Two-dimensional semiconductor in-plane integration method and device

Abstract

The invention discloses a two-dimensional semiconductor in-plane integration method and device, and the method comprises the steps: providing a first two-dimensional single-layer material, and placing the first two-dimensional single-layer material on a target substrate; partially stacking the second two-dimensional single-layer material on the first two-dimensional single-layer material to form a Van der Waals heterojunction comprising a stacking region and a single-layer region; an excitation light source of which the photon energy is greater than the luminous band gap of the first two-dimensional single-layer material and / or the second two-dimensional single-layer material is utilized, so that the van der Waals heterojunction is subjected to selective photochemical reaction, and the second two-dimensional single-layer material in the stacking region is removed through selective reaction; and the first two-dimensional single-layer material and the second two-dimensional single-layer material are integrated and spliced in the same plane. According to the two-dimensional semiconductor in-plane integration method and the two-dimensional semiconductor in-plane integration device provided by the invention, the upper-layer material in the stacking region is selectively removed by utilizing the electronic state distribution difference of different two-dimensional materials in the stacking region and the single-layer region in combination with the photochemical reaction, so that the in-plane splicing of the two-dimensional materials is realized.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor technology, and specifically relates to a two-dimensional semiconductor in-plane integration method and device. Background Art

[0002] Existing in-plane heterojunction preparation technologies usually rely on traditional single-step or multi-step growth methods, including chemical vapor deposition (CVD), atomic layer deposition (ALD), physical vapor deposition (PVD), electrochemical deposition, hydrothermal synthesis and epitaxial growth. These methods have certain applications in the preparation of two-dimensional materials and heterojunctions, but they face some technical bottlenecks. These growth methods usually rely on the crystal plane structure of the substrate, resulting in the inability to obtain patterned heterojunction arrays during the synthesis process. Due to the random nucleation problem, the growth of heterojunctions cannot be precisely controlled at the microscale.

[0003] Moreover, these processes often need to be carried out at extremely high temperatures, usually between 600°C and 1200°C. Such high temperatures place extremely high demands on the preparation process, especially in terms of compatibility with the integrated circuit process of the current semiconductor industry.

[0004] In order to solve the above-mentioned random nucleation problem, the prior art also attempts to prepare heterojunction arrays by combining material growth with modern micro-nano processing technology. Common micro-nano processing methods include electron beam etching, photolithography, laser ablation, etc., through which the patterning of the heterojunction area can be achieved. However, although these technologies can partially solve the patterning problem, in actual operation, there are still limitations in material design freedom, processing accuracy, and the need for a high temperature environment.

[0005] Therefore, it is necessary to provide a new solution to the above technical problems. Summary of the invention

[0006] The purpose of the present invention is to provide a two-dimensional semiconductor in-plane integration method and device, which can realize the construction of in-plane heterojunction at room temperature, has high material design freedom and processing accuracy, simple preparation process, and can realize low-cost integration.

[0007] To achieve the above purpose, the technical solution provided by the present invention is as follows:

[0008] In a first aspect, the present invention provides a two-dimensional semiconductor in-plane integration method, comprising: providing a first two-dimensional monolayer material and placing it on a target substrate; partially stacking a second two-dimensional monolayer material on the first two-dimensional monolayer material to form a van der Waals heterojunction including a stacking region and a monolayer region; using an excitation light source whose photon energy is greater than the luminescence band gap of the first two-dimensional monolayer material and / or the second two-dimensional monolayer material to cause the van der Waals heterojunction to undergo a selective photochemical reaction, so that the second two-dimensional monolayer material in the stacking region is selectively reacted and removed, so as to integrate and splice the first two-dimensional monolayer material and the second two-dimensional monolayer material in the same plane.

[0009] In one or more embodiments, the first two-dimensional single-layer material is made of molybdenum sulfide, tungsten sulfide, molybdenum selenide or tungsten selenide; and / or the second two-dimensional single-layer material is made of molybdenum sulfide, tungsten sulfide, molybdenum selenide or tungsten selenide.

[0010] In one or more embodiments, the target substrate is a gold substrate, a SiO2 / Si substrate, a sapphire substrate, a quartz substrate, a boron nitride substrate or a graphene substrate.

[0011] In one or more embodiments, a first two-dimensional monolayer material is obtained on a target substrate by physical vapor deposition, chemical vapor deposition or stripping; and / or a second two-dimensional monolayer material is obtained by physical vapor deposition, chemical vapor deposition or stripping, and a flexible polymer is used as an auxiliary substrate to transfer the second two-dimensional monolayer material to the first two-dimensional monolayer material, so that the second two-dimensional monolayer material is partially stacked on the first two-dimensional monolayer material to form a van der Waals heterojunction.

[0012] In one or more embodiments, the two-dimensional semiconductor in-plane integration method further includes: regulating the interlayer spacing between the first two-dimensional monolayer material and the second two-dimensional monolayer material to enhance the photochemical reaction activity of the second two-dimensional monolayer material in the stacking area.

[0013] In one or more embodiments, the reaction medium of the selected area photochemical reaction is a neutral or acidic aqueous solution.

[0014] In one or more embodiments, under the action of an excitation light source, photogenerated electrons in the second two-dimensional single-layer material of the stacked region are transferred to the first two-dimensional single-layer material, so that the second two-dimensional single-layer material of the stacked region accumulates photogenerated holes.

[0015] In one or more embodiments, before stacking the second two-dimensional single-layer material, the first two-dimensional single-layer material is patterned.

[0016] In a second aspect, the present invention provides a semiconductor device comprising a two-dimensional in-plane splicing material produced by the two-dimensional semiconductor in-plane integration method as described above.

