Method for determining the number of layers in transition metal chalcogenides

Abstract

The present invention is applicable to the field of transition metal chalcogenide layer number measurement technology and provides a method for determining the layer number of transition metal chalcogenides, comprising the following steps: selecting 15 detection areas with different layer numbers; obtaining white light reflectance spectra of each detection area under the same light intensity; determining the first reflection peak intensity and / or second reflection peak intensity of each detection area based on each white light reflectance spectrum; obtaining the layer number of each detection area; determining the correspondence between the layer number and the first reflection peak intensity and / or second reflection peak intensity of all detection areas; and determining the layer number of the sample to be detected based on the correspondence and the white light reflectance spectrum of the sample to be detected. The method for determining the layer number of transition metal chalcogenides provided by the present invention can simply, quickly, reliably, and non-destructively determine the layer number of the detection area in a high-throughput manner.

Description

Technical Field

[0001] The present invention belongs to the technical field of layer number measurement of transition metal chalcogenides, and in particular relates to a method for determining the layer number of transition metal chalcogenides. Background Art

[0002] Transition metal chalcogenides, such as MoS2 thin films and WS2 thin films, are expected to become next-generation optoelectronic devices, photocatalysts, electrocatalysts, and energy storage materials due to their excellent optical, catalytic, and lithium storage properties. As the number of layers increases, multilayer transition metal chalcogenides exhibit electronic band structures and physical properties that differ from those of single-layer transition metal chalcogenides. Therefore, determining the number of layers in transition metal chalcogenides is crucial for studying the physical properties of these materials and promoting their application in semiconductor devices.

[0003] Currently, there are several main methods for determining the number of layers of transition metal chalcogenides: the first is to measure the thickness of the film using an atomic force microscope, and then estimate the specific number of layers of the film prepared by peeling based on the theoretical thickness of a layer of film; the second is to detect the number of layers of the film using an electron microscope (such as a scanning electron microscope (SEM), a transmission electron microscope (TEM), and a scanning tunneling microscope (STM)); the third is to detect the number of layers of the film based on Raman spectroscopy and photoluminescence spectroscopy; and the fourth is to detect the number of layers of the film based on optical microscopy technology, such as technology based on optical contrast and sample color.

[0004] However, when using the first method, atomic force microscopy may cause structural defects in the film, and the measurement results may be affected by the absorption of the water layer. At the same time, this method is only suitable for the thickness measurement of small-sized two-dimensional nanofilms. When measuring large-area films, it also has the disadvantages of being time-consuming and having low throughput. When using the second method, it is not only time-consuming and costly, but may also introduce contamination or damage due to electron beam-induced deposition or atomic displacement. When using the third method, the number of layers that can be judged is extremely limited (generally only valid for 1-6 layers). When using the fourth method, data processing is cumbersome or the effective range of layer judgment is small.

[0005] Therefore, it is very necessary to develop a method that can simply, quickly, reliably and non-destructively determine the number of layers in the detection area with high throughput. Summary of the Invention

[0006] The present invention aims to provide a method for determining the number of layers in transition metal chalcogenides. This method, based solely on white light reflectance spectra, analyzes the intensity of the reflection peaks to provide a simple, rapid, reliable, and non-destructive high-throughput determination of the number of layers in the detection area, without requiring complex data processing or analysis.

[0007] The present invention is achieved by a method for determining the number of layers of a transition metal chalcogenide, comprising the following steps:

[0008] Select 15 detection areas with different numbers of layers, where the number of layers in each detection area is between 1 and 15;

[0009] Obtaining white light reflectance spectra of each detection area under the same light intensity;

[0010] Determining a first reflection peak intensity and / or a second reflection peak intensity of each detection area according to each white light reflectance spectrum; the first reflection peak intensity is the intensity of the reflection peak corresponding to the C exciton, and the second reflection peak intensity is the intensity of the reflection peak corresponding to the LED white light source with a wavelength between 570nm and 620nm;

[0011] Obtaining the number of layers in each of the detection areas;

[0012] determining a corresponding relationship between the number of layers of all the detection areas and the first reflection peak intensity and / or the second reflection peak intensity;

[0013] The number of layers of the sample to be detected is determined according to the corresponding relationship and the white light reflectance spectrum of the sample to be detected.

[0014] In an optional embodiment, determining the correspondence between the number of layers of all the detection areas and the first reflection peak intensity and / or the second reflection peak intensity comprises the following steps:

[0015] Obtaining a change relationship between the first reflection peak intensity and the second reflection peak intensity as the number of layers in the detection area changes;

[0016] Determine, based on the change relationship, a critical layer value n at which the first reflection peak intensity changes linearly with the number of layers in the detection area;

[0017] Establishing a corresponding relationship between the number of layers of the detection area with a number of layers less than or equal to n and the intensity of the second reflection peak;

[0018] A corresponding relationship between the number of layers of the detection area with a number of layers greater than or equal to n and the first reflection peak intensity is established.

