Single-layer mixed-phase molybdenum telluride selenide material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of low-dimensional semiconductors, and discloses a single-layer mixed-phase molybdenum telluride selenide material and a preparation method thereof, and the preparation method comprises the following specific steps: step 1, wiping a three-temperature-zone tubular furnace and a quartz sleeve by using absolute ethyl alcohol until the surfaces are free of visible stains and impurities, and ensuring cleanliness; the invention provides a single-layer mixed-phase molybdenum telluride selenide MoSe2 (1-x) Te2x material which is a MoSe2 (1-x) Te2x planar homojunction formed by mixing and embedding a 2H phase and a 1T'phase, the thickness is about 0.7 nm, the crystal phase proportion and the band gap can be flexibly regulated and controlled according to the tellurium / selenium proportion, and the single-layer mixed-phase molybdenum telluride selenide MoSe2 (1-x) Te2x material can meet the application requirements of nano electronic and optoelectronic devices. Secondly, the invention provides a preparation method of the single-layer mixed-phase tellurium selenide molybdenum material, the method is a one-step molten salt assisted chemical vapor deposition method, the single-layer mixed-phase tellurium selenide molybdenum material prepared by the method is high in crystal quality and obvious in phase mixing characteristic, and the method has the characteristics of simple operation, mild reaction and high repeatability.

Description

Technical Field

[0001] This invention belongs to the field of low-dimensional semiconductor technology, specifically a single-layer mixed-phase molybdenum telluride material, its preparation method, and its application. Background Technology

[0002] Two-dimensional transition metal dichalcogenides (TMDs), represented by molybdenum disulfide (MoS2), molybdenum diselenide (MoSe2), and molybdenum ditelluride (MoTe2), have shown broad application prospects in the fields of nanoelectronics and optoelectronic devices due to their ultrathin atomic structure, excellent photoelectric properties, and rich phase structures. Modulating the band structure of two-dimensional TMD materials by alloying elements is one of the effective methods to improve their photoelectric properties and enhance their device functionality. However, previous studies have mostly focused on the alloying element modulation of a single semiconductor phase, which has limited the scope and types of band modulation.

[0003] Two-dimensional molybdenum telluride (TMD) materials possess a rich variety of phase structures, including the semiconductor-like 2H and 3R phases, and the semi-metallic 1T, 1T', and 1Td phases. Monolayer 2H-phase TMD materials exhibit a direct bandgap, with the corresponding electromagnetic wavelength typically in the visible light range. Meanwhile, the semi-metallic 1T'-phase TMD materials display near-zero bandgap band characteristics, resulting in higher carrier mobility and conductivity. However, the fabricated optoelectronic devices exhibit high dark current. Therefore, combining the advantages of both phases to form a hybrid-phase TMD material would not only extend the spectral response range of the device but also improve the photocurrent while simultaneously reducing dark current. Monolayer molybdenum telluride selenide (MoSe) materials are a suitable candidate for this purpose. 2(1-x) Te 2x For example, its band gap can be adjusted between 1.5 eV (the band gap of a monolayer 2H phase MoSe2) and 0 eV (the band gap of a monolayer 1T' phase MoTe2) with the change of tellurium and selenium composition ratio. To achieve monolayer mixed-phase molybdenum telluride selenide (MoSe2), 2(1-x) Te 2x For applications in optoelectronic devices, the preparation of high-quality monolayer mixed-phase molybdenum telluride (TMD) materials with tunable selenium / tellurium composition is a crucial prerequisite. Chemical vapor deposition (CVD) is currently one of the most promising methods for preparing large-area, high-quality monolayer TMD materials. However, previous studies based on conventional CVD methods have limited the ability to prepare single-phase MoSe2, MoTe2, and MoSe. 2(1-x) Te 2x Materials, for MoSe composed of 2H and 1T' phases 2(1-x) Te 2x No studies on the growth of alloy monolayers have been reported; therefore, the development of a monolayer mixed phase MoSe with tunable composition is a key objective. 2(1-x) Te 2xThe CVD preparation method of alloy materials is of great significance for their application in high-performance optoelectronic devices. Summary of the Invention

[0004] The purpose of this invention is to provide a single-layer mixed-phase molybdenum telluride material, its preparation method, and its application, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a single-layer mixed-phase molybdenum telluride material and its preparation method, the specific steps of which are as follows:

[0006] Step 1:

[0007] The three-zone tubular furnace and quartz sleeve were wiped with anhydrous ethanol until no visible stains or impurities were visible on the surface, ensuring cleanliness. After wiping the surfaces of the tubular furnace and quartz sleeve, the quartz sleeve was installed at the furnace interface, the furnace door was closed, and the sealing bolts were tightened. The tubular furnace system was then tested for leak resistance using a helium mass spectrometer, requiring a system leak rate ≤ 5 × 10⁻⁶. -9 Pa·m 3 / s, if a leak is detected, the interface needs to be disassembled and the fluororubber gasket that can withstand temperatures above 300℃ replaced. After reassembly, the leak is checked again until the sealing requirements are met. Then, the tubular furnace is annealed at 600℃~700℃. During the annealing process, a 500sccm hydrogen-argon mixture is passed through to flush the furnace more than twice to ensure that the reaction environment is pure and free from pollution.

[0008] Step Two:

[0009] A 1cm×1cm silicon-based (SiO2 / Si) substrate was selected and cleaned sequentially with acetone, ethanol and deionized water, and then dried with nitrogen to remove impurities from the substrate surface before use.

[0010] Step 3:

[0011] Weigh appropriate amounts of molybdenum dioxide (MoO2), sodium bromide (NaBr), and sodium chloride (NaCl) solid powders, place them in a grinding mortar, and grind them thoroughly under inert gas protection until they are mixed evenly. Then place the mixture in a quartz boat as a reaction precursor.

[0012] Step Four:

[0013] Weigh appropriate amounts of selenium powder and tellurium granules, and place them in two quartz boats inside a quartz sleeve: place the quartz boat containing the selenium powder in the first temperature zone, and place the quartz boat containing the tellurium granules between the first and second temperature zones; place the quartz boat containing the above mixture from step three into the quartz sleeve and place it in the second temperature zone; then place the silicon substrate cleaned in step two upside down on top of the quartz boat.