[0017] Compared with the prior art, the two-dimensional semiconductor in-plane integration method and device provided by the present invention realizes the in-plane splicing of two-dimensional materials by utilizing the difference in electronic state distribution of different two-dimensional materials in the stacking area and the single-layer area, combined with photochemical reaction to selectively remove the upper material in the stacking area; the whole process can be carried out at room temperature, avoiding the limitations of high-temperature process; at the same time, by precisely controlling the photochemical reaction area, high-precision heterojunction patterning can be directly achieved, thus eliminating the need for additional micro-nano processing steps. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 A flow chart of a two-dimensional semiconductor in-plane integration method according to an embodiment of the present invention;

[0020] Figure 2 Schematic diagram of constructing WS2-MoS2 in-plane heterojunction by selective photohydrolysis in one embodiment of the present invention;

[0021] Figure 3 Schematic diagram of an in-situ photochemical reaction device in one embodiment of the present invention;

[0022] Figure 4 This is an optical image of the WS2 / MoS2 van der Waals heterojunction sample prepared in Example 1 of the present invention;

[0023] Figure 5 This is an optical image of the WS2-MoS2 in-plane heterojunction sample prepared in Example 1 of the present invention;

[0024] Figure 6 This is a Raman image of the WS2-MoS2 in-plane heterojunction sample prepared in Example 1 of the present invention;

[0025] Figure 7 The fluorescence images at various moments during the photohydrolysis reaction in Example 1 of the present invention;

[0026] Figure 8 1 is a kinetic curve analysis diagram of the photohydrolysis reaction process in Example 1 of the present invention;

[0027] Fig. 9 Optical images of the sample before and after photohydrolysis during the preparation of the WSe2-WS2 in-plane heterojunction in Example 2 of the present invention;

[0028] Fig.10 Optical images of the sample before and after photohydrolysis during the preparation of the WSe2-MoSe2 in-plane heterojunction in Example 2 of the present invention;

[0029] Fig.11 Optical images of the sample before and after photohydrolysis during the preparation of the WSe2-MoS2 in-plane heterojunction in Example 2 of the present invention;

[0030] Fig.12 The optical image and Raman imaging diagram of the WSe2-WS2-MoS2 in-plane heterojunction sample prepared in Example 3 of the present invention;

[0031] Fig.13 The surface potential difference (CPD) image and tip-enhanced Raman imaging image of the one-dimensional nanoscale MoS2-WS2NR-MoS2 in-plane superlattice sample prepared in Example 4 of the present invention;

[0032] Fig.14 This is a Raman image of the micron-scale WS2-MoS2 in-plane heterojunction array prepared in Example 5 of the present invention;

[0033] Fig.15 The optical images and fluorescence images of the sample before and after photohydrolysis during the preparation of the WS2-MoS2 in-plane heterojunction in Example 6 of the present invention;

[0034] Fig.16 The optical image and fluorescence image of the sample before and after photohydrolysis during the preparation of the WS2-MoS2 in-plane heterojunction in Example 7 of the present invention;

[0035] Fig.17 This is a test diagram of the electrical performance of the in-plane heterojunction electrical device prepared in Example 7 of the present invention. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0037] It should be noted that, unless otherwise indicated, all numbers used in the specification and claims to represent feature sizes, quantities and physical properties should be understood to be modified by the term "about" in all cases. Therefore, unless otherwise indicated, the numerical parameters listed in the above specification and the attached claims are approximate values, and those skilled in the art can use the teachings disclosed herein to seek to obtain the desired properties and appropriately change these approximate values. The use of numerical ranges expressed as endpoints includes all numbers within the range and any range within the range, for example, 1 to 5 includes 1, 1.2, 1.4, 1.55, 2, 2.75, 3, 3.80, 4 and 5, etc.

[0038] The technology of the present invention is generated to solve the bottlenecks and limitations of the existing in-plane splicing technology of two-dimensional materials, and can be widely used in the preparation of two-dimensional in-plane heterojunctions. In the design and manufacture of nanomaterials and electronic devices, two-dimensional transition metal chalcogenides (TMDs) are an important material with excellent electrical and optical properties, which can meet the needs of the next generation of high-performance electronic and optoelectronic devices. In-plane heterojunctions, as a key material structure form, can produce new physical effects through interface interactions between different materials, and are widely used in high-performance optoelectronic devices and integrated circuits. However, existing heterojunction preparation methods usually rely on high-temperature processes, crystal plane restrictions, etc., and it is difficult to achieve flexible preparation under low temperature conditions, and are greatly restricted in terms of patterning, material selection, and angle freedom.

[0039] In the analysis of existing technologies, it can be found that most of the current heterojunction preparation technologies use chemical vapor deposition (CVD) or other vapor deposition methods, which usually need to be carried out at high temperatures of 600°C to 1200°C, limiting their compatibility with modern integrated circuit manufacturing processes. In addition, since these methods rely on the crystal plane structure of the substrate, the growth of the heterojunction is affected by the crystal phase of the substrate, and it is impossible to achieve an in-plane heterostructure with free corners.

[0040] Transition and metal dichalcogenide (TMD) belongs to a class of two-dimensional materials. The chemical formula is MX2, where M refers to transition metal elements (such as molybdenum, tungsten, niobium, rhenium, titanium), and X refers to chalcogen elements (such as sulfur, selenium, tellurium). A single layer of transition metal sulfide is a sandwich structure of XMX. The bulk TMD layers are connected by weak van der Waals forces, while the atoms in the plane are connected by strong covalent bonds, so TMD can be stripped into single-layer or multi-layer nanosheets. Many TMDs exhibit semiconductor properties, and the energy bands of their multilayer materials are indirect band gaps. When stripped into a single layer, the band structure is transformed into a direct band gap.

