Multi-field coupling transmission electron microscope in-situ sample rod and bidirectional accurate temperature and electromagnetic field control system method thereof

Abstract

The invention discloses a multi-field coupling transmission electron microscope in-situ sample rod and a bidirectional accurate temperature and electromagnetic field control system method thereof, and belongs to the field of transmission electron microscopes. The rod head of the sample rod comprises an objective table, a micro U-shaped electromagnet and a PCB (Printed Circuit Board) which are arranged in the objective table, a temperature conducting plate and a liquid nitrogen circulating pipe which are arranged at the rear end of the objective table, and a four-electrode MEMS (Micro Electro Mechanical System) thermoelectric chip arranged on the objective table. Dual control of heating and an electric field is realized through the MEMS thermoelectric chip, and bidirectional temperature adjustment of a sample is realized in combination with a liquid nitrogen cooling system. And meanwhile, the sample rod is also integrated with a micro U-shaped electromagnet to apply a controllable parallel magnetic field. The whole system can carry out multi-field coupling experiments under extreme conditions, such as dynamic researches of electricity, magnetism, phase change and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of transmission electron microscope (TEM) in-situ experiments, and in particular relates to a multi-field coupled transmission electron microscope in-situ sample rod and a bidirectional precise temperature and electromagnetic field control system method thereof. Background Art

[0002] Transmission electron microscopy (TEM) is an important tool for studying the microstructure and physical 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 conditions of heating, cooling, stress, electric field, magnetic field, etc.).

[0003] At present, most TEM sample holder technologies on the market and in the literature mainly include heated sample holders, liquid nitrogen cooled sample holders, electric field and magnetic field controlled sample holders, etc., which can apply one or two physical fields (such as electric field and heating, magnetic field and cooling, etc.). However, there are still many challenges in realizing multi-field coupling control, especially the technology of simultaneous precise control of electric field, magnetic field, heating and cooling. The following are some major problems in the existing technology:

[0004] 1. High difficulty in multi-field coupling: Existing TEM sample rod technology mainly focuses on single physical field or dual field control. For example, common heating sample rods and electric field sample rods can independently achieve heating or electric field application, but when the electric field, magnetic field and temperature field interact, there is a problem of field interference. Especially when the sample is in a high temperature, electric field and magnetic field environment at the same time, electromagnetic interference, thermal runaway and other phenomena seriously affect the experimental accuracy.

[0005] 2. Limited temperature control range: The temperature control range of most heating and cooling systems is relatively narrow, especially the accuracy of two-way temperature control (heating and cooling), and the control of temperature gradient change is not stable enough. For example, the existing liquid nitrogen cooling sample rod only supports low-temperature cooling, but does not have the corresponding heating function; and the cooling function of the heated sample rod often does not have the ability to quickly convert temperature, which poses a challenge to dynamic experiments (such as phase change and microstructure evolution).

[0006] 3. Inaccurate coupling control of electromagnetic field and temperature field: In the existing technology, even if the joint control of multiple physical fields (such as electric field and heating, magnetic field and cooling) is achieved, electromagnetic interference and thermal interference are still difficult to overcome. For example, the magnetic field sample rod usually causes magnetic field instability due to heat transfer during heating or cooling, which in turn affects the microstructure or electromagnetic response of the sample; the influence of the electric field on the magnetic field is mainly reflected in the generation of additional magnetic fields through electromagnetic induction effects under high-intensity electric fields, and the electric field-induced current causes magnetic field distortion, thereby destroying the uniformity and stability of the magnetic field. In addition, changes in the electric field may also trigger a charge accumulation effect, interfering with the distribution of the magnetic field, especially in dynamic electric fields or micro-nanoscale experiments.

[0007] 4. Insufficient micro-area control and precision: In the existing TEM in-situ sample holder, it is still a technical difficulty to accurately control the temperature, electric field and magnetic field of the sample micro-area. Although MEMS chips have been used for micro-area heating control in recent years, how to realize the combined application of MEMS chips with electric fields and magnetic fields, and how to regulate the effects of different physical fields at the micrometer or nanometer scale, are still blank in the existing technology.

