Method and system for measuring glass-transition temperature of heat-sensitive material based on ultrafast photoacoustic spectroscopy

Abstract

The invention discloses a method and a system for measuring the glass transition temperature of a heat-sensitive material based on an ultrafast photoacoustic spectrum. The method comprises the following steps: preparing a heterostructure formed by superposing a two-dimensional semiconductor film and a heat-sensitive material film; on the basis of a femtosecond laser pumping detection technology, pumping laser pulses and detection laser pulses with different time delays are focused on the surface of a two-dimensional semiconductor film, and a time-resolved ultrafast photoacoustic spectrum is detected; time-resolved ultrafast photoacoustic spectra at different temperatures are obtained by heating the heterostructure; performing data processing on the time-resolved ultrafast photoacoustic spectrum, extracting the center frequencies of the Brillouin oscillation signals at different temperatures, and fitting to obtain a center frequency-temperature relation curve; an inflection point in the center frequency-temperature relation curve is extracted, and the temperature where the inflection point is located serves as the glass-transition temperature of the heat-sensitive material corresponding to the heat-sensitive material film. The method has the advantages of high sensitivity, high accuracy and non-destructive detection.

Description

Technical Field

[0001] The invention relates to a glass transition temperature measurement technology, and in particular to a method and a system for measuring the glass transition temperature of a heat-sensitive material based on ultrafast photoacoustic spectroscopy. Background Art

[0002] The glass transition temperature (Tg) is a key parameter for evaluating the transition of a material from a glassy state to a highly elastic state. When the ambient temperature is greater than the glass transition temperature, mechanical parameters such as density, thermal expansion coefficient, and modulus of thermosensitive materials change significantly, which has an important impact on the mechanical stability of thermosensitive material devices. It is an important material parameter that needs to be considered in the construction of a new generation of microelectronic devices and chips. How to measure the glass transition temperature of thermosensitive materials in situ, non-destructively, and accurately has important scientific significance and urgent industrial needs.

[0003] Traditional methods for obtaining the glass transition temperature of thermosensitive materials based on mechanical parameter detection, such as the nanoindentation method, rely on direct contact with the sample to measure changes in mechanical properties. However, this contact testing method usually causes a certain degree of damage to the sample surface or structure, thereby causing irreversible deformation or performance degradation. In addition, since the nanoindentation method mainly characterizes the mechanical behavior of the surface area of ​​the material, it is difficult to obtain information about the internal structure of the sample, which limits its application in in-depth research on the microscopic mechanism of thermosensitive materials. The dilatometer method, as another commonly used measurement method, infers the glass transition temperature by measuring the law of material size change with temperature. However, when studying samples that are small in size, irregular in shape, or susceptible to external stress, the sensitivity and accuracy of the test will be limited.

[0004] In summary, traditional methods cannot meet the needs of rapid, accurate, and non-destructive testing capabilities for the evaluation and application of thermal-sensitive materials. Therefore, it is urgent to develop a non-destructive testing method that can quickly and accurately measure the temperature-dependent physical parameters of thermal-sensitive materials, monitor the glass transition process and temperature, and support the basic research and industrial application of thermal-sensitive materials. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention aims to provide a method and system for measuring the glass transition temperature of thermosensitive materials based on ultrafast photoacoustic spectroscopy, so as to realize sensitive, accurate and non-destructive detection of the glass transition temperature parameters of thermosensitive materials.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] A method for measuring the glass transition temperature of a thermosensitive material based on ultrafast photoacoustic spectroscopy, comprising:

[0008] Step 1: preparing a heterostructure of a two-dimensional semiconductor film and a thermosensitive material film stacked together, wherein the two-dimensional semiconductor film includes a plurality of two-dimensional semiconductor layers;

