Transition metal chalcogenide single crystal film and preparation method thereof
By using a sapphire substrate with intrinsic symmetry C1v and annealing treatment, the problem of twin formation on the sapphire C-plane substrate was solved, and high-quality wafer-level transition metal chalcogenide single-crystal thin films were prepared, improving the uniformity and robustness of the preparation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NANJING UNIV
- Filing Date
- 2026-02-13
- Publication Date
- 2026-05-12
AI Technical Summary
In the preparation of wafer-level transition metal chalcogenide single-crystal thin films, the high symmetry of the sapphire C-plane substrate leads to twin formation, which affects the single crystal properties of the film and the device performance. Furthermore, the existing methods have poor uniformity and controllability when extended to large-size films.
Using a P-plane, R-plane, or S-plane sapphire substrate with intrinsic symmetry C1v, a transition metal chalcogenide single-crystal thin film is prepared on the substrate after annealing. The intrinsic crystal properties of the sapphire substrate restrict the orientation of the crystal domains, enabling unidirectional epitaxial growth and seamless splicing.
High-quality wafer-level single-crystal thin films can be obtained without complex processing, solving the twinning problem, broadening the process window, and improving the robustness and uniformity of the preparation.
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Figure CN122013313A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of semiconductor materials technology, specifically relating to a single-crystal thin film of a transition metal chalcogenide and its preparation method. Background Technology
[0002] Transition metal dichalcogenides (TMDCs) are representative two-dimensional semiconductor materials. Due to their atomic-level thickness, excellent electrostatic control capabilities, and unique semiconductor bandgap characteristics, they are considered the most promising channel materials after silicon for supporting next-generation high-performance, low-power integrated circuits. To realize the large-scale integration of TMDCs in electronic devices, the fabrication of high-quality, wafer-level single-crystal thin films is an indispensable prerequisite.
[0003] Currently, epitaxial growth is the main method for preparing wafer-level transition metal chalcogenide single-crystal thin films, and single-crystal sapphire has become the most commonly used growth substrate due to its good thermal stability, chemical inertness, and low cost. Among existing technologies, the C-plane (0001) sapphire substrate is the most widely researched and applied. However, the sapphire C-plane possesses triple rotational symmetry (C... 3v This high symmetry leads to two energy-degenerate dominant orientations (0° and 60°) for transition metal chalcogenide domains during nucleation, and these two orientations are antiparallel to each other. During the growth of the transition metal chalcogenide thin film, several transition metal chalcogenide domains parallel to the two orientations are formed. During the splicing process, the antiparallel domains meet to form twin boundaries, which severely damages the single crystallinity of the film and leads to a significant decrease in device performance.
[0004] To address the aforementioned issues, existing technologies employ methods such as substrate beveling to create surface steps, surface passivation, and the preparation of surface transition layers to break surface symmetry, thereby inducing unidirectional alignment of crystal domains. However, these methods all rely on external artificial intervention, and when extended to the preparation of larger-sized transition metal chalcogenide single-crystal thin films, they all face problems of poor uniformity and controllability.
[0005] Therefore, in order to address the above-mentioned technical problems, it is necessary to provide a transition metal chalcogenide single crystal thin film and its preparation method. Summary of the Invention
[0006] The purpose of this invention is to provide a transition metal chalcogenide single-crystal thin film and its preparation method, which can solve the problem of twin formation from the source and conveniently prepare wafer-level high-quality transition metal chalcogenide single-crystal thin films.
[0007] To achieve the above objectives, an embodiment of the present invention provides the following technical solution:
[0008] A method for preparing a single-crystal thin film of a transition metal chalcogenide, the method comprising the following steps:
[0009] A sapphire substrate is provided, wherein the sapphire substrate is a P-plane ( ) Sapphire substrate, R-side ( ) Sapphire substrate or S-plane ( Any type of sapphire substrate;
[0010] Single-crystal thin films of transition metal chalcogenides were prepared on sapphire substrates.
