A method for preparing aa-stacked double-layer transition metal chalcogenide thin films

Abstract

The application relates to a method for preparing AA-stacked double-layer transition metal chalcogenide films, which adopts a chemical vapor deposition method, regulates double-layer transition metal chalcogenide crystal domains to nucleate across steps on a substrate surface in a gas phase deposition process, and then grows into AA-stacked double-layer transition metal chalcogenide films. The application also relates to the AA-stacked double-layer transition metal chalcogenide films prepared by the method. The method can obtain full AA-stacked double-layer TMD films with excellent performance, and is beneficial to further obtaining double-layer single-crystal TMD.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of material preparation, and particularly relates to a method for preparing AA-stacked double-layer transition metal chalcogenide film. BACKGROUND

[0002] Transition metal chalcogenide (TMD) is a new two-dimensional material after graphene, and has more advantages and peculiar properties compared with graphene. At present, the preparation of single-layer TMD is relatively mature, but the preparation of double-layer or multi-layer TMD still has broad development space.

[0003] When the double-layer TMD is prepared by using the existing ordinary vapor deposition process, due to the thermodynamic properties of TMD, the energy of AA stacking and AB stacking formed in the growth process is roughly equal, and the system tends to change to the state with the lowest energy, so the probabilities of AA stacking and AB stacking of the upper and lower two layers of TMD are also roughly equal, so it is difficult to prepare double-layer TMD film with a single stacking mode. However, compared with double-layer TMD film with a non-single stacking mode, double-layer TMD film with a single stacking mode has more significant advantages in optical, electrical and other properties, and if the preparation of double-layer TMD film with a single stacking mode cannot be realized, double-layer single crystal cannot be further epitaxially grown. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a method for preparing AA-stacked double-layer transition metal chalcogenide film, which can obtain full AA-stacked double-layer TMD film with excellent performance, and is beneficial to further obtain double-layer single crystal TMD.

[0005] The technical scheme adopted by the present application is as follows:

[0006] The method for preparing AA-stacked double-layer transition metal chalcogenide film is characterized in that a chemical vapor deposition method is used to control the nucleation of the crystal domain of double-layer transition metal chalcogenide across the step on the surface of the substrate during the vapor deposition process, and then the double-layer transition metal chalcogenide film with AA stacking is grown.

[0007] The method of the present application breaks the symmetry of the substrate surface lattice by using the step on the surface of the substrate, controls the nucleation of the TMD crystal domain across the step during the vapor deposition process, so that the upper and lower two layers of TMD only have one energy minimum with the same growth direction, and therefore the orientations of the two layers of TMD are the same, forming AA stacking. The experimental results verify that the probability of AA stacking of the double-layer TMD crystal domain reaches more than 99% by using this method.

[0008] Compared with double-layer TMD film with a non-single stacking mode, the full AA-stacked double-layer TMD film prepared by the present application has more significant advantages in optical, electrical and other properties.

[0009] On the basis of the preparation of the full AA-stacked double-layer TMD nucleation achieved by the present application, through further epitaxial growth, the double-layer TMD crystal domains continue to grow and splice into a film, and a continuous AA-stacked double-layer film can be obtained.

[0010] More preferably, the method comprises the following steps:

[0011] S1. Place sulfur powder or selenium powder in a first temperature zone in a CVD tube furnace, and place a mixture of transition metal oxide and sodium chloride in a second temperature zone in the CVD tube furnace;

[0012] S2. In an inert atmosphere, heat the second temperature zone in the CVD tube furnace to 550-650℃ during 0 min to the 40th min, and heat the third temperature zone to 900℃, while heating the second temperature zone to 160℃ during the 20th min to the 40th min, and the first temperature zone, the second temperature zone and the third temperature zone are kept at a constant temperature from the 40th min;

[0013] S3. At the 40th min, place a sapphire substrate with atomically stepped surface distribution into the third temperature zone, and at the 50th min, take out the sapphire substrate from the third temperature zone, and after natural cooling to room temperature, obtain an AA-stacked double-layer transition metal chalcogenide film grown on the sapphire substrate.

[0014] The vapor deposition process of the method utilizes specific temperature conditions to achieve the regulation of the crystal domains to nucleate across the step at the step edge, and in particular, the sapphire substrate is placed into the third temperature zone for growth and deposition only in the last step S3, which small time window allows all the crystal domains to nucleate across the step edge, thereby improving the probability of forming AA stacking.

[0015] More preferably, the transition metal oxide is tungsten trioxide or molybdenum trioxide.