[0014] Step 5:

[0015] The three-zone tubular furnace was evacuated to reduce the internal pressure to below 10 Pa. Then, 500 sccm of hydrogen-argon mixture was introduced to flush the furnace. This "vacuuming-purging" cycle was repeated 2-3 times. After completing 2-3 cycles, the furnace was kept under vacuum, and the internal pressure was continuously monitored for 10 minutes. The pressure change curve was recorded. The pressure fluctuation was required to be ≤1 Pa within 10 minutes. If the pressure continued to rise, exceeding 1 Pa / 10 min, it indicated a possible hidden leak or residual air in the gas path. An additional "vacuuming-purging" cycle was required, and monitoring was repeated until the vacuum level stabilized, providing a clean environment for subsequent reactions.

[0016] Step Six:

[0017] After the gas filling and cleaning are completed, the carrier gas flow rate of the hydrogen-argon mixture is set. After the carrier gas flow rate stabilizes, the first and second temperature zones of the three-zone tubular furnace are heated to the target temperature and held for a period of time to grow a monolayer mixed-phase molybdenum telluride selenide material. Before cooling, the exhaust gas from the tubular furnace is treated by an exhaust gas treatment device to remove toxic components and then connected to a gas analyzer to detect the concentration of unreacted oxides of MoO3 and SeO2 in the exhaust gas. The concentration is required to be ≤1ppm. If the unreacted oxides exceed the standard, it indicates that the raw material reaction is insufficient. The holding time needs to be extended by 2-3 minutes, and the exhaust gas is detected again until the concentration of unreacted oxides meets the standard to reduce the impurity residue in subsequent samples. After the reaction is completed, when the tubular furnace cools down naturally to 400℃, the furnace lid is opened for rapid cooling until the furnace temperature drops to room temperature.

[0018] Step Seven:

[0019] The prepared molybdenum telluride selenide sample was cleaned with acetone solution to remove impurities and contaminants from its surface. Subsequently, it was cleaned with ethanol and deionized water in sequence to remove residual acetone from the surface of the molybdenum telluride selenide sample. The cleaned molybdenum telluride selenide sample was placed on a spin coater and AZ-5214 photoresist was spin-coated. Then, the uniformly spin-coated sample was placed on a gel coater at 100°C for 1 minute to gel. After gelation, it was stored away from light.

[0020] Step 8:

[0021] The required electrode pattern is etched on the sample surface with photoresist using laser direct writing technology. The sample is then placed in the developing solution for 18 seconds and then rinsed in deionized water for 10 seconds to remove residual developing solution.

[0022] Step Nine:

[0023] A vacuum evaporation process was used to first deposit a 10 nm thick chromium layer on the developing area of ​​the sample, followed by a 70 nm thick gold layer to form an electrode structure. The sample was then ultrasonically treated in acetone to remove the photoresist and metal layer from the undeveloped area. The sample was then cleaned with ethanol and deionized water in sequence to remove residual acetone, thus completing the fabrication of the photodetector device.

[0024] Preferably, in step one, the hydrogen concentration of the hydrogen-argon mixture is 10% by volume, wherein the hydrogen purity is ≥99.999% and the argon purity is ≥99.999%; during the hydrogen-argon mixture flushing process, the flushing time is 10-15 minutes per flush, and the residual air in the tubular furnace is completely replaced by multiple flushes.

[0025] Preferably, the mass of molybdenum dioxide (MoO2) powder in step three is 80mg to 150mg, the total mass of sodium bromide (NaBr) and sodium chloride (NaCl) is controlled at 1mg, and the mass ratio of the two is 1:1.

[0026] Preferably, in step four, the selenium powder has a mass of 10mg to 150mg, the tellurium particles have a mass of 500mg to 2.4g, and the particle size is 1-3mm; the quartz sleeve in step four is a quartz sleeve with a length of 60cm, an inner diameter of 2.8cm, an outer diameter of 3.2cm, and both ends are open; the quartz boat containing the selenium powder in step four is located in the first temperature zone and is 10cm to 15cm away from the substrate, the quartz boat containing the tellurium particles is located between the first and second temperature zones and is 4cm to 6cm away from the substrate, and the silicon substrate needs to be placed upside down 0.5cm to 1.5cm above the molybdenum source.

[0027] Preferably, in step six, the target temperature of the first temperature zone is 250℃~350℃, more preferably 320℃, and the target temperature of the second temperature zone is 700℃~800℃, more preferably 740℃. The temperature is maintained for 10~20 minutes. During the maintenance process, the flow rate fluctuation of the hydrogen-argon mixture carrier gas needs to be controlled within ±5sccm to avoid flow rate fluctuations affecting the volatilization and transport of the source material. In step six, the heating rate of both the first and second temperature zones is 20℃ / min. The first temperature zone needs to be heated for 15min~25min in the second temperature zone before the second temperature zone is heated. Temperature timing control ensures that both temperature zones reach the target temperature simultaneously.

[0028] Preferably, the spin coating process of the photoresist in step seven is as follows: first, spin coating at a low speed of 500 rpm for 6 seconds, and then spin coating at a high speed of 4000 rpm for 35 seconds. The thickness of the photoresist film formed after high-speed spin coating needs to be controlled between 1.5-2.0 μm. At the same time, it is necessary to ensure that the photoresist is fully cured and no bubbles are generated.

[0029] Preferably, the molybdenum telluride selenide (MoSe) mentioned in step six 2(1-x) Te 2xIt is a single-layer material whose phase structure is a planar homogeneous junction formed by the mixing of 2H and 1T' phases, with a composition x = 0.54 to 0.7, which can be adjusted by controlling the mass ratio of tellurium / selenium growth source within the range of 20:1 to 10:1.

