Two-dimensional material MOS2 simulation method based on Raman spectrum and structural defect detection

Abstract

The invention provides a two-dimensional material MOS2 simulation method based on Raman spectrum and structural defect detection. Comprising the following steps: S1, detecting by using a high-resolution Raman spectrum, and placing MoS2 with a complete structure and a defect state on a high-resolution laser Raman spectrometer loading platform to measure a Raman peak of the MoS2; s2, using Gauss View 6.0 to carry out modeling on the MOS2, taking single molecules of the MOS2, and then carrying out superposition and cell expansion to form a two-dimensional plane structure. A density functional (DFT) theory in Gaussian 16 is used, and base groups which have different elements and are suitable for computer configuration are set to carry out structure optimization and frequency calculation. And S3, multiplying the obtained vibration spectrogram data by a correction factor to obtain simulation spectrum parameters of the molybdenum disulfide with the layered structure. And S4, comparing the actually measured Raman spectrum and the simulated Raman spectrum of the molybdenum disulfide MOS2, and analyzing the characteristic peak intensity, the characteristic peak position difference, the broadened Raman and the splitting condition of the molybdenum disulfide MOS2. The invention provides a new method for monitoring and analyzing the structure change process of the two-dimensional material molybdenum disulfide, and has certain reference significance for Raman spectrum research and analysis of other layered materials.

Description

(I) Technical Field

[0001] This invention relates to a simulation method for two-dimensional material MoS2 based on Raman spectroscopy and the detection of structural defects. It utilizes the quantum chemistry software Gaussview 6.0 and Gaussian16W for spectral simulation and combines it with comparative analysis of measured Raman spectra, belonging to the field of computational chemistry technology. (II) Background Technology

[0002] Molybdenum disulfide (MoS2) is a typical semiconductor in the transition metal dihalogen (TMD) family of materials and is also a two-dimensional material. MoS2 is considered a promising optoelectronic two-dimensional material with wide applications in optical sensing, electronics, biosensing, photocatalysis, flexible substrates, and bioimaging. However, under long-term storage or improper handling (exposure to air, light, high temperature, high humidity, and contaminants), it may undergo oxidation, adsorption contamination, structural physical damage, or interlayer re-aggregation. These changes significantly affect its electrical, optical, and catalytic properties. Gaussian, a quantum chemical simulation software, is one of the most widely used quantum chemical simulation tools globally. Its background technology is based on a combination of quantum mechanics theory and high-performance computing methods. Its core algorithm is based on quantum mechanics, especially the Hartree-Fock method, which approximates the Schrödinger equation for multi-electron systems and optimizes molecular orbitals using a self-consistent field method; it also combines exchange-correlation functionals to efficiently handle large molecular systems. It is widely used for molecular structure optimization: Raman, infrared (IR), ultraviolet-visible (UV-Vis), and nuclear magnetic resonance (NMR) spectroscopy prediction and simulation; and reaction mechanisms, which can be used to study chemical reaction pathways through potential energy surface scanning and transition state searching. It is also used in materials and drug design to calculate electronic properties (such as HOMO / LUMO).

[0003] For simulation spectra of two-dimensional materials like MoS2, researchers have rarely conducted experiments simulating MoS2 with lattice defects. There has been almost no work on simulating this structure using Gaussian, and the simulation of its Raman characteristic spectra has always been difficult, and it is impossible to deeply elucidate its structural defects from the attributed vibrational modes. (III) Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a Raman spectroscopy-based simulation method for two-dimensional materials (MOS2) and for detecting structural defects. This invention offers a novel method for monitoring and analyzing the structural changes in the two-dimensional material molybdenum disulfide, thereby achieving non-destructive, rapid, and accurate detection.

[0005] The object of the present invention is achieved like this:

[0006] A two-dimensional material MOS2 simulation method and structural defect detection based on Raman spectroscopy includes the following steps:

[0007] Step S1: Establish the single-molecule MoS2 unit cell structure. Use the quantum chemical calculation software Gauss View 6.0 to model MOS2 and obtain the .cif file, including: establishing its sandwich interlayer structure.