[0016] More preferably, the mass ratio of the sulfur powder or selenium powder, the transition metal oxide and the sodium chloride is 20-25:6:1.

[0017] More preferably, in steps S2 and S3, argon gas is continuously introduced into the CVD tube furnace, or argon gas and hydrogen gas are continuously introduced into the CVD tube furnace.

[0018] More preferably, in steps S2 and S3, argon gas and hydrogen gas with a volume ratio of 10:1 are continuously introduced into the CVD tube furnace.

[0019] More preferably, in step S1, the sapphire substrate is placed in a non-heating zone in the CVD tube furnace, and the non-heating zone is adjacent to the third temperature zone.

[0020] In step S3, at the 40th minute, the sapphire substrate is pushed from the non-heating zone to the third temperature zone, at the 50th minute, the sapphire substrate is pulled from the third temperature zone to the non-heating zone, and the heating power of the CVD tube furnace is turned off, so that the sapphire substrate is naturally cooled to room temperature with the furnace.

[0021] The application also provides the AA-stacked bilayer transition metal chalcogenide film prepared by the method.

[0022] For better understanding and implementation, the application is described in detail below with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 A schematic diagram of a tube furnace for preparing an AA-stacked bilayer transition metal chalcogenide film according to the method of the application.

[0024] Figure 2 A temperature curve diagram of three temperature zones in the furnace during vapor deposition according to the method of the application.

[0025] Figure 3A Grown domains when depositing a bilayer transition metal chalcogenide using a substrate without steps are shown, Figure 3B Grown domains when depositing a bilayer transition metal chalcogenide using a substrate with steps according to the method of the application are shown.

[0026] Figure 4 Raman spectrum of an AA-stacked bilayer tungsten disulfide film prepared in Example 1.

[0027] Figure 5 Optical microscope image of an AA-stacked bilayer tungsten disulfide film prepared in Example 1.

[0028] Figure 6 SHG image of an AA-stacked bilayer tungsten disulfide film prepared in Example 1.

[0029] Figure 7 Optical microscope image of a bilayer tungsten disulfide film prepared in Comparative Example 1.

[0030] Figure 8 SHG image of a bilayer tungsten disulfide film prepared in Comparative Example 1. DETAILED DESCRIPTION

[0031] The application provides a method for preparing an AA-stacked bilayer transition metal chalcogenide film, which adopts chemical vapor deposition to regulate the nucleation of the domains of the bilayer transition metal chalcogenide across steps on the surface of a substrate during vapor deposition, and then grow into an AA-stacked bilayer transition metal chalcogenide film.

[0032] Reference should be made to Figure 3Aand Figure 3B , Figure 3A It is shown that the substrate surface without steps in the process of vapor deposition grows double-layer TMD crystal domains with different orientations, Figure 3B It is shown that the substrate surface with steps in the process of vapor deposition grows double-layer TMD crystal domains with the same orientation and full AA stacking according to the method of the present application, the square area in the figure represents the substrate surface, the triangular area with overlapping range represents two layers of TMD crystal domains, the larger triangular area represents the lower layer of TMD crystal domains grown on the substrate surface, and the smaller triangular area represents the upper layer of TMD crystal domains grown on the lower layer of TMD crystal domains.

[0033] As Figure 3A shown, when the substrate surface has no steps, the lattices of the substrate and the TMD have symmetry by nature, and only when they form certain angles can they have the lowest energy, which is called the dominant orientation, and there are more than one dominant orientation. The same is true when one layer of TMD grows on another layer of TMD. Therefore, when growing double-layer TMD on a substrate surface without steps, the orientations of the upper and lower layers of TMD may be different. Specifically, the probabilities of forming AA stacking and AB stacking are equal, i.e. the lower layer of TMD and the upper layer of TMD have only half the chance of having the same orientation, and it is impossible to obtain double-layer TMD crystal domains with only one stacking mode.

[0034] As Figure 3B shown, when the substrate surface has steps, the steps can be used to break the inherent lattice symmetry of the substrate and the TMD, and the inventors have found that when each layer of TMD grows across the substrate steps, it is no longer the case that the energy in different directions is comparable as when there are no steps, but only one direction has the lowest energy, and this is true for both the upper and lower layers of TMD, so that double-layer TMD crystal domains with the same orientation of both layers can be obtained, specifically in the form of AA stacking. Through further epitaxial growth, the double-layer TMD crystal domains in the form of AA stacking continue to grow and join together into a film, and a continuous double-layer film in the form of AA stacking can be obtained.

