Exciton luminescence regulation and control method of transition metal chalcogenide

Abstract

The invention relates to an exciton luminescence regulation and control method of a transition metal chalcogenide. The method comprises the following steps: S1, obtaining a two-dimensional layered transition metal chalcogenide; s2, putting the two-dimensional layered transition metal chalcogenide into a sample boat, putting the sample boat into a tubular furnace, putting the tubular furnace into a second temperature zone, and putting S powder, Se powder or Te powder into the first temperature zone of the tubular furnace; s3, annealing treatment is conducted on the two-dimensional layered transition metal chalcogenide, the temperature of the second temperature zone in the tubular furnace is controlled to range from 100 DEG C to 350 DEG C, hydrogen-containing gas is introduced into the tubular furnace, the hydrogen flow ranges from 1 sccm to 8 sccm, and the annealing time ranges from 10 min to 60 min; and S4, keeping the ventilation state, cooling the tubular furnace, and taking out the sample boat to obtain a target product. The method can be used for adjusting the vacancy of the chalcogenide element of the two-dimensional layered transition metal chalcogenide material to obtain the material with high exciton luminescence quality.

Description

Technical Field

[0001] The present invention relates to the preparation technology of transition metal chalcogenides, in particular to a method for regulating exciton luminescence of transition metal chalcogenides. Background Art

[0002] Since graphene was successfully exfoliated in 2004, the research on two-dimensional materials has entered a rapid development stage, and now a huge family system including graphene, transition metal chalcogenides (TMDCs), hexagonal boron nitride, MXenes, black phosphorus, etc. has been formed. Due to their atomic-scale thickness, high specific surface area, tunable bandgap, excellent carrier mobility and other characteristics, these materials show revolutionary application potential in the fields of electronic devices, optoelectronic devices and flexible sensor devices.

[0003] TMDCs have a layered structure similar to that of graphene, and at the same time, they have attracted extensive attention from researchers in many fields due to their unique electrical, optical and mechanical properties. The exciton luminescence mechanism of TMDCs mainly stems from their unique band structure and strong exciton effect. For example, monolayer WS2 and MoS2 have direct bandgap characteristics, and the exciton binding energy is as high as 0.2 - 0.5 eV, enabling excitons to exist stably at room temperature. When photoexcited, electron-hole pairs form excitons and release photons through radiative recombination, showing high photoluminescence (PL) efficiency and intensity, and having broad application prospects especially in the field of optoelectronic devices.

[0004] Currently, the main method for large-scale preparation of two-dimensional layered transition metal chalcogenides is chemical vapor deposition (CVD). The two-dimensional layered transition metal chalcogenide materials prepared by the CVD method are usually n-type conductive, and their n-type conductivity is mainly attributed to the existence of a large number of S vacancies in the materials, including single S vacancies and multi-S vacancy clusters, etc. A single S vacancy in transition metal chalcogenides is considered a shallow donor impurity, which will form a shallow donor energy level and provide electrons, making the material n-type conductive. However, excessive S vacancies and their clusters are non-single S vacancies, which will reduce the quality of the transition metal chalcogenides prepared by the CVD method, deteriorate the optoelectronic properties, reduce the proportion of neutral excitons and negatively charged excitons in the PL spectrum, and weaken the photoluminescence intensity, which is not conducive to the preparation and application of subsequent exciton-based electronic and optoelectronic devices. Therefore, exploring how to regulate the type of sulfur vacancy defects in transition metal chalcogenides through a simple, effective and controllable process to obtain two-dimensional layered transition metal chalcogenide materials with more single S vacancies or fewer S vacancies is beneficial to improving their exciton luminescence quality and promoting the application of two-dimensional layered transition metal chalcogenide materials.

[0005] The invention patent application CN114058364A discloses a method for enhancing the luminescence intensity of transition metal sulfides, which relates to the field of two-dimensional materials. This method covers an organic thin film on the S vacancies of transition metal sulfides, thereby achieving the purpose of reducing S vacancies. In this method, the organic thin film may decompose or its performance may degrade in a high-temperature environment, affecting its covering effect and the function of enhancing luminescence intensity. Secondly, DMSO and other organic solvents are used in the spin-coating process of this solution, and these solvents are toxic or volatile, posing potential risks to the environment and the safety of operators. Thirdly, the organic thin film materials (such as F4TCNQ, thiols, etc.) mentioned in the patent are relatively expensive, especially for the treatment of large-area thin films, the material cost will increase significantly.

[0006] Therefore, it is of practical significance to explore how to obtain better two-dimensional layered transition metal chalcogenide materials with single S vacancies or fewer S vacancies. Summary of the Invention

[0007] The purpose of the present invention is to overcome the defects in the quality of existing two-dimensional layered transition metal chalcogenides, and provide a method for regulating the exciton luminescence of transition metal chalcogenides. This method is based on a low-temperature annealing process, and achieves the purpose of regulating exciton luminescence by controlling the types and morphologies of chalcogen element vacancies in transition metal chalcogenides, and the experimental repeatability and controllability are good.

