An ultra-low-energy monochromated electron beam generation and transport device

Abstract

The application discloses an ultralow-energy monochromatic electron beam generation and transmission device, and relates to the technical field of electron optical instruments, which comprises the following units arranged in sequence along an electron beam transmission path: an electron generation unit for generating an initial electron beam; an injection lens unit for receiving the initial electron beam generated by the electron generation unit; a monochromator unit having an inlet and an outlet and being used for energy screening of the electron beam from the injection lens unit to reduce energy spread thereof; and a deceleration and focusing lens unit for receiving the monochromatized electron beam output from the outlet of the monochromator unit. The device can output an ultralow-energy electron beam with a continuously adjustable energy of 0 eV to 5 eV through the cooperative work of the electron generation unit, the injection lens unit, the monochromator unit and the deceleration and focusing lens unit, and the energy spread is better than 90 meV, thereby improving beam monochromaticity and transmission efficiency.

Description

Technical Field

[0001] This invention relates to the field of electronic optical instrument technology, and in particular to an ultra-low energy monochromatic electron beam generation and transmission device. Background Technology

[0002] Ultra-low energy electron beam sources are core components of surface analysis techniques such as electron diffraction, energy dispersive spectroscopy, and microscopic imaging. Electron beams with energies below 5 electron volts are sensitive to sample surface structures and cause low radiation damage, making them a key tool for non-destructive characterization of sensitive materials such as organic semiconductors and soft matter. With the advancement of research on low-dimensional and flexible materials, the industry's demand for such electron sources with adjustable energy and excellent monochromaticity is becoming increasingly urgent.

[0003] Currently, the industry mostly uses the deceleration field method to prepare low-energy electron beams. This method first generates a high-energy electron beam of tens to hundreds of electron volts, and then reduces it to the target energy through a deceleration lens. Electron emission mostly relies on thermionic emission or Schottky field emission mechanisms. However, thermionic emission has an inherent energy dispersion problem, with an energy width of 0.3 to 2.0 electron volts. The resulting "thermal blurring effect" directly limits the resolution of atomic-scale imaging and subelectron volt energy spectrum analysis.

[0004] Although existing monochromatic electron sources use a post-monochromatic unit and a speed reducer to optimize monochromaticity, the exit slit causes severe beam loss. During long-distance transmission, they are also susceptible to aberrations and space charge effects, making it impossible to balance high monochromaticity and signal strength. Especially in the ultra-low energy range of 0 electron volts to 5 electron volts, existing technologies struggle to achieve both continuously adjustable energy and high monochromaticity. The parameters of the dispersive element need to be optimized simultaneously during energy adjustment, and there is currently a lack of effective collaborative control mechanisms. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is that existing ultra-low energy electron beam sources have large energy dispersion, poor monochromaticity, significant beam loss and aberration, and it is difficult to balance tunability and monochromaticity in the range of 0 electron volts to 5 electron volts, and their compatibility and versatility are insufficient.

[0006] The above-mentioned technical problems are solved by the following technical solution: This invention proposes an ultra-low energy monochromatic electron beam generation and transmission device, which includes the following components arranged sequentially along the electron beam transmission path: An electron generating unit is used to generate an initial electron beam; An injection lens unit is used to receive the initial electron beam generated by the electron generating unit; A monochromator unit, having an inlet slit and an outlet slit, is used to filter the energy of the electron beam from the injection lens unit to reduce the energy broadening of the output electron beam; A deceleration and focusing lens unit is used to receive the monochromatic electron beam output from the monochromator unit; the electrode voltages of the deceleration and focusing lens unit are proportionally linked so that the kinetic energy of the output electron beam is adjustable within the range of 0 electron volts to 5 electron volts.

[0007] The injection lens unit focuses the initial electron beam and injects it into the entrance of the monochromator unit, while the deceleration and focusing lens unit decelerates and focuses the monochromatic electron beam before outputting it.

[0008] As a preferred embodiment of the ultra-low energy monochromatic electron beam generation and transmission device of the present invention, active edge field compensation electrodes are symmetrically integrated on the outer side of the inlet and the outer side of the outlet of the monochromator unit.

[0009] As a preferred embodiment of the ultra-low energy monochromatic electron beam generation and transmission device of the present invention: the injection lens unit is an electrostatic lens composed of multiple electrodes, and the injection lens unit is used to collect the initial electron beam with a divergence angle and converge the electrons to the entrance slit of the monochromator unit.

