Multi-field Coupled Transmission Electron Microscopy In-situ Sample Holder and Its Two-Way Precise Temperature and Electromagnetic Field Control System

Abstract

This invention discloses an in-situ sample holder for multi-field coupled transmission electron microscopy and its bidirectional precise temperature and electromagnetic field control system, belonging to the field of transmission electron microscopy. The sample holder of this invention includes a stage, a miniature U-shaped electromagnet and a PCB circuit board disposed within the stage, a temperature-conducting plate and a liquid nitrogen circulation pipe disposed at the rear end of the stage, and a four-electrode MEMS thermoelectric chip disposed on the stage. This invention achieves dual control of heating and electric field through the MEMS thermoelectric chip, and, combined with a liquid nitrogen cooling system, achieves bidirectional temperature regulation of the sample. Simultaneously, the sample holder also integrates a miniature U-shaped electromagnet to apply a controllable parallel magnetic field. The entire system can perform multi-field coupled experiments under extreme conditions, such as dynamic studies of electricity, magnetism, and phase transitions.

Description

Technical Field

[0001] This invention belongs to the field of in-situ experimental technology of transmission electron microscopy (TEM), and particularly relates to a multi-field coupled transmission electron microscope in-situ sample holder and its bidirectional precise temperature and electromagnetic field control system method. Background Technology

[0002] Transmission electron microscopy (TEM) is an important tool for studying the microstructure and properties of materials, providing high-resolution images and rich chemical and structural information. In many research fields, such as materials science, physics, and nanotechnology, TEM technology is widely used in in-situ experiments to study the dynamic behavior of samples under different physical fields (such as structural changes under heating, cooling, stress, electric fields, magnetic fields, etc.).

[0003] Currently, most TEM sample rod technologies on the market and in the literature mainly include heated sample rods, liquid nitrogen cooled sample rods, and electric and magnetic field controlled sample rods. These technologies can apply one or two physical fields (such as electric field and heating, magnetic field and cooling, etc.). However, achieving multi-field coupled control, especially the technology of simultaneously and accurately controlling electric field, magnetic field, heating and cooling, still faces many challenges. The following are some of the main problems in the existing technologies:

[0004] 1. High Challenges in Multi-Field Coupling: Existing TEM sample holder technologies mainly focus on single-field or dual-field control. For example, common heating sample holders and electric field sample holders can independently achieve heating or electric field application, but when electric, magnetic, and temperature fields interact, inter-field interference problems arise. Especially when the sample is simultaneously in a high-temperature, electric, and magnetic field environment, electromagnetic interference, thermal runaway, and other phenomena severely affect experimental accuracy.

[0005] 2. Limited Temperature Control Range: Most heating and cooling systems have relatively narrow temperature control ranges, especially bidirectional temperature control (heating and cooling), which has low precision and unstable temperature gradient control. For example, existing liquid nitrogen-cooled sample rods only support low-temperature cooling and lack corresponding heating functions; while the cooling function of heated sample rods often lacks the ability to rapidly change temperatures, posing a challenge to dynamic experiments (such as phase transitions and microstructure evolution).

[0006] 3. Inaccurate Coupling Control of Electromagnetic and Temperature Fields: Even with the current technology achieving joint control of multiple physical fields (such as electric field and heating, magnetic field and cooling), electromagnetic and thermal interference remain insurmountable problems. For example, during heating or cooling, the magnetic field of a magnetic sample rod often becomes unstable due to heat transfer, affecting the sample's microstructure or electromagnetic response. The influence of the electric field on the magnetic field is mainly manifested in the generation of an additional magnetic field through electromagnetic induction under high-intensity electric fields, and the distortion of the magnetic field caused by electric field-induced current, thus disrupting the uniformity and stability of the magnetic field. Furthermore, changes in the electric field can also induce charge accumulation effects, interfering with the distribution of the magnetic field, especially in dynamic electric fields or micro / nano-scale experiments.

[0007] 4. Insufficient Micro-area Control and Precision: In existing TEM in-situ sample holders, precisely controlling the temperature, electric field, and magnetic field of the sample micro-area remains a technical challenge. Although MEMS chips have been used for micro-area heating control in recent years, how to achieve the combined application of MEMS chips with electric and magnetic fields, and how to modulate the effects of different physical fields at the micrometer or nanometer scale, are still gaps in current technology.

