Spectral measurement method based on mechanical Raman scattering effect

Abstract

The present invention discloses a spectral measurement method based on the mechanical Raman scattering effect. The method includes: coupling a plasmonic metal to the surface of a sample to be measured, so that the oscillator to be measured drives the plasmonic metal to generate periodic vibrations; controlling an excitation light to irradiate the plasmonic metal to generate surface plasmon resonance, and collecting the spectral signal of the generated inelastic scattered light, wherein the plasmonic optical cavity generated by the surface plasmon resonance vibrates synchronously with the oscillator to be measured. This method uses a mechanical oscillator or a lattice oscillator with the characteristics of a mechanical oscillator to drive the movement of the plasmonic metal to finally generate an inelastic scattered light signal. This process is not restricted by the optical selection rules of the sample to be measured. By combining mechanical coupling and optical measurement methods, it is used for mechanical vibration measurement and crystal structure characterization.

Description

Technical Field

[0001] The present invention relates to the field of spectroscopic measurement technologies, and particularly to a spectroscopic measurement method based on the mechanical Raman scattering effect. Background Art

[0002] High-precision vibration measurement has a wide range of application scenarios, covering various fields such as basic sciences, materials, geology, engineering, and military. Classical vibration spectroscopy techniques, including infrared absorption spectroscopy and Raman scattering spectroscopy, etc., are one of the most effective ways to measure the motion states of molecules or lattice atoms, and can provide displacement information with picometer-level accuracy.

[0003] However, since mechanical oscillators often do not have a non-zero electric dipole polarization tensor, these vibration processes cannot be directly measured by classical vibration spectroscopy methods. Taking the ultra-low-frequency shear phonons with mechanical oscillator characteristics in layered crystals as an example, due to the cancellation of the changes in polarizability between layers, ultra-low-frequency phonons with co-directional atomic layer motion in layered crystals often cannot generate radiation-active electric dipoles under the action of incident light. How to effectively measure non-optically active vibrations, including classical mechanical vibrations and lattice oscillator vibrations, at the sub-atomic scale and apply them to vibration measurement and crystal structure characterization is the main objective and starting point of the present invention, which will be elaborated from two aspects of mechanical vibration and crystal structure characterization respectively below.

[0004] There are various macroscopic mechanical vibrations carrying multiple information in human production and life. Mechanical vibration measurement plays an important role in sonar technology, acoustic wave weapons, geological exploration, ultrasonic imaging, building flaw detection, earthquake monitoring, and gravitational wave detection. With the continuous development of lasers, filter elements, area array inductively coupled sensors, etc., Raman spectroscopy has been used for fingerprint recognition and atomic precision characterization in basic scientific research, homeland security, environmental monitoring, biomedical research, and cultural relic identification. However, people have not yet found experimental evidence of good coupling between the above types of vibration signals and visible light. The mechanical Raman scattering spectroscopy technology proposed by the present invention will provide an effective solution for measuring mechanical vibrations through Raman spectroscopy.

[0005] On the other hand, taking the lattice shear oscillator of layered crystals as an example, we will demonstrate the implementation method and potential application scenarios of the mechanical Raman scattering technology. In layered crystals, the overall, periodic ultra-low-frequency vibration with atomic layers as units is called the interlayer vibration mode (including shear mode and breathing mode). Such lattice phonons not only reflect fingerprint information such as crystal structure, symmetry, force constant, and electron-phonon coupling strength, but also play a key role in the optical, electrical, magnetic, thermal, and mechanical properties of crystal materials such as luminescence, ultrafast interfacial charge transfer, and superconductivity through the electron-phonon coupling effect.