[0010] As a preferred embodiment of the ultra-low energy monochromatic electron beam generation and transmission device of the present invention: the deceleration and focusing lens unit is used to decelerate the kinetic energy of the electron beam from the passing energy of the monochromator unit to a preset low energy; During deceleration, the deceleration and focusing lens unit can maintain the convergence of the electron beam.

[0011] As a preferred embodiment of the ultra-low energy monochromatic electron beam generation and transmission device of the present invention, the deceleration and focusing lens unit is configured to form a beam spot with a diameter of less than 1 mm on the image plane at a predetermined distance from the exit.

[0012] As a preferred embodiment of the ultra-low energy monochromatic electron beam generation and transmission device of the present invention, the active edge field compensation electrode is a Herzog plate.

[0013] As a preferred embodiment of the ultra-low energy monochromatic electron beam generation and transmission device of the present invention, the electron generation unit is a Schottky field emission electron gun.

[0014] As a preferred embodiment of the ultra-low energy monochromatic electron beam generation and transmission device of the present invention, the monochromator unit is a hemispherical electrostatic deflection analyzer.

[0015] As a preferred embodiment of the ultra-low energy monochromatic electron beam generation and transmission device described in this invention, the entire transmission path of the electron beam is set within a magnetically shielded cavity.

[0016] The beneficial effects of this invention are as follows: Through the coordinated operation of the electron generation unit, injection lens unit, monochromator unit and deceleration focusing lens unit, this device can stably achieve an ultra-low energy electron beam output with continuously adjustable energy from 0 electron volts to 5 electron volts, with an energy broadening better than 90 millielectron volts, effectively improving the monochromaticity of the ultra-low energy electron beam, and significantly improving the beam transmission efficiency. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments of the present invention will be briefly described below; obviously, the drawings described below only relate to some embodiments of the present invention, and are not intended to limit the present invention.

[0018] Figure 1 A schematic diagram of electron beam generation and transmission path is shown; Figure 2 A schematic diagram of the internal structure of the injection lens unit is shown; Figure 3 A schematic diagram of the internal structure of the deceleration and focusing lens unit is shown.

[0019] In the diagram: 1. Electron generating unit; 2. Injection lens unit; 21. First electrode; 22. Second electrode; 23. Third electrode; 24. Fourth electrode; 25. Fifth electrode; 3. Monochromator unit; 4. Deceleration and focusing lens unit; 41. Sixth electrode; 42. Seventh electrode; 43. Eighth electrode; 44. Ninth electrode; 45. Tenth electrode; 5. Active edge field compensation electrode. Detailed Implementation

[0020] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0021] The terminology used in this invention is that which is currently widely used in the art in consideration of the function of the invention; however, these terms may vary according to the intent of those skilled in the art, precedent, or new technology in the art. Furthermore, specific terms may be chosen by the applicant, and in such cases, their detailed meanings will be described in the detailed description of the invention. Therefore, the terminology used in this specification should not be construed as simple names, but rather based on the meaning of the terms and the overall description of the invention.

[0022] Reference Figure 1 This embodiment provides an ultra-low energy monochromatic electron beam generation and transmission device, comprising the following components arranged sequentially along the electron beam transmission path: Electron generating unit 1, used to generate an initial electron beam; The injection lens unit 2 is used to receive the initial electron beam generated by the electron generation unit 1. Monochromator unit 3, having an inlet slit and an outlet slit, is used to filter the energy of the electron beam from the injection lens unit 2 to reduce the energy broadening of the output electron beam; The deceleration and focusing lens unit 4 is used to receive the monochromatic electron beam output from the outlet of the monochromator unit 3; The injection lens unit 2 focuses the initial electron beam and injects it into the entrance of the monochromator unit 3, while the deceleration and focusing lens unit 4 decelerates and focuses the monochromatic electron beam before outputting it.

[0023] The electron generating unit 1 generates an initial electron beam; this initial electron beam is focused by the injection lens unit 2, and by optimizing the geometry and voltage ratio, as many electrons emitted at a large angle as possible are focused onto the entrance slit of the monochromator unit 3; subsequently, the monochromator unit 3 performs energy filtering on the electron beam.

