Electron source, electron gun and application of electron source

Abstract

The invention provides an electron source, an electron gun and application of the electron source, the electron source comprises an optical fiber, a conductive connection layer and an electron emission layer, the conductive connection layer is arranged on the outer surface of the optical fiber, and the electron emission layer comprises an electron excitation layer electrically connected with the conductive connection layer. The electron excitation layer comprises at least one of a zero-dimensional material, a one-dimensional material and a two-dimensional material, the electron excitation layer is arranged on a laser emitting path of the optical fiber, and laser emitted by the optical fiber can directly irradiate the electron emission layer, so that the electron excitation layer is excited by the laser and emits electrons. Low-dimensional materials such as a zero-dimensional material, a one-dimensional material and a two-dimensional material are adopted as materials of the electron excitation layer, and the low-dimensional materials have atomic-scale thickness, are free of dangling bonds and are stable in property, so that the low-dimensional materials have the characteristics of good stability, long service life and the like; moreover, the low-dimensional material can be directly integrated with the optical fiber, and the optical fiber can provide a stable excitation source with adjustable wavelength, polarization and optical mode, and can be suitable for different application scenes.

Description

Technical Field

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

[0002] An electron source is a device that generates vacuum electrons. Traditional electron sources are mainly classified into thermionic emission electron sources, field emission electron sources, and photoemission electron sources according to the excitation method. Thermionic emission electron sources mainly select metal materials. When heated to thousands of degrees Celsius, electrons are thermally excited to escape from the material surface to form vacuum electrons. Field emission electron sources mainly select metal tips. 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, it is necessary to provide an electron source, an electron gun, and an application of the electron source that can achieve high electron emission efficiency and good stability.

[0005] In a first aspect, this application provides an electron source. The electron source includes an optical fiber, a conductive connection layer, and an electron emission layer. 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. The electron excitation layer includes at least one of zero-dimensional materials, one-dimensional materials, and two-dimensional materials;

[0007] The electron excitation layer is disposed on the laser emission path of the optical fiber, and the laser emitted by the optical fiber can directly irradiate the electron emission 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 electron emission layer includes an auxiliary layer. The auxiliary layer is stacked on the side of the electron excitation layer close to the optical fiber; or,

[0010] The auxiliary layer is stacked on the side of the electron emission layer away from the optical fiber.

[0011] In some embodiments, the auxiliary layer is at least one of a conductive support layer and a heat dissipation support layer.

[0012] In some embodiments, the thickness of the auxiliary layer is 0.1 nm to 100 nm, and the light transmittance is ≥ 10%.

[0013] In some embodiments, the auxiliary layer includes a conductive support layer, and the conductive support layer is electrically connected to the conductive connection layer.

[0014] In some embodiments, 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 2000 nm, and the pulse power is 1 nW to 1 W.

[0015] In some embodiments, the included angle between the axial direction of the one-dimensional material in the electron excitation layer and the laser emission direction is 0 to 90°.

[0016] In some embodiments, the electron excitation layer includes at least one layer of two-dimensional material.

[0017] Optionally, the electron excitation layer includes at least two layers of two-dimensional materials stacked in sequence along the laser emission direction; or,

[0018] The electron excitation layer includes at least two two-dimensional materials with different materials connected to each other on the same plane.

[0019] In some embodiments, the material in the electron excitation layer includes one-dimensional material and zero-dimensional material disposed at the end and / or side of the one-dimensional material.

[0020] In some embodiments, the electron excitation layer includes zero-dimensional material and two-dimensional material, and the zero-dimensional material is disposed on the surface of the two-dimensional material.

[0021] In some embodiments, the electron excitation layer includes one-dimensional material and two-dimensional material, and the one-dimensional material is disposed on the surface of the two-dimensional material.

[0022] In some embodiments, the zero-dimensional material includes at least one of nanocrystals, fullerenes, and NV color centers.

[0023] In some embodiments, the one-dimensional material includes at least one of nanotubes, nanoribbons, and nanowires.

[0024] In some embodiments, the two-dimensional material includes at least one of graphene, black phosphorus, transition metal chalcogenides, and hexagonal boron nitride.

[0025] In some embodiments, the optical fiber is a solid-core optical fiber, a tip optical fiber, a side-cut optical fiber, or a porous optical fiber.

[0026] In a second aspect, the present application provides an electron gun, which includes a housing, a grid, an anode, and an electron source as described in the first aspect;

[0027] 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.

[0028] In a third aspect, the present application provides an application of the electron source as described in the first aspect. The application of the electron source includes at least one of an electron microscope, an electron beam exposure machine, an X-ray tube, a free electron laser, and a display.

[0029] Compared with the traditional technology, the present application has at least the following beneficial effects:

[0030] 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, with high electron emission efficiency. Moreover, the low-dimensional materials have no dangling bonds, are stable in nature and have a high melting point, are not easily damaged, can be applied to high-power excitation scenarios, and have characteristics such as good stability and long service life. There is a rich variety of low-dimensional materials, which support different types of electron emission requirements (high coherence, large beam current, narrow pulse width, etc.).

