Hexapole corrector, its microscope tube, microscope and correction method

Abstract

The application provides a sextupole corrector for correcting spherical aberration of a transmission electron microscope objective lens, a microscope column thereof, a microscope and a correction method. The sextupole corrector, the microscope column thereof, the microscope and the correction method of the application have great improvement in control system, material selection, structure design, manufacturing process and optical path precision control. The overall structure is compact, easy to install and maintain, can be used with an existing 200kV transmission electron microscope, and high-definition stable electron microscope images are obtained.

Description

Technical Field

[0001] This invention belongs to the field of electron optics and transmission electron microscopy, specifically relating to a six-pole corrector for correcting spherical aberration of transmission electron microscope objectives, its microscope tube, microscope, and correction method. Background Technology

[0002] The resolution of an electron microscope is directly affected by the third-order spherical aberration coefficient C3. Therefore, improving resolution usually requires reducing the spherical aberration coefficient C3 or increasing the accelerating voltage. However, Scherzer's theorem states that the spherical aberration coefficient of a conventional magnetic circular lens is always positive, indicating that a single circular lens cannot eliminate spherical aberration. The advent of spherical aberration correction techniques has broken this technical limitation, enabling electron microscopes to achieve sub-angstrom level resolution. In the past two decades, some progress has been made in the research and application of spherical aberration-corrected electron microscopes. For example, Rose's 8f optical model laid the theoretical foundation for hexapole correctors, but there is still an urgent need to develop a hexapole corrector for correcting spherical aberration of transmission electron microscope objectives that is easy to install and maintain and has an optimized structural design, as well as its microscope tube, microscope, and correction method. Summary of the Invention

[0003] Therefore, the purpose of this invention is to overcome the problems of the prior art and provide a six-pole corrector for correcting the spherical aberration of transmission electron microscope objectives, which is easy to install and maintain, has an optimized structural design, and can realize multi-pole modulation of the electron beam to correct the inherent spherical aberration of the electron microscope, as well as its microscope tube, microscope, and correction method. Before describing the content of this invention, the following terms are defined as follows: The term "TEM" refers to a transmission electron microscope, which is a large-scale precision analytical instrument that uses a high-energy electron beam with an extremely short wavelength as an illumination source to penetrate ultra-thin samples and form an image, allowing observation of the microstructure of materials at high magnification.

[0004] The term "STEM" refers to Scanning Transmission Electron Microscope, an electron microscopy technique that constructs images point by point by scanning a focused, elongated electron beam (probe) across a sample and collecting the electron signals that penetrate the sample at each scanning point.

[0005] The term "UTEM" refers to Ultrafast Transmission Electron Microscope, which is an electron microscope that combines ultrafast laser technology with transmission electron microscopy imaging technology, and can simultaneously achieve femtosecond-level temporal resolution and nanometer-level spatial resolution.

[0006] The term "spherical aberration coefficient C3" refers to the third-order spherical aberration coefficient of an electromagnetic lens in an electron microscope. It is a physical quantity describing the magnitude of the third-order spherical aberration of an electromagnetic lens. Spherical aberration is an inherent and unavoidable aberration of rotationally symmetric electromagnetic lenses.

[0007] The term "pole shoe" refers to an important structure in the magnetic circuit of an electromagnetic lens. It is a high-precision metal component that constitutes the core of an electromagnetic lens. It is usually made of soft magnetic materials such as soft iron or iron-cobalt alloy and can generate a highly converging rotationally symmetrical magnetic field.

[0008] The term "alignment" refers to a mechanical two-dimensional fine-tuning mechanism, also known as alignment, which is a comprehensive mechanical and electrical adjustment technology used to ensure that the entire electro-optical system achieves optimal coaxiality.

[0009] The term "astigmator coil" refers to a device consisting of multiple sets of electromagnetic coils evenly distributed around the optical axis, installed near the pole piece of an electromagnetic lens. It is a precision electro-optical component that eliminates or reduces axial astigmatism by generating a synthetic magnetic field with adjustable intensity and direction to compensate for non-uniform magnetic fields caused by lens manufacturing defects, contamination, etc.

[0010] The term "excitation current" refers to a stable direct current flowing through the copper coil of an electromagnetic lens. It is a driving source used to magnetize the pole pieces of a lens to generate a magnetic field that focuses electrons, and by changing its size, the focal length and magnification of the lens can be adjusted.

