. Unless otherwise specified, when the numerical interval refers only to the integers within the numerical interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints, which is equivalent to directly listing every integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical ranges disclosed in this application should be understood to include any and all subranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, percentage, ratio, etc. The term "numerical interval" can be broadly included to include percentage intervals, ratio intervals, proportion intervals, etc.

[0046] All references to documents mentioned in this application are incorporated herein by reference as if each document were individually incorporated by reference. Unless they conflict with the inventive purpose and / or technical solution of this application, the referenced documents involved in this invention are incorporated herein by reference in their entirety and for all purposes. When references are made in this application, the definitions of relevant technical features, terms, nouns, phrases, etc., in the referenced documents are also incorporated herein by reference. When references are made in this application, examples and preferred embodiments of the relevant technical features cited may also be incorporated herein by reference, but only to the extent that they enable the implementation of this invention. It should be understood that when the cited content conflicts with the description in this application, this application shall prevail or modifications shall be made adaptively based on the description in this application.

[0047] In traditional technologies, thermionic electron sources primarily utilize metallic materials such as tungsten filaments and lanthanum hexaboride. When heated to thousands of degrees Celsius, electrons are thermally excited and detach from the material surface, forming vacuum electrons. Field emission electron sources mainly employ metal tips such as tungsten, generating a tip discharge effect under the influence of a strong external electric field. Thermionic electron sources can operate in relatively poor vacuum environments, exhibiting good environmental adaptability and stability, but suffer from lower brightness and poor coherence. Field emission electron sources produce electron beams with high brightness and good coherence, but require high vacuum levels and are highly sensitive to vibrations. Both thermionic and field emission electron sources offer limited control over electron emission properties, making it impossible to simultaneously achieve both high emission efficiency and stability.

[0048] Optical electron emission sources typically use metallic materials such as Au as the electron emission layer, with thicknesses exceeding 50 nm, sometimes reaching hundreds of nanometers. However, the inventors of this application have discovered that the large thickness of the metallic electron emission layer results in a significant distance (50 nm to hundreds of nanometers) between the surface directly affected by the laser (the bottom layer) and the surface emitting electrons (the top layer). Electrons excited from the bottom layer are easily affected by scattering from the metal lattice as they pass through the electron emission layer, thus impacting emission efficiency. Furthermore, metallic materials are prone to damage under high-power laser irradiation, affecting the lifespan of the electron emission layer and consequently the emission efficiency and stability. While some methods employ side-incidence laser excitation, compared to back-incidence, side-incidence requires modification of the vacuum cavity and suffers from unstable excitation conditions.

[0049] Furthermore, traditional technologies utilize graphene as a saturable absorber. Graphene possesses broadband saturable absorption characteristics and a fast recovery time, making it suitable for Q-switching and mode-locking in lasers, or for sensing and detection by modulating the laser spectrum. However, graphene laser modulation differs from graphene electron emission. Graphene photoexcitation electron sources are based on the photoelectric effect, exciting and emitting electrons, while graphene laser modulation operates on the principle of light absorption, thereby controlling the laser's output parameters. Specifically, graphene laser modulation and graphene electron emission are significantly different; graphene electron emission is based on the photoelectric effect, while graphene laser modulation operates on the principle of light absorption. In laser modulation, the graphene saturable absorber primarily utilizes the fact that graphene's absorbance (or transmittance) increases (or decreases) with increasing incident light power, eventually reaching a saturation threshold. Its main application is in lasers for generating laser pulses. For example, in the ring fiber resonator of a fiber laser, when light circulates in the resonator, if the light power passing through the graphene saturable absorber exceeds its saturable absorption threshold, the light intensity in the cavity will instantly drop below the saturable absorption threshold due to the saturable absorption effect. This dropped light energy is output from the beam splitter of the cavity in the form of pulses.

[0050] Therefore, it is necessary to provide an electron source that can balance electron emission efficiency and stability.

