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

Abstract

The present invention discloses a method and apparatus for enhancing coherent acoustic phonon signals in a MoS2 / GaAs system using MoS2. The method includes using MoS2 as a transducer to amplify coherent acoustic phonons in GaAs material, and controlling the amplification amplitude of the coherent acoustic phonon signals in the MoS2 / GaAs system by adjusting the MoS2 thickness, where the thickness is between 40nm and 130nm. The method uses a transfer matrix method to predict and select the optimal thickness in advance to maximize amplification, facilitating data extraction and enabling the lossless extraction of precise information such as defects in semiconductor materials such as chips.

Description

Technical Field

[0001] The present application relates to the field of detection and analysis technology, and in particular to a method and device for enhancing coherent acoustic phonon signals in a MoS2 / GaAs system using MoS2. Background Art

[0002] With the widespread adoption of emerging technologies such as artificial intelligence and 5G, the requirements for chip manufacturing technology and processes are increasing. However, detecting internal chip defects and process integrity has always been a difficult problem to overcome. Currently, various methods are used to inspect the interior of semiconductor chips, but all suffer from drawbacks such as insufficient resolution and limited detection depth. While optical methods can detect semiconductor defects, this also presents significant challenges due to the difficulty of light penetrating most semiconductor materials.

[0003] To overcome these problems, pump-probe technology can be used to excite coherent acoustic phonons within the semiconductor. By converting optical signals into acoustic signals, internal defect information can be detected, effectively circumventing the limitations of optical detection. In the study of time-domain coherent acoustic phonons, in order to more accurately analyze their characteristics, it is generally desirable to have a larger amplitude of the detected coherent acoustic phonons so that more useful information can be extracted. To this end, both detection and excitation methods can be used to enhance the amplitude of the detected coherent acoustic phonons, thereby improving detection accuracy and the richness of the information obtained.

[0004] From a detection perspective, the wavelength of the probe light directly affects the amplitude, frequency, and detection depth of coherent acoustic phonons. Shorter wavelengths generally increase the signal amplitude but may result in a shallower detection depth; longer wavelengths, on the other hand, increase the detection depth but may reduce the amplitude. This dependence indicates that the wavelength of the probe light not only affects the signal intensity but also changes the frequency of coherent acoustic phonons. Therefore, a trade-off between amplitude, frequency, and depth is necessary to optimize detection effectiveness. Summary of the Invention

[0005] In response to the above problems, the present invention provides a method and device for enhancing the coherent acoustic phonon signal in the MoS2 / GaAs system using MoS2, aiming to select appropriate thickness information to achieve the maximum amplification requirement for the coherent acoustic phonons.

[0006] The first aspect of the present invention is a method for enhancing the coherent acoustic phonon signal in the MoS2 / GaAs system using MoS2, comprising: using MoS2 as a transducer to amplify the coherent acoustic phonons in the GaAs material, and controlling the amplification amplitude of the coherent acoustic phonon signal in the MoS2 / GaAs system by adjusting the thickness of MoS2, wherein the thickness of MoS2 is 40nm-130nm.

[0007] A further technical solution of the present invention is: the amplification factor of the coherent acoustic phonons in the MoS2 / GaAs system is controlled by adjusting the MoS2 thickness, specifically by predicting and selecting the optimal thickness in advance through the transmission matrix method to achieve the maximum amplification factor.

[0008] A further technical solution of the present invention is: when the thickness of MoS2 is 80nm, the coherent acoustic phonon signal of the MoS2 / GaAs system reaches a peak value.

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

[0010] The expression of the reflectivity R of the MoS2 / GaAs system is: in, They are the complex amplitudes of the reflection coefficients at the interfaces between 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, namely 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 the 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 in turn leads to a change in the reflectivity R. By comparing the changes of ΔR / R0 with Δn / n0 and Δκ / κ0 in MoS2 with different thicknesses, it is known that the change in 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 in n, κ and R.