[0011] The term "XY plane" refers to a two-dimensional horizontal coordinate plane perpendicular to the optical axis of the electron beam in a transmission electron microscope. It is a reference plane used to describe the range of two-dimensional movement of a sample in the horizontal direction. The operator uses movement on this plane to locate and select the area of ​​the sample of interest for observation.

[0012] The term "Zemlin diffraction" is a method used to measure and characterize various geometric aberrations (especially spherical aberration and higher-order aberrations) of electromagnetic lenses.

[0013] The term "OA" refers to the optical axis, which is the axis of symmetry of an optical system. It is the straight line where the center line of the beam or the curvature centers of the surfaces in the system are collinear. In anisotropic gemstones, the special direction in which birefringence does not occur is also called the optical axis. In the description of this invention, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0014] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0015] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. To achieve the above objectives, the present invention provides the following technical solution: A first aspect of the present invention provides a hexapole corrector for correcting spherical aberration of electron microscope objectives, the hexapole corrector comprising the following component modules: Six-pole field system module, Transmission lens and adjustment lens module, Vacuum regulation module, Deflection and astigmatism module, and Circuit control module; The hexapole field system module comprises multiple sub-units arranged vertically along the optical axis, each sub-unit consisting of six pole shoes and a coil. Preferably, in the hexapolar corrector according to the first aspect of the present invention, the hexapolar field system module includes: The number of groups in which the sub-units are evenly arranged vertically along the optical axis is 2-10, preferably 2-6, more preferably 2-4, and most preferably 2. Each of the aforementioned subunits is formed by inserting six of the aforementioned pole shoes into six corresponding bushings, and each bushing is wound with the aforementioned coil; and / or The material of the coil is selected from one or more of the following: gold, aluminum, superconducting materials, copper, preferably selected from one or more of the following: gold, aluminum, copper, and most preferably copper. More preferably, in the hexa-pole corrector according to the first aspect of the invention, in the sub-unit: The inner diameter of the pole shoe is 5-15mm, preferably 6-10mm, and more preferably 6-9mm; The length of the pole shoe is 15-35mm, preferably 20-30mm, and more preferably 22-25mm; The coil has 200-3600 turns, preferably 300-2000 turns, and more preferably 500-1000 turns; and / or The wire diameter of the coil is 0.1-0.8 mm, preferably 0.2-0.6 mm, and more preferably 0.3-0.4 mm. Preferably, in the hexa-pole corrector according to the first aspect of the invention, wherein: The transmission lens and adjustment lens module achieve focusing and centering adjustment of the electron beam through the generated rotationally symmetric magnetic field. The operating current range is 0-5A, preferably 0-3.5A, and more preferably 0-1.5A. Preferably, in the hexa-pole corrector according to the first aspect of the invention, wherein: The vacuum regulation module includes a vacuum tube, an upper sealing assembly, and a lower sealing assembly; The circuit control module includes a digital control circuit and a constant current power supply; and / or The deflection and astigmatism module includes a deflection system and an astigmatism correction system. More preferably, in the hexapolar corrector according to the first aspect of the invention, wherein: The deflection system includes an upper deflection coil group and a lower deflection coil group, each group consisting of two rectangular coils connected in opposite directions, achieving precise deflection of the electron beam in a plane; and / or The astigmatism correction system includes an astigmatism correction coil; More preferably, the astigmatism correction coil uses an octet coil to generate an octet field, and each astigmatism coil in the octet coil is independent and evenly distributed in the astigmatism correction system. More preferably, in the hexapolar corrector according to the first aspect of the invention, wherein: In the deflection system, the rectangular coil has 40-200 turns, preferably 50-100 turns, and most preferably 80 turns; the wire diameter of the rectangular coil is 0.05-0.3 mm, preferably 0.1-0.2 mm, and most preferably 0.2 mm; and / or In the astigmatism correction system, the astigmatism coil has 100-800 turns, preferably 300-600 turns, and most preferably 500 turns; the wire diameter of the astigmatism coil is 0.05-1.0 mm, preferably 0.1-0.5 mm, and most preferably 0.4 mm. A second aspect of the present invention provides a microscope tube comprising a hexapolar corrector according to a first aspect of the present invention; Preferably, in the microscope tube, the hexapole corrector is installed between the objective lens and the projection system of the microscope tube, and the optical axis of the hexapole corrector coincides with the principal optical axis of the objective lens. A third aspect of the present invention provides a transmission electron microscope comprising a microscope tube according to a second aspect of the present invention; Preferably, the transmission electron microscope is an ultrafast transmission electron microscope and / or a scanning transmission electron microscope.

