Two-dimensional metal semiconductor vertical heterojunction NbS2 / MoS2, and preparation method and application thereof

Abstract

The application discloses a two-dimensional metal semiconductor vertical heterojunction NbS2 / MoS2 and a preparation method and application thereof, and the method comprises the following steps: taking a sapphire as a substrate by sequentially spin-coating NaCl aqueous solution and NbCl5 isopropyl alcohol solution, introducing H2S gas and an inert gas flow carrying a Mo gaseous precursor into a reaction cavity at 850 DEG C, introducing H2 at the same time, and epitaxially growing a single-layer MoS2 triangle domain on the substrate; the temperature of the reaction cavity is increased to above 980 DEG C, H2S and an inert gas flow carrying a Nb gaseous precursor are introduced, NbS2 is grown on the single-layer MoS2 triangle domain, and the NbS2 / MoS2 vertical heterojunction is formed. The application realizes selective vertical epitaxial growth of NbS2 on the MoS2 triangle domain, constructs the NbS2 / MoS2 vertical heterojunction with an atom-level sharp interface and a highly consistent crystal lattice orientation, and has a wide application prospect in the fields of photoelectric devices, electronic devices and sensors.

Description

Technical Field

[0001] This invention belongs to the field of heterojunction materials technology, specifically relating to a two-dimensional metal-semiconductor vertical heterojunction NbS2 / MoS2, its preparation method, and its application. Background Technology

[0002] Transition metal chalcogenides (TMDCs) are typically composed of transition metal elements M (such as molybdenum, tungsten, niobium, rhenium, titanium, etc.) and chalcogen elements X (such as sulfur, selenium, tellurium, etc.). For example, MoS2 is considered a highly promising channel material in the post-Mohs era due to its atomically thin thickness, suitable band gap and high carrier mobility.

[0003] While MoS2 has demonstrated numerous advantages as a channel material, pure MoS2 devices generally suffer from high contact resistance and low current injection efficiency. Integrating MoS2 with metallic TMDCs (such as NbS2) to construct van der Waals vertical heterojunctions is an effective way to reduce contact resistance and improve device performance.

[0004] Currently, the fabrication of heterojunctions often employs mechanical transfer methods, which are prone to introducing interface contamination and damage, leading to unstable device performance and difficulty in large-scale scaling. Chemical vapor deposition (CVD) and its derivative technologies (such as MOCVD) can achieve large-area, high-quality direct growth of two-dimensional materials, but how to precisely control the selective vertical epitaxy of the second material (such as NbS2) on the first material (such as MoS2), rather than lateral splicing on the substrate, remains a significant challenge.

[0005] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a two-dimensional metal-semiconductor vertical heterojunction NbS2 / MoS2, its preparation method, and its application. This invention solves the problem that existing methods are difficult to control the selective vertical epitaxial growth of NbS2 on MoS2. This invention achieves the selective vertical epitaxial growth of NbS2 on the triangular domains of MoS2, thereby constructing an NbS2 / MoS2 vertical heterojunction with atomically sharp interfaces and highly consistent lattice orientation.

[0007] To achieve the above objectives, this invention provides a method for preparing a two-dimensional metal-semiconductor vertical heterojunction NbS2 / MoS2. The method includes: using a sapphire substrate sequentially spin-coated with an aqueous NaCl solution and an isopropanol solution of NbCl5; introducing H2S gas and an inert gas stream carrying a gaseous Mo precursor into a reaction chamber at 850°C, while simultaneously introducing H2 to suppress carbon residue; epitaxially growing a monolayer of MoS2 triangular domains on the substrate; rapidly raising the temperature of the reaction chamber to above 980°C; introducing H2S and the inert gas stream carrying the Nb gaseous precursor, causing H2S to react with Nb2(OC2H5). 10 A reaction occurs, and NbS2 is selectively grown in the central region of the monolayer MoS2 triangular domains to form an NbS2 / MoS2 vertical heterojunction. After growth is complete, the sample is cooled to room temperature under a protective atmosphere.

[0008] Preferably, the Mo gaseous precursor is selected from Mo(CO)6; or / and the Nb gaseous precursor is selected from Nb2(OC2H5). 10 ; or / and, the substrate is selected from C-plane sapphire substrates.

[0009] Preferably, the gaseous Mo precursor is transported to the reaction chamber at 20-25 °C through a Mo(CO)6 bubbler under the action of 8-10 sccm Ar carrier gas; the growth of the monolayer MoS2 triangular domains uses an H2S flow rate of 4-6 sccm; the growth time of the monolayer MoS2 triangular domains is 8-12 minutes.