[0031] In addition, the low-dimensional materials can be directly integrated with optical fibers. The optical fibers transmit laser and, as the carriers 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 do not require a complex optical path, having characteristics such as small volume and high integration. Description of the Drawings

[0032] Figure 1 It is a schematic structural diagram of the electron source provided in Embodiment 1 of the present application. Among them, 110a - solid-core optical fiber; 120a - electron excitation layer; 130a - conductive connection layer.

[0033] Figure 2 It is a schematic structural diagram of the electron source provided in Embodiment 2 of the present application. Among them, 110b - tip optical fiber; 120b - electron excitation layer; 130b - conductive connection layer.

[0034] Figure 3 It is a schematic structural diagram of the electron source provided in Embodiment 3 of the present application. Among them, 110c - solid-core optical fiber; 120c - electron excitation layer; 130c - conductive connection layer; 140c - auxiliary layer.

[0035] Figure 4 It is a schematic structural diagram of the electron source provided in Embodiment 5 of the present application. Among them, 110d - solid-core optical fiber; 120d - electron excitation layer; 130d - conductive connection layer.

[0036] Figure 5Schematic structural diagram of the electron source provided in Embodiment 6 of the present application, where 110e is a side-cut optical fiber; 120e is an electron excitation layer; 130e is a conductive connection layer.

[0037] Figure 6 Schematic structural diagram of the electron source provided in Embodiment 7 of the present application, where 110f is a solid-core optical fiber; 120f is an electron excitation layer; 130f is a conductive connection layer; 140f is an auxiliary layer.

[0038] Figure 7 Schematic structural diagram of the electron source provided in Embodiment 8 of the present application, where 110g is a solid-core optical fiber; 120g is an electron excitation layer; 130g is a conductive connection layer.

[0039] Figure 8 Schematic internal structural diagram of the electron gun provided in an embodiment of the present application, where 100 is an electron source; 200 is a grid; 300 is an anode. Detailed implementation manners

[0040] The following further describes the present application in detail in combination with the implementation manners and embodiments. These implementation manners and embodiments are only used to illustrate the present application and not to limit the scope of the present application. The purpose of providing these implementation manners and embodiments is to make the understanding of the disclosed content of the present application more thorough and comprehensive. It should also be understood that the present application can be implemented in many different forms and is not limited to the implementation manners and embodiments described herein. Those skilled in the art can make various changes or modifications without departing from the connotation of the present application, and the equivalent forms obtained also fall within the protection scope of the present application. In addition, in the following description, a large number of specific details are given to provide a more thorough understanding of the present application. It should be understood that the present application 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 those skilled in the technical field to which the present application belongs. The terms used in the description of the present application herein are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0042] In the present application, "optionally", "optional", "option" mean having or not having, that is, any one selected from two parallel options of "having" or "not having". If "optional" appears multiple times in a technical solution, without special instructions and without contradictions or mutual restrictions, each "optional" is independent of each other.

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

[0044] In this application, among the technical features described in an open-ended manner, it includes a closed technical solution composed of the listed features, as well as an open technical solution containing the listed features.

[0045] In this application, regarding numerical intervals (i.e., numerical ranges), unless otherwise specified, the distribution of the selectable numerical values within the numerical interval is considered continuous and includes the two numerical endpoints of the numerical interval (i.e., the minimum value and the maximum value), as well as each numerical value between these two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to the integers within the numerical interval, it includes the two endpoint integers of the numerical range, as well as each integer between the two endpoints, which is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical ranges disclosed in this application should be understood to include any and all sub-ranges subsumed therein. The "numerical values" in the numerical interval can be any quantitative values, such as numbers, percentages, ratios, etc. The "numerical interval" is allowed to broadly include quantitative intervals such as percentage intervals, ratio intervals, and ratio value intervals.

[0046] All the documents mentioned in this application are cited as references in this application, just as if each document is cited separately as a reference. Unless it conflicts with the invention purpose and / or technical solution of this application, the cited documents related to this application are cited for all their contents and all their purposes. When this application involves citing documents, the definitions of relevant technical features, terms, nouns, phrases, etc. in the cited documents are also cited. When this application involves citing documents, the examples and preferred ways of the relevant technical features cited can also be incorporated as references into this application, but only to the extent that this application can be implemented. It should be understood that when the cited content conflicts with the description in this application, this application shall prevail or be amended adaptively according to the description in this application.

[0047] In the prior art, materials with metallic properties such as tungsten filaments and lanthanum hexaboride are mainly selected as thermionic electron sources. When heated to thousands of degrees Celsius, electrons are thermally excited to escape from the material surface to form vacuum electrons. Field emission electron sources mainly select metal tips such as tungsten. Under the action of a strong external electric field, the tip discharge effect is generated. Among them, the electron beam emitted by the thermionic electron source can work in a relatively poor vacuum environment, with good environmental adaptability and stability, but with 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 vibrations. Whether it is a thermionic electron source or a field emission electron source, the regulation of electron emission properties is limited, and it is impossible to balance coherence, pulsatility, emission efficiency, and stability.