[0016] A fourth aspect of the present invention provides a method for correcting spherical aberration of a transmission electron microscope objective, the method comprising: using a hexapolar corrector according to a first aspect of the present invention; Preferably, the method includes the following steps: 1) Fix the hexapole corrector into the tube of the transmission electron microscope; 2) Connect the vacuum regulation module; 3) Connect the cable to the circuit control module and turn on the power to each module; 4) Axis alignment adjustment to ensure electron beam alignment; 5) Adjust the six-pole field excitation current and the transmission lens current to minimize the third-order spherical aberration coefficient C3; 6) Verify the spherical aberration correction effect through imaging. According to a preferred embodiment of the present invention, a hexapole corrector for use in a transmission electron microscope or scanning transmission electron microscope is provided, comprising five parts: a hexapole field system module, a transfer lens and adjustment lens module, a vacuum and mechanical alignment adjustment module, a deflection and astigmatism module, and a circuit control module. The hexapole field system module includes a hexapole unit housing, a hexapole shoe, a coil, a coil support, a hexapole shoe bushing, a hexapole tightening nut, a positioning pin, a hexapole shoe adjusting pad, and a hexapole tightening nut adjusting pad. The transfer lens and adjustment lens module includes a microscope tube housing, a transfer lens upper housing, a middle housing and a lower housing, an adjustment lens upper housing and a lower housing, a water-cooled baffle and cover plate, a coil, a water-cooled chamber assembly, and a two-dimensional mechanical alignment device. The vacuum adjustment module includes a vacuum tube, an upper sealing assembly, and a lower sealing assembly. The circuit control module includes a digital control circuit and a high-stability constant current power supply. The deflection and astigmatism module includes a deflection system and an astigmatism correction system. The deflection system includes an upper deflection coil group and a lower deflection coil group, each consisting of two rectangular coils connected in opposite directions to achieve precise deflection of the electron beam in the XY plane. The astigmatism correction system includes astigmatism correction coils. This design uses an octet coil to generate an octet field. Each astigmatism coil is independent and evenly distributed along the circumference to finely compensate for the remaining astigmatism, including asymmetric aberrations caused by manufacturing errors, centering deviations, contamination, etc. According to the aforementioned preferred embodiment of the hexapole corrector, more preferably, the hexapole field system module comprises two sets of hexapole field sub-units arranged vertically along the optical axis. Each set of hexapole field sub-units consists of six independent pole shoes arranged at equal angles of 60° around the circumference. Each bushing is wound with a copper coil, and the pole shoes are inserted into the bushings to form a sub-unit. All sub-units are independent structures, facilitating disassembly, assembly, and maintenance. The entire hexapole field sub-unit is installed with dedicated tooling, which significantly improves assembly accuracy and meets operational requirements. Those skilled in the art should understand that the hexapole field structure of this invention is not limited to sixfold symmetry and is also applicable to multi-pole field systems such as 12-pole or 24-pole systems. According to the aforementioned preferred embodiment of the six-pole calibrator, more preferably, the inner diameter of the pole shoe is 6-10mm, preferably 9mm, the pole shoe length is 25-35mm, preferably 25mm; the number of coil turns is 500-3600 turns, preferably 1000 turns, the wire diameter is 0.2-0.6mm, preferably 0.4mm, and the operating current range is 0-800mA, preferably 0-500mA. According to the aforementioned preferred embodiment of the hexapolar corrector, more preferably, the operating current range of the transmission lens and the adjustment lens is 0-1.5A, and the electron beam is focused and centered by the generated rotationally symmetric magnetic field. According to the aforementioned preferred embodiment of the six-electrode corrector, more preferably, the stability of the six-electrode field current source output by the circuit control module is better than 1-2 ppm, and the stability of the transmission lens current source is better than 5-10 ppm; the corrector has a two-layer mechanical two-dimensional centering mechanism and is equipped with an independent water cooling system to ensure the working stability of the entire spherical aberration corrector. According to the aforementioned preferred embodiment of the hexapole corrector, more preferably, the deflection and astigmatism module includes a deflection system and an astigmatism correction system; the deflection system includes an upper deflection coil group and a lower deflection coil group, each group consisting of two rectangular coils connected in series in opposite directions, with 40-200 turns, preferably 80 turns, a coil wire diameter of 0.1-0.2mm, preferably 0.2mm, a series resistance of approximately 4Ω, and an operating current range of 0-150mA, adjustable in both directions, used to achieve precise deflection of the electron beam in the XY plane and its alignment and centering in the optical path; the astigmatism correction system includes 8 independent astigmatism correction coils, each with 100-500 turns, preferably 500 turns, a coil wire diameter of 0.1-0.4mm, preferably 0.4mm, and an operating current