[0009] Step 2: Based on the femtosecond laser pump-probe technology, pump laser pulses and probe laser pulses with different time delays are generated, and the pump laser pulses and probe laser pulses with different time delays are focused on the surface of the two-dimensional semiconductor film to detect the Brillouin oscillation signal formed by the coherent superposition of the reflected light on the surface of the two-dimensional semiconductor film and the reflected light of the picosecond acoustic wave pulse in the thermal sensitive material under different time delays, i.e., time-resolved ultrafast photoacoustic spectroscopy;

[0010] Step 3: heating the heterostructure to different temperatures to obtain time-resolved ultrafast photoacoustic spectra at different temperatures;

[0011] Step 4: Process the time-resolved ultrafast photoacoustic spectra at different temperatures to obtain the spectra of the Brillouin oscillation signals at different temperatures, and extract the center frequencies of the Brillouin oscillation signals at different temperatures from the spectra;

[0012] Step 5: According to the center frequency of the Brillouin oscillation signal corresponding to different temperatures, a center frequency-temperature relationship curve is obtained by fitting;

[0013] Step 6: Extract the inflection point in the center frequency-temperature relationship curve, and use the temperature at the inflection point as the glass transition temperature of the thermosensitive material corresponding to the thermosensitive material film.

[0014] Furthermore, the step 2 specifically includes:

[0015] Focusing the pump laser pulse on the surface of the two-dimensional semiconductor film causes the interlayer coherent acoustic phonons of the two-dimensional semiconductor film to oscillate, thereby emitting picosecond acoustic wave pulses into the thermosensitive material film. During the propagation of the picosecond acoustic wave pulses, the optical refractive index of the thermosensitive material undergoes a transient change, forming an acoustic-optical reflection interface.

[0016] When the time-delayed detection laser pulse arrives, the detection laser pulse reflected by the surface of the two-dimensional semiconductor film and the detection laser pulse reflected by the acousto-optic reflection interface are coherently superimposed to form a Brillouin oscillation signal;

[0017] By setting the time delay to different values, the Brillouin oscillation signals under different time delays are obtained, namely, time-resolved ultrafast photoacoustic spectroscopy.

[0018] A system for measuring glass transition temperature of thermosensitive materials based on ultrafast photoacoustic spectroscopy, comprising:

[0019] A femtosecond laser pump-probe module is used to generate pump laser pulses and probe laser pulses with different time delays based on femtosecond laser pump-probe technology, and focus the pump laser pulses and probe laser pulses with different time delays on the surface of the two-dimensional semiconductor film of the heterostructure, and detect the Brillouin oscillation signal formed by the coherent superposition of the reflected light on the surface of the two-dimensional semiconductor film and the reflected light of the picosecond acoustic wave pulse in the thermosensitive material under different time delays, i.e., time-resolved ultrafast photoacoustic spectroscopy. Wherein, the heterostructure is a superposition structure of a two-dimensional semiconductor film and a thermosensitive material film, and the two-dimensional semiconductor film includes several two-dimensional semiconductor layers;

[0020] A controllable heating stage is placed under the heterostructure and is used to heat the heterostructure to different temperatures, thereby obtaining time-resolved ultrafast photoacoustic spectra at different temperatures;

[0021] A data processing module is used to process the time-resolved ultrafast photoacoustic spectra at different temperatures to obtain the frequency spectra of the Brillouin oscillation signals at different temperatures, and to extract the center frequencies of the Brillouin oscillation signals at different temperatures from the frequency spectra;

[0022] A curve fitting module is used to fit the center frequency-temperature relationship curve according to the center frequency of the Brillouin oscillation signal corresponding to different temperatures;

[0023] The glass transition temperature extraction module is used to obtain the sound velocity and Young's modulus of the thermosensitive material corresponding to the thermosensitive material film, and determine the glass transition temperature of the thermosensitive material according to the sound velocity and Young's modulus based on the center frequency-temperature relationship curve.