[0048] The photoemission electron source uses metal materials such as Au as the material of the electron emission layer, with a thickness of more than 50 nm, even reaching hundreds of nanometers. However, the inventors of the present application have found through research that the electron emission layer of the metal material has a large thickness, and the distance between the surface directly irradiated by the laser (the bottom layer of the electron emission layer) and the surface where electrons are emitted (the surface layer of the electron emission layer) in the electron emission layer is relatively far (50 nm to hundreds of nanometers). During the process of electrons excited from the bottom layer passing through the electron emission layer, they are easily affected by metal lattice scattering, thereby affecting the emission efficiency. Moreover, the metal material is easily damaged under high-power laser irradiation, affecting the service life of the electron emission layer, and thus affecting the emission efficiency and stability of electrons. Some electron sources use the method of laser side incidence to excite electrons. Compared with laser back incidence, side incidence requires the modification of the vacuum chamber, and the irradiation method has high operation difficulty and problems such as unstable excitation conditions.

[0049] 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 differences between graphene laser regulation and graphene electron emission. The graphene photoexcited electron source is based on the photoelectric effect to excite and emit electrons, while graphene laser regulation is based on the principle of light absorption to regulate the output parameters of the laser. Specifically, 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. In laser regulation, the graphene saturable absorber 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 an optical fiber laser, when the light power passing through the graphene saturable absorber exceeds its saturation absorption threshold during the circulation of light in the resonator, due to the saturable absorption effect, the light intensity in the cavity will instantaneously drop below the saturation absorption threshold, and this part of the dropped light energy is output in the form of pulses from the optical splitter of the cavity.

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

[0051] This application uses low-dimensional materials such as zero-dimensional materials, one-dimensional materials, and two-dimensional materials as the materials of the electron emission 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 the characteristics of 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.

[0052] In the first aspect of this application, an electron source is provided. The electron source includes an optical fiber, a conductive connection layer, and an electron emission layer. 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 to connect the low-dimensional material with the external circuit, form a complete circuit, realize the replenishment of charges and electric field control, and the electron emission layer can be excited to emit electrons under laser irradiation to form an electron beam;

[0054] The electron excitation layer includes at least one of a zero-dimensional material, a one-dimensional material, and a two-dimensional material;

[0055] The electron excitation layer is disposed on the laser output path of the optical fiber, and the laser output from the optical fiber can directly irradiate the electron emission layer, so that the electron excitation layer is excited by the laser and emits electrons.

[0056] It should be noted that in this application, low-dimensional materials refer to zero-dimensional materials, one-dimensional materials, or two-dimensional materials.

[0057] This application uses low-dimensional materials such as zero-dimensional materials, one-dimensional materials, or two-dimensional materials as the materials for the electron excitation layer. Low-dimensional materials have an atomic-level thickness, and the back-incident electrons can be emitted without passing through in-body transmission, with high electron emission efficiency; moreover, low-dimensional materials have no dangling bonds, are stable in nature and have a high melting point, are not easily damaged, can be applied to scenarios of high-power excitation, and have characteristics such as good stability and high service life.

[0058] In addition, low-dimensional materials can be directly integrated with optical fibers. The optical fibers transmit laser light and, as the carriers of low-dimensional materials, can provide a stable excitation source with adjustable wavelength, polarization, and optical mode, can be applied to different application scenarios, and do not require a complex optical path, having characteristics such as small volume and high integration.

[0059] Among them, zero-dimensional materials have typical discrete energy levels. Under the action of laser excitation, electrons are mainly tunnel-excited from the discrete energy levels, and electrons with very high monochromaticity can be excited, and the emitted electrons have concentrated energy and small energy dispersion. One-dimensional materials have the characteristic of a small curvature radius (nanoscale), can enhance the light-matter interaction and provide a large field enhancement factor, ensure multi-photon emission, optical field emission, etc., and are applied to scenarios that require a high-brightness electron source. Two-dimensional materials have the characteristic of an atomic layer thickness. During the process of the laser interacting with two-dimensional materials, it hardly affects the light transmission mode and has high stability; moreover, the excited electrons can be directly emitted without internal scattering in the material, ensuring the purity of the emitted electrons and an extremely narrow pulse width.

[0060] In this application, zero-dimensional materials refer to substances with dimensions in the nanoscale in all three spatial dimensions, and electrons cannot move freely; one-dimensional materials refer to materials in which electrons can move freely only in one non-nanoscale direction; two-dimensional materials refer to materials in which electrons can move freely only in two non-nanoscale dimensions (i.e., planar motion). The nanoscale refers to 0.1 nm to 100 nm. Zero-dimensional materials, one-dimensional materials, and two-dimensional materials can be excited to emit electrons under the action of laser excitation.