[0011] In one embodiment, the surface symmetry of the sapphire substrate is C. 1v .
[0012] In one embodiment, the angle between the surface of the sapphire substrate and its standard crystal plane is -5° to 5°, and the standard crystal plane is the P-plane (…). ), R side ( ) or S-side ( Any one of them.
[0013] In one embodiment, the formation energy of the transition metal chalcogenide on the sapphire substrate has a single minimum as the orientation angle between the transition metal chalcogenide and the sapphire substrate changes.
[0014] In one embodiment, the step of preparing a transition metal chalcogenide single-crystal thin film on a sapphire substrate includes:
[0015] In the first stage, several transition metal chalcogenide domains are formed on the sapphire substrate, and all transition metal chalcogenide domains are epitaxially grown along the same direction.
[0016] In the second stage, all transition metal chalcogenide domains continue to grow and merge with each other to form a transition metal chalcogenide single crystal film, which covers the sapphire substrate.
[0017] In one embodiment, the step of preparing a transition metal chalcogenide single-crystal thin film on a sapphire substrate further includes:
[0018] The sapphire substrate is surface treated to make its surface clean and flat.
[0019] In one embodiment, the surface treatment step of the sapphire substrate is as follows:
[0020] The sapphire substrate is annealed at a temperature of 850°C to 1600°C.
[0021] In one embodiment, a single-crystal thin film of a transition metal chalcogenide is prepared on a sapphire substrate by chemical vapor deposition, physical vapor deposition, or atomic layer deposition.
[0022] In one embodiment, the transition metal chalcogenide single crystal thin film is any one of molybdenum disulfide single crystal thin film, molybdenum diselenide single crystal thin film, tungsten disulfide single crystal thin film, or tungsten diselenide single crystal thin film.
[0023] Another embodiment of the present invention provides the following technical solution:
[0024] A transition metal chalcogenide single-crystal thin film, wherein the transition metal chalcogenide single-crystal thin film is prepared by the above-described preparation method.
[0025] Compared with the prior art, the present invention has the following beneficial effects:
[0026] This invention employs C with intrinsic symmetry 1v P-side ( ) Sapphire substrate, R-side ( ) Sapphire substrate or S-plane ( Sapphire substrates, as growth substrates for transition metal chalcogenide single crystal thin films, eliminate the problem of twin formation during the growth of transition metal chalcogenide thin films from the source, and high-quality single crystal thin films at the wafer level can be obtained without complex processing of the substrate.
[0027] This invention employs C with intrinsic symmetry 1v P-side ( ) Sapphire substrate, R-side ( ) Sapphire substrate or S-plane ( Sapphire substrates, as growth substrates for single-crystal thin films of transition metal chalcogenides, successfully decouple the growth orientation of transition metal chalcogenides from the surface treatment process, avoiding the problem of uneven substrate treatment, significantly widening the process window, and improving the robustness of the fabrication. Attached Figure Description
[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0029] Figure 1 This is a process flow diagram of the method for preparing single-crystal thin films of transition metal chalcogenides in Example 1 of the present invention;
[0030] Figure 2This is a schematic diagram of the crystal structure of sapphire.
[0031] Figure 3 This is a schematic diagram of the preparation of molybdenum disulfide single crystal thin films using a three-temperature zone CVD tube furnace in Embodiment 1 of the present invention;
[0032] Figure 4 This is a schematic diagram of the atomic structure of the P-facet of sapphire.
[0033] Figure 5 The molybdenum disulfide calculated by DFT in the P-plane ( A diagram showing the formation energy on a sapphire substrate as a function of orientation angle.
[0034] Figure 6 These are optical microscope images of molybdenum disulfide domains formed on different regions of the sapphire substrate in Embodiment 1 of the present invention.
[0035] Figure 7 These are atomic force microscopy characterization images of molybdenum disulfide crystal domains formed on a sapphire substrate in Embodiment 1 of the present invention at different magnifications.