[0006] To date, more than 5,600 layered crystals have been discovered. Shear vibration phonon branches with co-directional atomic layer motion carry unique information about the global structure and hidden interfaces in the crystal structure. However, in most known layered crystals, according to the interlayer bond polarizability model, the absolute value of the change in the polarizability of such shear phonons is very small or zero (the electron-phonon coupling is extremely weak), so their signals cannot be experimentally measured by existing techniques. Through the implementation of various embodiments of the present invention, we will demonstrate the unique advantages of the mechanical Raman scattering technique in crystal structure characterization, especially in global crystal structure characterization and hidden interface detection.

[0007] The information disclosed in this background art section is only intended to enhance the overall understanding of the present invention and should not be regarded as an admission or any form of implication that this information constitutes prior art already known to those of ordinary skill in the art. Summary of the Invention

[0008] The object of the present invention is to provide a spectral measurement method based on the mechanical Raman scattering effect, which is used to solve the technical problems that the existing spectral measurement methods cannot achieve the measurement of the global structure of layered crystals, the detection of hidden interfaces, and the measurement of mechanical vibrations.

[0009] To achieve the above object, an embodiment of the present invention provides a spectral measurement method based on the mechanical Raman scattering effect, and the method includes:

[0010] Couple a plasmonic metal to the surface of the sample to be measured, so that the oscillator to be measured drives the plasmonic metal to generate periodic vibrations;

[0011] Control the excitation light to irradiate the plasmonic metal to generate surface plasmon resonance, and collect the spectral signal of the generated inelastic scattered light, wherein the plasmonic optical cavity generated by the surface plasmon resonance vibrates synchronously with the oscillator to be measured.

[0012] In one or more embodiments of the present invention, the incident laser frequency of the excitation light irradiating the surface of the plasmonic metal is adjustable, and the wavelength range of the incident laser generating plasmon resonance is 250 nm to 300,000 nm.

[0013] In one or more embodiments of the present invention, there is an energy transfer between the oscillator to be measured and the plasmonic metal, and the energy difference between the photon energy of the inelastic scattered light signal and the photon energy of the incident laser is equal to the product of the frequency of the oscillator to be measured and Planck's constant.

[0014] In one or more embodiments of the present invention, in the first-order approximation, the intensity of the inelastic scattered light signal is proportional to the square of the amplitude of the oscillator to be measured.

[0015] In one or more embodiments of the present invention, the plasmonic metal includes one or more of aluminum, gold, silver, copper, sodium, nickel, graphene, or an alloy thereof.

[0016] In one or more embodiments of the present invention, the plasmonic metal has a nanoscale undulating structure and a resonant excitation wavelength that matches the wavelength of the incident laser.

[0017] Compared with the prior art, the spectroscopic measurement method based on the mechanical Raman scattering effect according to the embodiments of the present invention uses the oscillator to be measured to drive the movement of the plasmonic metal to finally generate an inelastic scattered light signal. This process is not limited by the optical selection rules of the sample to be measured. By combining the mechanical coupling and optical measurement methods, it is used for mechanical vibration measurement and crystal structure characterization, and has the advantages of simple sample preparation steps, efficient signal acquisition, and low cost. Description of the Drawings

[0018] Figure 1 is a flowchart of a spectroscopic measurement method based on the mechanical Raman scattering effect according to an embodiment of the present invention;

[0019] Figure 2 is a schematic structural diagram of the coupling between the plasmonic metal and the oscillator to be measured in a spectroscopic measurement method based on the mechanical Raman scattering effect according to an embodiment of the present invention;

[0020] Figure 3 is a schematic diagram of the mechanical Raman scattering principle in a spectroscopic measurement method based on the mechanical Raman scattering effect according to an embodiment of the present invention;

[0021] Figure 4 is a schematic diagram of the results of the calculated and measured values of the resonant excitation wavelength of the nanoscale undulating plasmonic metal structure;

[0022] Figure 5 is a comparison diagram of the results of optical Raman testing and mechanical Raman testing of a multi-layer graphite crystal in a spectroscopic measurement method based on the mechanical Raman scattering effect according to an embodiment of the present invention;

