Heteroepitaxial single crystal metal chalcogenide film and preparation and application thereof

Abstract

The invention relates to a heteroepitaxial single crystal metal chalcogenide film, the chemical formula of the film is MX2, M is any one of metals platinum, palladium, molybdenum and tungsten; x is any one of sulfur, selenium and tellurium in chalcogenide elements. Meanwhile, the invention also discloses a preparation method and application of the film. According to the method, the atom utilization rate and the loading capacity are effectively improved, compared with a monatomic catalyst which only disperses a small amount of active sites, the active sites can be provided to the maximum extent on the monatomic layer scale, and excellent catalytic activity is shown in hydrogen production through water splitting.

Description

Technical Field

[0001] The present invention relates to the field of new material electronic devices, and in particular to a heteroepitaxial single crystal metal sulfide compound film and the preparation and application thereof. Background Art

[0002] Two-dimensional transition metal dichalcogenides (2D-TMDs) have shown broad application prospects in electronics and catalysis due to their unique physical and chemical properties. In particular, two-dimensional platinum diselenide (2D PtSe2) has obvious advantages over traditional semiconductor phase 2D TMDs due to its higher carrier mobility, semi-metallic electrical properties and enhanced electrocatalytic activity. In electrocatalytic reactions, 2D PtSe2 forms a strong interfacial electric field, enhances the d-band center of the electrocatalyst, improves the adsorption of intermediate species, and significantly improves the efficiency and selectivity of the catalytic reaction, providing strong support for the development of high-performance catalysts.

[0003] However, due to the problems of easy vertical growth, uncontrollable number of layers and limited growth size faced by traditional CVD, the synthesis of wafer-level controllable number of layers of platinum selenide thin films still faces major challenges. As a solution, heteroepitaxial growth can controllably synthesize single-layer films. However, the synthesis conditions are harsh and require ultra-high vacuum, expensive metal precursors, etc.

[0004] In summary, although 2D-TMDs such as 2D PtSe2 have great application potential in electronics and catalysis, the preparation of wafer-level thin films still faces technical and cost challenges. Therefore, there is an urgent need for a single-crystalline transition metal chalcogenide thin film preparation that can achieve wafer-level and controllable number of layers to promote the development and application of related technologies. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a heteroepitaxial single crystal metal chalcogenide film which can effectively improve the atomic utilization rate and the loading amount.

[0006] Another technical problem to be solved by the present invention is to provide a method for preparing the heteroepitaxial single crystal metal chalcogenide film.

[0007] The third technical problem to be solved by the present invention is to provide application of the heteroepitaxial single crystal metal sulfide compound film.

[0008] To solve the above problems, the present invention discloses a heteroepitaxial single crystal metal chalcogenide film, characterized in that the chemical formula of the film is MX2, wherein: M is any one of the metals platinum, palladium, molybdenum, and tungsten; and X is any one of the chalcogen elements sulfur, selenium, and tellurium.

[0009] The film is a wafer-level single crystal structure. The thickness of the single-layer film is ~0.9 nm, the thickness of the double-layer film is ~2.3 nm, the diameter is 1 inch, and the epitaxial growth method is droplet-driven growth.

[0010] The method for preparing a heteroepitaxial single crystal metal chalcogenide film as described above comprises the following steps: (1) On a growth substrate, a metal is deposited by a thin film deposition technique to form a metal layer with a final thickness of 0.08 nm to 0.18 nm; the metal is any one of platinum (Pt), palladium (Pd), molybdenum (Mo), and tungsten (W); (2) Place the chalcogenide source in two alumina boats, and the growth substrate on which the metal is deposited in a quartz boat. The three are placed in a tubular container in sequence along the direction of the gas flow, and the distance between the chalcogenide source close to the growth substrate and the growth substrate is 2-5 cm, and the distance between the chalcogenide source far from the growth substrate and the growth substrate is 20-25 cm. The growth substrate on which the metal layer is deposited is placed in the center of the tubular furnace; introduce carrier gas, first raise the temperature to 500°C at 5°C / min at room temperature, then keep it at 500°C for 10 minutes for growth, and finally cool it naturally with the furnace to obtain a wafer-level heteroepitaxial single crystal metal chalcogenide compound film.