[0036] Figure 8 The images show optical microscope images and corresponding second harmonic surface scans of the molybdenum disulfide domain splicing region formed on the sapphire substrate in Embodiment 1 of the present invention.
[0037] Figure 9 This is a photograph of the molybdenum disulfide single-crystal thin film prepared in Example 1 of the present invention;
[0038] Figure 10 The images shown are optical microscope images and corresponding second harmonic surface scans of the molybdenum disulfide single crystal thin film prepared in Example 1 of this invention.
[0039] Figure 11 These are atomic force microscopy characterization images of molybdenum disulfide domains formed on a sapphire substrate at different magnifications in Embodiment 2 of the present invention.
[0040] Figure 12 This is a schematic diagram of the crystal structure of sapphire.
[0041] Figure 13 This is a schematic diagram of the atomic structure of the R-facet of sapphire.
[0042] Figure 14 The molybdenum disulfide calculated by DFT in the R-plane ( A diagram showing the formation energy on a sapphire substrate as a function of orientation angle.
[0043] Figure 15 This is an optical microscope image of the molybdenum disulfide domains formed on the sapphire substrate in Embodiment 3 of the present invention.
[0044] Figure 16 This is a photograph of the molybdenum disulfide single-crystal thin film prepared in Example 3 of the present invention;
[0045] Figure 17 The images shown are optical microscope images and corresponding second harmonic surface scans of the molybdenum disulfide single crystal thin film prepared in Example 3 of this invention.
[0046] Figure 18 This is a schematic diagram of the atomic structure of the S-facet of sapphire.
[0047] Figure 19 The molybdenum disulfide calculated by DFT is located on the S-plane ( A diagram showing the formation energy on a sapphire substrate as a function of orientation angle.
[0048] Figure 20 This is an optical microscope image of the molybdenum disulfide domains formed on the sapphire substrate in Example 4 of the present invention.
[0049] Figure 21 This is a photograph of the molybdenum disulfide single-crystal thin film prepared in Example 4 of the present invention;
[0050] Figure 22 The images shown are optical microscope images and corresponding second harmonic surface scans of the molybdenum disulfide single crystal thin film prepared in Example 4 of this invention. Detailed Implementation
[0051] To enable those skilled in the art to better understand the technical solutions in this disclosure, the technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this disclosure.
[0052] This invention discloses a method for preparing single-crystal thin films of transition metal chalcogenides, comprising the following steps:
[0053] Provide a sapphire substrate, the sapphire substrate being P-plane ( ) Sapphire substrate, R-side ( ) Sapphire substrate or S-plane ( Any type of sapphire substrate;
[0054] Single-crystal thin films of transition metal chalcogenides were prepared on sapphire substrates.
[0055] The present invention also discloses a transition metal chalcogenide single crystal thin film, which is prepared by the above-described preparation method.
[0056] The present invention will be further described below in conjunction with specific examples.
[0057] Example 1:
[0058] Refer to Figure 1 As shown, the preparation method of the transition metal chalcogenide single crystal thin film in this example includes the following steps:
[0059] S1. Provide a sapphire substrate, which is any one of a P-plane ( ), R-plane ( ), or S-plane ( ) sapphire substrate.
[0060] Further, compared with the prior art, the preparation method in this example does not require precise control of the beveling direction of the sapphire substrate. That is, the surface of the sapphire substrate does not need to be strictly coincident with its standard crystal plane (any one of the P-plane ( ), R-plane ( ), or S-plane ( )) (the included angle is the theoretical value of 0.00°). The included angle between the two is within the range of -5° to 5°, and the symmetry of the surface used for growing the transition metal chalcogenide single crystal thin film satisfies the intrinsic symmetry C 1v That's all.
[0061] Specifically, refer to Figure 2 As shown, the sapphire substrate in this example is a P-plane ( ) sapphire substrate, that is, its standard crystal plane is the P-plane ( ). The sapphire P-plane is obtained by rotating the sapphire C-plane (0001) around the M-axis < > by 61.2°.