[0041] An in-plane heterojunction is a structure formed by seamless connection of two or more different materials on the same plane. This structure is different from the traditional vertically stacked van der Waals heterojunction because it involves direct chemical bonding between different materials in the same plane. In-plane heterojunctions are widely used in electronic devices, optical and optoelectronic applications, and quantum technology. The research and development of in-plane heterojunctions is a cutting-edge topic in the field of materials science and nanotechnology. It opens up new possibilities for material performance regulation and new device design by precisely controlling the combination and interface of materials.

[0042] Two-dimensional single-layer semiconductor materials represented by transition metal dichalcogenides (TMDs), such as WS2 (tungsten sulfide), WSe2 (tungsten selenide), MoS2 (molybdenum sulfide), MoSe2 (molybdenum selenide), etc., have important applications in thin film transistors, large-scale field effect transistors (FETs), flexible electronics, complementary metal oxide semiconductor (CMOS) logic, light emitters, photodetectors and light collection devices due to their adjustable band gap and excellent electrical and optical properties.

[0043] Compared with traditional silicon-based and germanium-based semiconductors, it can still maintain a high carrier mobility at the atomic level thickness (<1nm), making it one of the competitive and popular candidate channel materials in the post-Moore era. Assembling two or more TMD monolayers in the horizontal direction can form an in-plane heterojunction. In the heterojunction, the characteristics of each monolayer component itself can be maintained, and because the electrons of each monolayer component are exposed to the heterojunction interface and interact with each other, many novel exciton physics and optoelectronic synergistic effects are generated, making it have great application value and potential in new functional devices (such as photodetectors, light-emitting diodes, photovoltaic cells, artificial superlattice devices, valley electron transistors, etc.) and the integrated circuit industry.

[0044] Based on an in-depth analysis of the aforementioned fields, the present invention proposes a method for in-plane integration of two-dimensional semiconductors based on selective photochemical reactions (such as photohydrolysis). This method utilizes the difference in the electronic state distribution of different two-dimensional materials in the stacking area and the single-layer area, and combines photochemical reactions to selectively remove the upper layer of the stacking area, thereby achieving in-plane splicing of two-dimensional materials, which can be used for the construction of two-dimensional in-plane heterojunctions.

[0045] Moreover, the entire process can be carried out at room temperature, avoiding the limitations of high-temperature processes. At the same time, by precisely controlling the photochemical reaction area, high-precision heterojunction patterning can be directly achieved, eliminating the need for additional micro-nano processing steps. This method breaks through the limitations of existing technologies in temperature, material selection, and patterning, and can increase the freedom of material selection and torsion angle design, providing a gentle, flexible, and highly controllable technical means for the preparation of two-dimensional in-plane heterojunctions.

[0046] Please refer to Figure 1 FIG. 1 is a flow chart of a two-dimensional semiconductor in-plane integration method according to an embodiment of the present invention. The two-dimensional semiconductor in-plane integration method specifically comprises the following steps:

[0047] S101: providing a first two-dimensional single-layer material, and placing it on a target substrate.

[0048] It should be noted that in order to successfully place the two-dimensional material on the target substrate, an appropriate target substrate material can be selected. The choice of the target substrate affects the transfer effect and stability of the two-dimensional material. Optional substrate materials include gold substrate, SiO2 / Si substrate, sapphire substrate, quartz substrate, boron nitride substrate, graphene substrate, etc. These substrates have good flatness and chemical stability, and can provide good support for the two-dimensional material.

[0049] As a metal material with excellent conductivity, gold substrate can be used in the preparation of optoelectronic and electronic devices. Gold has good chemical inertness and excellent electrical properties, and can form a stable van der Waals heterojunction with a variety of two-dimensional materials. For example, in photodetectors or nanoelectronic devices, two-dimensional semiconductor materials such as MoS2 or WS2 can be stacked on a gold substrate to use the high conductivity of gold as an electrode material to ensure the efficient transmission performance of the device. At the same time, the optical properties of the gold substrate also give it advantages in optical applications, such as enhancing the light absorption or emission efficiency of two-dimensional materials.

[0050] SiO2 / Si substrate is the carrier of silicon-based integrated circuits. While providing good mechanical stability and chemical inertness, the SiO2 layer acts as an insulating layer to help control the electronic properties of the material. In the study of two-dimensional materials, SiO2 / Si substrates can be used to construct field effect transistors (FETs), isolating electrons through the SiO2 layer to form a current switching effect. For example, when preparing MoS2-based FET devices, after the MoS2 monolayer material is transferred to the SiO2 / Si substrate, the Si substrate can be used as a back gate electrode to achieve precise control of the electron transmission channel.

[0051] The graphene substrate is a structure based on the combination of a graphene layer and a copper, SiO2 / Si, quartz, or sapphire substrate. As a two-dimensional material, graphene's unique electrical conductivity and mechanical flexibility make it a popular candidate for the next generation of electronic devices. In the graphene substrate, the graphene layer can be grown on a substrate such as copper, SiO2 / Si, quartz, or sapphire by chemical vapor deposition (CVD). The lower substrate provides high thermal conductivity and a stable substrate structure, while the graphene layer can serve as a supporting layer for the two-dimensional material or as an electron transport layer. For example, when constructing high-performance optoelectronic devices, the graphene layer can be used as a transparent electrode or charge transport layer, using its excellent electrical conductivity and transparency to improve the photoelectric conversion efficiency of the device.