[0012] The relationship between the slope of (ΔR / R0) / (Δn / n0) and the MoS2 thickness in the MoS2 / GaAs system is obtained, thereby obtaining the MoS2 thickness when the coherent acoustic phonon signal reaches its peak.

[0013] A second aspect of the present invention provides a device for enhancing coherent acoustic phonon signals in a MoS2 / GaAs system using MoS2, wherein the device is configured to:

[0014] 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, where the thickness of MoS2 is 40nm-130nm.

[0015] The device is further configured to control the coherent acoustic phonon amplification amplitude of the MoS2 / GaAs system by adjusting the MoS2 thickness, specifically by predicting and selecting the optimal thickness in advance through a transmission matrix method to achieve maximum amplification.

[0016] The device is further configured such that: the transmission matrix method specifically includes:

[0017] The expression of the reflectivity R of the MoS2 / GaAs system is: in, They are the complex amplitudes of the reflection coefficients at the interfaces between 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, namely 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 the 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 in turn leads to a change in the reflectivity R. By comparing the changes of ΔR / R0 with Δn / n0 and Δκ / κ0 in MoS2 with different thicknesses, it is known that the change in 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 in n, κ and R.

[0019] The relationship between the slope of (ΔR / R0) / (Δn / n0) and the MoS2 thickness in the MoS2 / GaAs system is obtained, thereby obtaining the MoS2 thickness when the coherent acoustic phonon signal reaches its peak.

[0020] The device is further configured such that when the thickness of MoS2 is 80 nm, the coherent acoustic phonon signal of the MoS2 / GaAs system reaches a peak value.

[0021] The present invention provides a method and device for enhancing coherent acoustic phonon signals in a MoS2 / GaAs system using MoS2. The method uses MoS2 as a transducer to amplify coherent acoustic phonons in GaAs material, and can control the amplification factor of the coherent acoustic phonons in the MoS2 / GaAs system by adjusting the thickness of MoS2. When the thickness of MoS2 is greater than 40nm, the signal can be amplified. The transmission matrix method can be used to predict and select the optimal thickness in advance to achieve the maximum amplification factor, thereby facilitating data extraction and being more conducive to the lossless extraction of precise information such as defects in 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 disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 (a) is a graph showing the variation of ΔR / R0 with Δn / n0 in MoS2 / GaAs with a MoS2 thickness of 1-100 nm in an embodiment of the present invention;

[0024] Figure 1 (b) is a graph showing the relationship between the slope of (ΔR / R0) / (Δn / n0) and the MoS2 thickness in the MoS2 / GaAs system according to an embodiment of the present invention;

[0025] Figure 2 (a) is a comparison 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 of the coherent acoustic phonon oscillations of the three samples and bulk GaAs extracted in the embodiment of the present invention;

[0027] Figure 3 It is a comparison diagram of the Fast Fourier Transform (FFT) amplitudes corresponding to coherent acoustic phonon oscillations in MoS2 / GaAs samples with MoS2 thickness of 2nm, 4nm, and 80nm and bare GaAs in the embodiments of the present invention. DETAILED DESCRIPTION

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, rather than all structures.

[0029] Before discussing the exemplary embodiments in more detail, it should be mentioned 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 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 present invention provides a method and apparatus for enhancing coherent acoustic phonon signals in a MoS2 / GaAs system using MoS2, and provides the following embodiments:

[0031] From a pumping perspective, the main means of increasing 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 also faces the risk of sample damage. Using two-dimensional materials as photoacoustic transducers to transfer strain to samples that are difficult to directly excite can also increase the amplitude, making phonon excitation more efficient. At the same time, from a detection perspective, the main means of increasing the amplitude of coherent acoustic phonons includes 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, enabling an effective balance between experimental accuracy and sample protection under different conditions.

[0032] A method for enhancing coherent acoustic phonon signals in a MoS2 / GaAs system using MoS2, comprising:

[0033] 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, where the thickness of MoS2 is 40nm-130nm.