[0062] In addition, steps extending along the M-axis of the sapphire are formed on the surface of the sapphire substrate in this example.
[0063] Further, before growing the transition metal chalcogenide single crystal thin film, surface treatment of the sapphire substrate is also included to make the surface of the sapphire substrate clean and flat.
[0064] Specifically, in this example, the surface treatment of the sapphire substrate is carried out in an air or inert gas atmosphere at an annealing temperature of 850°C to 1600°C to obtain a clean and flat surface.
[0065] S2. Prepare a transition metal chalcogenide single crystal thin film on the sapphire substrate.
[0066] Further, the transition metal chalcogenide single crystal thin film includes but is not limited to any one of molybdenum disulfide single crystal thin film, molybdenum diselenide single crystal thin film, tungsten disulfide single crystal thin film or tungsten diselenide single crystal thin film. The transition metal chalcogenide single crystal thin film in this embodiment is a molybdenum disulfide single crystal thin film.
[0067] As shown Figure 3 in, in this embodiment, the molybdenum disulfide single crystal thin film is prepared on a sapphire substrate by a Chemical Vapor Deposition (CVD) process. First, sulfur powder and molybdenum trioxide powder as precursors are respectively placed in the first temperature zone and the second temperature zone of a three-temperature zone CVD tube furnace, and the sapphire substrate is placed in the third temperature zone of the three-temperature zone CVD tube furnace; the three-temperature zone CVD tube furnace is evacuated to a vacuum degree below 10 Pa, and 100 sccm of argon gas is introduced; after the temperatures of the first temperature zone, the second temperature zone and the third temperature zone are respectively raised to 150 °C, 550 °C and 950 °C, 5 sccm of oxygen gas is introduced; the reaction is carried out in the three-temperature zone CVD tube furnace. After the reaction is completed, the introduction of oxygen gas is stopped, the heating of the second temperature zone and the third temperature zone is stopped, and the remaining molybdenum trioxide powder is taken out; after the sapphire substrate is cooled to 250 °C in an argon and sulfur atmosphere, the heating of the first temperature zone (sulfur powder) is stopped; after the sapphire substrate on which the reaction is completed is naturally cooled to room temperature, it is taken out.
[0068] It should be noted that the reaction time should be reasonably controlled according to actual needs. If the reaction time is insufficient, several transition metal chalcogenide crystal domains arranged epitaxially in the same direction will be formed on the sapphire substrate. As the reaction time is extended, these transition metal chalcogenide crystal domains will continue to grow and merge and splice to form a transition metal chalcogenide single crystal thin film, finally covering the entire sapphire substrate.
[0069] It should be understood that in other multiple embodiments, other processes capable of realizing the epitaxial growth of the transition metal chalcogenide single crystal thin film, such as physical vapor deposition process or atomic layer deposition process, can also be used to prepare the transition metal chalcogenide single crystal thin film on the sapphire substrate.
[0070] More specifically, this step includes:
[0071] (1) In the first stage, several transition metal chalcogenide crystal domains are formed on the sapphire substrate, and all the transition metal chalcogenide crystal domains grow epitaxially along the same direction.
[0072] As shown Figure 4 and Figure 5 , since the P-plane ( ) sapphire substrate has an intrinsic symmetry C 1v , the results obtained by DFT calculation show that with molybdenum disulfide and the P-plane ( ), the change in the orientation angle between sapphire substrates, and the formation energy of molybdenum disulfide on the P-plane ( ) sapphire substrate has a single minimum value, and the orientation corresponding to the lowest energy point has a thermodynamic stability advantage, which can limit the epitaxial nucleation of molybdenum disulfide in a specific direction.