[0051] This application uses a two-dimensional material as the electron emission layer. Under laser irradiation, the two-dimensional material undergoes a photoelectric effect, emitting electrons. Furthermore, the two-dimensional material has atomic-level thickness, is free of dangling bonds, and exhibits stable properties, resulting in high stability and long service life. Moreover, the two-dimensional material can be stacked or spliced ​​to form heterojunctions or homojunctions, thereby realizing electron sources with different modes. In addition, in this application, the two-dimensional material is directly integrated with optical fibers. Optical fibers can provide a stable excitation source with tunable wavelength, polarization, and optical mode, making it suitable for various application scenarios.

[0052] The first aspect of this application provides an electronic source, which includes an optical fiber, a conductive connection layer and an electron emission layer, wherein the conductive connection layer is disposed on the outer surface of the optical fiber;

[0053] The electron emission layer includes an electron excitation layer electrically connected to the conductive connection layer, and the electron excitation layer includes at least one layer of two-dimensional material;

[0054] The electron excitation layer is disposed on the laser emission path of the optical fiber, and the laser emitted from the optical fiber can directly irradiate the electron excitation layer, so that the electron excitation layer is excited by the laser and emits electrons.

[0055] This application employs at least one layer of two-dimensional material as the electronic excitation layer. The two-dimensional material has atomic-level thickness, allowing electrons generated by laser excitation to be emitted into the vacuum without intralayer propagation, making it ideal for ultrafast electron sources with narrow pulse widths. The two-dimensional material lacks dangling bonds and possesses high stability and a high melting point, making it less prone to damage and suitable for high-power, high-current electron sources. Furthermore, the rich variety of two-dimensional materials and their homogeneous and heterogeneous structures provide extremely high degrees of freedom in electron emission properties, enabling pulsed electron sources and one-dimensional electron source emission. In addition, this application directly integrates the two-dimensional material with optical fiber. The optical fiber transmits the laser and serves as a low-dimensional material carrier, providing a stable excitation source with tunable wavelength, polarization, and optical mode, applicable to various application scenarios. It eliminates the need for complex optical paths and features small size and high integration.

[0056] It should be noted that, in this application, two-dimensional materials refer to materials in which electrons can move freely in only two dimensions at a non-nanoscale scale (i.e., planar motion). The nanoscale refers to 1 nm to 100 nm. Two-dimensional materials can be excited and emit electrons under laser excitation.

[0057] It should be noted that the light emission path of the optical fiber in this application refers to the path of laser irradiation within the optical fiber. Taking a solid-core optical fiber as an example, the laser emission position of the solid-core optical fiber is located at the fiber core end face, meaning the electron emission layer can be located at the fiber core. Taking a side-sectioned optical fiber as another example, the laser emission position of the side-sectioned optical fiber is located on one side of the side section, meaning the electron emission layer can be located at the side section. It is understood that in this application, the electron emission layer can be in direct contact with the laser emission surface of the optical fiber, or it can be supported by other structural layers; that is, the goal is simply to ensure that the laser emitted from the optical fiber can irradiate the electron emission layer.

[0058] It should also be noted that the purpose of electrically connecting the conductive connection layer and the electron excitation layer in this application is to connect the low-dimensional material with the external circuit to form a complete loop, thereby achieving charge replenishment and electric field control. The direction and convergence of electron emission can be adjusted by voltage regulation. As one implementation, the conductive connection layer in this application can be directly connected to the electron excitation layer. In other implementations, the conductive connection layer and the electron excitation layer can also be electrically connected through other conductive structures. For example, taking a solid-core optical fiber, the conductive connection layer is disposed on the side of the solid-core optical fiber, and the electron excitation layer is disposed at the core of the solid-core optical fiber. The conductive connection layer and the electron excitation layer are electrically connected, and there is no conductive connection layer at the core.

[0059] In some embodiments, the two-dimensional material includes a dopant element. Optionally, the dopant element includes at least one selected from alkali metals, alkaline earth metals, transition metals, rare earth elements, halogen elements, and light elements, wherein the light element includes at least one selected from B, C, N, and O.