[0008] In summary, existing TEM sample holder techniques have significant limitations in multi-field coupling control, temperature range and accuracy, and micro-field application, especially lacking effective solutions for the coordinated control of electric fields, magnetic fields, heating, and cooling. Therefore, there is an urgent need for a novel sample holder capable of achieving multi-field coupling, precise temperature control, and micro-area manipulation in TEM experiments to meet the experimental needs of materials science and other cutting-edge research. Summary of the Invention

[0009] To overcome the shortcomings of existing technologies, this invention provides a multi-field coupled transmission electron microscope (TEM) in-situ sample holder and its bidirectional precise temperature and electromagnetic field control system method. This invention aims to achieve precise coordinated control of multiple physical fields (electric field, magnetic field, heating, and cooling) in in-situ transmission electron microscopy (TEM) experiments, while maintaining high precision, stability, and repeatability under multi-field coupling conditions.

[0010] On one hand, the present invention provides an in-situ sample rod for a multi-field coupled transmission electron microscope, comprising a sample rod head, a sample rod body, and a handle; the sample rod head and the handle are respectively disposed at both ends of the sample rod body;

[0011] The sample rod head includes a stage, a four-electrode MEMS thermoelectric chip located within the stage, a U-shaped electromagnet, a PCB circuit board, a thermoelectric shield for enclosing the U-shaped electromagnet, and a temperature-conducting plate located at the rear end of the stage; wherein the stage is provided with a MEMS thermoelectric chip positioning groove and a four-electrode tungsten needle, the MEMS thermoelectric chip positioning groove being used for positioning the MEMS thermoelectric chip.

[0012] The thermoelectric shield is U-shaped, and the U-shaped electromagnet is completely placed inside the thermoelectric shield. The two ends of the U-shaped structure of the thermoelectric shield are sealed. The shell wall of the thermoelectric shield (23) is made of multi-layer composite thermal insulation and electrical insulation material, which includes, from the inside to the outside, a polyimide inner layer, a ceramic fiber felt middle layer, an alumina ceramic outer layer and a surface treatment layer. The two arms of the U-shaped electromagnet are respectively placed on both sides of the stage, which can apply a parallel magnetic field to the sample.

[0013] An external control interface is provided at the end of the handle, and the U-shaped electromagnet and the four-electrode tungsten needle are electrically connected to the external control interface through a PCB circuit board.

[0014] The handle contains a cooling reservoir, which includes an inner liquid nitrogen reservoir and an outer shell, with a vacuum interlayer in between to insulate against heat transfer.

[0015] The liquid nitrogen in the cooling jug circulates through a liquid nitrogen circulation tube to the temperature-conducting plate, where it contacts the chip to lower the temperature. The liquid nitrogen circulation tube is equipped with an inflow micro flow controller and an outflow micro flow controller for dual control of the inflow and outflow of liquid nitrogen. The four-electrode MEMS thermoelectric chip has a heating function and works in conjunction with the temperature-conducting plate to precisely apply the required temperature field through bidirectional temperature control. The handle is equipped with a liquid nitrogen filling port for adding liquid nitrogen to the cooling jug.

[0016] On the other hand, the present invention provides a two-way precise temperature and electromagnetic field control method based on the in-situ sample holder of the transmission electron microscope, which includes:

[0017] The sample is transferred onto a four-electrode MEMS thermoelectric chip by dropping or using a focused ion beam instrument.

[0018] Confirm under a light microscope that the tip of the sample rod is clean and free of foreign objects;

[0019] Liquid nitrogen is added into the refrigeration vessel through the liquid nitrogen filling port;

[0020] Loosen the tightening screws, load the four-electrode MEMS thermoelectric chip containing the sample onto the stage through the chip limiting slot, and adjust the chip position so that the four-electrode tungsten needles are aligned with the four electrodes on the four-electrode MEMS thermoelectric chip. Finally, tighten the tightening screws to complete the sample loading.

[0021] The sample rod head is inserted directly into the transmission electron microscope sample stage and pushed to the limit position, and the inside of the transmission electron microscope is evacuated.