[0023] Figure 6 is a comparison diagram of the results of mechanical Raman testing of graphite sheets with different numbers of layers in a spectroscopic measurement method based on the mechanical Raman scattering effect according to an embodiment of the present invention;

[0024] Figure 7 is a comparison diagram of the results of optical Raman testing and mechanical Raman testing of a multi-layer cubic boron nitride crystal in a spectroscopic measurement method based on the mechanical Raman scattering effect according to an embodiment of the present invention;

[0025] Figure 8It is a comparison diagram of the results of optical Raman testing and mechanical Raman testing on multilayer tungsten diselenide in the spectral measurement method based on the mechanical Raman scattering effect according to an embodiment of the present invention;

[0026] Figure 9 It is a schematic diagram of the results of detecting the crystal global quality characterization of different crystal samples based on the mechanical Raman scattering spectrum in the spectral measurement method based on the mechanical Raman scattering effect according to an embodiment of the present invention;

[0027] Figure 10 It is a schematic diagram of the results of testing heterojunctions and homojunctions constructed by layered crystals based on the mechanical Raman scattering spectrum in the spectral measurement method based on the mechanical Raman scattering effect according to an embodiment of the present invention. Detailed Embodiments

[0028] The present application will be described in detail below in conjunction with the various embodiments shown in the accompanying drawings. However, these embodiments do not limit the present application, and structural, method, or functional transformations made by those of ordinary skill in the art based on these embodiments are all included within the protection scope of the present application.

[0029] The terms "first", "second", "third", "fourth", etc. (if any) in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects and do not necessarily need to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprising" and "corresponding to" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0030] For the convenience of understanding, the nouns involved in the embodiments of the present application will be described first below.

[0031] Raman scattering: Raman scattering is a type of inelastic scattering effect that occurs when photons interact with matter. When an incident photon (with energy hν0) interacts with a molecule or lattice, the photon has a certain probability of losing or gaining an energy equal to the vibrational (or rotational) energy level (ω R ). The process in which the incident photon loses the corresponding energy is called Stokes scattering (Stokes scattering, E = ν0 - ω R), the process in which incident photons obtain corresponding energy is called anti-Stokes Raman scattering (E = ν0 - ω R ). Under thermal equilibrium conditions, the intensity ratio of Stokes scattering and anti-Stokes scattering depends on the system temperature T, i.e.: I anti-Stkes / I Stokes = exp(-hv i / k B T), where h is the Planck constant, v i is the vibrational energy ω R , k B is the Boltzmann constant, and T is the thermodynamic temperature.

[0032] Localized surface plasmon resonance: Under the action of incident light, free electrons on the surface of metal nanoparticles undergo periodic oscillations. Under specific incident light frequencies and polarization conditions, surface plasmon resonance occurs, and a plasmonic cavity is formed at the gap structure or the position with a small radius of curvature.

[0033] Layered crystals: The layers of the material are mainly connected by van der Waals forces, and the atoms within the layers are connected by covalent bonds. The single-layer thickness ranges from a single atomic layer to several atomic layers. A series of single layers assembled by a specific stacking method form a crystal material called layered crystals.

[0034] Lattice shear oscillator: Shear mode and breathing mode are two types of characteristic vibration modes in layered crystals. Taking the interlayer shear mode as an example, they are the in-plane relative motion modes of the entire atomic layer. According to the linear chain model and only considering the interaction between the nearest layers, each atomic layer can be regarded as a rigid sphere, and a layered material with N layers is simplified to a one-dimensional linear chain containing N rigid spheres, with a total of N - 1 ultra-low-frequency shear vibration modes.

[0035] Mechano-Raman scattering effect: Under the drive of a periodic vibrating mechanical oscillator (with a frequency of ω mech ), the plasmonic cavity undergoes synchronous vibration. Under resonance excitation conditions, photons in the plasmonic metal cavity will mechanically couple with the mechanical oscillator and generate inelastic scattering, ultimately generating scattered light signals with frequencies of ν0 ± ω mech . In the present invention, this new inelastic light scattering phenomenon is called mechano-Raman scattering (MRS), and its principle can be referred to Figure 3. In MRS, surface plasmons act as scattering media, focusing the incident light to greatly enhance the scattering efficiency, and demonstrating unique advantages in the characterization of lattice structures with mechanical propagation and vibration measurement.