[0030] Preferably, the substrate in step two is a 1cm × 1cm p-type heavily doped silicon substrate, and the doping concentration of the silicon substrate is 1 × 10⁻⁶. 18 -5×10 19 cm -3 A 300nm thick silicon dioxide (SiO2) oxide layer is grown on the substrate surface. The surface roughness Ra of the oxide layer is ≤0.5nm, and the oxide layer is free of defects such as pinholes and cracks.

[0031] Preferably, the vacuum degree of the vacuum evaporation process in step nine needs to be maintained at 5 × 10⁻⁶. -4 Below Pa, the chromium layer has a deposition thickness of 10 nm, and the deposition rate is constant at 0.2 nm / min. The chromium layer, acting as a transition layer, ensures adhesion between the gold layer and the molybdenum telluride selenide material ≥ 5 N / cm². 2 The gold layer has a deposition thickness of 70 nm, and the deposition rate is controlled in three stages: the first stage is a low deposition rate of 0.5 nm / min for the first 10 minutes, the second stage is a high deposition rate of 5 nm / min for the middle 12 minutes, and the third stage is a low deposition rate of 0.5 nm / min for the last 10 minutes.

[0032] Preferably, the monolayer mixed-phase molybdenum telluride selenide material is used in the fabrication of photoelectric detectors.

[0033] The beneficial effects of this invention are as follows:

[0034] This application provides a monolayer mixed-phase molybdenum telluride (MoSe) 2(1-x) Te 2x The material is a MoSe formed by a mixture of 2H and 1T' phases. 2(1-x) Te 2x The planar homojunction, with a thickness of approximately 0.7 nm, exhibits a crystal phase ratio and band gap that can be flexibly controlled according to the tellurium / selenium ratio, thus meeting the application requirements of nanoelectronic and optoelectronic devices. Secondly, a method for preparing this monolayer mixed-phase molybdenum telluride selenide material is provided. This method is a one-step molten salt-assisted chemical vapor deposition (MCCVD) method, resulting in monolayer mixed-phase molybdenum telluride selenide material with high crystal quality and obvious phase mixing characteristics. Furthermore, the method itself is characterized by its simple operation, mild reaction, and high reproducibility. Finally, the application of this monolayer mixed-phase molybdenum telluride selenide material in photodetectors is presented. Compared to single-phase TMD photodetectors, photodetectors prepared from this material have advantages such as a wider spectral response range, higher detection sensitivity, and faster response speed. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the three-temperature zone CVD tube furnace equipment used in this embodiment of the invention;

[0036] Figure 2 This is an optical microscope image of a typical monolayer mixed-phase molybdenum telluride obtained in Example 1 of the present invention under a high magnification microscope.

[0037] Figure 3 Atomic force microscopy morphology and height diagram of a typical monolayer mixed phase molybdenum telluride obtained in Example 1 of the present invention.

[0038] Figure 4 This is the Raman spectrum of the monolayer mixed telluride selenide corresponding to Example 1 of the present invention;

[0039] Figure 5 This is the Raman spectral mapping diagram of a typical monolayer phase mixed molybdenum telluride selenide obtained in Example 1 of the present invention;

[0040] Figure 6 This is a fine elemental photoelectron spectroscopy (XPS) spectrum of a typical monolayer mixed molybdenum telluride selenide obtained in Example 1 of this invention.

[0041] Figure 7 The Raman spectra of monolayer phase mixed telluride selenide with different components are shown in Examples 1-3 of this invention.

[0042] Figure 8 This is a schematic image of a test of a monolayer mixed molybdenum telluride selenide alloy device prepared based on Example 1;

[0043] Figure 9 Optical microscope images of the monolayer mixed molybdenum telluride selenide alloy device prepared based on Example 1;

[0044] Figure 10 The image shows a comparison of the signal-to-noise ratio of a single-layer mixed molybdenum telluride selenide alloy device at different bias voltages at 520 nm, 638 nm, and 940 nm.

[0045] Figure 11 The image shows the IV characteristics of a device based on a monolayer mixed molybdenum telluride selenide alloy under different optical power illumination at a wavelength of 940 nm.

[0046] Figure 12 The graph shows the responsivity and detectivity calculated under different optical powers at a 3V bias for a single-layer mixed molybdenum telluride selenide alloy device.

[0047] Figure 13 This is an optical microscope image of a typical 2H phase molybdenum telluride selenide alloy obtained in Comparative Example 1 of this invention under high magnification.

[0048] Figure 14This is an atomic force microscope height diagram of a typical 2H phase molybdenum telluride selenide alloy obtained in Comparative Example 1 of the present invention.

[0049] Figure 15 Raman spectral mapping of a typical 2H phase molybdenum telluride selenide alloy obtained in Comparative Example 1 of this invention;

[0050] Figure 16 The Raman spectra of the 2H phase molybdenum telluride selenide alloys with different compositions obtained in Comparative Examples 1-3 of this invention are shown in comparison.

[0051] Figure 17 The fluorescence spectra of 2H phase molybdenum telluride selenide alloys with different compositions obtained in Comparative Examples 1, 2, and 3 of this invention are shown in the comparison diagram.

[0052] Figure 18 This is a comparison chart of the responsivity and detectivity of the devices prepared in Example 1, Comparative Example 1, and Comparative Example 3 of the present invention at different laser wavelengths.

[0053] Figure 19 This is a high-magnification optical microscope image of a typical monolayer 1T' phase molybdenum telluride selenide alloy obtained in Comparative Example 4 of the present invention.

[0054] Figure 20 This is an atomic force microscope height diagram of a typical monolayer 1T' phase molybdenum telluride alloy obtained in Comparative Example 4 of the present invention.

[0055] Figure 21 The Raman spectrum of a typical monolayer 1T' phase molybdenum telluride alloy obtained in Comparative Example 4 of this invention is shown.