[0024] The injection lens unit 2 employs a five-element electrostatic lens design. Through the coordinated matching of multiple electrode voltages, it can effectively collect the electron beam from the divergence angle of the electron source and converge it to the entrance slit of the monochromator unit 3. This lens unit not only provides a defined object-image position relationship and optical magnification but also adjusts the electron beam energy to match the transmission energy of the monochromator unit 3, thereby improving the transmission efficiency of the electron beam. Specifically, the monochromator unit 3 utilizes the dispersion effect of the electrostatic field on electron energy by controlling the inner hemisphere electrode voltage V. 1q outer hemisphere electrode voltage V 2q The inner hemisphere radius R1 and the outer hemisphere radius R2 allow only electrons within a range of ±40 millielectron volts to pass through, thus monochromating the electron beam and reducing the energy broadening of the electron beam.

[0025] Finally, the deceleration and focusing lens unit 4 applies a gradually increasing negative potential and utilizes the effect of an electrostatic lens to converge the diverging electron beam onto the sample surface, thereby decelerating and focusing the monochromatic electron beam.

[0026] Furthermore, the deceleration and focusing lens unit 4 are proportionally linked to the electrode voltage so that the output electron beam kinetic energy is adjustable from 0 electron volts to 5 electron volts.

[0027] When the device is working, the electron energy is selected by adjusting the voltage difference of the monochromator unit 3; the final kinetic energy is set by adjusting the voltage of the end electrode of the deceleration and focusing lens unit 4.

[0028] The device in this embodiment can output an ultra-low energy monochromatic electron beam with continuously adjustable kinetic energy in the range of 0 electron volts to 5 electron volts at the sample; specifically, the energy broadening of the electron beam is better than 90 millielectron volts, and the beam current intensity is adjustable in the range of 50 nanoamps to 0.5 microamps.

[0029] Reference Figure 1As an optional embodiment, the electron generation unit 1 is a Schottky field emission electron gun.

[0030] In this embodiment, the core component of the Schottky field emission electron gun is the emitter cathode, which is made of a 0.125 mm diameter <310> oriented tungsten single crystal wire through electrochemical etching; the tip curvature radius is between 0.1 μm and 1.0 μm, with a typical value of 0.6 μm; the surface of the tip is coated with a zirconium oxide film with a thickness of 1 to 2 monolayers by vacuum deposition; this coating can effectively reduce the work function, allowing electrons to escape through the thermoelectric emission (Schottky emission) mechanism at lower electric field strength and heating temperature.

[0031] The intrinsic energy dispersion of the Schottky field-emission electron gun is approximately 0.3 electron volts, providing a high-quality, narrow-energy-dispersion initial electron beam source for subsequent monochromatic processing.

[0032] In another alternative embodiment, the electron generating unit 1 may employ a cold field emission electron gun; its emission source is an unheated, sharp tungsten single crystal needle tip, which emits electrons through quantum tunneling effect by applying an extremely high extraction electric field in an ultra-high vacuum environment; the cold field emission source can provide a smaller virtual source size and higher brightness, and its initial energy broadening can theoretically approach the Fermi distribution at room temperature; in order to maintain the cleanliness of the needle tip and the stability of the emission, such sources usually need to be equipped with an in-situ flash heating device to periodically remove adsorbents.

[0033] Furthermore, monochromator unit 3 is a hemispherical electrostatic deflection analyzer.

[0034] In this embodiment, the hemispherical deflection analyzer consists of two concentric hemispherical electrodes and is the core component for achieving sub-100 millielectronvolt energy resolution.

[0035] Specifically, the inner hemisphere radius R1 of the monochromator unit 3 is preferably 50 mm; the corresponding outer hemisphere radius R2 is preferably 70 mm; and the gap d between the two electrodes is preferably 5 mm.

[0036] The electrodes of monochromator unit 3 are made of non-magnetic stainless steel, and the inner surface is electropolished to reduce surface roughness and reduce electron scattering.

[0037] An inlet slit and an outlet slit are provided at the inlet and outlet of the monochromator unit 3, respectively; the slit width is one of the key parameters that determine the energy resolution, and in this embodiment, the slit width is preferably 0.2 to 0.5 mm; the height is 2 to 5 mm.