[0036] In the commonly used preparation methods for the current characterization of molecular structures, the spectral methods mainly rely on optical Raman spectroscopy and infrared spectroscopy. When there are changes in polarizability and dipole moment, their spectral signals can be detected. These complementary spectroscopic methods have been widely used as powerful tools for studying molecular structures and chemical compositions in various fields such as materials, chemical engineering, environmental protection, and geology. However, due to the failure to directly provide the global information of crystal structures and hidden interface information, and not reflecting the mechanical transfer characteristics and vibration displacement information.

[0037] The aberration-corrected electron microscope can reflect the fine crystal structure at the atomic scale, but can only reflect the regional information of the sample, the sample preparation steps are cumbersome and complex, rely on extremely expensive equipment, have a slow detection speed, and are not suitable for vibration sensing.

[0038] Using the information of X-ray diffraction spectra, the determination of the phase of a conventional microscope can be achieved, and it can be judged whether there are large lattice defects inside the crystal, etc. It cannot judge local defects and is not suitable for vibration sensing.

[0039] The existing laser interference measurement method has achieved the measurement of femtometer-scale mechanical displacement, but the applicable system is very limited and is not yet suitable for layered crystal structures.

[0040] Traditional optomechanical microcavities have achieved the measurement of the vibration frequency and displacement of molecules, but it is difficult to apply to lattice systems.

[0041] The purpose of the present invention is to provide a spectral measurement method based on the mechanical Raman scattering effect. By means of the mechanical coupling effect between the surface plasmon cavity and the oscillator to be measured, a measurement technique that can be used for the global structure characterization, hidden interface detection, and ultra-high-precision vibration sensing of the sample to be measured (such as layered crystals) is provided, which will provide a new idea for high-precision (sub-picometer amplitude) and convenient mechanical vibration measurement.

[0042] Refer Figure 1 , an embodiment of the spectral measurement method based on the mechanical Raman scattering effect of the present application is introduced. In this embodiment, the method includes:

[0043] S101. Coupling a plasmonic metal to the surface of the sample to be measured, so that the oscillator to be measured drives the plasmonic metal to generate periodic vibrations.

[0044] Plasmonic metals refer to metals that can generate plasmon resonances under the excitation of pumping light. Processing such metal targets into the nanoscale yields corresponding plasmonic metals. In some embodiments, the metal targets of plasmonic metals can be one or an alloy of aluminum, gold, silver, copper, sodium, nickel, graphene. As Figure 4 shown in FIGS. 4a and 4b, the plasmonic metal has a nanoscale undulating structure and a resonance excitation wavelength matching the incident laser wavelength.

[0045] In some embodiments, exemplarily, the plasmonic metal can be processed into an ellipsoidal metal nanoisland structure or a metal nanodisc structure. Among them, the ellipsoidal metal nanoisland structure can be prepared by thermal evaporation, and the metal nanodisc structure can be precisely prepared by electron beam lithography combined with thermal evaporation.

[0046] Figure 2 The process of coupling the plasmonic metal with the oscillator to be measured is shown. In this embodiment, the nanoarray of the plasmonic metal is uniformly evaporated on the surface of the sample to be measured, and the morphology of the nanoarray of the plasmonic metal can be flexibly designed according to actual needs.

[0047] S102. Control the pumping light to irradiate the plasmonic metal to generate surface plasmon resonance, and collect the spectral signal of the generated inelastic scattered light, wherein the plasmonic optical cavity generated by the surface plasmon resonance vibrates synchronously with the oscillator to be measured.

