Method and device for enhancing coherent acoustic phonon signal in MoS2 / GaAs system by using MoS2

Abstract

The invention discloses a method and device for enhancing coherent acoustic phonon signals in a MoS2 / GaAs system through MoS2, and the method comprises the steps that MoS2 serves as a transducer to amplify coherent acoustic phonons in a GaAs material, the amplification amplitude of the coherent acoustic phonon signals in the MoS2 / GaAs system is controlled by adjusting the thickness of MoS2, and the thickness of MoS2 ranges from 40 nm to 130 nm. According to the method, the optimal thickness is predicted and selected in advance through a transmission matrix method to achieve the maximum amplification factor, data extraction is facilitated, and nondestructive extraction of precision information such as defects of semiconductor materials such as chips is facilitated.

Description

Technical Field

[0001] The present application relates to the field of detection and analysis technology, and in particular to a method for using MoS 2 Enhanced MoS 2 Method and apparatus for detecting coherent acoustic phonon signals in GaAs / GaAs systems. Background Art

[0002] With the widespread application of emerging technologies such as artificial intelligence and 5G, the requirements for chip manufacturing technology and processes are also increasing. However, the detection of internal defects and process completeness of chips has always been a difficult problem to overcome. There are currently many methods for internal inspection of chip semiconductors, but all of them have defects such as insufficient resolution and limited detection depth. Although semiconductor defects can be detected by optical means, optical detection also faces great challenges because light has difficulty penetrating most semiconductor materials.

[0003] To overcome these problems, pump-probe technology can be used to excite coherent acoustic phonons inside the semiconductor, and internal defect information can be detected by converting optical signals into acoustic signals, thereby effectively circumventing the limitations of optical detection. In the study of time-domain coherent acoustic phonons, in order to more accurately analyze its characteristics, it is usually hoped that the amplitude of the detected coherent acoustic phonons will be larger so that more useful information can be extracted. To this end, the amplitude of the detected coherent acoustic phonons can be enhanced from both the detection method and the excitation method, thereby improving the detection accuracy and the richness of information acquisition.

[0004] From the detection perspective, the wavelength of the detection light directly affects the amplitude, frequency and detection depth of the coherent acoustic phonons. Shorter wavelengths usually enhance the amplitude of the signal, but may lead to a shallower detection depth; while longer wavelengths can increase the detection depth, but may reduce the amplitude. This dependence shows that the wavelength of the detection light not only affects the signal intensity, but also changes the frequency of the coherent acoustic phonons. Therefore, it is necessary to weigh the relationship between amplitude, frequency and depth to optimize the detection effect. Summary of the invention

[0005] In view of the above problems, the present invention provides a method for utilizing MoS 2 Enhanced MoS 2 The invention discloses a method and device for detecting coherent acoustic phonon signals in a GaAs system, aiming to select appropriate thickness information to achieve the maximum amplification requirement for coherent acoustic phonons.

[0006] In a first aspect of the present invention, a method using MoS 2 Enhanced MoS 2 A method for detecting coherent acoustic phonon signals in a MoS / GaAs system, comprising: 2 As a transducer to amplify the coherent acoustic phonons in GaAs materials, and by regulating MoS2 Thickness Control MoS 2 / GaAs system coherent acoustic phonon signal amplification amplitude, among which MoS 2 The thickness is 40nm-130nm.

[0007] A further technical solution of the present invention is: by adjusting the MoS 2 Thickness Control MoS 2 / GaAs system coherent acoustic phonon amplification factor, specifically through the transmission matrix method to predict in advance and select the optimal thickness to achieve the maximum amplification factor.

[0008] A further technical solution of the present invention is: MoS 2 When the thickness is 80nm, MoS 2 / GaAs system coherent acoustic phonon signal reaches a peak.