[0008] In summary, the existing TEM sample holder technology has significant limitations in terms of multi-field coupling control, temperature range and accuracy, micro-field application, etc., especially the lack of effective solutions under the coordinated control of electric field, magnetic field, heating and cooling. Therefore, there is an urgent need for a new type of sample holder that can achieve multi-field coupling, precise temperature control and micro-area regulation in TEM experiments to meet the experimental needs of materials science and other cutting-edge research. Summary of the invention

[0009] In order to overcome the shortcomings of the prior art, the present invention provides a multi-field coupled transmission electron microscope in-situ sample holder and a method for controlling a bidirectional precise temperature and electromagnetic field. The present invention is intended to be used in transmission electron microscope (TEM) in-situ experiments to achieve precise coordinated control of multiple physical fields (electric field, magnetic field, heating, cooling) and maintain high precision, stability and repeatability under multi-field coupling conditions.

[0010] In one aspect, the present invention provides an in-situ sample holder for a multi-field coupled transmission electron microscope, comprising a sample holder head, a sample holder shaft and a hand grip; the sample holder head and the hand grip are respectively arranged at two ends of the sample holder shaft;

[0011] The sample rod head includes a stage, a four-electrode MEMS thermoelectric chip located in the stage, a U-shaped electromagnet, a PCB circuit board and a thermoelectric shielding cover for wrapping the U-shaped electromagnet, and a temperature conducting plate arranged at the rear end of the stage; wherein a MEMS thermoelectric chip limiting groove and a four-electrode tungsten needle are arranged at the stage, and the MEMS thermoelectric chip limiting groove is used for positioning the MEMS thermoelectric chip,

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

[0013] An external control interface is provided at the end of the hand grip, 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 pot inside, which includes an inner liquid nitrogen pot and an outer shell, with a vacuum interlayer in the middle to isolate heat transfer;

[0015] The liquid nitrogen in the refrigeration kettle is circulated to the temperature conduction plate through the liquid nitrogen circulation pipe and contacts the chip to reduce the temperature. The liquid nitrogen circulation pipe is provided with an inflow micro flow controller and an outflow micro flow controller for doubly controlling 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 conduction plate to accurately apply the required temperature field through the two-way temperature control capability. The hand handle is provided with a liquid nitrogen filling port for adding liquid nitrogen to the refrigeration kettle.

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

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

[0018] Confirm under a light microscope that the front end of the sample rod is clean and free of foreign matter;

[0019] Add liquid nitrogen into the refrigeration pot through the liquid nitrogen filling port;

[0020] Loosen the loosening screw, load the four-electrode MEMS thermoelectric chip loaded with the sample onto the stage through the chip limiting groove, and adjust the chip position so that the four-electrode tungsten needle faces the four electrodes on the four-electrode MEMS thermoelectric chip, and finally tighten the loosening screw. The sample loading is now completed;

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

[0022] The sample rod head is inserted into the sample stage of the transmission electron microscope, rotated and installed in place, and the external control interface of the hand grip is connected to the external controller through a control line;

[0023] When the temperature of the sample area needs to be lowered, the liquid nitrogen in the refrigeration pot flows into the liquid nitrogen circulation tube through the dual control of the inflow micro flow controller and the outflow micro flow controller, and circulates to the temperature conduction plate to contact the chip to reduce the temperature of the sample area. When the temperature of the sample area needs to be increased, a four-electrode MEMS thermoelectric chip is used for heating, thereby accurately applying the required temperature field through dual cooling and heating.

[0024] At the same time, an external controller is used to control the four-electrode MEMS thermoelectric chip to apply a specific electric field, and the size 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 influence of the external temperature field and electric field on the U-shaped electromagnet, avoiding the instability of the magnetic field caused by the heat transfer process, and also avoiding 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.