[0056] Figure 22 For the typical monolayer 1T' phase molybdenum telluride alloy obtained in Comparative Example 4 of this invention, A was selected. g Raman spectrum mapping of the peak. Detailed Implementation

[0057] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0058] Example 1

[0059] like Figures 1 to 12 As shown, this invention provides a single-layer mixed-phase molybdenum telluride selenide material, its preparation method, and its application. The specific steps are as follows:

[0060] Step 1:

[0061] The three-zone tubular furnace and quartz sleeve were wiped with anhydrous ethanol until no visible stains or impurities were visible on the surface, ensuring cleanliness. After wiping the surfaces of the tubular furnace and quartz sleeve, the quartz sleeve was installed at the furnace interface, the furnace door was closed, and the sealing bolts were tightened. The tubular furnace system was then tested for leak resistance using a helium mass spectrometer, requiring a system leak rate ≤ 5 × 10⁻⁶. -9 Pa·m 3 / s, if a leak is detected, the interface needs to be disassembled and the fluororubber gasket that can withstand temperatures above 300℃ replaced. After reassembly, the leak is checked again until the sealing requirements are met. Then, the tube furnace is annealed at 700℃ for 10 minutes. During the annealing process, a 500 sccm hydrogen-argon mixture is passed through to flush the furnace more than twice to ensure that the reaction environment is pure and free from pollution.

[0062] Step Two:

[0063] A 1cm×1cm silicon-based (SiO2 / Si) substrate was selected and cleaned sequentially with acetone, ethanol and deionized water, and then dried with nitrogen to remove impurities from the substrate surface before use.

[0064] Step 3:

[0065] An appropriate amount of 80 mg of molybdenum dioxide (MoO2), 1 mg of sodium bromide (NaBr) and 1 mg of sodium chloride (NaCl) solid powder were placed in a grinding mortar and ground thoroughly for more than 5 minutes under inert gas protection until they were mixed evenly. Then, 40 mg of the mixture was weighed and placed in a quartz boat as a reaction precursor.

[0066] Step Four:

[0067] Weigh 120 mg of selenium powder and 2.4 g of tellurium particles, with a tellurium / selenium mass ratio of 20:1. Place them separately in two quartz boats inside a quartz sleeve. Position the quartz boat containing the selenium powder in the first temperature zone, 15 cm from the substrate. Position the quartz boat containing the tellurium particles between the first and second temperature zones, 6 cm from the substrate. Place the quartz boat containing the above mixture from step three into the quartz sleeve and position it in the second temperature zone. Then, invert the silicon substrate cleaned in step two, placing it 1 cm above the quartz boat.

[0068] Step 5:

[0069] The three-zone tubular furnace was evacuated to reduce the internal pressure to below 10 Pa. Then, 500 sccm of hydrogen-argon mixture was introduced to flush the furnace. This "vacuuming-purging" cycle was repeated 2-3 times. After completing 2-3 cycles, the furnace was kept under vacuum, and the internal pressure was continuously monitored for 10 minutes. The pressure change curve was recorded. The pressure fluctuation was required to be ≤1 Pa within 10 minutes. If the pressure continued to rise, exceeding 1 Pa / 10 min, it indicated a possible hidden leak or residual air in the gas path. An additional "vacuuming-purging" cycle was required, and monitoring was repeated until the vacuum level stabilized, providing a clean environment for subsequent reactions.

[0070] Step Six:

[0071] After gas filling and cleaning, chemical vapor deposition (CVD) is used. A hydrogen-argon mixture with a flow rate of 90 sccm is introduced, and the hydrogen concentration in the mixture is 10% by volume. After the carrier gas flow rate stabilizes, the second zone of the three-zone tubular furnace is heated to 740℃ at a rate of 20℃ / min for 20 minutes, and then the first zone is heated to 300℃ and held for 20 minutes to grow a monolayer mixed-phase molybdenum telluride selenide material. Before cooling, the exhaust gas from the tubular furnace is treated to remove toxic components and then connected to a gas analyzer to detect the concentration of unreacted oxides of MoO3 and SeO2 in the exhaust gas. The concentration is required to be ≤1ppm. If the unreacted oxides exceed the standard, it indicates that the raw material reaction is insufficient, and the holding time needs to be extended by 2-3 minutes. The exhaust gas is then tested again until the concentration of unreacted oxides meets the standard to reduce impurities in subsequent samples. After the reaction is completed, the tubular furnace is allowed to cool naturally to 400℃. Then, the furnace lid is opened for rapid cooling until the furnace temperature drops to room temperature.

[0072] Step Seven:

[0073] The prepared molybdenum telluride selenide sample was cleaned with acetone solution to remove impurities and contaminants from its surface. Then, it was cleaned sequentially with ethanol and deionized water to remove any residual acetone. The cleaned molybdenum telluride selenide sample was placed on a spin coater, and 2 ml of AZ-5214 photoresist was added. The sample was then spin-coated at a low speed of 400 rpm for 6 seconds, followed by a high-speed spin coat at 4000 rpm for 35 seconds. The uniformly spin-coated sample was then placed on a gel coater at 100°C for 1 minute and stored away from light.

[0074] Step 8:

[0075] The required electrode pattern is etched on the sample surface with photoresist using laser direct writing technology. The sample is then placed in the developing solution for 18 seconds and then rinsed in deionized water for 10 seconds to remove residual developing solution.

[0076] Step Nine:

[0077] A vacuum evaporation process was used to first deposit a 10 nm thick chromium layer on the developing area of ​​the sample, followed by a 70 nm thick gold layer to form an electrode structure. The sample was then ultrasonically treated in acetone to remove the photoresist and metal layer from the undeveloped area. The sample was then cleaned with ethanol and deionized water in sequence to remove residual acetone, thus completing the fabrication of the photodetector device.

[0078] In step one, the hydrogen concentration of the hydrogen-argon mixture is 10% by volume, and the purity of the hydrogen is ≥99.999% and the purity of the argon is ≥99.999%. During the hydrogen-argon mixture flushing process, the flushing time is 10-15 minutes, and the residual air in the tubular furnace is completely replaced by multiple flushes.

[0079] By specifying that hydrogen accounts for 10% of the volume of the hydrogen-argon mixture and has a gas purity of ≥99.999%, the reducing atmosphere required for the reaction can be ensured to be stable and free from impurities. At the same time, limiting each flush to 10-15 minutes allows for the thorough replacement of residual air in the tubular furnace through multiple flushes, further improving the purity of the reaction environment. This provides a clean foundation for the subsequent growth of monolayer mixed-phase molybdenum telluride selenide materials and avoids impurities affecting the purity and phase structure of the materials.