[0009] A further technical solution of the present invention is: the transmission matrix method specifically includes:

[0010] MoS 2 The expression of reflectivity R of GaAs system is: in, Air and MoS 2 Film, MoS 2 The complex amplitude of the reflection coefficient at the interface between the film and GaAs, and the complex refractive index of each material are represents the complex refractive index in air, Indicates the first layer material, namely MoS 2 The complex refractive index, represents the complex refractive index of the second layer material, GaAs, n i represents the real part of the complex refractive index, κ i represents the imaginary part of the complex refractive index, δ i represents complex phase shift;

[0011] After the pump pulse is excited, the real part n and imaginary part κ of the complex refractive index change, which leads to the change of reflectivity R. 2 Medium ΔR / R 0 With Δn / n 0 and Δκ / κ 0 The changes in MoS 2 Thickness change affects differential reflectivity ΔR / R 0 The numerical value of (ΔR / R 0 ) / (Δn / n 0 ) slope characterizes the magnitude of coherent acoustic phonon oscillation, n 0 , κ 0 and R0 are the parameters of n, κ and R under equilibrium conditions, ΔR, Δn, Δκ represent the changes of n, κ and R;

[0012] Get MoS 2 / GaAs system (ΔR / R 0 ) / (Δn / n 0 ) slope with MoS 2 The relationship between the thickness change and the peak value of the coherent acoustic phonon signal can be obtained. 2 thickness.

[0013] The second aspect of the present invention provides a method for utilizing MoS 2 Enhanced MoS 2 / GaAs system, the device is configured to:

[0014] MoS 2 As a transducer to amplify the coherent acoustic phonons in GaAs materials, and by regulating MoS 2 Thickness Control MoS 2 / GaAs system coherent acoustic phonon signal amplification amplitude, among which MoS 2 The thickness is 40nm-130nm.

[0015] The device is further configured to: 2 Thickness Control MoS 2 / GaAs system coherent acoustic phonon amplification amplitude, specifically through the transmission matrix method to predict and select the optimal thickness in advance to achieve the maximum amplification factor.

[0016] The device is further configured as follows: the transmission matrix method specifically includes:

[0017] MoS 2 The expression of reflectivity R of GaAs system is: in, Air and MoS 2 Film, MoS 2 The complex amplitude of the reflection coefficient at the interface between the film and GaAs, and the complex refractive index of each material are represents the complex refractive index in air, Indicates the first layer material, namely MoS 2 The complex refractive index, represents the complex refractive index of the second layer material, GaAs, n i represents the real part of the complex refractive index, κ i represents the imaginary part of the complex refractive index, δ i represents complex phase shift;

[0018] After the pump pulse is excited, the real part n and imaginary part κ of the complex refractive index change, which leads to the change of reflectivity R. 2 Medium ΔR / R 0 With Δn / n 0 and Δκ / κ 0 The changes in MoS 2 Thickness change affects differential reflectivity ΔR / R 0 The numerical value of (ΔR / R 0 ) / (Δn / n 0 ) slope characterizes the magnitude of coherent acoustic phonon oscillation, n 0 , κ 0 and R 0 are the parameters of n, κ and R under equilibrium conditions, ΔR, Δn, Δκ represent the changes of n, κ and R;

[0019] Get MoS 2 / GaAs system (ΔR / R 0 ) / (Δn / n 0 ) slope with MoS 2 The relationship between the thickness change and the peak value of the coherent acoustic phonon signal can be obtained. 2 thickness.

[0020] The device is further configured as: MoS 2 When the thickness is 80nm, MoS 2 / GaAs system coherent acoustic phonon signal reaches a peak.

[0021] The present invention provides a method of using MoS 2 Enhanced MoS 2 / GaAs system, using MoS 2 As a transducer to amplify coherent acoustic phonons in GaAs materials, it can also be tuned by MoS 2 The thickness of MoS is controlled 2 / GaAs system coherent acoustic phonon amplification, in MoS 2 When the thickness is greater than 40nm, the signal can be amplified, and the optimal thickness can be predicted and selected in advance through the transmission matrix method to achieve the maximum amplification factor, which is convenient for data extraction and more conducive to the lossless extraction of precise information such as defects of semiconductor materials such as chips.