[0019] In an optional embodiment, the method for determining the number of layers of the transition metal chalcogenide compound further includes the following steps:

[0020] According to the linear relationship between the first reflection peak intensity and the number of layers in the detection area, the corresponding relationship between the number of layers between 15 and 30 and the first reflection peak intensity is derived.

[0021] In an optional embodiment, the derivation of the corresponding relationship between the number of layers between 15 and 30 and the first reflection peak intensity based on the linear relationship between the first reflection peak intensity and the number of layers in the detection area comprises the following steps:

[0022] Determining a linear relationship between the number of layers and the first reflection peak intensity based on data analysis of the number of layers and the first reflection peak intensity in all the detection areas;

[0023] The corresponding relationship between the number of layers between 15 and 30 and the first reflection peak intensity is derived based on the linear relationship.

[0024] In an optional embodiment, determining the number of layers of the sample to be detected based on the corresponding relationship and the white light reflectance spectrum of the sample to be detected includes the following steps:

[0025] Establishing a database of layer numbers and corresponding reflection peak intensities according to the corresponding relationship;

[0026] The number of layers of the sample to be detected is obtained by searching based on the corresponding reflection peak intensity in the white light reflection spectrum of the sample to be detected and the database.

[0027] In an optional embodiment, the method for determining the number of layers of a transition metal chalcogenide compound further includes the following steps before selecting the plurality of detection areas:

[0028] Preparation of transition metal chalcogenide films by gold film-assisted stripping technology;

[0029] A plurality of detection areas are selected from the transition metal chalcogenide film.

[0030] In an optional embodiment, the preparation of the transition metal chalcogenide film by the gold film assisted stripping technique comprises the following steps:

[0031] providing a silicon substrate;

[0032] preparing a titanium bonding layer on the silicon substrate;

[0033] preparing a gold film on the titanium bonding layer;

[0034] A transition metal chalcogenide film is prepared on the gold film.

[0035] In an optional embodiment, the step of preparing the detection area on the gold film comprises the following steps:

[0036] Providing transition metal chalcogenide crystals;

[0037] pressing the transition metal chalcogenide crystals onto the surface of the gold film to form a composite;

[0038] The above composition was annealed at 180° C. for 60 seconds and then cooled for 10-20 seconds.

[0039] In an optional embodiment, the following steps are further included between the step of providing a silicon substrate and the step of forming a gold film on the silicon substrate:

[0040] The surface of the silicon substrate is cleaned and dried.

[0041] In an optional embodiment, a Raman spectrometer equipped with an LED white light source is used to obtain multiple white light reflectance spectra corresponding to the multiple detection areas under the same light intensity;

[0042] The detection area is a MoS2 thin film.

[0043] The technical effect of the present invention compared to the prior art is as follows: the method for determining the number of layers of transition metal chalcogenides provided in the embodiment of the present invention is based on the white light reflectance spectrum corresponding to the detection area. By fully utilizing the reflection peak induced by the rich exciton properties of transition metal chalcogenides in the reflectance spectrum and the emission peak of the light source, and combining it with existing methods for detecting the number of layers, the number of layers of detection areas of different sizes can be accurately and quickly determined in a non-contact, non-destructive, and high-throughput manner. In addition, the method for determining the number of layers of transition metal chalcogenides provided in the embodiment of the present invention has simple data processing and a wide effective judgment range. According to tests, the method for determining the number of layers of transition metal chalcogenides provided in the embodiment of the present invention can determine the number of layers in detection areas of 1-30 layers, and the entire operation can achieve non-destructive testing. Such a large application range is currently difficult to achieve based on optical contrast methods.

[0044] Thus, the method for determining the number of layers of transition metal chalcogenides provided in the embodiments of the present invention can accurately and nondestructively determine the number of layers in detection areas ranging from 1 to 30 layers, or even thicker. This wide range of layer determination is difficult to achieve with previous thickness characterization techniques. The timely emergence of the method for determining the number of layers of transition metal chalcogenides provided in the embodiments of the present invention will greatly promote basic research on layer-number-related physics (e.g., optics, thermal, and electrical) and the demonstration of proof-of-concept devices based on transition metal chalcogenides. Furthermore, this technology can be easily combined with fluorescence and Raman spectroscopy to simultaneously study other layer-number-related physical properties of transition metal chalcogenides. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0046] Figure 1 1 is a flow chart of a method for determining the number of layers of a transition metal chalcogenide compound provided in an embodiment of the present invention;

[0047] Figure 2 Schematic diagram of a curve showing the wavelength and reflection intensity of a MoS2 film having 1 to 10 layers measured using the method for determining the number of layers of a transition metal chalcogenide compound provided in an embodiment of the present invention;

[0048] Figure 3 yes Figure 2 Schematic diagram of the curves of different reflection peak intensities and layer numbers as the number of MoS2 films changes, and the fitting curve corresponding to the C peak intensity;

[0049] Figure 4 It is a structural diagram of using a Raman spectrometer to detect the sample to be detected.

