Rare earth doped MX2 heterojunction and preparation method thereof

Abstract

The invention discloses a rare earth doped MX2 heterojunction and a preparation method thereof. The preparation method comprises the following steps: cleaning a silicon wafer substrate, preparing a mixed solution from oxysalts of two M metals, trivalent rare earth chloride and deionized water, and carrying out ultrasonic dispersion; weighing sodium cholate, adding the sodium cholate into the mixed solution subjected to ultrasonic treatment, stirring to obtain a precursor solution, sucking the precursor solution, dripping the precursor solution on the surface of a silicon wafer substrate, and carrying out spin coating; a tubular furnace is adopted for chemical vapor deposition reaction, a porcelain boat containing an X source is placed in a low-temperature area of an air inlet of the tubular furnace, and a silicon wafer substrate coated with a precursor solution is placed in a central temperature area of the tubular furnace; and after the system is heated to a specified temperature, the X source is conveyed to the surface of the silicon wafer to react with the two M sources, so that the preparation of the rare earth doped heterojunction is realized. The rare earth element doped MX2 heterojunction is prepared by a one-step method by using a liquid phase precursor assisted CVD preparation process, and the luminescent property of the heterojunction is improved by introducing rare earth.

Description

Technical Field

[0001] The present invention belongs to the field of two-dimensional material preparation, and specifically relates to a rare earth-doped MX2 heterojunction and a preparation method thereof. Background Art

[0002] MX2 (M = W, Mo, X = S or Se) is a typical graphene-like layered two-dimensional material. Since graphene was first prepared by mechanical exfoliation in 2004, two-dimensional materials have become a frontier of research in materials science and condensed matter physics due to their unique atomically thin structure and other excellent properties. MX2 has a unique layered structure, with a transition metal atom Mo or W in the middle layer and chalcogen atoms S or Se on either side. The layers are bonded by weak van der Waals forces and strong covalent bonds within the layers. A van der Waals heterojunction is a material formed by vertically stacking two or more different two-dimensional materials with atomic-level precision using van der Waals forces. This allows for the stacking of materials with different lattice constants and relatively flexible material combinations. In addition to nearly universal coverage of material types, structural manipulation in multiple dimensions, such as stacking order and rotation angle, can also induce diverse properties. Atomically flat interfaces ensure no atomic diffusion across the interface. These unique structures give van der Waals heterojunctions unique band structures and tunable electronic structures, resulting in widespread applications in electronics, optoelectronics, and quantum technology. Rare earth elements have unfilled 4f electron orbitals. This unique electronic structure makes their internal energy levels very rich and stable, and can produce multiple energy level transitions, covering the band from ultraviolet light to infrared light. When they are doped into MX2, they can be used through mechanisms such as electronic structure modulation, defect engineering, and energy transfer, making rare earth-doped MX2 materials widely used in fields such as photoelectric detection.

[0003] In the studies that have been reported, most of the research on growing heterojunctions is a two-step growth method, and most of them are dry synthesis. In addition, the research on doping heterojunctions is mostly done with transition metal elements such as Fe, Re, V, and Nb. So far, there has been no report on the one-step preparation of rare earth element doped MX2 heterojunctions. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a rare earth doped MX2 heterojunction and a preparation method thereof, and to prepare the rare earth element doped MX2 heterojunction in one step by using a liquid precursor assisted CVD preparation process.

[0005] To solve the above technical problems, according to one aspect of the present invention, a method for preparing a rare earth-doped MX2 heterojunction is provided, comprising: Step 1: Cleaning the silicon wafer substrate; Step 2: preparing a mixed solution using two M metal oxyacid salts, trivalent rare earth chloride and deionized water; Step 3: Ultrasonic dispersion of the mixed solution prepared in step 2 to achieve uniform dispersion of the elements; Step 4, weighing sodium cholate and adding it to the mixed solution after ultrasonication, stirring to obtain a precursor solution; Step 5: Place the cleaned silicon wafer substrate in the center of the spin coater, draw the precursor solution obtained in step 4, and drop it on the surface of the silicon wafer substrate for spin coating; In step six, a chemical vapor deposition reaction is carried out in a tube furnace. A porcelain boat containing an X source is placed in the low-temperature zone of the tube furnace's air inlet, and a silicon wafer substrate coated with a precursor solution is placed in the central temperature zone of the tube furnace. A carrier gas is introduced, and when the system is heated to the specified temperature, the X source is transported to the surface of the silicon wafer to react with the two M sources, thereby fabricating a rare earth-doped heterojunction.

