Transmission electron microscope in-situ test chip heated by microwave and test method

Abstract

The invention relates to a microwave heating transmission electron microscope in-situ test chip and a microwave heating transmission electron microscope in-situ test method. The test chip comprises a silicon substrate; the window area is positioned in the center of the silicon substrate and is provided with a transparent film through which electron beams can penetrate; the microwave induction area is arranged on the transparent film; the observation area is arranged on the microwave induction area and is used for placing a sample to be observed. Compared with a traditional resistance heating and laser heating mode, the method has the advantages of being high in heating rate and uniform in temperature distribution, and a new in-situ characterization means is provided for material thermodynamics research.

Description

Technical Field

[0001] The invention belongs to the technical field of transmission electron microscope (TEM) in-situ testing, and relates to a transmission electron microscope in-situ testing chip and a testing method utilizing microwave heating. Background Art

[0002] In-situ observation technology is to observe the micro-deformation, micro-damage and other processes of materials in real time, dynamically and continuously with the help of special microscopic imaging instruments during the mechanical property testing of materials at the micro / nanoscale, while tracking and collecting displacement-load information in real time. As an important characterization method in the field of materials science, the in-situ high-temperature testing technology of transmission electron microscopy (TEM) can observe the microstructural evolution, phase change behavior and dynamic reaction process of materials in high-temperature environments in real time. Traditional in-situ heating methods mainly rely on the principle of resistance heating. However, such methods have some significant problems: first, due to the limitations of the heat conduction path and contact thermal resistance, the temperature field distribution in the sample area is highly non-uniform, which seriously affects the accuracy of the experimental data; second, at high temperatures, the metal heating element is prone to interfacial reaction with the sample, resulting in distortion of the material's intrinsic properties test.

[0003] Nondestructive testing technologies for thermal deformation of materials in high-temperature environments are primarily categorized as contact and non-contact. While contact testing offers good applicability and reliability in high-temperature environments, it is limited by the fact that its measuring components require direct contact with the object being tested and cannot withstand excessively high temperatures. In recent years, non-contact laser heating technology has emerged, which can avoid the issue of contact thermal resistance. However, its energy absorption characteristics are limited by the optical properties of the material, making it prone to localized overheating in non-metallic and nanostructured materials.

[0004] Microwaves, waves with frequencies between 300MHz and 300GHz, are typically generated by a magnetron and transmitted into the heating chamber via a waveguide. Microwaves polarize the polar molecules in the material, creating dipoles. These dipoles rotate under the influence of the electric field, generating friction. This friction is then converted into heat, raising the internal temperature of the material. In this process, microwave energy is converted into thermal energy. Because microwaves can penetrate the surface of the material, the heating process occurs not only on the surface but also within the material, making it more efficient than traditional heating methods.

[0005] However, the compatibility of existing microwave excitation technology with TEM sample rods still has significant defects. Specifically, the use of conventional microwave antennas in transmission electron microscopes has structural incompatibility issues, the microwave field has severe spatial divergence, and the divergent microwave field is prone to electromagnetic interaction with the high-energy electron beam in the TEM, resulting in electron trajectory deviation or energy disturbance, and reduced image resolution.

[0006] Therefore, designing a microwave heating in-situ high-temperature testing method compatible with the transmission electron microscope system to solve key technical problems such as insufficient temperature field control accuracy and limited thermal response speed in the existing technology has become an urgent need to achieve accurate characterization of the high-temperature dynamic behavior of materials. Summary of the Invention

[0007] The purpose of the present invention is to provide a transmission electron microscope in-situ test chip and test method using microwave heating, realize the combination of microwave heating and TEM, and utilize the efficient and uniform characteristics of microwave heating to achieve rapid and uniform temperature increase of the sample, providing a new way to study the dynamic behavior of materials at high temperatures.

[0008] The purpose of the present invention can be achieved by the following technical solutions:

[0009] In one aspect, the present invention provides a transmission electron microscope in-situ test chip using microwave heating, comprising:

[0010] Silicon substrate;

[0011] a window region located in the center of the silicon substrate, having a transparent film capable of transmitting electron beams;

[0012] a microwave sensing area, which is provided on the transparent film;

[0013] and an observation area which is arranged on the microwave sensing area and is used for placing samples to be observed.

[0014] Furthermore, the transparent film is silicon nitride or silicon oxide.

[0015] Furthermore, the microwave sensing area is a coating formed by plating a material having a strong microwave absorption effect.

[0016] Furthermore, the material of the coating is nanomagnetic particles or nanocarbon tubes.

[0017] Furthermore, the observation area is one or more holes formed by etching on the microwave sensing area.