[0061] It should be noted that in this application, the light output path of the optical fiber refers to the path where the laser light irradiates in the optical fiber. Taking a solid-core optical fiber as an example, the laser output position of the solid-core optical fiber is located at the end face of the core, that is, the electron emission layer can be arranged at the core; taking a side-cut optical fiber as an example, the laser output position of the side-cut optical fiber is located on the side-cut side of the side-cut optical fiber, that is, the electron emission layer can be arranged at the side-cut. It can be understood that in this application, the electron emission layer can be in direct contact with the laser output surface of the optical fiber, or can be supported by other structural layers, that is, as long as the laser light output from the optical fiber can irradiate on the electron emission layer.

[0062] It should also be noted that the purpose of the electrically conductive connection layer being electrically connected to the electron emission layer in this application is to connect the low-dimensional material to the external circuit to form a complete circuit and achieve charge replenishment and electric field control. As an implementation manner, the electrically conductive connection layer in this application can be directly connected to the electron emission layer. In other implementation manners, the electrically conductive connection layer and the electron emission layer can also be electrically connected through other conductive structures. For example, taking a solid-core optical fiber as an example, the electrically conductive connection layer is disposed on the side surface of the solid-core optical fiber, the electron emission layer is disposed at the core of the solid-core optical fiber, and the electrically conductive connection layer is electrically connected to the electron emission layer, and there is no electrically conductive connection layer at the core.

[0063] In some embodiments, the zero-dimensional material, one-dimensional material, or two-dimensional material independently includes a doping element.

[0064] This application improves the conductivity of the low-dimensional material, changes the work function, and adjusts the electron emission performance by doping elements into the low-dimensional material. For example, alkali metals and alkaline earth metal elements can improve the conductivity of the low-dimensional material and at the same time reduce the work function of the low-dimensional material to increase 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 range.

[0065] Optionally, the doping element includes at least one of alkali metals, alkaline earth metals, transition metals, rare earth elements, halogen elements, and light elements. The light elements include at least one of B, C, N, and O.

[0066] In some embodiments, the electrically conductive connection layer is provided with an electrode. Optionally, the electrically conductive connection layer can completely cover the outer surface of the optical fiber or partially cover the outer surface of the optical fiber, and there is no electrically conductive connection layer on the light output path of the laser. Further optionally, the thickness of the electrically conductive connection layer is 10 nm to 1 μm, for example, it can be 10 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, or 1 μm.

[0067] 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.

[0068] In some embodiments, the electron emission layer further includes an auxiliary layer, and the auxiliary layer is stacked on the side of the electron excitation layer close to the optical fiber; or,

[0069] The auxiliary layer is stacked on the side of the electron excitation layer away from the optical fiber.

[0070] 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 emission layer, that is, the electron excitation layer is disposed on the auxiliary layer; or, when the electron excitation layer cannot be directly connected and conductively connected to the conductive connection layer, it is connected to the conductive connection layer through the conductive auxiliary layer, and the auxiliary layer is used to achieve electron conduction between the electron excitation layer and the conductive connection layer.

[0071] Optionally, the auxiliary layer includes at least one of a conductive support layer and a heat dissipation support layer.

[0072] Optionally, the thickness of the auxiliary 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.

[0073] Optionally, the light transmittance of the auxiliary layer is ≥10%, for example, it can be 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or 100%.

[0074] In some embodiments, the auxiliary layer includes a conductive support layer, and the material of the conductive support layer includes a conductive metal. Optionally, the laser wavelength in the optical fiber is 200 nm to 2000 nm, for example, it can be 200 nm, 400 nm, 600 nm, 800 nm, 1000 nm, 1200 nm, 1400 nm, 1600 nm, 1800 nm or 2000 nm; the pulse power is 1 nW to 1 W, for example, it can be 1 nW, 100 nW, 1 μW, 10 μW, 100 μW, 1 mW, 10 mW, 100 mW or 1 W.

[0075] In this application, the auxiliary layer 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.

[0076] In some embodiments, the auxiliary layer is disposed on the side where the electron excitation layer emits electrons, and the thickness of the auxiliary layer is 0.1 nm to 10 nm. Thereby reducing the influence of the auxiliary layer on the electron emission effect.

[0077] In some embodiments, the angle between the axial direction of the one-dimensional material in the electron excitation layer and the emission direction of the laser is 0 to 90°, for example, it can be 0°, 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80° or 90°.

[0078] In some embodiments, the axial direction of the one-dimensional material is the same as the laser emission direction, enabling point emission of the electron source with high resolution. If a low-density arrangement of one-dimensional materials is adopted, the emitted electrons have low energy dispersion and high brightness. If a high-density arrangement of one-dimensional materials is adopted, a large electron beam current of the electron source can be achieved. Herein, low density refers to the number of one-dimensional materials per unit area. For example, a density less than 1 per nm 2 is a low density, and greater than 1 per nm 2 is a high density.