[0011] The growth substrate in step (1) refers to any one of SiO2 / Si, BN, mica, sapphire, MoS2, and MoSe2 substrates, and its size is 2 inches; among which the BN, MoS2, and MoSe2 substrates are single layers.

[0012] The thin film deposition technology in step (1) refers to electron beam evaporation, and its deposition rate is 0.01 Å / s.

[0013] In step (2), the two alumina boats are of different lengths, wherein the long alumina boat is close to the growth substrate, and the short alumina boat is far away from the growth substrate.

[0014] The mass ratio of the chalcogenide source placed in the long alumina boat to the chalcogenide source placed in the short alumina boat is 2-4:5.

[0015] The tubular container in step (2) refers to a tubular furnace with a heating device in the center.

[0016] The carrier gas in step (2) is a mixed gas consisting of argon with a flow rate of 60 sccm and hydrogen with a flow rate of 10 sccm.

[0017] The application of a heteroepitaxial single crystal metal sulfide compound thin film as described above is characterized in that the heteroepitaxial single crystal metal sulfide compound thin film catalyst is used as a cathode in electrochemical water splitting to produce hydrogen.

[0018] Compared with the prior art, the present invention has the following advantages: 1. The present invention effectively improves the atomic utilization and loading capacity by adding chalcogen elements to metal single atoms. Compared with single-atom catalysts that only disperse a small number of active sites, it can provide active sites to the maximum extent at the single-atom layer scale, and its atomic utilization rate is as high as 30%, thereby providing a highly potential design scheme for the preparation of efficient and low-cost metal single-atom catalysts.

[0019] 2. The present invention provides a droplet-driven growth method, which uses electron beam evaporation technology to prepare extremely small metal clusters with a diameter of 2 nm on different substrates, greatly reducing the melting point of the metal and the reaction energy barrier between the metal and the chalcogenide elements. At 500°C, the metal exists in liquid form, and selenium gas is introduced to drive the metal source droplets to grow a nanometer-level two-dimensional single-crystal single-layer heterostructure film.

[0020] 3. The present invention provides the possibility of growing large-sized single-crystal thin films on various substrates and is suitable for large-scale device manufacturing.

[0021] 4. The present invention adopts thin film deposition technology to controllably grow two-dimensional single crystal films of different numbers of layers. The area of ​​the generated film is controlled by controlling the amount of metal source. When the thickness of the metal layer is 0.1nm, it can just generate a uniform single crystal film by selenization. When the thickness of the metal layer is 0.18nm, it can just generate two uniform single crystal films, making it show the change of properties from semiconductor to semi-metal and then to metal.

[0022] 5. The present invention can controllably grow two-dimensional single crystal materials with different curvatures. By controlling the saturated vapor pressure of the chalcogenide source, the edge shape of the generated film can be changed. When the saturated vapor pressure is much greater than the vapor pressure of the metal source, the edge grows straight. Gradually reducing the vapor pressure of the chalcogenide source can increase the curvature of the film edge. Specific surface sites with large curvature have high catalytic activity. The present invention can maximize the use of these active sites, making them exhibit excellent catalytic performance.

[0023] 6. The electrolytic cell with the heteroepitaxial single crystal transition metal chalcogenide wafer-level thin film as the cathode can generate 1200 mA·cm at a potential of 0.75 V. -2 The high current density is similar to that of a pure platinum electrode, and it can stably and continuously produce high-flow hydrogen. Under the same conditions, its performance is better than most existing precious metal single-atom catalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0025] Figure 1The present invention is a schematic diagram of the preparation process of the heteroepitaxial single-crystalline metal chalcogenide wafer-level PtSe2 film.

[0026] Figure 2 This is a digital photo of the heteroepitaxial single-crystalline metal chalcogenide wafer-level PtSe2 thin film of the present invention.