[0025] Compared with the prior art, the liquid nitrogen in the refrigeration pot of the present invention flows into the liquid nitrogen circulation pipe through a micro flow controller and circulates to the temperature conduction plate to contact the chip to achieve controllable temperature reduction. At the same time, a four-electrode MEMS chip (the chip has four electrodes, two electrodes are energized to apply an electric field, and two electrodes are energized to control heating) is used in conjunction with a liquid nitrogen cooling system to achieve two-way temperature control from extremely low temperature (-196°C) to high temperature (1000°C) (that is, if the temperature needs to be increased, the MEMS thermoelectric chip is used for heating, and if the temperature needs to be reduced, the liquid nitrogen flow rate is controlled by the micro flow controller for cooling, and the temperature increase and cooling can be flexibly controlled), supporting temperature gradient adjustment and precise control. The sample rod head of the present invention has the function of rapid cooling. On the one hand, the four-electrode MEMS thermoelectric chip itself contacts the temperature conduction plate to achieve rapid cooling. On the other hand, the four-electrode MEMS thermoelectric chip is fixed and installed through a limit groove made of high thermal conductivity material, and the limit groove is connected to the temperature conduction plate, so that the coldness of the liquid nitrogen can be quickly and high-throughput transferred to the four-electrode MEMS thermoelectric chip, and then act on the sample.

[0026] The U-shaped electromagnet of the present invention is completely placed in the thermoelectric shielding cover, the structure of the thermoelectric shielding cover matches the thermoelectric shielding cover, both are U-shaped, and the two ends of the U-shaped structure of the thermoelectric shielding cover are sealed; the two arms of the U-shaped electromagnet are respectively placed on both sides of the stage, and can apply a parallel magnetic field to the sample. The thermoelectric shielding cover adopts a multi-layer composite thermal insulation and electrical insulation material, which includes a polyimide inner layer, an alumina fiber felt middle layer, an alumina ceramic outer layer and a nano-silicon dioxide surface treatment layer in sequence from the inside to the outside, wherein alumina can shield the electric field and maintain the flexibility and temperature resistance of the material, the alumina fiber felt has extremely low thermal conductivity and can effectively isolate heat transfer, and can also provide structural strength, the alumina ceramic further shields the external electric field, and the nano-silicon dioxide surface treatment layer reduces the penetration path of heat and electric field. The thermoelectric shield can effectively isolate the influence of external temperature field and electric field on U-shaped electromagnet, avoid magnetic field instability caused by heat transfer, and also avoid the influence of electric field on magnetic field when electric field is applied, so as to realize the measurement of electrical and magnetic properties of samples under specific temperature field and maintain high precision, stability and repeatability under multi-field coupling conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is an overall diagram of the in-situ sample holder of a multi-field coupled transmission electron microscope as shown in the embodiment.

[0028] Figure 2 It is an overall diagram of the in-situ sample holder of a multi-field coupled transmission electron microscope as shown in the embodiment.

[0029] Figure 3 It is a schematic diagram of the partial structure of the front side of the sample rod head according to the embodiment.

[0030] Figure 4 It is a front view schematic diagram of a micro U-shaped electromagnet and a thermoelectric shielding cover structure of a sample rod head according to an embodiment. DETAILED DESCRIPTION

[0031] The present invention is further described and illustrated below in conjunction with specific embodiments. The embodiments are merely exemplary of the present disclosure and do not define the scope of limitation. The technical features of each embodiment of the present invention may be combined accordingly without conflicting with each other.

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

[0033] In the present invention, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, a physical connection, or a wireless communication connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0034] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0035] like Figure 1 and Figure 2 Schematic diagram of the appearance of the in-situ sample rod of a multi-field coupled transmission electron microscope at different viewing angles. Figure 3 and Figure 4 Schematic diagram of the relevant structure of the sample rod head. The in-situ sample rod of the embodiment comprises a sample rod head 1, a sample rod shaft and a hand grip 8 in terms of overall structure; the sample rod head 1 and the hand grip 8 are respectively arranged at both ends of the sample rod shaft. The sample rod shaft comprises a first hollow rod 3 and a second hollow rod 6; wherein the diameter of the first hollow rod 2 is smaller than that of the second hollow rod 6, one end of the first hollow rod 2 is connected to the sample rod head 1, and the other end is provided with a conical transition section 5, the conical transition section 5 is connected to the second hollow rod 6, and a sealing ring 4 is arranged between the conical transition section 5 and the second hollow rod 6.