[0022] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1(a) is MoS in the embodiment of the present invention 2 MoS with a thickness of 1-100 nm 2 ΔR / R in GaAs 0 As Δn / n 0 The change curve diagram of

[0024] Figure 1 (b) is MoS in the embodiment of the present invention 2 / GaAs system (ΔR / R 0 ) / (Δn / n 0 ) slope with MoS 2 Thickness change relationship curve diagram;

[0025] Figure 2 (a) is a comparison diagram of the pump-probe results of three samples and bulk GaAs in the embodiment of the present invention;

[0026] Figure 2 (b) is a comparison diagram of the coherent acoustic phonon oscillations of three samples and bulk GaAs extracted in the embodiment of the present invention;

[0027] Figure 3 In the embodiments of the present invention, the thickness of MoS is 2nm, 4nm, and 80nm respectively. 2 MoS 2 Comparison of the Fast Fourier Transform (FFT) amplitudes corresponding to the coherent acoustic phonon oscillations of the GaAs / GaAs sample and bare GaAs. DETAILED DESCRIPTION

[0028] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0029] It should be mentioned before discussing the exemplary embodiments in more detail that some exemplary embodiments are described as processes or methods depicted as flow charts. Although the flow charts describe the steps as sequential processes, many of the steps therein can be implemented in parallel, concurrently or simultaneously. In addition, the order of the steps can be rearranged. The process can be terminated when its operation is completed, but can also have additional steps not included in the accompanying drawings. The process can correspond to a method, function, procedure, subroutine, subprogram, etc.

[0030] The embodiment of the present invention is directed to a method using MoS 2 Enhanced MoS 2 / GaAs system, the method and device provide the following embodiments:

[0031] From the perspective of pumping, the main means to increase the amplitude of coherent acoustic phonons include increasing the energy flux density of the pump pulse and the energy of the pump photons. The former can directly increase the phonon amplitude, but the energy level needs to be controlled to prevent sample damage; the latter achieves the purpose of amplitude enhancement by enhancing electron-phonon coupling, but it also faces the risk of sample damage. Using two-dimensional materials as photoacoustic transducers to transfer strain to samples that are difficult to excite directly can also increase the amplitude and make phonon excitation more efficient. At the same time, from the perspective of detection, the main means to increase the amplitude of coherent acoustic phonons include selecting a resonant detection wavelength. When the detection wavelength is fixed, selecting a two-dimensional material that is transparent to the detection wavelength and changing its thickness can effectively change the detection sensitivity. The combined application of these methods provides more options for coherent acoustic phonon research, so that experimental accuracy and sample protection are effectively balanced under different conditions.

[0032] A method using MoS 2 Enhanced MoS 2 A method for detecting coherent acoustic phonon signals in a GaAs system, comprising:

[0033] MoS 2 As a transducer to amplify the coherent acoustic phonons in GaAs materials, and by regulating MoS 2 Thickness Control MoS 2 / GaAs system coherent acoustic phonon signal amplification amplitude, among which MoS 2 The thickness is 40nm-130nm.

[0034] By regulating MoS 2 Thickness Control MoS 2 / GaAs system coherent acoustic phonon amplification factor, specifically through the transmission matrix method to predict in advance and select the optimal thickness to achieve the maximum amplification factor.

[0035] MoS 2 When the thickness is 80nm, MoS 2 / GaAs system coherent acoustic phonon signal reaches a peak.

[0036] The transfer matrix method specifically includes:

[0037] MoS 2 The expression of reflectivity R of GaAs system is: in, Air and MoS 2 Film, MoS 2 The complex amplitude of the reflection coefficient at the interface between the film and GaAs, and the complex refractive index of each material are represents the complex refractive index in air, Indicates the first layer material, namely MoS 2 The complex refractive index, represents the complex refractive index of the second layer material, GaAs, n i represents the real part of the complex refractive index, κ i represents the imaginary part of the complex refractive index, δ i represents complex phase shift;

[0038] After the pump pulse is excited, the real part n and imaginary part κ of the complex refractive index change, which leads to the change of reflectivity R. 2 Medium ΔR / R 0 With Δn / n 0 and Δκ / κ 0 The changes in MoS 2 Thickness change affects differential reflectivity ΔR / R 0 The numerical value of (ΔR / R 0 ) / (Δn / n 0 ) slope characterizes the magnitude of coherent acoustic phonon oscillation, n 0 , κ 0 and R 0 are the parameters of n, κ and R under equilibrium conditions, ΔR, Δn, Δκ represent the changes of n, κ and R;

[0039] Get MoS 2 / GaAs system (ΔR / R 0 ) / (Δn / n 0 ) slope with MoS 2 The relationship between the thickness change and the peak value of the coherent acoustic phonon signal can be obtained. 2 thickness.