[0050] Description of reference numerals:

[0051] 100. Raman spectrometer; 110. Spectrometer body; 120. LED white light source; 130. Objective lens; 200. Detection platform; 300. Sample to be detected. DETAILED DESCRIPTION

[0052] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0053] In the description of the present invention, it should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0054] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature identified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0055] In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0056] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0057] Please refer to Figure 1 As shown, in an embodiment of the present invention, a method for determining the number of layers of a transition metal chalcogenide is provided. The transition metal chalcogenide in this embodiment can be any one of a MoS2 thin film, a WS2 thin film, a NbS2 thin film, and the like.

[0058] The method for determining the number of layers of a transition metal chalcogenide comprises the following steps:

[0059] S1. Select 15 detection areas with different numbers of layers, where the number of layers in each detection area is between 1 and 15.

[0060] Specifically, the 15 detection areas can be prepared separately or prepared at one time using gold film-assisted stripping technology. The specific selection can be flexibly made according to experimental conditions and R&D needs.

[0061] S2. Obtain the white light reflectance spectrum of each detection area under the same light intensity.

[0062] Specifically, a Raman spectrometer equipped with an LED white light source can be used to illuminate the detection areas of different layers, and obtain the white light reflectance spectra corresponding to the detection areas of different layers under the same light intensity. Other spectrometers that can obtain the above-mentioned white light reflectance spectra can also be used for operation, and this is not limited here.

[0063] S3. Determine the first reflection peak intensity and / or second reflection peak intensity of each detection area according to each white light reflection spectrum; the first reflection peak intensity is the intensity of the reflection peak corresponding to the C exciton, and the second reflection peak intensity is the intensity of the reflection peak corresponding to the LED white light source with a wavelength between 570nm-620nm.

[0064] The above white light reflectance spectrum is as follows Figure 2 As shown, there are generally exciton reflection peaks corresponding to A excitons, B excitons, and C excitons, as well as multiple light source reflection peaks corresponding to light sources of different wavelengths. During use, the first reflection peak intensity and / or second reflection peak intensity corresponding to each detection area can be obtained by analyzing the white light reflection spectrum corresponding to each detection area.

[0065] S4. Obtain the number of layers of multiple detection areas.

[0066] Specifically, this step can be measured by any one or more of existing technologies, such as atomic force microscopy, scanning electron microscopy, transmission electron microscopy, scanning tunneling microscopy, Raman spectroscopy, and photoluminescence spectroscopy.

[0067] S5. Determine the corresponding relationship between the number of layers of all detection areas and the first reflection peak intensity and / or the second reflection peak intensity.

[0068] Specifically, this step can be performed by manually recording the number of layers, the first reflection peak intensity and / or the second reflection peak intensity measured in the same detection area one by one to form a corresponding relationship between the number of layers and the first reflection peak intensity and / or the second reflection peak intensity of each detection area; or a curve graph of the number of layers, the first reflection peak intensity and / or the second reflection peak intensity measured in the same detection area can be obtained based on the above data fitting, and the corresponding relationship between the number of layers, the first reflection peak intensity and / or the second reflection peak intensity measured in the same detection area can be obtained based on the corresponding curve.

[0069] S6. Determine the number of layers of the sample to be tested according to the corresponding relationship and the white light reflectance spectrum of the sample to be tested.

[0070] The principle underlying the method for determining the number of layers of a transition metal chalcogenide provided in an embodiment of the present invention is:

[0071] After measuring the white light reflectance spectrum of the detection area with different number of layers (in this application, molybdenum disulfide MoS2 is used as an example), we found that a series of reflection peaks appeared in the reflection spectrum, such as Figure 2 shown. Figure 2 This is a comparison chart of the white light reflectance spectra corresponding to 1-10 layers of molybdenum disulfide MoS2 films.

[0072] Through analysis Figure 2As shown in the comparison diagram, it is found that the three reflection peaks located at around 450nm, 605nm and 900nm correspond to the three emission peaks of the LED light source. For the convenience of description, the reflection peak near 605nm is marked as the O peak. In addition, three additional reflection peaks appear in the white light reflectance spectrum corresponding to the molybdenum disulfide MoS2 film. Among them, the two lowest energy peaks (1.79eV and 1.92eV) correspond to A excitons and B excitons, and the response at higher photon energy (2.36eV) corresponds to C excitons. For the convenience of description, the reflection peak corresponding to A excitons will be referred to as A peak, the reflection peak corresponding to B excitons will be referred to as B peak, and the reflection peak corresponding to C excitons will be referred to as C peak.