[0073] See Figure 6 and Figure 7 . As shown, several molybdenum disulfide domains all exhibit a typical triangular morphology on the surface of the P-plane ( ) sapphire substrate, and on the P-plane ( ) sapphire substrate, the ZIGZAG edge ( direction) of molybdenum disulfide is always parallel to the M-axis direction of sapphire, that is, all triangular molybdenum disulfide domains grow epitaxially in the same direction. This macroscopic orientation consistency intuitively confirms that the intrinsic low symmetry of the sapphire substrate does strictly limit the nucleation of molybdenum disulfide to a single thermodynamically stable direction, thus successfully achieving the single-direction epitaxial growth of molybdenum disulfide on the sapphire substrate surface. The specific one-way arrangement shown by the characterization results, that is, the epitaxial configuration between molybdenum disulfide and the sapphire substrate is exactly the same as the configuration with the lowest energy predicted by the DFT theory. It is proved that by using the thermodynamic energy minimum matching mechanism between the sapphire substrate lattice and the single crystal thin film of transition metal chalcogenide, the orientation degeneracy of the nucleation of transition metal chalcogenide domains is broken, and the spontaneous one-way arrangement of transition metal chalcogenide domains can be achieved without relying on a specific surface step orientation or surface passivation, so that high-quality single crystal thin films at the wafer level can be obtained at low cost and high efficiency.
[0074] (2) In the second stage, all transition metal chalcogenide domains continue to grow and fuse and join together to form a transition metal chalcogenide single crystal thin film, and the transition metal chalcogenide single crystal thin film covers the sapphire substrate.
[0075] See Figure 8 . As shown, the second harmonic generation (SHG) signal between the locally joined one-way arranged molybdenum disulfide domains shows a uniform signal intensity, and there is no obvious intensity attenuation at the joining place, proving that the adjacent triangular molybdenum disulfide domains have a consistent lattice orientation and seamless joining is achieved.
[0076] See Figure 9 . As shown, after sufficient reaction growth, several molybdenum disulfide domains grow and join together to form a large-area single crystal thin film. Combining Figure 10As shown, the second harmonic generation surface scanning (SHG mapping) was performed on the single crystal thin film of transition metal chalcogenide prepared by the preparation method in this embodiment. The results show that the signal intensity in the entire scanning area is uniform and no obvious grain boundary characteristics are observed, further proving the single crystal property of the large-area molybdenum disulfide thin film prepared.
[0077] Compared with the prior art, the intrinsic property of the crystal plane of the sapphire substrate is utilized in this embodiment to completely solve the twin crystal problem. Through this intrinsic thermodynamic selection mechanism, the degeneracy of the crystal domain orientation is successfully broken, and the problem of twin crystal formation during the growth of transition metal chalcogenide thin films is eradicated from the source. High-quality single crystal thin films of transition metal chalcogenides at the wafer level can be obtained without complex treatment of the substrate, and it is applicable to the growth of various single crystal thin films of transition metal chalcogenides, with strong universality.
[0078] Example 2:
[0079] The single crystal thin film of transition metal chalcogenide and its preparation method in this embodiment are substantially the same as those in Example 1, except that the step direction on the surface of the P-plane ( ) sapphire substrate is not parallel to the M axis, that is, the beveling direction of the sapphire substrate in this embodiment is different from that in Example 1.
[0080] As shown in Figure 11 , the ZIGZAG edges of the molybdenum disulfide crystal domains formed on the sapphire substrate are not parallel to the step edges on the surface of the sapphire substrate, but several molybdenum disulfide crystal domains still arrange along a single direction. This result shows that no matter in which direction the steps on the surface of the sapphire substrate with intrinsic symmetry C 1v extend, the epitaxial orientation of the formed molybdenum disulfide crystal domains does not change and always strictly follows the specific epitaxial relationship described in Example 1.
[0081] Compared with the prior art that heavily relies on artificial means to guide the single crystal growth of thin films, once the processing accuracy is insufficient, the growth orientation will get out of control, and it is difficult to control the uniformity when growing large-area thin films. Using the sapphire substrate with intrinsic symmetry C 1v as the growth substrate for the single crystal thin film of transition metal chalcogenide, the growth orientation of transition metal chalcogenides is successfully decoupled from the surface treatment process, significantly broadening the process window and improving the preparation robustness.