[0048] In some embodiments, pumping light resonant with the plasmonic metal can be selected to excite the plasmonic metal to generate surface plasmon resonance and generate a plasmonic optical cavity. Under resonant excitation conditions, the photons in the plasmonic optical cavity will mechanically couple with the oscillator to be measured and generate an inelastic scattered light signal.

[0049] Collect and process this inelastic scattered light signal, and then obtain the measurement spectrum of the inelastic scattered light signal. Finally, based on this measurement spectrum of the inelastic scattered light signal, the structural characterization information and mechanical vibration information of the sample to be measured can be obtained. Among them, the structural characterization information of the sample to be measured includes its global structure and hidden interface information, and the mechanical vibration information includes the vibration frequency of the oscillator and mechanical transmission information.

[0050] In this embodiment, the frequency of the incident laser on the surface of the plasmonic metal is adjustable. Specifically referring to Figure 3 this, energy transfer occurs between the plasmonic optical cavity excited by the incident laser and the oscillator to be measured. During this process, the outgoing photons can obtain or give an energy of an oscillator, thereby realizing the controllable modulation of the incident laser frequency by the oscillator.

[0051] Exemplarily, the resonance response center of a 100-nm silver nanodisc is at 527 nm. Refer toFigure 4 .

[0052] During the excitation light excitation process, there is energy transfer between the oscillator to be measured and the plasmon metal, which causes an energy difference between the photon of the inelastic scattered light signal (outgoing photon) and the incident photon. The magnitude of this energy difference is equal to the product of the frequency of the oscillator to be measured and Planck's constant, that is, hv mech .

[0053] At the same time, in the first-order approximation, the intensity of the inelastic scattered light signal will be proportional to the square of the amplitude of the oscillator to be measured.

[0054] In some embodiments, the sample to be tested can be a multilayer crystal structure made of any one (homojunction) material of graphite, molybdenum sulfide, tungsten sulfide, molybdenum selenide, tungsten selenide, and boron nitride, or a combination of two or more (heterojunction) materials.

[0055] The following examples of measurements in some scenarios are used to verify the feasibility of the spectral measurement method based on the mechanical Raman scattering effect of the present invention.

[0056] 1) Different crystal samples were used as test samples to verify the spectral measurement method based on the mechanical Raman scattering effect of the present invention.

[0057] Common layered crystals include graphite, molybdenum sulfide, and hexagonal boron nitride crystals. The following is an exemplary introduction to the measurement process of global phonons of several different crystal samples.

[0058] ①Use layered graphite crystal as a crystal sample to measure its global phonon:

[0059] Optical Raman and mechanical Raman tests were performed on multilayer graphite crystals. The test results of optical Raman and mechanical Raman are compared. Figure 5 As shown, curve f is the test result of optical Raman, and curve g is the test result of mechanical Raman. Figure 5 It can be found that optical Raman is limited by the Raman selection law, and only the highest frequency shear phonons are measured, while mechanical Raman can measure all the shear phonons of the sample to be tested, where the Raman shift corresponds to the frequency of the lattice oscillator. This method can distinguish vibration displacements at the sub-picometer level.

[0060] ② Use graphene sheets with different numbers of layers as crystal samples to measure their global phonons:

[0061] like Figure 6As shown in the figure, in this embodiment, mechanical Raman tests were performed on graphite sheet layers with different numbers of layers, and it was found that the measured vibration frequencies were consistent with the theoretical values (calculated from the straight-chain model), and the signals of these shear phonons were invisible in ordinary ultra-low wavenumber Raman tests. Further, damping information on the mechanical force transfer of graphite sheet layers with different numbers of layers can be obtained by observing the change in the full width at half maximum with the number of layers.

[0062] ③ Using cubic boron nitride crystals as crystal samples to measure their global phonons:

[0063] Optical Raman tests and mechanical Raman tests were performed on multi-layer cubic boron nitride crystals, and the test results are compared as Figure 7 shown. It can be Figure 7 found that mechanical Raman can detect all shear phonons of the sample to be measured.