[0040] Specifically, MoS can be transferred at room temperature and pressure. 2 To the GaAs material, it will not affect the chip itself, and by changing the two-dimensional material MoS 2 The thickness of the coherent acoustic phonons can be controlled to achieve the regulation of the amplification of the coherent acoustic phonons. The transfer matrix method can be used to predict and explain how to choose the appropriate thickness information to achieve the maximum amplification of the coherent acoustic phonons.

[0041] The transfer matrix method is an important mathematical tool that is widely used to analyze the propagation of waves or particles in complex media. This method is particularly suitable for dealing with propagation problems in multilayer dielectric structures, such as the reflection and transmission behavior of light in multilayer films, or the transmission characteristics of electrons in lattice structures. The transfer matrix method can effectively simplify the analysis process by layering the dielectric structure and using the transfer matrix to describe the influence of each layer on the wave or particle. The transfer matrix of each layer describes the interaction of the wave or particle in that layer, and finally the overall transmission characteristics of the entire multilayer structure are obtained by multiplying the matrices.

[0042] This method has a wide range of applications in physics, engineering, and materials science, especially in the design of optical and electronic devices. In the field of optics, the transfer matrix method is used to analyze and design the optical properties of multilayer film structures, thereby achieving the precise design of filters, reflectors, and other optical devices. In the design of electronic devices, this method can effectively handle the layered structure of semiconductor materials and help engineers optimize the electronic transmission characteristics of the device. Because the transfer matrix method can efficiently handle layered medium structures and provide a simplified mathematical framework in solving complex medium propagation problems, it has become an indispensable analytical tool in many fields.

[0043] In the study of optical thin films, properties such as light penetration depth, the real part (n) and imaginary part (κ) of the refractive index, and interface reflection are particularly critical. For optical films with a thickness less than or equal to the light penetration depth, the reflection characteristics are mainly determined by the real and imaginary parts of the refractive index. The real part of the refractive index (n) indicates the speed of light propagation in the material, while the imaginary part (κ) reflects the degree of light absorption. Due to multiple reflections between the air / film and film / substrate interfaces, these reflected beams will interfere, affecting the overall reflectivity (R).

[0044] This interference effect is directly related to the optical performance of the film. In this case, the transfer matrix method is effective. MoS 2 The analytical expression of the reflectivity R of the / GaAs system is as follows:

[0045]

[0046] in, and Air / MoS 2 Films and MoS 2 The complex amplitude of the reflection coefficient at the film / GaAs interface. The complex refractive index of each material is defined as and is the complex phase shift caused by the change in the optical path and the absorption in the thin film or GaAs, d irepresents the thickness of the i-th layer of material, and λ represents the wavelength of the detection light.

[0047] After the pump pulse is excited, the refractive index n and extinction coefficient κ of the film will change, which will lead to a change in the reflectivity R. It can be expressed as: n = n 0 +Δn,κ=κ 0 +Δκ, R=R 0 +ΔR, where n 0 , κ 0 and R 0 is a parameter under equilibrium conditions. To better understand the differential reflection (ΔR / R 0 ) and refractive index change (Δn / n 0 and Δκ / κ 0 ) in the double-layer sample. 2 Under the condition of material thickness, Δn / n is respectively 0 =-0.02, -0.01, 0, 0.01, 0.02 or Δκ / K 0 =-0.02, -0.01, 0, 0.01, 0.02, using formula (1) we can plot ΔR / R 0 As Δn / n 0 and Δκ / κ 0 The change relationship of the function, such as Figure 1 (a) shown.

