Method for grading and discriminating interfacial interaction strength of type-ii transition metal chalcogenide heterojunction based on multi-dimensional optical information

Abstract

The application provides a type II transition metal chalcogenide heterojunction interlayer interaction strength grading discrimination method based on multi-dimensional optical information, and belongs to the field of two-dimensional semiconductor heterojunction optical characterization and optoelectronic device analysis; the problems of single optical criterion in the prior art being easy to fail in different coupling stages and lacking a unified discrimination framework are solved; the method obtains multi-dimensional optical information of the heterojunction; a first criterion parameter for representing the change relationship of the overall photoluminescence intensity of the heterojunction relative to the constituent single-layer material is constructed based on photoluminescence intensity imaging, a second criterion parameter for representing the interlayer light emission contribution relationship in the photoluminescence spectrum of the heterojunction is constructed based on the photoluminescence spectrum, and a third criterion parameter for representing the interlayer charge transfer efficiency of the heterojunction is constructed based on the time-resolved dynamic response curve; the criterion parameters of the application can be adaptively switched, so that continuous grading discrimination of the interlayer interaction strength of the heterojunction is realized.

Description

Technical Field

[0001] This application relates to the field of optical characterization of two-dimensional semiconductor heterojunctions and analysis of optoelectronic devices, and in particular to a method for classifying and judging the interlayer interaction intensity of type II transition metal chalcogenide heterojunctions based on multidimensional optical information. Background Technology

[0002] With the development of the application of two-dimensional transition metal chalcogenide materials in optoelectronic devices, the performance of thin-layer devices based on type II transition metal chalcogenide heterojunctions has shown significant differences. One of the main reasons is that the interlayer interaction strength is uncertain during the material preparation process, which affects the carrier migration efficiency and exciton recombination behavior. Therefore, it is necessary to effectively characterize the interlayer interaction strength.

[0003] In existing technologies, methods for determining the interlayer interaction strength of type II transition metal chalcogenide heterostructures mainly fall into two categories: optical methods and non-optical methods. Non-optical methods primarily include atomic force microscopy (AFM) and transmission electron microscopy (TEM). These methods can obtain information such as the layer thickness or local electronic states of the heterostructure, thereby reflecting the interlayer interaction strength. However, the interlayer coupling strength is mainly determined by carrier migration and exciton dynamics, and there is no direct correlation between the two. Therefore, it is difficult to quantitatively or hierarchically determine the interlayer interaction strength.

[0004] In contrast, optical methods can reflect interlayer interactions from the perspective of carrier recombination processes. Common methods include steady-state measurements based on photoluminescence spectral characteristics and exciton dynamics measurements based on time-resolved techniques. The former characterizes interlayer interactions by analyzing the spectral contributions of different components of luminescence intensity, while the latter reflects carrier transfer and recombination mechanisms through exciton relaxation processes. However, these methods typically exhibit good sensitivity under specific conditions or within a certain coupling range. Due to the differences in the physical processes reflected by different measurement methods, their applicability is limited. A single criterion is difficult to maintain effectiveness across different interlayer interaction intensities, and when interlayer interactions change, the original criterion often becomes invalid or its discriminative ability decreases. Summary of the Invention

[0005] To address the issues of existing optical technologies where single optical criteria are prone to failure at different coupling stages and lack a unified discrimination framework, this application proposes a hierarchical discrimination method for the interlayer interaction intensity of type II transition metal chalcogenide heterostructures based on multidimensional optical information.

[0006] The technical solution adopted in this application is as follows: a method for classifying and discriminating the interlayer interaction intensity of type II transition metal chalcogenide heterostructures based on multidimensional optical information is proposed, including the following steps:

[0007] Step 1: Perform optical measurements on the heterojunction of the type II transition metal chalcogenide to be tested and its constituent monolayer material to obtain multidimensional optical information including at least photoluminescence intensity imaging, photoluminescence spectrum and time-resolved exciton dynamics response curve;

[0008] Step 2: Construct a first criterion parameter A based on photoluminescence intensity imaging to characterize the relationship between the overall photoluminescence intensity of the heterostructure and its constituent monolayer material, and construct a corresponding discriminant effectiveness index R based on the first criterion parameter A. A This is used to evaluate the discriminative reliability of the first criterion parameter A; when the discriminative effectiveness index R... A When the preset threshold condition is met, the interaction state between heterojunction layers is determined according to the value of the first criterion parameter A;