[0010] Preferably, the Nb gaseous precursor is obtained by passing Nb2(OC2H5) at 20~25°C. 10 The bubbler delivers the NbS2 to the reaction chamber under the action of Ar carrier gas at 10~15 sccm; the NbS2 growth uses an H2S flow rate of 30~40 sccm; the NbS2 growth time is 25~35 minutes.

[0011] Preferably, before the MoS2 growth, the substrate is pretreated by annealing it in air at 1000°C for 6 hours, followed by spin-coating NaCl aqueous solution and NbCl5 isopropanol solution sequentially, and then loading it into a quartz reaction chamber; or / and, the concentration of the NaCl aqueous solution is 0.3 mol / L, and the concentration of the NbCl5 isopropanol solution is 0.1~0.125 mol / L.

[0012] Preferably, before the MoS2 growth, the system is thoroughly purged with inert gas to remove oxygen and moisture, and the bubbler containing Mo(CO)6 is kept at 20~25°C.

[0013] A second objective of the present invention is to provide a two-dimensional metal-semiconductor vertical heterojunction NbS2 / MoS2 obtained by the aforementioned preparation method, wherein the two-dimensional metal-semiconductor vertical heterojunction NbS2 / MoS2 has an atomically sharp interface, and the lattice orientations of MoS2 and NbS2 are consistent, with an included angle Δθ < 1°.

[0014] A third objective of this invention is to provide the application of the aforementioned NbS2 / MoS2 vertical heterojunction in the fabrication of electronic devices, wherein the electronic devices are field-effect transistors.

[0015] Preferably, the vertical heterojunction is used as the channel material of the transistor.

[0016] The two-dimensional metal-semiconductor vertical heterojunction NbS2 / MoS2 of the present invention, its preparation method, and its application solve the problem of the difficulty in selectively controlling the vertical epitaxial growth of NbS2 on MoS2 using existing methods, and has the following advantages: (1) This invention utilizes high temperature (≥980℃) as a thermodynamic switch to drive the vertical stacking mode, and gas phase precursor conversion to promote high-quality heterojunction growth. NbS2 is selectively vertically epitaxially grown on MoS2, overcoming the competitive growth of lateral splicing. The heterojunction structure is clear, and NbS2 / MoS2 vertical heterojunction with atomic-level sharp interface and high crystal quality is obtained, which can be applied to high-performance electronic devices. (2) The present invention adopts in-situ sequential growth, which avoids interface contamination caused by the transfer process. The atomic structure of the heterojunction interface is clear and sharp, and the lattice orientation is highly consistent (Δθ < 1°). The interface quality is high, which is conducive to efficient carrier transport. (3) This invention uses Mo(CO)6, H2S and Nb2(OC2H5) 10 As a gaseous precursor, and precisely controlled by a gas mass flow meter, the reaction can be precisely regulated. (4) The field-effect transistors fabricated based on the vertical heterojunction of the present invention have a significantly improved on-off ratio (40%) compared to a single MoS2 device, demonstrating their advantages in electronic devices. (5) The MOCVD process used in this invention is compatible with existing semiconductor manufacturing platforms and has the potential to develop towards large-area, large-scale preparation. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the growth process of the two-dimensional metal-semiconductor vertical heterojunction NbS2 / MoS2 of the present invention; (a) growth of MoS2 triangular domains; (b) nucleation of NbS2 at the center of MoS2; (c) completion of vertical epitaxial growth of NbS2; (d) schematic diagram of MOCVD system.

[0018] Figure 2The following are material characterization diagrams of the NbS2 / MoS2 vertical heterojunction prepared in Example 1 of this invention: (a) Optical microscope image; (b) Atomic force microscope image and height map; (c) Raman spectrum; (d-f) Scanning transmission electron microscope images.

[0019] Figure 3 The following are electrical performance diagrams of the heterojunction field-effect transistors prepared based on Embodiment 1 of the present invention: (a) schematic diagram of electrical testing; (b) physical test diagram; (c) comparison of the transfer characteristic curves of MoS2 and NbS2 / MoS2 vertical heterojunctions. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0021] It should be noted that: for conditions not specifically specified in the examples, standard conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0022] In this invention, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are used only for simplicity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0023] The features mentioned in this invention can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification, provided that there is no contradiction in the combination of these features. Each feature disclosed in the specification can be replaced by any alternative feature that provides the same, equivalent, or similar purpose. Therefore, unless otherwise specified, the disclosed features are merely general examples of equivalent or similar features.