[0060] This application improves the conductivity and electron emission performance of two-dimensional materials by doping them with elements. For example, alkali metals and alkaline earth metals can improve the conductivity of low-dimensional materials and reduce their work function to increase the emission beam current; elements such as B, C, N, O, F, and rare earth elements can create discrete energy levels to obtain narrow-energy electron beams.

[0061] In some embodiments, the conductive connection layer is provided with electrodes for connection to an external circuit. Optionally, the conductive connection layer may fully cover or partially cover the outer surface of the optical fiber, and the laser emission path does not have a conductive connection layer. Further optionally, the thickness of the conductive connection layer is 10 nm to 1 μm, for example, it may be 10 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm or 1 μm.

[0062] In some embodiments, the thickness of the electron excitation layer is 0.1 nm to 100 nm, for example, it can be 0.1 nm, 0.5 nm, 1 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm or 100 nm.

[0063] In some embodiments, the thickness of the two-dimensional material is 0.1 nm to 50 nm, for example, it can be 0.1 nm, 0.5 nm, 1 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm or 50 nm.

[0064] In some embodiments, the two-dimensional material includes at least one selected from graphene, transition metal chalcogenides, two-dimensional perovskites, two-dimensional diamond, and boron nitride. Optionally, the transition metal chalcogenides include at least one selected from WS2, WSe2, and NbSe2.

[0065] In some embodiments, the electron excitation layer comprises at least two layers of two-dimensional material stacked sequentially along the laser emission direction of the optical fiber.

[0066] Optionally, all of the two-dimensional materials are conductive two-dimensional materials.

[0067] In this application, two-dimensional materials with conductivity are stacked, and the charge transfer between the two-dimensional materials is fast and the stability is high. If there is an insulating material in the stacked two-dimensional materials, the insulating material will block the electron transport. Not only is it necessary to add an additional control electrode, but there is also an additional scattering problem during the electron transfer process, resulting in low emission efficiency and high energy dissipation.

[0068] In some embodiments, the two-dimensional materials of adjacent layers may be the same or different.

[0069] In some embodiments, the electron excitation layer comprises at least two layers of two-dimensional material sequentially stacked along the laser emission direction of the optical fiber, the two-dimensional materials having the same or different thicknesses. Preferably, the thickness of the two-dimensional materials decreases sequentially along the direction away from the optical fiber.

[0070] In some embodiments, the crystal axis angle between two adjacent layers of the two-dimensional material is 0° to 360°, for example, it can be 0°, 30°, 60°, 90°, 120°, 150°, 180°, 210°, 240°, 270°, 300°, 330° or 360°.

[0071] This application uses a multilayer stack of two-dimensional materials to form a vertical heterojunction or a vertical homojunction between adjacent two layers of two-dimensional materials. The heterojunction structure can enhance the interaction between light and two-dimensional materials, achieving high-efficiency electron emission under low laser power. Moreover, the heterojunction structure has the function of interface bandgap modulation. Through material design and rotation angle modulation, special interface states can be obtained to achieve high brightness and low energy dissipation electron emission.

[0072] In some embodiments, the electron-emitting layer is formed by splicing together at least two two-dimensional materials of different materials, and the laser light from the optical fiber irradiates the splice between adjacent two-dimensional materials. Optionally, the electron-emitting layer includes a two-dimensional material layer formed by splicing together graphene and molybdenum disulfide. The splice between graphene and molybdenum disulfide forms a one-dimensional interface, and the response of this one-dimensional interface to light is different from that of both graphene and molybdenum disulfide, thereby achieving one-dimensional emission from the interface state.

[0073] In some embodiments, the electron emission layer is formed by splicing together at least two two-dimensional materials of different materials, with adjacent two-dimensional materials having the same or different thicknesses. This application sets different thicknesses for the spliced ​​two-dimensional materials to achieve different forms of electron excitation.