[0038] The rectangular slit design is based on the principle of electro-optics optimization: the spatial constraints are appropriately relaxed in the direction perpendicular to the energy dispersion plane (the slit length direction) to accommodate more electrons and increase the transmission flux; while the width is kept extremely narrow in the key direction that determines the energy resolution (the slit width direction), thereby improving the transmission efficiency several times without sacrificing the energy resolution.

[0039] When the energy is set to 10 electron volts, the inner hemisphere electrode voltage V 1q The voltage of the outer hemisphere electrode is 14V. 2q The voltage is 7.14V; active edge field compensation electrodes 5 are symmetrically integrated on the outside of the inlet and outlet of the monochromator unit 3. By applying an independently optimized voltage, focusing distortion and astigmatism caused by electric field boundary effects can be actively corrected.

[0040] To eliminate edge electric field distortion, end cap compensation electrodes are installed at both ends of the hemispherical electrode. Their shape is optimized by simulation to ensure that the electric field in the hemispherical gap is as ideal and uniform as possible.

[0041] In this embodiment, the monochromator unit 3 adopts a hemispherical electrostatic deflection structure to achieve energy monochromatic screening of the electron beam. The core is to form a radial electrostatic field by applying a voltage difference between the inner and outer hemispherical electrodes. By utilizing the difference in deflection radius of electrons of different energies in the radial electrostatic field, the screening of target energy electrons is completed. The specific working principle and parameter matching relationship are as follows: When a voltage difference ΔV is applied between the inner and outer hemispherical electrodes, a radial electrostatic field for electron deflection and screening is formed between the two electrodes, and the voltage difference ΔV is defined as follows: ; Among them, V 1q V is the voltage of the inner hemisphere electrode. 2q The voltage of the outer hemisphere electrode; ∆V is the voltage difference between the inner and outer hemisphere electrodes.

[0042] The field strength distribution of the aforementioned radial electrostatic field is directly determined by the voltage difference ΔV between the inner and outer hemispherical electrodes. After entering this electrostatic field, electrons will be deflected by the radial electric force, and their deflection trajectory is determined by their own kinetic energy and the electric field strength. Only when the kinetic energy of the incident electron and the voltage difference satisfy a preset matching relationship can the electron complete a 180° deflection along the central orbit of the hemispherical electrode and pass smoothly through the exit slit. Electrons with the remaining energy will hit the electrode wall and be filtered out. This energy matching relationship is shown in the following formula: ; Where ΔV is the voltage difference applied between the inner and outer hemispherical electrodes; K is a constant determined by the geometric dimensions (R1, R2); e is the elementary charge; and E is the kinetic energy of the electron that can deflect along the central track and pass through the exit slit.

[0043] Based on the hemispherical electrostatic field energy screening mechanism constructed above, the core performance index of monochromator unit 3, the theoretical energy resolution ΔE / E, is mainly determined by the electrode geometric factor and the slit parameters, where the geometric factor is determined by the determining constant K.

[0044] Under the structural parameters of this embodiment (R1=50mm, R2=70mm, entrance slit width=0.2mm), for electrons with an energy of 500meV that pass through the screening process, the absolute energy resolution ΔE is better than 80meV, which fully meets the design requirement of "absolute energy resolution less than 100meV" of this scheme. At the same time, the structure has a wide energy transfer function, which can effectively reduce the loss of the electron beam during the screening process and help maintain a high beam transmission efficiency, which is fully matched with the design goal of high monochromaticity and high transmission efficiency of low-energy electron beams in this scheme.

[0045] In another alternative embodiment, the monochromator unit 3 may be a cylindrical mirror analyzer; it consists of two coaxial cylindrical electrodes: the inner cylindrical electrode is usually grounded, and the outer cylindrical electrode is subjected to a negative bias voltage; electrons are emitted from a point source located on the axis of the inner cylinder, and after being double-deflected (passing through the slits on the inner cylinder wall twice), they are focused onto the detector by the electric field of the outer cylinder.

[0046] Cylindrical mirror analyzers have a larger solid angle of reception, resulting in higher transmission efficiency, but their energy resolution is usually slightly inferior to that of hemispherical analyzers. By optimizing the radius ratio, length, and slit position of the inner and outer cylinders, an energy resolution better than 120 millielectron volts can also be achieved, making them suitable for applications with extremely high beam intensity requirements.

[0047] Monochromator unit 3 adopts a high-throughput electro-optical structure design. By optimizing the entrance and exit slit sizes and compensating for edge field effects to reduce aberration effects, it achieves high-throughput and high-brightness beam transmission.