[0064] ④ Using the layered transition metal chalcogenide tungsten diselenide as a crystal sample to measure its global phonons:

[0065] Optical Raman and mechanical Raman tests were performed on multi-layer tungsten diselenide, and the test results are compared as Figure 8 shown. It can be Figure 8 found that the mechanical Raman scattering signal can be detected and is marked with triangles in the figure.

[0066] 2) Detecting the global quality characterization of crystals based on mechanical Raman scattering spectra.

[0067] In this embodiment, mechanical Raman scattering spectra are used to detect the lattice quality of primary graphite (Kish-graphite), two highly oriented pyrolytic graphites HOPGⅠ and HOPGⅡ.

[0068] Ag / G samples (Kish-graphiteh and HOPGⅠ) with uniform thickness in the optical photos were respectively selected for spatial imaging of MRS signals, and the corresponding imaging results are as Figure 9 a and Figure 9 b. After subtracting the baseline from the peak, the intensities of different vibration modes at the lowest frequency were normalized respectively. At the same time, the coefficient of variation was calculated based on the intensity values of all pixel points in the imaging area and represented by the value V in the lower left corner. This coefficient is not affected by the sampling range. The coefficient of variation and the normalization factor can jointly reflect the crystal quality. The larger the normalization factor, the higher the crystal quality, and the smaller the coefficient of variation, the more uniform. The crystal quality of HOPGⅠ is much lower than that of the Kish-graphite sample.

[0069] The imaging technique based on MRS can achieve the accurate positioning of defects in the lattice. Since the MRS signal only truthfully reflects the information of all atomic layers above the interface (defect), the position where the defect appears is determined through the MRS spectral data. To more clearly illustrate the advantages of MRS in crystal quality detection, a graphite sheet layer with large-area defects (a homojunction formed by artificially stacking defects) is constructed in the present invention, as Figure 9 shown in c, where nLG treated by oxygen plasma (3 min) is used as the bottom layer and mLG is used as the top layer to construct an (m + n)-layer homojunction.

[0070] MRS imaging is performed on three regions. In region ①, mLG exhibits the mechanical Raman signal of mLG; for region ③, during the upward propagation of the mechanical force, it encounters the top layer damaged by the plasma, resulting in the ineffective driving of the surface plasmon metal, so there is no MRS signal in this region; while for region ②, the transmission of the mechanical force of the bottom-layer material is blocked at the homojunction interface damaged by the plasma, and the mechanical force of the top-layer material is not affected, so MRS shows mLG, and the specific transmission process is as Figure 9 shown in d. Thus, it can be seen that the position of the defect can be determined through MRS.

[0071] To verify the ability of the MRS technique to distinguish natural defects in crystals, the present invention uses mechanical Raman scattering spectroscopy to perform spatial imaging of the MRS signal on the lattice quality of HOPGⅡ with moderate mosaic diffusion, and the imaging result is as Figure 9 shown in e. The position of the defect in HOPGⅡ is located through the MRS technique, that is, the dark area shown.

[0072] Thus, it can be seen that the global quality of the crystal can be characterized through the imaging technique of MRS.

[0073] 3) Detecting the hidden interface of layered crystals based on mechanical Raman scattering spectroscopy.

[0074] Perform MRS tests on the heterojunctions and homojunctions constructed from layered crystals, and the test results are as Figure 10 shown, where Figure 10 a is the signal of the heterojunction obtained by the test, Figure 10 Curves Ⅰ and Ⅱ in b are both signals of the heterojunction obtained by the test, and curves Ⅲ and Ⅳ are both signals of the homojunction obtained by the test.