[0034] The coherent acoustic phonon amplification factor of the MoS2 / GaAs system is controlled by adjusting the MoS2 thickness. Specifically, the optimal thickness is predicted and selected in advance through the transfer matrix method to achieve the maximum amplification factor.

[0035] When the MoS2 thickness is 80nm, the coherent acoustic phonon signal of the MoS2 / GaAs system reaches its peak.

[0036] The transfer matrix method specifically includes:

[0037] The expression of the reflectivity R of the MoS2 / GaAs system is: in, They are the complex amplitudes of the reflection coefficients at the interfaces between 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, namely 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 the 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 in turn leads to a change in the reflectivity R. By comparing the changes of ΔR / R0 with Δn / n0 and Δκ / κ0 in MoS2 with different thicknesses, it is known that the change in 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 in n, κ and R.

[0039] The relationship between the slope of (ΔR / R0) / (Δn / n0) and the MoS2 thickness in the MoS2 / GaAs system is obtained, thereby obtaining the MoS2 thickness when the coherent acoustic phonon signal reaches its peak.

[0040] Specifically, MoS2 can be transferred to GaAs material at room temperature and pressure without affecting the chip itself, and the amplification of coherent acoustic phonons can be controlled by changing the thickness of the two-dimensional material MoS2. The transfer matrix method can be used to predict and explain how to choose the appropriate thickness information to achieve the maximum amplification of coherent acoustic phonons.

[0041] The transfer matrix method is an important mathematical tool widely used to analyze the propagation of waves or particles in complex media. It is particularly well-suited to addressing 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. By arranging the dielectric structure into layers and using a transfer matrix to describe the influence of each layer on the wave or particle, the transfer matrix method effectively simplifies the analysis process. The transfer matrix for each layer describes the interaction between waves or particles in that layer, and ultimately, 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, mirrors, and other optical devices. In the design of electronic devices, this method can effectively handle the layered structure of semiconductor materials, helping engineers optimize the electronic transmission characteristics of the device. Because the transfer matrix method can efficiently handle layered dielectric structures and provide a simplified mathematical framework for solving complex dielectric propagation problems, it has become an indispensable analytical tool in many fields.

[0043] In optical thin film research, properties such as light penetration depth, the real (n) and imaginary (κ) parts of the refractive index, and interface reflection are particularly critical. For optical thin films with a thickness less than or equal to the light penetration depth, their reflective properties are primarily determined by both the real and imaginary parts of the refractive index. The real part of the refractive index (n) represents the speed of light propagation in the material, while the imaginary part (κ) reflects the degree of light absorption. Due to multiple reflections in thin films at the air / film and film / substrate interfaces, these reflected beams interfere with each other, 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. The analytical expression for the reflectivity R of the MoS2 / GaAs system is as follows:

[0045]

[0046] in, and are the complex amplitudes of the reflection coefficients at the air / MoS2 film and MoS2 film / GaAs interfaces, respectively. The complex refractive index of each material is defined as and is the complex phase shift due to the change in optical path and absorption in the thin film or GaAs, d i represents the thickness of the i-th layer of material, and λ represents the wavelength of the detection light.

[0047] After the pump pulse excitation, the refractive index n and extinction coefficient κ of the film will change, which will lead to a change in the reflectivity R. It is expressed as: n = n0 + Δn, κ = κ0 + Δκ, R = R0 + ΔR, where n0, κ0 and R0 are parameters under equilibrium conditions. In order to better understand the relationship between differential reflection (ΔR / R0) and refractive index change (Δn / n0 and Δκ / κ0), under the condition of changing the thickness of the MoS2 material in the double-layer sample, Δn / n0 = -0.02, -0.01, 0, 0.01, 0.02 or Δκ / K0 = -0.02, -0.01, 0, 0.01, 0.02 are respectively introduced. Using formula (1), the relationship between ΔR / R0 as a function of Δn / n0 and Δκ / κ0 can be plotted, as shown in the following example: Figure 1 As shown in (a).