[0009] Step 3: When the first criterion parameter A does not meet the corresponding discrimination condition, a second criterion parameter B is constructed based on the photoluminescence spectrum to characterize the interlayer luminescence contribution relationship in the photoluminescence spectrum of the heterojunction, and a corresponding discrimination effectiveness index R is constructed based on the second criterion parameter B. B This is used to evaluate the discriminative reliability of the second criterion parameter B; when the discriminative effectiveness index R... B When the preset threshold condition is met, the interaction state between heterojunction layers is determined according to the value of the second criterion parameter B;

[0010] Step 4: When the second criterion parameter B does not meet the corresponding discrimination condition, a third criterion parameter C is constructed based on the time-resolved dynamic response curve to characterize the charge transfer efficiency between heterojunction layers, and a corresponding discrimination effectiveness index R is constructed based on the third criterion parameter C. C It is used to evaluate the discrimination reliability of the third criterion parameter C; and to further discriminate the interaction state between heterojunction layers based on the value of the third criterion parameter C.

[0011] The interaction states between the heterojunction layers include at least three types: a first type, a second type, and a third type.

[0012] Furthermore, the first criterion parameter A is constructed based on the difference between the overall photoluminescence intensity of the heterojunction and the comprehensive photoluminescence intensity of its constituent monolayer materials, wherein the comprehensive photoluminescence intensity is the sum of the photoluminescence intensities of the charge donor layer and the charge acceptor layer constituting the heterojunction.

[0013] Furthermore, the second criterion parameter B is constructed based on the intensity relationship of the characteristic emission peaks of the charge donor layer and the charge acceptor layer in the heterojunction photoluminescence spectrum.

[0014] Furthermore, the third criterion parameter C is constructed based on the difference in photoluminescence intensity between the zero-delay region and the long-delay region in the time-resolved exciton dynamics response curve.

[0015] Furthermore, the discriminant effectiveness index R A , discriminant effectiveness index R B and the discriminant effectiveness index R C These are the parameters obtained after normalizing the corresponding criterion parameters relative to statistical fluctuations, system noise, or measurement errors.

[0016] Furthermore, the first type of state corresponds to the weak interaction state where interlayer carrier transfer is restricted, the second type of state corresponds to the situation where interlayer interaction is further enhanced but still at a moderate coupling level, and the third type of state corresponds to the strong interlayer interaction state.

[0017] Furthermore, when the first criterion parameter A is greater than zero, it indicates that the overall photoluminescence intensity of the heterojunction is higher than the comprehensive photoluminescence intensity of its constituent monolayer materials, corresponding to the first type of state;

[0018] When the discrimination capability of the first criterion parameter A decreases, the interaction state between heterojunction layers is further discriminated based on the second criterion parameter B; when the characteristic emission peak corresponding to the charge donor layer in the heterojunction photoluminescence spectrum can still be effectively distinguished, the second criterion parameter B is significantly non-zero, corresponding to the second type of state.

[0019] When the second criterion parameter B gradually approaches zero and its discrimination ability decreases, it indicates that the characteristic emission peak corresponding to the charge donor layer has almost disappeared. At this time, the interaction state between heterojunction layers is further discriminated based on the third criterion parameter C.

[0020] When the third criterion parameter C is greater than zero, it indicates that the photoluminescence intensity near the zero-delay region in the time-resolved exciton dynamics response curve is weakened, which corresponds to the second type of state.

[0021] When the third criterion parameter C is less than zero, it indicates that the photoluminescence intensity near the zero-delay region in the time-resolved exciton dynamics response curve is enhanced, corresponding to the third type of state.

[0022] Furthermore, the time-resolved exciton dynamics response curves were obtained through pump-probe photoluminescence measurements.

[0023] Furthermore, the heterostructure of the type II transition metal chalcogenide to be tested is a van der Waals heterostructure prepared by mechanical exfoliation stacking and chemical vapor deposition.

[0024] Furthermore, the excitation source in the optical measurement adopts continuous laser or pulsed laser, and the excitation wavelength is selected according to the material bandgap of the heterojunction of the type II transition metal chalcogenide to be measured; during the measurement process, the excitation power, integration time and spot size are controlled to ensure the comparability between heterojunctions of different type II transition metal chalcogenides to be measured; and background subtraction and system response correction are performed on the acquired photoluminescence intensity image.