[0075] The signal of the hidden interface and the phonon information of the entire crystal can be detected respectively using an excitation light of 532 nm. From Figure 10It can be known that for the 1LG / 3L-MoS2 heterojunction, the phenomenon that there is no MRS signal in the spectrum well reflects that the flexibility of monolayer graphene caused by the shear modulus can well hinder the transmission of the lattice shear force below. For the 1L-MoS2 / 6LG heterojunction, the appearance of the MRS signal well reflects that the rigidity of monolayer molybdenum disulfide caused by the shear modulus can well transmit the action of the lattice shear force below.

[0076] From Figure 10 It can be known from b that for the 3L-MoS2 / 4L-WSe2 heterojunction, the appearance of the MRS signals of the two lattices respectively indicates that this spectroscopic measurement method based on the mechanical Raman scattering effect can directly transmit the information of the hidden interface without being affected by the different lattice oscillators above. For the twisted and folded (10+10) layer graphite, the MRS signal presents the information of the overall lattice vibration, which cannot be achieved at all in ordinary optical Raman under the Van Hove singularity resonance.

[0077] It can be seen from this that the spectroscopic measurement method of MRS based on the mechanical Raman scattering effect well demonstrates the transmission of mechanical forces and quantum characteristics in the lattice.

[0078] There are various common characterizations of crystal structures at present. Among them, the spectroscopic methods are mainly optical Raman spectroscopy technology and infrared spectroscopy technology, which can obtain Raman-active and infrared-active signals respectively; the aberration-corrected electron microscope reflects the fine crystal structure at the atomic scale and has a sub-angstrom resolution; the vibration detection method based on the interference principle (Michelson interferometer) is widely used in the measurement of the small displacement and micro-vibration of macroscopic objects.

[0079] Comparing the above existing crystal structure and vibration measurement methods with the spectroscopic measurement method based on the mechanical Raman scattering effect of the present invention in terms of crystal structure measurement and vibration sensing measurement, the following conclusions can be drawn:

[0080] ① Classical optical Raman spectroscopy (traditional spectroscopic technology): In crystal structure measurement, it can reflect crystal structure information, measure local signals, and perform non-destructive detection, but it cannot be used for the global characterization of crystal structures; in vibration sensing measurement, it can detect the vibration and rotational energy levels of substance molecules, reflect the vibration form but not the mechanical transmission characteristics, and the measurement frequency range > 50 cm -1 , and there is no vibration displacement information.

[0081] ② Ultra-low wavenumber Raman spectroscopy: In crystal structure measurement, it can reflect crystal structure information, measure local signals or bulk phase signals, and perform non-destructive detection. In vibration sensing measurement, it can detect Raman-active interlayer vibrations or chain rotations, reflect the vibration form but not the mechanical transmission characteristics, and the frequency range < 50 cm -1 , and reflect the vibration displacement information.

[0082] ③Infrared spectroscopy (traditional spectroscopic technique): In crystal structure measurement, it can measure crystal quality characterization, obtain local signals, and perform non-destructive detection; in vibration sensing measurement, it can detect the vibration and rotational energy levels of molecular substances, reflecting the vibration form but not the mechanical transmission characteristics, nor the vibration displacement information.

[0083] ④Spherical aberration corrected transmission electron microscope: In crystal structure measurement, it can reflect the fine crystal structure at the atomic scale, with sub-angstrom resolution, and obtain local signals; it is destructive to the crystal structure and cannot be used for the global fine structure characterization of crystal structures; it is not applicable in vibration sensing measurement.

[0084] ⑤X-ray diffraction: In crystal structure measurement, it can accurately determine the crystal structure and stress of substances, perform accurate phase analysis, detect whether there are large defects inside the crystal, obtain overall signals, and perform non-destructive detection. Although it can reflect overall signals, it is not applicable to small lattice defects; it is not applicable in vibration sensing measurement.

[0085] ⑥Vibration detection method based on the interference principle (Michelson interferometer): Not applicable to crystal structure measurement; in vibration sensing measurement, it can measure the vibration and displacement of macroscopic objects and is not applicable to crystal measurement.