[0073] from Figure 2 It can be seen that the positions and intensities of peaks A, B, and C have obvious layer number dependence. Specifically, due to the quantum confinement effect and optical interference effect, as the number of MoS2 layers increases, the positions of the three reflection peaks are red-shifted. However, the intensities of the three reflection peaks have different evolution trends. For 1-3 layer (layer, L) MoS2 films, peaks A and B are almost invisible due to the interlayer charge transfer in the ultra-thin MoS2-Au mixed system. When the number of layers of the MoS2 film exceeds 3, the intensities of peaks A and B decrease monotonically with the increase of the sample thickness. Please refer to Figure 2 and Figure 3 In contrast, the intensity of the C peak increases monotonically with increasing sample thickness.

[0074] More importantly, when the number of MoS2 film layers is greater than 5, the intensity of the C peak shows a perfect linear relationship with the number of MoS2 film layers (linear fitting parameter R 2 =0.9995), indicating that the reflection peak intensity corresponding to C excitons can be used to easily and accurately determine the number of layers in thicker MoS2 films.

[0075] For 1-5 layers of MoS2 film, although the intensity of the C peak increases monotonically, the increase is very small, which is not convenient for accurately determining the number of layers. However, we note that when the number of layers of the MoS2 film increases, the position of the O peak in the white light reflectance spectrum does not change, but the O peak intensity shows a significant decrease between the number of layers of the MoS2 film from 1 to 9 layers, and increases again when the number of layers of the MoS2 film is greater than 9. Therefore, the O peak can be used to accurately determine the number of layers of the MoS2 film of 1-7 layers where the C peak is not easy to distinguish. Once the number of layers of the MoS2 film of 1-7 layers is determined by the O peak, the slope of the linear increase region in the C peak intensity can be determined and used to accurately identify the number of layers of thicker MoS2 films. The above is the basic principle of accurately determining the number of layers of transition metal chalcogenides by white light reflectance spectroscopy in this application.

[0076] The method for determining the number of layers of transition metal chalcogenides provided in an embodiment of the present invention is based on the white light reflectance spectrum corresponding to the detection area. By fully utilizing the reflection peaks induced by the rich exciton properties of transition metal chalcogenides in the reflectance spectrum and the emission peaks of the light source, and combining it with existing methods for detecting the number of layers, it can accurately and rapidly determine the number of layers in detection areas of varying sizes in a non-contact, non-destructive, and high-throughput manner. Furthermore, the method for determining the number of layers of transition metal chalcogenides provided in an embodiment of the present invention simplifies data processing and has a wide effective judgment range. Testing has shown that the method for determining the number of layers of transition metal chalcogenides provided in an embodiment of the present invention can determine the number of layers in detection areas of 1-30 layers, and the entire operation can achieve non-destructive testing. This wide range of applications is currently difficult to achieve using optical contrast methods.

[0077] Thus, the method for determining the number of layers of transition metal chalcogenides provided in the embodiments of the present invention can accurately and nondestructively determine the number of layers in detection areas ranging from 1 to 30 layers, or even thicker. This wide range of layer determination is difficult to achieve with previous thickness characterization techniques. The timely emergence of the method for determining the number of layers of transition metal chalcogenides provided in the embodiments of the present invention will greatly promote basic research on layer-number-related physics (e.g., optics, thermal, and electrical) and the demonstration of proof-of-concept devices based on transition metal chalcogenides. Furthermore, this technology can be easily combined with fluorescence and Raman spectroscopy to simultaneously study other layer-number-related physical properties of transition metal chalcogenides.

[0078] In an optional embodiment, determining the correspondence between the number of layers of all detection areas and the first reflection peak intensity and / or the second reflection peak intensity, that is, the above-mentioned step S5, includes the following steps:

[0079] S51, obtaining the relationship between the first reflection peak intensity and the second reflection peak intensity as the number of layers in the detection area changes;

[0080] S52, determining a critical layer value n at which the first reflection peak intensity changes linearly with the number of layers in the detection area according to the change relationship;

[0081] S53, establishing a corresponding relationship between the number of layers in the detection area with a number of layers less than or equal to n and the second reflection peak intensity;

[0082] S54 , establishing a corresponding relationship between the number of layers in the detection area with a number of layers greater than or equal to n and the first reflection peak intensity.