[0048] By comparing different thicknesses of MoS 2 ΔR / R in the sample 0 With Δn / n 0 and Δκ / κ 0 The change of MoS 2 The change in thickness does affect the differential reflectivity ΔR / R 0 The numerical value of Δn / n 0 and Δκ / κ 0 Represent the percentage of change of the real and imaginary parts of the complex refractive index, then at this time, ΔR / R 0 As Δn / n 0 and Δκ / κ 0 The function line segment is derived to obtain the slope of the line segment. This slope corresponds to the degree to which the sample refractive index changes when the same pump laser excites samples of different thicknesses, and thus corresponds to the degree of change in the reflected signal, which corresponds to the change trend of the signal ΔR / R in the experiment. Therefore, (ΔR / R 0 ) / (Δn / n 0 ) can characterize the size of the coherent acoustic phonon oscillation. The change of the slope of the obtained line segment is as follows: Figure 1 (b) shows that in MoS 2 When it is about 1-40nm, (ΔR / R0 ) / (Δn / n 0 ) has a basically unchanged slope, so the amplitude of the coherent acoustic phonon remains basically unchanged. 2 The gradual increase in thickness (ΔR / R 0 ) / (Δn / n 0 ) slope, that is, the amplitude of the coherent acoustic phonon increases first, then reaches a peak, and then gradually decreases.

[0049] In order to verify the correctness of the transmission matrix, the inventors constructed different MoS 2 Thickness of MoS 2 / GaAs heterojunction, and use pump-probe technology to excite and detect the coherent acoustic phonon oscillation signal of the heterojunction, select the appropriate MoS 2 The thickness can amplify the GaAs material signal.

[0050] Figure 2 (a) shows the experimental results obtained by the inventors using the same pump-probe experiment. On this basis, the corresponding MoS 2 MoS 2 / GaAs and pure GaAs coherent acoustic phonon oscillations, such as Figure 2 (b) When the coherent acoustic phonon signals of the sample and pure GaAs are subjected to Fast Fourier Transform (FFT) and the frequencies are compared, Figure 3 As shown in Figure 2, it can be observed that the frequency shifts of the two vibration peaks are both around 40 GHz, which indicates that the acoustic emission of the sample mainly comes from GaAs itself, rather than MoS 2 A phase shift in the phase acoustic vibration was observed. This may be due to the fact that MoS 2 The phase matching of the surface acoustic waves between MoS and GaAs. The amplification of GaAs phonon signals is mainly concentrated in the low-frequency part of the signal, while the high-frequency part is basically not amplified. This may be due to the fact that MoS 2 The poor bonding between the GaAs material and the substrate results in a rough interface, which affects the generation of high-frequency signals. Figure 2 (b) and Figure 3 It can be seen that in the case of 2nm and 4nm thickness MoS 2 MoS 2 / GaAs samples, the coherent acoustic phonons of GaAs are not only not enhanced, but even slightly weakened, but at 80nm MoS 2 MoS 2 In the 2 / GaAs sample, the coherent acoustic phonon amplitude is significantly enhanced. 2 Thickness of MoS2 In the 2 / GaAs sample, the amplitude of the coherent acoustic phonon gradually weakened and remained constant after 130nm. It can be seen that the simulation results obtained by the transmission matrix are consistent with the experimental results of the inventors. 2 The thickness of the semiconductor can be adjusted to achieve the control of the amplification of coherent acoustic phonons, and the transmission matrix can be used to predict the corresponding amplification law. This is meaningful for better control of the oscillation amplitude of coherent acoustic phonons and further observation of the acoustic information inside the semiconductor.

[0051] Another embodiment is a method using MoS 2 Enhanced MoS 2 The device for detecting coherent acoustic phonon signals in a MoS / GaAs system can implement the method provided by any embodiment of the present invention using MoS 2 Enhanced MoS 2 / GaAs system, has the functional modules and beneficial effects corresponding to the execution method, and the device can be implemented by software and / or hardware (integrated circuit), and can generally be integrated into a server or terminal device. Specifically,

[0052] An embodiment of the present invention uses MoS 2 Enhanced MoS 2 / GaAs system, the device is configured to:

[0053] MoS 2 As a transducer to amplify the coherent acoustic phonons in GaAs materials, and by regulating MoS 2 Thickness Control MoS 2 / GaAs system coherent acoustic phonon signal amplification amplitude, among which MoS 2 The thickness is 40nm-130nm.