[0008] In the method of the present invention, high-quality two-dimensional layered transition metal chalcogenide materials are prepared by CVD method, and further, by optimizing important process parameters such as annealing temperature, hydrogen flow rate, and annealing time, two-dimensional layered transition metal chalcogenide materials with controllable chalcogen element vacancies and excellent optoelectronic properties are obtained. The principle lies in building an environment for repairing chalcogen element vacancies, and controlling factors such as the distance between the chalcogen element powder in the first temperature zone and the sample in the second temperature zone, as well as the reaction temperature, hydrogen flow rate, and time, to achieve the structural adjustment and optimization of the material.

[0009] Finally, the present invention conducts photoluminescence spectroscopy tests on the samples before and after the low-temperature hydrogen annealing process, and confirms that the annealing process can achieve controllable adjustment of the types and morphologies of chalcogen element vacancies in two-dimensional layered transition metal chalcogenides, as well as the regulation of exciton luminescence of the material.

[0010] The specific scheme is as follows:

[0011] A method for regulating the exciton luminescence of transition metal chalcogenides, comprising the following steps:

[0012] S1. Obtain two-dimensional layered transition metal chalcogenides;

[0013] S2. Load the two-dimensional layered transition metal chalcogenide into a sample boat, place it in a tube furnace, put it into the second temperature zone, and place S powder, Se powder or Te powder in the first temperature zone of the tube furnace; define the end where the gas enters the tube furnace as the front end, then the first temperature zone is located at the front end of the second temperature zone and is 20 - 40 cm apart.

[0014] S3. Anneal the two-dimensional layered transition metal chalcogenide, control the temperature of the second temperature zone in the tube furnace to be 100 °C - 350 °C, introduce a hydrogen-containing gas into the tube furnace, the hydrogen flow rate is 1 sccm - 8 sccm, and the annealing time is 10 min - 60 min.

[0015] S4. Cool down the tube furnace while maintaining the gas supply state, take out the sample boat to obtain the target product.

[0016] Further, the two-dimensional layered transition metal chalcogenide in S1 is at least one of WS2, MoS2, ReS2, WSe2, MoSe2, ReSe2, WTe2, MoTe2.

[0017] Preferably, the two-dimensional layered transition metal chalcogenide is prepared by the CVD method, including: the substrate is a Si / SiO2 substrate, and the transition metal oxide source wafer is deposited on the Si / SiO2 substrate by thermal evaporation; cover the deposited transition metal oxide source wafer on the substrate Si / SiO2 substrate, and the interval between the source wafer and the substrate is 1 - 2 mm; then place sulfur powder in the low-temperature zone of the CVD tube furnace at a temperature of 200 - 300 °C, place the substrate and the source wafer in the high-temperature zone of the CVD tube furnace at a temperature of 900 - 1000 °C, use argon as the carrier gas during the growth process, the flow rate range is 60 - 200 sccm, and the growth time is 30 - 60 minutes.

[0018] Further, the sample boat in S2 is cleaned in advance, and the sample boat is ultrasonically cleaned with acetone, absolute ethanol, and ultrapure water and then purged with nitrogen until clean.

[0019] Further, for the S powder, Se powder or Te powder in S2, the powder purity is 99.999%, and an environment suitable for the repair of chalcogen element vacancies is built.

[0020] Further, the temperature of the second temperature zone in S3 is 120 °C - 320 °C, preferably 150 - 300 °C, more preferably 180 - 280 °C.

[0021] Further, direct heating is not performed in the first temperature zone, and the distance between the chalcogen element powder in the first temperature zone and the two-dimensional layered transition metal chalcogenide is controlled to be 30-40 cm. Within this distance range, the second temperature zone will indirectly obtain the heat transferred from the first temperature zone, so that the chalcogen element powder participates in the chemical reaction process.

[0022] Further, the hydrogen-containing gas in S3 is a mixed gas of an inert gas and hydrogen, and the inert gas is any one of helium, neon, argon, krypton, xenon, and radon.

[0023] Further, the flow rate of the inert gas is 50 sccm to 120 sccm, preferably 60 sccm to 100 sccm.

[0024] Further, the flow rate of the hydrogen in S3 is 2 sccm to 6 sccm, preferably 3 sccm to 5 sccm.

[0025] Further, the annealing time is 15 min to 45 min, preferably 20 to 30 min.

[0026] Beneficial effects: The present invention uses a low-temperature hydrogen annealing process to controllably adjust the chalcogen element vacancies of the prepared two-dimensional layered transition metal chalcogenide material, effectively improving the luminescence intensity of the prepared two-dimensional layered transition metal chalcogenide and regulating the exciton luminescence.

[0027] The present invention can effectively overcome the problems existing in the prior art, such as high-temperature decomposition and degradation of organic thin films, toxicity or volatility, and high cost.

[0028] At the same time, the low-temperature annealing process is based on the CVD growth environment, does not introduce foreign impurities, has good experimental repeatability and controllability, and has a large adjustable range of luminescence intensity.