[0035] Specifically, the method of the present application comprises the following steps:

[0036] S1. Placing sulfur powder or selenium powder in a first temperature zone in a CVD tube furnace, and placing a mixture of transition metal oxide and sodium chloride in a second temperature zone in the CVD tube furnace;

[0037] S2. In an inert atmosphere, heating the second temperature zone in the CVD tube furnace to 550-650℃ and the third temperature zone to 900℃ from 0min to the 40th min, and heating the second temperature zone to 160℃ from the 20th min to the 40th min, and maintaining the first temperature zone, the second temperature zone and the third temperature zone from the 40th min;

[0038] S3. At the 40th minute, the atomically stepped surface distributed sapphire substrate is put into the third temperature zone, and at the 50th minute, the sapphire substrate is taken out of the third temperature zone, and after naturally cooling to room temperature, an AA-stacked bilayer transition metal chalcogenide film grown on the sapphire substrate is obtained.

[0039] The above vapor deposition process utilizes specific temperature conditions to realize the regulation of the crystal domains to nucleate across the step edges, especially in the last step S3, the sapphire substrate is put into the third temperature zone for growth and deposition, which is a small time window that allows all crystal domains to nucleate across the step edges, thereby improving the probability of forming an AA-stacked bilayer.

[0040] Embodiment 1

[0041] This embodiment prepares an AA-stacked bilayer tungsten disulfide film, as shown in Figure 1 and Figure 2 A three-temperature-zone CVD tube furnace is used, which is sequentially provided with a first temperature zone, a second temperature zone and a third temperature zone, and the following steps are taken:

[0042] 1) Two porcelain boats are taken, each containing 500g of sulfur powder, and are placed in the first temperature zone. 120g of tungsten trioxide and 20g of sodium chloride are mixed and loaded into a porcelain boat, which is placed in the second temperature zone. A sapphire substrate with atomically stepped surface is placed on a push-pull device in the non-heated area for standby, as shown in Figure 1 .

[0043] The non-heated area is the area in the CVD tube furnace other than the first temperature zone, the second temperature zone and the third temperature zone, and is adjacent to the third temperature zone. The push-pull device includes a heat-resistant quartz plate and a magnetic push-pull mechanism. The quartz plate is used to carry the sapphire substrate, and the magnetic push-pull mechanism is driven by magnetic force to push or pull the quartz plate carrying the sapphire substrate into or out of the third temperature zone.

[0044] 2) Argon and hydrogen are continuously introduced into the CVD tube furnace, with argon flow rate set to 40sccm and hydrogen flow rate set to 4sccm.

[0045] 3) Turn on the heating power of the second temperature zone and the third temperature zone, and start heating. From 0min to the 40th minute, heat the second temperature zone to 650℃ and the third temperature zone to 900℃. At the 20th minute, turn on the heating power of the first temperature zone, and from the 20th minute to the 40th minute, heat the second temperature zone to 160℃. From the 40th minute, the first temperature zone, the second temperature zone and the third temperature zone are kept at 160℃, 650℃ and 900℃, respectively.

[0046] 4) using the push-pull device, at 40 min, push the sapphire substrate from the non-heating zone into the third temperature zone, at 50 min, pull the sapphire substrate from the third temperature zone to the non-heating zone, at the same time, turn off all the heating power of the CVD tube furnace and the hydrogen flow switch, stop the heating of the first temperature zone, the second temperature zone and the third temperature zone, and let the sapphire substrate cool down to room temperature with the furnace, and after taking out, obtain the AA-stacked bilayer molybdenum disulfide film grown on the surface of the sapphire substrate.

[0047] Example 2

[0048] In this embodiment, an AA-stacked bilayer molybdenum disulfide film is prepared, as shown in Figure 1 and Figure 2 A three-temperature-zone CVD tube furnace is used, which is sequentially provided with a first temperature zone, a second temperature zone and a third temperature zone, and the following steps are taken:

[0049] 1) Take two porcelain boats, each containing 500 g of sulfur powder, and place them in the first temperature zone. Mix 120 g of molybdenum trioxide and 20 g of sodium chloride, and load them into a porcelain boat, which is placed in the second temperature zone. Place a sapphire substrate with atomically stepped surface on the push-pull device in the non-heating zone for standby.