[0054] Furthermore, by adjusting the MoS 2 Thickness Control MoS 2 / GaAs system coherent acoustic phonon amplification amplitude, specifically through the transmission matrix method to predict and select the optimal thickness in advance to achieve the maximum amplification factor.

[0055] Furthermore, the transmission matrix method specifically includes:

[0056] MoS 2 The expression of reflectivity R of GaAs system is: in, Air and MoS 2 Film, MoS 2 The complex amplitude of the reflection coefficient at the interface between the film and GaAs, and the complex refractive index of each material are represents the complex refractive index in air, Indicates the first layer material, namely MoS 2 The complex refractive index, represents the complex refractive index of the second layer material, GaAs, n i represents the real part of the complex refractive index, κ i represents the imaginary part of the complex refractive index, δ i represents complex phase shift;

[0057] After the pump pulse is excited, the real part n and imaginary part κ of the complex refractive index change, which leads to the change of reflectivity R. 2 Medium ΔR / R 0 With Δn / n 0 and Δκ / κ 0 The changes in MoS 2 Thickness change affects differential reflectivity ΔR / R 0 The numerical value of (ΔR / R 0 ) / (Δn / n 0 ) slope characterizes the magnitude of coherent acoustic phonon oscillation, n 0 , κ 0 and R 0 are the parameters of n, κ and R under equilibrium conditions, ΔR, Δn, Δκ represent the changes of n, κ and R;

[0058] Get MoS 2 / GaAs system (ΔR / R 0 ) / (Δn / n 0 ) slope with MoS 2 The relationship between the thickness change and the peak value of the coherent acoustic phonon signal can be obtained. 2 thickness.

[0059] Furthermore, MoS 2 When the thickness is 80nm, MoS 2 / GaAs system coherent acoustic phonon signal reaches a peak.

[0060] Using MoS 2 Enhanced MoS 2 The device for detecting coherent acoustic phonon signals in a GaAs system may further include other components; however, since these components are irrelevant to the contents of the embodiments of the present disclosure, their illustration and description are omitted here.

[0061] A method using MoS 2 Enhanced MoS 2 The specific working process of the device for coherent acoustic phonon signals in the MoS / GaAs system is referred to the above 2Enhanced MoS 2 The description of the embodiment of the method for detecting coherent acoustic phonon signals in a GaAs system will not be repeated here.

[0062] Based on the above embodiments, the use of MoS 2 Enhanced MoS 2 / GaAs system, using MoS 2 As a transducer to amplify coherent acoustic phonons in GaAs materials, it can also be tuned by MoS 2 The thickness of MoS is controlled 2 / GaAs system coherent acoustic phonon amplification, in MoS 2 When the thickness is greater than 40nm, the signal can be amplified, and the optimal thickness can be predicted and selected in advance through the transmission matrix method to achieve the maximum amplification factor, which is convenient for data extraction and more conducive to the lossless extraction of precise information such as defects of semiconductor materials such as chips.

[0063] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A method for enhancing coherent acoustic phonon signals in a MoS2 / GaAs system using MoS2, characterized in that: include: MoS2 is used as a transducer to amplify the coherent acoustic phonons in the GaAs material, and the amplification amplitude of the coherent acoustic phonon signal in the MoS2 / GaAs system is controlled by adjusting the thickness of MoS2, wherein the thickness of MoS2 is 40nm-130nm.

2. The method for enhancing the coherent acoustic phonon signal in the MoS2 / GaAs system using MoS2 according to claim 1, characterized in that: The amplification factor of the coherent acoustic phonons in the MoS2 / GaAs system is controlled by adjusting the MoS2 thickness, and the optimal thickness is predicted and selected in advance by a transmission matrix method to achieve the maximum amplification factor.