range of 0-500mA, used to eliminate additional aberrations generated by the hexapole corrector. According to another preferred embodiment of the present invention, the present invention provides a method for using the hexapole corrector described in the aforementioned preferred embodiment, comprising the following steps: Step 1, fixing the hexapole corrector to the electron microscope barrel via upper and lower connecting flanges, and achieving vacuum sealing through the sealing rings on the flanges; Step 2, connecting the vacuum system and water cooling pipeline; Step 3, connecting the cable to the circuit control module and turning on the power to each module; Step 4, performing alignment adjustment to ensure electron beam alignment; Step 5, acquiring Zemlin diffraction patterns using an amorphous carbon film as a sample and calculating aberration coefficients; Step 6, iteratively adjusting the hexapole field excitation current and the transmission lens current to minimize the third-order spherical aberration coefficient C3; Step 7, verifying the spherical aberration correction effect through high-resolution imaging. According to another preferred embodiment of the present invention, a hexapolar corrector comprising the following five modules: a hexapolar field system module, a transfer lens and adjustment lens module, a vacuum adjustment module, a deflection and astigmatism module, and a circuit control module. The deflection and astigmatism module is responsible for the precise deflection of the electron beam and the elimination of second-order astigmatism. The hexapolar field system module, as the core component, contains two sets of sub-units arranged vertically along the optical axis, each set consisting of six pole shoes and corresponding copper coils. The transfer lens and adjustment lens module includes an upper transfer lens, a lower transfer lens, and an adjustment lens. The circuit control module, through a digital control circuit and a constant current power supply, provides highly stable current to each module. According to the aforementioned preferred embodiment of the hexapole corrector, further preferably, the key parameters of each module are as follows: the inner diameter of the pole shoe of the hexapole field subunit is 6-10mm, the pole shoe length is 25-35mm, the number of coil turns is 500-3600 turns, and the operating current is 0-800mA. The operating current range of the transfer lens and the adjustment lens is 0-1.5A, and the electron beam focusing and centering are achieved through a rotationally symmetric magnetic field. Regarding the circuit control module, the stability of the hexapole field current source is better than 1-2ppm, and the current source of the transfer lens is better than 5-10ppm. Even more preferably, the deflection and astigmatism module is further divided into a deflection system and an astigmatism correction system. The deflection system includes an upper deflection coil group and a lower deflection coil group, each group consisting of two rectangular coils connected in opposite series, responsible for accurately deflecting the electron beam in the XY plane. The astigmatism correction system adopts an octet coil configuration, eliminating second-order astigmatism through the astigmatism correction coils. According to another preferred embodiment of the present invention, the present invention provides a method for using a hexapole corrector according to yet another preferred embodiment, comprising the following steps: Step 1, fixing the hexapole corrector to the electron microscope barrel via upper and lower connecting flanges and achieving vacuum sealing; Step 2, connecting the vacuum system and water cooling pipeline; Step 3, connecting the cable to the circuit control module and turning on the power of each module; Step 4, performing alignment adjustment to ensure electron beam centering; Step 5, acquiring Zemlin diffraction charts using an amorphous carbon film as the sample and calculating aberration coefficients; Step 6, iteratively adjusting the hexapole field excitation current and the transmission lens current to minimize the third-order spherical aberration coefficient C3; Step 7, verifying the correction effect. According to a preferred embodiment of the present invention, a six-pole corrector comprising the following five modules: a six-pole system module, a transfer lens and adjustment lens module, a vacuum adjustment module, a deflection and astigmatism module, and a circuit control module. The six-pole system module comprises two sets of six-pole sub-units arranged vertically along the optical axis, each set consisting of six pole shoes and copper coils. The transfer lens and adjustment lens module comprises an upper transfer lens group, a lower transfer lens group, and an adjustment lens, forming the telescope imaging optical path. In the deflection and astigmatism module, the deflection coil modulates the optical path position of the upper and lower six-pole units, while the astigmatism coil eliminates additional astigmatism introduced by the corrector. The circuit control module supplies power to each module via a digital control circuit and a high-stability constant current power supply. Compared with the prior art, the technical solution of the present invention may have the following beneficial effects, but is not limited to: This invention represents a significant improvement in control systems, material selection, structural design, manufacturing processes, and precise optical path control. The overall structure is compact, easy to install and maintain, and can be used in conjunction with existing 200kV transmission electron microscopes to obtain high-definition and stable electron microscopic images. Attached Figure Description