[0083] For ease of understanding, Figure 2 and Figure 3The analysis of the case shown in the figure shows that when the number of layers in the detection area is less than or equal to 7, the intensity of the second reflection peak (i.e., the O peak) changes significantly, and when the number of layers of the MoS2 film is greater than 5, the intensity of the C peak shows a perfect linear relationship with the number of layers of the MoS2 film (linear fitting parameter R 2 =0.9995), that is, in this scheme, n is 5. Since the second reflection peak intensity of films with fewer than 5 layers varies significantly with the number of layers, and the first reflection peak intensity of films with more than 5 layers varies significantly with the number of layers, a corresponding relationship between the number of layers and the second reflection peak intensity can be established for detection areas with fewer than 5 layers, and a corresponding relationship between the number of layers and the first reflection peak intensity can be established for detection areas with more than 5 layers. Using this method, the number of layers in MoS2 films of different thicknesses can be accurately and quickly determined.

[0084] because Figure 2 and Figure 3 For a specific example, when the detection environment such as the substrate and LED light source in the detection area changes, the above n value will also change. Therefore, the n value can be derived from the specific data and is not limited here.

[0085] In summary, the method for determining the number of layers of transition metal chalcogenides provided in this embodiment can accurately and quickly determine the number of layers of transition metal chalcogenides of different thicknesses.

[0086] The above analysis shows that when the number of layers of a transition metal chalcogenide compound is greater than n, a linear relationship exists between the first reflection peak intensity and the number of layers. Thus, the number of layers of a transition metal chalcogenide compound exceeding 15 layers can be deduced based on this linear relationship. In an optional embodiment, the method for determining the number of layers of a transition metal chalcogenide compound further includes the following steps between determining the correspondence between the number of layers and the first reflection peak intensity and / or the second reflection peak intensity in all detection areas, and determining the number of layers of the sample to be detected based on the correspondence and the white light reflectance spectrum of the sample to be detected:

[0087] According to the linear relationship between the first reflection peak intensity and the number of layers in the detection area, the corresponding relationship between the number of layers between 15 and 30 and the first reflection peak intensity is derived.

[0088] For ease of understanding, Figure 2 and Figure 3 The specific operation of the solution provided in this embodiment can refer to the following steps:

[0089] First, select the layer number and first reflection peak intensity data for at least two test areas with 5 or more layers. Let the layer number be x and the first reflection peak intensity be y. Substitute the two sets of data into the formula y = ax + b to obtain a and b, and then obtain a linear relationship. For example, the first set of data has 6 layers and a first reflection peak intensity of 0.31; the second set of data has 14 layers and a first reflection peak intensity of 0.71. Substituting a into the above formula to calculate a and b is 0.05 and 0.01, the resulting linear relationship is y = 0.05x + 0.01.

[0090] Then, based on the above linear relationship, the corresponding relationship between the number of layers and the first reflection peak intensity of the detection area with different numbers of layers is obtained. Specifically, when x = 5, 6, 7, etc., the corresponding y is calculated using the relationship y = ax + b, forming the corresponding data of the number of layers in the detection area and the first reflection peak intensity.

[0091] In addition, a curve graph can be first fitted between the data of the number of layers and the first reflection peak intensity in each detection area, and then the slope and intercept of the curve for the part of the curve with more than 5 layers can be obtained based on the curve graph. Finally, a linear relationship between the number of layers and the first reflection peak intensity can be obtained based on the above curve slope and intercept.

[0092] Of course, in other embodiments, other methods may be used to derive the linear relationship between the number of layers and the first reflection peak intensity, which is not the only limitation here.

[0093] Then, based on the linear relationship, mathematical calculations can be used to obtain the corresponding relationship between the number of layers between 15 and 30 and the intensity of the first reflection peak.

[0094] By adopting the method provided in this embodiment, more data can be obtained with fewer measurements and simple calculations, and the operation is simple and the numerical values ​​are accurate.

[0095] To ensure data accuracy, in an optional embodiment, the corresponding relationship between the number of layers between 15 and 30 and the first reflection peak intensity is derived based on the linear relationship between the first reflection peak intensity and the number of layers in the detection area, including the following steps:

[0096] Fitting a curve graph between the number of layers and the first reflection peak intensity in all detection areas;

[0097] Obtain curve parameters of the straight line portion of the curve graph, the curve parameters including the curve slope;

[0098] According to the curve parameters, a linear relationship between the number of layers and the intensity of the first reflection peak is obtained;

[0099] The corresponding relationship between the number of layers between 15 and 30 and the intensity of the first reflection peak was derived based on the linear relationship.

[0100] Specifically, the curve parameters include the curve slope, and may also include the curve intercept, linear correlation, etc., which can be flexibly selected according to the needs of use. Figure 3 As shown in the figure, the slope of the curve for the portion with more than 5 layers is 0.0522, and the square of the linear correlation is 0.9995. In this case, y ≈ 0.0522x.

