In-situ SEM thermogravimetric system based on MEMS cantilever beam and application thereof
By using an in-situ SEM thermogravimetric system based on a MEMS cantilever beam, the problems of high-temperature imaging noise and insufficient growth kinetics research have been solved, enabling efficient and accurate analysis of material microstructure and properties, and providing simultaneous capture of multi-dimensional information.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-26
- Publication Date
- 2026-04-03
AI Technical Summary
Existing SEM in-situ stages suffer from background noise affecting image clarity and data repeatability during high-temperature imaging, and lack research on the dynamics of growth and weightlessness. Conventional hot stages are large in size and consume a lot of power, making it difficult to achieve efficient and accurate analysis of material microstructure and properties.
An in-situ SEM thermogravimetric system based on a MEMS cantilever beam was adopted, which integrates temperature control and mass change monitoring. The sample mass was monitored by the change of the resonant frequency of the MEMS cantilever beam, and the morphology was observed by SEM scanning electron microscopy, so as to realize the synchronous capture of multi-dimensional information of the material at high temperature.
It improves image clarity at high temperatures, reduces the system's impact on the SEM detector, enables precise monitoring of minute mass changes, provides simultaneous observation of multi-dimensional information, and enhances the efficiency and accuracy of material analysis.
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Figure CN121784053A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of in-situ electron microscopy technology, and in particular to an in-situ SEM thermogravimetric system based on a MEMS cantilever beam and its usage method. Background Technology
[0002] Scanning electron microscopy (SEM) enables microstructural characterization of materials across scales from nanometers to millimeters. When coupled with energy-dispersive X-ray spectroscopy (EDS), it can obtain microscopic information including grain size, elemental distribution, and interface characteristics, making it one of the most common characterization methods in materials science, biology, and microelectronics. Traditional material characterization employs ex-situ (non-in-situ) methods, which reduce the influence of samples on experimental equipment. However, conventional non-in-situ analysis lacks the influence of sample preparation processes and service conditions (coupling effects of heat, force, and time) on the microstructure, and thus lacks dynamic information on the real-time correlation between the material's microstructure and properties. Furthermore, to obtain temperature-dependent thermal or growth characteristics of nanomaterials, conventional non-in-situ analysis methods require the preparation of a large number of samples (at different temperatures and times), reverse sampling, observation, and data processing to obtain detailed growth thermodynamic and kinetic parameters.
[0003] Developing miniature in-situ stages, leveraging the superior nanoscale resolution of SEM, enables in-situ observation of the microstructure of materials during dynamic processes. This not only overcomes the time-consuming and inefficient problems of conventional non-in-situ analysis methods but also captures microstructural information of materials or devices under service conditions, providing a basis for evaluating and improving performance models of various microstructures and microscales of materials. In recent years, miniaturized in-situ mechanical property testing sample stages have developed rapidly. By assembling additional devices with functions such as tension, compression, bending, shearing, indentation, and heating within a scanning electron microscope, parameters such as plastic deformation, elastic modulus, and hardness of materials can be analyzed. This allows for the proposing of deformation and crack mechanisms under a microscopic microscope, deepening the understanding of the intrinsic relationship between the structure and mechanical properties of materials. To better understand the mechanical properties of materials in high-temperature service environments, various SEM in-situ heated sample stages have been developed. The Bruker Hysitron PI series instruments offer two heating options, with temperatures up to 1000°C. In-situ heating up to 400°C is achieved using a resistive MEMS heater, activating various deformation mechanisms for nanomechanical research, such as the brittle-ductile transition in glass and polymers. A water circulation module on the sample heating stage and sensor minimizes system temperature drift. The biggest challenge is that a large number of thermionic electrons during high-temperature imaging can cause a "flooding effect" on the secondary electron topography image, generating significant noise background during acquisition and severely reducing secondary electron resolution and image contrast. Furthermore, at higher temperatures, both the in-situ heating stage and the tested sample generate a large amount of infrared light, reducing the signal-to-noise ratio of the secondary electron probe 11.