[0022] Insert the sample rod into the transmission electron microscope sample stage, rotate and install it in place, and connect the external control interface of the handle to the external controller via the control line;

[0023] When it is necessary to lower the temperature of the sample area, liquid nitrogen in the refrigeration vessel flows into the liquid nitrogen circulation pipe through dual control of the inflow and outflow of the micro flow controller and circulates to the temperature-conducting plate to contact the chip, thereby lowering the temperature of the sample area. When it is necessary to raise the temperature of the sample area, a four-electrode MEMS thermoelectric chip is used for heating, thereby precisely applying the required temperature field through both cooling and heating.

[0024] Simultaneously, an external controller controls the four-electrode MEMS thermoelectric chip to apply a specific electric field. The magnitude of the parallel magnetic field applied to the sample is controlled by controlling the voltage and current applied to the U-shaped electromagnet. The thermoelectric shield isolates the U-shaped electromagnet from the influence of the external temperature field and electric field, avoiding magnetic field instability during heat transfer. It also avoids the influence of the electric field on the magnetic field when the electric field is applied, thereby enabling the measurement of the electrical and magnetic properties of the sample under a specific temperature field.

[0025] Compared with existing technologies, the liquid nitrogen in the cooling vessel of this invention flows into the liquid nitrogen circulation pipe through a micro flow controller and circulates to the temperature-conducting plate, where it contacts the chip to achieve a controllable temperature reduction. Simultaneously, a four-electrode MEMS chip (with four electrodes, two energized to apply an electric field and two energized to control heating) is used in conjunction with the liquid nitrogen cooling system to achieve bidirectional temperature control from extremely low temperatures (-196℃) to high temperatures (1000℃). This means that heating is achieved through the MEMS thermoelectric chip when heating is needed, and cooling is achieved by controlling the liquid nitrogen flow rate through the micro flow controller, allowing for flexible control of both heating and cooling. It also supports gradient temperature adjustment and precise control. The sample rod of this invention has a rapid cooling function. On one hand, the four-electrode MEMS thermoelectric chip itself contacts the temperature-conducting plate to achieve rapid cooling. On the other hand, the four-electrode MEMS thermoelectric chip is fixed and installed through a limiting groove made of a high thermal conductivity material, and the limiting groove is connected to the temperature-conducting plate. This allows the cooling capacity of the liquid nitrogen to be rapidly and efficiently transferred to the four-electrode MEMS thermoelectric chip, which then acts on the sample.

[0026] The U-shaped electromagnet of this invention is completely housed within a thermoelectric shield. The structure of the thermoelectric shield matches that of the electromagnet, both being U-shaped, with both ends of the U-shaped structure sealed. The two arms of the U-shaped electromagnet are positioned on either side of the stage, enabling the application of a parallel magnetic field to the sample. The thermoelectric shield employs a multi-layered composite thermal and electrical insulating material, which, from the inside out, sequentially includes a polyimide inner layer, an alumina fiber felt middle layer, an alumina ceramic outer layer, and a nano-silica surface treatment layer. Alumina shields the electric field, maintaining the material's flexibility and temperature resistance. The alumina fiber felt has extremely low thermal conductivity, effectively isolating heat transfer and providing structural strength. The alumina ceramic further shields the external electric field, and the nano-silica surface treatment layer reduces the penetration paths of heat and electric fields. Thermoelectric shielding can effectively isolate the influence of external temperature and electric fields on U-shaped electromagnets, avoid magnetic field instability during heat transfer, and also avoid the influence of electric field on magnetic field when electric field is applied. This enables the determination of electrical and magnetic properties of samples under specific temperature fields and maintains high precision, stability and repeatability under multi-field coupling conditions. Attached Figure Description

[0027] Figure 1 This is an overall view of the in-situ sample holder for a multi-field coupled transmission electron microscope, as illustrated in the embodiment.

[0028] Figure 2 This is an overall view of the in-situ sample holder for a multi-field coupled transmission electron microscope, as illustrated in the embodiment.

[0029] Figure 3 This is a schematic diagram of a partial front structure of the sample rod head, as illustrated in the embodiment.

[0030] Figure 4 This is a front view of the miniature U-shaped electromagnet and thermoelectric shield structure of the sample rod head, as illustrated in the embodiment. Detailed Implementation

[0031] The present invention will be further described and illustrated below with reference to specific embodiments. The embodiments described are merely examples of the content of this disclosure and do not limit the scope of the invention. The technical features of each embodiment in the present invention can be combined accordingly, provided that there is no mutual conflict.