[0074] In some embodiments, the electron emission layer further includes an auxiliary layer, which is stacked on the side of the electron excitation layer closest to the optical fiber; or,

[0075] The auxiliary layer is stacked on the side of the electron excitation layer away from the optical fiber.

[0076] In this application, an auxiliary layer is added. When the electron excitation layer requires structural support, the auxiliary layer is used to provide structural support for the electron excitation layer, so as to achieve the flat laying of the two-dimensional material. In addition, the auxiliary layer can also serve as a heat dissipation structure to improve the heat dissipation effect of the electron source. Alternatively, when the electron emission layer cannot be directly electrically connected to the conductive connection layer, it is connected to the conductive connection layer through a conductive auxiliary layer, so as to achieve electron conduction between the electron emission layer and the conductive connection layer.

[0077] In some embodiments, the auxiliary layer includes a transparent support layer.

[0078] Optionally, the transparent support layer may be made of at least one of boron nitride, mica, and diamond.

[0079] This application uses a transparent material as a transparent support layer, which does not affect the interaction between the laser and the two-dimensional material.

[0080] In some embodiments, the thickness of the transparent support layer is 0.1nm to 1000nm, for example, it can be 0.1nm, 0.5nm, 1nm, 5nm, 10nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm or 1000nm.

[0081] In some embodiments, the light transmittance of the transparent support layer is ≥10%, for example, it can be 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100%.

[0082] In some embodiments, the auxiliary layer includes a conductive support layer, and the electron emission layer is electrically connected to the conductive connection layer through the conductive support layer.

[0083] In some embodiments, the material of the conductive support layer includes at least one of a conductive metal and graphene. Optionally, the conductive metal includes at least one of gold, silver, and copper.

[0084] In some embodiments, the thickness of the conductive support layer is 0.1 nm to 100 nm, for example, it can be 0.1 nm, 0.5 nm, 1 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm or 100 nm. Preferably, it is 1 nm to 50 nm.

[0085] In some embodiments, the conductive support layer is provided on the laser emission path of the optical fiber, and the wavelength of the laser is 200nm~2000nm, and the pulse power is 1nW~1W.

[0086] In this application, the auxiliary layer is made of conductive metal, and the laser parameters are controlled to avoid the problem of melting caused by laser irradiation of conductive metal, thus ensuring that the auxiliary layer has the functions of support and conductivity.

[0087] In some embodiments, the auxiliary layer is graphene. This application uses graphene as the auxiliary layer because graphene not only has electrical conductivity but also excellent heat dissipation capabilities.

[0088] In some embodiments, the optical fiber is a solid optical fiber, a needle-tip optical fiber, a side-sectioned optical fiber, or a perforated optical fiber.

[0089] In some embodiments, the optical fiber is a tip-shaped optical fiber. This application places a two-dimensional material on the tip-shaped optical fiber. Due to the tip geometry of the optical fiber, the field emission enhancement factor is improved, resulting in a higher brightness electron source. Furthermore, at least one of a zero-dimensional material and a one-dimensional material is placed on the two-dimensional material to achieve functions such as high brightness, low energy dissipation, and narrow pulse width.

[0090] In some embodiments, the optical fiber is a side-sectioned optical fiber. This application places a two-dimensional material on the side section of the side-sectioned optical fiber, and evanescent waves leaking from the fiber core interact with the two-dimensional material in the horizontal direction. Edge states similar to those of a one-dimensional material are obtained at the side section, forming a novel electron emission structure that achieves high brightness, low energy dissipation, and narrow pulse width.

[0091] In some embodiments, the optical fiber is a perforated optical fiber. In this application, a perforated optical fiber is a type of optical fiber with a microstructure or that is completely hollow, including photonic crystal fibers, antiresonant fibers, or capillary fibers. Two-dimensional materials can be disposed within the pores or walls of the perforated optical fiber, allowing for a longer interaction distance between the laser and the low-dimensional material, thereby achieving high-brightness electron emission. Because perforated optical fibers possess a unique optical transmission mode, and because different types or dimensions of materials can be further grown or transferred within the pores or walls already filled with two-dimensional materials to form heterojunctions, multifunctional electron emission can be achieved.