[0004] Bai et al. used in-situ electron microscopy to observe the structural changes of cerium oxide at the microscopic scale, pointing out that the reversible reduction reaction in cerium oxide was driven by the electric field rather than the increased temperature. Huang et al. were the first to use in-situ electron microscopy to study the dynamic process of lithium charging of tin dioxide nanowires under charging conditions. This provided a direct understanding of the volume expansion, plastic deformation, and destructive consequences of lithium charging, offering a powerful tool for real-time observation and analysis of the complex reactions of batteries under operating conditions and for exploring ways to improve battery performance. In-situ heated electron microscopy is also frequently used to study the evolution of nanocrystal morphology, grain fusion, and wetting. Sacher et al. used in-situ electron microscopy to observe the fusion process of gold nanoparticles in their study of diffusion and fusion on the surface of metal nanoparticles.
[0005] However, most existing SEM in-situ stages are (bulk) hot stages or thermo-dynamic stages, which have the following shortcomings: 1. Background noise affects image clarity and data repeatability. Conventional (bulk) high-temperature hot stages consume a lot of power, and the heat radiated from them degrades the electron beam focusing effect of the SEM objective (electromagnetic lens) and also worsens the imaging effect of the secondary electron detector, making it difficult to acquire high-resolution images in static environments. Modern detectors typically have higher quantum detection efficiency and camera frame rates, which significantly shortens image acquisition time, improving the time resolution of phase transition processes and greatly reducing the impact of data quality degradation caused by sample drift in in-situ environments. On the other hand, with the development of Micro Electro-Mechanical Systems (MEMS), miniaturized MEMS sample stages have significant advantages such as small size, low power consumption, and minimal impact on the internal detectors of the SEM. Through proper selection and design of MEMS, the data impact caused by changes in the external environment can be minimized.
[0006] 2. Mass parameters are often overlooked, and kinetic studies of growth and weight loss are lacking. With the help of various specially designed in-situ platforms, researchers can conduct physical experiments, including electrical, mechanical, luminescent, and melting experiments, as well as chemical experiments, such as phase transitions, growth, dissolution, oxidation, reduction, and catalysis, during electron microscopy observation. Most studies focus on the effects of various growth parameters, such as temperature, atmospheric pressure, and defects, on the composition, length, diameter, and migration of nanowires and alloy particles. Morphological changes often reflect changes in the chemical potential of reactants in the catalyst and the energy states of the gas-liquid-solid three-phase system. However, physical parameters such as sample mass are often neglected. For example, under specific oxygen partial pressure atmospheres, various metals can generate stress between the surface oxide layer and the underlying metal layer. Simultaneously, driven by Fick's diffusion law, nanowires migrate directionally along specific crystal directions. Conventional morphological observations struggle to capture the weight gain and growth kinetic parameters during the oxidation process. Summary of the Invention
[0007] To overcome the shortcomings of existing in-situ electron microscopy technology, such as unstable imaging and lack of dynamic research on growth and weight loss, this invention proposes an in-situ SEM thermogravimetric system based on a MEMS cantilever beam. This system integrates in-situ temperature control and in-situ mass change, enabling the in-situ growth morphology evolution of materials, device state at operating temperature, device failure mechanism, and metastable state capture.
[0008] The present invention proposes an in-situ SEM thermogravimetric system based on a MEMS cantilever beam, comprising a SEM scanning electron microscope, a MEMS cantilever beam, a weighing module, a temperature control module, and a host computer for load measurement and control software; the MEMS cantilever beam integrates a sample loading area, a micro heater, a driver, and a resonant detector. During observation, the MEMS cantilever beam is placed in the vacuum chamber of the SEM (Scanning Electron Microscope), and the sample loading area is located in the scanning area of the SEM. In the working state of the MEMS cantilever beam, the actuator drives the MEMS cantilever beam to vibrate, the resonance detector is used to detect the resonant frequency of the MEMS cantilever beam, and the micro heater is used to heat the sample loading area. The micro heater is connected to the host computer via a temperature control module, and adjusts the temperature according to the measurement and control commands issued by the host computer. The driver and the resonant detector are connected to the host computer via a weighing module. The driver drives the MEMS cantilever beam to vibrate, and the weighing module obtains the change in the sample mass in the sample loading area by analyzing the resonant frequency detected by the resonant detector based on the relationship between the resonant frequency and the mass of the MEMS cantilever beam, and uploads the result to the host computer. The host computer synchronously records changes in sample temperature and mass, as well as morphological information from SEM scanning electron microscopy.