[0048] By comparing the changes of ΔR / R0 with Δn / n0 and Δκ / κ0 in MoS2 samples of different thicknesses, it can be found that the change of MoS2 thickness does affect the numerical value of the differential reflectivity ΔR / R0. Δn / n0 and Δκ / κ0 represent the percentage changes of the real and imaginary parts of the complex refractive index, respectively. Then, at this time, the function line segment of ΔR / R0 is derived as Δn / n0 and Δκ / κ0 to obtain the slope of the line segment. This slope corresponds to the same pump laser exciting samples of different thicknesses, changing the degree of the sample's refractive index, and then corresponding to the degree of change in the reflected signal, which corresponds to the changing trend of the signal ΔR / R in the experiment. Therefore, the slope of (ΔR / R0) / (Δn / n0) can characterize the size of the coherent acoustic phonon oscillation. The change in the slope of the resulting line segment is shown as follows: Figure 1 As shown in (b): It can be seen that when the MoS2 is about 1-40nm, the slope of (ΔR / R0) / (Δn / n0) is basically unchanged, so the coherent acoustic phonon amplitude is basically unchanged. As the thickness of MoS2 gradually increases, the slope of (ΔR / R0) / (Δn / n0), that is, the coherent acoustic phonon amplitude, first increases, then reaches a peak, and then gradually decreases.

[0049] To verify the correctness of the transmission matrix, the inventors constructed MoS2 / GaAs heterojunctions with different MoS2 thicknesses at room temperature and pressure, and used pump-probe technology to excite and detect the coherent acoustic phonon oscillation signals of the heterojunction, selecting the appropriate MoS2 thickness to 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 coherent acoustic phonon oscillations of MoS2 / GaAs and pure GaAs corresponding to MoS2 at 2nm, 4nm, and 80nm are further extracted, as shown in Figure 2. Figure 2(b) When the coherent acoustic phonon signals of the sample and pure GaAs are subjected to Fast Fourier Transform (FFT) and compared in frequency, Figure 3 As shown, 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 the MoS2 material. A phase shift in the phase acoustic vibration is observed. This may be due to the phase matching of the surface acoustic waves between MoS2 and GaAs. The amplification of the GaAs phonon signal 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 poor bonding between MoS2 and the GaAs material on the substrate, resulting 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 MoS2 / GaAs samples with 2nm and 4nm MoS2 thickness, the coherent acoustic phonons of GaAs are not only not enhanced, but even slightly weakened. However, in the MoS22 / GaAs sample with MoS2 at 80nm, the coherent acoustic phonon amplitude is significantly enhanced. In the MoS22 / GaAs sample with a MoS2 thickness greater than 80nm, the coherent acoustic phonon amplitude gradually weakens, and the amplitude tends to remain unchanged after 130nm. It can be seen that the simulation results obtained by the transmission matrix are consistent with the experimental results of the inventors. Therefore, by changing the thickness of the two-dimensional material MoS2 to achieve the regulation of the amplification of coherent acoustic phonons, and using the transmission matrix to predict the corresponding amplification law, it is meaningful to further observe the acoustic information inside the semiconductor for better regulation of the oscillation amplitude of the coherent acoustic phonons.

[0051] Another embodiment is a device for enhancing the coherent acoustic phonon signal in a MoS2 / GaAs system using MoS2. The device can execute the method for enhancing the coherent acoustic phonon signal in a MoS2 / GaAs system using MoS2 provided in any embodiment of the present invention, and has the corresponding functional modules and beneficial effects of the execution method. 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 a device for enhancing a coherent acoustic phonon signal in a MoS2 / GaAs system using MoS2 is configured as follows:

[0053] 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, where the thickness of MoS2 is 40nm-130nm.

[0054] Furthermore, the coherent acoustic phonon amplification amplitude of the MoS2 / GaAs system is controlled by adjusting the MoS2 thickness. Specifically, the optimal thickness is predicted and selected in advance through the transmission matrix method to achieve the maximum amplification factor.