[0080] In step three, the mass of molybdenum dioxide (MoO2) powder is 80mg to 150mg, the total mass of sodium bromide (NaBr) and sodium chloride (NaCl) is controlled at 1mg, and the mass ratio of the two is 1:1.

[0081] By defining the mass range of molybdenum dioxide powder from 80mg to 150mg, the supply of molybdenum source can be precisely controlled. Limiting the total mass of sodium bromide and sodium chloride to 1mg and the mass ratio to 1:1 can stabilize the flux concentration, avoid material agglomeration and impurity residue caused by imbalance of raw material dosage or ratio, ensure the uniformity of precursor mixing, and provide a suitable material ratio for the stable growth of monolayer materials.

[0082] In step four, the selenium powder weighs 10mg to 150mg, the tellurium particles weigh 500mg to 2.4g, and the particle size is 1-3mm. The quartz sleeve in step four is a quartz sleeve with a length of 60cm, an inner diameter of 2.8cm, an outer diameter of 3.2cm, and both ends are open. The quartz boat containing the selenium powder in step four is located in the first temperature zone and is 10cm to 15cm away from the substrate. The quartz boat containing the tellurium particles is located between the first and second temperature zones and is 4cm to 6cm away from the substrate. The silicon substrate needs to be placed upside down 0.5cm to 1.5cm above the molybdenum source.

[0083] By clearly defining the mass range and particle size of selenium powder and tellurium particles, the volatilization rate of selenium and tellurium sources can be controlled. Fixing the specifications of the quartz sleeve ensures the stability of the gas path space. Precisely limiting the distance between each quartz boat and the substrate ensures that the transport paths of selenium, tellurium and molybdenum source materials are consistent, making the growth conditions on the substrate surface uniform, avoiding uneven material thickness or phase structure differences, and improving the repeatability and consistency of material growth.

[0084] In step six, the target temperature for the first temperature zone is 250℃~350℃, preferably 320℃, and the target temperature for the second temperature zone is 700℃~800℃, preferably 740℃. The temperature is maintained for 10~20 minutes. During the maintenance process, the flow rate fluctuation of the hydrogen-argon mixture carrier gas needs to be controlled within ±5sccm to avoid flow rate fluctuations affecting the volatilization and transport of the source material. In step six, the heating rate of both the first and second temperature zones is 20℃ / min. The first temperature zone needs to be heated for 15min~25min in the second temperature zone before the second temperature zone is heated. Temperature timing control ensures that both temperature zones reach the target temperature simultaneously.

[0085] By clearly defining the target temperatures and 10-20 minute holding times for the first and second temperature zones, the material growth kinetics can be precisely controlled. Optimizing the temperature further enhances growth efficiency and material quality. Controlling carrier gas flow rate fluctuations to ≤±5 sccm avoids instability in source material transport. A reasonable heating sequence ensures that both temperature zones reach the target temperature simultaneously, avoiding component segregation caused by temperature differences and guaranteeing the stability of the monolayer structure and mixed phase ratio of the molybdenum telluride selenide material.

[0086] In step seven, the photoresist spin coating process is as follows: first, spin coating at a low speed of 500 rpm for 6 seconds, and then spin coating at a high speed of 4000 rpm for 35 seconds. The thickness of the photoresist film formed after high-speed spin coating needs to be controlled between 1.5-2.0 μm. At the same time, it is necessary to ensure that the photoresist is fully cured and no bubbles are generated.

[0087] The spin coating process of 500 rpm for 6 seconds and 4000 rpm for 35 seconds for photoresist is clearly defined, which can precisely control the photoresist film thickness and ensure film thickness uniformity.

[0088] In step six, molybdenum telluride selenide (MoSe) 2(1-x) Te 2x It is a single-layer material whose phase structure is a planar homogeneous junction formed by the mixing of 2H and 1T' phases, with a composition x = 0.54 to 0.7, which can be adjusted by controlling the mass ratio of tellurium / selenium growth source within the range of 20:1 to 10:1.

[0089] The single-layer properties ensure the material's two-dimensional electron transport performance, while the mixed-phase structure can create a built-in electric field to improve photoelectric conversion efficiency.

[0090] In step two, the substrate is a 1cm × 1cm p-type heavily doped silicon substrate with a doping concentration of 1 × 10⁻⁶. 18 -5×10 19 cm -3 A 300nm thick silicon dioxide (SiO2) oxide layer is grown on the substrate surface. The surface roughness Ra of the oxide layer is ≤0.5nm, and the oxide layer is free of defects such as pinholes and cracks.

[0091] The heavy doping properties of the substrate provide a good conductive substrate, and the 300nm oxide layer achieves electrical isolation between the substrate and the material.

[0092] In step nine, the vacuum level of the vacuum evaporation process needs to be maintained at 5 × 10⁻⁶. -4 Below Pa, the chromium layer has a deposition thickness of 10 nm, and the deposition rate is constant at 0.2 nm / min. The chromium layer, acting as a transition layer, ensures adhesion between the gold layer and the molybdenum telluride selenide material ≥ 5 N / cm². 2 The gold layer has a deposition thickness of 70 nm, and the deposition rate is controlled in three stages: the first stage is a low deposition rate of 0.5 nm / min for the first 10 minutes, the second stage is a high deposition rate of 5 nm / min for the middle 12 minutes, and the third stage is a low deposition rate of 0.5 nm / min for the last 10 minutes.

[0093] The 70nm gold layer thickness and the three-stage evaporation speed control (low-high-low speed) can reduce internal stress in the gold layer to prevent cracking, ensure the conductivity and structural integrity of the electrode structure, and improve the performance stability and service life of photodetector electrodes.

[0094] Among them, monolayer mixed-phase molybdenum telluride selenide materials are used to prepare photoelectric detectors.