[0025] The advantages of this application compared to existing technologies are as follows: This application constructs a multi-stage discrimination system by acquiring the photoluminescence intensity, photoluminescence spectrum, and time-resolved exciton dynamics response information of the type II transition metal chalcogenide heterojunction sample and its constituent monolayer materials. By evaluating the discrimination effectiveness index corresponding to each criterion parameter, the system automatically switches to the next criterion when the current criterion fails to meet the discrimination conditions, thus forming a progressive discrimination mechanism based on multi-dimensional optical information, achieving continuous hierarchical discrimination of the interlayer interaction strength of the heterojunction. In the first stage, criterion parameters are constructed based on photoluminescence intensity; when its discrimination ability is insufficient, in the second stage, criterion parameters are constructed based on the luminescence contribution of different components in the photoluminescence spectrum; when the spectral criterion fails, in the third stage, criterion parameters are constructed based on the photoluminescence intensity changes under different time delays in the time-resolved exciton dynamics response curve. Simultaneously, the effectiveness of each criterion parameter is evaluated by normalization, and the system adaptively switches to the next criterion when the current criterion fails. This application does not require complex structural design, is applicable to different type II transition metal chalcogenide heterojunction systems, and has good versatility and reliable discrimination. Attached Figure Description

[0026] The following description, in conjunction with the accompanying drawings, further illustrates this application:

[0027] Figure 1 This is a flowchart illustrating the classification process of this application;

[0028] Figure 2 This is a diagram of the optical measurement system for acquiring multidimensional optical information in this embodiment;

[0029] Figure 3 To verify the results of the photoluminescence intensity imaging experiment at different power levels in this embodiment, the imaging power of 3a is 185μW, the imaging power of 3b is 38μW, and the imaging power of 3c is 0.1μW.

[0030] Figure 4 To verify the experimental results of photoluminescence spectra under different annealing conditions collected in this embodiment;

[0031] Figure 5 To verify the experimental results of time-resolved exciton dynamics under different annealing conditions collected in this embodiment;

[0032] In the diagram: 1 is a femtosecond laser, 2 is a polarizing beam splitter, 3 is a polarizer, 4 is the first reflecting mirror, 5 is the first unpolarizing beam splitter, 6 is the second reflecting mirror, 7 is a quarter-wave plate, 8 is the third reflecting mirror, 9 is the fourth reflecting mirror, 10 is an electronically controlled stepper, 11 is a short-pass filter, 12 is a beam expander, 13 is a dichroic mirror, 14 is the objective lens, 15 is the sample, 16 is the second unpolarizing beam splitter, 17 is the fifth reflecting mirror, 18 is a spectrometer, 19 is the first lens, 20 is a pinhole camera, 21 is the second lens, 22 is the third lens, and 23 is a single-photon detector. Detailed Implementation

[0033] like Figures 1 to 5 As shown, this application provides a method for classifying the interlayer interaction intensity of type II transition metal chalcogenide heterostructures based on multidimensional optical information. This method is applicable to van der Waals heterostructures prepared by mechanical exfoliation stacking, chemical vapor deposition, or other methods. The method employs a progressive combination mechanism driven by the validity of criteria to classify the interlayer interaction intensity of heterostructures step by step. The criteria used include a first criterion parameter A, which characterizes the change in the overall photoluminescence intensity of the heterostructure relative to its constituent monolayer materials; a second criterion parameter B, which characterizes the interlayer luminescence contribution in the photoluminescence spectrum of the heterostructure; and a third criterion parameter C, which characterizes the interlayer charge transfer efficiency of the heterostructure.

[0034] The specific steps of this application method include:

[0035] Step 1: Perform optical measurements on the heterojunction of the type II transition metal chalcogenide to be tested and its constituent monolayer material to obtain multidimensional optical information such as photoluminescence intensity imaging, photoluminescence spectrum and time-resolved exciton dynamics response curve.

[0036] In optical measurements, the excitation source can be a continuous laser or a pulsed laser, and the excitation wavelength is selected according to the band gap of the material used in the heterojunction to be measured. During the measurement process, the excitation power, integration time, and spot size are controlled to ensure comparability between different heterojunction samples. Background subtraction and system response correction are performed on the acquired photoluminescence intensity images.

[0037] Step 2: Construct a first criterion parameter A based on photoluminescence intensity imaging. This first criterion parameter A is constructed based on the difference between the overall photoluminescence intensity of the heterojunction and the combined photoluminescence intensity of its constituent monolayers. When A > 0, it indicates that the photoluminescence intensity of the heterojunction is higher than the sum of the photoluminescence intensities of its constituent monolayers (i.e., the combined photoluminescence intensity), which usually corresponds to a weakly coupled state with limited interlayer carrier transfer, i.e., the first type of state. When A < 0, it indicates that the photoluminescence intensity of the heterojunction is lower than the sum of the photoluminescence intensities of its constituent monolayers, indicating enhanced interlayer carrier transfer, thereby suppressing the intralayer radiative recombination process. The corresponding interlayer interaction may be a subsequent state. Its specific expression is:

[0038] ;

[0039] In the formula, , These represent the photoluminescence intensities of the charge donor layer and charge acceptor layer that constitute the heterojunction, respectively. It is the overall photoluminescence intensity of the heterojunction region composed of the charge donor layer and the charge acceptor layer.