[0052] The material of the first two-dimensional single-layer material can be transition metal chalcogenides (TMD), such as molybdenum sulfide (MoS2), tungsten sulfide (WS2), molybdenum selenide (MoSe2) and tungsten selenide (WSe2). These materials are selected as two-dimensional single-layer materials mainly because their excellent properties match the composition of two-dimensional materials and can play an excellent role in different application scenarios.

[0053] MoS2 has good semiconductor properties. In the monolayer state, MoS2 exhibits direct bandgap characteristics, which enables it to exhibit efficient light absorption and emission capabilities in optoelectronic devices (such as photodetectors and light-emitting diodes). In addition, MoS2 has high electron mobility and excellent conductivity in field effect transistors (FETs). As the first two-dimensional monolayer material, MoS2 can provide a solid foundation for heterojunctions, and by stacking with a second layer of material, richer electronic and optical properties can be achieved.

[0054] As a material with a high band gap, WS2 not only has excellent photoelectric responsiveness, but also has high thermal stability and mechanical strength under extreme conditions. MoSe2 has a high photoelectric conversion efficiency, and its band gap can be adjusted by adjusting stress and the number of layers, so it is also widely used in flexible electronic devices. These materials, as the first two-dimensional single-layer materials, can form a van der Waals heterojunction by stacking with the second layer of materials.

[0055] WSe2 has direct bandgap characteristics and can form efficient heterojunctions with other TMD materials. Especially in photovoltaic devices and light-emitting devices, WSe2 can greatly improve the efficiency of devices due to its high carrier mobility and low surface recombination rate. In the construction of in-plane heterojunctions, when WSe2 is stacked with other materials such as MoS2 or WS2, it can optimize the optoelectronic performance, especially having a significant impact on exciton physics and charge transfer.

[0056] In an exemplary embodiment, a first two-dimensional single-layer material is provided and placed on a target substrate, and its implementation method specifically includes: obtaining the first two-dimensional single-layer material on the target substrate by physical vapor deposition, chemical vapor deposition or stripping.

[0057] For example, a flexible polymer can be used as an auxiliary substrate, and a mechanical peeling method can be used to obtain a first two-dimensional single-layer material. Combined with a two-dimensional material transfer platform, the first two-dimensional single-layer material can be transferred from the flexible polymer auxiliary substrate to the target substrate.

[0058] For example, polydimethylsiloxane (PDMS), a hydrophobic silicone material also known as dimethyl silicone oil, is often used to assist in transferring two-dimensional materials to other substrates because of its mechanical softness and stretchability, which allows it to come into contact with thin and fragile two-dimensional materials without causing damage.

[0059] The use of PDMS as an auxiliary substrate is mainly due to its mechanical flexibility and good elasticity. It can effectively make seamless contact with the two-dimensional material, avoiding the stress concentration problem of the hard substrate during the transfer process. When the two-dimensional material is mechanically peeled off, PDMS wraps the material through its flexibility and fully adheres to the surface of the material under the action of appropriate external force. This bonding method ensures that the material will not crack or break due to the mismatch between the substrates.

[0060] During mechanical exfoliation, the material is exfoliated by applying appropriate external forces. For example, in MoS2, the layers of the material are bonded by van der Waals forces, which allows them to be separated into a single layer or a few layers by mechanical exfoliation. During the operation, PDMS is first placed on the surface of the material, and the PDMS is adhered to the surface of the material by slight pressure, and then the PDMS is gently lifted by the mechanical exfoliation device, thereby taking away the two-dimensional material.

[0061] After the material is peeled off, the two-dimensional material is attached to the PDMS surface. In order to finally transfer it to the target substrate, a two-dimensional material transfer platform can be used. The design of the transfer platform combines precise temperature control and mechanical control to ensure that the material will not be physically disturbed too much during the transfer process.

[0062] During the transfer process, PDMS adheres to the target substrate. By adjusting the heating temperature of the platform (for example, it can be controlled at around 80°C) and maintaining it for a certain period of time (such as 10 minutes), the flexibility and adhesion of the PDMS material will change, allowing the two-dimensional material to be smoothly transferred from the PDMS surface to the target substrate. The temperature control in this process can ensure the stability of the two-dimensional material and keep the PDMS material in good elasticity, avoiding material damage.

[0063] S102: partially stacking a second two-dimensional single-layer material on the first two-dimensional single-layer material to form a van der Waals heterojunction including a stacking region and a single-layer region.

[0064] It should be noted that the second two-dimensional single layer material is different from the first two-dimensional single layer material, and the material can be a transition metal chalcogenide (TMD). The valence band top of the second two-dimensional single layer material is higher than the valence band top of the first two-dimensional single layer material.

[0065] A van der Waals heterojunction is a multilayer structure composed of different two-dimensional material layers combined by van der Waals forces. The characteristic of this structure is that there is no chemical bonding between the layers, and they only interact through van der Waals forces (i.e., weak attraction between molecules). This allows new material systems to be manufactured by precisely stacking two-dimensional materials of different properties to achieve or optimize electronic, optical and mechanical properties. The van der Waals heterojunction retains the inherent properties of each material and introduces unique electronic and optical behaviors at the interface. A van der Waals heterojunction includes a stacking region (heterojunction region) and a single-layer region. The stacking region described in the present invention refers to the region where the upper and lower layers of single-layer materials overlap, and the single-layer region refers to the region without overlap.

[0066] In a two-dimensional single-layer van der Waals heterojunction, since the two-dimensional monolayer has an atomic-level thickness, electrons are exposed on the surface and interact at the interface, which makes the electronic state distribution in the double-layer region and the single-layer region of the heterojunction different, and ultimately leads to different chemical activities. By regulating the interlayer distance between the two monolayer components, the photochemical reaction activity of the upper layer material in the heterojunction region can be made higher.