[0006] Furthermore, in step one, the silicon wafer substrate is cleaned with acetone, anhydrous ethanol, and deionized water in sequence.

[0007] Furthermore, in step 2, the oxygen-containing salt of the M metal is selected from ammonium molybdate, ammonium tungstate or hydrates thereof.

[0008] Furthermore, in step 2, the trivalent rare earth chloride is selected from ErCl3 or YbCl3.

[0009] Furthermore, in step 2, the oxygen-containing salts of two M metals are prepared with deionized water to obtain solution A for growing a pure phase heterojunction; trivalent rare earth chloride is dissolved in deionized water to prepare solution B, and solution B is added to solution A to obtain a mixed solution.

[0010] Furthermore, in step 2, trivalent rare earth chloride is dissolved in deionized water to prepare a solution with a concentration of 0.1 mg / mL.

[0011] Furthermore, in step three, the ultrasound duration is set to 30-50 minutes.

[0012] Furthermore, in step six, the system temperature is raised from room temperature to 600°C within 20 minutes, raised to 750°C within 16 minutes, and kept at 750°C for 5 minutes before the program ends.

[0013] Furthermore, in step six, the carrier gas is argon, and after argon purge for 3 to 10 minutes, the gas flow rate is maintained at 120 sccm.

[0014] According to another aspect of the present invention, provided is a rare earth-doped MX2 heterojunction obtained by any one of the above methods.

[0015] The present invention utilizes a liquid-phase precursor-assisted CVD growth method, selects trivalent rare earth chloride and different M sources to prepare a mixed solution, and performs direct growth in one step, successfully realizing the doping of MX2 heterojunction with rare earth elements. The introduction of rare earth improves the luminescence performance of the heterojunction. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the CVD reaction principle of the rare earth-doped MX2 heterojunction prepared in Example 1; Figure 2 is an optical microscope image of the rare earth-doped MX2 heterojunction prepared in Example 1; Figure 3 is an optical microscope image of the rare earth-doped MX2 heterojunction prepared in Example 3; Figure 4 is an AFM height image of the rare earth-doped MX2 heterojunction prepared in Example 3; Figure 5 This is the HAADF-STEM atomic image of the rare earth-doped MX2 heterojunction prepared in Example 3.

[0017] Figure 6 This is a comparison picture of the Raman spectra test of the rare earth-doped MX2 heterojunction prepared in Example 3 and the undoped heterojunction; Figure 7 This is a comparison picture of the fluorescence spectrum test of the rare earth-doped MX2 heterojunction prepared in Example 3 and the undoped heterojunction. DETAILED DESCRIPTION

[0018] A typical embodiment of the present invention provides a method for preparing a rare earth-doped MX2 heterojunction. This embodiment realizes the controllable preparation of a rare earth-doped MX2 heterojunction based on a liquid precursor and chemical vapor deposition method, including the following steps 1 to 6.

[0019] Step 1: Cleaning the substrate: Clean the silicon wafer substrate multiple times to thoroughly remove impurities on the substrate.

[0020] Relatively specifically, the cleaning of the substrate described in this step is to place a beaker in an ultrasonic cleaner, place a silicon wafer cleaning rack in the beaker, place the cut silicon wafer on the cleaning rack, and replace the cleaning agent in the order of acetone → anhydrous ethanol → deionized water. The cleaning time is set to 10 minutes each time. After cleaning, the cleaned silicon wafer is blown dry with a nitrogen gun.

[0021] Step 2: Preparation of a mixed solution: A mixed solution for growing a rare earth doped heterojunction is prepared using two oxygen-containing salts of M metals, a trivalent rare earth chloride and deionized water.

[0022] In this step, the M metal is W or Mo. Exemplarily, the oxyacid salt of the M metal is selected from ammonium molybdate, ammonium tungstate, ammonium molybdate tetrahydrate or ammonium tungstate hydrate; and the trivalent rare earth chloride is selected from ErCl3 or YbCl3.