[0017] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the overall module composition structure of the six-pole corrector as exemplified in Embodiment 1 of the present invention.

[0018] Figure 2 This is a schematic cross-sectional view of the six-pole field sub-unit structure in the six-pole corrector exemplified in Embodiment 1 of the present invention.

[0019] Figure 3 This is a schematic diagram of the deflection and astigmatism correction module in the hexapolar corrector exemplified in Embodiment 1 of the present invention.

[0020] Figure 4 This is a schematic diagram of the overall assembly structure of the TEM tube as exemplified in Embodiment 2 of the present invention, and a schematic diagram showing the positional relationship between the hexapolar corrector and the other components as exemplified in Embodiment 1 of the present invention.

[0021] Figure 5 The method described in Embodiment 3 of the present invention uses the hexapolar corrector described in Embodiment 1 of the present invention to obtain the imaging test result image of the gold standard sample under an accelerating voltage of 80kV. Explanation of reference numerals in the attached figures: 1. First transfer lens group; 2. Second transfer lens group; 3. Adjustment lens; 4. First transfer lens deflection coil; 5. Deflection and astigmatism adjustment module; 6. First hexapole field; 7. Second transfer lens deflection coil; 8. Second hexapole field deflection coil; 9. Second hexapole field; 10. Imaging deflection coil; 11. Hexapole corrector; 12. Circuit control module; 13. Imaging system; 14. Illumination system; 15. Transmission electron microscope; 16. Fastening screw; 17. Hexapole field housing; 18. Hexapole coil; 19. Bushing; 20. Hexapole pole shoe; 21. Upper deflection coil; 22. Astigmatism correction coil; 23. Lower deflection coil. Those skilled in the art should understand that the above figures are for illustrating preferred embodiments of the present invention only and are not intended to limit the invention. The dimensions and shapes of the components in the figures do not fully reflect the true proportions of the corrector and are only intended to illustrate the principle. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, it should be understood that these embodiments are merely for more detailed and specific explanation and should not be construed as limiting the present invention in any way. This section provides a general description of the materials and testing methods used in the experiments of this invention. While many of the materials and methods of operation used to achieve the objectives of this invention are well known in the art, the invention is still described in as much detail as possible herein. It will be apparent to those skilled in the art that, unless otherwise stated in the context, the materials and methods of operation used in this invention are well known in the art. Example 1