[0048] Furthermore, active edge field compensation electrodes 5 are symmetrically integrated on the outer side of the inlet and the outer side of the outlet of the monochromator unit 3.

[0049] To achieve an energy resolution better than 100 millielectron volts, the monochromator unit 3 in this embodiment has undergone key structural optimizations: a pair of active edge field compensation electrodes 5 are symmetrically integrated on the outer sides of its inlet and outlet, such as... Figure 1 As shown.

[0050] The active edge field compensation electrode 5 is a specially shaped metal ring or cavity structure, which is closely adjacent to the inlet and outlet ends of the hemispherical analyzer body, namely the inner and outer hemispherical electrodes.

[0051] The active edge field compensation electrode 5 is electrically insulated from the main analyzer electrode but mechanically fixed, forming part of the analyzer as a whole; its inner diameter is precisely aligned with the inlet / outlet channel of the main analyzer to ensure unobstructed passage of the electron beam.

[0052] The inner surface profile of the active edge field compensation electrode 5 is optimized by electrostatic field finite element simulation to generate an electric field distribution that smoothly connects with the ideal hemispherical field, thereby effectively "guiding" and "terminating" the radial electric field in the main analysis region and weakening the field distortion at the edge.

[0053] Furthermore, each active edge field compensation electrode 5 is connected to an independent, high-precision programmable voltage source.

[0054] The voltages of the inlet and outlet compensation electrodes can be adjusted independently and dynamically, without depending on the voltage ∆V of the main hemisphere electrode.

[0055] In actual debugging, the following method is used to achieve optimal compensation: First, the analyzer is set to a certain central energy, such as 500 millielectron volts; then, a monoenergetic electron beam is injected into the analyzer, or the natural energy distribution of the emission source is utilized; next, the voltages of the inlet compensation electrode and the outlet compensation electrode are finely adjusted, while monitoring the electron beam intensity or energy distribution width through the outlet slit; when the beam intensity reaches its maximum value or the energy distribution width reaches its narrowest value, it indicates that the edge field has been optimally compensated; at this time, this pair of optimal compensation voltage values ​​is recorded.

[0056] Furthermore, the active edge field compensation electrode 5 is a Herzog plate.

[0057] Specifically, the Herzog plate is a classic active edge field compensation electrode structure in the field of charged particle optics. Its core function is to correct the electric field distortion at the entrance / exit of electrostatic analyzers and electrostatic lenses. By applying a compensation potential that matches the main electric field, the equipotential surface of the edge distortion is corrected into an ideal uniform shape.

[0058] In different embodiments, the active edge field compensation electrode 5 can also be a Stir electrode. Its core function is a multi-segment split active edge field compensation electrode structure optimized for high-resolution electrostatic analyzers in the field of charged particle optics. Through the gradient potential configuration of multiple independent electrodes, it can achieve more refined edge electric field shaping than the traditional Herzog plate, further suppressing the trajectory distortion and energy dispersion of charged particles, and reducing the resolution loss caused by the edge field.

[0059] The active edge field compensation electrode 5 adopts a Steller electrode design, which enables more precise and flexible active control of the edge field. At the entrance and exit ends of the monochromator unit 3, a set of Steller electrode components is integrated. Each component consists of two coaxial ring electrode segments, which are arranged along the electron beam axis and close to the end of the main hemispherical electrode.

[0060] The electrode segments are isolated from each other and from the main electrode by insulators; the inner hole profile of each electrode segment is also optimized to ensure that the electron beam passes through without obstruction.

[0061] Reference Figures 1-2 In one embodiment provided in this application, the injection lens unit 2 is an electrostatic lens composed of multiple electrodes, and the injection lens unit 2 is used to collect the initial electron beam of the divergence angle and converge the electrons to the entrance slit of the monochromator unit 3.

[0062] In this embodiment, the injection lens unit 2 adopts a five-element electrostatic lens unit, the structure of which is as follows: Figure 2 As shown, this design, through the precise control of multiple electrodes, enables better phase space manipulation of the electron beam, ensuring efficient coupling with the downstream monochromator unit 3.