[0024] Furthermore, the femtosecond laser pumping detection module specifically includes:

[0025] Laser emission equipment, used to generate pump laser pulses and detection laser pulses;

[0026] A time delay device, used to delay the detection laser pulse to reach the surface of the two-dimensional semiconductor film compared to the pump laser pulse, and to adjust the time delay to different values;

[0027] A microscope objective lens, used to focus the pump laser pulse and the probe laser pulse on the surface of the two-dimensional semiconductor film;

[0028] The optical detector is used to detect Brillouin oscillation signals under different time delays when the time delay device adjusts the time delay to different values, that is, time-resolved ultrafast photoacoustic spectroscopy, wherein the Brillouin oscillation signal is an interference signal formed by the coherent superposition of the detection laser pulse reflected by the surface of the two-dimensional semiconductor film and the detection laser pulse reflected by the acousto-optic reflection interface, and the formation process of the acousto-optic reflection interface is: when the pump laser pulse is focused on the two-dimensional semiconductor film, the coherent acoustic phonon oscillation between the generation layers of the two-dimensional semiconductor film is caused, thereby emitting picosecond acoustic wave pulses into the thermosensitive material film, and the picosecond acoustic wave pulses cause the optical refractive index of the thermosensitive material to produce transient changes during the propagation process, thereby forming the acousto-optic reflection interface.

[0029] Compared with the prior art, the present invention has the following advantages: (1) the present invention uses a two-dimensional semiconductor film as the emission source of picosecond acoustic wave pulses, which can realize the emission of GHz ultra-high frequency ultrasound, and the wavelength reaches the nanometer scale, so it has a high spatial measurement resolution; (2) the present invention is an all-optical non-destructive testing method; (3) the present invention has the ability to monitor the dynamic changes of mechanical parameters of thermal sensitive materials in real time. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic flow chart of a method for measuring the glass transition temperature of a thermosensitive material based on ultrafast photoacoustic spectroscopy provided in an embodiment of the present invention;

[0031] Figure 2 Schematic diagram of the femtosecond laser pump-probe principle;

[0032] Figure 3 Time-domain ultrafast photoacoustic spectra (a) and spectrum (b) at room temperature;

[0033] Figure 4 is the Brillouin oscillation spectrum at different temperatures;

[0034] Figure 5 This is the center frequency-temperature relationship curve of the Brillouin oscillation signal. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0036] Embodiment 1

[0037] The embodiment of the present invention provides a method for measuring the glass transition temperature of a thermosensitive material based on ultrafast photoacoustic spectroscopy. Figure 1 As shown, including:

[0038] Step 1: Prepare a heterostructure of a two-dimensional semiconductor film and a thermosensitive material film stacked together, wherein the two-dimensional semiconductor film includes a plurality of two-dimensional semiconductor layers.

[0039] In this embodiment, PMMA film is used as an example of a heat-sensitive material and MoS2 is used as an example of a two-dimensional semiconductor film for research. It can be understood that in other embodiments, other two-dimensional semiconductor materials can also be used to test other heat-sensitive materials.

[0040] First, a MoS2 film is prepared on a substrate. The MoS2 film includes several MoS2 layers and is prepared by mechanical exfoliation. Then, a PMMA film of a heat-sensitive material is covered on the MoS2 film to form a heterostructure. The preparation method is as follows:

[0041] 1) Place the coating machine in a vacuum state to ensure that the MoS2 film with the substrate can be firmly adsorbed on the surface of the coating machine;

[0042] 2) adding anisole solution containing PMMA dropwise onto the surface of the MoS2 film;

[0043] 3) In the spin coating step, first spin at 600 r / min for 30 seconds to initially distribute the solution; then adjust the spin coating speed to 2000 r / min and spin for 60 seconds to further stretch and evenly coat the film;

[0044] 4) Finally, the spin-coated sample was annealed in a heating environment at 423K for 30 minutes to obtain a PMMA film with uniform thickness and good adhesion on the MoS2 film, and then the substrate under the MoS2 film was removed.