[0082] Example 3:
[0083] The single crystal thin film of transition metal chalcogenide and its preparation method in this embodiment are substantially the same as those in Example 1, except that the sapphire substrate in this embodiment is an R-plane ( ) sapphire substrate.
[0084] Specifically, referring to Figure 12 as shown, the sapphire substrate in this embodiment is an R-plane ( ) sapphire substrate, that is, its standard crystal plane is the R-plane ( ), and the sapphire R-plane is obtained by rotating the sapphire C-plane (0001) around the A-axis < > by 57.6°.
[0085] Referring to Figure 13 and Figure 14 as shown, similar to Embodiment 1, due to the intrinsic symmetry C of the R-plane ( ) sapphire substrate, the results obtained by DFT calculation show that with the change of the orientation angle between molybdenum disulfide and the R-plane ( 1v ) sapphire substrate, the formation energy of molybdenum disulfide on the R-plane ( ) sapphire substrate also has a single minimum value, and the orientation corresponding to the lowest energy point has a thermodynamic stability advantage, so that the epitaxial nucleation of molybdenum disulfide can also be limited to a specific direction. ).
[0086] Referring to Figure 15 as shown, in this embodiment, several transition metal chalcogenide crystal domains formed in the first stage also grow epitaxially along the same direction.
[0087] Referring to Figure 16 as shown, with the extension of the reaction growth time, several molybdenum disulfide crystal domains formed in the first stage in this embodiment also grow and finally merge into a large-area single-crystal thin film.
[0088] Referring to Figure 17 as shown, the second-harmonic surface scanning results show that the signal intensity in the entire scanning area is uniform and no obvious grain boundary characteristics are observed, indicating that a large-area and high-quality molybdenum disulfide single-crystal thin film is also successfully prepared in this embodiment.
[0089] Embodiment 4:
[0090] The transition metal chalcogenide single-crystal thin film and its preparation method in this embodiment are substantially the same as those in Embodiment 1, except that the sapphire substrate in this embodiment is an S-plane ( ) sapphire substrate.
[0091] Specifically, referring to Figure 12 as shown, the sapphire substrate in this embodiment is an S-plane ( ) sapphire substrate, that is, its standard crystal plane is the S-plane ( ), and the sapphire S-plane is obtained by rotating the sapphire C-plane (0001) around the A-axis < > by 72.4°.
[0092] Reference Figure 18 and Figure 19 As shown, similar to Example 1, since the S-plane ( ) sapphire substrate has an intrinsic symmetry C 1v , the results obtained by DFT calculations show that as the orientation angle between molybdenum disulfide and the S-plane ( ) sapphire substrate changes, the formation energy of molybdenum disulfide on the S-plane ( ) sapphire substrate also has a single minimum value. The orientation corresponding to the lowest energy point has a thermodynamic stability advantage, thus being able to limit the epitaxial nucleation of molybdenum disulfide to a specific direction as well.
[0093] Reference Figure 20 As shown, in this embodiment, several transition metal chalcogenide domains formed in the first stage also grow epitaxially along the same direction.
[0094] Reference Figure 21 As shown, as the reaction growth time extends, several molybdenum disulfide domains formed in the first stage in this embodiment also grow and finally merge into a large-area single-crystal thin film.
[0095] Reference Figure 22 As shown, the second harmonic surface scanning results show that the signal intensity in the entire scanning area is uniform and no obvious grain boundary features are seen, indicating that a large-area and high-quality molybdenum disulfide single-crystal thin film is also successfully prepared in this embodiment.