[0092] In some embodiments, the optical fiber is a solid-core optical fiber. The two-dimensional material of this application is disposed at the core of the solid-core optical fiber, and evanescent waves leaking from the core can interact with the two-dimensional material surrounding the optical fiber. This system allows for a longer light-material interaction distance, enabling high-brightness electron emission. Furthermore, different diameters of micro / nano fibers can be drawn, allowing for the interaction of light of different modes and intensities with low-dimensional materials, thus achieving precisely controlled electron emission parameters. Additionally, different types or dimensions of materials can be further grown or transferred on the grown or transferred low-dimensional material to form heterojunctions, achieving multifunctional electron emission.

[0093] It should be noted that this application does not impose specific requirements or special limitations on the size of the optical fiber, and those skilled in the art can reasonably select the size of the optical fiber according to the actual usage requirements.

[0094] In some embodiments, the surface of the two-dimensional material is provided with at least one of a zero-dimensional material and a one-dimensional material.

[0095] This application modifies the surface of a two-dimensional material by setting zero-dimensional or one-dimensional materials on the surface of the material, thereby enabling electron source emission in different modes.

[0096] Optionally, the surface of the two-dimensional material is dispersed with zero-dimensional material.

[0097] Optionally, a one-dimensional material is disposed on the surface of the two-dimensional material, and the angle between the axial direction of the one-dimensional material and the plane of the two-dimensional material is 0~90°.

[0098] A second aspect of this application provides a method for preparing an electron source as described in the first aspect, the method comprising:

[0099] An electron source is prepared by forming an electron excitation layer composed of at least one two-dimensional material along the laser emission path of the optical fiber, and forming a conductive connection layer electrically connected to the electron excitation layer on the outer surface of the optical fiber.

[0100] It should be noted that this application does not impose specific requirements or limitations on the formation method of two-dimensional materials, and those skilled in the art can make reasonable choices based on the actual materials. For example, two-dimensional materials can be formed by at least one of dry transfer, wet transfer, and direct growth.

[0101] In some embodiments, the electron emission layer is prepared by a two-dimensional material dry transfer method, the preparation method including: transferring the two-dimensional material onto an adhesive tape by mechanical peeling, and transferring the two-dimensional material onto the laser emission side of the optical fiber through the adhesive tape.

[0102] In some embodiments, the electron emission layer is prepared by a two-dimensional material wet transfer method, the preparation method including: preparing the two-dimensional material directly in a solution and floating it on the liquid surface, contacting the material on the liquid surface with an optical fiber and drying it.

[0103] In some embodiments, the electron emission layer is prepared by directly growing a two-dimensional material. The preparation method includes forming a two-dimensional material directly on the laser emission side of an optical fiber using at least one of chemical vapor deposition, physical vapor deposition, molecular beam epitaxy, and liquid filling to prepare the electron emission layer.

[0104] A third aspect of this application provides an electron gun, the electron gun comprising a housing, a gate, an anode, and an electron source as described in the first aspect;

[0105] The electron source is fixed inside the housing, and the gate and the anode are sequentially arranged on the electron emission side of the electron source.

[0106] It should be noted that in this application, the anode is used to restrict the shape of the electron beam, and the grid is used to accelerate the electrons. When electrons are excited and emitted from the electron source, they will interact with the electrostatic field established by the space charge of the anode and the electrons themselves, forming an electron beam with a certain shape, which is then emitted from the grid for use.

[0107] The fourth aspect of this application provides an application of an electronic source as described in the first aspect, the application of which includes at least one of an electron microscope, an electron beam irradiator, an X-ray tube, a free-electron laser, and a display.