[0009] Preferably, the weighing module and the temperature control module are located outside the SEM (Scanning Electron Microscope). The SEM is equipped with a vacuum-tight electrode that connects the weighing module and the temperature control module. The MEMS cantilever beam is detachably connected to the SEM. When the MEMS cantilever beam is installed in the cavity of the SEM, it connects the weighing module and the temperature control module through the vacuum-tight electrode.
[0010] Preferably, the actuator and resonant detector are located on the side of the microheater away from the sample loading area, and a hollow structure is provided on the side of the microheater on the MEMS cantilever beam near the actuator and resonant detector.
[0011] Preferably, the sample loading area is located at the cantilever end of the MEMS cantilever beam.
[0012] Preferably, the microheater is made of Mo, W or Pt and is fabricated using photolithography and sputtering processes.
[0013] Preferably, the SEM (Scanning Electron Microscope) is a tungsten filament lamp-based SEM, a benchtop SEM, or a field emission high-resolution SEM; the vacuum level of the SEM during operation is 10. -3 -10 -4 Pa.
[0014] This invention proposes a metal analysis method for obtaining the dewetting of metal thin films and the evaporation rate of dewetting micro / nano particles at different temperatures. The steps are as follows: Step 1: Clean the MEMS cantilever beam, cover the cantilever beam with a stainless steel mask, leaving only a hole above the sample loading area of the cantilever beam, then deposit a metal film of a specified thickness in the sample loading area, and then put the MEMS cantilever beam into the sample stage in the SEM scanning electron microscope cavity. Step 2: Close the SEM chamber door. When the vacuum level of the SEM chamber drops to 10... -3 -10 -4When Pa is reached, turn on the electron gun, adjust the position and height of the sample area, and adjust the electron beam collimation, astigmatism, magnification and scanning parameters of the SEM. Step 3: Start the measurement and control software on the host computer, use the measurement and control program to control the power of the micro heater to regulate the temperature of the sample loading area, the weighing module monitors the change of sample mass at different temperatures by analyzing the resonant frequency of the MEMS cantilever beam, and the SEM scanning electron microscope records the evolution of sample morphology simultaneously. Step 4: Repeat steps 1-3 and record the morphological evolution and mass changes of the sample under test at different temperatures; Step 5: Comprehensively analyze the evolution data of mass and morphology of metal films of different thicknesses over time at different temperatures, and analyze the dewetting conditions and evaporation rate of metal films of different thicknesses.
[0015] Preferably, the metal is one of the transition metals Ni, Cu, and Al, or one of the noble metals Au, Pt, Ag, and Pd, or an alloy composed of two or more metals.
[0016] This invention proposes a metal analysis method for analyzing nanowires grown by thermal oxidation of transition metals, the steps of which are as follows: Step 1: After cleaning the MEMS cantilever beam, drop-coat the metal powder to be tested onto the sample loading area, and after drying, mount the MEMS cantilever beam into the SEM (Scanning Electron Microscope). Step 2: Close the chamber door of the SEM (Scanning Electron Microscope), evacuate the vacuum, adjust the field of view, adjust the position and height of the sample area, and adjust the electron beam collimation, astigmatism, magnification, and scanning parameters of the SEM. Step 3: Start the measurement and control software through the host computer, control the temperature of the sample loading area at the set constant temperature and keep it at the set temperature for a set time, monitor the mass change of the metal powder to be tested through the weighing module, and record the morphological evolution of the sample by SEM scanning electron microscope, that is, the length of thermally oxidized nanowires on micron particles. Step 4: Repeat steps 1-3 above to obtain the kinetic parameters of the thermal oxidation growth of nanowires from the metal powder under test at different temperatures, and analyze the correlation between the nanowire growth rate and the weight gain to characterize the thermodynamic and kinetic properties of thermal oxidation growth.