[0079] In some embodiments, the axial direction of the one-dimensional material forms an angle with the laser emission direction. The angle can be a right angle or an acute angle. Laser excitation of the one-dimensional material can generate a linear electron source.

[0080] In some embodiments, the electron excitation layer includes at least two two-dimensional materials stacked in sequence along the laser emission direction, or the electron emission layer includes at least two two-dimensional materials with different materials connected to each other on the same plane.

[0081] In some embodiments, at least two two-dimensional materials are stacked, or at least two two-dimensional materials are joined to form the same plane. Further, the materials of adjacent two-dimensional materials are different, thereby forming a vertical heterojunction or a planar heterojunction. The heterojunction structure can enhance the interaction between light and two-dimensional materials, realizing efficient electron emission at low laser power. Moreover, 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.

[0082] In some embodiments, 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.

[0083] In this application, by combining zero-dimensional materials with one-dimensional materials and disposing the zero-dimensional materials at the ends or sides of the one-dimensional materials, that is, using zero-dimensional materials to modify the surface structure of one-dimensional materials. Both zero-dimensional materials and one-dimensional materials have typical discrete energy levels. Under the action of laser, electrons are mainly excited by tunneling from the discrete energy levels, and the emitted electrons have characteristics such as concentrated energy, small energy dispersion, and high emission efficiency.

[0084] In some embodiments, the electron excitation layer includes zero-dimensional materials and two-dimensional materials, and the zero-dimensional materials are disposed on the surface of the two-dimensional materials.

[0085] In this application, the zero-dimensional materials are disposed on the surface of the two-dimensional materials. The two-dimensional materials can not only serve as a support layer for carrying the zero-dimensional materials, but also avoid the addition of a conductive layer by using conductive two-dimensional materials. That is, the two-dimensional materials can serve as an auxiliary layer for the zero-dimensional materials to achieve the functions of support and conductivity.

[0086] In some embodiments, 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; optionally, the included angle between the axial direction of the one-dimensional material and the surface of the two-dimensional material is 0 to 90°.

[0087] In this application, the one-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 one-dimensional material, but also avoid the addition of a conductive layer 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.

[0088] In some embodiments, the zero-dimensional material includes at least one of quantum dots, fullerenes, NV color centers, and nanocrystals. Among them, the NV color center refers to a nitrogen vacancy color center, and the quantum dots include at least one of carbon quantum dots, CdSe colloidal quantum dots, and GaAs semiconductor quantum dots.

[0089] In some embodiments, the one-dimensional material includes at least one of nanotubes, nanoribbons, and nanowires. Optionally, the nanowires include at least one of gold nanowires, semiconductor (GaAs) nanowires, and Te quantum wires; the nanotubes include carbon nanotubes.

[0090] In some embodiments, the two-dimensional material includes at least one of graphene, black phosphorus, transition metal chalcogenides, and hexagonal boron nitride. Optionally, the transition metal chalcogenides include at least one of WS2, WSe2, and NbSe2.

[0091] In some embodiments, the optical fiber is a solid-core optical fiber, a tip optical fiber, a side-cut optical fiber, or a porous optical fiber.

[0092] In some embodiments, the optical fiber is a tip optical fiber. In this application, the low-dimensional material is disposed on the tip optical fiber. Due to the tip geometric structure of the tip optical fiber, the field emission enhancement factor is improved, and a higher-brightness electron source can be obtained. The low-dimensional material can be a two-dimensional material. Further, at least one of a zero-dimensional material and a one-dimensional material is disposed on the two-dimensional material, thereby realizing functions such as high brightness, low energy dispersion, and narrow pulse width.

[0093] In some embodiments, the optical fiber is a side-cut optical fiber. In this application, the low-dimensional material is disposed on the side-cut surface of the side-cut optical fiber, and the evanescent wave leaking from the core interacts with the low-dimensional material in the horizontal direction. For example, when the low-dimensional material is a two-dimensional material, edge states similar to one-dimensional materials are obtained at the side-cut, forming a new electron emission structure to achieve functions such as high brightness, low energy dispersion, and narrow pulse width; when the low-dimensional material is a one-dimensional material, edge states of zero-dimensional materials are obtained at the side-cut, forming a new electron emission structure to achieve functions such as high brightness, low energy dispersion, and narrow pulse width; when the low-dimensional material is a combination of two-dimensional materials, one-dimensional materials, and zero-dimensional materials, the energy band of the two-dimensional material can be modulated by doping one-dimensional and zero-dimensional materials, improving the interaction between light and materials, and realizing electron emission with functions such as high brightness, low energy dispersion, and narrow pulse width.