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

[0037] The miniature U-shaped electromagnet 12 is mainly used to generate a parallel magnetic field. In the present invention, the sample is at the micron level. The two arms of the electromagnet 12 are located on both sides of the stage. The magnetic field generated by the electromagnet 12 can be considered to be parallel in the sample area. In a specific embodiment of the present invention, the miniature U-shaped electromagnet 12 includes an 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 outside of the U-shaped solenoid; the enameled wire is connected to the 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 body.

[0038] The size of the micro electromagnet is mainly determined by the size of the micro solenoid. In the sample rod, the size of the electromagnet should be as small as possible while ensuring that the appropriate magnetic field required for the test can be applied to the sample. In the present invention, the size of the magnetic field is changed by adjusting the voltage applied to the U-shaped solenoid.

[0039] In order to avoid the influence of temperature change and applied electric field on the magnetic field generated by the micro electromagnet, in a specific embodiment of the present invention, a thermoelectric shielding cover is used as the shell of the micro electromagnet to perform thermoelectric shielding on the micro electromagnet, wherein the shape of the thermoelectric shielding is a shell wrapped around the outside of the micro electromagnet, which is U-shaped, and both ends are also sealed with thermoelectric shielding materials. The inside of the shell is hollow, and the hollow area accommodates the U-shaped electromagnet. The material of the thermoelectric shielding cover and the thermoelectric shielding material is a multi-layer composite thermal insulation and electrical insulation material. In an embodiment of the present invention, the multi-layer composite thermal insulation and electrical insulation material includes a polyimide inner layer, a ceramic fiber felt middle layer, an alumina ceramic outer layer and a surface treatment layer in sequence from the inner layer to the outer layer; wherein the ceramic fiber felt middle layer material can be alumina fiber felt, and the surface treatment layer material is a nano oxide film, for example, a nano silicon dioxide film; the above-mentioned layers of materials can be purchased commercially. Among them, polyimide has excellent electrical insulation properties, enhances the electric field shielding effect, and its low thermal conductivity can effectively isolate heat transfer. Alumina fiber felt has extremely low thermal conductivity (about 0.069-0.321W / m·K), which can effectively isolate heat transfer. In addition, it can also provide structural strength, prevent brittle fracture of the outer ceramic material, and ensure the stability and durability of the entire thermoelectric shield. Alumina ceramics have excellent electrical insulation properties and can effectively shield external electric fields. The nanostructure of nanosilicon dioxide can effectively reduce the penetration path of heat and electric fields and enhance the thermal insulation and electric field shielding capabilities of the multilayer structure. The thermoelectric shield of this material not only has excellent thermal insulation and electric field shielding properties, but also achieves stability and reliability in high and low temperature environments through the innovative design of the nanostructure. The thermoelectric shield in the embodiment avoids the problem of magnetic field instability caused by heat transfer, which in turn affects the microstructure or electromagnetic response of the sample; it also avoids the influence of the electric field on the magnetic field when the electric field is applied, making the magnetic field more stable. And the miniature U-shaped electromagnet 12 is placed on both sides of the sample stage, which can apply a strong parallel magnetic field to the sample.

[0040] In a specific embodiment of the present invention, the two ends of the U-shaped structure of the thermoelectric shield 23 are sealed and contacted with the thermal conductive plate 17, thereby enclosing an area on the stage 22 for setting the four-electrode MEMS thermoelectric chip and the MEMS thermoelectric chip limiting groove 16; in addition, the thermal conductive plate 17 is also in contact with the rear end of the four-electrode MEMS thermoelectric chip and one end of the MEMS thermoelectric chip limiting groove 16, respectively. The MEMS thermoelectric chip limiting groove 16 has two, which are respectively located on both sides of the MEMS thermoelectric chip. The MEMS thermoelectric chip limiting groove 16 is made of aluminum nitride ceramic material with high thermal conductivity, good mechanical strength, low thermal expansion coefficient, 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 groove plays a role in stabilizing the chip and assisting heat conduction. The two arms of the U-shaped structure of the thermoelectric shield are located on the outside of the two limiting grooves.