[0040] However, in actual measurements, the first criterion parameter A may be affected by system noise, measurement errors, or the non-uniformity of the heterojunction sample, making accurate judgment difficult when its value is close to zero. Therefore, the first criterion parameter A is normalized to construct a discrimination effectiveness index R. A The significance of the first criterion parameter A relative to the noise level is used to characterize the reliability of the first criterion parameter A. The discriminant effectiveness index R... A for:

[0041] ;

[0042] In the formula, It is the standard deviation of the first criterion parameter A obtained from different locations. When R A Greater than the preset threshold T A If the sign of parameter A is positive, the first criterion parameter is considered to have good discriminative reliability, and the interlayer interaction strength can be determined based on the sign of parameter A; otherwise, the first criterion parameter A is considered to have insufficient discriminative ability, and other criteria need to be introduced for further judgment. Threshold T A Determined based on the measured noise level, signal variation amplitude, or experimental statistical results.

[0043] The first type of state corresponds to a weakly interacting state where interlayer carrier transfer is restricted. Its formation mechanism is typically related to the asymmetric migration of interlayer carriers. Due to differences in band structure, Fermi level, or initial doping level between the two layers constituting the heterojunction, photoexcited electrons and holes exhibit asymmetric behavior during interlayer migration. One type of carrier is more prone to interlayer transfer, while the other remains primarily localized within its original layer, resulting in uneven spatial distribution of carriers across different layers. Under this condition, interlayer carrier recombination channels are suppressed, while radiative recombination within each monolayer is relatively dominant; that is, intralayer recombination efficiency is more dominant than interlayer recombination efficiency, thus enhancing the radiative recombination contribution within each monolayer. Consequently, the overall photoluminescence intensity of the heterojunction may be higher than the combined photoluminescence intensity of its constituent monolayers, as indicated by the first criterion parameter A > 0. In some embodiments, the aforementioned asymmetric migration process may also be related to factors such as interface barriers, band alignment, or local electric fields, but this application is not limited to a specific mechanism.

[0044] Step 3: When the first criterion parameter A does not meet the discrimination condition, the photoluminescence spectrum of the heterojunction in steady state is introduced, and the characteristic emission peaks of different components in the photoluminescence spectrum are numerically processed to obtain the spectral peak intensities of each component, thus constructing the second criterion parameter B:

[0045] ;

[0046] In the formula, , These represent the peak or integral intensity of the charge donor and charge acceptor layers in the heterojunction photoluminescence spectrum, respectively.

[0047] The second criterion parameter B is constructed based on the intensity relationship of the characteristic emission peaks of the charge donor layer and the charge acceptor layer in the photoluminescence spectrum of the heterojunction. If the interlayer charge transfer is incomplete, the spectrum of the charge donor layer is visible, i.e., the B value is significantly greater than 0, indicating that the interlayer interaction is of the second type. As the intensity of the interlayer interaction increases, the B value gradually decreases and approaches zero. At this point, it becomes difficult to further distinguish the intensity of the interlayer interaction based on the change in the spectral contribution relationship, leading to a decrease in the discriminative power of the second criterion parameter B.

[0048] Furthermore, in actual measurement processes, when the value of the second criterion parameter B approaches its discrimination limit, its physical meaning is easily affected by measurement noise and errors. To ensure the reliability of the discrimination results, referring to the processing method of the first criterion parameter A, the second criterion parameter B is normalized to construct the corresponding discrimination effectiveness index R. B This is used to evaluate its discriminative ability. Discriminative effectiveness index R B for:

[0049] ;

[0050] In the formula, This represents the statistical fluctuation of the second criterion parameter B under different sampling conditions. The discriminant effectiveness index R of the second criterion parameter B is also shown. B The determination method is the same as that of the first criterion parameter A, when R B Greater than the preset threshold T B If the threshold T is present, it has discriminative validity; otherwise, its discriminative ability is considered insufficient. B Determined based on the measured noise level, signal variation amplitude, or experimental statistical results.