[0096] From the above technical solutions, the present invention has the following beneficial effects:
[0097] The present invention uses a P-plane ( 1v ) sapphire substrate, an R-plane ( ) sapphire substrate or an S-plane ( ) sapphire substrate with an intrinsic symmetry C as the growth substrate for the transition metal chalcogenide single-crystal thin film, eradicating the problem of twin formation during the growth of the transition metal chalcogenide thin film from the source. High-quality single-crystal thin films at the wafer level can be obtained without complex treatment of the substrate;
[0098] The present invention uses a P-plane ( 1v ) sapphire substrate, an R-plane ( ) sapphire substrate or an S-plane ( ) sapphire substrate with an intrinsic symmetry C as the growth substrate for the transition metal chalcogenide single-crystal thin film, successfully decoupling the growth orientation of the transition metal chalcogenide from the surface treatment process, avoiding the problem of uneven substrate treatment, significantly broadening the process window, and improving the preparation robustness.
[0099] It will be apparent to those skilled in the art that this disclosure is not limited to the details of the exemplary embodiments described above, and that this disclosure can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of this disclosure is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this disclosure. No reference numerals in the claims should be construed as limiting the scope of the claims.
[0100] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.
Claims
1. A method for preparing a single-crystal thin film of a transition metal chalcogenide, characterized in that, The preparation method includes the following steps: A sapphire substrate is provided, wherein the sapphire substrate is a P-plane ( ) Sapphire substrate, R-side ( ) Sapphire substrate or S-plane ( Any type of sapphire substrate; Single-crystal thin films of transition metal chalcogenides were prepared on sapphire substrates.
2. The method for preparing a single-crystal thin film of a transition metal chalcogenide according to claim 1, characterized in that, The symmetry of the surface of the sapphire substrate is C. 1v .
3. The method for preparing a single-crystal thin film of a transition metal chalcogenide according to any one of claims 1 or 2, characterized in that, The angle between the surface of the sapphire substrate and its standard crystal plane is -5° to 5°, and the standard crystal plane is the P-plane ( ), R side ( ) or S-side ( Any one of them.
4. The method for preparing a single-crystal thin film of a transition metal chalcogenide according to claim 1, characterized in that, The formation energy of transition metal chalcogenides on sapphire substrates has a single minimum value as the orientation angle between the transition metal chalcogenide and the sapphire substrate changes.
5. The method for preparing a single-crystal thin film of a transition metal chalcogenide according to claim 1, characterized in that, The steps for preparing transition metal chalcogenide single-crystal thin films on sapphire substrates include: In the first stage, several transition metal chalcogenide domains are formed on the sapphire substrate, and all transition metal chalcogenide domains are epitaxially grown along the same direction. In the second stage, all transition metal chalcogenide domains continue to grow and merge with each other to form a transition metal chalcogenide single crystal film, which covers the sapphire substrate.
6. The method for preparing a single-crystal thin film of a transition metal chalcogenide according to claim 1, characterized in that, The step of preparing a transition metal chalcogenide single-crystal thin film on a sapphire substrate also includes: The sapphire substrate is surface treated to make its surface clean and flat.
7. The method for preparing a single-crystal thin film of a transition metal chalcogenide according to claim 6, characterized in that, The steps for surface treatment of the sapphire substrate are as follows: The sapphire substrate is annealed at a temperature of 850°C to 1600°C.
8. The method for preparing a single-crystal thin film of a transition metal chalcogenide according to claim 1, characterized in that, Transition metal chalcogenide single-crystal thin films are prepared on sapphire substrates using chemical vapor deposition, physical vapor deposition, or atomic layer deposition.
9. The method for preparing a single-crystal thin film of a transition metal chalcogenide according to claim 1, characterized in that, The transition metal chalcogenide single crystal thin film is any one of molybdenum disulfide single crystal thin film, molybdenum diselenide single crystal thin film, tungsten disulfide single crystal thin film, or tungsten diselenide single crystal thin film.
10. A single-crystal thin film of a transition metal chalcogenide, characterized in that, The transition metal chalcogenide single-crystal thin film is prepared by the preparation method according to any one of claims 1 to 9.