[0050] The non-heating zone is the area in the CVD tube furnace other than the first temperature zone, the second temperature zone and the third temperature zone, and is adjacent to the third temperature zone. The push-pull device includes a heat-resistant quartz plate and a magnetic push-pull mechanism. The quartz plate is used to carry the sapphire substrate, and the magnetic push-pull mechanism is driven by magnetic force to push or pull the quartz plate carrying the sapphire substrate into or out of the third temperature zone.

[0051] 2) continuously introduce argon into the CVD tube furnace, and adjust the argon flow to 40 sccm.

[0052] 3) Turn on the heating power of the second temperature zone and the third temperature zone, and start heating. From 0 min to 40 min, heat the second temperature zone to 550°C and the third temperature zone to 900°C. At 20 min, turn on the heating power of the first temperature zone. From 20 min to 40 min, heat the second temperature zone to 160°C. From 40 min, the first temperature zone, the second temperature zone and the third temperature zone are kept at 160°C, 550°C and 900°C, respectively.

[0053] 4) using the push-pull device, at 40 min, push the sapphire substrate from the non-heating zone into the third temperature zone, at 50 min, pull the sapphire substrate from the third temperature zone to the non-heating zone, at the same time, turn off all the heating power of the CVD tube furnace, stop the heating of the first temperature zone, the second temperature zone and the third temperature zone, and let the sapphire substrate cool down to room temperature naturally, after taking out, the AA-stacked bilayer molybdenum disulfide film grown on the surface of the sapphire substrate is obtained.

[0054] Example 3

[0055] In this embodiment, an AA-stacked bilayer molybdenum diselenide film is prepared, as shown in Figure 1 and Figure 2 A three-temperature-zone CVD tube furnace is used, the CVD tube furnace is sequentially provided with a first temperature zone, a second temperature zone and a third temperature zone, and the following steps are taken:

[0056] 1) Take two porcelain boats, each containing 400 g of selenium powder, and place them in the first temperature zone, mix 120 g of molybdenum trioxide and 20 g of sodium chloride, and load them into a porcelain boat, and place them in the second temperature zone, place the sapphire substrate with atomically stepped surface on the push-pull device in the non-heating zone for standby.

[0057] The non-heating zone is the area in the CVD tube furnace other than the first temperature zone, the second temperature zone and the third temperature zone, and is adjacent to the third temperature zone. The push-pull device includes a heat-resistant quartz plate and a magnet push-pull mechanism, the quartz plate is used to carry the sapphire substrate, and the magnet push-pull mechanism is driven by magnetic force and used to push or pull the quartz plate carrying the sapphire substrate into or out of the third temperature zone.

[0058] 2) continuously introduce argon and hydrogen into the CVD tube furnace, wherein the argon flow is adjusted to 40 sccm and the hydrogen flow is adjusted to 4 sccm.

[0059] 3) Turn on the heating power of the second temperature zone and the third temperature zone, and start heating, from 0 min to 40 min, heat the second temperature zone to 550℃, and heat the third temperature zone to 900℃; at 20 min, turn on the heating power of the first temperature zone, from 20 min to 40 min, heat the second temperature zone to 160℃; from 40 min, the first temperature zone, the second temperature zone and the third temperature zone are kept at 160℃, 550℃ and 900℃ respectively.

[0060] 4) using the push-pull device, at 40 min, push the sapphire substrate from the non-heating zone to the third temperature zone, at 50 min, pull the sapphire substrate from the third temperature zone to the non-heating zone, at the same time, turn off all the heating power of the CVD tube furnace and turn off the hydrogen flow switch, stop the heating of the first temperature zone, the second temperature zone and the third temperature zone, and let the sapphire substrate cool down to room temperature with the furnace, after taking out, the AA-stacked bilayer tungsten diselenide film grown on the surface of the sapphire substrate is obtained.

[0061] Comparative Example 1

[0062] In this comparative example, a bilayer tungsten disulfide film is prepared using a three-temperature-zone CVD tube furnace, which is sequentially provided with a first temperature zone, a second temperature zone and a third temperature zone, and the following steps are taken:

[0063] 1) 300 g of sulfur powder is divided into two porcelain boats and placed in the first temperature zone, 160 g of tungsten trioxide and 40 g of sodium chloride are mixed and loaded into a porcelain boat, which is placed in the second temperature zone, and an unannealed stepless sapphire substrate is placed in the third temperature zone.

[0064] 2) continuously introduce argon and hydrogen into the CVD tube furnace, wherein the argon flow is adjusted to 40 sccm and the hydrogen flow is adjusted to 4 sccm.