[0067] In an exemplary embodiment, physical vapor deposition, chemical vapor deposition or stripping method can be used to obtain the second two-dimensional monolayer material, and a flexible polymer can be used as an auxiliary substrate to transfer the second two-dimensional monolayer material to the first two-dimensional monolayer material, so that the second two-dimensional monolayer material is partially stacked on the first two-dimensional monolayer material to form a van der Waals heterojunction.

[0068] For example, PDMS can be used as an auxiliary substrate to extract the second two-dimensional monolayer material from the original substrate by mechanical stripping, and then stack it on the first layer of material through a two-dimensional material transfer platform. In this process, the second two-dimensional monolayer material in some areas overlaps with the first two-dimensional monolayer material to form a stacking area, while the rest remains as a single-layer area. This structural design allows the two materials to produce a heterojunction effect in the stacking area, while maintaining the individual characteristics of each material in the single-layer area.

[0069] In specific operations, the stacking position, area and angle of the two-dimensional materials can be adjusted according to the actual application requirements. By precisely aligning and controlling the size of the stacking area, different types of in-plane heterostructures can be constructed.

[0070] In an exemplary embodiment, during the transfer process, the interlayer spacing between the first two-dimensional monolayer material and the second two-dimensional monolayer material is regulated by the heating function of the two-dimensional material transfer platform to enhance the photochemical reaction activity of the second two-dimensional monolayer material in the stacking area.

[0071] The interlayer spacing between two-dimensional materials has an important influence on their electronic structure and physicochemical properties. In van der Waals heterojunctions, the van der Waals forces between materials are weak, so regulating the interlayer spacing can effectively affect the interlayer electronic interactions, especially in photochemical reactions, where the transfer behavior of interlayer electrons and holes is significantly affected by the change in spacing. By precisely controlling the interlayer spacing through a heating platform, the electronic state of the material can be optimized, thereby enhancing the photochemical reaction activity of the upper material in the stacking area.

[0072] In specific operations, when two-dimensional materials are stacked together to form a van der Waals heterojunction, the spacing between the materials is not fixed. This spacing can be precisely adjusted through the heating function of the two-dimensional material transfer platform. Usually, by raising the temperature to a moderate range (such as 80°C) through the heating platform, the thermal expansion of the material or the adjustment of the surface energy can be triggered, thereby changing the van der Waals force between the materials. This heating process does not destroy the layered structure of the material, but it will have a slight effect on the physical state of the material.

[0073] The use of a heating platform allows for fine-tuning of the material through gentle heat treatment without affecting the structural integrity of the material. This is different from traditional mechanical control methods, as thermal control can change the interlayer spacing more evenly and controllably, avoiding mechanical damage that may occur to the material during operation.

[0074] S103: Using an excitation light source whose photon energy is greater than the luminescence band gap of the first two-dimensional monolayer material or the second two-dimensional monolayer material, the van der Waals heterojunction undergoes a selective photochemical reaction, so that the second two-dimensional monolayer material in the stacking area is selectively reacted and removed, so as to integrate and splice the first two-dimensional monolayer material and the second two-dimensional monolayer material in the same plane.

[0075] In order to trigger a photochemical reaction, the photon energy of the selected light source must be greater than the emission band gap of at least one material in the stacked material. For example, for transition metal chalcogenides (TMDs) such as MoS2 or WS2, the band gap of a single layer of material is usually between 1.2 and 2.1 electron volts, so a light source with a wavelength of around 530nm can be used to excite electronic transitions in these materials. In this case, a power-adjustable laser or mercury lamp is usually used as the excitation light source. By precisely controlling the photon energy, it is possible to ensure that a photochemical reaction occurs only in the stacked area.

[0076] When the energy of the photon is greater than the luminescence band gap of the stacked material, the illumination will trigger the electron to jump from the valence band to the conduction band. At this time, the electrons will leave holes after jumping from the valence band, and the electrons will enter the conduction band and conduct in the material. The holes will remain in the valence band, and they can participate in oxidation reactions, so the distribution of holes is directly related to the photochemical reactivity of the material. In a single-layer material, holes accumulate locally in the valence band inside the material, but because there is no charge transfer process, the holes in the single-layer material are relatively stable and will not cause obvious photochemical reactions.

[0077] However, in the bilayer region, the situation is different. Stacked bilayer materials usually have different valence band structures, especially in heterojunctions, where the valence band top of the upper material is often higher than that of the lower material. Since holes tend to transfer to materials with higher valence band tops, the charge distribution in the bilayer region becomes asymmetric. Specifically, holes transfer from materials with lower valence bands (such as MoS2 in the lower layer) to materials with higher valence bands (such as WS2 in the upper layer). This transfer process significantly increases the hole density of the upper material, resulting in a significant increase in the photochemical reaction activity of the upper material, thereby initiating a photochemical reaction.

[0078] This hole accumulation effect is the key to the photochemical reaction in the double-layer region. In the stacked region, the hole density of the upper material is much higher than that of the lower material, so the chemical reactivity of the upper material is greatly enhanced. In the photochemical reaction, the holes react with the surrounding water molecules, causing the upper material to oxidize into water-soluble products (such as molybdic acid or tungstic acid), which are then hydrolyzed and removed from the surface of the material. In this way, the upper material in the stacked region is selectively removed, while the lower material remains intact.

[0079] Through this mechanism, the difference in the distribution of electronic states between the bilayer and monolayer regions makes the selected-area photochemical reaction highly selective. Specifically, only in the bilayer region will the upper material undergo a photochemical reaction due to the transfer and accumulation effect of holes. This reaction stops spontaneously at the material boundary, ensuring the precise boundary after the material is partially removed, thereby forming a heterojunction structure in the bilayer region, while other unstacked regions remain intact.