[0027] Figure 3 This is a transmission electron microscope photograph of the heteroepitaxial single-crystalline metal chalcogenide wafer-level PtSe2 film of the present invention.

[0028] Figure 4 Transmission electron microscope images of heteroepitaxial single crystal metal chalcogenide wafer-level PtSe2 films with different Pt amounts of the present invention.

[0029] Figure 5 This is a selected area electron diffraction pattern of the heteroepitaxial single crystal metal chalcogenide wafer-level PtSe2 thin film of the present invention.

[0030] Figure 6 The Raman spectra of the heteroepitaxial single crystal metal chalcogenide wafer-level PtSe2 thin films with different Pt amounts of the present invention.

[0031] Figure 7 This is a luminescence spectrum diagram of the heteroepitaxial single-crystalline metal chalcogenide wafer-level PtSe2 thin film of the present invention.

[0032] Figure 8 This is an optical photograph of a micro-nano electrochemical device of the heteroepitaxial single-crystalline metal chalcogenide wafer-level PtSe2 thin film of the present invention.

[0033] Fig. 9 Polarization curves and corresponding mass activity diagrams, curvature diagrams, and perimeter-to-area ratio diagrams of heteroepitaxial single-crystalline metal chalcogenide wafer-level PtSe2 thin films with different Pt amounts in the present invention. DETAILED DESCRIPTION

[0034] A heteroepitaxial single-crystalline metal chalcogenide film, the chemical formula of which is MX2, where: M is any one of the metals platinum (Pt), palladium (Pd), molybdenum (Mo), and tungsten (W); X is any one of the chalcogen elements sulfur (S), selenium (Se), and tellurium (Te). The film is a wafer-level single crystal structure, with a single-layer film thickness of ~0.9 nm and a double-layer film thickness of ~2.3nm, a diameter of 1 inch, and an epitaxial growth method of droplet-driven growth.

[0035] Its preparation method is as follows Figure 1 As shown, the following steps are included: ⑴ On the growth substrate, the metal is deposited by thin film deposition technology to form a metal layer with a final thickness of 0.08 nm~0.18 nm; the metal is any one of platinum (Pt), palladium (Pd), molybdenum (Mo), and tungsten (W).

[0036] Wherein: the growth substrate refers to any one of SiO2 / Si, BN, mica, sapphire, MoS2, and MoSe2 substrates, and its size is 2 inches; wherein the BN, MoS2, and MoSe2 substrates are single layers.

[0037] The thin film deposition technology refers to electron beam evaporation, and its deposition rate is 0.01 Å / s.

[0038] ⑵ Place the chalcogenide source in two alumina boats, and the growth substrate for depositing metal in a quartz boat. The three are placed in a tubular container in sequence along the direction of the gas flow. The tubular container refers to a tubular furnace with a heating device in the center. The distance between the chalcogenide source close to the growth substrate and the growth substrate is 2~5 cm, and the distance between the chalcogenide source far from the growth substrate and the growth substrate is 20~25 cm. The growth substrate for depositing the metal layer is placed in the center of the tubular furnace and a carrier gas is introduced. The carrier gas refers to a mixed gas composed of argon with a flow rate of 60 sccm and hydrogen with a flow rate of 10 sccm. First, heat up to 500 ℃ at 5 ℃ / min at room temperature, then keep at 500 ℃ for 10 minutes for growth, and finally cool naturally with the furnace to obtain a wafer-level heteroepitaxial single crystal metal chalcogenide film.

[0039] The two alumina boats are of different lengths, wherein the long alumina boat is close to the growth substrate, and the short alumina boat is far away from the growth substrate.

[0040] The mass ratio (g / g) of the chalcogenide source placed in the long alumina boat to the chalcogenide source placed in the short alumina boat is 2 to 4:5.