[0032] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0033] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection, an electrical connection, a physical connection, or a wireless communication connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two elements or the interaction between two elements, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0034] The present invention will be further described in detail below with reference to the accompanying drawings.

[0035] like Figure 1 and Figure 2 This is a schematic diagram of the appearance of the in-situ sample rod in a multi-field coupled transmission electron microscope from different perspectives. Figure 3 and Figure 4 This is a schematic diagram of the relevant structure of the sample rod head. The in-situ sample rod of this embodiment includes a sample rod head 1, a sample rod body, and a handle 8 in its overall structure; the sample rod head 1 and the handle 8 are respectively disposed at both ends of the sample rod body. The sample rod body includes a first hollow rod 3 and a second hollow rod 6; wherein, the diameter of the first hollow rod 3 is smaller than that of the second hollow rod 6, one end of the first hollow rod 3 is connected to the sample rod head 1, and the other end is provided with a tapered transition section 5, which is connected to the second hollow rod 6, and a sealing ring 4 is provided between the tapered transition section 5 and the second hollow rod 6.

[0036] like Figure 3 and Figure 4 As shown, the sample rod head 1 in this embodiment includes a stage 22, a four-electrode MEMS thermoelectric chip located inside the stage, a U-shaped electromagnet 12, a PCB circuit board 19, a thermoelectric shield 23 for wrapping the micro electromagnet 12, and a temperature-conducting plate 17 disposed at the rear end of the stage; wherein the stage is provided with a MEMS thermoelectric chip limiting groove 16 and a four-electrode tungsten needle 15, the MEMS thermoelectric chip limiting groove 16 is used for positioning the chip and sample, and the PCB circuit board 19 is placed at the rear end of the micro U-shaped electromagnet 12 to centrally connect the micro electromagnet and the four-electrode tungsten needle circuit.

[0037] The miniature U-shaped electromagnet 12 is mainly used to generate a parallel magnetic field. In this invention, the sample is at the micrometer level. The two arms of the electromagnet 12 are located on both sides of the stage, and the magnetic field it generates can be considered parallel in the sample area. In a specific embodiment of this invention, the miniature U-shaped electromagnet 12 includes enameled wire, a U-shaped solenoid, and a U-shaped iron core disposed therein. The miniature electromagnet 12 is disposed on both sides of the stage 22, and the enameled wire is wound around the U-shaped solenoid. The enameled wire is connected to a PCB circuit board 19 via a wire, and the PCB circuit board 19 is connected to the external control interface 9 via a wire passing through the sample rod.

[0038] The size of a miniature electromagnet is primarily determined by the size of its miniature solenoid. Within the sample rod, the electromagnet should be as small as possible while still ensuring it can apply the appropriate magnetic field required for the test. In this invention, the magnetic field strength is altered by adjusting the voltage applied to the U-shaped solenoid.

[0039] To avoid the influence of temperature changes and the applied electric field on the magnetic field generated by the miniature electromagnet, in a specific embodiment of the present invention, a thermoelectric shield is used as the outer shell of the miniature electromagnet to provide thermoelectric shielding. The thermoelectric shield is a U-shaped shell surrounding the miniature electromagnet, with both ends sealed with thermoelectric shielding material. The shell is hollow, accommodating the U-shaped electromagnet. The thermoelectric shield and the thermoelectric shielding material are made of multi-layer composite thermal and electrical insulating material. In this embodiment, the multi-layer composite thermal and electrical insulating material, from the innermost layer to the outermost layer, includes a polyimide inner layer, a ceramic fiber felt middle layer, an alumina ceramic outer layer, and a surface treatment layer. The ceramic fiber felt middle layer can be made of alumina fiber felt, and the surface treatment layer is made of a nano-oxide film, such as a nano-silica film. All of the above materials can be commercially available. Polyimide possesses excellent electrical insulation properties, enhancing the electric field shielding effect, while its low thermal conductivity effectively isolates heat transfer. Alumina fiber felt possesses extremely low thermal conductivity (approximately 0.069-0.321 W / m·K), effectively isolating heat transfer. Furthermore, it provides structural strength, preventing brittle fracture of the outer ceramic layer and ensuring the stability and durability of the entire thermoelectric shield. Alumina ceramic exhibits excellent electrical insulation properties, effectively shielding external electric fields. The nanostructure of nano-silica effectively reduces the penetration paths of heat and electric fields, enhancing the thermal insulation and electric field shielding capabilities of the multi-layered structure. This thermoelectric shield not only possesses excellent thermal insulation and electric field shielding performance but also achieves stability and reliability under high and low temperature environments through innovative nanostructure design. The thermoelectric shield in this embodiment avoids magnetic field instability caused by heat transfer, thus preventing issues affecting the microstructure or electromagnetic response of the sample; it also avoids the influence of the electric field on the magnetic field when an electric field is applied, making the magnetic field more stable. Moreover, miniature U-shaped electromagnets 12 are placed on both sides of the sample stage, applying a strong parallel magnetic field to the sample.