[0045] Step 2: Based on the femtosecond laser pump-probe technology, pump laser pulses and probe laser pulses with different time delays are generated, and the pump laser pulses and probe laser pulses with different time delays are focused on the surface of the two-dimensional semiconductor film. The Brillouin oscillation signal formed by the coherent superposition of the reflected light on the surface of the two-dimensional semiconductor film and the reflected light of the picosecond acoustic wave pulse in the thermal sensitive material under different time delays is detected, that is, the time-resolved ultrafast photoacoustic spectroscopy.

[0046] In this embodiment, the pump laser pulse (400nm) and the probe laser pulse (800nm) are both generated by a titanium sapphire femtosecond laser with an output central wavelength of 800nm, a pulse width of about 100fs, and a repetition frequency of 80MHz. The pump and probe laser powers are 0.3mW and 0.1mW respectively, and the two light spots are overlapped in space and focused on the same position of the MoS2 film through an optical microscope objective.

[0047] like Figure 2As shown, the pump laser pulse is focused on the surface of the MoS2 film, so that longitudinal coherent acoustic phonon oscillations are generated between the layers of the MoS2 film, thereby emitting picosecond acoustic wave pulses into the PMMA film through heterogeneous interface coupling. During the propagation of the picosecond acoustic wave pulse, the optical refractive index of the thermal sensitive material undergoes a transient change, forming an acoustic-optical reflection interface. When the time-delayed detection laser pulse arrives, the detection laser pulse reflected by the surface of the two-dimensional semiconductor film is coherently superimposed with the detection laser pulse reflected by the acoustic-optical reflection interface, forming a Brillouin oscillation signal. By setting the time delay to different values, the time-resolved ultrafast photoacoustic spectrum of the Brillouin oscillation signal reflected on the MoS2 surface can be detected, as shown in Figure 3 Shown is the time-domain ultrafast photoacoustic spectrum and frequency spectrum at room temperature, with a center frequency of 10.0 GHz.

[0048] Step 3: Heat the heterostructure to different temperatures to obtain time-resolved ultrafast photoacoustic spectra at different temperatures.

[0049] The heating temperature of the heterostructure ranges from 293 K to 393 K. The temperature is gradually increased by a controllable heating stage. During the heating process, the temperature change interval is set to 10 K and maintained at each target temperature for 20 minutes to ensure uniform and stable heating.

[0050] Step 4: Process the time-resolved ultrafast photoacoustic spectra at different temperatures to obtain the frequency spectra of the Brillouin oscillation signals at different temperatures, and extract the center frequencies of the Brillouin oscillation signals at different temperatures from the frequency spectra.

[0051] The data processing of time-resolved ultrafast photoacoustic spectroscopy includes double exponential function background removal, Fourier transform and time domain zero filling, so as to obtain the spectrum of Brillouin oscillation signal at different temperatures, such as Figure 4 As shown in the figure, it can be seen that the center position of the frequency peak (center frequency) moves toward the low frequency direction as the temperature increases. By marking the movement trend of the center frequency with arrows, an obvious inflection point can be found.

[0052] Step 5: According to the center frequency of the Brillouin oscillation signal corresponding to different temperatures, a center frequency-temperature relationship curve is fitted.

[0053] The center frequency-temperature relationship curve of this embodiment is as follows: Figure 5 shown.

[0054] Step 6: Extract the inflection point in the center frequency-temperature relationship curve, and use the temperature at the inflection point as the glass transition temperature of the thermosensitive material corresponding to the thermosensitive material film.

[0055] exist Figure 5In the center frequency-temperature curve, a significant turning point appears at 370K, indicating that this temperature is the glass transition temperature (Tg) of the polymer film.

[0056] This embodiment can also obtain mechanical parameters such as the sound velocity and Young's modulus of the thermosensitive material. The sound velocity of the thermosensitive material can be calculated by the following formula:

[0057]

[0058] f b represents the Brillouin oscillation center frequency of the picosecond acoustic wave pulse, and n is the wavelength of the detection laser λ at which the thermal sensitive material pr The optical refractive index at , v is the sound velocity of the heat-sensitive material.