[0017] Preferably, the transition metal is one of W, Ti, and Fe, and the metal powder particle size is 1-50 µm; in step 3, the nanowires grown by W, Ti, and Fe under a set constant temperature and oxygen partial pressure are W, Ti, and Fe, respectively. 3-x Nanowires, TiO2 nanowires and Fe2O3 nanowires.
[0018] The advantages of this invention are: (1) Conventional "bulk" hot stages are large in size, consume a lot of power, and require the design of an insulation layer and water cooling in addition to the insulation layer to reduce the influence of the radiative thermal field on the SEM objective and secondary electron probe. The vacuum chamber has extremely high requirements for the water cooling system and joints inside the chamber. Even slight leakage or water seepage can cause incalculable damage to the SEM working in high vacuum. The present invention proposes an in-situ SEM thermogravimetric system based on a MEMS cantilever beam. The MEMS cantilever beam is used as the substrate, and a micro heater is introduced for local temperature control. The micro heater is small in size and consumes little power. It has a hollow structure with the substrate, so that the high temperature zone is limited to the sample loading area. No additional water cooling system is required. The area outside the sample loading area does not get hot. It has little impact on the SEM objective and secondary electron imaging probe, which is conducive to obtaining high-definition microscopic images under high temperature conditions.
[0019] (2) Compared with existing thermogravimetric analysis (TGA), the lower limit of mass detection of precision balance is only in µg. This invention uses a silicon-based MEMS cantilever beam to detect changes in sample mass by changing the resonant frequency. It can monitor mass changes in the pg range. The detection limit is about 6 orders of magnitude lower than that of existing laboratory TGA systems. It can accurately monitor the mass changes of trace samples during evaporation, decomposition and reaction processes.
[0020] (3) This invention can control the sample temperature through a microheater and simultaneously monitor minute changes in sample mass in real time through the frequency shift of the cantilever beam resonant frequency; finally, a measurement and control system and host computer are developed to realize real-time feedback and linkage of temperature and mass data, and combined with SEM image acquisition, to complete the development of a multifunctional in-situ SEM sample stage. This invention can simultaneously observe multi-dimensional information of material "temperature-morphology-mass", providing technical support for in-depth exploration of the thermodynamics and kinetics of nanomaterial growth.
[0021] (4) The metal analysis method proposed in this invention fully explores the correlation between the thermal oxidation growth and weight gain of oxide nanowires in the in-situ SEM system, and the influence of the morphological evolution and weight loss of the thermodynamic kinetic parameters of semiconductor device failure / vacuum in-situ evaporation of alloy nanoparticles. It can also simultaneously monitor the changes in mass and morphology of materials / substances during heating or cooling under a certain vacuum degree. It does not require batch preparation of samples under different conditions and repeated SEM sample loading and observation, which can accelerate the progress of material research and development. In addition, it can capture important information that cannot be captured by conventional non-in-situ analysis, and improve the level of material and device analysis and characterization. Attached Figure Description
[0022] Figure 1 This is a schematic diagram of the in-situ SEM thermogravimetric system based on a MEMS cantilever beam proposed in this invention. Figure 2 This is a flowchart of a metal analysis method using an in-situ SEM thermogravimetric system based on a MEMS cantilever beam. Figure 3This is a flowchart of another metal analysis method using an in-situ SEM thermogravimetric system based on a MEMS cantilever beam.