[0041] In a specific embodiment of the present invention, the handle 8 is provided with an external control interface 9 at the end, the micro electromagnet 12 and the four-electrode tungsten needle 15 are electrically connected to the external control interface 9 through the PCB circuit board 19, and the external control interface 9 is connected to the external controller; the handle 8 contains a cooling pot inside, and the cooling pot structure is an internal liquid nitrogen pot and an outer shell, with a vacuum interlayer in the middle to isolate heat transfer, and the double-layer interlayer is silver-plated to reduce heat radiation heat transfer. The liquid nitrogen in the cooling pot is controlled by the inflow micro flow controller 24 and the outflow micro flow controller 25 to flow into the liquid nitrogen circulation pipe to circulate to the temperature conduction plate and contact the chip to achieve controllable temperature reduction. At the same time, the four-electrode MEMS chip has a heating function, and the combined use with the liquid nitrogen cooling system can achieve two-way temperature control from extremely low temperature (-196°C) to high temperature (1000°C), supporting temperature gradient adjustment and precise control. The inflow micro flow controller 24 and the outflow micro flow controller 25 can adopt feedback control. When the temperature needs to be lowered 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 closed.

[0042] In a specific embodiment of the present invention, the liquid nitrogen in the refrigeration kettle is circulated to the temperature conduction plate 17 through the liquid nitrogen circulation pipe 18 and contacts the chip to reduce the temperature. At the same time, a four-electrode MEMS thermoelectric chip has a heating function, and the required temperature field is accurately applied through the two-way temperature control capability; a liquid nitrogen filling port 10 is provided on the handle 8 for adding liquid nitrogen to the refrigeration kettle, and the liquid nitrogen filling port and the refrigeration kettle connecting pipe 11 are spirally pleated to reduce heat conduction.

[0043] The external controller is used to control the sample rod of the present invention by changing the electrical signal to achieve various field changes. 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 flowing into the micro flow controller 24 and out of the micro flow controller to achieve controllable temperature reduction, adjusts the size of the magnetic field (magnetic field) by adjusting the voltage applied to the micro electromagnet, and adjusts the size 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 pressure 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 two sides; the chip fixing pressure plate 13 is located at the front end of the stage and is used to fix the chip; the four-electrode tungsten needle 15, which is at least partially arranged under the chip fixing pressure 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 screws 14 on the chip fixing pressure 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] In order to achieve sensing positioning, a sensing pin 7 is provided on the hand grip 8 , and the sensing pin 7 is configured for sensing 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 realize the coordinated control of electric field, magnetic field, and temperature field (heating and cooling), and realize the comprehensive application and adjustment of multiple physical fields in one experimental system, which greatly improves the flexibility of in-situ material testing and the experimental capabilities in complex environments.

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

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

[0050] Confirm under a light microscope that the front end of the sample rod head 1 is clean and free of foreign matter;

[0051] Add liquid nitrogen into the refrigeration pot through the liquid nitrogen filling port 10;

[0052] Loosen the loosening screw 14, load the four-electrode MEMS thermoelectric chip loaded with the sample onto the stage 22 through the chip limiting groove 16, and adjust the chip position so that the four-electrode tungsten needle faces the four electrodes on the four-electrode MEMS thermoelectric chip, and finally tighten the loosening screw 14, and the sample loading is completed;

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

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

[0055] When the temperature of the sample area needs to be lowered, the liquid nitrogen in the refrigeration pot is circulated through the liquid nitrogen circulation pipe to the temperature conduction plate and contacts the chip to reduce the temperature of the sample area. On the one hand, the temperature conduction plate directly contacts the four-electrode MEMS thermoelectric chip to achieve cold transfer. On the other hand, the temperature conduction plate transfers the cold to the four-electrode MEMS thermoelectric chip through the limit groove made of high thermal conductivity material, so that the cold of the liquid nitrogen can be quickly and high-throughput transferred to the four-electrode MEMS thermoelectric chip; when the temperature of the sample area needs to be increased, the four-electrode MEMS thermoelectric chip is used for heating, so that the required temperature field is accurately applied through dual cooling and heating;

[0056] At the same time, the chip is controlled by an external controller to apply a specific electric field to measure the electrical properties of the sample under a specific temperature field, and the magnitude of the parallel magnetic field applied to the sample is controlled by controlling the voltage and current applied to the micro electromagnet 12 to measure the magnetic properties of the sample under a specific temperature field.