[0094] In some embodiments, the optical fiber is a holey optical fiber. The holey optical fiber in this application is a type of optical fiber with microstructures or completely hollow, including photonic crystal fibers, anti-resonant fibers, or capillary fibers, etc. The low-dimensional material can be disposed in the pores or pore walls of the holey optical fiber, enabling the laser to have a longer interaction distance with the low-dimensional material, thereby achieving high-brightness electron emission. Since the holey optical fiber itself has a special light transmission mode, and different types or dimensions of materials can continue to grow or be transferred in the pores or pore walls where the low-dimensional material has already grown or been filled to form a heterojunction, multifunctional electron emission can be realized.

[0095] In some embodiments, the optical fiber is a solid-core optical fiber. In this application, the low-dimensional material is disposed at the core of the solid-core optical fiber, and the evanescent wave leaking from the core can interact with the low-dimensional material surrounding the optical fiber. A longer interaction distance between light and materials can be achieved in this system to realize high-brightness electron emission. In addition, different diameters of micro-nano optical fibers can be drawn, enabling light of different modes and intensities to interact with the low-dimensional material to realize electron emission with precisely regulated parameters. In addition, different types or dimensions of materials can continue to grow or be transferred on the grown or transferred low-dimensional material to form a heterojunction to realize multifunctional electron emission.

[0096] It should be noted that this application does not make 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 actual usage requirements.

[0097] In some embodiments, the electron excitation layer is formed by at least one of dry transfer, wet transfer, and direct growth.

[0098] In some embodiments, the electron excitation layer is prepared by dry transfer. The preparation method includes: transferring zero-dimensional materials, one-dimensional materials, or two-dimensional materials to the tape by mechanical exfoliation, and transferring the zero-dimensional materials, one-dimensional materials, or two-dimensional materials to the laser output side of the optical fiber through the tape.

[0099] In some embodiments, the electron excitation layer is prepared by wet transfer. The preparation method includes: directly preparing zero-dimensional materials, one-dimensional materials or two-dimensional materials in a solution and floating them on the liquid surface, and using an optical fiber to contact the materials on the liquid surface and drying.

[0100] In some embodiments, the electron excitation layer is prepared by direct growth. The preparation method includes: directly preparing an electron emission layer on the laser emission side of the optical fiber by at least one of chemical vapor deposition, physical vapor deposition, molecular beam epitaxy, and liquid filling.

[0101] The second aspect of the present application provides an electron gun, which includes a housing, a grid, an anode, and an electron source as described in the first aspect;

[0102] 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.

[0103] It should be noted that in the present application, the grid is used to limit the shape of the electron beam, and the anode 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 grid and the space charge of the electrons themselves, forming an electron beam with a certain shape and emitting from the anode for use.

[0104] The third aspect of the present application provides an application of the electron source as described in the first aspect. The application of the electron source includes at least one of an electron microscope, an electron beam exposure machine, an X-ray tube, a free electron laser, and a display.

[0105] The embodiments of the present application will be described in detail below. It should be understood that these embodiments are only used to illustrate the present application and not to limit the scope of the present application. For the experimental methods without specific conditions in the following embodiments, the guidance given in the present application is preferentially referred to, and it can also be carried out according to the experimental manuals or conventional conditions in the art, or according to the conditions recommended by the manufacturer, or referring to the experimental methods known in the art.

[0106] In the following embodiments, the conductive connection layer is a gold layer covering the side surface of the optical fiber with a thickness of 60 nm, and the conductive connection layer is in contact connection with the auxiliary layer or the electron emission layer.

[0107] Example 1

[0108] Polycarbonate propylene carbonate and anisole with a mass ratio of 1:8 are dropped onto a silicon wafer, and spin-coated for 1 minute at a speed of 1500 r / min using a spin coater, and then baked at 60 °C for 2 minutes to obtain a PPC film on the silicon wafer;

[0109] Graphene was obtained from bulk raw materials using the mechanical exfoliation method with a first tape; then the first tape with graphene was pasted onto a PPC film. After pressing with a cotton swab, the low-dimensional material was brought into full contact with the PPC film. The graphene to be transferred was selected using a light microscope.

[0110] A second tape was taken and a square hole with dimensions of 3 mm × 3 mm was made in the middle of the second tape. The second tape was attached to the PPC film so that the graphene to be transferred was located at the opening position of the second tape. After pressing with a cotton swab, the PPC film was fully attached to the second tape; the second tape and the PPC film were lifted, and the PPC film was peeled off from the first tape, and the graphene was transferred onto the PPC film.

[0111] The second tape and the PPC film were fixed on a glass slide with a central circular hole (diameter 5 mm). The square hole of the second tape was centered at the central circular hole. A heating sheet was set on the side of the glass slide away from the PPC film and placed under a light microscope with the side of the PPC with graphene facing down. First, the glass slide was heated to 40 °C to smooth out the wrinkles of the PPC film. Then, the end face of a solid-core optical fiber with a conductive connection layer was oriented towards the side of the PPC with graphene and brought into contact with the PPC film. The heating temperature was increased to 60 °C and the optical fiber was further moved up by 50 μm to ensure full contact between the end face of the optical fiber and the PPC film. The temperature was raised to 130 °C to melt the PPC film. The optical fiber was removed and immersed in acetone to clean the PPC film remaining on the end face of the optical fiber. As Figure 1 shown, an electron excitation layer 120a made of graphene with a thickness of 1 nm was obtained on the end face of the solid-core optical fiber 110a. The graphene was electrically connected to the conductive connection layer 130a to obtain the described electron source.