[0023] Illustration: 1-SEM (Scanning Electron Microscope); 11-Secondary Electron Probe; 2-MEMS Cantilever Beam; 21-Micro Heater; 22-Actuator; 23-Resonant Detector; 24-Sample Loading Area; 25-Hollow Structure; 3-Vacuum-Tight Electrode. Detailed Implementation
[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0025] like Figure 1 As shown, this embodiment proposes an in-situ SEM (Scanning Electron Microscope) thermogravimetric system based on a MEMS (Micro-Electro-Mechanical Systems) cantilever beam, comprising an SEM scanning electron microscope 1, a MEMS cantilever beam 2, a weighing module, a temperature control module, and a host computer. The host computer is connected to both the weighing module and the temperature control module.
[0026] MEMS cantilever beams are mounted on the sample stage of a scanning electron microscope (SEM). They can be fixed or detachable.
[0027] The MEMS cantilever beam integrates a microheater 21, an actuator 22, and a resonant detector 23. The microheater is connected to a temperature control module and adjusts the temperature according to the signal transmitted by the temperature control module. The microheater is used to heat the sample loading area 24 of the cantilever beam to control the temperature of the sample to be tested.
[0028] The driver connects to the host computer and drives the MEMS cantilever beam to vibrate according to the host computer's instructions.
[0029] The MEMS cantilever beam can be specifically designed using a silicon-based MEMS structure. After the actuator is powered on via the weighing module, it generates an AC heating voltage to heat the MEMS cantilever beam. The silicon substrates expand to varying degrees upon heating, resulting in relative displacement and causing the entire MEMS cantilever beam to vibrate. The frequency of the AC heating voltage tends towards the resonant frequency of the MEMS cantilever beam, thereby increasing the vibration amplitude. In practice, the actuator can be selected based on the resonant frequency of the MEMS cantilever beam to ensure that the frequency of the AC heating voltage approaches, or even matches, the resonant frequency of the MEMS cantilever beam. A resonant detector is used to detect the vibration signal (specifically, the amplitude signal) of the MEMS cantilever beam. A Wheatstone bridge can be used to determine the vibration amplitude of the MEMS cantilever beam through the piezoresistive effect of the single-crystal silicon substrate.
[0030] The weighing module is connected to the resonant detector. The weighing module is used to analyze the vibration signal of the MEMS cantilever beam fed back by the resonant detector to obtain the mass change. Thus, when the sample is loaded in the sample-bearing area, the mass change fed back by the vibration signal is the mass change of the sample.
[0031] In practical implementation, a vacuum-tight electrode 3 can be installed on the SEM (Scanning Electron Microscope) to connect the microheater, driver, and resonant detector located inside the SEM cavity with the weighing module and temperature control module located outside the SEM, thus avoiding the influence of test signal lines on the sealed testing environment of the SEM. The vacuum-tight electrode can be connected to the SEM via a flange, and the flange leakage rate of the vacuum-tight electrode can be set to be less than 1×10⁻⁶. -10 Pa·cm 3 / s, to ensure the airtightness of the SEM scanning electron microscope cavity.
[0032] The host computer is connected to both the weighing module and the temperature control module to issue test commands. Specifically, the host computer can issue measurement and control commands to put the driver and resonant detector into working state; it can also issue test temperature commands to instruct the temperature control module to control the micro heater to adjust the specific temperature value (e.g., 30-1100 degrees Celsius) and control the heating and cooling rate.
[0033] The microheater is used to regulate the testing temperature of the sample. Depending on the sample, the maximum temperature may need to reach 800-1100 degrees Celsius. The microheater can be made of Mo, W, or Pt. The temperature control module can control the chip temperature through the drive power to achieve a temperature range of room temperature to 1100 degrees Celsius in the sample area.
[0034] In practice, the driver and resonant detector can be located on the side of the micro heater away from the sample loading area, and a hollow structure 25 can be set between the driver and resonant detector and the micro heater for heat insulation to avoid the driver and resonant detector being affected by the high temperature of the micro heater.