[0008] Step S2: Expand the cell using Cell Replication in PBC in Gauss View 6.0, and in Calculation Setup, select fre for Job Type, check Compute Raman; select DFT-B3LPY for Method, set the basis set to a mixed basis set, select 6-31G* basis set for S, select LANL2DZ pseudopotential basis set for Mo, and save the input file .gjf.

[0009] Further: Submit the computation task to Gaussian 16 for computation.

[0010] Step S3: After optimization and frequency calculation, a stable structure is obtained, and the molecular vibration information in the output file .out can be viewed to obtain the simulated spectrum of monolayer molybdenum disulfide.

[0011] Step S4: Use a LabRAM HR Evolution high-resolution Raman spectrometer manufactured by Horiba for detection. The excitation wavelength of the Raman spectroscopy system is 785 nm, the measurement range of the Raman spectrum is set to 0-1000 cm⁻¹, the laser power is 60 mW, the integration time is 5 s, and the number of times is accumulated is 3.

[0012] Further: Molybdenum disulfide thin film MOS2 and powdered MOS2 were placed on the Raman spectrometer platform to measure their Raman peaks. Monolayer MoS2 was purchased from Shenzhen C6 Co., Ltd. and was prepared by chemical vapor deposition (CVD).

[0013] Step S5: Perform baseline removal and Savitzky-Golay convolution smoothing on the data, compare the simulated and measured Raman spectra of monolayer and powdered molybdenum disulfide MOS2, and analyze the peak spacing to verify the reliability of the simulation.

[0014] In summary, the advantages and positive effects of this invention are as follows:

[0015] This invention is based on quantum chemical calculation software. Before the experiment, a two-dimensional material sample was simulated, which provided a reference and guidance for subsequent analysis.

[0016] The method of simulating the Raman spectrum of two-dimensional layered material MOS2 based on density functional theory (DFT) can provide guidance for the detection of structural defects in MoS2, offer a new method for monitoring and analyzing the structure of two-dimensional molybdenum disulfide, and have certain reference value for the Raman spectral research and analysis of other layered materials.

[0017] It can also provide theoretical guidance for Raman spectroscopy analysis methods of graphene materials. (iv) Description of the attached drawings

[0018] Figure 1 This is a flowchart of a two-dimensional material MOS2 simulation method based on Raman spectroscopy and a structural defect detection method provided in an embodiment of the present invention.

[0019] Figure 2 This is a schematic diagram of the two-dimensional material molybdenum disulfide 2H and 1T phase structure provided in the embodiments of the present invention.

[0020] Figure 3 This is a schematic diagram of the experimental and simulated spectral results provided in the embodiments of the present invention. (V) Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0022] This invention utilizes the chemical calculation software GaussView 6.0 and Gaussian 16 to simulate the Raman spectra of two-dimensional layered structures, which can provide guidance for experiments and has reference value.

[0023] The application principle of the present invention will be described in detail below with reference to the accompanying drawings.

[0024] like Figure 1 As shown, the two-dimensional material MOS2 simulation method and detection based on Raman spectroscopy provided in this embodiment of the invention includes the following steps:

[0025] Step S1: Locate the unit cell structure of the 2H and 1T phases and download the .cif file. Use the quantum chemistry calculation software GaussView 6.0 to modify the monolayer S-Mo-S structure of the MOS2 single molecule; use CellReplication in PBC of GaussView 6.0 to expand the cell, as shown below. Figure 2 The structure shown. Figure 2 (a) and (b) are the same MOS2 structure, but from different perspectives.

[0026] Step S2: This step involves optimizing and calculating the frequency to obtain a stable structure. In Calculation Setup, select Opt+fre for Job Type, check Compute Raman, select DFT-B3LPY for Method, set the basis set to a hybrid basis set, select the 6-31G* basis set for S, and select the LANL2DZ pseudopotential basis set for the transition metal Mo. Save the input file as .gjf.

[0027] Step S3: After submitting the calculation task to Gaussian 16 for calculation, the molecular vibration information in the output file (.out) is obtained after the calculation is completed. The obtained vibrational spectrum data is multiplied by a correction factor to obtain the simulated spectrum of monolayer molybdenum disulfide.