[0112] Example 2

[0113] Graphene was grown on a substrate by the CVD (chemical vapor deposition) method. The substrate with graphene was placed in a water tank filled with deionized water to make the graphene float on the water surface. The tip side of the tip optical fiber was brought into contact with the graphene from above the water surface. After full contact, the tip side was immersed in water and then taken out and dried for the tip optical fiber. As Figure 2 shown, an electron excitation layer 120b made of graphene with a thickness of 0.4 nm was obtained on the tip side of the tip optical fiber 110b. Then, a conductive connection layer 130b was prepared on the tip optical fiber 110b to electrically connect the graphene to the conductive connection layer 130b to obtain the described electron source.

[0114] Example 3

[0115] As Figure 3As shown in the figure, an auxiliary layer 140c with a thickness of 10 nm and made of gold is deposited on the end face of the solid-core optical fiber 110c having a conductive connection layer 130c; then, carbon quantum dots are grown on the surface of the auxiliary layer 140c by CVD method to obtain an electron excitation layer 120c on the surface of the auxiliary layer 140c; the auxiliary layer 140c is electrically connected to the conductive connection layer 130c to obtain the electron source described above.

[0116] Example 4

[0117] An auxiliary layer with a thickness of 10 nm and made of gold is deposited on the end face of the hollow-core optical fiber having a conductive connection layer; then, carbon nanotubes are grown on the surface of the auxiliary layer by CVD method, and the axial directions of the carbon nanotubes are all perpendicular to the plane of the auxiliary layer, and an electron excitation layer is prepared on the surface of the auxiliary layer; the auxiliary layer is electrically connected to the conductive connection layer to obtain the electron source described above.

[0118] Example 5

[0119] As Figure 4 shown in the figure, graphene with a thickness of 1 nm is grown by CVD on the end face of the solid-core optical fiber 110d having a conductive connection layer 130d; then, carbon nanotubes are grown on the surface of the graphene by CVD method, and the axial direction of the carbon nanotubes is parallel to the plane of the graphene, and an electron excitation layer 120d is obtained on the end face of the solid-core optical fiber 110d; the graphene is electrically connected to the conductive connection layer 130d to obtain the electron source described above.

[0120] Example 6

[0121] As Figure 5 shown in the figure, graphene with a thickness of 1 nm is grown by CVD on the side cross-section of the side-cut optical fiber 110e, and then molybdenum disulfide (MoS2) quantum dots are prepared on the surface of the graphene by CVD method to obtain an electron excitation layer 120e; a conductive connection layer is provided at the side-cut optical fiber 110e, and the conductive connection layer 130e is electrically connected to the graphene to obtain the electron source described above.

[0122] Example 7

[0123] As Figure 6 shown in the figure, an auxiliary layer 140f with a thickness of 10 nm and made of gold is deposited and grown on the end face of the solid-core optical fiber 110f having a conductive connection layer 130f, and carbon nanotubes are prepared on the surface of the auxiliary layer 140f by CVD, and the axial direction of the carbon nanotubes is perpendicular to the surface of the auxiliary layer; then, molybdenum disulfide (MoS2) quantum dots are grown on the carbon nanotubes by CVD to obtain an electron excitation layer 120f, and the auxiliary layer 140f is electrically connected to the conductive connection layer 130f to obtain the electron source described above.

[0124] Example 8

[0125] AsFigure 7 As shown in the figure, graphene and black phosphorus are successively grown on the end face of the solid-core optical fiber 110g with the conductive connection layer 130g. The thickness of the graphene is 1 nm, and the thickness of the black phosphorus is 1 nm, forming an electron excitation layer 120g stacked by graphene and black phosphorus. The graphene is electrically connected to the conductive connection layer 130g to obtain the electron source.

[0126] Comparative Example 1

[0127] An electron source is prepared according to the structure of Example 1, except that the electron emission layer in Example 1 is replaced with a gold layer with a thickness of 100 nm, and the gold layer is prepared by deposition.

[0128] Comparative Example 2

[0129] An electron source is prepared according to the structure of Comparative Example 1, except that the electron emission layer in Comparative Example 1 is replaced with a gold layer with a thickness of 1 nm.