[0023] A relatively specific method for preparing the mixed solution is: two oxygen-containing salts of M metals are prepared with deionized water to obtain solution A for growing a pure phase heterojunction; trivalent rare earth chloride is dissolved in deionized water to prepare solution B with a concentration of 0.1 mg / mL, and solution B is added to the above solution A to obtain a mixed solution for growing a rare earth-doped heterojunction.

[0024] Step 3: Ultrasonic treatment of the mixed solution: Ultrasonic dispersion of the mixed solution prepared in step 2 is performed to achieve uniform dispersion of the elements.

[0025] Specifically, in this step, the prepared mixed solution is placed in an ultrasonic cleaning instrument for ultrasonication, and the ultrasonication time is set to 30 to 50 minutes until a clear and transparent mixed solution is obtained. After cooling to room temperature, a mixed solution in which various elements are uniformly dispersed is obtained.

[0026] Step 4, adding sodium cholate and stirring: weighing sodium cholate and adding it to the ultrasonicated mixed solution, and building a chemical equilibrium system by stirring.

[0027] Illustratively, in this step, 150 mg of sodium cholate powder is weighed and added to the mixed solution cooled to room temperature. A stirrer is added, and the mixture is placed on a magnetic stirrer and stirred until fully mixed and dissolved into an emulsion, thereby obtaining a chemically balanced precursor solution.

[0028] Step 5: Spin coating the precursor: Place the cleaned silicon wafer in the center of the spin coater, absorb the precursor solution, and drop it on the surface of the silicon wafer for spin coating.

[0029] Exemplarily, in the steps, the cleaned silicon wafer is placed in the center of the spin coater, the vacuum pump is turned on for adsorption and fixation, the precursor solution is absorbed, a drop is dropped on the center of the silicon wafer surface, and spin coating is performed at 2500 rpm for 1 minute.

[0030] Step 6: Use a tube furnace to perform chemical vapor deposition: Place a porcelain boat containing an X source in the low-temperature zone of the tube furnace's air inlet, and place a silicon wafer coated with a precursor solution in the center temperature zone of the tube furnace. Then, introduce a carrier gas, and when the system heats up to the specified temperature, the X source is transported to the substrate surface to react with the two M sources to prepare a rare earth-doped heterojunction.

[0031] The X source mentioned above is S or Se. For example, when performing a chemical vapor deposition reaction, a porcelain boat containing an X source is first placed in the low-temperature area of the tube furnace's air inlet. A silicon wafer coated with a precursor solution is placed flat on another porcelain boat with the coated surface facing up. This porcelain boat is then placed in the center temperature zone of the tube furnace. After purging with argon for 3 to 10 minutes, a gas flow rate of 120 seem is maintained. The tube furnace's heating program is set as follows: from room temperature to 600°C within 20 minutes, then to 750°C within 16 minutes, and then maintained at 750°C for 5 minutes. The program ends, and after the furnace cools naturally to room temperature, the flow meter is turned off and the silicon wafer is removed. At this point, the rare earth-doped MX2 heterojunction is completed.

[0032] The technical solutions claimed in the present invention are further illustrated below by means of some examples. However, the examples are intended to illustrate the embodiments of the present invention and do not exceed the scope of the subject matter of the present invention. The scope of protection of the present invention is not limited by the examples. Unless otherwise specified, the materials and reagents used in the present invention can be obtained from commercial products in the art. Example 1

[0033] Cleaning of the substrate: Place a beaker in the ultrasonic cleaner, place a silicon wafer cleaning rack in the beaker, place the cut silicon wafer on the cleaning rack, add cleaning agent to the beaker, and replace the cleaning agent in the order of acetone → anhydrous ethanol → deionized water. The cleaning time is set to 10 minutes each time. After cleaning, use a nitrogen gun to blow dry the cleaned silicon wafer.

[0034] Weigh 5 mg of ammonium molybdate tetrahydrate and 15 mg of ammonium tungstate hydrate, add them into a beaker and prepare solution A with deionized water. Dissolve ErCl3 in deionized water to prepare an ErCl3 solution with a concentration of 0.1 mg / mL. Measure 3.25 mL of ErCl3 solution and add it to solution A to prepare 10 mL of a mixed solution.

[0035] Place 10 mL of the prepared mixed solution in an ultrasonic cleaning apparatus for ultrasonication. The ultrasonication time is set to 30 to 50 minutes until a clear and transparent mixed solution is obtained. After cooling to room temperature, a mixed solution in which various elements are evenly dispersed is obtained.