[0051] The second type of state corresponds to a situation where interlayer interactions are further enhanced but still at a moderate coupling level. In this state, both electrons and holes can migrate to some extent between the two layers, enhancing the interlayer charge transfer process in the heterojunction, thus causing the overall photoluminescence intensity of the heterojunction to gradually decrease relative to its constituent monolayers. As interlayer interactions intensify, the overall photoluminescence intensity of the heterojunction gradually approaches the combined photoluminescence intensity of its constituent monolayers. At this point, the value of the first criterion parameter A is close to its critical region, making it susceptible to measurement noise and statistical fluctuations, leading to a decrease in its discrimination ability. Therefore, a second criterion parameter B is introduced to further discriminate the interlayer interactions. In this state, due to the presence of interlayer charge transfer, the spectral peak intensity corresponding to the charge donor layer gradually decreases, while the spectral peak intensity corresponding to the charge acceptor layer relatively increases (i.e., the luminescence contribution of the charge acceptor layer is relatively enhanced), but the characteristic emission peaks corresponding to the charge donor and charge acceptor layers in the heterojunction photoluminescence spectrum can still be identified. Therefore, the value of the second criterion parameter B is significantly greater than zero and can be used to characterize the degree of interlayer interaction in the second type of state. In pump-probe measurements of heterojunctions in this state, the pump light first excites electrons in both layers of material to high conduction band levels. When the probe light arrives before the electron relaxation is complete, it interacts with transient carriers in the type II transition metal chalcogenide heterojunction system, thereby affecting the photoluminescence response near zero delay. For heterojunctions in this state, although interlayer charge transfer is already significant, its transfer efficiency is still insufficient to completely offset processes such as probe light-induced nonradiative recombination enhancement. Therefore, the photoluminescence intensity near zero delay is weakened, corresponding to a third criterion parameter C being greater than zero. In some embodiments, the above process may also be related to factors such as interface states, band alignment, or local electric field distribution, but this application is not limited to a specific mechanism.

[0052] Step 4: When the second criterion parameter B does not meet the discrimination condition, the photoluminescence intensity change under different time delays is recorded using a pump-probe or time-resolved photoluminescence measurement system to obtain the time-resolved exciton dynamics response curve of the heterojunction. Based on the time-resolved exciton dynamics response curve, the third criterion parameter C is constructed:

[0053] ;

[0054] In the formula, , These represent the heterojunction photoluminescence intensities at the zero-delay time and the time exceeding the exciton relaxation time, respectively.

[0055] The exciton relaxation time is determined by the actual measurement temperature, the heterojunction sample, and the system resolution. The typical exciton relaxation time for a type II transition metal chalcogenide heterojunction is approximately a few picoseconds to tens of picoseconds. Photoluminescence intensity can be directly read from the detector or obtained by acquiring and integrating the photoluminescence spectrum.

[0056] The third criterion parameter C is constructed based on the difference in photoluminescence intensity between the zero-delay and long-delay regions in the time-resolved exciton dynamics response curve of pump-probe photoluminescence. It can characterize the time-resolved dynamics information of exciton relaxation features. When C > 0, it indicates that the photoluminescence response of the type II transition metal chalcogenide heterojunction system in the zero-delay region is weaker than that in the long-delay region, meaning that the interlayer charge transfer is insufficient to offset the enhancement effect of the probe light on the nonradiative recombination process, still corresponding to the second type of state. When C < 0, it indicates that the photoluminescence response of the type II transition metal chalcogenide heterojunction system in the zero-delay region is stronger than that in the long-delay region, indicating that the interlayer interaction is further enhanced, corresponding to the third type of state. When C does not meet the discrimination condition, the state of the type II transition metal chalcogenide heterojunction system can be determined by combining other criteria or further analysis.

[0057] Under the critical condition of transitioning from the second to the third state, as the interlayer charge transfer efficiency gradually increases, the zero-delay photoluminescence response characteristic in the time-resolved exciton dynamics response curve may approach the flipping critical state. At this point, the numerical change of the third criterion parameter C is easily affected by system noise, measurement conditions, or heterojunction sample inhomogeneity, resulting in insufficient discrimination significance. The above-mentioned criterion parameter processing method can be used to normalize it and construct a discrimination effectiveness index R. C To assess its discriminative reliability:

[0058] ;

[0059] In the formula, This represents the statistical fluctuation of the third criterion parameter C under different sampling conditions.

[0060] The third state corresponds to a strong interlayer interaction state, whose formation mechanism is usually related to the dominance of ultrafast interlayer charge transfer processes. In this state, electrons or holes in the heterojunction can efficiently migrate to another layer within an ultrafast timescale, thereby significantly altering the transient carrier distribution in the type II transition metal chalcogenide heterojunction system. Since efficient interlayer charge transfer reduces the accumulation of transient carriers in the original layer, the enhancement effect of the probe light on the nonradiative recombination process is significantly weakened. At this point, the role of the probe light is mainly to further excite carriers to participate in the radiative recombination process. Therefore, the photoluminescence response near zero delay changes from weakening to enhancement, manifested as a sign reversal in the time-resolved exciton dynamics response curve, corresponding to the third criterion parameter C being less than zero. In some embodiments, the above-mentioned dynamic behavior may also be related to factors such as interface states, local electric fields, many-body interactions, or carrier scattering processes, but this application is not limited to a specific dynamic model.