[0108] The embodiments of the present invention will be described in detail below with reference to examples. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. For experimental methods in the following embodiments where specific conditions are not specified, please refer to the guidelines given in this invention, or follow experimental manuals or conventional conditions in the art, or follow the conditions recommended by the manufacturer, or refer to experimental methods known in the art.

[0109] In the following embodiments, the conductive interconnect layer includes a Ti layer with a thickness of 5 nm and an Au layer with a thickness of 60 nm.

[0110] Example 1

[0111] This embodiment provides an electronic source, such as... Figure 1 As shown, it includes a solid optical fiber 110a, an electronic excitation layer 120a, and a conductive connection layer 130a. The conductive connection layer 130a covers the sidewall of the solid optical fiber 110a and forms an annular layer on one side of the laser emission end face of the solid optical fiber 110a. The annular layer does not cover the core of the solid optical fiber 110a. An electronic excitation layer 120a with a thickness of 1nm and made of graphene is disposed on one side of the laser emission end face of the solid optical fiber 110a. The electronic excitation layer 120a covers the core of the solid optical fiber 110a and is erected on the annular layer and electrically connected to the conductive connection layer 130a.

[0112] This embodiment also provides a method for preparing the above-mentioned electron source, including:

[0113] The graphene was adhered and peeled off using a first adhesive tape, then the graphene material on the first tape was dissociated a second time using a second adhesive tape, and then the dissociation was repeated using a third adhesive tape until the thickness of the graphene was 1 nm.

[0114] Then, the graphene-containing tape was transferred onto a polypropylene carbonate film, baked at 50°C for 2 minutes, and the tape was peeled off to obtain a polypropylene carbonate film containing graphene.

[0115] A conductive connection layer 130a is deposited on a solid optical fiber 110a, forming an annular layer on the laser emission side of the solid optical fiber 110a. Then, a polypropylene carbonate film containing graphene is transferred to the laser emission side of the solid optical fiber 110a, so that the polypropylene carbonate film containing graphene is bonded to the annular layer and covers the core of the solid optical fiber 110a. After the polypropylene carbonate is heated and melted, the residual polypropylene carbonate film is removed by immersion in acetone to form an electron excitation layer 120a, thus preparing the electron source.

[0116] Example 2

[0117] The electron source was prepared according to the method in Example 1, with the only difference being that... Figure 2 As shown, the electron source includes a solid optical fiber 110b, an electron excitation layer 120b, and a conductive connection layer 130b. The electron excitation layer 120b includes a first material layer 121b and a second material layer 122b arranged sequentially along the laser emission direction. The first material layer 121b is a graphene layer with a thickness of 5nm, and the second material layer 122b is a molybdenum disulfide layer with a thickness of 2nm.

[0118] Example 3

[0119] The electron source was prepared according to the method in Example 1, with the only difference being that... Figure 3 As shown, the electron source includes a solid optical fiber 110c, an electron excitation layer 120c, a conductive connection layer 130c, and a transparent support layer 140c. The transparent support layer 140c is disposed on the side of the electron excitation layer 120c close to the solid optical fiber 110c, and the transparent support layer 140c is boron nitride with a thickness of 100nm.

[0120] Example 4

[0121] The electron source was prepared according to the method in Example 1, with the only difference being that... Figure 4 As shown, the electron source includes a solid optical fiber 110d, an electron excitation layer 120d, a conductive connection layer 130d, and a conductive support layer 150d. The electron excitation layer 120d is made of a 2nm thick molybdenum disulfide layer. The conductive support layer 150d is disposed on the side of the electron excitation layer 120d close to the solid optical fiber 110d. The conductive support layer 150d is a 5nm thick gold layer. The conductive support layer 120d is in contact with and electrically connected to the conductive connection layer 130d.

[0122] Example 5

[0123] The electron source was prepared according to the method in Example 1, with the only difference being that... Figure 5 and Figure 6As shown, the electron source includes a solid optical fiber 110e, an electron excitation layer 120e, and a conductive connection layer 130e. The electron excitation layer 120e is formed by splicing a first material layer 121e and a second material layer 122e. The first material layer 121e is graphene with a thickness of 1 nm, and the second material layer 122e is molybdenum disulfide with a thickness of 3 nm. The shape of the splice is a straight line.