[0018] Furthermore, it also includes a temperature measurement circuit, which includes at least one current input electrode and at least one voltage measurement electrode, and the current input electrode and the voltage measurement electrode are both connected to the microwave sensing area.

[0019] In a second aspect, the present invention provides a transmission electron microscope in-situ testing method using microwave heating, which is implemented based on the test chip described in the first aspect above, and the testing method comprises the following steps:

[0020] placing the test chip on a sample rod having a microwave conduction function;

[0021] connecting an adjustable microwave source to the sample rod;

[0022] Setting the output power of the microwave source according to the required temperature so that the microwave sensing area is heated and then the heat is transferred to the sample to be observed;

[0023] After the temperature of the observed sample reaches the set target temperature, the sample temperature data is collected, the temperature change over time is recorded, and transmission electron microscopy observation is performed at the same time.

[0024] Furthermore, a microwave power amplifier is connected between the adjustable microwave source and the sample rod.

[0025] Furthermore, the output power is input according to a calibration curve based on microwave power and sample area temperature obtained in advance.

[0026] Furthermore, the calibration curve is obtained by the following method:

[0027] Before the test, the temperature of the sample area was measured using an infrared temperature measuring device, and the output power of the adjustable microwave source was adjusted to obtain the relationship curve between temperature and microwave power.

[0028] Compared to existing technologies, the microwave-heated transmission electron microscope in-situ testing chip and method of the present invention achieves a maximum heating temperature exceeding 360°C during in-situ high-temperature testing, with temperature uniformity in the microwave sensing area exceeding 13 mK. Compared to in-situ testing methods using heat conduction heating, microwave heating can achieve a more uniform temperature distribution. Furthermore, because microwave heating for in-situ high-temperature testing avoids interfacial reactions between the metal heating element and the sample, it has the advantage of preventing distortion in testing of the material's intrinsic properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a front structural diagram of the transmission electron microscope in-situ test chip of the present invention;

[0030] Figure 2 This is a partial enlarged view of the observation area of ​​the transmission electron microscope in-situ test chip of the present invention;

[0031] Figure 3 A cross-sectional view of a transmission electron microscope in-situ test chip of the present invention mounted on a sample holder;

[0032] Figure 4 Schematic diagram of the electromagnetic field distribution of the transmission electron microscope in-situ test chip during the test process of the present invention;

[0033] Figure 5 A block diagram of the components required for the transmission electron microscope in-situ testing method of the present invention;

[0034] Figure 6 The figure is a temperature control flow chart of the transmission electron microscope in-situ testing method of the present invention, wherein a is an open-loop control method based on a calibration curve, and b is a closed-loop control method based on temperature feedback;

[0035] Figure 7 The transmission electron microscope in-situ test chip and method of the present invention are tested at a microwave power density of 20W / cm 2 and 200W / cm 2 The simulation result diagram of the sample temperature changing with time;

[0036] Figure 8 is the temperature distribution diagram of the microwave sensing area;

[0037] Description of the marks in the figure:

[0038] 1 is the silicon substrate, 2 is the window area, 3 is the microwave sensing area, 4 is the observation area, 5 is the sample to be observed, 6 is the temperature measurement circuit, 61 is the current input electrode, 62 is the voltage measurement electrode, 7 is the transparent film, 8 is the circuit board, 81 is the center conductor, 82 is the grounding conductor, and 83 is the electron beam through hole. DETAILED DESCRIPTION

[0039] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0040] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0041] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0042] In the following implementation manners or examples, unless otherwise specified, functional components or structures are conventional components or conventional structures used in the art to achieve corresponding functions.

[0043] In order to solve the key technical problems of the prior art such as insufficient temperature field control accuracy and limited thermal response speed, the present invention provides a transmission electron microscope in-situ test chip using microwave heating. Figures 1 to 3 As shown, including:

[0044] Silicon substrate 1;

[0045] A window area 2 located at the center of the silicon substrate 1, having a transparent film 7 that can transmit electron beams;

[0046] a microwave sensing area 3, which is provided on the transparent film 7;

[0047] and an observation area 4 disposed on the microwave sensing area 3 and used for placing a sample 5 to be observed.

[0048] In some specific embodiments, the transparent film 7 is silicon nitride or silicon oxide.

[0049] In some specific embodiments, the microwave induction zone 3 is a coating formed by plating a material having a strong microwave absorption effect. In a more specific embodiment, the coating is made of nanomagnetic particles or carbon nanotubes.

[0050] In some specific embodiments, the observation area 4 is one or more holes formed by etching on the microwave sensing area 3 .