[0061] It should be noted that both the first and second types of states may exhibit a weakening photoluminescence intensity near zero delay in pump-probe photoluminescence measurements, corresponding to a third criterion parameter C being greater than zero. Therefore, it is difficult to accurately distinguish the different interlayer interaction states based solely on the kinetic response characteristics. Furthermore, different criterion parameters have different applicability and discrimination sensitivities at different stages of interlayer interaction: the first criterion parameter A is mainly applicable to situations where the overall photoluminescence intensity changes significantly under weak interaction conditions; the second criterion parameter B is mainly applicable to situations where the characteristic luminescence of different monolayer components in a heterojunction can be effectively distinguished; and the third criterion parameter C is mainly applicable to further discrimination of strong interlayer interaction states after the spectral criterion has nearly failed. Therefore, this application does not rely on a single optical parameter to judge interlayer interactions, but rather achieves continuous hierarchical discrimination of different interlayer interaction states through adaptive switching and joint analysis between different criterion parameters.

[0062] Furthermore, within the effective range of the three criteria, the strength of interlayer interactions should be determined based on the numerical values ​​of each criterion; the specific criteria can be determined through the above description. However, different systems are not directly comparable without calibration.

[0063] The method of this application will be further described below through a specific embodiment.

[0064] This embodiment uses a WS2 / WSe2 van der Waals heterojunction prepared by mechanical exfoliation as an example. The effectiveness of the discrimination method proposed in this application is verified by jointly measuring the steady-state photoluminescence intensity, photoluminescence spectrum, and time-resolved exciton dynamics response curves under different interlayer interaction conditions.

[0065] In this embodiment, a steady-state photoluminescence optical measurement system is specifically used to excite the WS2 / WSe2 van der Waals heterojunction sample and its constituent monolayer materials, and to acquire photoluminescence intensity imaging, photoluminescence spectra, and time-resolved exciton dynamics response curves. For example... Figure 2 As shown, the optical measurement system comprises three parts: a pump-probe module, a collection optical path, and a sample optical path. The pump-probe module outputs a laser pulse with a center wavelength of 532 nm and a pulse width of approximately 380 fs from a femtosecond laser 1. This pulse is split into two paths after passing through a polarization beam splitter 2, a polarizer 3, a first reflecting mirror 4, and a first unpolarized beam splitter 5. One path serves as the pump light, which is reflected by a quarter-wave plate 7 and a third reflecting mirror 8 before entering the first unpolarized beam splitter 5. The other path serves as the probe light, entering a fourth reflecting mirror 9 and then being reflected back to the first unpolarized beam splitter 5. An electrically controlled stepper 10 is installed in the probe optical path to adjust the time delay between the two paths. After the two beams are combined, they enter the sample optical path through a second reflecting mirror 6. In the sample optical path, the laser light passes through a short-pass filter 11, a beam expander 12, and a dichroic mirror 13 before being focused by an objective lens 14 onto the surface of the sample 15 (WS2 / WSe2 van der Waals heterojunction). The photoluminescence signal emitted by sample 15 enters the collecting optical path after passing through dichroic mirror 13. The collecting optical path is split into two paths by the second unpolarized beam splitter 16. One laser path is reflected by mirror 17 to spectrometer 18 to collect the photoluminescence spectrum. The other laser path is focused at pinhole 20 by first lens 19, then re-parallelized by second lens 21, and finally focused by third lens 22 onto single-photon detector 23 to collect photoluminescence intensity and obtain photoluminescence intensity imaging and time-resolved exciton dynamics response information. The photoluminescence intensity is the emission intensity at the corresponding position of sample 15 collected by single-photon detector 23.

[0066] In this embodiment, the photoluminescence intensity imaging, photoluminescence spectrum and time-resolved exciton dynamics response curve information of the WS2 / WSe2 van der Waals heterojunction sample and its constituent monolayer material are acquired simultaneously, and the first criterion parameter A, the second criterion parameter B and the third criterion parameter C are constructed based on the above information.