[0101] This method can avoid the adverse effects of large deviations in the selected data on the linear relationship, effectively improve the accuracy of the linear relationship, and thus improve the accuracy of the final result.

[0102] In an optional embodiment, determining the number of layers of the sample to be detected according to the corresponding relationship and the white light reflectance spectrum of the sample to be detected, that is, the above-mentioned step S6, includes the following steps:

[0103] S61, establishing a database of layer numbers and corresponding reflection peak intensities according to the corresponding relationship;

[0104] S62. Find the number of layers of the sample to be detected based on the corresponding reflection peak intensity in the white light reflection spectrum of the sample to be detected and the database.

[0105] In this way, by establishing a database once, it can provide support for multiple subsequent tests to improve the detection speed.

[0106] Since the successful preparation of graphene in 2004, tape-based mechanical exfoliation has been the most commonly used method to obtain high-quality single-crystalline monolayers and few-layer two-dimensional materials, but the size of the exfoliated samples is very limited. Recently, a gold film-assisted exfoliation technique has emerged that is effective for dozens of two-dimensional crystals. Using this technique, not only can high-quality millimeter-scale or even centimeter-scale transition metal dichalcogenides (TMDs) monolayers be obtained, but also large-area multi-layer films can be exfoliated. In these large-area films, there are usually a large number of regions with different thicknesses separated by a layer, and such samples are difficult to achieve with traditional tape-exfoliated samples. Such films provide an excellent platform for the study of layer-related physics and the demonstration of proof-of-concept devices, and therefore gold film-assisted exfoliation technology is stimulating growing interest in two-dimensional materials.

[0107] In an optional embodiment, the method for determining the number of layers of a transition metal chalcogenide compound further includes the following steps before selecting 15 detection areas (ie, step S1):

[0108] Preparation of transition metal chalcogenide films by gold film-assisted stripping technology;

[0109] A plurality of detection areas are selected from the transition metal chalcogenide film.

[0110] Specifically, the gold film-assisted stripping technology has revolutionized the preparation of multi-layer transition metal chalcogenide single crystal thin films. This technology can prepare a wide range of samples with different numbers of layers. This is something that traditional tape stripping technology can easily achieve. Accordingly, the layer number characterization technology of these thin films also needs to be innovated. The previous layer number characterization technology based on the optical contrast method involves a complex data processing process and has a small scope of application. It is obvious that it can no longer meet the requirements for layer number characterization of samples with richer layers. A new optical method with a wider range of applications is urgently needed. The solution provided in this embodiment can achieve the preparation of large-area thin films with a wider range of applications and the determination of the number of layers.

[0111] It should be noted that the transition metal chalcogenide film prepared in this embodiment has multiple regions with different thicknesses (ie, different numbers of layers), from which generally 15 detection regions can be directly selected.

[0112] In addition, the rise of gold film-assisted exfoliation technology has made it possible to mass-produce large-scale, high-quality, ultrathin two-dimensional materials. The solution provided in this embodiment not only allows the preparation of millimeter-scale or even centimeter-scale monolayers, but also thin films with a wide range of different thickness regions. These diverse sample formats provide an excellent platform for the study of layer-dependent physics and also bring opportunities for the practical application and commercialization of two-dimensional material-based devices. The method for determining the number of layers of transition metal chalcogenides proposed in this application not only takes into account the advantages of non-destructiveness, high throughput, and precision, but also fully utilizes the rich exciton properties of transition metal chalcogenides, thereby enabling the determination of the number of layers in detection areas of 1-30 layers or even thicker. This will further advance the study of layer-dependent physics and open up the possibility for researchers to explore the novel physics that may exist in thicker films. In addition, this will also promote the research of thickness-dependent two-dimensional material-based devices. It should be noted that thicker films have greater advantages in hybrid functional devices such as photodetection and photocatalysis. In summary, the combination of the layer-number determination technology in this application with the emerging large-area, ultrathin two-dimensional material preparation technology will greatly promote the study of layer-dependent physics and devices of two-dimensional materials.

[0113] To prevent the gold film from falling off in the above embodiment, in an optional embodiment, preparing the transition metal chalcogenide film by gold film assisted stripping technology includes the following steps:

[0114] providing a silicon substrate;

[0115] preparing a titanium bonding layer on a silicon substrate;

[0116] A gold film is prepared on the titanium bonding layer;

[0117] Transition metal chalcogenide films were prepared on gold films.

[0118] In this embodiment, the titanium bonding layer and the gold film can be respectively produced by a DC magnetron sputtering system. The thickness of the titanium bonding layer is 6.5 nm, and the thickness of the gold film is 9.7 nm. Other methods can also be used for production, which is not limited here.