[0023] This embodiment is an exemplary description of the hexapole corrector for correcting spherical aberration of transmission electron microscope objectives according to the present invention. Figure 1 The diagram shown illustrates the structural block diagram of the six-pole corrector in operation according to this embodiment. The six-pole corrector of this embodiment consists of five main modules: a six-pole field system module, a transfer lens and adjustment lens module, a vacuum and mechanical alignment adjustment module, a deflection and astigmatism module, and a circuit control module. In operation, the electron beam is incident along the optical axis (OA). After being focused by the objective lens, the first transfer lens group 1 images the back focal plane of the objective lens 1:1 onto the center of the first hexapole field 6. As the electron beam passes through this central region, it is subjected to the hexapole field, resulting in second-order deflection. Subsequently, the second transfer lens group 2 images the first hexapole field onto the second hexapole field 9 without rotation and at the same magnification. The two hexapole fields (6, 9) are arranged along the optical axis and form an optical transformation path through the transfer lens system, synthesizing an equivalent third-order spherical aberration term equal in magnitude but opposite in direction to the objective lens spherical aberration, thus compensating for and correcting the objective lens spherical aberration. A deflection and astigmatism adjustment module 5 is placed before the first hexapole field 6 for coaxial deflection of the electron beam and correction of residual astigmatism. Finally, the electron beam is adapted to the projection imaging system via the adjustment lens 3. Each lens system is equipped with independent deflection coils 4, 7, 8, and 10, and the circuit control module 12 provides highly stable current to each component for precise optical path modulation. like Figure 2 As shown, in this embodiment of the hexapole corrector, the hexapole field subunit is composed of hexapole pole shoes 20 and hexapole coils 18 arranged at equal angles along the circumference of the hexapole field housing 17. The hexapole coils 18 are wound on the hexapole pole shoes 20 and positioned and locked by bushings 19 and fastening screws 16. The six pole shoes are evenly arranged at 60° intervals, with the ends of each pole shoe pointing towards the center, and adjacent pole shoes are separated by coil slots. The hexapole field generates a sixfold symmetrical magnetic field distribution through the superposition of magnetic fields between three sets of opposite pole shoes.

[0024] In this embodiment of the six-electrode corrector, the vacuum adjustment module includes a vacuum tube, an upper sealing assembly, and a lower sealing assembly. The vacuum tube is connected to an external vacuum pump unit. The upper and lower sealing assemblies are located at the upper and lower connecting flanges between the corrector and the electron microscope barrel, respectively, and high-vacuum sealing is achieved using O-rings. The design of the sealing assembly ensures that the vacuum level inside the corrector is better than the vacuum requirement of the electron microscope barrel, avoiding the impact of vacuum leakage on imaging quality. The individual vacuum test of this corrector system is much less than 10. -3 Pa, meets the work requirements. In this embodiment of the hexapole corrector, both the transfer lens group (1 and 2) and the adjustment lens group 3 are equipped with cooling channels to control temperature rise, and the operating current range is 0-1.5A. A two-dimensional mechanical centering adjustment device is provided externally to the lenses to ensure that the optical axis coincides with the system's main optical axis. The transfer lens group (1 and 2) is integrated within the entire hexapole field module, consisting of an upper transfer lens and a lower transfer lens, positioned vertically between the correction module and fixed by a long bolt, forming a complete system. This correction scheme is not limited to hexapole coils and is also applicable to 12-pole or 24-pole coil configurations. Test results of the transfer lens group have confirmed its normal function, and the rationality of its design has been verified. like Figure 3 As shown, the deflection and astigmatism module in the hexapole corrector of this embodiment includes a deflection system and an astigmatism correction system, comprising an upper deflection coil 21, a lower deflection coil 23, and an astigmatism correction coil 22. The deflection and astigmatism module is positioned before the first hexapole field for precise deflection and astigmatism correction of the electron beam. The astigmatism correction system operates based on the principle of multipole field superposition. By adjusting the excitation current of the coils, an adjustable compensating magnetic field is generated in the XY plane to eliminate second-order astigmatism introduced by mechanical errors or magnetic field asymmetry in the hexapole correction system, thereby improving the accuracy of spherical aberration correction. The deflection and astigmatism module is electrically connected to the circuit control module, which provides a highly stable constant current power supply. The operating current of each deflection coil and astigmatism correction coil is independently adjusted by the digital control circuit to achieve precise current control and real-time feedback. The deflection and astigmatism module enables the hexapole corrector to finely adjust the electron beam path during spherical aberration correction, reducing the difficulty of alignment and thus improving correction efficiency and imaging quality.