[0040] In one specific embodiment of the present invention, the two ends of the U-shaped structure of the thermoelectric shield 23 are sealed and contact the temperature-conducting plate 17, thereby forming an area on the stage 22 for setting the four-electrode MEMS thermoelectric chip and the MEMS thermoelectric chip limiting groove 16. Furthermore, the temperature-conducting plate 17 also contacts the rear end of the four-electrode MEMS thermoelectric chip and one end of the MEMS thermoelectric chip limiting groove 16, respectively. There are two MEMS thermoelectric chip limiting grooves 16, located on both sides of the MEMS thermoelectric chip. The MEMS thermoelectric chip limiting grooves 16 are made of aluminum nitride ceramic material with high thermal conductivity, good mechanical strength, low coefficient of thermal expansion, electrical insulation, and non-magnetic properties. The two ends of the MEMS thermoelectric chip are respectively fixedly installed in the two MEMS thermoelectric chip limiting grooves 16. The limiting grooves serve to stabilize the chip and assist in heat conduction. The two arms of the U-shaped structure of the thermoelectric shield are located outside the two limiting grooves.

[0041] In one specific embodiment of the present invention, an external control interface 9 is provided at the end of the handle 8. The miniature electromagnet 12 and the four-electrode tungsten needle 15 are electrically connected to the external control interface 9 through the PCB circuit board 19. The external control interface 9 is connected to an external controller. The handle 8 contains a cooling tank, which consists of an inner liquid nitrogen tank and an outer shell, with a vacuum interlayer in between to isolate heat transfer. The double-layer interlayer is silver-plated to reduce heat radiation heat transfer. The liquid nitrogen in the cooling tank is circulated into the liquid nitrogen circulation pipe through a dual control of the inflow micro flow controller 24 and the outflow micro flow controller 25, and then contacts the chip at the temperature-conducting plate to achieve a controllable temperature reduction. At the same time, the four-electrode MEMS chip has a heating function. The combined use with the liquid nitrogen cooling system can achieve bidirectional temperature control from extremely low temperature (-196℃) to high temperature (1000℃), supporting gradient temperature adjustment and precise control. The inflow micro flow controller 24 and the outflow micro flow controller 25 can be controlled by feedback. When it is necessary to reduce the temperature as quickly as possible, the liquid nitrogen flow rate is increased; when the temperature change demand is small, the flow rate is reduced or the two flow controllers 24 are turned off.

[0042] In a specific embodiment of the present invention, the liquid nitrogen in the cooling jug is circulated through the liquid nitrogen circulation pipe 18 to the temperature-conducting plate 17 to contact the chip and reduce the temperature. At the same time, a four-electrode MEMS thermoelectric chip with heating function is used to accurately apply the required temperature field through bidirectional temperature control capability. The handle 8 is provided with a liquid nitrogen filling port 10 for adding liquid nitrogen into the cooling jug. The liquid nitrogen filling port and the cooling jug connecting pipe 11 are spirally pleated to reduce heat conduction.

[0043] An external controller is used to control the sample rod of the present invention to achieve various field changes by changing electrical signals. The present invention does not limit its form. In an optional embodiment, the external controller adjusts the temperature applied to the sample by adjusting the voltage of the heating electrode, adjusts the liquid nitrogen flow rate by adjusting the inflow and outflow micro flow controllers to achieve a controllable reduction of temperature, adjusts the magnitude of the magnetic field by adjusting the voltage applied to the micro electromagnet, and adjusts the magnitude of the electric field applied to the sample by adjusting the voltage applied to the voltage electrode.