[0124] Example 6

[0125] The electron source was prepared according to the method in Example 1, with the only difference being that... Figure 7 and Figure 8 As shown, the electron source includes a solid optical fiber 110f, an electron excitation layer 120f, a conductive connection layer 130f, and a conductive support layer 150f. The conductive support layer 150f is disposed on one side of the electron excitation layer 120f located on the solid optical fiber 110f. The conductive support layer 150f is electrically connected to the conductive connection layer 130f. The electron excitation layer 120f consists of a first material layer 121f and a second material layer 122f stacked along the laser emission direction. Both the first material layer 121f and the second material layer 122f are perovskite layers with a thickness of 2nm, and the crystal axis angle between the two perovskite layers is 90°.

[0126] Example 7

[0127] The electron source was prepared according to the method in Example 1, with the only difference being that... Figure 9 As shown, the electron source includes a perforated optical fiber 110g, an electron excitation layer 120g, and a conductive connection layer 130g. The electron excitation layer 120g is disposed on a first material layer 121g and a second material layer 122g on the inner wall of the perforated optical fiber 110g. The first material layer 121g and the second material layer 122g are stacked sequentially in a direction away from the inner wall of the perforated optical fiber 110g. The first material layer 121g is graphene with a thickness of 5nm, and the second material layer 122g is a molybdenum disulfide layer with a thickness of 3nm. The conductive connection layer 130g is conductively connected to the first material layer 121g.

[0128] Comparative Example 1

[0129] An electron source was prepared according to the structure of Example 1, except that the electron excitation layer in Example 1 was replaced with a gold layer with a thickness of 60 nm, and the gold layer was prepared by deposition.

[0130] Comparative Example 2

[0131] An electron source was prepared according to the structure of Comparative Example 1, except that the electron excitation layer in Comparative Example 1 was replaced with a gold layer with a thickness of 1 nm.

[0132] like Figure 10As shown, the electron source 100 prepared using the above embodiments and comparative examples is assembled into an electron gun. The electron gun also includes a housing, a gate 200, and an anode 300. The performance of the prepared electron gun is tested, and the test methods include:

[0133] Stability test: At an excitation power of 50% of the damage power, the vacuum level is 2×10⁻⁶. -5 Pa, continuous emission current for 1 hour, after removing bad points, calculate the difference between the maximum current and the minimum current and the average current, that is, stability parameter = (maximum current - minimum current) / average current.

[0134] Lifetime test: At an excitation power of 50% of the damage power, the vacuum level is 2×10⁻⁶. -5 Pa is the time it takes for the continuously emitted current to decay to less than 10% of its initial value, which is defined as the lifetime.

[0135] Working vacuum test: When the excitation power is 50% of the damage power, the electron gun continuously emits current and gradually increases the working vacuum level until the current decays rapidly (rapid decay is defined as the current decaying by more than 50% within 1 minute). The vacuum level at this point is defined as the working vacuum level.

[0136] Damage power refers to the laser power at which damage occurs when a material is damaged under 100 fs pulsed laser irradiation. For example, the damage power of graphene is 0.25 J / cm. 2 The damage threshold for gold is 0.1 J / cm. 2 .

[0137] The test results are shown in Table 1.

[0138] Table 1

[0139]

[0140] As can be seen from the table above:

[0141] This application employs at least one layer of two-dimensional material as the electron emission layer. The two-dimensional material has atomic-level thickness, allowing electrons excited by laser irradiation to be emitted into the vacuum without intralayer propagation, making it ideal for ultrafast electron sources with narrow pulse widths. The two-dimensional material has no dangling bonds and possesses good stability and a high melting point, making it less prone to damage to high-power, high-current electron sources. Furthermore, the rich variety of two-dimensional materials and their homogeneous and heterogeneous structures provide extremely high degrees of freedom in electron emission properties, enabling pulsed electron source and one-dimensional electron source emission. In addition, this application directly integrates the two-dimensional material with optical fiber. The optical fiber transmits the laser and serves as a low-dimensional material carrier, providing a stable excitation source with tunable wavelength, polarization, and optical mode, suitable for various application scenarios. It eliminates the need for complex optical paths and features small size and high integration.