[0025] The deflection system 4 employs a rectangular coil dual-deflection design, comprising an upper deflection coil group and a lower deflection coil group. Each deflection coil group consists of two opposing rectangular coils connected in series, with a single coil resistance of approximately 2Ω and a total resistance of approximately 4Ω after series connection. The coils are wound with 0.2mm diameter enameled wire, and the operating current range is 0~150mA, with adjustable forward and reverse current. The upper and lower deflection coil groups are independently controlled, working together to achieve precise deflection of the electron beam in the XY plane, used for alignment and electron beam centering. The astigmatism correction system contains eight independent astigmatism correction coils, each with 100-500 turns, a wire diameter of 0.1-0.4mm, and an operating current range of 0~500mA, used to eliminate additional aberrations generated by the hexapole corrector. The astigmatism correction coils are configured with eight poles, evenly distributed along the circumference. By independently adjusting the current of each coil, an adjustable eight-pole compensation field is generated, thereby accurately eliminating asymmetric aberrations caused by mechanical assembly errors, magnetic field asymmetry, or contamination. Example 2

[0026] This embodiment is an exemplary illustration of a microscope tube (specifically a TEM tube) that includes the six-pole corrector of the example in Embodiment 1. Figure 4 This is a schematic diagram of the overall assembly structure of the TEM tube as exemplified in Embodiment 2 of the present invention, and a schematic diagram showing the positional relationship between the hexapolar corrector and the other components as exemplified in Embodiment 1 of the present invention.

[0027] Specifically, in this embodiment, the hexapole corrector is installed in the TEM tube as follows: Figure 1 As shown, the hexapole corrector 11 is installed between the objective lens and the projection system in the transmission electron microscope tube. Along the optical axis (OA), from top to bottom, it comprises: an imaging system, a corrector module, a projection system, and a detector. The corrector module is fixed to the electron microscope tube via upper and lower connecting flanges. During installation, it must be ensured that the optical axis of the corrector coincides with the principal optical axis of the electron microscope, with a deviation not exceeding 10 μm. The corrected electron beam is transmitted to the detector for imaging via the projection system.

[0028] In this diagram, 15 represents a transmission electron microscope, specifically a JEOL-2000EX model, with the dotted line with an arrowhead indicating the electron beam path. 13 represents the imaging system, consisting of an electron gun, condenser lens, and objective lens. 14 represents the illumination system, composed of an intermediate mirror, projection mirror, and fluorescent screen. 12 represents the circuit control module, which uses a digital control circuit and a highly stable DC power supply to independently adjust the current of each coil. In this embodiment, a OneView camera manufactured by Gatan Inc. is used for image acquisition. Example 3

[0029] This embodiment is an example of a method for correcting spherical aberration of a transmission electron microscope objective lens using the six-electrode corrector exemplified in Embodiment 1 of the present invention, as exemplified in Embodiment 3 of the present invention. The method includes the following steps: Step 1: Fix the hexapole corrector to the electron microscope barrel through upper and lower connecting flanges, and achieve vacuum sealing through the sealing ring on the flange; Step 2: Connect the vacuum system and water cooling pipeline; Step 3: Connect the cable to the circuit control module and turn on the power of each module; Step 4: Perform coaxial adjustment to ensure electron beam alignment; Step 5: Collect Zemlin diffraction patterns using an amorphous carbon film as the sample and calculate the aberration coefficients; Step 6: Iteratively adjust the hexapole field excitation current and the transfer lens current to minimize the third-order spherical aberration coefficient C3; Step 7: Verify the spherical aberration correction effect through high-resolution imaging.

[0030] Image of the imaging test results of the gold standard sample under an accelerating voltage of 80 kV. This is yet another exemplary illustration of the Si-based GaN heterostructure and its fabrication method according to the present invention.

[0031] like Figure 5 As shown, the imaging test results of the hexapolar corrector of this invention demonstrate that, when used in conjunction with a 200kV transmission electron microscope, it yielded high-resolution electron microscopic images, verifying the feasibility and reliability of the corrector design. Further optimization of the coil parameters and control system can be implemented to obtain even better image quality. While the above description shows some of the technical solutions and effects of the embodiments, those skilled in the art should understand that, based on the concept of the present invention, other technical solutions of the present invention not specifically shown in the embodiments can also achieve technical effects equivalent to those of the embodiments. Although the invention has been described to a certain extent, it is apparent that appropriate variations can be made to the various conditions without departing from the spirit and scope of the invention. It is understood that the invention is not limited to the described embodiments, but falls within the scope of the claims, which include equivalent substitutions for each of the elements.