[0036] 150 mg of sodium cholate was weighed and added to the mixed solution cooled to room temperature. A stirring bar was added and the mixture was placed on a magnetic stirrer and stirred until it was fully mixed and dissolved into an emulsion, thereby obtaining a chemically balanced precursor solution.

[0037] Take a cleaned silicon wafer and place it in the center of the spin coater. Turn on the vacuum pump to adsorb and fix it. Absorb the precursor solution and drop a drop on the center of the silicon wafer surface. Spin coat at 2500 rpm for 1 minute to obtain a silicon wafer substrate coated with the precursor solution.

[0038] A porcelain boat filled with S powder is placed in the low-temperature area of the air inlet of the tubular furnace, and the silicon wafer coated with the precursor solution is placed flat on another porcelain boat with the coated surface facing up. The porcelain boat is placed in the central temperature zone of the tubular furnace. After purging with argon for 5 minutes, the gas flow rate is maintained at 120 sccm. The heating program of the tubular furnace is set as follows: from room temperature to 600°C within 20 minutes, and to 750°C within 16 minutes. After keeping warm at 750°C for 5 minutes, the program ends and the growth is completed. After waiting for the furnace to cool naturally to room temperature, the flow meter is turned off and the silicon wafer is taken out. At this time, the rare earth Er-doped WS2 / MoS2 heterojunction is completed.

[0039] Through the above experimental steps, rare earth Er-doped WS2 / MoS2 heterojunction was successfully prepared in one step.

[0040] The CVD reaction principle diagram of the rare earth Er-doped WS2 / MoS2 heterojunction prepared in this example is shown in the figure. Figure 1 shown.

[0041] The optical microscope image of the rare earth Er-doped WS2 / MoS2 heterojunction prepared in this example is as follows: Figure 2 As shown, the morphology of the upper and lower layers are both equilateral triangles with a smooth surface, which is consistent with the reported WS2 / MoS2 heterojunction morphology. Example 2

[0042] (1) Cleaning of the substrate: Place a beaker in the ultrasonic cleaner, place a silicon wafer cleaning rack in the beaker, place the cut silicon wafer on the cleaning rack, add cleaning agent to the beaker, and replace the cleaning agent in the order of acetone → anhydrous ethanol → deionized water. The cleaning time is set to 10 minutes each time. After cleaning, use a nitrogen gun to blow dry the cleaned silicon wafer.

[0043] (2) Weigh 5 mg of ammonium molybdate tetrahydrate and 15 mg of ammonium tungstate hydrate, add them to a beaker and prepare solution A with deionized water. Dissolve YbCl3 in deionized water to prepare a YbCl3 solution with a concentration of 0.1 mg / mL. Measure 3.25 mL of YbCl3 solution and add it to solution A to prepare 10 mL of mixed solution.

[0044] (3) Place 10 mL of the prepared mixed solution in an ultrasonic cleaning instrument for ultrasonication. The ultrasonication time is set to 30 to 50 minutes until a clear and transparent mixed solution is obtained. After cooling to room temperature, a mixed solution in which various elements are evenly dispersed is obtained.

[0045] (4) Weigh 150 mg of sodium cholate and add it to the mixed solution cooled to room temperature. Add a stirrer and place it on a magnetic stirrer to stir until it is fully mixed and dissolved into an emulsion, thus obtaining a chemically balanced precursor solution.

[0046] (5) Take a clean silicon wafer and place it in the center of the coating machine. Turn on the vacuum pump to adsorb and fix it. Absorb the precursor solution and drop a drop on the center of the silicon wafer surface. Spin coat at 2500 rpm for 1 minute to obtain a silicon wafer substrate coated with the precursor solution.

[0047] (6) Place a porcelain boat filled with S powder in the low-temperature area of the tube furnace's air inlet, place the silicon wafer coated with the precursor solution on another porcelain boat with the coating surface facing up, and place the porcelain boat in the central temperature zone of the tube furnace. After purging with argon for 3 minutes, maintain a gas flow rate of 120 sccm, and set the heating program of the tube furnace as follows: from room temperature to 600°C within 20 minutes, and to 750°C within 16 minutes. After keeping at 750°C for 5 minutes, the program ends and the growth is completed. After waiting for the furnace to cool naturally to room temperature, turn off the flow meter and take out the silicon wafer. At this time, the rare earth Yb-doped WS2 / MoS2 heterojunction is completed.