[0029] In summary, the method provided by the present invention, based on the chalcogen element vacancy repair mechanism of the material, can more effectively obtain two-dimensional layered transition metal chalcogenides with high exciton luminescence quality, which are used for the development and research of next-generation optoelectronic devices. Description of the Drawings

[0030] In order to more clearly illustrate the technical solutions of the present invention, the drawings will be briefly introduced below. Obviously, the drawings in the following description only relate to some embodiments of the present invention and do not limit the present invention.

[0031] Figure 1(a) is a surface scan diagram of the integrated intensity of the PL spectrum of the unannealed monolayer WS2 provided in Example 1 of the present invention;

[0032] Figure 1(b) is the surface scan of the integrated intensity of the PL spectrum of single-layer WS2 after annealing provided by Example 1 of the present invention;

[0033] Figure 1(c) is the peak splitting diagram of the PL spectrum of single-layer WS2 without annealing provided by Example 1 of the present invention, where X - is the emission peak of negatively charged excitons and X D is the emission peak of defect excitons;

[0034] Figure 1(d) is the peak splitting diagram of the PL spectrum of single-layer WS2 after annealing provided by Example 1 of the present invention, where X - is the emission peak of negatively charged excitons and X D is the emission peak of defect excitons;

[0035] Figure 2(a) is the surface scan of the integrated intensity of the PL spectrum of single-layer WS2 without annealing provided by Example 2 of the present invention;

[0036] Figure 2(b) is the surface scan of the integrated intensity of the PL spectrum of single-layer WS2 after annealing provided by Example 2 of the present invention;

[0037] Figure 2(c) is the peak splitting diagram of the PL spectrum of single-layer WS2 without annealing provided by Example 2 of the present invention, where X - is the emission peak of negatively charged excitons and X D is the emission peak of defect excitons;

[0038] Figure 2(d) is the peak splitting diagram of the PL spectrum of single-layer WS2 after annealing provided by Example 2 of the present invention, where X - is the emission peak of negatively charged excitons and X D is the emission peak of defect excitons;

[0039] Figure 3(a) is the surface scan of the integrated intensity of the PL spectrum of single-layer WS2 without annealing provided by Example 3 of the present invention;

[0040] Figure 3(b) is the surface scan of the integrated intensity of the PL spectrum of single-layer WS2 after annealing provided by Example 3 of the present invention;

[0041] Figure 3(c) is the peak splitting diagram of the PL spectrum of single-layer WS2 without annealing provided by Example 3 of the present invention, where X - is the emission peak of negatively charged excitons and X D is the emission peak of defect excitons;

[0042] Figure 3(d) is the peak splitting diagram of the PL spectrum of single-layer WS2 after annealing provided by Example 3 of the present invention, where X - is the emission peak of negatively charged excitons and X D is the emission peak of defect excitons;

[0043] Figure 4(a) is a surface scan of the integrated intensity of the PL spectrum of as-deposited monolayer WS2 provided by Example 4 of the present invention;

[0044] Figure 4(b) is a surface scan of the integrated intensity of the PL spectrum of annealed monolayer WS2 provided by Example 4 of the present invention;

[0045] Figure 4(c) is a peak-resolved PL spectrum of as-deposited monolayer WS2 provided by Example 4 of the present invention, where X - is the emission peak of negatively charged excitons and X D is the emission peak of defect excitons;

[0046] Figure 4(d) is a peak-resolved PL spectrum of annealed monolayer WS2 provided by Example 4 of the present invention, where X - is the emission peak of negatively charged excitons and X D is the emission peak of defect excitons. Detailed Embodiments

[0047] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. For those techniques or conditions not specified in the examples, they shall be performed according to the techniques or conditions described in the literature in this field or according to the product specifications. For reagents or instruments whose manufacturers are not specified, they are all conventional products that can be obtained commercially. In the following examples, unless otherwise specified, "%" refers to weight percentage.

[0048] The following test methods are used:

[0049] Photoluminescence spectroscopy test:

[0050] Spectroscopy test equipment: Witec alpha 300R confocal micro-Raman spectrometer, laser wavelength 532 nm, tested in air at room temperature

[0051] Example 1

[0052] 1) Two-dimensional WS2 was prepared by CVD method. The specific preparation process includes: using a Si / SiO2 substrate; depositing tungsten trioxide source film on the Si / SiO2 substrate by thermal evaporation; covering the deposited tungsten trioxide source film on the substrate Si / SiO2 substrate, and the distance between the source film and the substrate is about 1 mm;

[0053] Placing the substrate film and the source film in the high-temperature zone of the CVD tube furnace. Placing 300 mg of high-purity sulfur powder in the low-temperature zone of the CVD tube furnace. Argon was used as the carrier gas during the growth process, and the flow rate range was 60-200 sccm.

[0054] The temperature in the low-temperature zone during growth is 220 °C, and the temperature in the high-temperature zone is 950 °C. The growth time is 40 minutes.

[0055] 2) Ultrasonically clean the substrate material, quartz boat, etc. with acetone, absolute ethanol, and ultrapure water for 10 min each, and blow them clean with nitrogen.