[0065] 3) turn on the heating power of the second temperature zone and the third temperature zone, start heating, from 0 min to 40 min, heat the second temperature zone to 650°C and the third temperature zone to 900°C; at 20 min, turn on the heating power of the first temperature zone, from 20 min to 40 min, heat the second temperature zone to 160°C; from 40 min, the first temperature zone, the second temperature zone and the third temperature zone are kept at 160°C, 650°C and 900°C respectively.

[0066] 4) at 50 min, turn off all the heating power of the CVD tube furnace and turn off the hydrogen flow switch, stop the heating of the first temperature zone, the second temperature zone and the third temperature zone, and let the sapphire substrate cool down to room temperature with the furnace, after taking out, the bilayer tungsten disulfide film grown on the surface of the sapphire substrate is obtained.

[0067] Comparative Example 2

[0068] In this comparative example, a bilayer molybdenum disulfide film is prepared using a three-temperature-zone CVD tube furnace, which is sequentially provided with a first temperature zone, a second temperature zone and a third temperature zone, and the following steps are taken:

[0069] 1) 400g of sulfur powder was divided into two porcelain boats and placed in the first temperature zone, 160g of molybdenum trioxide and 40g of sodium chloride were mixed and loaded into a porcelain boat and placed in the second temperature zone, and the unannealed step-free sapphire substrate was placed in the third temperature zone.

[0070] 2) Argon was continuously introduced into the CVD tube furnace, and the argon flow was adjusted to 40sccm.

[0071] 3) The heating power of the second and third temperature zones was turned on, and heating was started. From 0min to 40min, the second temperature zone was heated to 550°C, and the third temperature zone was heated to 900°C. At 20min, the heating power of the first temperature zone was turned on, and from 20min to 40min, the second temperature zone was heated to 160°C. From 40min, the first, second and third temperature zones were kept at 160°C, 550°C and 900°C, respectively.

[0072] 4) At 50min, all the heating powers of the CVD tube furnace were turned off, the hydrogen flow switch was turned off, and the heating of the first, second and third temperature zones was stopped. The sapphire substrate was naturally cooled to room temperature with the furnace, and after being taken out, a double-layer molybdenum disulfide film grown on the surface of the sapphire substrate was obtained.

[0073] Comparative Example 3

[0074] A double-layer molybdenum diselenide film was prepared in this comparative example, and a three-temperature-zone CVD tube furnace was used, which had a first temperature zone, a second temperature zone and a third temperature zone in sequence. The following steps were taken:

[0075] 1) 300g of selenium powder was divided into two porcelain boats and placed in the first temperature zone, 160g of molybdenum trioxide and 40g of sodium chloride were mixed and loaded into a porcelain boat and placed in the second temperature zone, and the unannealed step-free sapphire substrate was placed in the third temperature zone.

[0076] 2) Argon and hydrogen were continuously introduced into the CVD tube furnace, wherein the argon flow was adjusted to 40sccm, and the hydrogen flow was adjusted to 4sccm.

[0077] 3) The heating power of the second and third temperature zones was turned on, and heating was started. From 0min to 40min, the second temperature zone was heated to 550°C, and the third temperature zone was heated to 900°C. At 20min, the heating power of the first temperature zone was turned on, and from 20min to 40min, the second temperature zone was heated to 160°C. From 40min, the first, second and third temperature zones were kept at 160°C, 550°C and 900°C, respectively.

[0078] 4) At 50 min, turn off all heating power of the CVD tube furnace, turn off the hydrogen flow switch, stop heating of the first temperature zone, the second temperature zone and the third temperature zone, and let the sapphire substrate cool down to room temperature with the furnace, and after taking out, a double-layer molybdenum diselenide film grown on the surface of the sapphire substrate is obtained.

[0079] Experimental results:

[0080] See Figures 4-8 , Figure 4 the Raman spectrum of the AA-stacked double-layer tungsten disulfide film prepared in Example 1, Figure 5 the optical microscope image of the AA-stacked double-layer tungsten disulfide domain prepared in Example 1, Figure 6 the SHG image of the AA-stacked double-layer tungsten disulfide domain prepared in Example 1, Figure 7 the optical microscope image of the double-layer tungsten disulfide domain prepared in Comparative Example 1, Figure 8 the SHG image of the double-layer tungsten disulfide domain prepared in Comparative Example 1.

[0081] It can be seen from Figure 5 that the directions of the lower triangular domains and the upper triangular domains in the double-layer WS2 film obtained in Example 1 are the same, indicating that the preparation method of Example 1 can ensure the obtained double-layer film to be AA-stacked.