[0095] Example 2:

[0096] like Figure 7 As shown, this embodiment of the invention provides a monolayer mixed-phase molybdenum telluride material with lower tellurium content and its preparation method. Specifically, the mass of tellurium particles is 2.4g, the mass of selenium powder is 160mg, and the mass ratio of tellurium to selenium is 15:1 to prepare a monolayer mixed-phase molybdenum telluride sample.

[0097] The difference from Example 1 is that in this example, the mass of selenium powder used is 160mg, the mass ratio of tellurium to selenium is 15:1, and the first temperature zone starts to heat up 17 minutes after the second temperature zone heats up, and the second temperature zone heats up to 720°C.

[0098] Example 3:

[0099] like Figure 7As shown, this embodiment of the invention provides a monolayer mixed-phase molybdenum telluride material with the lowest tellurium content and its preparation method. Specifically, the mass of tellurium particles is 2g, the mass of selenium powder is 200mg, and the mass ratio of tellurium to selenium is 10:1 to prepare a monolayer mixed-phase molybdenum telluride sample.

[0100] The difference from Example 1 is that the mass of tellurium granules used in this example is 2g, the mass of selenium powder is 200mg, the mass ratio of tellurium to selenium is 10:1, and the first temperature zone starts to heat up 15 minutes after the second temperature zone heats up, and the second temperature zone heats up to 770°C. Other aspects of the invention are the same as in Example 1.

[0101] The samples obtained in Examples 1, 2, and 3 were all monolayer 2H / 1T' mixed-phase molybdenum telluride (MoSe). 2(1-x) Te 2x The XPS and Raman spectroscopy characterization demonstrates that by changing the tellurium / selenium mass ratio using this growth method, the mixed-phase molybdenum telluride selenide can be grown in a controllable manner within the component x range of 0.54 to 0.7; (refer to the attached manual). Figure 1 and 2 It can be observed that it is composed of hexagonal crystal domains of the 2H phase and strip-shaped crystal domains of the 1T' phase, with a thickness of approximately 0.7 nm, proving that it is a single-layer structure; combined with the appendix of the specification. Figure 5 This further proves that it is composed of 2H phase and 1T' phase crystal domains; combined with the appendix to the specification. Figure 6 Integrating its characteristic peak positions yields an actual component x of 0.7; according to the instruction manual appendix... Figure 7 It can be seen that with the increase of the tellurium / selenium mass ratio, the proportion of tellurium component in the sample increases, and the vibration peak of the 1T' phase gradually strengthens, indicating that the composition and phase ratio of mixed-phase molybdenum telluride selenide can be controlled by changing the tellurium / selenium mass ratio; combined with the appendix to the instruction manual... Figure 10 As can be seen, the instruction manual includes... Figure 9 The photodetector shown exhibits excellent signal-to-noise ratio in the visible-near-infrared band, achieving a wide range of spectral detection, and is described in the accompanying manual. Figure 11 The IV characteristic curves show that the device has a good optical response in the 940nm near-infrared region. (See attached datasheet.) Figure 12 It exhibits a responsivity as high as 248.4 mA / W and a specific detectivity of 2.17 × 10⁻⁶. 12 Jones.

[0102] Comparative Example 1

[0103] This comparative example provides a monolayer mixed-phase molybdenum telluride selenide material. The preparation method differs from that of Example 1 only in that the mass of tellurium particles in step 4 of Example 1 is changed to 800 mg, the mass of selenium powder is changed to 200 mg, and the mass ratio of tellurium to selenium is 4:1. A monolayer 2H phase molybdenum telluride selenide sample is prepared. In step six, the first temperature zone and the second temperature zone are heated simultaneously. All other steps are the same.

[0104] Comparative Example 2

[0105] This comparative example provides a monolayer mixed-phase molybdenum telluride selenide material. The preparation method differs from that of Example 1 only in that the mass of tellurium particles in step 4 of Example 1 is changed to 200 mg, the mass of selenium powder is changed to 200 mg, and the mass ratio of tellurium to selenium is 1:1. A monolayer 2H phase molybdenum telluride selenide sample is prepared. In step six, the first temperature zone and the second temperature zone are heated simultaneously, and the second temperature zone is heated to 770°C. All other steps are the same.

[0106] Comparative Example 3

[0107] This comparative example provides a monolayer mixed-phase molybdenum telluride selenide material. The preparation method differs from that of Example 1 only in that the mass of tellurium particles in step 4 of Example 1 is changed to 100 mg, the mass of selenium powder is changed to 300 mg, and the mass ratio of tellurium to selenium is 1:3. A monolayer 2H phase molybdenum telluride selenide sample is prepared. In step six, the first temperature zone and the second temperature zone are heated simultaneously, and the second temperature zone is heated to 800°C. All other steps are the same.

[0108] Comparative Examples 1, 2, and 3 did not use a delayed heating method, and the temperature and tellurium / selenium source mass ratio were reduced compared to Example 1. All prepared samples were monolayer 2H phase molybdenum telluride selenide. (See attached instruction manual.) Figure 13 Included with instruction manual Figure 14 The images show the optical morphology and AFM morphology and height diagram of a typical molybdenum telluride selenide domain prepared in Comparative Example 1, respectively. It exhibits hexagonal domains with a thickness of 0.71 nm, confirming its monolayer structure. (See attached specification.) Figure 15 Sample A prepared for Comparative Example 1 1g The peak Raman mapping diagram, with its highly consistent color contrast, demonstrates the uniformity of its structure; see instruction manual attached. Figure 16 The Raman spectra of the samples prepared in Comparative Examples 1, 2, and 3 show that as the tellurium / selenium mass ratio increases, all Raman characteristic peaks undergo a blue shift, and the A1g peak weakens, while the E... 2g The peak is increasing, indicating that its composition can be controlled by the tellurium / selenium mass ratio; see the attached instruction manual. Figure 17 The photoluminescence spectra of the samples prepared in Examples 1, 2, and 3 are shown. The blue shift of the emission peak position proves that the proportion of tellurium component decreases accordingly with the decrease of the tellurium / selenium mass ratio; see the attached instruction manual. Figure 18The performance of molybdenum telluride selenide devices with different compositions and crystal phases was compared, demonstrating that increasing the tellurium content can broaden the wavelength detection range, and that the mixed phase structure greatly improves the device sensitivity.