[0080] The selective photochemical reaction in the present invention is a self-terminating photochemical reaction process, the principle of which is based on the charge transfer mechanism between different two-dimensional materials in the stacking region and the difference in the electronic state distribution between the double layer and the single layer region. When the selective photochemical reaction starts, a light source with a photon energy greater than the band gap of the second two-dimensional single layer material (upper layer) and / or the first two-dimensional single layer material (lower layer) is used to irradiate the stacking region.

[0081] Please refer to Figure 2As shown in the figure, in the WS2-MoS2 van der Waals heterojunction, WS2 is used as the upper material and MoS2 is used as the lower material. Light excites the electrons in the upper WS2 to jump to the conduction band, forming electron-hole pairs. Due to the difference in energy bands in the heterojunction region, the conduction band and valence band positions of WS2 and MoS2 are different. Electrons are more easily transferred from the conduction band of WS2 to the lower MoS2, while holes remain in the upper WS2. As the illumination time increases, holes gradually accumulate in WS2, resulting in an increase in its chemical reactivity.

[0082] The accumulation of holes makes the upper layer of WS2 extremely active, capable of undergoing oxidation reactions with water molecules in the reaction medium (such as ultrapure water or dilute sulfuric acid solution). Specifically, the holes react with the oxygen atoms in the water molecules, gradually oxidizing WS2 into tungstic acid that is soluble in water.

[0083] As the photochemical reaction proceeds, the upper material of WS2 is gradually decomposed and removed from the edge. When the photochemical reaction reaches the boundary of the stacking area, that is, when the hydrolysis of WS2 advances to the edge with the lower MoS2, the reaction stops spontaneously. This is because the boundary between the upper and lower materials is spliced ​​and coupled, and the electrons enriched in the lower material MoS2 meet the holes accumulated in the upper material WS2 at the boundary and form charge binding. This charge binding effect prevents further accumulation of holes and blocks the continuation of the hydrolysis reaction. After the reaction is completed, the sample is dried with nitrogen to obtain an in-plane heterojunction sample in which the upper and lower monolayer materials are spliced ​​together.

[0084] By repeating the above steps S102 and S103, transferring other two-dimensional single-layer materials in turn and performing selected area photochemical reactions, a multi-dimensional in-plane splicing material containing multiple interfaces can be constructed.

[0085] The first two-dimensional single-layer material or the second two-dimensional single-layer material can be a single-component two-dimensional material or a multi-component spliced ​​two-dimensional material. A single-component two-dimensional material refers to a two-dimensional structure composed of a specific material. Common single-component two-dimensional materials include transition metal chalcogenides (TMDs), such as molybdenum sulfide, tungsten sulfide, molybdenum selenide, and the like. A multi-component spliced ​​two-dimensional material refers to a material spliced ​​together from two or more different two-dimensional materials. This splicing can be performed on the same plane by the aforementioned method or other methods to form an in-plane heterojunction. The advantage of multi-component spliced ​​materials is that they can combine the characteristics of different materials to achieve synergistic optimization of functions. For example, a heterostructure with superior optoelectronic performance can be constructed by splicing materials with different band gaps.

[0086] In an exemplary embodiment, the first two-dimensional single-layer material may be patterned before stacking the second two-dimensional single-layer material. The purpose of patterning is to selectively process the first layer of material through a pre-designed geometric shape or pattern to form a specific pattern or structure, so as to achieve the desired functional effect when stacking the second layer of material.

[0087] Patterning is designed to provide a customized structural basis for the preparation of stacked heterojunctions. By patterning the first layer of material, the arrangement and layout of the material in the subsequent stacking process can be precisely controlled. This precise control not only affects the geometry of the material, but also regulates the physical and chemical properties of the material. For example, patterning can form specific channels, interfaces or functional areas, thus providing the possibility of optimizing the function of heterojunctions in electronic or optoelectronic devices.

[0088] The heterostructure construction process in the present invention does not rely on synchronous growth technology, but is achieved through mechanical exfoliation and transfer stacking of two-dimensional materials. In operation, the first two-dimensional monolayer material (such as MoS2) is exfoliated and transferred to a substrate, and then the second two-dimensional monolayer material (such as WS2) is partially stacked on the first layer of material through the same exfoliation and transfer steps. Since transfer stacking is a physical process, the operator can accurately control the angle of the second layer of material relative to the first layer of material when transferring it, and can freely adjust the torsion angle between the two layers of material.

[0089] After stacking two-dimensional monolayer materials with different twist angles, the upper material in the stacking area (material with higher photochemical reaction activity) can be selectively removed through selective photochemical reaction. Since the upper material in the stacking area is removed, the originally stacked area becomes a direct splicing of two different materials in the same plane, forming an in-plane heterojunction. Since the twist angle between the two materials has been set during stacking, the newly formed in-plane heterojunction interface naturally has this twist angle.

[0090] Traditional CVD methods are usually unable to achieve the regulation of the twist angle between layers due to the lattice matching requirements of the growth substrate. However, the two-dimensional material transfer platform in the present invention can produce different twist angles between the upper and lower materials by manually regulating the stacking angle.

[0091] The present invention also provides a semiconductor device, which includes a two-dimensional in-plane splicing material produced by the above-mentioned two-dimensional semiconductor in-plane integration method.

[0092] The present invention will be further described below in conjunction with specific embodiments.

[0093] The present invention selects four transition metal chalcogenide (TMD) monolayers: molybdenum sulfide (MoS2), tungsten sulfide (WS2), molybdenum selenide (MoSe2), and tungsten selenide (WSe2) two-dimensional monolayer materials.