[0086] ⑦Traditional optomechanical microcavity: Not applicable to crystal structure measurement; in vibration sensing measurement, it can be used for the measurement of molecular vibration frequency and vibration displacement.

[0087] ⑧Mechanical Raman scattering (MRS): Applicable to the global characterization of crystal structures, reflecting both mechanical transmission characteristics and vibration information, with no restrictions on the object.

[0088] In summary, on the one hand, existing spectroscopic methods cannot achieve the measurement of the global structure of layered crystals: For information such as global phonons and sub-picometer atomic layer displacements in crystal materials, ordinary spectroscopic methods are restricted by optical selection rules and electron-phonon coupling strength and are impossible to achieve in principle; moreover, there will be rich interface information in the homojunctions or heterojunctions constructed by layered crystals, and ordinary spectroscopic methods cannot detect hidden interfaces. The present invention completely relies on the mechanical transmission properties in layered crystals and can achieve the detection of crystal global information and hidden interfaces.

[0089] On the other hand, existing interference-based vibration detection methods are not applicable to the vibration measurement of lattice systems (high vibration frequencies, extremely small vibration displacements), and their experimental methods are not feasible in principle for the displacement and frequency detection of layered crystals.

[0090] In summary, the spectral measurement method of the present invention based on the mechanical Raman scattering effect uses a mechanical oscillator to drive the movement of a plasmonic metal to ultimately generate an inelastic scattered light signal. This process is not restricted by the optical selection rules of the sample to be measured (layered crystal). By combining the lattice mechanical properties and optical measurement methods, it is possible to simultaneously detect the global structure, hidden interfaces, and vibration characteristics of the sample to be measured (layered crystal).

[0091] The foregoing description of specific exemplary embodiments of the invention has been presented for purposes of illustration and example. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is apparent that, based on the above examples, many modifications and variations are possible. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the invention and its practical applications, so that those skilled in the art can implement and utilize various different exemplary embodiments of the invention and make various different selections and changes. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A spectral measurement method based on the mechanical Raman scattering effect, characterized in that The method includes: Coupling a plasmonic metal to the surface of a sample to be measured, so that an oscillator to be measured drives the plasmonic metal to generate periodic vibrations; the oscillator to be measured is a mechanical oscillator or a lattice oscillator with mechanical oscillator characteristics; Controlling an excitation light to irradiate the plasmonic metal to generate surface plasmon resonance, collecting and processing the generated inelastic scattered light signal, and obtaining a measurement spectrum of the inelastic scattered light signal; Wherein, the plasmonic optical cavity generated by the surface plasmon resonance vibrates synchronously with the oscillator to be measured, so that photons in the plasmonic optical cavity are mechanically coupled with the oscillator to be measured to generate an inelastic scattered light signal.

2. The spectral measurement method based on the mechanical Raman scattering effect according to claim 1, characterized in that, The incident laser frequency of the excitation light irradiating the surface of the plasmonic metal is adjustable, wherein the incident laser wavelength range for generating plasmon resonance is 250 nm to 300000 nm.

3. The spectral measurement method based on the mechanical Raman scattering effect according to claim 1, characterized in that, There is energy transfer between the oscillator to be measured and the plasmonic metal, and the energy difference between the photon energy of the inelastic scattered light signal and the photon energy of the incident laser is equal to the product of the frequency of the oscillator to be measured and the Planck constant.

4. The spectral measurement method based on the mechanical Raman scattering effect according to claim 1, wherein, In the case of first-order approximation, the intensity of the inelastic scattered light signal is proportional to the square of the amplitude of the oscillator to be measured.

5. The spectral measurement method based on the mechanical Raman scattering effect according to claim 1, characterized in that The plasmonic metal includes one or an alloy of aluminum, gold, silver, copper, sodium, nickel.

6. The spectroscopic measurement method based on the mechanical Raman scattering effect according to claim 2, characterized in that, The plasmonic metal has a nanoscale undulating structure and a resonance excitation wavelength matching the incident laser wavelength.

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