[0056] 3) Place the prepared WS2 sample in the quartz boat, place the quartz boat in the second temperature zone (high-temperature zone) of the CVD tube furnace, and place 50 mg of high-purity S powder in the first temperature zone (low-temperature zone). The distance between the sample and the high-purity S powder is 30 cm, and the first temperature zone is located at the front end of the second temperature zone.

[0057] 4) Close the CVD tube furnace, turn on the laboratory tail gas treatment device and the argon gas cylinder knob, set the temperature control program, the flow rate of the inert carrier gas (such as argon), and the hydrogen flow rate. The temperature of the low-temperature annealing process in the second temperature zone is 100 °C, the annealing time is 20 min, the flow rate of the inert carrier gas is 90 sccm, and the hydrogen flow rate is 3 sccm.

[0058] 5) Cool down the tube furnace while maintaining the ventilation state, take out the quartz boat to obtain the target product. Perform photoluminescence spectroscopy tests on the samples before and after annealing to obtain the exciton emission of the samples.

[0059] Results for reference Figure 1(a) to Figure 1(d) , as can be seen from Figure 1(a) and Figure 1(b), the spectral surface scan of the sample after annealing is brighter than that of the sample before annealing, indicating that the overall photoluminescence intensity of the sample after annealing has been improved. As can be seen from Figure 1(c) and Figure 1(d), the spectral intensity curves of the sample before and after annealing change greatly, and the intensity of the curve after annealing is higher. This is because during the low-temperature annealing process of hydrogen, hydrogen reacts with sulfur to form hydrogen sulfide, and hydrogen sulfide repairs the S vacancy defects in the prepared tungsten disulfide, reducing the S vacancy concentration, or changing the multi-S vacancy defect clusters in the prepared tungsten disulfide into single S vacancy defects. The reduction of the S vacancy concentration and the generation of single S vacancy defects effectively improve the crystal quality of tungsten disulfide, increase the electron concentration generated by single S vacancy defects, thereby enhancing the negative exciton emission and increasing the photoluminescence intensity.

[0060] It can be seen that the above method realizes the controllable regulation of the types and morphologies of chalcogen element vacancies in two-dimensional layered transition metal chalcogenides and the regulation of the exciton emission of the material based on the control of the annealing process.

[0061] Example 2

[0062] 1) Two-dimensional WS2 was prepared by the CVD method. The specific preparation process includes: using a Si / SiO2 substrate; evaporating tungsten trioxide source film onto the Si / SiO2 substrate by thermal evaporation; covering the evaporated tungsten trioxide source film on the substrate Si / SiO2, with a spacing of about 1 mm between the source film and the substrate;

[0063] Placing the substrate film and the source film in the high-temperature zone of the CVD tube furnace. Placing 300 mg of high-purity sulfur powder in the low-temperature zone of the CVD tube furnace. Argon was used as the carrier gas during the growth process, with a flow rate range of 60 - 200 sccm.

[0064] The temperature in the low-temperature zone during growth was 220 °C, and the temperature in the high-temperature zone was 950 °C. The growth time was 40 minutes. 2) The substrate material, quartz boat, etc. were ultrasonically cleaned with acetone, absolute ethanol, and ultrapure water for 10 min each, and blown clean with nitrogen.

[0065] 3) The prepared WS2 sample was placed in a quartz boat, and the quartz boat was placed in the second temperature zone (high-temperature zone) of the CVD tube furnace. 50 mg of high-purity S powder was placed in the first temperature zone (low-temperature zone). The distance between the sample and the high-purity S powder was 30 cm, and the first temperature zone was at the front of the second temperature zone.

[0066] 4) Close the CVD tube furnace, turn on the laboratory tail gas treatment device and the argon gas cylinder knob, set the temperature control program, the flow rate of the inert carrier gas (such as argon), and the hydrogen flow rate. The temperature of the low-temperature annealing process in the second temperature zone was 200 °C, the annealing time was 20 min, the inert carrier gas flow rate was 90 sccm, and the hydrogen flow rate was 3 sccm.

[0067] 5) Keep the ventilation state and cool down the tube furnace, take out the quartz boat to obtain the target product. The photoluminescence spectra of the samples before and after annealing were tested respectively to obtain the exciton emission of the samples.

[0068] The results are shown in Figure 2(a) to Figure 2(d) , as can be seen from Fig. 2(a) and Fig. 2(b), the spectral surface scan of the sample after annealing is brighter than that of the sample before annealing, indicating that the overall photoluminescence intensity of the sample after annealing has been improved. As can be seen from Fig. 2(c) and Fig. 2(d), the spectral intensity curves of the sample before and after annealing have changed greatly, and the intensity of the curve after annealing is higher. This is because during the low-temperature annealing process of hydrogen, hydrogen reacts with sulfur to form hydrogen sulfide, and hydrogen sulfide repairs the S vacancy defects in the prepared tungsten disulfide, reduces the S vacancy concentration, or changes the multi-S vacancy defect clusters in the prepared tungsten disulfide into single S vacancy defects. The reduction of the S vacancy concentration and the generation of single S vacancy defects effectively improve the crystal quality of tungsten disulfide, increase the electron concentration generated by single S vacancy defects, thereby enhancing the negative exciton emission and improving the photoluminescence intensity.