[0094] The specific preparation process is as follows:

[0095] (1) The TMD monolayer on the PDMS substrate was obtained by mechanical exfoliation.

[0096] (2) Combine the two-dimensional material transfer platform to transfer the TMD monolayer material to a flat gold substrate. After the sample is attached to the substrate, the heating temperature of the transfer platform is set to 80°C and maintained for 10 minutes. The PDMS is then lifted using the transfer platform to transfer the monolayer on the PDMS to the target substrate.

[0097] (3) Using the same method, align the second TMD monolayer material as required and attach it to the first monolayer. Then, set the heating temperature of the transfer platform to 80°C. After maintaining for 13 min, lift the PDMS using the transfer platform. At this time, the second monolayer is stacked on the first monolayer, thereby obtaining a weakly coupled van der Waals heterojunction sample.

[0098] The photohydrolysis reaction was carried out under a fluorescence microscope equipped with a highly sensitive scientific-grade camera, and the kinetic changes of the reaction process were observed in situ. The experimental setup is as follows: Figure 3 The photohydrolysis experimental steps include:

[0099] (1) One end of the PDMS is attached to the stage of the microscope, and the other end is used to fix the substrate with the sample.

[0100] (2) Place a drop of ultrapure water on the sample and place a cover glass on it. To offset the effect of the cover glass on the imaging, an objective lens with a correction ring can be used to optimize the imaging quality.

[0101] (3) The entire system is placed under a fluorescence microscope, and a power-adjustable mercury lamp or other light with a light bandgap energy greater than that of the TMD monolayer material is used as an excitation light source to illuminate the van der Waals heterojunction sample, so that the sample undergoes a selected photohydrolysis reaction. The image of the sample passes through a long-pass filter and is recorded and collected by a high-speed S-CMOS camera, thereby obtaining a dynamic fluorescence image or video of the heterojunction sample during the photohydrolysis process. After the reaction is completed, the sample is dried with nitrogen to obtain an in-plane heterojunction sample with two monolayers of material spliced ​​together.

[0102] Example 1

[0103] Prepare WS2 / MoS2 weakly coupled van der Waals heterojunction samples (such as Figure 4), and then a photohydrolysis experiment was performed on it to compare the pre- and post-hydrolysis (as shown in Figure 5 It can be seen from the optical photograph of the heterojunction double layer region after hydrolysis ( Figure 5 The contrast of the sample is reduced to that of a single layer, and combined with the Raman imaging of the sample (such as Figure 6 ), demonstrating the formation of WS2-MoS2 in-plane heterojunction.

[0104] The fluorescence microscope can record the fluorescence photos of the sample at each time during the reaction process of Example 1, so as to analyze the information of the photohydrolysis reaction kinetics. Figure 7 It can be seen that the photohydrolysis reaction starts from the edge of the upper WS2 heterojunction region, and the curve of the perimeter change of the reactant (WS2 monolayer in the stacking area) over time (such as Figure 8 The results show that the circumference of the reactant decays linearly with time, that is, the photohydrolysis reaction in this selected area is a zero-order reaction.

[0105] Example 2

[0106] WSe2 / WS2, WSe2 / MoSe2, and WSe2 / MoS2 van der Waals heterojunctions were prepared according to the aforementioned method and subjected to photohydrolysis reactions. The optical photographs before and after hydrolysis were compared (e.g. Fig. 9 , Fig.10 and Fig.11 As shown in the figure, it is proved that WSe2-WS2, WSe2-MoSe2, and WSe2-MoS2 in-plane heterojunctions were successfully constructed through selective photohydrolysis reaction.

[0107] Example 3

[0108] MoS2, WS2, and WSe2 monolayers were obtained on the PDMS substrate by mechanical exfoliation.

[0109] The MoS2 monolayer was transferred to a flat gold substrate using a two-dimensional material transfer platform. After the sample was attached to the substrate, the heating temperature of the transfer platform was set to 80°C and maintained for 10 minutes. The PDMS was then lifted using the transfer platform, and the MoS2 monolayer on the PDMS was transferred to the target substrate.

[0110] The WS2 monolayer was stacked on the MoS2 monolayer in the same way, and then the heating temperature of the transfer platform was set to 80°C. After maintaining it for 13 minutes, the PDMS was lifted using the transfer platform to obtain a WS2 / MoS2 weakly coupled van der Waals heterojunction sample.

[0111] The WS2-MoS2 in-plane heterojunction was obtained by selective photohydrolysis reaction of the WS2 / MoS2 weakly coupled van der Waals heterojunction sample.

[0112] The WSe2 monolayer was stacked onto the WS2-MoS2 in-plane heterojunction, and the interface boundary between WS2 and MoS2, one edge of WS2, and one edge of MoS2 were all partially covered by the WSe2 monolayer. After lamination, the heating temperature of the transfer platform was set to 80°C, and after maintaining for 13 minutes, the PDMS was lifted up using the transfer platform, and weakly coupled van der Waals heterojunction samples of WS2 / WSe2 and MoS2 / WSe2 were obtained at the same time.

[0113] The above heterojunction samples were subjected to selected area photohydrolysis reaction, and a WSe2-WS2-MoS2 in-plane heterojunction with three different interface boundaries (WSe2-WS2, WSe2-MoS2, WS2-MoS2) was obtained, and these three boundaries intersected at one point at the same time, as shown in Fig.12 shown.

[0114] Example 4

[0115] Combining electron beam exposure technology and plasma etching technology, the MoS2 monolayer on the gold substrate was first etched into a one-dimensional array consisting of MoS2 nanogaps with a width of 180nm. Then, using it as a template, a single layer of WS2 was stacked on it to obtain a weakly coupled WS2 / MoS2 van der Waals heterojunction, and finally a one-dimensional nanoscale MoS2-WS2NR-MoS2 in-plane superlattice was constructed through selective photohydrolysis reaction, such as Fig.13 shown.