[0082] Comparative Example 1 adopts the same three-temperature zone temperature curve as Example 1 in the vapor deposition process, but uses a sapphire substrate without steps, and the sapphire substrate is placed in the third temperature zone in step 1).

[0083] Compared with Figure 5 , it can be seen from Figure 7 that the directions of the lower triangular domains and the upper triangular domains in the double-layer WO2 film obtained in Comparative Example 1 are the same in some cases and different in some cases, indicating that the preparation method of Comparative Example 1 cannot ensure the obtained double-layer film to be AA-stacked.

[0084] To determine whether the double-layer TMD film is AA-stacked or AB-stacked, a more accurate method is SHG test (second harmonic spectrum test), which is characterized by SHG image. If the directions of the upper and lower layers of TMD material are the same (AA-stacked), the generated SHG signals will superimpose on each other, and the intensity will be four times that of a single layer. If the directions are opposite (AB-stacked), the SHG signals will cancel each other out and the SHG signal will be zero.

[0085] After SHG test, as shown in Figure 6 , each triangular domain in the Figure 6 is bright, proving that the double-layer WO2 film obtained in Example 1 is fully AA-stacked. Similarly, the double-layer TMD films prepared in Examples 2 and 3 are also subjected to SHG test, and the results prove that they are all fully AA-stacked.

[0086] In comparison with Figure 6 In comparison with Figure 8 The middle of some domains in the figure is black triangle, which is the area of AB stacking. The surrounding circle of light is the single layer which is not covered, which proves that the double layer WO2 film obtained in the comparative example 1 exists AB stacking, but not full AA stacking. Similarly, the double layer TMD films obtained in the comparative examples 2 and 3 are also tested by SHG, and the results prove that AB stacking exists, but not full AA stacking.

[0087] The above embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as the limitation of the scope of the patent. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which belong to the protection scope of the present application.

Claims

1. A method for preparing an AA stacked double-layer transition metal chalcogenide thin film, characterized in that: Using chemical vapor deposition, the crystal domains of the double-layer transition metal chalcogenide are regulated to cross the steps on the substrate surface during the vapor deposition process to form nuclei, and then grow into an AA-stacked double-layer transition metal chalcogenide film. The method for preparing an AA stacked double-layer transition metal chalcogenide thin film comprises the following steps: S1. The sulfur powder or selenium powder is placed in the first temperature zone of the CVD tube furnace, and the mixture of the transition metal oxide and sodium chloride is placed in the second temperature zone of the CVD tube furnace; S2. In an inert atmosphere, from 0 min to 40 min, the second temperature zone in the CVD tube furnace is heated to 550-650 ° C, the third temperature zone is heated to 900 ° C, and from 20 min to 40 min, the second temperature zone is heated to 160 ° C, and from 40 min onwards, the first temperature zone, the second temperature zone and the third temperature zone are kept warm; S3. placing the sapphire substrate having atomic steps distributed on its surface into the third temperature zone at 40 minutes, removing the sapphire substrate from the third temperature zone at 50 minutes, and naturally cooling the substrate to room temperature to obtain an AA-stacked double-layer transition metal chalcogenide thin film grown on the sapphire substrate; Wherein, the transition metal oxide is tungsten trioxide or molybdenum trioxide; In step S1, the sapphire substrate is placed in a non-heating zone in the CVD tube furnace, where the non-heating zone is adjacent to the third temperature zone; In step S3, at the 40th minute, the sapphire substrate is pushed from the non-heating zone into the third temperature zone, and at the 50th minute, the sapphire substrate is pulled out from the third temperature zone to the non-heating zone, and the heating power of the CVD tube furnace is turned off to allow the sapphire substrate to cool naturally to room temperature with the furnace.

2. The method according to claim 1, characterized in that The mass ratio of the sulfur powder or selenium powder, transition metal oxide and sodium chloride is 20-25:6:

1.

3. The method according to claim 1, characterized in that In step S2 and step S3, argon gas is continuously introduced into the CVD tube furnace, or argon gas and hydrogen gas are continuously introduced into the CVD tube furnace.

4. The method according to claim 3, characterized in that In step S2 and step S3, argon and hydrogen are continuously introduced into the CVD tube furnace at a volume ratio of 10:

1.

5. An AA-stacked double-layer transition metal chalcogenide thin film prepared by the method according to any one of claims 1 to 4.

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