[0063] The five-element electrostatic lens has five coaxial cylindrical electrodes arranged sequentially along the electron optical axis (Z-axis); refer to the attached instruction manual. Figure 2 As shown, the cylindrical electrodes are numbered sequentially as first electrode 21, second electrode 22, third electrode 23, fourth electrode 24, and fifth electrode 25; all electrodes are precision machined from non-magnetic stainless steel and electrically isolated and fixed by alumina ceramic rings.

[0064] Specifically, the inner diameter of all electrodes is consistent and can be adjusted within the range of 20 mm to 50 mm, with a preferred value of 30 mm; the axial length of each electrode is between 10 mm and 30 mm, with a preferred value of 15 mm; the axial gap between adjacent electrodes is between 2 mm and 5 mm, with a preferred value of 3 mm; the distance from the front end face of the first electrode 21 of the lens to the virtual emission point of the electron source is between 10 mm and 30 mm; and the distance from the rear end face of the fifth electrode 25 of the lens to the entrance slit of the monochromator unit 3 is between 20 mm and 50 mm.

[0065] To achieve effective collection and precise focusing of divergent electrons, the typical operating voltages for each electrode are set as follows: (First electrode 21) V1: 0V to +10V (usually set to near ground potential, used to define the object potential). (Second electrode 22) V2: +150V to +250V (core focusing electrode, forming a strong focusing force field). (Third electrode 23) V3: +30V to +80V (Auxiliary focusing and aberration correction electrode). (Fourth electrode 24) V4: +10V to +30V (used to control the angle and shape of the output beam). (Fifth electrode 25) V5: 0V to +10V (usually set to ground potential or near ground potential, defining the image potential).

[0066] The five-element lens unit can provide a defined optical magnification, making the beam phase space distribution controllable and predictable. By configuring the voltage, the energy of the electron beam can be precisely set at the optimal inlet energy of the monochromator unit 3, thereby maximizing the electron transmission efficiency through the slit of the monochromator unit 3 and improving the overall transmission efficiency.

[0067] Compared to a simple three-electrode lens, this five-element lens design offers more adjustable degrees of freedom, enabling it to more effectively collect the initial electron beam from the electron source at the "divergence angle" and convert the initial electron beam into a beam that is highly matched with the optical characteristics of the monochromator unit. It is a key front-end component for realizing a high-current, high-transmission-efficiency ultra-low-energy electron beam unit.

[0068] Specifically, Figure 2 The three dashed lines in the figure represent the trajectories of electron beams under different initial conditions inside the injection lens unit 2: the central dashed line represents the ideal electron trajectory incident along the optical axis; the dashed lines on both sides represent electron beams with a certain divergence angle, which, after being focused by the five-element electrostatic lens, finally converge at the entrance slit of the monochromator unit 3.

[0069] Reference Figures 1-3 In some embodiments, the deceleration and focusing lens unit 4 is used to decelerate the electron beam kinetic energy from the passing energy of the monochromator unit 3 to a preset low energy. During deceleration, the deceleration and focusing lens unit 4 can maintain the convergence of the electron beam.

[0070] The deceleration and focusing lens unit 4 controls the focused beam size of the electron beam on the sample surface to less than 1 mm; specifically, it maintains the focused beam size to be less than 1 mm throughout an energy variation range of several orders of magnitude (from 10-20 electron volts to 0-5 electron volts).

[0071] Specifically, the deceleration and focusing lens unit 4 employs a precision-designed zoom transfer lens, which can achieve aberration-free energy deceleration and beam transmission in the process of reducing the electron beam kinetic energy from the passing energy of the monochromator unit 3 to the target kinetic energy of 0 electron volts to 5 electron volts.

[0072] The deceleration and focusing lens unit 4 is a precision five-electrode zoom transfer lens, such as... Figure 3 As shown, its core design goal is to reduce the kinetic energy of the electron beam from the passing energy (preferably 10-20 electron volts) of the monochromator unit 3 to a wide energy range of preset low energy (0 electron volts to 5 electron volts), dynamically maintaining optimal focusing conditions, thereby obtaining a small beam spot with precisely adjustable energy on the sample surface.

[0073] Specifically, the deceleration and focusing lens unit 4 consists of five coaxial cylindrical electrodes arranged sequentially along the electronic optical axis; all electrodes are precision machined from non-magnetic stainless steel.