[0142] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0143] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. An electronic source, characterized in that, The electron source includes an optical fiber, a conductive connection layer, and an electron emission layer, wherein the conductive connection layer is disposed on the outer surface of the optical fiber; The electron emission layer is disposed on the laser emission surface of the optical fiber, and the electron emission layer includes an electron excitation layer electrically connected to the conductive connection layer, the electron excitation layer including at least one layer of two-dimensional material; The electron excitation layer is disposed on the laser emission path of the optical fiber, and the laser emitted from the optical fiber can directly irradiate the electron excitation layer, so that the electron excitation layer is excited by the laser to generate a photoelectric effect and emit electrons.

2. The electronic source as described in claim 1, characterized in that, The electron-excited layer satisfies at least one of the following conditions: (1) The thickness of the electron excitation layer is 0.1 nm to 100 nm; (2) The thickness of the two-dimensional material is 0.1 nm to 50 nm; (3) The two-dimensional material includes at least one of graphene, transition metal chalcogenide, two-dimensional perovskite, two-dimensional diamond and boron nitride.

3. The electronic source as described in claim 1, characterized in that, The electron excitation layer comprises at least two layers of two-dimensional material stacked sequentially along the laser emission direction of the optical fiber. The two-dimensional materials are all conductive. The two adjacent layers of two-dimensional materials may be the same or different.

4. The electronic source as described in claim 3, characterized in that, The crystal axis angle between two adjacent layers of the two-dimensional material is 0°~360°.

5. The electronic source as described in claim 1, characterized in that, The electron excitation layer is formed by splicing together at least two two-dimensional materials of different materials, and the laser of the optical fiber irradiates the splice of adjacent two-dimensional materials.

6. The electronic source as described in claim 1, characterized in that, The optical fiber is a solid fiber, a needle-tip fiber, a side-cut fiber, or a perforated fiber.

7. The electronic source according to any one of claims 1-6, characterized in that, The electron emission layer further includes an auxiliary layer, which is stacked on the side of the electron excitation layer closest to the optical fiber; or, The auxiliary layer is stacked on the side of the electron excitation layer away from the optical fiber.

8. The electronic source as described in claim 7, characterized in that, The auxiliary layer includes a transparent support layer, and the material of the transparent support layer includes at least one of boron nitride, mica and diamond. The thickness of the transparent support layer is 0.1nm~1000nm, and the light transmittance is ≥10%.

9. The electronic source as described in claim 7, characterized in that, The auxiliary layer includes a conductive support layer, and the electron excitation layer is electrically connected to the conductive connection layer through the conductive support layer. The material of the conductive support layer includes at least one of conductive metal and graphene; The thickness of the conductive support layer is 0.1 nm to 100 nm.

10. A method for preparing an electron source according to any one of claims 1-9, characterized in that, The preparation method includes: An electron source is prepared by forming an electron excitation layer composed of at least one two-dimensional material along the laser emission path of the optical fiber, and forming a conductive connection layer electrically connected to the electron excitation layer on the outer surface of the optical fiber.

11. An electron gun, characterized in that, The electron gun includes a housing, a gate, an anode, and an electron source as described in any one of claims 1-9; The electron source is fixed inside the housing, and the gate and the anode are sequentially arranged on the electron emission side of the electron source.

12. An application of the electronic source according to any one of claims 1-9, characterized in that, The application of the electron source includes at least one of an electron microscope, an electron beam lithography machine, an X-ray tube, a free-electron laser, and a display.

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