[0059] Young's modulus can be estimated by the following formula:

[0060] E=ρv 2

[0061] E represents the Young's modulus of the thermosensitive material, ρ is the density of the thermosensitive material, and v is the sound velocity of the thermosensitive material.

[0062] The experimental results show that the present invention has high sensitivity and high reliability in detecting the glass transition temperature of polymer films based on picosecond acoustic wave technology, which effectively verifies the practicality and advancement of the present invention.

[0063] Embodiment 2

[0064] The embodiment of the present invention provides a system for measuring the glass transition temperature of a thermosensitive material based on ultrafast photoacoustic spectroscopy, comprising:

[0065] A femtosecond laser pump-probe module is used to generate pump laser pulses and probe laser pulses with different time delays based on femtosecond laser pump-probe technology, and focus the pump laser pulses and probe laser pulses with different time delays on the surface of a two-dimensional semiconductor film of a heterostructure, and detect the Brillouin oscillation signal formed by the coherent superposition of the reflected light on the surface of the two-dimensional semiconductor film and the reflected light of the picosecond acoustic wave pulse in the thermosensitive material under different time delays, i.e., time-resolved ultrafast photoacoustic spectroscopy; wherein the heterostructure is a superposition structure of a two-dimensional semiconductor film and a thermosensitive material film, and the two-dimensional semiconductor film includes a plurality of two-dimensional semiconductor layers;

[0066] A controllable heating stage is placed under the heterostructure to heat the heterostructure to different temperatures, thereby obtaining time-resolved ultrafast photoacoustic spectra at different temperatures; the temperature range is 293K to 393K;

[0067] A data processing module is used to process the time-resolved ultrafast photoacoustic spectra at different temperatures (including double exponential function background removal, Fourier transform and time domain zero filling), obtain the spectrum of the Brillouin oscillation signal at different temperatures, and extract the center frequency of the Brillouin oscillation signal at different temperatures from the spectrum;

[0068] A curve fitting module, used for fitting a center frequency-temperature relationship curve according to the center frequency of the Brillouin oscillation signal corresponding to different temperatures; the center frequency-temperature relationship curve is obtained by fitting a Lorentz function;

[0069] The glass transition temperature extraction module is used to obtain the sound velocity and Young's modulus of the thermosensitive material corresponding to the thermosensitive material film, and determine the glass transition temperature of the thermosensitive material according to the sound velocity and Young's modulus based on the center frequency-temperature relationship curve.

[0070] Wherein, the femtosecond laser pump detection module specifically includes:

[0071] Laser emission equipment, used to generate pump laser pulses and detection laser pulses;

[0072] A time delay device, used to delay the detection laser pulse to reach the surface of the two-dimensional semiconductor film compared to the pump laser pulse, and to adjust the time delay to different values;

[0073] A microscope objective lens, used to focus the pump laser pulse and the probe laser pulse on the surface of the two-dimensional semiconductor film;

[0074] The optical detector is used to detect Brillouin oscillation signals under different time delays when the time delay device adjusts the time delay to different values, that is, time-resolved ultrafast photoacoustic spectroscopy, wherein the Brillouin oscillation signal is an interference signal formed by the coherent superposition of the detection laser pulse reflected by the surface of the two-dimensional semiconductor film and the detection laser pulse reflected by the acousto-optic reflection interface, and the formation process of the acousto-optic reflection interface is: when the pump laser pulse is focused on the two-dimensional semiconductor film, the coherent acoustic phonon oscillation between the generation layers of the two-dimensional semiconductor film is caused, thereby emitting picosecond acoustic wave pulses into the thermosensitive material film, and the picosecond acoustic wave pulses cause the optical refractive index of the thermosensitive material to produce transient changes during the propagation process, thereby forming the acousto-optic reflection interface.

[0075] The system provided in the embodiment of the present invention can be used to execute the method provided in the first embodiment of the present invention, and has the corresponding functions and beneficial effects of the execution method.