[0035] This embodiment monitors minute changes in sample mass by monitoring the shift in the resonant frequency of the MEMS cantilever beam. The sample loading area is positioned at the cantilever end of the MEMS cantilever beam. As can be seen from the lever principle, this makes the MEMS cantilever beam more sensitive to sample mass; changes in sample mass are more likely to cause changes in the amplitude of the MEMS cantilever beam.
[0036] In this system, the test temperature is controlled by a microheater, the morphological changes of the sample in the sample-carrying area are observed by a scanning electron microscope (SEM), and the mass changes of the sample in the sample-carrying area are observed by a resonant detector and a weighing module. The SEM can be a small (or even benchtop) scanning electron microscope based on a tungsten filament lamp, or a high-resolution scanning electron microscope based on field emission.
[0037] Using the aforementioned in-situ SEM thermogravimetric system based on a MEMS cantilever beam, the dewetting of noble metal nanofilms can be observed in situ (the film shrinks into discrete nanoparticles as the temperature rises, thus reducing the system's free energy), or the particles in a vacuum (SEM chamber vacuum level 10). -4 The system can obtain the evaporation rate at different temperatures under conditions of -1 Pa, and can also obtain the influence of nanoscale effect on the evaporation rate. At the same time, the system can efficiently obtain the growth thermodynamic and kinetic parameters of oxide nanowires corresponding to the thermal oxidation growth of some transition metals (such as W, Ti, etc.) under low oxygen partial pressure.
[0038] Reference Figure 2 When using the above-mentioned in-situ SEM thermogravimetric system based on MEMS cantilever beams to analyze the dewetting and evaporation rates of noble metal thin films, the steps are as follows: Step S1, Substrate cleaning: Perform oxygen plasma cleaning on the MEMS cantilever beam, with a power of 30-100W, an oxygen flow rate of 5-30sccm, and a cleaning time of 0.5-5min. Step S2, precious metal film evaporation: The MEMS cantilever beam is placed in a thermal evaporation, electron beam evaporation, or magnetron sputtering cavity, and 5-20nm of Au, Pt, or Ag is deposited on the chip sample area; Step S3, SEM observation settings: Install the MEMS cantilever beam from step S2 into the cavity of the SEM scanning electron microscope, evacuate the vacuum until the electron gun can be turned on, select the field of view, and adjust the electron beam collimation, astigmatism, and focusing until the morphology of the noble metal film can be observed at 5000 to 50000x magnification. Step S4, In-situ Thermogravimetric Analysis and Morphology Synchronous Observation: Open the MEMS cantilever beam measurement and control program on the host computer, and start the weighing module and temperature control module; the temperature control module controls the micro heater to work according to the measurement and control program, for example, controlling the temperature to rise from 200 degrees Celsius to 1000 degrees Celsius in 50-degree Celsius increments, and holding it at the set temperature for 5 minutes; the weighing module monitors the change in sample mass at different temperatures by analyzing the vibration signal of the microcomputer cantilever arm fed back by the resonant detector; the morphological evolution of the sample is recorded using the manual scanning or continuous automatic scanning function of the SEM scanning electron microscope at a certain time step (10s-10min); Step S5, Data Analysis: Retrieve sample temperature, mass change, and evolution (including particle size distribution) data at different times to analyze the dewetting conditions of noble metal films, the migration and merging of dewetting nanoparticles at higher temperatures (Ostwald ripening), and simultaneously obtain the evaporation rate of nanoparticles of different sizes under higher temperature (vacuum) conditions.