[0119] In an optional embodiment, preparing a transition metal chalcogenide film on a gold film (i.e., the above-mentioned step S03) includes the following steps:

[0120] S031. Providing a transition metal chalcogenide crystal;

[0121] S032, pressing a transition metal chalcogenide crystal onto the surface of the gold film to form a composite;

[0122] S033. Anneal the above composition at 180° C. for 60 seconds, then take it out and cool it for 10-20 seconds.

[0123] To do this, they first use tape to tear off a section of MoS2 bulk crystal and press it onto a freshly prepared Au / Ti / SiO2 / Si substrate. They are then annealed at 180°C for 60 seconds and then removed and allowed to cool for 10-20 seconds. After removing the tape, large-area single-layer and few-layer MoS2 films are obtained.

[0124] The method provided in this embodiment is used to prepare the detection area, which is simple to operate and has a good preparation effect.

[0125] To ensure the preparation effect of the gold film, in an optional embodiment, between providing the silicon substrate and preparing the gold film on the silicon substrate, that is, between the above steps S01 and S02, the following steps are further included:

[0126] The silicon substrate is surface cleaned and dried.

[0127] The specific operations can be done in the following ways:

[0128] The silicon substrate was ultrasonically treated in acetone, isopropanol, and ethanol for 20-30 minutes respectively;

[0129] Dry it with a nitrogen gun.

[0130] Of course, in other embodiments, other methods may be used to clean and dry the surface, which can be flexibly selected according to usage needs and are not limited here.

[0131] By adopting the solution provided in this embodiment, the surface of the silicon substrate can be cleaned before preparing the gold film to avoid the adverse effects of impurities on the surface of the silicon substrate on the preparation of the gold film, thereby ensuring the stable connection between the gold film and the silicon substrate, and the stability of the final detection area structure.

[0132] In a specific embodiment, a Raman spectrometer 100 equipped with an LED white light source is used to measure the white light reflectance spectra corresponding to detection areas with different numbers of layers under the same light intensity;

[0133] The detection area is the MoS2 thin film.

[0134] Specifically, the structure of the Raman spectrometer 100 equipped with an LED white light source can be referred to Figure 4 As shown, the spectrometer includes a main body 110, an LED white light source 120, and an objective lens 130. During use, a sample 300 to be tested is placed on the testing platform 200. The LED white light source 120 then emits light toward the sample 300 to be tested. This light then passes through the objective lens 130 and irradiates the sample 300 to be tested. The light then passes through the objective lens 130 and enters the main body 110 of the spectrometer. The spectrometer main body 110 then forms a white light reflectance spectrum of the sample to be tested based on the light received.

[0135] The specific operations are as follows:

[0136] The SiO2 / Si wafer was ultrasonically treated in acetone, isopropanol, and ethanol for 25 minutes respectively, and then dried with a nitrogen gun. First, a titanium (Ti) adhesion layer was evaporated on the pre-cleaned SiO2 / Si substrate, and then a thin gold (Au) film was deposited on the Ti / SiO2 / Si structure. The two metal layers were prepared using a DC magnetron sputtering system. A part was torn off from the MoS2 bulk crystal with tape and then pressed onto the newly prepared Au / Ti / SiO2 / Si substrate. They were annealed at 180°C for 60 seconds, then taken out and cooled for 10-20 seconds. After removing the tape, large-area single-layer and few-layer MoS2 films can be obtained.

[0137] Measure the reflectance spectra of Au / Ti / SiO2 / Si substrates and samples with different number of layers on them under the same light intensity;

[0138] The layer-number-dependent peak intensities of the C and O peaks were extracted from these reflection spectra;

[0139] Use atomic force microscopy to confirm the number of sample layers and establish a database of reflection peak intensity and layer number;

[0140] Determine the thickness of other thin layers using a standard database.

[0141] The entire operation is simple, reliable, fast, non-destructive, high-throughput, and easy to promote.

[0142] The foregoing description is merely a preferred embodiment of the present invention and specifically describes the technical principles of the present invention. These descriptions are intended solely to explain the principles of the present invention and should not be construed in any way as limiting the scope of protection of the present invention. Based on the explanations herein, any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention, as well as other specific embodiments of the present invention that can be devised by those skilled in the art without inventive effort, shall be included within the scope of protection of the present invention.