[0067] First, the photoluminescence intensity imaging results under different power conditions were obtained by adjusting the excitation power. Since the excitation laser introduces a weak thermal effect during the measurement process, it continuously fine-tunes the interlayer interaction state; therefore, different excitation power conditions correspond to different degrees of interlayer interaction. For example... Figure 3 As shown in 3a, under low interaction conditions, the overall photoluminescence intensity of the heterojunction region is higher than the comprehensive photoluminescence intensity of its constituent monolayer material, corresponding to the first criterion parameter A being greater than zero, and is thus determined to be a first-type state.

[0068] Subsequently, the WS2 / WSe2 van der Waals heterojunction samples were subjected to thermal annealing treatment, and then respectively... Figure 4 , Figure 5 The steady-state photoluminescence spectra and time-resolved exciton kinetic response curves are shown in the figure before annealing and under different annealing temperatures. Figure 4 As shown, when the annealing temperature is below 17℃, the characteristic emission peak corresponding to WSe2 can still be distinguished in the photoluminescence spectrum of the WS2 / WSe2 van der Waals heterojunction sample, indicating that the emission contribution of the charge donor layer still exists. At this time, the second criterion parameter B is significantly greater than zero, corresponding to the second type state. Its time-resolved exciton dynamics response curve is shown in Figure 1. Figure 5 As shown in the preceding theoretical analysis, the zero-delay region weakens. As the annealing temperature further increases, the characteristic peak corresponding to WSe2 gradually weakens and becomes indistinguishable, indicating that the interlayer charge transfer is further enhanced, leading to a significant suppression of radiative recombination in the charge donor layer. At this point, the second criterion parameter B gradually approaches zero, and its discriminative ability decreases.

[0069] like Figure 5 As shown, the pump-probe time-resolved exciton dynamics response curves before annealing and under different annealing temperatures are analyzed. The results show that after the emission peak of the charge donor layer becomes indistinguishable near 170℃, the time-resolved exciton dynamics response curve gradually changes from weakening to strengthening near the zero-delay region, corresponding to the third criterion parameter C gradually changing from greater than zero to less than zero. When C is less than zero, it indicates that the interlayer charge transfer process can dominate the transient dynamics behavior of the WS2 / WSe2 van der Waals heterojunction system, corresponding to the third state.

[0070] The above embodiments demonstrate that this application, by constructing a multi-stage criterion system based on photoluminescence intensity, photoluminescence spectrum, and time-resolved exciton dynamics response curves, and combining this with a criterion effectiveness index to achieve adaptive switching between different criteria, can realize continuous hierarchical discrimination of the interlayer interaction strength of type II transition metal chalcogenide heterostructures. Simultaneously, through the discrimination effectiveness index R... A R B and R C Evaluating the reliability of criteria at each stage can effectively avoid misjudgment caused by the failure of a single optical criterion in the critical coupling region. This embodiment does not further limit the discrimination effectiveness index, but discrimination bias or decreased effectiveness of the criterion can be observed in some critical states; these situations do not constitute a limitation on this embodiment.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for classifying and discriminating the interlayer interaction intensity of type II transition metal chalcogenide heterostructures based on multidimensional optical information, characterized in that: Includes the following steps: Step 1: Perform optical measurements on the heterojunction of the type II transition metal chalcogenide to be tested and its constituent monolayer material to obtain multidimensional optical information including at least photoluminescence intensity imaging, photoluminescence spectrum and time-resolved exciton dynamics response curve; Step 2: Construct a first criterion parameter A based on photoluminescence intensity imaging to characterize the relationship between the overall photoluminescence intensity of the heterostructure and its constituent monolayer material, and construct a corresponding discriminant effectiveness index R based on the first criterion parameter A. A , used to evaluate the discriminative reliability of the first criterion parameter A; When the discriminant effectiveness index R A When the preset threshold condition is met, the interaction state between heterojunction layers is determined according to the value of the first criterion parameter A; Step 3: When the first criterion parameter A does not meet the corresponding discrimination condition, a second criterion parameter B is constructed based on the photoluminescence spectrum to characterize the interlayer luminescence contribution relationship in the photoluminescence spectrum of the heterojunction, and a corresponding discrimination effectiveness index R is constructed based on the second criterion parameter B. B , used to evaluate the discriminative reliability of the second criterion parameter B; When the discriminant effectiveness index R B When the preset threshold condition is met, the interaction state between heterojunction layers is determined according to the value of the second criterion parameter B; Step 4: When the second criterion parameter B does not meet the corresponding discrimination condition, a third criterion parameter C is constructed based on the time-resolved dynamic response curve to characterize the charge transfer efficiency between heterojunction layers, and a corresponding discrimination effectiveness index R is constructed based on the third criterion parameter C. C This is used to evaluate the discriminative reliability of the third criterion parameter C; The interaction state between heterojunction layers is further determined based on the value of the third criterion parameter C. The interaction states between the heterojunction layers include at least three types: a first type, a second type, and a third type.