[0069] It can be seen that the above method realizes the controllable regulation of the types and morphologies of chalcogen vacancies in two-dimensional layered transition metal chalcogenides and the regulation of the exciton luminescence of the material based on annealing process control.

[0070] Example 3

[0071] 1) Two-dimensional WS2 was prepared by CVD method. The specific preparation process includes: using a Si / SiO2 substrate; tungsten trioxide source wafers were deposited on the Si / SiO2 substrate by thermal evaporation; the deposited tungsten trioxide source wafers were covered on the substrate Si / SiO2, and the interval between the source wafer and the substrate was about 1 mm;

[0072] The substrate wafer and the source wafer were placed in the high-temperature zone of the CVD tube furnace. 300 mg of high-purity sulfur powder was placed in the low-temperature zone of the CVD tube furnace. Argon was used as the carrier gas during the growth process, and the flow rate range was 60 - 200 sccm.

[0073] During growth, the temperature in the low-temperature zone was 220 °C, and the temperature in the high-temperature zone was 950 °C. The growth time was 40 minutes.

[0074] 2) The substrate material, quartz boat, etc. were ultrasonically cleaned with acetone, absolute ethanol, and ultrapure water for 10 minutes each, and then blown clean with nitrogen.

[0075] 3) The prepared WS2 sample was placed in a quartz boat, and the quartz boat was placed in the second temperature zone (high-temperature zone) of the CVD tube furnace. 50 mg of high-purity S powder was placed in the first temperature zone (low-temperature zone). The distance between the sample and the high-purity S powder was 30 cm, and the first temperature zone was located at the front end of the second temperature zone.

[0076] 4) Close the CVD tube furnace, turn on the laboratory tail gas treatment device and the argon gas cylinder knob, set the temperature control program, the flow rate of the inert carrier gas (such as argon), and the hydrogen flow rate. The temperature of the low-temperature annealing process in the second temperature zone was 200 °C, the annealing time was 20 minutes, the inert carrier gas flow rate was 90 sccm, and the hydrogen flow rate was 5 sccm.

[0077] 5) Keep the ventilation state and cool down the tube furnace, take out the quartz boat to obtain the target product. Photoluminescence spectroscopy tests were performed on the samples before and after annealing to obtain the exciton luminescence of the samples.

[0078] The results are shown in Figure 3(a) to Figure 3(d), As can be seen from Figures 3(a) and 3(b), the spectral surface scan of the annealed sample is brighter than that of the sample before annealing, indicating that the overall photoluminescence intensity of the annealed sample has been improved. As can be seen from Figures 3(c) and 3(d), the spectral intensity curves of the sample before and after annealing change greatly, and the intensity of the curve after annealing is higher. This is because during the low-temperature annealing process of hydrogen, hydrogen reacts with sulfur to form hydrogen sulfide, and hydrogen sulfide repairs the S vacancy defects in the prepared tungsten disulfide, reducing the S vacancy concentration, or changing the multi-S vacancy defect clusters in the prepared tungsten disulfide into single S vacancy defects. The reduction of the S vacancy concentration and the generation of single S vacancy defects effectively improve the crystal quality of tungsten disulfide, increase the electron concentration generated by single S vacancy defects, thereby enhancing the negative exciton luminescence and improving the photoluminescence intensity.

[0079] It can be seen that the above method realizes the controllable regulation of the types and morphologies of chalcogen element vacancies in two-dimensional layered transition metal chalcogenides and the regulation of exciton luminescence of materials based on the control of the annealing process.

[0080] Example 4

[0081] 1) Two-dimensional WS2 was prepared by CVD method. The specific preparation process includes: using a Si / SiO2 substrate; the tungsten trioxide source wafer was deposited on the Si / SiO2 substrate by thermal evaporation; the deposited tungsten trioxide source wafer was covered on the substrate Si / SiO2 substrate, and the interval between the source wafer and the substrate was about 1 mm;

[0082] The substrate wafer and the source wafer were placed in the high-temperature zone of the CVD tube furnace. 300 mg of high-purity sulfur powder was placed in the low-temperature zone of the CVD tube furnace. Argon was used as the carrier gas during the growth process, and the flow rate range was 60-200 sccm.

[0083] The temperature of the low-temperature zone during growth was 220 °C, and the temperature of the high-temperature zone was 950 °C. The growth time was 40 minutes. 2) The substrate material, quartz boat, etc. were ultrasonically cleaned with acetone, absolute ethanol, and ultrapure water for 10 min each, and purged with nitrogen until clean.

[0084] 3) The prepared WS2 sample was placed in a quartz boat, and the quartz boat was placed in the second temperature zone (high-temperature zone) of the CVD tube furnace, and 50 mg of high-purity S powder was placed in the first temperature zone (low-temperature zone). The distance between the sample and the high-purity S powder was 30 cm, and the first temperature zone was located at the front end of the second temperature zone.