[0048] Through the above experimental steps, rare earth Yb-doped WS2 / MoS2 heterojunction was successfully prepared in one step. Example 3

[0049] (1) Cleaning of the substrate: Place a beaker in the ultrasonic cleaner, place a silicon wafer cleaning rack in the beaker, place the cut silicon wafer on the cleaning rack, add cleaning agent to the beaker, and replace the cleaning agent in the order of acetone → anhydrous ethanol → deionized water. The cleaning time is set to 10 minutes each time. After cleaning, use a nitrogen gun to blow dry the cleaned silicon wafer.

[0050] (2) Weigh 5 mg of ammonium molybdate tetrahydrate and 15 mg of ammonium tungstate hydrate, add them to a beaker and prepare solution A with deionized water. Dissolve ErCl3 and YbCl3 in deionized water to prepare ErCl3 solution and YbCl3 solution with a concentration of 0.1 mg / mL, respectively. Measure 1.625 mL of ErCl3 solution and YbCl3 solution, respectively, and add them to solution A to prepare 10 mL of mixed solution.

[0051] (3) Place 10 mL of the prepared mixed solution in an ultrasonic cleaning instrument for ultrasonication. The ultrasonication time is set to 30 to 50 minutes until a clear and transparent mixed solution is obtained. After cooling to room temperature, a mixed solution in which various elements are evenly dispersed is obtained.

[0052] (4) Weigh 150 mg of sodium cholate and add it to the mixed solution cooled to room temperature. Add a stirrer and place it on a magnetic stirrer to stir until it is fully mixed and dissolved into an emulsion, thus obtaining a chemically balanced precursor solution.

[0053] (5) Take a clean silicon wafer and place it in the center of the coating machine. Turn on the vacuum pump to adsorb and fix it. Absorb the precursor solution and drop a drop on the center of the silicon wafer surface. Spin coat at 2500 rpm for 1 minute to obtain a silicon wafer substrate coated with the precursor solution.

[0054] (6) Place a porcelain boat filled with S powder in the low-temperature area of the tube furnace inlet, and place the silicon wafer coated with the precursor solution on another porcelain boat with the coating surface facing up. Place the porcelain boat in the central temperature zone of the tube furnace, purge with argon for 10 minutes, maintain a gas flow of 120 sccm, and set the heating program of the tube furnace as follows: from room temperature to 600°C within 20 minutes, and to 750°C within 16 minutes. After keeping at 750°C for 5 minutes, the program ends and the growth is completed. After waiting for the furnace to cool naturally to room temperature, turn off the flow meter and take out the silicon wafer. At this time, the rare earth Er and Yb co-doped WS2 / MoS2 heterojunction is completed.

[0055] Through the above experimental steps, rare earth Er and Yb co-doped WS2 / MoS2 heterojunction was successfully prepared in one step.

[0056] The optical microscope image of the rare earth Er and Yb co-doped WS2 / MoS2 heterojunction prepared in this example is as follows: Figure 3 shown.

[0057] The AFM height image of the rare earth Er and Yb co-doped WS2 / MoS2 heterojunction prepared in this example is shown in Figure 2. Figure 4 As shown, the upper layer height is 0.7nm and the lower layer height is 0.85nm, which are consistent with the height characteristics of single-layer MX2.

[0058] The HAADF-ATEM atomic image of the Er and Yb co-doped WS2 / MoS2 heterojunction prepared in this example is shown in Figure 2. Figure 5 As shown in the figure, since the HAADF intensity is positively correlated with the atomic number (Z), and since the atomic numbers of S (Z = 16), Mo (Z = 42), W (Z = 74), Er (Z = 68), and Yb (Z = 70) elements are significantly different, different atoms can be clearly distinguished by the intensity difference, such as Figure 5 The atoms circled in the monolayer MoS2 region in (a) indicate that rare earth atoms are mainly doped in the form of atomic substitution, and their brightness is significantly stronger than that of other atoms. Figure 5 (b) In the selected area intensity profile, Er atoms and Yb atoms can be distinguished more clearly. Figure 5 The circled atoms in the heterojunction region shown in (c) are significantly brighter than other atoms. Figure 5 (d) In the selected area intensity profile, Er and Yb atoms show weaker intensities than W atoms.