[0039] Reference Figure 3 When using the above-mentioned in-situ SEM thermogravimetric system based on MEMS cantilever beams to analyze the thermal oxidation growth of transition metal nanowires, the steps are as follows: Step 11, Substrate cleaning: Perform oxygen plasma cleaning on the MEMS cantilever beam, with a power of 30-100W, an oxygen flow rate of 5-30sccm, and a cleaning time of 0.5-5min; Step 12, Transition metal powder loading: High-purity W (or Ti) powder with a specific particle size (0.1-20µm) is dispersed in deionized water and ultrasonically treated to form a suspension. A small amount of powder is dipped into the tip of a wolf hair brush and then transferred to the sample loading area of the MEMS cantilever beam under a microscope. Step 13, SEM observation settings: Install the MEMS cantilever beam carrying the sample into the cavity of the SEM scanning electron microscope, evacuate the vacuum until the electron gun can be turned on, select the field of view, and adjust the electron beam collimation, astigmatism, and focusing until the morphology of the noble metal film can be observed at 5000 to 50000x magnification. Step 14: In-situ thermogravimetric and morphology synchronous observation: Open the measurement and control program of the MEMS cantilever beam on the host computer, control the temperature of the sample loading area at a constant temperature (e.g., 400 degrees Celsius), keep it at the temperature for 0.1-5 hours, monitor the increase in sample mass, and record the morphological evolution of the sample by manual scanning or continuous automatic scanning with SEM at a certain time step (10s-10min). Step 15: Repeat steps 13 and 14, and change the temperature of step 14 after changing the sample to obtain the kinetic parameters (such as nanowire growth rate) of the transition metal powder for thermal oxidation growth of nanowires at different temperatures. Step 16, Data Analysis: Extract the mass increase of metal powder, diameter and length of thermally oxidized nanowires at different temperatures and times to obtain the correlation between nanowire growth rate and weight gain (oxidation rate), and analyze the thermodynamic and kinetic characteristics of thermal oxidation growth.
[0040] Of course, those skilled in the art will recognize that the present invention is not limited to the details of the exemplary embodiments described above, but also includes the same or similar structures that can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.
[0041] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.
[0042] The technologies, shapes, and structures not described in detail in this invention are all known technologies.
Claims
1. An in-situ SEM thermogravimetric analysis system based on a MEMS cantilever beam, characterized in that, It includes a scanning electron microscope (SEM), a MEMS cantilever beam, a weighing module, a temperature control module, and a host computer for load measurement and control software; the MEMS cantilever beam integrates a sample loading area, a micro heater, an actuator, and a resonant detector. During observation, the MEMS cantilever beam is placed in the vacuum chamber of the SEM (Scanning Electron Microscope), and the sample loading area is located in the scanning area of the SEM. In the working state of the MEMS cantilever beam, the actuator drives the MEMS cantilever beam to vibrate, the resonance detector is used to detect the resonant frequency of the MEMS cantilever beam, and the micro heater is used to heat the sample loading area. The micro heater is connected to the host computer via a temperature control module, and adjusts the temperature according to the measurement and control commands issued by the host computer. The driver and the resonant detector are connected to the host computer via a weighing module. The driver drives the MEMS cantilever beam to vibrate, and the weighing module obtains the change in the sample mass in the sample loading area by analyzing the resonant frequency detected by the resonant detector based on the relationship between the resonant frequency and the mass of the MEMS cantilever beam, and uploads the result to the host computer. The host computer synchronously records changes in sample temperature and mass, as well as morphological information from SEM scanning electron microscopy.
2. The in-situ SEM thermogravimetric analysis system based on a MEMS cantilever beam as described in claim 1, characterized in that, The weighing module and temperature control module are located outside the SEM (Scanning Electron Microscope). The SEM is equipped with vacuum-tight electrodes that connect the weighing module and temperature control module. The MEMS cantilever beam is detachably connected to the SEM. When the MEMS cantilever beam is installed in the cavity of the SEM, it connects the weighing module and temperature control module through the vacuum-tight electrodes.
3. The in-situ SEM thermogravimetric analysis system based on a MEMS cantilever beam as described in claim 1, characterized in that, The actuator and resonant detector are located on the side of the microheater away from the sample loading area, and a hollow structure is set on the side of the microheater near the actuator and resonant detector on the MEMS cantilever beam.
4. The in-situ SEM thermogravimetric analysis system based on a MEMS cantilever beam as described in claim 3, characterized in that, The sample loading area is located at the cantilever end of the MEMS cantilever beam.