[0076] It is worth noting that in the embodiment of the above system, the various units and modules included are only divided according to functional logic, but are not limited to the above division, as long as the corresponding functions can be achieved; in addition, the specific names of the functional units are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of the present invention.

[0077] The embodiments described above are only illustrative, wherein the modules described as separate components may or may not be physically separated, and the components displayed as modules may or may not be physical modules, i.e., they may be located in one place, or they may be distributed on multiple network modules. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, or of course, it can be implemented only by hardware, as long as the function or effect can be achieved.

[0078] It should be understood that the above embodiments and descriptions only describe the principles, main features and advantages of the present invention. Without departing from the spirit and scope of the present invention, the present invention may be subject to various changes and improvements, and these changes and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for measuring the glass transition temperature of a thermosensitive material based on ultrafast photoacoustic spectroscopy, characterized in that: include: Step 1: preparing a heterostructure of a two-dimensional semiconductor film and a thermosensitive material film, wherein the two-dimensional semiconductor film includes a plurality of two-dimensional semiconductor layers; Step 2: Based on the femtosecond laser pump-probe technology, pump laser pulses and probe laser pulses with different time delays are generated, and the pump laser pulses and probe laser pulses with different time delays are focused on the surface of the two-dimensional semiconductor film to detect the Brillouin oscillation signal formed by the coherent superposition of the reflected light from the surface of the two-dimensional semiconductor film and the reflected light from the picosecond acoustic wave pulse in the thermal sensitive material under different time delays, i.e., time-resolved ultrafast photoacoustic spectroscopy; Step 3: heating the heterostructure to different temperatures to obtain time-resolved ultrafast photoacoustic spectra at different temperatures; Step 4: Process the time-resolved ultrafast photoacoustic spectra at different temperatures to obtain the spectra of the Brillouin oscillation signals at different temperatures, and extract the center frequencies of the Brillouin oscillation signals at different temperatures from the spectra; Step 5: According to the center frequency of the Brillouin oscillation signal corresponding to different temperatures, a center frequency-temperature relationship curve is obtained by fitting; Step 6: Extract the inflection point in the center frequency-temperature relationship curve, and use the temperature at the inflection point as the glass transition temperature of the thermosensitive material corresponding to the thermosensitive material film.

2. The method for measuring the glass transition temperature of a thermosensitive material based on ultrafast photoacoustic spectroscopy according to claim 1, characterized in that: The step 2 specifically includes: Focusing the pump laser pulse on the surface of the two-dimensional semiconductor film causes the interlayer coherent acoustic phonons of the two-dimensional semiconductor film to oscillate, thereby emitting picosecond acoustic wave pulses into the thermosensitive material film. During the propagation of the picosecond acoustic wave pulses, the optical refractive index of the thermosensitive material undergoes a transient change, forming an acoustic-optical reflection interface. When the time-delayed detection laser pulse arrives, the detection laser pulse reflected by the surface of the two-dimensional semiconductor film and the detection laser pulse reflected by the acousto-optic reflection interface of the picosecond acoustic wave pulse are coherently superimposed to form a Brillouin oscillation signal; By setting the time delay to different values, the Brillouin oscillation signals under different time delays are detected, namely, time-resolved ultrafast photoacoustic spectroscopy.

3. The method for measuring the glass transition temperature of a thermosensitive material based on ultrafast photoacoustic spectroscopy according to claim 1, characterized in that: In the step 5, the center frequency-temperature relationship curve is obtained by fitting the Lorentz function.

4. The method for measuring the glass transition temperature of a thermosensitive material based on ultrafast photoacoustic spectroscopy according to claim 1, characterized in that: The heating temperature range of the heterostructure in step 3 is 293K to 393K.

5. The method for measuring the glass transition temperature of a thermosensitive material based on ultrafast photoacoustic spectroscopy according to claim 1, characterized in that: The data processing in step 4 includes double exponential function background removal, Fourier transform and time domain zero filling.