[0109] Comparative Example 4

[0110] This comparative example provides a monolayer mixed-phase molybdenum telluride selenide material. The preparation method differs from that of Example 1 only in that the mass of tellurium particles in step 4 of Example 1 is changed to 2.4g, the mass of selenium powder is changed to 50mg, and the mass ratio of tellurium to selenium is 48:1. A monolayer 1T' phase molybdenum telluride selenide sample is prepared. In step six, the first temperature zone starts heating 25 minutes after the second temperature zone, and the second temperature zone is heated to 720℃. All other steps are the same.

[0111] Comparative Example 5

[0112] This comparative example provides a monolayer mixed-phase molybdenum telluride selenide material. The preparation method differs from that of Example 1 only in that the mass of tellurium particles in step 4 of Example 1 is changed to 2.4g, the mass of selenium powder is changed to 50mg, and the mass ratio of tellurium to selenium is 48:1. A monolayer 1T' phase molybdenum telluride selenide sample is prepared. In step six, the first temperature zone and the second temperature zone are heated simultaneously, and the second temperature zone is heated to 720℃. All other steps are the same.

[0113] The samples prepared in Comparative Examples 4 and 5 were both monolayer 1T' phase molybdenum telluride, as per the instruction manual. Figure 19 The image shown is a high-magnification optical microscope image of typical 1T' phase molybdenum telluride selenide domains prepared in Comparative Example 4, exhibiting a strip-like or band-like morphology; see the instruction manual attached. Figure 20 The AFM morphology and height diagram of a typical 1T' phase molybdenum telluride selenide domain prepared for Comparative Example 1 are shown, with a thickness of 0.69 nm, confirming its monolayer structure; see attached specification. Figure 21 The Raman spectrum of the sample prepared in Comparative Example 1 is shown in Figure A. g and B g The peak confirms that it belongs to the 1T' phase structure; see attached manual. Figure 22 Sample A prepared for Comparative Example 1 g The Raman mapping images show uniform color and brightness, indicating high crystal quality and good structural consistency. Compared with Examples 1-3 and Comparative Examples 1-3, the tellurium / selenium mass ratio of Examples 4 and 5 is 48:1, the growth temperature is 720℃, and the results remain unchanged regardless of whether a delayed heating method is used. This indicates that when the experimental tellurium / selenium mass ratio is increased to 48:1, the grown sample is a monolayer molybdenum telluride selenide of the 1T' phase.

[0114] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0115] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A single-layer mixed-phase molybdenum telluride selenide material and its preparation method, characterized in that, The specific steps are as follows: Step 1: The three-zone tubular furnace and quartz sleeve were wiped with anhydrous ethanol until no visible stains or impurities were visible on the surface, ensuring cleanliness. After wiping the surfaces of the tubular furnace and quartz sleeve, the quartz sleeve was installed at the furnace interface, the furnace door was closed, and the sealing bolts were tightened. The tubular furnace system was then tested for leak resistance using a helium mass spectrometer, requiring a system leak rate ≤ 5 × 10⁻⁶. -9 Pa·m 3 / s, if a leak is detected, the interface needs to be disassembled and the fluororubber gasket that can withstand temperatures above 300℃ replaced. After reassembly, the leak is checked again until the sealing requirements are met. Then, the tubular furnace is annealed at 600℃~700℃. During the annealing process, a 500sccm hydrogen-argon mixture is passed through to flush the furnace more than twice to ensure that the reaction environment is pure and free from pollution. Step Two: A 1cm×1cm silicon-based (SiO2 / Si) substrate was selected and cleaned sequentially with acetone, ethanol and deionized water, and then dried with nitrogen to remove impurities from the substrate surface before use. Step 3: Weigh appropriate amounts of molybdenum dioxide (MoO2), sodium bromide (NaBr), and sodium chloride (NaCl) solid powders, place them in a grinding mortar, and grind them thoroughly under inert gas protection until they are mixed evenly. Then place the mixture in a quartz boat as a reaction precursor. Step Four: Weigh appropriate amounts of selenium powder and tellurium granules, and place them in two quartz boats inside a quartz sleeve: place the quartz boat containing the selenium powder in the first temperature zone, and place the quartz boat containing the tellurium granules between the first and second temperature zones; place the quartz boat containing the above mixture from step three into the quartz sleeve and place it in the second temperature zone; then place the silicon substrate cleaned in step two upside down on top of the quartz boat. Step 5: The three-zone tubular furnace was evacuated to reduce the internal pressure to below 10 Pa. Then, 500 sccm of hydrogen-argon mixture was introduced to flush the furnace. This "vacuuming-purging" cycle was repeated 2-3 times. After completing 2-3 cycles, the furnace was kept under vacuum, and the internal pressure was continuously monitored for 10 minutes. The pressure change curve was recorded. The pressure fluctuation was required to be ≤1 Pa within 10 minutes. If the pressure continued to rise, exceeding 1 Pa / 10 min, it indicated a possible hidden leak or residual air in the gas path. An additional "vacuuming-purging" cycle was required, and monitoring was repeated until the vacuum level stabilized, providing a clean environment for subsequent reactions. Step Six: After the gas filling and cleaning are completed, the carrier gas flow rate of the hydrogen-argon mixture is set. After the carrier gas flow rate stabilizes, the first and second temperature zones of the three-zone tubular furnace are heated to the target temperature and held for a period of time to grow a monolayer mixed-phase molybdenum telluride selenide material. Before cooling, the exhaust gas from the tubular furnace is treated by an exhaust gas treatment device to remove toxic components and then connected to a gas analyzer to detect the concentration of unreacted oxides of MoO3 and SeO2 in the exhaust gas. The concentration is required to be ≤1ppm. If the unreacted oxides exceed the standard, it indicates that the raw material reaction is insufficient. The holding time needs to be extended by 2-3 minutes, and the exhaust gas is detected again until the concentration of unreacted oxides meets the standard to reduce the impurity residue in subsequent samples. After the reaction is completed, when the tubular furnace cools down naturally to 400℃, the furnace lid is opened for rapid cooling until the furnace temperature drops to room temperature. Step Seven: The prepared molybdenum telluride selenide sample was cleaned with acetone solution to remove impurities and contaminants from its surface. Subsequently, it was cleaned with ethanol and deionized water in sequence to remove residual acetone from the surface of the molybdenum telluride selenide sample. The cleaned molybdenum telluride selenide sample was placed on a spin coater and AZ-5214 photoresist was spin-coated. Then, the uniformly spin-coated sample was placed on a gel coater at 100°C for 1 minute to gel. After gelation, it was stored away from light. Step 8: The required electrode pattern is etched on the sample surface with photoresist using laser direct writing technology. The sample is then placed in the developing solution for 18 seconds and then rinsed in deionized water for 10 seconds to remove residual developing solution. Step Nine: A vacuum evaporation process was used to first deposit a 10 nm thick chromium layer on the developing area of ​​the sample, followed by a 70 nm thick gold layer to form an electrode structure. The sample was then ultrasonically treated in acetone to remove the photoresist and metal layer from the undeveloped area. The sample was then cleaned with ethanol and deionized water in sequence to remove residual acetone, thus completing the fabrication of the photodetector device.