[0085] 4) Close the CVD tube furnace, turn on the laboratory tail gas treatment device and the argon gas cylinder knob, set the temperature control program, the flow rate of the inert carrier gas (such as argon), and the hydrogen flow rate. The temperature of the low-temperature annealing process in the second temperature zone was 200 °C, the annealing time was 30 min, the flow rate of the inert carrier gas was 90 sccm, and the hydrogen flow rate was 3 sccm.

[0086] 5) Keep the tubular furnace in a ventilated state to cool down, take out the quartz boat, and obtain the target product. Photoluminescence spectroscopy tests were carried out on the samples before and after annealing to obtain the exciton luminescence of the samples.

[0087] The results are shown in Figure 4(a) to Figure 4(d) , as can be seen from Figures 4(a) and 4(b), the spectral surface scan of the annealed sample is brighter than that of the sample before annealing, indicating that the overall photoluminescence intensity of the annealed sample has been improved. As can be seen from Figures 4(c) and 4(d), the spectral intensity curves of the sample before and after annealing change greatly, and the intensity of the curve after annealing is higher. This is because during the low-temperature annealing process of hydrogen, hydrogen reacts with sulfur to form hydrogen sulfide, and hydrogen sulfide repairs the S vacancy defects in the prepared tungsten disulfide, reduces the S vacancy concentration, or changes the multi-S vacancy defect clusters in the prepared tungsten disulfide to single S vacancy defects. The reduction of the S vacancy concentration and the generation of single S vacancy defects effectively improve the crystal quality of tungsten disulfide, increase the electron concentration generated by single S vacancy defects, thereby enhancing the negative exciton luminescence and increasing the photoluminescence intensity.

[0088] It can be seen that the above method realizes the controllable regulation of the types and morphologies of chalcogen element vacancies in two-dimensional layered transition metal chalcogenides and the regulation of the exciton luminescence of materials based on the control of the annealing process.

[0089] Example 5

[0090] 1) Prepare two-dimensional MoS2 by CVD method. The specific preparation process includes: using a Si / SiO2 substrate; depositing molybdenum trioxide source wafers on the Si / SiO2 substrate by thermal evaporation; covering the deposited molybdenum trioxide source wafers on the substrate Si / SiO2 substrate, and the interval between the source wafer and the substrate is about 1 mm;

[0091] Place the substrate wafer and the source wafer in the high-temperature zone of the CVD tubular furnace. Place 300 mg of high-purity sulfur powder in the low-temperature zone of the CVD tubular furnace. Argon is used as the carrier gas during the growth process, and the flow rate range is 60 - 200 sccm.

[0092] The temperature in the low-temperature zone during growth is 220 °C, and the temperature in the high-temperature zone is 750 °C. The growth time is 40 minutes. 2) Use acetone, absolute ethanol, and ultrapure water to ultrasonically clean the substrate material, quartz boat, etc. for 10 min each, and blow dry with nitrogen.

[0093] 3) Put the prepared MoS2 sample into the quartz boat, place the quartz boat in the second temperature zone (high-temperature zone) of the CVD tubular furnace, and put 50 mg of high-purity S powder in the first temperature zone (low-temperature zone). The distance between the sample and the high-purity S powder is 30 cm, and the first temperature zone is located at the front end of the second temperature zone.

[0094] 4) Close the CVD tube furnace, turn on the laboratory tail gas treatment device and the argon gas cylinder knob, set the temperature control program, the flow rate of the inert carrier gas (such as argon), and the hydrogen gas flow rate. The temperature of the low-temperature annealing process in the second temperature zone is 200 °C, the annealing time is 20 min, the inert carrier gas flow rate is 90 sccm, and the hydrogen gas flow rate is 8 sccm.

[0095] 5) Keep the gas flowing and cool down the tube furnace, then take out the quartz boat to obtain the target product.

[0096] Through the above method, the spectral surface scan of the annealed sample is brighter than that of the sample before annealing, indicating that the overall photoluminescence intensity of the annealed sample has been improved. Moreover, the spectral intensity curves of the sample before and after annealing have changed significantly, and the intensity of the curve after annealing is higher, realizing the controllable regulation of the types and morphologies of chalcogen vacancies in two-dimensional layered transition metal chalcogenides, as well as the regulation of the exciton luminescence of the material.

[0097] Example 6

[0098] 1) Prepare two-dimensional MoS2 by CVD method. The specific preparation process includes: using a Si / SiO2 substrate; depositing molybdenum trioxide source film on the Si / SiO2 substrate by thermal evaporation; covering the deposited molybdenum trioxide source film on the substrate Si / SiO2 substrate, and the interval between the source film and the substrate is about 1 mm;

[0099] Place the substrate film and the source film in the high-temperature zone of the CVD tube furnace. Place 300 mg of high-purity sulfur powder in the low-temperature zone of the CVD tube furnace. Argon is used as the carrier gas during the growth process, and the flow rate range is 60-200 sccm.

[0100] The temperature of the low-temperature zone during growth is 220 °C, and the temperature of the high-temperature zone is 750 °C. The growth time is 40 minutes. 2) Ultrasonically clean the substrate material, quartz boat, etc. with acetone, absolute ethanol, and ultrapure water for 10 min each, and blow dry with nitrogen.