[0130] As Figure 8 shown, the electron sources 100 prepared by the above-mentioned examples and comparative examples are assembled into an electron gun. The electron gun further includes a housing, a grid 200, and an anode 300. The performance of the prepared electron gun is tested. The test methods include:

[0131] Stability test: When the excitation power is 50% of the damage power, the vacuum degree is 2×10 -5 Pa, and the continuous emission current is 1 h. After removing the bad points, calculate the difference between the maximum current and the minimum current and the average current, that is, the stability parameter = (maximum current - minimum current) / average current.

[0132] Lifetime test: When the excitation power is 50% of the damage power, the vacuum degree is 2×10 -5 Pa, and the continuous emission current is measured until the time when the current decays to less than 10% of the initial value, which is defined as the lifetime.

[0133] Working vacuum degree test: When the excitation power is 50% of the damage power, the continuous emission current is measured, and the working environment vacuum degree of the electron gun is gradually increased until the current shows a rapid decay (the rapid decay is defined as the current decaying by more than 50% within 1 min). At this time, the vacuum degree is defined as the working vacuum degree.

[0134] Among them, the damage power refers to the laser power when the material is damaged under the irradiation of a 100 fs pulsed laser. For example, the damage power of graphene is 0.25 J / cm 2 , and the damage threshold of gold is 0.1 J / cm 2 .

[0135] The test results are shown in Table 1.

[0136] Table 1

[0137]

[0138] It can be seen from the above table that:

[0139] In this application, low-dimensional materials such as zero-dimensional materials, one-dimensional materials, and two-dimensional materials have atomic-level dimensions. Electrons incident from the back can be emitted into the vacuum without passing through in-body transmission, making them very suitable for ultrafast electron sources with narrow pulse widths. Moreover, low-dimensional materials and different types of optical fibers can be directly integrated, bringing ultra-high stability and integration. In addition, low-dimensional materials have no dangling bonds, are stable, have a high melting point, and are not easily damaged, making them suitable for high-power-excited large-beam electron sources. When low-dimensional materials and tips are integrated, very sharp optical fiber tips can be obtained, 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, there are significant advantages in integrating low-dimensional materials with optical fibers. Optical fibers can not only transmit laser light, but also, as carriers of low-dimensional materials, provide a stable excitation source with adjustable wavelength, polarization, and optical mode, can be applied to different application scenarios, and do not require a complex optical path, having the characteristics of small volume and high integration. When integrated with other devices, stable integration can be achieved without cracking and modifying vacuum electronic devices.

[0140] 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, it should be considered as falling within the scope described in this specification.

[0141] The above-described embodiments merely represent several implementation manners of this application. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of this application, several modifications and improvements can still be made, and these all belong to the protection scope of this application. Therefore, the protection scope of this application patent shall be subject to the appended claims.

Claims

1. An electron source, characterized in that, The electron source includes an optical fiber, a conductive connection layer, and an electron emission layer. The conductive connection layer is disposed on the outer surface of the optical fiber; The electron emission layer includes an electron excitation layer electrically connected to the conductive connection layer. The electron excitation layer includes at least one of a zero-dimensional material, a one-dimensional material, and a 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 emission layer, so that the electron excitation layer is excited by the laser and emits electrons.

2. The electron source according to claim 1, wherein The thickness of the electron excitation layer is 0.1 nm to 100 nm.

3. The electron source according to claim 1, wherein The electron emission layer includes an auxiliary layer, and the auxiliary layer is stacked on one side of the electron emission layer close to the optical fiber; or, The auxiliary layer is stacked on one side of the electron excitation layer away from the optical fiber.

4. The electron source according to claim 3, wherein The auxiliary layer satisfies at least one of the following conditions: (1) The auxiliary layer includes at least one of a conductive support layer and a heat dissipation support layer; (2) The thickness of the auxiliary layer is 0.1 nm to 100 nm, and the light transmittance is ≥10%.

5. The electron source according to claim 3, wherein The auxiliary layer includes a conductive support layer, and the conductive support layer is electrically connected to the conductive connection layer.

6. The electron source according to claim 3, 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 2000 nm, and the pulse power is 1 nW to 1 W.

7. The electron source according to claim 1, characterized in that, The axial direction of the one-dimensional material in the electron emission layer forms an angle of 0 to 90° with the emission direction of the laser.

8. 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.

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

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

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

12. The electron source according to claim 1, wherein The electron source also satisfies at least one of the following conditions: (1) The zero-dimensional material includes at least one of a quantum dot, fullerene, NV color center, and nanocrystal; (2) The one-dimensional material includes at least one of a nanotube, nanoribbon, and nanowire; (3) The two-dimensional material includes at least one of graphene, black phosphorus, transition metal chalcogenide, and hexagonal boron nitride.

13. The electron source according to any one of claims 1 to 12, characterized in that, The optical fiber is a solid-core optical fiber, a tip optical fiber, a side-cut optical fiber, or a porous optical fiber.

14. 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 1-13; The electron source is fixed in the housing, and the grid and the anode are sequentially disposed on the electron emission side of the electron source.

15. An application of the electron source according to any one of claims 1-13, characterized in that, The applications of the electron source include 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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