5. The in-situ SEM thermogravimetric analysis system based on a MEMS cantilever beam as described in claim 1, characterized in that, The microheaters are made of Mo, W, or Pt and are fabricated using photolithography and sputtering processes.
6. The in-situ SEM thermogravimetric analysis system based on a MEMS cantilever beam as described in claim 1, characterized in that, The scanning electron microscope (SEM) can be a tungsten filament lamp-based SEM, a benchtop SEM, or a field emission high-resolution SEM; the vacuum level during SEM operation is 10. -3 -10 -4 Pa.
7. A metal analysis method using an in-situ SEM thermogravimetric system based on a MEMS cantilever beam as described in any one of claims 1-6, characterized in that, The steps for obtaining the dewetting rate of metal thin films and the evaporation rate of dewetting micro / nano particles at different temperatures are as follows: Step 1: Clean the MEMS cantilever beam, cover the cantilever beam with a stainless steel mask, leaving only a hole above the sample loading area of the cantilever beam, then deposit a metal film of a specified thickness in the sample loading area, and then put the MEMS cantilever beam into the sample stage in the SEM scanning electron microscope cavity. Step 2: Close the SEM chamber door. When the vacuum level of the SEM chamber drops to 10... -3 -10 -4 When Pa is reached, turn on the electron gun, adjust the position and height of the sample area, and adjust the electron beam collimation, astigmatism, magnification and scanning parameters of the SEM. Step 3: Start the measurement and control software on the host computer, use the measurement and control program to control the power of the micro heater to regulate the temperature of the sample loading area, the weighing module monitors the change of sample mass at different temperatures by analyzing the resonant frequency of the MEMS cantilever beam, and the SEM scanning electron microscope records the evolution of sample morphology simultaneously. Step 4: Repeat steps 1-3 and record the morphological evolution and mass changes of the sample under test at different temperatures; Step 5: Comprehensively analyze the evolution data of mass and morphology of metal films of different thicknesses over time at different temperatures, and analyze the dewetting conditions and evaporation rate of metal films of different thicknesses.
8. The precious metal analysis method as described in claim 7, characterized in that, The metal is one of the transition metals Ni, Cu, and Al, or one of the noble metals Au, Pt, Ag, and Pd, or an alloy composed of two or more metals.
9. A metal analysis method using an in-situ SEM thermogravimetric system based on a MEMS cantilever beam as described in any one of claims 1-6, characterized in that, The steps for analyzing transition metal thermally oxidized nanowires are as follows: Step 1: After cleaning the MEMS cantilever beam, drop-coat the metal powder to be tested onto the sample loading area, and after drying, mount the MEMS cantilever beam into the SEM (Scanning Electron Microscope). Step 2: Close the chamber door of the SEM (Scanning Electron Microscope), evacuate the vacuum, adjust the field of view, adjust the position and height of the sample area, and adjust the electron beam collimation, astigmatism, magnification, and scanning parameters of the SEM. Step 3: Start the measurement and control software through the host computer, control the temperature of the sample loading area at the set constant temperature and keep it at the set temperature for a set time, monitor the mass change of the metal powder to be tested through the weighing module, and record the morphological evolution of the sample by SEM scanning electron microscope, that is, the length of thermally oxidized nanowires on micron particles. Step 4: Repeat steps 1-3 above to obtain the kinetic parameters of the thermal oxidation growth of nanowires from the metal powder under test at different temperatures, and analyze the correlation between the nanowire growth rate and the weight gain to characterize the thermodynamic and kinetic properties of thermal oxidation growth.
10. The precious metal analysis method as described in claim 9, characterized in that, The transition metal is one of W, Ti, and Fe, and the metal powder particle size is 1-50 µm; in step 3, the nanowires grown by W, Ti, and Fe under a set constant temperature and oxygen partial pressure are W, Ti, and Fe, respectively. 3-x Nanowires, TiO2 nanowires and Fe2O3 nanowires.