[0101] 3) Put the prepared MoS2 sample into the quartz boat, place the quartz boat in the second temperature zone (high-temperature zone) of the CVD tube furnace, and put 50 mg of high-purity S powder in the first temperature zone (low-temperature zone). The distance between the sample and the high-purity S powder is 30 cm, and the first temperature zone is at the front end of the second temperature zone.

[0102] 4) Close the CVD tube furnace, turn on the laboratory tail gas treatment device and the argon gas cylinder knob, set the temperature control program, the flow rate of the inert carrier gas (such as argon), and the hydrogen gas flow rate. The temperature of the low-temperature annealing process in the second temperature zone is 250 °C, the annealing time is 30 min, the inert carrier gas flow rate is 80 sccm, and the hydrogen gas flow rate is 1 sccm.

[0103] 5) Keep the ventilation state and cool down the tube furnace, take out the quartz boat, and obtain the target product.

[0104] Through the above method, the spectral plane scan of the annealed sample is brighter than that of the sample before annealing, indicating that the overall photoluminescence intensity of the annealed sample has been improved, and there are significant changes in the spectral intensity curves of the sample before and after annealing, with the intensity of the curve after annealing being higher, realizing the controllable regulation of the types and morphologies of chalcogen vacancies in two-dimensional layered transition metal chalcogenides, as well as the regulation of the exciton luminescence of the material.

[0105] Comparative Example 1

[0106] 1) Prepare two-dimensional WS2 by CVD method. The specific preparation process includes: using a Si / SiO2 substrate; depositing tungsten trioxide source film on the Si / SiO2 substrate by thermal evaporation; covering the deposited tungsten trioxide source film on the substrate Si / SiO2 substrate, with a spacing of about 1 mm between the source film and the substrate;

[0107] Place the substrate film and the source film in the high-temperature zone of the CVD tube furnace. Place 300 mg of high-purity sulfur powder in the low-temperature zone of the CVD tube furnace. Argon is used as the carrier gas during the growth process, and the flow rate range is 60 - 200 sccm.

[0108] The temperature in the low-temperature zone during growth is 220 °C, and the temperature in the high-temperature zone is 950 °C. The growth time is 40 minutes. 2) Ultrasonically clean the substrate material, quartz boat, etc. with acetone, absolute ethanol, and ultrapure water for 10 min each, and blow dry with nitrogen.

[0109] 3) Put the prepared WS2 sample into the quartz boat, place the quartz boat in the second temperature zone (high-temperature zone) of the CVD tube furnace, and place 50 mg of high-purity S powder in the first temperature zone (low-temperature zone), with a distance of 30 cm between the sample and the high-purity S powder. The first temperature zone is located at the front end of the second temperature zone.

[0110] 4) Close the CVD tube furnace, turn on the laboratory tail gas treatment device and the argon gas cylinder knob, set the temperature control program, the flow rate of the inert carrier gas (such as argon), and the hydrogen flow rate. The temperature of the low-temperature annealing process in the second temperature zone is 200 °C, the annealing time is 20 min, the flow rate of the inert carrier gas is 90 sccm, and the hydrogen flow rate is 15 sccm.

[0111] 5) Keep the ventilation state and cool down the tube furnace, take out the quartz boat, and obtain the target product. Perform photoluminescence spectroscopy tests on the samples before and after annealing to obtain the exciton luminescence of the samples.

[0112] Based on the control of the annealing process in this comparative example, it was found that excessive hydrogen had an obvious corrosive effect on the WS2 film, the quality of the sample was significantly deteriorated, and the photoluminescence intensity decreased.

[0113] Comparative Example 2

[0114] 1) Two-dimensional WS2 was prepared by CVD method. The specific preparation process included: using a Si / SiO2 substrate; depositing a tungsten trioxide source film on the Si / SiO2 substrate by thermal evaporation; covering the deposited tungsten trioxide source film on the Si / SiO2 substrate, with a spacing of about 1 mm between the source film and the substrate;

[0115] Placing the substrate film and the source film in the high-temperature zone of the CVD tube furnace. Placing 300 mg of high-purity sulfur powder in the low-temperature zone of the CVD tube furnace. Argon was used as the carrier gas during the growth process, and the flow rate range was 60 - 200 sccm.

[0116] The temperature in the low-temperature zone during growth was 220 °C, and the temperature in the high-temperature zone was 950 °C. The growth time was 40 minutes.

[0117] 2) The substrate material, quartz boat, etc. were ultrasonically cleaned with acetone, absolute ethanol, and ultrapure water for 10 min each, and then purged with nitrogen until clean.

[0118] 3) The prepared WS2 sample was placed in a quartz boat, and the quartz boat was placed in the second temperature zone (high-temperature zone) of the CVD tube furnace. 50 mg of high-purity S powder was placed in the first temperature zone (low-temperature zone). The distance between the sample and the high-purity S powder was 30 cm, and the first temperature zone was at the front of the second temperature zone.