[0044] like Figure 3 and Figure 4 As shown, the stage 22 of the present invention mainly includes: a stage body, a chip limiting groove 16, a chip fixing plate 13, and a four-electrode tungsten needle 15; the chip limiting groove 16 is opened on both sides of the stage and is lower than the height of the sides; the chip fixing plate 13 is located at the front end of the stage and is used to fix the chip; the four-electrode tungsten needle 15 is at least partially disposed below the chip fixing plate 13, and the contact degree between the four-electrode tungsten needle and the four-electrode MEMS thermoelectric chip can be adjusted by the tightening screw 14 on the chip fixing plate 13.

[0045] In order to control the opening and closing of the valve of the transmission electron microscope, a guide pin 2 is provided on the first hollow rod 3, and the guide pin 1 is configured to guide the sample rod head 1.

[0046] To achieve sensing and positioning, a sensing pin 7 is provided on the handle 8, which is configured to enable sensing and positioning after the sample rod head 1 is inserted into the electron lens.

[0047] The multi-field coupled transmission electron microscope in-situ sample holder provided in this embodiment can simultaneously achieve coordinated control of electric field, magnetic field, and temperature field (heating and cooling), realizing the comprehensive application and adjustment of multiple physical fields within an experimental system, which greatly improves the flexibility of in-situ material testing and experimental capabilities in complex environments.

[0048] The following describes the control method for the in-situ sample holder of a multi-field coupled transmission electron microscope. Before control, the external controller is connected to the sample holder through the external control interface. The control method is as follows:

[0049] The sample is transferred onto a four-electrode MEMS thermoelectric chip by dropping or by using a focused ion beam (FIB) instrument.

[0050] Under an optical microscope, confirm that the tip of sample rod 1 is clean and free of foreign objects;

[0051] Liquid nitrogen is added into the refrigeration vessel through the liquid nitrogen filling port 10;

[0052] Loosen the loosening screw 14, load the four-electrode MEMS thermoelectric chip containing the sample onto the stage 22 through the chip limiting groove 16, and adjust the chip position so that the four-electrode tungsten needles are aligned with the four electrodes on the four-electrode MEMS thermoelectric chip. Finally, tighten the loosening screw 14 to complete the sample loading.

[0053] The sample rod head 1 is inserted directly into the transmission electron microscope sample stage and pushed to the limit position, and the inside of the transmission electron microscope is evacuated.

[0054] The sample rod head 1 is inserted into the transmission electron microscope sample stage, rotated and installed in place, and the external control interface 9 of the handle 8 is connected to the external controller via the control line.

[0055] When it is necessary to lower the temperature of the sample area, liquid nitrogen in the cooling vessel circulates through the liquid nitrogen circulation pipe to the temperature-conducting plate, which then contacts the chip to lower the temperature of the sample area. The temperature-conducting plate directly contacts the four-electrode MEMS thermoelectric chip to transfer cold energy. On the other hand, the temperature-conducting plate transfers cold energy to the four-electrode MEMS thermoelectric chip through a limiting groove made of a high thermal conductivity material. Thus, the cold energy of the liquid nitrogen can be transferred to the four-electrode MEMS thermoelectric chip quickly and in high throughput. When it is necessary to raise the temperature of the sample area, the four-electrode MEMS thermoelectric chip is used for heating, thereby precisely applying the required temperature field through both cooling and heating.

[0056] Simultaneously, the electrical properties of the sample under a specific temperature field are measured by applying a specific electric field through an external controller chip, and the magnetic properties of the sample under a specific temperature field are measured by controlling the magnitude of the parallel magnetic field applied to the sample by controlling the magnitude of the voltage and current applied to the micro electromagnet 12.

[0057] As demonstrated by the above methods, this in-situ sample holder for transmission electron microscopy, through the combined use of a MEMS thermoelectric chip and a liquid nitrogen cooling system, enables bidirectional temperature control from extremely low temperatures (-196℃) to high temperatures (1000℃), supporting gradient temperature adjustment and precise control. This bidirectional control gives the invention significant advantages in studying dynamic processes such as phase transitions and the evolution of material microstructures. The use of a four-electrode MEMS thermoelectric chip achieves dual control of micro-area heating and electric field application. It allows for precise adjustment of sample temperature, electric field, and magnetic field at the micrometer or nanometer scale, making it particularly suitable for testing the local properties of nanomaterials and semiconductor materials.