[0024] In the description of this invention, it should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover a 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 a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0025] This invention provides a two-dimensional metal-semiconductor vertical heterojunction NbS2 / MoS2, its preparation method, and its applications, such as... Figure 1 As shown, the core of this method lies in utilizing high temperature (≥980℃) as a thermodynamic switch. Classical nucleation theory analysis demonstrates that under high-temperature conditions, the energy barrier for NbS2 nucleation on the MoS2 surface is significantly lower than that on the sapphire substrate, thus driving the dominance of the vertical stacking mode and achieving selective vertical epitaxial growth of NbS2 on MoS2. Specifically, firstly, NaCl and NbCl5 are spin-coated onto the sapphire substrate as nucleation regulators and niobium sources. Then, during the MoS2 growth stage, by controlling the reaction temperature to 850℃ and precisely introducing H2S gas and an inert gas stream carrying the gaseous Mo precursor Mo(CO)6, while simultaneously introducing H2 to suppress carbon residue, a monolayer of MoS2 triangular domains is successfully epitaxially grown on the substrate. Subsequently, during the NbS2 growth stage, the reaction chamber temperature is increased to above 980℃, and H2S and the Nb gaseous precursor Nb2(OC2H5) are introduced. 10 An inert gas flow is used, utilizing pre-coated NbCl5 and gas-phase transported Nb2(OC2H5). 10 As a niobium source, it reacts with H2S to perform vertical epitaxial growth of NbS2 on monolayer MoS2 triangular domains, ultimately forming NbS2 with atomically sharp interfaces. 2 / MoS2 vertical heterojunction. This innovative method not only overcomes the interface contamination and damage problems caused by traditional mechanical transfer methods, but also ensures high quality of the heterojunction interface through in-situ sequential growth, providing strong support for the application of high-performance electronic devices.

[0026] The following examples provide a detailed description of the two-dimensional metal-semiconductor vertical heterojunction NbS2 / MoS2 provided by the present invention, its preparation method, and its applications.

[0027] Example 1; A two-dimensional metal-semiconductor vertical heterojunction NbS2 / MoS2, the preparation method of which includes: (1) Substrate pretreatment A 2-inch C-side sapphire substrate was annealed in air at 1000°C for 6 hours. Subsequently, a 0.3 mol / L NaCl aqueous solution and a 0.125 mol / L NbCl5 isopropanol solution (solute: NbCl5, solvent: isopropanol, concentration: 0.125 mol / L) were spin-coated sequentially, and then the substrate was placed into a quartz reaction chamber. (2) System preparation Using an MOCVD system, the reactor was thoroughly purged with Ar gas before the reaction to remove oxygen and moisture. The bubbler containing Mo(CO)6 was kept at 20°C. (3) MoS2 growth The reaction chamber temperature was raised to 850℃, 5 sccm H2S was introduced, and the Mo precursor was transported in the gas phase by passing it through a Mo(CO)6 bubbler at 20℃ and purging with 8~10 sccm Ar carrier gas. At the same time, 4 sccm H2 was introduced to suppress carbon residue. The growth lasted for 10 minutes to obtain a triangular MoS2 monolayer. (4) NbS2 growth The reaction chamber temperature was raised to 980℃, 35 sccm of H2S was introduced, and Nb2(OC2H5) at 25℃ was passed through. 10 A bubbler, under Ar carrier gas purging at 10~25 sccm, enables the gas-phase transport of Nb precursors, allowing H2S to react with the gas-phase transported Nb2 (OC2H5). 10 The reaction occurs with the Nb source on the substrate, and the growth lasts for 30 minutes.

[0028] (5) Post-processing After growth, the heat source was turned off, and the sample was allowed to cool naturally to room temperature in an atmosphere of 5 sccm H2S and 200 sccm Ar.

[0029] like Figure 2 The figures shown are material characterization diagrams of the NbS2 / MoS2 vertical heterojunction prepared in Example 1 of this invention; (a) optical microscope image; (b) atomic force microscope image and height diagram; (c) Raman spectrum; (d-f) scanning transmission electron microscope images. Figure 2 It can be seen that, Figure 2 (a) shows that Area 1 has a hexagonal shape with a side length of about 18 micrometers (NbS2) and Area 2 has a triangular shape with a side length of about 45 micrometers (MoS2). Figure 2 (b) reveals a clear interface, and Area 1 is raised relative to Area 2, suggesting the formation of a vertical heterostructure; Figure 2 (c) shows that the Raman spectrum of Area 2 has a characteristic peak of MoS2 (E1²g≈385 cm⁻¹, A1²g≈405 cm⁻¹, Δ≈20 cm⁻¹), while Area 1 has a characteristic peak of NbS2 (E1≈335 cm⁻¹, A1≈379 cm⁻¹). The peak overlap phenomenon (showing three peaks instead of four peaks) further supports the vertical heterostructure. Figure 2 The (d~f) values ​​show the contrast difference between the two regions (the dark region is MoS2 and the bright region is NbS2), the interface is defect-free, and the lattice orientation is highly consistent (Δθ < 1°).