Claims

1. A six-pole corrector for correcting spherical aberration of electron microscope objectives, characterized in that, The hexapolar corrector includes the following component modules: Six-pole field system module, Transmission lens and adjustment lens module, Vacuum regulation module, Deflection and astigmatism module, and Circuit control module; The hexapole field system module comprises multiple sub-units arranged vertically along the optical axis, each sub-unit consisting of six pole shoes and a coil.

2. The six-pole corrector according to claim 1, characterized in that, In the hexapole field system module: The number of groups in which the sub-units are evenly arranged vertically along the optical axis is 2-10, preferably 2-6, more preferably 2-4, and most preferably 2. Each of the aforementioned subunits is formed by inserting six of the aforementioned pole shoes into six corresponding bushings, and each bushing is wound with the aforementioned coil; and / or The material of the coil is selected from one or more of the following: gold, aluminum, superconducting materials, copper, preferably selected from one or more of the following: gold, aluminum, copper, and most preferably copper.

3. The six-pole corrector according to claim 2, characterized in that, In the subunit: The inner diameter of the pole shoe is 5-15mm, preferably 6-10mm, and more preferably 6-9mm; The length of the pole shoe is 15-35mm, preferably 20-30mm, and more preferably 22-25mm; The coil has 200-3600 turns, preferably 300-2000 turns, and more preferably 500-1000 turns; and / or The wire diameter of the coil is 0.1-0.8 mm, preferably 0.2-0.6 mm, and more preferably 0.3-0.4 mm.

4. The six-pole corrector according to any one of claims 1-3, characterized in that: The transmission lens and adjustment lens module achieve focusing and centering adjustment of the electron beam through the generated rotationally symmetric magnetic field. The operating current range is 0-5A, preferably 0-3.5A, and more preferably 0-1.5A.

5. The six-pole corrector according to any one of claims 1-4, characterized in that: The vacuum regulation module includes a vacuum tube, an upper sealing assembly, and a lower sealing assembly; The circuit control module includes a digital control circuit and a constant current power supply; and / or The deflection and astigmatism module includes a deflection system and an astigmatism correction system.

6. The six-pole corrector according to claim 5, characterized in that: The deflection system includes an upper deflection coil group and a lower deflection coil group, each group consisting of two rectangular coils connected in opposite directions, achieving precise deflection of the electron beam in a plane; and / or The astigmatism correction system includes an astigmatism correction coil; Preferably, the astigmatism correction coil uses an octagonal coil to generate an octagonal field, and each astigmatism coil in the octagonal coil is independent and evenly distributed in the astigmatism correction system.

7. The six-pole corrector according to claim 6, characterized in that: In the deflection system, the rectangular coil has 40-200 turns, preferably 50-100 turns, and most preferably 80 turns; the wire diameter of the rectangular coil is 0.05-0.3 mm, preferably 0.1-0.2 mm, and most preferably 0.2 mm; and / or In the astigmatism correction system, the astigmatism coil has 100-800 turns, preferably 300-600 turns, and most preferably 500 turns; the wire diameter of the astigmatism coil is 0.05-1.0 mm, preferably 0.1-0.5 mm, and most preferably 0.4 mm.

8. A microscope tube comprising a hexapolar corrector according to any one of claims 1-7; Preferably, in the microscope tube, the hexapole corrector is installed between the objective lens and the projection system of the microscope tube, and the optical axis of the hexapole corrector coincides with the principal optical axis of the objective lens.

9. A transmission electron microscope, characterized in that, The transmission electron microscope comprises the microscope tube according to claim 8; Preferably, the transmission electron microscope is an ultrafast transmission electron microscope and / or a scanning transmission electron microscope.

10. A method for correcting spherical aberration of a transmission electron microscope objective, characterized in that, The method includes: using a six-pole corrector according to any one of claims 1-7; Preferably, the method includes the following steps: 1) Fix the hexapole corrector into the tube of the transmission electron microscope; 2) Connect the vacuum regulation module; 3) Connect the cable to the circuit control module and turn on the power to each module; 4) Axis alignment adjustment to ensure electron beam alignment; 5) Adjust the six-pole field excitation current and the transmission lens current to minimize the third-order spherical aberration coefficient C3; 6) Verify the spherical aberration correction effect through imaging.

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