[0116] Example 5

[0117] Combining electron beam exposure technology and plasma etching technology, the MoS2 monolayer on the gold substrate was etched into a two-dimensional array consisting of MoS2 square holes with a side length of 20μm. Then, using it as a template, a single layer of WS2 was stacked on it to obtain a weakly coupled WS2 / MoS2 van der Waals heterojunction. Finally, a millimeter-scale WS2-MoS2 in-plane heterojunction array was constructed through selective photohydrolysis reaction, such as Fig.14 shown.

[0118] Example 6

[0119] The weakly coupled van der Waals WS2 / MoS2 heterojunction was prepared on a graphene / Cu substrate using the aforementioned method, and then subjected to a selective photohydrolysis reaction. The optical and fluorescence photographs before and after hydrolysis proved the successful preparation of the WS2-MoS2 in-plane heterojunction. Fig.15 shown.

[0120] Example 7

[0121] The weakly coupled van der Waals WS2 / MoS2 heterojunction was prepared on a SiO2 / Si substrate using the aforementioned method, and then subjected to a selective photohydrolysis reaction. The optical photographs before and after hydrolysis proved the successful preparation of the WS2-MoS2 in-plane heterojunction, such as Fig.16 shown.

[0122] Then, the in-plane heterojunction was made into an electrical device by combining electron beam exposure technology and plasma etching technology. The device was tested under different back gates (V g =0,10,20,30,40,50V) and different excitation light powers (P laser =0,4,22,67μW) of IV curve (such as Fig.17 This demonstrates the feasibility of using the in-plane heterojunction prepared by the selective photohydrolysis method in semiconductor devices.

[0123] In summary, the two-dimensional semiconductor in-plane integration method and device provided by the present invention realizes the in-plane splicing of two-dimensional materials by utilizing the difference in electronic state distribution of different two-dimensional materials in the stacking area and the single-layer area, combined with photochemical reaction to selectively remove the upper material in the stacking area; the whole process can be carried out at room temperature, avoiding the limitations of high-temperature process; at the same time, by precisely controlling the photochemical reaction area, high-precision heterojunction patterning can be directly achieved, thus eliminating the need for additional micro-nano processing steps.

[0124] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0125] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A two-dimensional semiconductor in-plane integration method, characterized in that: include: providing a first two-dimensional monolayer material and placing it on a target substrate; partially stacking a second two-dimensional single-layer material on the first two-dimensional single-layer material to form a van der Waals heterojunction including a stacking region and a single-layer region; By using an excitation light source whose photon energy is greater than the luminescence band gap of the first two-dimensional monolayer material and / or the second two-dimensional monolayer material, the van der Waals heterojunction undergoes a selective photochemical reaction, so that the second two-dimensional monolayer material in the stacking area is selectively reacted and removed, so as to integrate and splice the first two-dimensional monolayer material and the second two-dimensional monolayer material in the same plane.

2. The two-dimensional semiconductor in-plane integration method according to claim 1, characterized in that: The material of the first two-dimensional single-layer material is molybdenum sulfide, tungsten sulfide, molybdenum selenide or tungsten selenide; and / or The second two-dimensional single-layer material is made of molybdenum sulfide, tungsten sulfide, molybdenum selenide or tungsten selenide.

3. The two-dimensional semiconductor in-plane integration method according to claim 1, characterized in that: The target substrate is a gold substrate, a SiO2 / Si substrate, a sapphire substrate, a quartz substrate, a boron nitride substrate or a graphene substrate.

4. The two-dimensional semiconductor in-plane integration method according to claim 1, characterized in that: Obtaining a first two-dimensional monolayer of material on a target substrate by physical vapor deposition, chemical vapor deposition or stripping; and / or A second two-dimensional monolayer material is obtained by physical vapor deposition, chemical vapor deposition or stripping, and a flexible polymer is used as an auxiliary substrate to transfer the second two-dimensional monolayer material to the first two-dimensional monolayer material, so that the second two-dimensional monolayer material is partially stacked on the first two-dimensional monolayer material to form a van der Waals heterojunction.

5. The two-dimensional semiconductor in-plane integration method according to claim 4, characterized in that: The two-dimensional semiconductor in-plane integration method further comprises: The interlayer distance between the first two-dimensional monolayer material and the second two-dimensional monolayer material is regulated to enhance the photochemical reaction activity of the second two-dimensional monolayer material in the stacking region.

6. The two-dimensional semiconductor in-plane integration method according to claim 1, characterized in that: The reaction medium of the selected-area photochemical reaction is a neutral or acidic aqueous solution.

7. The two-dimensional semiconductor in-plane integration method according to claim 1, characterized in that: Under the action of the excitation light source, the photogenerated electrons in the second two-dimensional single-layer material in the stacked area are transferred to the first two-dimensional single-layer material, so that the second two-dimensional single-layer material in the stacked area accumulates photogenerated holes.

8. The two-dimensional semiconductor in-plane integration method according to claim 1, characterized in that: Before stacking the second two-dimensional single-layer material, the first two-dimensional single-layer material is patterned.

9. The two-dimensional semiconductor in-plane integration method according to claim 1, characterized in that: The first two-dimensional single-layer material or the second two-dimensional single-layer material is a single-component two-dimensional material or a multi-component spliced ​​two-dimensional material.

10. A semiconductor device, characterized in that: It comprises a two-dimensional in-plane splicing material prepared by the two-dimensional semiconductor in-plane integration method as described in any one of claims 1 to 9.

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