[0051] In some specific embodiments, please refer to Figure 1 As shown in FIG. 1 , the test chip further includes a temperature measurement circuit 6 , which includes at least one current input electrode 61 and at least one voltage measurement electrode 62 . Both the current input electrode 61 and the voltage measurement electrode 62 are connected to the microwave sensing area 3 .

[0052] In a second aspect, the present invention provides a transmission electron microscope in-situ testing method using microwave heating, which is implemented based on the test chip described in the first aspect above, and the testing method comprises the following steps:

[0053] placing the test chip on a sample rod having a microwave conduction function;

[0054] connecting an adjustable microwave source to the sample rod;

[0055] The output power of the microwave source is set according to the required temperature, so that the microwave induction area 3 is heated and the heat is transferred to the sample 5 to be observed;

[0056] After the temperature of the observed sample 5 reaches the set target temperature, the sample temperature data is collected, the temperature change over time is recorded, and transmission electron microscopy observation is performed at the same time.

[0057] In some specific embodiments, a microwave power amplifier is further connected between the adjustable microwave source and the sample holder.

[0058] In some specific embodiments, the output power is input according to a pre-acquired calibration curve based on microwave power and sample area temperature.

[0059] In a more specific embodiment, the calibration curve is obtained by the following method:

[0060] Before the test, the temperature of the sample area was measured using an infrared temperature measuring device, and the output power of the adjustable microwave source was adjusted to obtain the relationship curve between temperature and microwave power.

[0061] The above embodiments may be implemented individually or in any combination of two or more.

[0062] The above implementation is described in more detail below with reference to specific examples.

[0063] Example 1:

[0064] Figures 1 to 3 This is a structural diagram of a transmission electron microscope in-situ test chip using microwave heating, provided in this embodiment. The chip comprises a silicon substrate 1, a window area 2, a microwave sensing area 3, and an observation area 4. The silicon substrate 1 is polygonal, such as a regular octagon. Because the mounting slot on a typical sample holder is circular with a diameter of 3 mm, it is easier to cut the silicon wafer in a straight line. The window area 2, located at the center of the silicon substrate 1, is used to transmit the electron beam and is shaped like a 0.1 mm x 0.1 mm square. It is fabricated by etching. A transparent film 7, such as a 10-100 nm thick silicon nitride layer, is located on the window area 2. The microwave sensing area 3, located on the transparent film 7, is made of a material with a strong microwave absorption effect, such as a nanomagnetic particle composite material or carbon nanotubes. Above the microwave sensing area 3 is an observation area 4 for placing a sample 5 to be observed. The observation area 4 consists of one or more holes etched into the microwave sensing area 3. Figure 2 The cases where the observation area 4 is a smaller hole of 5×5 (left picture) or a larger hole (right picture) are shown.

[0065] The chip also features a temperature measurement circuit 6, connected to the microwave sensing zone 3. The circuit 61 represents the current input electrode, and the circuit 62 represents the voltage measurement electrode. Using a four-electrode connection, a small current is input to the current input electrode 61, and the voltage at the voltage measurement electrode 62 is read to determine the resistance of the microwave sensing zone 3. The relationship between the measured resistance and temperature can be used to measure the average temperature of the microwave sensing zone 3.

[0066] Figure 3 This is the cross-sectional structure of the chip when it is mounted on the sample rod. The sample rod head has a circuit board 8 with microwave transmission function. The circuit board 8 uses a coplanar waveguide structure to transmit microwaves from 0 to 20 GHz to the sample area. The circuit board 8 has a center conductor 81, a ground conductor 82 and an electron beam through hole 83. It should be pointed out here that how to arrange the center conductor 81 and other structures on the circuit board 8 to form a coplanar waveguide structure is a conventional design in the field and is not the innovation of the present invention. It will not be repeated here. In addition, the electromagnetic field established between the center conductor 81 and the ground conductor 82 of the circuit board 8 is as follows: Figure 4 As shown, the microwave power density of the microwave induction zone 3 can reach 200W / cm 2 In order to ensure that the sample 5 to be observed can be affected by the electromagnetic field generated by the circuit board 8 during the test, a chip mounting slot is provided on the circuit board 8 , and its position satisfies that the sample 5 to be observed is located on the extension line of the electron beam through hole 83 .

[0067] Figure 5 and Figure 6 A method for testing using the transmission electron microscope in-situ test chip of the present invention:

[0068] 1. Install the above chip on a sample holder with microwave conduction function, connect the microwave input end to the microwave power amplifier and microwave source, connect the temperature measurement circuit end to the temperature measurement unit, and connect the control unit to the temperature measurement unit and microwave source.

[0069] 2. The control unit sets an initial microwave power according to the set temperature. After the microwave induction area is heated, the resistance changes, and the temperature measured by the temperature measuring unit is fed back to the control unit.