[0041] The present invention uses a very small metal source and an excess of chalcogen source to regulate the saturated vapor pressure ratio of the metal source and the non-metal source, which is the key to achieving nanoscale curved growth of thin films. Metal clusters with a diameter of 2 nm are successfully prepared on different substrates by electron beam evaporation process. The mass of the chalcogen source close to the substrate is 200g~400g, the length of the alumina boat is 15cm, and the chalcogen source is flattened in the alumina boat to ensure that each temperature zone has a continuous supply of chalcogen sources. The mass of the chalcogen source far away from the substrate is 500g. When the reaction temperature is reached, the chalcogen source reacts with the metal source along with the carrier gas. Because the mass of the chalcogen source is much greater than that of the metal source, that is, the vapor pressure ratio of the metal source to the non-metal source reaches saturation during the reaction. As long as the non-metal source is ensured to be continuously supplied in each temperature zone and the non-metal source is excessive, a two-dimensional material with a curved edge can be obtained. By reducing the mass of the chalcogen source and the flattening length, the vapor pressure of the non-metal source is controlled, thereby regulating the edge curvature of the film.

[0042] The present invention uses 500°C for reaction to achieve the integrity of the film, prevent the formation of holes or precious metal nanoparticles, and uses a heating rate of 5°C / min to ensure the single crystal properties of the film. In addition, the film can be pushed and spread laterally, and hydrogen is an indispensable key condition.

[0043] Application of a heteroepitaxial single crystal metal sulfide compound film: The heteroepitaxial single crystal metal sulfide compound film catalyst is used as a cathode in electrochemical water splitting to produce hydrogen.

[0044] Example 1 Figure 1 As shown, a heteroepitaxial single-crystalline transition metal chalcogenide wafer-level PtSe2 thin film is prepared: a Pt thin film is first deposited on a substrate, and then selenized using a CVD method, and then naturally cooled to obtain a single-crystalline PtSe2 thin film. The specific process is as follows: (1) Using electron beam evaporation, 0.08 nm~0.18 nm Pt films were deposited on a single-layer MoS2 substrate grown on a 2-inch SiO2 / Si substrate at a rate of 0.01 Å / s.

[0045] ⑵Put the selenium powder in two alumina boats, one alumina boat is 15cm long and holds 200~400g of selenium powder, and the other alumina boat is 5cm long and holds 500g of selenium powder. Place the long alumina boat 2cm upstream from the center of the tube furnace, and the short alumina boat 25cm upstream from the center of the tube furnace. The sample with deposited Pt film is placed in the center of the tube furnace. The carrier gas is a mixture of argon and hydrogen, with an argon gas flow rate of 60 sccm and a hydrogen gas flow rate of 10 sccm. There is no need to evacuate the tube furnace cavity with a mechanical pump before heating. Expel the air in the tube by passing the mixed gas for 10 minutes at room temperature, then heat up to 500°C for 90 minutes and keep warm for 10 minutes. Finally, the tube furnace is cooled naturally to obtain a single crystal PtSe2 film.

[0046] Comparative Example 1 Preparation of a Pt thin film: A Pt thin film was deposited on a substrate. The specific process was the same as step (1) of Example 1.

[0047] The performance tests were conducted on the heteroepitaxial single crystal metal chalcogenide wafer-level PtSe2 thin film of Example 1 and the Pt thin film of Comparative Example 1:

Basic performance characterization

[0048] Tested by transmission electron microscopy, Figure 3 As shown, the heteroepitaxial single-crystalline metal chalcogenide wafer-level PtSe2 film has a uniform and continuous atomic-level structure.

[0049] After the condenser spherical aberration test, such as Figure 4 As shown, epitaxy with different Pt amounts shows that the film grows in the form of droplet-driven growth, extending in an earthworm-like manner with different curvatures, and eventually covers the entire first layer.

[0050] Selected area electron diffraction, such as Figure 5 As shown in the figure, the heteroepitaxial PtSe2 film has single crystal characteristics. The outer circle of diffraction spots is MoS2, and the inner circle is epitaxial PtSe2.

[0051] After Raman spectrometer testing, Figure 6 As shown in the figure, the peak positions of the films epitaxially grown with different Pt contents have different degrees of red shift. 1g Mode relative to E g The peak intensity of the mode increases significantly with increasing film thickness, which is attributed to the increased amount of Pt, which enhances the out-of-plane interactions.