[0119] 4) Close the CVD tube furnace, turn on the laboratory tail gas treatment device and the argon gas cylinder knob, set the temperature control program and the flow rate of the inert carrier gas (such as argon). The temperature of the low-temperature annealing process in the second temperature zone was 200 °C, the annealing time was 20 min, the flow rate of the inert carrier gas was 90 sccm, and the flow rate of hydrogen was 0.5 sccm.

[0120] 5) Keep the ventilation state and cool down the tube furnace, take out the quartz boat to obtain the target product. Photoluminescence spectroscopy tests were performed on the samples before and after annealing to obtain the exciton emission of the samples.

[0121] Based on the annealing process control of this comparative example, it was found that the hydrogen flow rate was too low, and the change in the spectral intensity curve of the sample before and after annealing was not significant, and the sample quality was similar, indicating that there was no obvious adjustment effect on the WS2 film at this time.

[0122] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0123] In addition, it should be noted that, among the various specific technical features described in the above specific embodiments, they can be combined in any suitable manner without conflict. To avoid unnecessary repetition, the present invention will not separately describe various possible combination manners.

[0124] In addition, any combination can also be made among various different embodiments of the present invention, as long as it does not violate the idea of the present invention, and it should also be regarded as the content disclosed by the present invention.

Claims

1. A method for regulating exciton luminescence of transition metal chalcogenides, characterized in that: It includes the following steps: S1. Obtain a two-dimensional layered transition metal chalcogenide; S2. Load the two-dimensional layered transition metal chalcogenide into a sample boat, place it in a tube furnace, put it into the second temperature zone, and put S powder, Se powder or Te powder in the first temperature zone of the tube furnace; define the end where the gas enters the tube furnace as the front end, then the first temperature zone is located at the front end of the second temperature zone and is 20 - 40 cm apart; S3. Anneal the two-dimensional layered transition metal chalcogenide, control the temperature of the second temperature zone in the tube furnace to be 100°C - 350°C, introduce a gas containing hydrogen into the tube furnace, the hydrogen flow rate is 1 sccm - 8 sccm, and the annealing time is 10 min - 60 min; S4. Keep the ventilation state and cool down the tube furnace, take out the sample boat to obtain the target product.

2. The method for regulating exciton luminescence of the transition metal chalcogenide according to claim 1, wherein: The two-dimensional layered transition metal chalcogenide in S1 is at least one of WS2, MoS2, ReS2, WSe2, MoSe2, ReSe2, WTe2, MoTe2; Preferably, the two-dimensional layered transition metal chalcogenide is prepared by the CVD method, including: the substrate is a Si / SiO2 substrate, and the transition metal oxide source wafer is evaporated on the Si / SiO2 substrate by thermal evaporation; cover the evaporated transition metal oxide source wafer on the substrate Si / SiO2 substrate, and the distance between the source wafer and the substrate is 1 - 2 mm; then place the chalcogen element powder in the low-temperature zone of the CVD tube furnace with a temperature of 200 - 300°C, place the substrate and the source wafer in the high-temperature zone of the CVD tube furnace with a temperature of 900 - 1000°C, and use argon as the carrier gas during the growth process, with a flow rate range of 60 - 200 sccm and a growth time of 30 - 60 minutes.

3. The method for regulating the exciton luminescence of the transition metal chalcogenide according to claim 1, characterized in that: The sample boat in S2 is cleaned in advance, and the sample boat is ultrasonically cleaned with acetone, absolute ethanol, and ultrapure water, and blown clean with nitrogen.

4. The method for regulating exciton luminescence of the transition metal chalcogenide according to any one of claims 1-3, characterized in that: In S2, the S powder, Se powder or Te powder, and the powder purity is 99.999 wt%.

5. The method for regulating the exciton luminescence of the transition metal chalcogenide according to claim 4, characterized in that: In S3, the temperature of the second temperature zone is 120°C - 320°C, preferably 150 - 300°C, more preferably 180 - 280°C.

6. The method for regulating exciton luminescence of the transition metal chalcogenide according to claim 5, wherein: The first temperature zone is not directly heated, and the distance between the chalcogen element powder in the first temperature zone and the two-dimensional layered transition metal chalcogenide is controlled to be 30 - 40 cm.

7. The method for regulating the exciton luminescence of the transition metal chalcogenide according to claim 5, characterized in that: In S3, the gas containing hydrogen is a mixed gas of an inert gas and hydrogen, and the inert gas is any one of helium, neon, argon, krypton, xenon, and radon.

8. The method for regulating exciton luminescence of the transition metal chalcogenide according to claim 7, wherein: The flow rate of the inert gas is 50 sccm - 120 sccm, preferably 60 sccm - 100 sccm.

9. The method for regulating the exciton luminescence of the transition metal chalcogenide according to claim 7, wherein: In S3, the flow rate of the hydrogen is 2 sccm - 6 sccm, preferably 3 sccm - 5 sccm.

10. The method for regulating exciton luminescence of the transition metal chalcogenide according to any one of claims 1-3, characterized in that: The annealing time is 15 min - 45 min, preferably 20 - 30 min.

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