[0070] 3. The control unit sets a new microwave power according to the deviation between the current temperature and the set temperature until the temperature reaches within the allowable error range near the set temperature.

[0071] 4. Real-time recording of temperature and time data while simultaneously performing transmission electron microscopy observations, such as obtaining high-resolution electron microscopic images, electron diffraction patterns, differential phase contrast images, and electron energy loss spectra. This allows for studying changes in the sample's crystal structure or surface structure after microwave heating.

[0072] Figure 6A method for temperature control using a calibration curve is also given. The first step is to calibrate the chip, including: setting the microwave power, then using infrared equipment to perform infrared temperature measurement, gradually increasing the microwave power and measuring the corresponding temperature, repeating the above process to obtain a calibration curve. The second step is in-situ testing, including: setting the temperature, calculating the power requirement corresponding to the set temperature based on the above calibration curve, then setting the microwave power, and recording the data after the temperature stabilizes. It should be pointed out that Figure 6 The method described in Figure (b) differs from the "closed-loop control" (also known as feedback control) method using temperature feedback described in steps 1-4 of the previous method. This method uses "open-loop control" (also known as feedforward control), meaning that the microwave power is not set based on the temperature read by the temperature measurement circuit. Instead, a pre-obtained "microwave power-temperature calibration curve" is used to set the desired power. This may be applicable in the following scenarios: a. Temperature measurement anomalies caused by damage to the temperature measurement circuit or other reasons; b. The microwave source lacks programmable control and must be set manually; c. Large temperature fluctuations occur in closed-loop control due to feedback delays.

[0073] The simulation results of microwave induction heating process using finite element method are as follows Figure 7 When the material of the microwave induction zone is NiO-Ni composite material and the size is 0.1mm*0.1mm*5um, the microwave frequency is 18GHz and the power density is 20W / cm 2 When the power density is 20W / cm 2 The temperature can rise to above 360℃ within 1s, and the fastest heating rate can reach 1200℃ / s. The temperature distribution in the microwave induction zone is as follows: Figure 8 , and its maximum temperature deviation is less than 13mK. Therefore, using microwave heating to heat the sample to be observed for in-situ high-temperature testing can provide high heating efficiency and higher temperature uniformity.

[0074] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A transmission electron microscope in-situ test chip using microwave heating, characterized in that: include: Silicon substrate; a window region located in the center of the silicon substrate, having a transparent film capable of transmitting electron beams; a microwave sensing area, which is provided on the transparent film; and an observation area which is arranged on the microwave sensing area and is used for placing samples to be observed.

2. The transmission electron microscope in-situ test chip using microwave heating according to claim 1, characterized in that: The transparent film is silicon nitride or silicon oxide.

3. The transmission electron microscope in-situ test chip using microwave heating according to claim 1, characterized in that: The microwave induction zone is a coating formed by plating a material having a strong microwave absorption effect.

4. The transmission electron microscope in-situ test chip using microwave heating according to claim 3, characterized in that: The material of the coating is nano magnetic particles or nano carbon tubes.

5. The transmission electron microscope in-situ test chip using microwave heating according to claim 1, characterized in that: The observation area is one or more holes formed by etching on the microwave sensing area.

6. The transmission electron microscope in-situ test chip using microwave heating according to claim 1, characterized in that: It also includes a temperature measurement circuit, which includes at least one current input electrode and at least one voltage measurement electrode. Both the current input electrode and the voltage measurement electrode are connected to the microwave sensing area.

7. A transmission electron microscope in-situ testing method using microwave heating, which is implemented based on the test chip according to any one of claims 1 to 6, characterized in that: The test method comprises the following steps: placing the test chip on a sample rod having a microwave conduction function; connecting an adjustable microwave source to the sample rod; Setting the output power of the microwave source according to the required temperature so that the microwave sensing area is heated and then the heat is transferred to the sample to be observed; After the temperature of the observed sample reaches the set target temperature, the sample temperature data is collected, the temperature change over time is recorded, and transmission electron microscopy observation is performed at the same time.

8. The transmission electron microscope in-situ testing method using microwave heating according to claim 7, characterized in that: A microwave power amplifier is also connected between the adjustable microwave source and the sample rod.

9. The transmission electron microscope in-situ testing method using microwave heating according to claim 7, characterized in that: The output power is input according to a calibration curve based on microwave power and sample area temperature obtained in advance.

10. The transmission electron microscope in-situ testing method using microwave heating according to claim 9, characterized in that: The calibration curve was obtained by the following method: Before the test, the temperature of the sample area was measured using an infrared temperature measuring device, and the output power of the adjustable microwave source was adjusted to obtain the relationship curve between temperature and microwave power.

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