[0052] The photoluminescence spectrum test showed that Figure 7 As shown, the annihilation of the 600-700 nm peak proves the formation of the heterostructure.

[0053]

Micro-nano electrochemical device hydrogen production performance test

[0054] High-precision electrochemical platform testing, such as Fig. 9 As shown, the performance of single-crystalline PtSe2 films with different Pt amounts is different, and the electrochemical performance is basically consistent with the curvature trend and the perimeter-to-area ratio trend, which proves that the catalytic performance can be improved by adjusting the curvature.

Claims

1. A heteroepitaxial single crystal metal chalcogenide thin film, characterized in that: The chemical formula of the film is MX2, wherein: M is any one of metal platinum, palladium, molybdenum, and tungsten; and X is any one of sulfur, selenium, and tellurium in the chalcogenide elements.

2. The heteroepitaxial single crystal metal chalcogenide thin film according to claim 1, characterized in that: The film is a wafer-level single crystal structure. The thickness of the single-layer film is ~0.9 nm, the thickness of the double-layer film is ~2.3 nm, the diameter is 1 inch, and the epitaxial growth method is droplet-driven growth.

3. A method for preparing a heteroepitaxial single crystal metal chalcogenide thin film according to claim 1 or 2, comprising the following steps: (1) On a growth substrate, a metal is deposited by a thin film deposition technique to form a metal layer with a final thickness of 0.08 nm to 0.18 nm; the metal is any one of platinum, palladium, molybdenum, and tungsten; (2) Place the chalcogenide source in two alumina boats, and the growth substrate on which the metal is deposited in a quartz boat. The three are placed in a tubular container in sequence along the direction of the gas flow, and the distance between the chalcogenide source close to the growth substrate and the growth substrate is 2-5 cm, and the distance between the chalcogenide source far from the growth substrate and the growth substrate is 20-25 cm. The growth substrate on which the metal layer is deposited is placed in the center of the tubular furnace. Pass the carrier gas, first raise the temperature to 500°C at 5°C / min at room temperature, then keep it at 500°C for 10 minutes for growth, and finally cool it naturally with the furnace to obtain a wafer-level heteroepitaxial single crystal metal chalcogenide compound film.

4. The method for preparing a heteroepitaxial single crystal metal chalcogenide thin film according to claim 3, characterized in that: The growth substrate in step (1) refers to any one of SiO2 / Si, BN, mica, sapphire, MoS2, and MoSe2 substrates, and its size is 2 inches; among which the BN, MoS2, and MoSe2 substrates are single layers.

5. The method for preparing a heteroepitaxial single crystal metal chalcogenide thin film according to claim 3, characterized in that: The thin film deposition technology in step (1) refers to electron beam evaporation, and its deposition rate is 0.01 Å / s.

6. The method for preparing a heteroepitaxial single crystal metal chalcogenide thin film according to claim 3, characterized in that: In step (2), the two alumina boats are of different lengths, wherein the long alumina boat is close to the growth substrate, and the short alumina boat is far away from the growth substrate.

7. The method for preparing a heteroepitaxial single crystal metal chalcogenide thin film according to claim 6, characterized in that: The mass ratio of the chalcogenide source placed in the long alumina boat to the chalcogenide source placed in the short alumina boat is 2-4:

5.

8. The method for preparing a heteroepitaxial single crystal metal chalcogenide thin film according to claim 3, characterized in that: The tubular container in step (2) refers to a tubular furnace with a heating device in the center.

9. The method for preparing a heteroepitaxial single crystal metal chalcogenide thin film according to claim 3, characterized in that: The carrier gas in step (2) is a mixed gas consisting of argon with a flow rate of 60 sccm and hydrogen with a flow rate of 10 sccm.

10. The use of a heteroepitaxial single crystal metal chalcogenide thin film as claimed in claim 1 or 2, characterized in that: The heteroepitaxial single-crystalline metal chalcogenide thin film catalyst is used as the cathode in electrochemical water splitting to produce hydrogen.

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