[0057] From the above method, it can be known that the transmission electron microscope in-situ sample rod can achieve two-way temperature control from extremely low temperature (-196°C) to high temperature (1000°C) through the combined use of MEMS thermoelectric chip and liquid nitrogen cooling system, and supports temperature gradient adjustment and precise control. This two-way regulation gives the present invention significant advantages in studying dynamic processes such as phase change and material microstructure evolution. The use of a four-electrode MEMS thermoelectric chip realizes dual control of micro-area heating and electric field application. It can accurately adjust the temperature, electric field and magnetic field of the sample at the micrometer or nanometer scale, and is particularly suitable for local property testing of nanomaterials and semiconductor materials.

[0058] The sample rod is combined with the feedback system of the external controller to realize the automatic multi-field control of temperature, magnetic field and electric field, and improve the stability of the experiment and the convenience of operation. In the present invention, a thermoelectric shielding cover is arranged on the outside of the U-shaped electromagnet, which effectively reduces the interference problem between the magnetic field and the thermal field and between the magnetic field and the electric field, and ensures the experimental accuracy and repeatability in a multi-field environment. Especially in a high temperature environment, the application of a precise magnetic field is effectively suppressed by the interference of high temperature. The sample rod is designed as a modular structure, which allows fast switching of different functional modules (such as higher strength electromagnets, chips with different temperature control ranges), greatly improving the flexibility and maintainability of the equipment and reducing the experimental cost.

Claims

1. An in-situ sample holder for a multi-field coupled transmission electron microscope, comprising a sample holder head (1), a sample holder shaft and a hand grip (8); the sample holder head (1) and the hand grip (8) are respectively arranged at two ends of the sample holder shaft; It is characterized in that The sample rod head (1) comprises 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 shielding cover (23) for wrapping the U-shaped electromagnet (12), and a temperature conducting plate (17) arranged at the rear end of the stage; wherein a MEMS thermoelectric chip limiting groove (16) and a four-electrode tungsten needle (15) are arranged at the stage, wherein the MEMS thermoelectric chip limiting groove (16) is used for positioning the MEMS thermoelectric chip, The thermoelectric shielding cover (23) is U-shaped, the U-shaped electromagnet (12) is completely placed inside the thermoelectric shielding cover (23), and both ends of the U-shaped structure of the thermoelectric shielding cover (23) are sealed. The shell wall of the thermoelectric shielding cover (23) adopts a multi-layer composite heat-insulating and electrically insulating material, which includes a polyimide inner layer, a ceramic fiber felt middle layer, an alumina ceramic outer layer and a surface treatment layer in sequence from the inside to the outside; the two arms of the U-shaped electromagnet (12) are respectively placed on both sides of the stage, so as to apply a parallel magnetic field to the sample; An external control interface (9) is provided at the end of the hand grip (8), and the U-shaped electromagnet (12) and the four-electrode tungsten needle (15) are electrically connected to the external control interface (9) via a PCB circuit board (19); The handle (8) contains a cooling pot inside, which includes an inner liquid nitrogen pot and an outer shell, with a vacuum interlayer in the middle to isolate heat transfer; The liquid nitrogen in the refrigeration pot is circulated to the temperature conducting plate (17) through a liquid nitrogen circulation pipe (18) and contacts the chip to reduce the temperature. The liquid nitrogen circulation pipe (18) is provided 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 a required temperature field through a bidirectional temperature control capability. The hand grip (8) is provided with a liquid nitrogen filling port (10) for adding liquid nitrogen to the refrigeration pot.