[0074] Preferably, the inner diameter of the electrodes is 20 mm to 40 mm, the axial length of each electrode is 10 mm to 20 mm, the electrode wall thickness is 1 mm to 2 mm, the axial gap between adjacent electrodes is 2 mm to 5 mm, and the total length from the lens inlet to the outlet is approximately 80 mm to 120 mm. This structure ensures the axial symmetry and high repeatability of the electric field, and can aberrately reduce the kinetic energy of the electron beam from the passing energy (e.g., 10–20 electron volts) of the monochromator unit 3 to any target kinetic energy of 0–5 electron volts. During this energy change spanning several orders of magnitude, the focused size of the beam spot on the sample surface is always kept less than 1 mm, thereby generating a small, well-focused, ultra-low-energy monochromatic electron beam on the sample.

[0075] Furthermore, the deceleration and focusing lens unit 4 includes a sixth electrode 41, a seventh electrode 42, an eighth electrode 43, a ninth electrode 44, and a tenth electrode 45; and multiple electrodes work together, wherein the tenth electrode 45 directly sets the final kinetic energy of the electron, and the sixth electrode 41, the seventh electrode 42, the eighth electrode 43, and the ninth electrode 44 are linked in an optimized ratio according to the voltage change of the tenth electrode 45, thereby realizing the zoom function of the electrostatic lens.

[0076] (Sixth electrode 41) V 1t As a potential reference, it is set in the range of 1V to 10V; it defines the starting potential of the deceleration process.

[0077] (Seventh electrode 42)V 2t (Eighth electrode 43)V 3t (Ninth electrode 44)V 4t The voltages of these three intermediate electrodes are adjustable within the range of 1V to 15V; together they shape the gradient of the axial deceleration electric field and generate a radial converging force, the specific value of which is determined by the voltage of the (tenth electrode). 5t The fixed proportional relationship is used to determine the focusing length variation under different reduction ratios.

[0078] V 5t The voltage of the last electrode is continuously and precisely adjusted between 1V and 7V.

[0079] When the passing energy of monochromator unit 3 is set to 10 electron volts, and the final kinetic energy of the output electrons is required to be 5 electron volts, the voltages of the five electrodes are optimized as follows: V 1t =6.6V; V 2t =10.1V; V 3t =8.0V; V4t =3.0V; V 5t =1.6V.

[0080] This specific voltage combination ensures that the axial electric field and radial lens field experienced by electrons are always in optimal condition as they decelerate from 10 electron volts to 5 electron volts, so that the electron beam is transmitted and focused on the sample surface without aberrations.

[0081] When the passing energy of monochromator unit 3 is set to 10 electron volts, and the final kinetic energy of the output electrons is required to be 0 electron volts, the voltages of the five electrodes are optimized as follows: V 1t =-6.6V; V 2t =-4.7V; V 3t =-4.2V; V 4t =-1.8V; V 5t =3.4V.

[0082] In practice, when directly decelerating to 0 electron volts, the electrons' kinetic energy is extremely low, making them highly susceptible to failure to reach the sample surface due to contact potential differences or minute electromagnetic disturbances. To address this issue, a small positive bias voltage (e.g., +0.1V) can be applied to the sample to "extract" these near-zero kinetic energy electrons, ensuring their successful arrival at the sample surface. This bias voltage is extremely small and its impact on the accuracy of electron beam energy analysis is negligible.

[0083] The above two sets of operating parameters verify that the device can achieve effective deceleration and focusing through proportional linkage of electrode voltage throughout the entire range of 0 electron volts to 5 electron volts. For other intermediate energy values ​​in this range, those skilled in the art can determine the corresponding optimal voltage combination by linear interpolation or numerical optimization based on the voltage parameters of the above two endpoints and the control mechanism of proportional linkage of electrode voltage, thereby achieving continuously adjustable energy output throughout the entire range.

[0084] Throughout the entire energy adjustment range, the diameter of the beam spot formed on the sample surface can always be kept less than 1 mm; due to the avoidance of beam loss and energy broadening caused by defocusing or aberration, the transmission efficiency from the monochromator unit 3 outlet to the sample is high, and the final energy broadening of the electron beam can still maintain the high standard of the output of the monochromator unit 3.