[0028] Step S4: High-resolution Raman spectra were detected using a LabRAM HR Evolution Raman spectrometer manufactured by Horiba. The excitation wavelength of the Raman spectroscopy system was 785 nm. Optical focusing was set, followed by laser focusing. The measurement range of the Raman spectrum was set to 0-1000 cm⁻¹, the laser power was 60 mW, the integration time was 5 s, and the number of iterations was 3.

[0029] Different structures of MOS2 were placed on the Raman spectrometer platform, and their Raman peaks were measured.

[0030] Step S5: Perform baseline removal and Savitzky-Golay convolution smoothing on the data, and compare the simulated and measured Raman spectra of monolayer and powdered molybdenum disulfide MOS2 to obtain the following results. Figure 3 The results are shown. A larger peak position difference in the sample indicates enhanced interlayer coupling, stemming from re-stacking due to long-term storage. Secondly, an increase in the full width at half maximum (FWHM) of the characteristic peaks indicates increased lattice disorder. The broadened Raman peaks in the 150-350 cm⁻¹ range and some stray peaks reflect the presence of sulfur vacancies in MoS₂. Simultaneously, combined with simulations, the splitting of the characteristic peak near 411 cm⁻¹ reflects the interlayer stacking of layered MoS₂; if splitting occurs, it indicates a higher proportion of 1T phase stacking in MoS₂, suggesting structural instability.

[0031] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A simulation method and defect detection method for two-dimensional material MOS2 based on Raman spectroscopy, characterized in that, The system includes the following steps: Step S1: Place a structurally intact, defect-state MOS2 sample on the Raman spectrometer platform and measure its Raman peaks. Step S2: Use the quantum chemical calculation software Gauss View to model MOS2 and obtain the simulated spectrum of the molybdenum disulfide defect state. Step S3: Compare the simulated and measured Raman spectra of monolayer and powdered molybdenum disulfide MOS2, and analyze their characteristic peak intensities, peak position differences, broadened Raman beams, and splitting characteristics. Step S4: Based on the above analysis, determine the defect characteristics of MoS2.

2. The two-dimensional material MOS2 spectral simulation method according to claim 1, characterized in that: Based on the principles of quantum mechanics, the Schrödinger equation is solved, and calculations are performed directly from the electronic structure and nuclear configuration of molecules. This includes constructing different layered molybdenum disulfide structures, providing a fundamental theoretical explanation for the Raman spectral peak positions and intensities. It precisely maps Raman peaks in the two-dimensional material MoS2 to specific molecular vibrational modes, avoiding the need to prepare large quantities of high-quality samples with specific, single defects for systematic Raman testing. Especially when studying a range of defect types, the computational cost is often lower than the experimental cost.

3. The two-dimensional material MOS2 spectral simulation method according to claim 1, characterized in that: The calculations are simplified for heavy atom Mo while maintaining high accuracy for light atoms. This includes: using pseudopotential basis sets such as LANL2DZ for Mo, replacing inner-shell electrons with effective nuclear potentials to improve calculation speed; and using all-electron 6-31G* basis sets for S to simplify calculations and avoid redundancy.

4. The two-dimensional material MOS2 spectral simulation method according to claim 1, characterized in that: Vibrations are identified using the keyword `freq=intmodoes`, providing complete vibrational information for the two-dimensional material MOS2 and visualizing vibrational modes. This includes obtaining the Raman active modes, all frequencies, and atomic displacement vectors. Based on the calculated Raman tensor, the relative intensities of different vibrational modes can be predicted and compared with experimental trends.

5. The structural defect detection method as described in claim 1, characterized in that: By measuring and simulating the Raman spectra of different layers of molybdenum disulfide (MoS2), specifically including analyzing the vibrational modes of the simulated spectra, the intensity of characteristic peaks of the MoS2 defect state, the peak position difference of characteristic peaks, the broadened Raman spectrum, and the splitting condition, a non-destructive, rapid, and accurate detection of the existence and degree of structural damage can be achieved.

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