[0030] The heterojunction prepared in Example 1 was used to fabricate a field-effect transistor. From bottom to top, the structure consisted of a silicon substrate (as the gate electrode), a SiO2 layer (as the dielectric layer), and the heterojunction of the present invention (as the channel layer). Source / drain electrodes (Ti / Au) were disposed on both sides of the heterojunction, with a length of 80 nm. A pure MoS2 device was fabricated on the substrate using the same method as steps (1) to (3) in Example 1, with only a triangular MoS2 monolayer as the channel layer. This device was then compared with the field-effect transistor fabricated using the heterojunction of Example 1.

[0031] The electrical performance of the devices prepared in Example 1 and Comparative Example 1 was tested at 300K / room temperature for 10 hours. -6 Tested under Pa vacuum conditions, results are shown below. Figure 3 .

[0032] like Figure 3 As shown, the on / off ratio of the fabricated field-effect transistor is 1.4 times that of the pure MoS2 device, which is a 40% performance improvement.

[0033] In summary, this invention, through a unique temperature control and in-situ sequential growth strategy, successfully achieved selective vertical epitaxial growth of NbS2 on MoS2, constructing an NbS2 / MoS2 vertical heterojunction with an atomically sharp interface and highly consistent lattice orientation. This effectively overcomes the interface contamination and damage problems caused by traditional mechanical transfer methods, while avoiding competitive growth of lateral splicing, ensuring the high quality and definition of the heterojunction structure, and providing a reliable material basis for the fabrication of high-performance electronic devices.

[0034] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for preparing a two-dimensional metal-semiconductor vertical heterojunction NbS2 / MoS2, characterized in that, The preparation method includes: Using sapphire substrates sequentially spin-coated with NaCl aqueous solution and NbCl5 isopropanol solution, H2S gas and an inert gas stream carrying Mo gaseous precursor were introduced into the reaction chamber at 850°C, while H2 was introduced to suppress carbon residue, and a monolayer of MoS2 triangular domains was epitaxially grown on the substrate. The temperature of the reaction chamber is rapidly raised to over 980°C, and H2S and an inert gas stream carrying the Nb gaseous precursor are introduced, causing the H2S to react with Nb2(OC2H5). 10 A reaction occurs, in which NbS2 is grown by selectively forming nuclei in the central region of the monolayer MoS2 triangular domains, thus forming an NbS2 / MoS2 vertical heterojunction. After growth is complete, the sample is cooled to room temperature under a protective atmosphere.

2. The preparation method according to claim 1, characterized in that, The Mo gaseous precursor is selected from Mo(CO)6; Or / and, the Nb gaseous precursor is selected from Nb2(OC2H5). 10 ; Or / and, the substrate is selected from C-plane sapphire substrates.

3. The preparation method according to claim 2, characterized in that, The gaseous Mo precursor is transported to the reaction chamber through a Mo(CO)6 bubbler at 20-25 °C under the action of 8-10 sccm Ar carrier gas. The growth of the monolayer MoS2 triangular domains was carried out using an H2S flow rate of 4~6 sccm. The growth time for the single-layer MoS2 triangular domains is 8-12 minutes.

4. The preparation method according to claim 2, characterized in that, The Nb gaseous precursor is obtained by passing Nb2(OC2H5) at 20~25℃. 10 The bubbler delivers the gas to the reaction chamber under the action of 10~15 sccm Ar carrier gas; The NbS2 growth was performed using an H2S flow rate of 30-40 sccm. The NbS2 growth time is 25-35 minutes.

5. The preparation method according to claim 1, characterized in that, Before the growth of MoS2, the substrate was pretreated: the substrate was annealed in air at 1000°C for 6 hours, and then NaCl aqueous solution and NbCl5 isopropanol solution were spin-coated in sequence and placed into a quartz reaction chamber. Or / and, the concentration of the NaCl aqueous solution is 0.3 mol / L, and the concentration of the NbCl5 isopropanol solution is 0.1~0.125 mol / L.

6. The preparation method according to any one of claims 1 to 5, characterized in that, Before the growth of MoS2, the system is thoroughly purged with inert gas to remove oxygen and water vapor, and the bubbler containing Mo(CO)6 is kept at 20~25°C.

7. A two-dimensional metal-semiconductor vertical heterojunction NbS2 / MoS2 obtained by the preparation method according to any one of claims 1 to 6, characterized in that, The two-dimensional metal-semiconductor vertical heterojunction NbS2 / MoS2 has an atomically sharp interface, and the lattice orientations of MoS2 and NbS2 are consistent, with an included angle Δθ < 1°.

8. The application of the NbS2 / MoS2 vertical heterojunction as described in claim 7 in the fabrication of electronic devices, characterized in that, The electronic device is a field-effect transistor.

9. The application according to claim 8, characterized in that, The vertical heterojunction is used as the channel material for the transistor.

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