6. A system for measuring the glass transition temperature of thermosensitive materials based on ultrafast photoacoustic spectroscopy, characterized in that: include: A femtosecond laser pump-probe module is used to generate pump laser pulses and probe laser pulses with different time delays based on femtosecond laser pump-probe technology, and focus the pump laser pulses and probe laser pulses with different time delays on the surface of a two-dimensional semiconductor film of a heterostructure, and detect the Brillouin oscillation signal formed by the coherent superposition of the reflected light on the surface of the two-dimensional semiconductor film and the reflected light of the picosecond acoustic wave pulse in the thermosensitive material under different time delays, i.e., time-resolved ultrafast photoacoustic spectroscopy; wherein the heterostructure is a superposition structure of a two-dimensional semiconductor film and a thermosensitive material film, and the two-dimensional semiconductor film includes a plurality of two-dimensional semiconductor layers; A controllable heating stage is placed under the heterostructure and is used to heat the heterostructure to different temperatures, thereby obtaining time-resolved ultrafast photoacoustic spectra at different temperatures; A data processing module is used to process the time-resolved ultrafast photoacoustic spectra at different temperatures to obtain the frequency spectra of the Brillouin oscillation signals at different temperatures, and to extract the center frequencies of the Brillouin oscillation signals at different temperatures from the frequency spectra; A curve fitting module is used to fit the center frequency-temperature relationship curve according to the center frequency of the Brillouin oscillation signal corresponding to different temperatures; The glass transition temperature extraction module is used to obtain the sound velocity and Young's modulus of the thermosensitive material corresponding to the thermosensitive material film, and determine the glass transition temperature of the thermosensitive material according to the sound velocity and Young's modulus based on the center frequency-temperature relationship curve.

7. The system for measuring glass transition temperature of thermosensitive materials based on ultrafast photoacoustic spectroscopy according to claim 6, characterized in that: The femtosecond laser pumping detection module specifically includes: Laser emission equipment, used to generate pump laser pulses and detection laser pulses; A time delay device, used to delay the detection laser pulse to reach the surface of the two-dimensional semiconductor film compared to the pump laser pulse, and to adjust the time delay to different values; A microscope objective lens, used to focus the pump laser pulse and the probe laser pulse on the surface of the two-dimensional semiconductor film; The optical detector is used to detect Brillouin oscillation signals under different time delays when the time delay device adjusts the time delay to different values, that is, time-resolved ultrafast photoacoustic spectroscopy, wherein the Brillouin oscillation signal is an interference signal formed by the coherent superposition of the detection laser pulse reflected by the surface of the two-dimensional semiconductor film and the detection laser pulse reflected by the acousto-optic reflection interface, and the formation process of the acousto-optic reflection interface is: when the pump laser pulse is focused on the two-dimensional semiconductor film, the coherent acoustic phonon oscillation between the generation layers of the two-dimensional semiconductor film is caused, thereby emitting picosecond acoustic wave pulses into the thermosensitive material film, and the picosecond acoustic wave pulses cause the optical refractive index of the thermosensitive material to produce transient changes during the propagation process, thereby forming the acousto-optic reflection interface.

8. The system for measuring glass transition temperature of thermosensitive materials based on ultrafast photoacoustic spectroscopy according to claim 6, characterized in that: The center frequency-temperature relationship curve is obtained by fitting the Lorentz function.

9. The method for measuring the glass transition temperature of a thermosensitive material based on ultrafast photoacoustic spectroscopy according to claim 6, characterized in that: The controllable heating stage heats the heterostructure in a temperature range of 293K to 393K.

10. The system for measuring glass transition temperature of thermosensitive materials based on ultrafast photoacoustic spectroscopy according to claim 6, characterized in that: The data processing of the time-resolved ultrafast photoacoustic spectroscopy specifically includes double exponential function background removal, Fourier transform and time domain zero filling.

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