Claims

1. A method for determining the number of layers in a detection region of 1 to 30 layers of a transition metal chalcogenide compound, characterized in that: The following steps are involved: Select 15 detection areas with different numbers of layers, where the number of layers in each detection area is between 1 and 15; Obtaining white light reflectance spectra of each detection area under the same light intensity; Determining a first reflection peak intensity and a second reflection peak intensity of each detection area according to each white light reflectance spectrum; the first reflection peak intensity is the intensity of the reflection peak corresponding to the C exciton, and the second reflection peak intensity is the intensity of the reflection peak corresponding to the LED white light source with a wavelength between 570nm and 620nm; Obtaining the number of layers in each of the detection areas; determining a corresponding relationship between the number of layers of all the detection areas and the first reflection peak intensity and the second reflection peak intensity; Determining the number of layers of the sample to be tested according to the corresponding relationship and the white light reflectance spectrum of the sample to be tested; Determining the correspondence between the number of layers of all the detection areas and the first reflection peak intensity and the second reflection peak intensity comprises the following steps: Obtaining a change relationship between the first reflection peak intensity and the second reflection peak intensity as the number of layers in the detection area changes; Determine, based on the change relationship, a critical layer value n at which the first reflection peak intensity changes linearly with the number of layers in the detection area; Establishing a corresponding relationship between the number of layers of the detection area with a number of layers less than or equal to n and the intensity of the second reflection peak; A corresponding relationship between the number of layers of the detection area with a number of layers greater than or equal to n and the first reflection peak intensity is established.

2. The method for determining the number of layers in the detection region of 1 to 30 layers of transition metal chalcogenide compounds according to claim 1, wherein: The method for determining the number of layers of a transition metal chalcogenide compound further includes the following steps between determining the correspondence between the number of layers of all the detection areas and the first reflection peak intensity and the second reflection peak intensity, and determining the number of layers of the sample to be detected based on the correspondence and the white light reflectance spectrum of the sample to be detected: According to the linear relationship between the first reflection peak intensity and the number of layers in the detection area, the corresponding relationship between the number of layers between 15 and 30 and the first reflection peak intensity is derived.

3. The method for determining the number of layers in the detection region of 1 to 30 layers of transition metal chalcogenide compounds according to claim 2, wherein: The step of deducing the corresponding relationship between the number of layers between 15 and 30 and the first reflection peak intensity based on the linear relationship between the first reflection peak intensity and the number of layers in the detection area comprises the following steps: Fitting a curve graph between the number of layers in all the detection areas and the first reflection peak intensity data; Obtaining curve parameters of the straight line portion of the curve graph, wherein the curve parameters include a curve slope; According to the curve parameters, a linear relationship between the number of layers and the first reflection peak intensity is obtained; The corresponding relationship between the number of layers between 15 and 30 and the first reflection peak intensity is derived based on the linear relationship.

4. The method for determining the number of layers of a detection region of 1 to 30 layers of a transition metal chalcogenide compound according to any one of claims 1 to 3, characterized in that: Determining the number of layers of the sample to be detected based on the corresponding relationship and the white light reflectance spectrum of the sample to be detected includes the following steps: Establishing a database of layer numbers and corresponding reflection peak intensities according to the corresponding relationship; The number of layers of the sample to be detected is obtained by searching based on the corresponding reflection peak intensity in the white light reflection spectrum of the sample to be detected and the database.

5. The method for determining the number of layers of a detection region of 1 to 30 layers of a transition metal chalcogenide compound according to any one of claims 1 to 3, characterized in that: The method for determining the number of layers further includes the following steps before selecting 15 detection areas: Preparation of transition metal chalcogenide films by gold film-assisted stripping technology; A plurality of detection areas are selected from the transition metal chalcogenide film.

6. The method for determining the number of layers in the detection region of 1 to 30 layers of transition metal chalcogenide compounds according to claim 5, characterized in that: The method of preparing a transition metal chalcogenide film by gold film assisted stripping technology comprises the following steps: providing a silicon substrate; preparing a titanium bonding layer on the silicon substrate; preparing a gold film on the titanium bonding layer; A transition metal chalcogenide film is prepared on the gold film.

7. The method for determining the number of layers in the detection region of 1 to 30 layers of transition metal chalcogenide compounds according to claim 6, characterized in that: The preparation of the transition metal chalcogenide film on the gold film comprises the following steps: Providing transition metal chalcogenide crystals; pressing the transition metal chalcogenide crystals onto the surface of the gold film to form a composite; The above composition was annealed at 180° C. for 60 seconds and then cooled for 10-20 seconds.

8. The method for determining the number of layers in the detection region of 1 to 30 layers of transition metal chalcogenide compounds according to claim 6, wherein: The method further includes the following steps between providing a silicon substrate and preparing a gold film on the silicon substrate: The surface of the silicon substrate is cleaned and dried.

9. The method for determining the number of layers of a detection region of 1 to 30 layers of a transition metal chalcogenide compound according to any one of claims 1 to 3, characterized in that: A Raman spectrometer equipped with an LED white light source is used to obtain a plurality of white light reflectance spectra corresponding to the plurality of detection areas under the same light intensity; The detection area is a MoS2 thin film.

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