[0058] The sample rod, combined with an external controller feedback system, enables automated multi-field control of temperature, magnetic field, and electric field, improving experimental stability and operational convenience. In this invention, a thermoelectric shield is placed around the U-shaped electromagnet, effectively reducing interference between the magnetic and thermal fields, as well as between the magnetic and electric fields, ensuring experimental accuracy and repeatability in multi-field environments. Particularly in high-temperature environments, the interference of high-temperature interference with the application of precise magnetic fields is effectively suppressed. The sample rod is designed with a modular structure, allowing for rapid switching between different functional modules (such as higher-strength electromagnets or chips with different temperature control ranges), greatly improving the flexibility and maintainability of the equipment and reducing experimental costs.

Claims

1. A multi-field coupled transmission electron microscope in-situ sample rod, comprising a sample rod head (1), a sample rod body, and a hand grip (8); the sample rod head (1) and the hand grip (8) are respectively disposed at both ends of the sample rod body; Its features are, The sample rod head (1) includes a stage (22), a four-electrode MEMS thermoelectric chip, a U-shaped electromagnet (12), a PCB circuit board (19), a thermoelectric shield (23) for wrapping the U-shaped electromagnet (12), and a temperature-conducting plate (17) disposed at the rear end of the stage; wherein the stage is provided with a MEMS thermoelectric chip limiting groove (16) and a four-electrode tungsten needle (15), the MEMS thermoelectric chip limiting groove (16) being used for positioning the MEMS thermoelectric chip. The thermoelectric shield (23) is U-shaped, and the U-shaped electromagnet (12) is completely placed inside the thermoelectric shield (23). The two ends of the U-shaped structure of the thermoelectric shield (23) are sealed. The shell wall of the thermoelectric shield (23) is made of multi-layer composite thermal insulation and electrical insulation material, which includes, from the inside to the outside, a polyimide inner layer, a ceramic fiber felt middle layer, an alumina ceramic outer layer and a surface treatment layer. The two arms of the U-shaped electromagnet (12) are respectively placed on both sides of the stage, which can apply a parallel magnetic field to the sample. An external control interface (9) is provided at the end of the handle (8). The U-shaped electromagnet (12) and the four-electrode tungsten needle (15) are electrically connected to the external control interface (9) through the PCB circuit board (19). The handle (8) contains a cooling bottle, which includes an inner liquid nitrogen bottle and an outer shell, with a vacuum interlayer in between to isolate heat transfer. The liquid nitrogen in the refrigeration vessel is circulated through the liquid nitrogen circulation tube (18) to the temperature-conducting plate (17) to contact the chip and reduce its temperature. The liquid nitrogen circulation tube (18) is equipped with an inflow micro flow controller (24) and an outflow micro flow controller (25) for dual control of the inflow and outflow of liquid nitrogen. The four-electrode MEMS thermoelectric chip has a heating function and is used in conjunction with the temperature-conducting plate (17) to accurately apply the required temperature field through bidirectional temperature control. The handle (8) is equipped with a liquid nitrogen filling port (10) for adding liquid nitrogen into the refrigeration vessel.

2. The in-situ sample holder for a multi-field coupled transmission electron microscope according to claim 1, characterized in that, The U-shaped electromagnet (12) includes an enameled wire, a U-shaped solenoid and a U-shaped iron core disposed therein. The enameled wire is wound around the outside of the U-shaped solenoid and is connected to the PCB circuit board (19) via a wire.

3. The in-situ sample holder for a multi-field coupled transmission electron microscope according to claim 1, characterized in that, The ceramic fiber felt middle layer of the thermoelectric shield (23) is made of alumina fiber felt, and the surface treatment layer is made of nano-silica film. The two ends of the U-shaped structure of the thermoelectric shield (23) are sealed with the multi-layer composite thermal insulation and electrical insulation material.

4. The in-situ sample holder for a multi-field coupled transmission electron microscope according to claim 1, characterized in that, After the two ends of the U-shaped structure of the thermoelectric shield (23) are sealed, they contact the temperature-conducting plate (17) to form an area on the stage (22) for setting the four-electrode MEMS thermoelectric chip and the MEMS thermoelectric chip limiting groove (16); the temperature-conducting plate (17) contacts the four-electrode MEMS thermoelectric chip and the MEMS thermoelectric chip limiting groove (16) respectively. There are two MEMS thermoelectric chip limiting grooves (16), which are located on both sides of the MEMS thermoelectric chip respectively. The MEMS thermoelectric chip limiting grooves (16) are made of aluminum nitride ceramic material. The two ends of the MEMS thermoelectric chip are fixedly installed in the two MEMS thermoelectric chip limiting grooves (16) respectively.