2. The method for classifying and discriminating the interlayer interaction intensity of type II transition metal chalcogenide heterostructures based on multidimensional optical information according to claim 1, characterized in that: The first criterion parameter A is constructed based on the difference between the overall photoluminescence intensity of the heterojunction and the comprehensive photoluminescence intensity of its constituent monolayer materials, wherein the comprehensive photoluminescence intensity is the sum of the photoluminescence intensities of the charge donor layer and the charge acceptor layer constituting the heterojunction.

3. The method for classifying and discriminating the interlayer interaction intensity of type II transition metal chalcogenide heterostructures based on multidimensional optical information according to claim 2, characterized in that: The second criterion parameter B is constructed based on the intensity relationship of the characteristic emission peaks of the charge donor layer and the charge acceptor layer in the heterojunction photoluminescence spectrum.

4. The method for classifying and discriminating the interlayer interaction intensity of type II transition metal chalcogenide heterostructures based on multidimensional optical information according to claim 3, characterized in that: The third criterion parameter C is constructed based on the difference in photoluminescence intensity between the zero-delay region and the long-delay region in the time-resolved exciton dynamics response curve.

5. The method for classifying and discriminating the interlayer interaction intensity of type II transition metal chalcogenide heterostructures based on multidimensional optical information according to claim 1, characterized in that: The discriminant effectiveness index R A , discriminant effectiveness index R B and the discriminant effectiveness index R C These are the parameters obtained after normalizing the corresponding criterion parameters relative to statistical fluctuations, system noise, or measurement errors.

6. The method for classifying and discriminating the interlayer interaction intensity of type II transition metal chalcogenide heterostructures based on multidimensional optical information according to claim 4, characterized in that: The first type of state corresponds to a weak interaction state where interlayer carrier transfer is restricted; the second type of state corresponds to a situation where interlayer interaction is further enhanced but still at a moderate coupling level; and the third type of state corresponds to a strong interlayer interaction state.

7. The method for classifying and discriminating the interlayer interaction intensity of type II transition metal chalcogenide heterostructures based on multidimensional optical information according to claim 6, characterized in that: When the first criterion parameter A is greater than zero, it indicates that the overall photoluminescence intensity of the heterojunction is higher than the comprehensive photoluminescence intensity of its constituent monolayer materials, corresponding to the first type of state; When the discrimination capability of the first criterion parameter A decreases, the interaction state between heterojunction layers is further discriminated based on the second criterion parameter B; when the characteristic emission peak corresponding to the charge donor layer in the heterojunction photoluminescence spectrum can still be effectively distinguished, the second criterion parameter B is significantly non-zero, corresponding to the second type of state. When the second criterion parameter B gradually approaches zero and its discrimination ability decreases, it indicates that the characteristic emission peak corresponding to the charge donor layer has almost disappeared. At this time, the interaction state between heterojunction layers is further discriminated based on the third criterion parameter C. When the third criterion parameter C is greater than zero, it indicates that the photoluminescence intensity near the zero-delay region in the time-resolved exciton dynamics response curve is weakened, which corresponds to the second type of state. When the third criterion parameter C is less than zero, it indicates that the photoluminescence intensity near the zero-delay region in the time-resolved exciton dynamics response curve is enhanced, corresponding to the third type of state.

8. The method for classifying and discriminating the interlayer interaction intensity of type II transition metal chalcogenide heterostructures based on multidimensional optical information according to claim 4, characterized in that: The time-resolved exciton dynamics response curves were obtained through pump-probe photoluminescence measurements.

9. The method for classifying and discriminating the interlayer interaction intensity of type II transition metal chalcogenide heterostructures based on multidimensional optical information according to claim 1, characterized in that: The heterostructure of the type II transition metal chalcogenide to be tested is a van der Waals heterostructure prepared by mechanical exfoliation stacking and chemical vapor deposition.

10. The method for classifying and discriminating the interlayer interaction intensity of type II transition metal chalcogenide heterostructures based on multidimensional optical information according to claim 1, characterized in that: In optical measurements, the excitation source is either a continuous laser or a pulsed laser, and the excitation wavelength is selected according to the band gap of the material used in the heterojunction of the type II transition metal chalcogenide to be measured. During the measurement process, the excitation power, integration time, and spot size are controlled to ensure the comparability between heterojunctions of different type II transition metal chalcogenides to be measured. Background subtraction and system response correction are performed on the acquired photoluminescence intensity images.

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