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

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

4. The multi-field coupled transmission electron microscope in-situ sample holder according to claim 1, characterized in that: The two ends of the U-shaped structure of the thermoelectric shielding cover (23) are sealed and contacted with the thermal conductive plate (17), thereby enclosing an area on the stage (22) for arranging the four-electrode MEMS thermoelectric chip and the MEMS thermoelectric chip limiting groove (16); the thermal conductive plate (17) is in contact with the four-electrode MEMS thermoelectric chip and the MEMS thermoelectric chip limiting groove (16) respectively; the MEMS thermoelectric chip limiting groove (16) has two, which are respectively located on both sides of the MEMS thermoelectric chip; the MEMS thermoelectric chip limiting groove (16) is made of aluminum nitride ceramic material; and the two ends of the MEMS thermoelectric chip are respectively fixedly installed in the two MEMS thermoelectric chip limiting grooves (16).

5. The multi-field coupled transmission electron microscope according to claim 1, characterized in that: The object carrier (22) comprises: Stage body; Chip limiting grooves (16) are provided on both sides of the loading platform and are lower than the height of the two sides; A chip fixing plate (13), located at the front end of the stage, and used for fixing the four-electrode MEMS thermoelectric chip; The four-electrode tungsten needle (15) is at least partially arranged 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 means of a loosening screw (14) on the chip fixing plate (13).

6. The multi-field coupled transmission electron microscope according to claim 1, characterized in that: The sample rod body comprises a first hollow rod (3) and a second hollow rod (6); The diameter of the first hollow rod (2) is smaller than that of the second hollow rod (6); one end of the first hollow rod (2) is connected to the sample rod head (1); the other end of the first hollow rod (2) is provided with a conical transition section (5); the conical transition section (5) is connected to the second hollow rod (6); a sealing ring (4) is provided between the conical transition section (5) and the second hollow rod (6); The wires led 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 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), and the guide pin (1) 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 multi-field coupled transmission electron microscope according to claim 1, characterized in that: The hand grip (8) is provided with a sensor pin (7), and the sensor pin (7) is used for sensor positioning after the sample rod head (1) is inserted into the electron lens.

9. A method for bidirectional precise temperature and electromagnetic field control of an in-situ sample holder of a transmission electron microscope according to any one of claims 1 to 8, characterized in that include: The sample is transferred to a four-electrode MEMS thermoelectric chip by dropping or using a focused ion beam instrument; Confirm under a light microscope that the front end of the sample rod head (1) is clean and free of foreign matter; Adding liquid nitrogen into the refrigeration pot through a liquid nitrogen filling port (10); Loosen the loosening screw (14), load the four-electrode MEMS thermoelectric chip loaded with the sample onto the stage (22) through the chip limiting groove (16), and adjust the chip position so that the four-electrode tungsten needle faces the four electrodes on the four-electrode MEMS thermoelectric chip, and finally tighten the loosening screw (14), and the sample loading is completed; The sample rod head (1) is directly inserted into the sample stage of the transmission electron microscope and pushed to the limit position, and the interior of the transmission electron microscope is evacuated; The sample rod head (1) is inserted into the sample stage of the transmission electron microscope, rotated and installed in place, and the external control interface (9) of the hand grip (8) is connected to the external controller through a control line; When the temperature of the area where the sample is located needs to be lowered, the liquid nitrogen in the refrigeration pot 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 conduction plate (17) to contact the chip to achieve the temperature reduction of the area where the sample is located. When the temperature of the area where the sample is located needs to be increased, a four-electrode MEMS thermoelectric chip is used for heating, thereby accurately applying the required temperature field through dual cooling and heating. At the same time, an external controller controls the four-electrode MEMS thermoelectric chip to apply a specific electric field, and the magnitude of the parallel magnetic field applied to the sample is controlled by controlling the magnitude of the voltage and current applied to the U-shaped electromagnet (12). The thermoelectric shielding cover (23) isolates the influence of the external temperature field and electric field on the U-shaped electromagnet (12), thereby avoiding the instability of the magnetic field caused by the heat transfer process, and also avoiding the influence of the electric field on the magnetic field when the electric field is applied, thereby realizing the measurement of the electrical properties and magnetic properties of the sample under a specific temperature field.

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