2. The single-layer mixed-phase molybdenum telluride material and its preparation method according to claim 1, characterized in that: In step one, the hydrogen concentration of the hydrogen-argon mixture is 10% by volume, and the purity of the hydrogen is ≥99.999% and the purity of the argon is ≥99.999%. During the hydrogen-argon mixture flushing process, the flushing time is 10-15 minutes, and the residual air in the tubular furnace is completely replaced by multiple flushes.

3. The single-layer mixed-phase molybdenum telluride material and its preparation method according to claim 1, characterized in that: In step three, the mass of molybdenum dioxide (MoO2) powder is 80mg to 150mg, and the total mass of sodium bromide (NaBr) and sodium chloride (NaCl) is controlled at 1mg, with a mass ratio of 1:

1.

4. The single-layer mixed-phase molybdenum telluride material and its preparation method according to claim 1, characterized in that: The selenium powder in step four has a mass of 10mg to 150mg, the tellurium particles have a mass of 500mg to 2.4g, and a particle size of 1-3mm. The quartz sleeve in step four is a quartz sleeve with a length of 60cm, an inner diameter of 2.8cm, an outer diameter of 3.2cm, and both ends are open. The quartz boat containing the selenium powder in step four is located in the first temperature zone and is 10cm to 15cm away from the substrate. The quartz boat containing the tellurium particles is located between the first and second temperature zones and is 4cm to 6cm away from the substrate. The silicon substrate needs to be placed upside down 0.5cm to 1.5cm above the molybdenum source.

5. The monolayer mixed-phase molybdenum telluride material and its preparation method according to claim 1, characterized in that: In step six, the target temperature of the first temperature zone is 250℃~350℃, preferably 320℃, and the target temperature of the second temperature zone is 700℃~800℃, preferably 740℃. The temperature is maintained for 10~20 minutes. During the holding period, the flow rate fluctuation of the hydrogen-argon mixture carrier gas needs to be controlled within ±5sccm to avoid flow rate fluctuations affecting the volatilization and transport of the source material. In step six, the heating rate of both the first and second temperature zones is 20℃ / min. The first temperature zone needs to be heated for 15min~25min in the second temperature zone before the first temperature zone is heated. Temperature timing control ensures that both temperature zones reach the target temperature simultaneously.

6. The single-layer mixed-phase molybdenum telluride material and its preparation method according to claim 1, characterized in that: The photoresist spin coating process described in step seven is as follows: first, spin coating at a low speed of 500 rpm for 6 seconds, and then spin coating at a high speed of 4000 rpm for 35 seconds. The thickness of the photoresist film formed after high-speed spin coating needs to be controlled between 1.5-2.0 μm. At the same time, it is necessary to ensure that the photoresist is fully cured and no bubbles are generated.

7. The monolayer mixed-phase molybdenum telluride material and its preparation method according to claim 1, characterized in that: The molybdenum telluride selenide (MoSe) mentioned in step six 2(1-x) Te 2x It is a single-layer material whose phase structure is a planar homogeneous junction formed by the mixing of 2H and 1T' phases, with a composition x = 0.54 to 0.7, which can be adjusted by controlling the mass ratio of tellurium / selenium growth source within the range of 20:1 to 10:

1.

8. The monolayer mixed-phase molybdenum telluride material and its preparation method according to claim 1, characterized in that: The substrate mentioned in step two is a 1cm × 1cm p-type heavily doped silicon substrate, and the doping concentration of the silicon substrate is 1 × 10⁻⁶. 18 -5×10 19 cm -3 A 300nm thick silicon dioxide (SiO2) oxide layer is grown on the substrate surface. The surface roughness Ra of the oxide layer is ≤0.5nm, and the oxide layer is free of defects such as pinholes and cracks.

9. The single-layer mixed-phase molybdenum telluride material and its preparation method according to claim 1, characterized in that: The vacuum level in the vacuum evaporation process described in step nine needs to be maintained at 5 × 10⁻⁶. -4 Below Pa, the chromium layer has a deposition thickness of 10 nm, and the deposition rate is constant at 0.2 nm / min. The chromium layer, acting as a transition layer, ensures adhesion between the gold layer and the molybdenum telluride selenide material ≥ 5 N / cm². 2 The gold layer has a deposition thickness of 70 nm, and the deposition rate is controlled in three stages: the first stage is a low deposition rate of 0.5 nm / min for the first 10 minutes, the second stage is a high deposition rate of 5 nm / min for the middle 12 minutes, and the third stage is a low deposition rate of 0.5 nm / min for the last 10 minutes.

10. A single-layer mixed-phase molybdenum telluride material according to any one of claims 1-9, characterized in that: Application of the monolayer mixed-phase molybdenum telluride selenide material in the fabrication of photoelectric detectors.

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