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

[0056] The expression of the reflectivity R of the MoS2 / GaAs system is: in, They are the complex amplitudes of the reflection coefficients at the interfaces between 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, namely 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 the 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 in turn leads to a change in the reflectivity R. By comparing the changes of ΔR / R0 with Δn / n0 and Δκ / κ0 in MoS2 with different thicknesses, it is known that the change in 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 in n, κ and R.

[0058] The relationship between the slope of (ΔR / R0) / (Δn / n0) and the MoS2 thickness in the MoS2 / GaAs system is obtained, thereby obtaining the MoS2 thickness when the coherent acoustic phonon signal reaches its peak.

[0059] Furthermore, when the MoS2 thickness is 80nm, the coherent acoustic phonon signal of the MoS2 / GaAs system reaches a peak.

[0060] The apparatus for enhancing the coherent acoustic phonon signal in the MoS2 / GaAs system using MoS2 may further include other components. However, since these components are irrelevant to the content of the embodiments of the present disclosure, their illustration and description are omitted here.

[0061] The specific working process of a device for enhancing coherent acoustic phonon signals in a MoS2 / GaAs system using MoS2 is described in the above-mentioned method embodiment for enhancing coherent acoustic phonon signals in a MoS2 / GaAs system using MoS2, and will not be repeated here.

[0062] In summary, the above-mentioned embodiments provide a method and device for enhancing the coherent acoustic phonon signal in the MoS2 / GaAs system using MoS2. MoS2 is used as a transducer to amplify the coherent acoustic phonons in the GaAs material, and the amplification factor of the coherent acoustic phonons in the MoS2 / GaAs system can be controlled by adjusting the thickness of MoS2. When the thickness of MoS2 is greater than 40nm, the signal can be amplified, and the optimal thickness can be predicted and selected in advance by the transmission matrix method to achieve the maximum amplification factor, which facilitates data extraction and is more conducive to the lossless extraction of precise information such as defects in semiconductor materials such as chips.

[0063] Note that the above are only preferred embodiments of the present invention and the technical principles employed. 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 detail through the above embodiments, the present invention is not limited to the above embodiments and may include many other equivalent embodiments without departing from the concept of the present invention. 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 coherent acoustic phonons in GaAs material, and the amplification amplitude of the coherent acoustic phonon signal in the MoS2 / GaAs system is controlled by adjusting the MoS2 thickness, where the MoS2 thickness is 40nm-130nm; 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; The transmission matrix method specifically includes: The expression of the reflectivity R of the MoS2 / GaAs system is: in, They are the complex amplitudes of the reflection coefficients at the interfaces between 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, namely 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 the complex phase shift; After the pump pulse is excited, the real part n and imaginary part κ of the complex refractive index change, which in turn leads to a change in the reflectivity R. By comparing the changes of ΔR / R0 with Δn / n0 and Δκ / κ0 in MoS2 with 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 MoS2 thickness in the MoS2 / GaAs system is obtained, thereby obtaining the MoS2 thickness when the coherent acoustic phonon signal reaches its peak.

2. 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.

3. 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 coherent acoustic phonons in GaAs material, and the amplification amplitude of the coherent acoustic phonon signal in the MoS2 / GaAs system is controlled by adjusting the MoS2 thickness, where the MoS2 thickness is 40nm-130nm; The coherent acoustic phonon amplification amplitude of 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 maximum amplification; The transmission matrix method specifically includes: The expression of the reflectivity R of the MoS2 / GaAs system is: in, They are the complex amplitudes of the reflection coefficients at the interfaces between 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, namely 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 the complex phase shift; After the pump pulse is excited, the real part n and imaginary part κ of the complex refractive index change, which in turn leads to a change in the reflectivity R. By comparing the changes of ΔR / R0 with Δn / n0 and Δκ / κ0 in MoS2 with 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, k0 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 MoS2 thickness in the MoS2 / GaAs system is obtained, thereby obtaining the MoS2 thickness when the coherent acoustic phonon signal reaches its peak.

4. The device for enhancing coherent acoustic phonon signals in a MoS2 / GaAs system using MoS2 according to claim 3, 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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