3. The method for enhancing the coherent acoustic phonon signal in the MoS2 / GaAs system using MoS2 according to claim 2, characterized in that: The transmission matrix method specifically includes: The expression of reflectivity R of MoS2 / GaAs system is: in, They are the complex amplitudes of the reflection coefficients at the interfaces of air and MoS2 film, and MoS2 film and GaAs, and the complex refractive index of each material is represents the complex refractive index in air, represents the complex refractive index of the first layer material, i.e., MoS2, represents the complex refractive index of the second layer material, GaAs, n i represents the real part of the complex refractive index, κ i represents the imaginary part of the complex refractive index, δ i represents complex phase shift; After the pump pulse is excited, the real part n and imaginary part κ of the complex refractive index change, which leads to the change of the reflectivity R. By comparing the changes of ΔR / R0 with Δn / n0 and Δκ / κ0 in MoS2 of different thicknesses, it is known that the change of MoS2 thickness affects the numerical value of the differential reflectivity ΔR / R0. The slope of (ΔR / R0) / (Δn / n0) is used to characterize the size of the coherent acoustic phonon oscillation. n0, κ0 and R0 are the parameters of n, κ and R under equilibrium conditions. ΔR, Δn, Δκ represent the changes of n, k and R. The relationship between the slope of (ΔR / R0) / (Δn / n0) and the thickness of MoS2 in the MoS2 / GaAs system is obtained, so as to obtain the MoS2 thickness when the coherent acoustic phonon signal reaches the peak value.

4. The method for enhancing the coherent acoustic phonon signal in the MoS2 / GaAs system using MoS2 according to claim 1, characterized in that: When the MoS2 thickness is 80nm, the coherent acoustic phonon signal of the MoS2 / GaAs system reaches its peak.

5. A device for enhancing coherent acoustic phonon signals in a MoS2 / GaAs system using MoS2, characterized in that: The device is configured to: MoS2 is used as a transducer to amplify the coherent acoustic phonons in the GaAs material, and the amplification amplitude of the coherent acoustic phonon signal in the MoS2 / GaAs system is controlled by adjusting the thickness of MoS2, wherein the thickness of MoS2 is 40nm-130nm.

6. The device for enhancing the coherent acoustic phonon signal in the MoS2 / GaAs system using MoS2 according to claim 5, characterized in that: The coherent acoustic phonon amplification amplitude of the MoS2 / GaAs system is controlled by adjusting the MoS2 thickness, and specifically, the optimal thickness is predicted and selected in advance through the transmission matrix method to achieve the maximum amplification factor.

7. The device for enhancing the coherent acoustic phonon signal in the MoS2 / GaAs system using MoS2 according to claim 6, characterized in that: The transmission matrix method specifically includes: The expression of reflectivity R of MoS2 / GaAs system is: in, They are the complex amplitudes of the reflection coefficients at the interfaces of air and MoS2 film, and MoS2 film and GaAs, and the complex refractive index of each material is represents the complex refractive index in air, represents the complex refractive index of the first layer material, i.e., MoS2, represents the complex refractive index of the second layer material, GaAs, n i represents the real part of the complex refractive index, k i represents the imaginary part of the complex refractive index, δ i represents complex phase shift; After the pump pulse is excited, the real part n and imaginary part k of the complex refractive index change, which leads to the change of the reflectivity R. By comparing the changes of ΔR / R0 with Δn / n0 and Δκ / κ0 in MoS2 of different thicknesses, it is known that the change of MoS2 thickness affects the numerical value of the differential reflectivity ΔR / R0. The slope of (ΔR / R0) / (Δn / n0) is used to characterize the size of the coherent acoustic phonon oscillation. n0, κ0 and R0 are the parameters of n, κ and R under equilibrium conditions. ΔR, Δn, Δκ represent the changes of n, κ and R. The relationship between the slope of (ΔR / R0) / (Δn / n0) and the thickness of MoS2 in the MoS2 / GaAs system is obtained, so as to obtain the MoS2 thickness when the coherent acoustic phonon signal reaches the peak value.

8. The device for enhancing the coherent acoustic phonon signal in the MoS2 / GaAs system using MoS2 according to claim 5, characterized in that: When the MoS2 thickness is 80nm, the coherent acoustic phonon signal of the MoS2 / GaAs system reaches its peak.

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