[0059] The Raman spectrum test comparison pictures of the rare earth Er and Yb co-doped WS2 / MoS2 heterojunction prepared in this example and the undoped heterojunction are shown in the figure. Figure 6 As shown, the characteristic peaks of MoS2 are at 385cm -1 and 405cm -1 The characteristic peaks of the heterojunction are at 323 cm -1 、351cm -1 、385cm -1 、405cm -1 and 420cm -1 At the same time, there is a certain degree of deviation compared with the undoped heterojunction, indicating that the introduction of rare earths changes the lattice vibration of the heterojunction.

[0060] The fluorescence spectrum comparison pictures of the rare earth Er and Yb co-doped WS2 / MoS2 heterojunction prepared in this example and the undoped heterojunction are shown in the figure. Figure 7 As shown in the figure, under the same laser intensity, Er and Yb doped WS2 / MoS2 heterojunctions showed characteristic peaks at 631nm and 677nm, respectively, corresponding to the characteristic peaks of A exciton of WS2 and A exciton of MoS2, respectively. A characteristic peak at 677nm appeared in the single-layer MoS2 region. These three characteristic peaks showed a shift in peak position and a significant enhancement in intensity relative to the undoped heterojunction, indicating that the introduction of rare earths improved the luminescence performance of the heterojunction.

[0061] The scope of protection claimed by the present invention is not limited to the above specific embodiments. For those skilled in the art, the present invention may have various variations and modifications. Any modifications, improvements and equivalent substitutions made within the concept and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a rare earth-doped MX2 heterojunction, characterized in that: include: Step 1: Cleaning the silicon wafer substrate; Step 2: preparing a mixed solution using two M metal oxyacid salts, trivalent rare earth chloride and deionized water; Step 3: Ultrasonic dispersion of the mixed solution prepared in step 2 to achieve uniform dispersion of the elements; Step 4, weighing sodium cholate and adding it to the mixed solution after ultrasonication, stirring to obtain a precursor solution; Step 5: Place the cleaned silicon wafer substrate in the center of the spin coater, draw the precursor solution obtained in step 4, and drop it on the surface of the silicon wafer substrate for spin coating; Step 6: A tube furnace is used to perform a chemical vapor deposition reaction. A porcelain boat containing an X-ray source is placed in the low-temperature zone of the tube furnace's air inlet, and the silicon wafer substrate coated with the precursor solution is placed in the central temperature zone of the tube furnace. The carrier gas is introduced, and when the system is heated to the specified temperature, the X source is transported to the surface of the silicon wafer to react with the two M sources to achieve the preparation of rare earth doped heterojunction.

2. The method according to claim 1, wherein: In step 1, the silicon wafer substrate is cleaned with acetone, anhydrous ethanol, and deionized water in sequence.

3. The method according to claim 1 or 2, characterized in that: In step 2, the oxyacid salt of the M metal is selected from ammonium molybdate, ammonium tungstate or hydrates thereof.

4. The method according to claim 3, wherein: In step 2, the trivalent rare earth chloride is selected from ErCl3 or YbCl3.

5. The method according to claim 4, characterized in that: In step 2, two M metal oxyacid salts are prepared with deionized water to obtain solution A for growing a pure phase heterojunction; trivalent rare earth chloride is dissolved in deionized water to prepare solution B, and solution B is added to solution A to obtain a mixed solution.

6. The method according to claim 5, characterized in that: In step 2, trivalent rare earth chloride is dissolved in deionized water to prepare a solution with a concentration of 0.1 mg / mL.

7. The method according to claim 1 or 6, characterized in that: In step 3, the ultrasound duration is set to 30-50 minutes.

8. The method according to claim 7, wherein: In step six, the system temperature is raised from room temperature to 600°C within 20 minutes, then raised to 750°C within 16 minutes, and then kept at 750°C for 5 minutes before the program ends.

9. The method according to claim 1 or 8, characterized in that: In step six, the carrier gas is argon, and after argon purge for 3 to 10 minutes, the gas flow rate is maintained at 120 sccm.

10. A rare earth-doped MX2 heterojunction obtained by the method according to any one of claims 1 to 9.

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