[0085] And the instruction manual is attached Figure 3 The dotted line represents the approximate trajectory of electrons within the deceleration and focusing lens unit 4. Electrons enter through the inlet, are filtered within the deceleration and focusing lens unit 4, and finally converge at the outlet for emission. Specifically... Figure 3The dashed lines in the image represent the movement paths of electron beams inside the lens under different initial conditions: the central dashed line represents the ideal electron trajectory incident along the optical axis; the dashed lines on both sides represent electron beams with a certain divergence angle, which, after being decelerated and focused by the lens, eventually converge to the same focal point at the exit. These trajectories visually demonstrate how the five-electrode zoom transfer lens maintains good focusing performance of the electron beam under different deceleration ratios.

[0086] The device of this invention adopts a modular interface design. Through standardized connection interfaces, it can be compatible with various electron optical analysis units such as reflected electron spectrometers, low-energy electron diffractometers, scanning low-energy electron microscopes, and electron energy loss spectrometers, and has good versatility and expandability.

[0087] Furthermore, the entire transmission path of the electron beam is set within a magnetically shielded cavity made of a high-permeability material (such as permalloy).

[0088] In summary, this five-electrode zoom transfer lens effectively solves the inherent technical challenge of balancing strong deceleration and strong focusing in ultra-low energy electron optics. This lens can form a small, highly focused, and energy-pure ultra-low energy monochromatic electron beam on the sample surface, breaking through the performance bottleneck of traditional systems of the same type and providing a high-precision electron detection tool for atomic-scale surface analysis.

[0089] Finally, it should be noted that the methods and devices described in detail above are merely embodiments, and those skilled in the art can modify these embodiments in different ways as long as they do not depart from the scope of the present invention.

[0090] Importantly, the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A device for generating and transmitting ultra-low energy monochromatic electron beams, characterized in that: Including those arranged sequentially along the electron beam transmission path: An electron generating unit (1) is used to generate an initial electron beam; An injection lens unit (2) is used to receive the initial electron beam generated by the electron generating unit (1); The monochromator unit (3) has an inlet slit and an outlet slit for energy screening of the electron beam from the injection lens unit (2) to reduce the energy broadening of the output electron beam; The deceleration and focusing lens unit (4) is used to receive the monochromatic electron beam output from the monochromator unit (3); the electrode voltage of the deceleration and focusing lens unit (4) is proportionally linked so that the kinetic energy of the output electron beam is adjustable in the range of 0 electron volts to 5 electron volts. The injection lens unit (2) focuses the initial electron beam and injects it into the entrance of the monochromator unit (3), and the deceleration and focusing lens unit (4) decelerates and focuses the monochromatic electron beam before outputting it.

2. The ultra-low energy monochromatic electron beam generation and transmission device according to claim 1, characterized in that: The monochromator unit (3) has active edge field compensation electrodes (5) symmetrically integrated on the outer side of the inlet and the outer side of the outlet.

3. The ultra-low energy monochromatic electron beam generation and transmission device according to claim 1 or 2, characterized in that: The injection lens unit (2) is an electrostatic lens composed of multiple electrodes, and the injection lens unit (2) is used to collect an initial electron beam with a divergence angle and converge the electrons to the entrance slit of the monochromator unit (3).

4. The ultra-low energy monochromatic electron beam generation and transmission device according to claim 3, characterized in that: The deceleration and focusing lens unit (4) is used to decelerate the electron beam kinetic energy from the passing energy of the monochromator unit (3) to a preset low energy; During deceleration, the deceleration and focusing lens unit (4) can maintain the convergence of the electron beam.

5. The ultra-low energy monochromatic electron beam generation and transmission device according to claim 4, characterized in that: The deceleration and focusing lens unit (4) is configured to form a beam spot with a diameter of less than 1 mm on the image plane at a predetermined distance from the exit.

6. The ultra-low energy monochromatic electron beam generation and transmission device according to claim 2, characterized in that: The active edge field compensation electrode (5) is a Herzog plate.

7. An ultra-low energy monochromatic electron beam generation and transmission device according to claim 1, 2, 4, 5 or 6, characterized in that: The electron generation unit (1) is a Schottky field emission electron gun.

8. An ultra-low energy monochromatic electron beam generating and transmitting device according to claim 1, 2, 4, 5 or 6, characterized in that: The monochromator unit (3) is a hemispherical electrostatic deflection analyzer.

9. The ultra-low energy monochromatic electron beam generation and transmission device according to claim 8, characterized in that: The entire transmission path of the electron beam is set within a magnetically shielded cavity.

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