5. The in-situ sample holder for a multi-field coupled transmission electron microscope according to claim 1, characterized in that, The stage (22) includes: The stage itself; Chip limiting grooves (16) are provided on both sides of the stage and are lower than the height of the sides; The chip fixing plate (13) is located at the front end of the stage and is used to fix the four-electrode MEMS thermoelectric chip. The four-electrode tungsten needle (15) is at least partially disposed below the chip fixing plate (13) and the contact degree between the four-electrode tungsten needle and the four-electrode MEMS thermoelectric chip can be adjusted by the tightening screw (14) on the chip fixing plate (13).

6. The in-situ sample holder for a multi-field coupled transmission electron microscope according to claim 1, characterized in that, The sample rod body includes a first hollow rod (3) and a second hollow rod (6); Wherein, the diameter of the first hollow rod (3) is smaller than that of the second hollow rod (6), one end of the first hollow rod (3) is connected to the sample rod head (1), and the other end is provided with a tapered transition section (5), the tapered transition section (5) is connected to the second hollow rod (6), and a sealing ring (4) is provided between the tapered transition section (5) and the second hollow rod (6); The wires leading out from the PCB circuit board (19) pass through the first hollow rod (3) and the second hollow rod (6) and are connected to the external control interface (9).

7. The in-situ sample holder for a multi-field coupled transmission electron microscope according to claim 6, characterized in that, The first hollow rod (3) is provided with a guide pin (2), which is configured to guide the sample rod head (1) and control the opening and closing of the valve of the transmission electron microscope.

8. The in-situ sample holder for a multi-field coupled transmission electron microscope according to claim 1, characterized in that, The handle (8) is provided with a sensing pin (7), which is used for sensing and positioning of the sample rod head (1) after it is inserted into the electron lens.

9. A method for bidirectional precise temperature and electromagnetic field control of an in-situ sample holder for a multi-field coupled transmission electron microscope as described in any one of claims 1-8, characterized in that... include: The sample is transferred onto a four-electrode MEMS thermoelectric chip by dropping or using a focused ion beam instrument. Under a light microscope, confirm that the front end of the sample rod (1) is clean and free of foreign matter; Liquid nitrogen is added to the refrigeration vessel through the liquid nitrogen filling port (10); Loosen the loosening screw (14), load the four-electrode MEMS thermoelectric chip containing the sample onto the stage (22) through the chip limiting groove (16), adjust the chip position so that the four-electrode tungsten needle is aligned with the four electrodes on the four-electrode MEMS thermoelectric chip, and finally tighten the loosening screw (14) to complete the sample loading. The sample rod head (1) is inserted directly into the transmission electron microscope sample stage and pushed to the limit position, and the inside of the transmission electron microscope is evacuated. Insert the sample rod head (1) into the transmission electron microscope sample stage, rotate and install it in place, and connect the external control interface (9) of the hand grip (8) to the external controller through the control line; When it is necessary to lower the temperature of the sample area, the liquid nitrogen in the refrigeration vessel flows into the liquid nitrogen circulation pipe (18) through the dual control of the inflow micro flow controller (24) and the outflow micro flow controller (25) and circulates to the temperature-conducting plate (17) to contact the chip, thereby lowering the temperature of the sample area. When it is necessary to raise the temperature of the sample area, a four-electrode MEMS thermoelectric chip is used for heating, thereby applying the required temperature field precisely through both cooling and heating. Meanwhile, a specific electric field is applied to the four-electrode MEMS thermoelectric chip by an external controller. The magnitude of the parallel magnetic field applied to the sample is controlled by controlling the voltage and current applied to the U-shaped electromagnet (12). The thermoelectric shield (23) isolates the influence of the external temperature field and electric field on the U-shaped electromagnet (12), avoids magnetic field instability during heat transfer, and also avoids the influence of the electric field on the magnetic field when the electric field is applied, thereby realizing the measurement of the electrical and magnetic properties of the sample under a specific temperature field.

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