Nanotube array preparation method, nanotube array and device

Abstract

The invention provides a nanotube array preparation method, a nanotube array and a device, and the method comprises the steps: preparing a double-layer two-dimensional material with a lattice-oriented relative included angle on a substrate, and taking the double-layer two-dimensional material as a template; the method comprises the following steps: determining chiral parameters of a to-be-prepared nanotube corresponding to a relative included angle of lattice orientation of a double-layer two-dimensional material, determining nanobelt orientation and nanobelt width based on the determined chiral parameters, and determining a distance between nanobelts based on the density of the to-be-prepared nanotube and the nanobelt width, etching the double-layer two-dimensional material based on the determined nanobelt orientation, nanobelt width and spacing between nanobelts to obtain a nanobelt array of the double-layer two-dimensional material; and performing thermal excitation treatment on the obtained nanotube array of the double-layer two-dimensional material to obtain the nanotube array. According to the invention, the nanotube array with controllable density, orientation and chirality can be prepared.

Description

Technical Field

[0001] The present invention relates to the fields of nano material preparation and semiconductor technology, and in particular to a nano tube array preparation method, a nano tube array and a device. Background Art

[0002] Single-walled carbon nanotubes (CNTs) can be viewed as quasi-one-dimensional structures formed by curling graphene. Depending on the curling mode (chirality), single-walled carbon tubes can exhibit metallic or semiconducting properties. Fully semiconducting, high-density (more than 125 per micron) parallel arrays of semiconducting single-walled carbon tubes are the core materials for building high-performance carbon-based transistors and integrated circuits.

[0003] At present, the preparation methods of single-walled carbon tubes are mainly divided into two categories: the first category is catalyst-assisted chemical vapor deposition (for example, see the following documents, document 1: Zhang S et al., Nature, 2017, 543: 234-238; document 2: Wang J et al., Nature Catalysis, 2018, 1: 326-331.), which can directly grow fully semiconducting or even single-chirality single-walled carbon tube arrays. However, the disadvantage of this method is that the synthesis temperature is too high, it is not compatible with integrated circuit technology, and the array density is low. The second type is the solution separation + assembly arrangement method. The typical scheme is to use polymer dispersion to obtain a single-walled carbon tube solution, combined with density gradient centrifugation to achieve metal-semiconductor single-walled carbon tube separation, and then self-assemble to form a carbon nanotube array wafer (for example, see the following documents, document 3: Liu L et al., Science, 2020, 368: 850-856; document 4: Jinkins KR et al., Science advances, 2021, 7 (37): eabh0640.). This type of method can meet the performance index requirements of advanced technology nodes in terms of semiconductor carbon tube purity and density, but it will introduce difficult-to-control polymer residues, and the arrangement of carbon tubes will also have local agglomeration, stacking and other inhomogeneities. At the same time, this type of method currently still lacks effective control over the chirality of carbon tubes, that is, the chirality of carbon tubes is randomly distributed.

[0004] In summary, the current carbon tube array preparation technology still has many difficulties and challenges. The density, orientation, chirality control and cleanliness of the carbon tube array are difficult to ensure at the same time, and thus cannot simultaneously meet the high orientation, high density, full semiconductor and high cleanliness requirements of carbon nanotube arrays when used to construct high-performance carbon-based transistors and integrated circuits, thus affecting the realization of high-performance carbon-based transistors and integrated circuits. Summary of the invention

[0005] In view of this, embodiments of the present invention provide a nanotube array preparation method, a nanotube array and a device to eliminate or improve one or more defects existing in the prior art.

[0006] In one aspect of the present invention, a method for preparing a nanotube array is provided, the method comprising the following steps:

[0007] a template preparation step, preparing a double-layer two-dimensional material having a relative angle of lattice orientation on a substrate, wherein the double-layer two-dimensional material is used as a template;

[0008] a nanoribbon array etching step, determining the chiral parameters of the nanotubes to be prepared corresponding to the relative angle of the lattice orientation of the double-layer two-dimensional material, determining the nanoribbon orientation and the nanoribbon width based on the determined chiral parameters, determining the spacing between the nanoribbons based on the density of the nanotubes to be prepared and the nanoribbon width, and etching the double-layer two-dimensional material based on the determined nanoribbon orientation, nanoribbon width and spacing between the nanoribbons to obtain a nanoribbon array of the double-layer two-dimensional material;

[0009] The nanotube array generation step is to subject the obtained double-layer two-dimensional material nanotube array to thermal excitation treatment to obtain a nanotube array.

[0010] In some embodiments of the present invention, the method of preparing a double-layer two-dimensional material having a relative angle of lattice orientation on a substrate includes: preparing a double-layer two-dimensional material having a relative angle of lattice orientation on the substrate by using mechanical exfoliation combined with a controllable angle transfer method or using liquid phase transfer combined with a controllable angle transfer method; or obtaining a single-layer two-dimensional material by mechanical exfoliation or liquid phase transfer, and folding the obtained single-layer two-dimensional material according to a set orientation to obtain a double-layer two-dimensional material having a relative angle of lattice orientation; or directly growing a double-layer two-dimensional material having a relative angle of lattice orientation by a growth method, wherein the growth method includes one of the following: chemical vapor deposition, molecular beam epitaxy or physical vapor deposition.

[0011] In some embodiments of the present invention, the etching of a double-layer two-dimensional material based on the determined nanoribbon orientation, nanoribbon width and spacing between nanoribbons includes: etching the double-layer two-dimensional material based on the determined nanoribbon orientation, nanoribbon width and spacing between nanoribbons using the following etching techniques: laser lithography, electron beam lithography, focused ion beam, high-energy electron beam, mask method or chemical etching.

[0012] In some embodiments of the present invention, the thermal excitation treatment includes one or more of the following treatments: annealing, laser excitation, Joule heating, and high-energy ray irradiation.

[0013] In some embodiments of the present invention, at least one layer of the two-dimensional material in the double-layer two-dimensional material is a p-type doped or n-type doped two-dimensional material.

[0014] In some embodiments of the present invention, at least one layer of the two-dimensional material in the double-layer two-dimensional material is a two-dimensional material with grain boundaries; different regions of the same double-layer two-dimensional material prepared in the template preparation step have relative angles of different lattice orientations, and / or different sections in the length direction of the nanoribbon of the same double-layer two-dimensional material in the nanoribbon array etching step correspond to different nanoribbon widths; the nanotube array obtained in the nanotube array generation step is an array of nanotubes spliced ​​with different chirality.

[0015] In some embodiments of the present invention, the nanoribbon array generation step also includes: determining the length of the nanoribbon based on the length of the nanotube to be prepared; etching the double-layer two-dimensional material based on the determined nanoribbon orientation, nanoribbon width and spacing between nanoribbons includes: etching the double-layer two-dimensional material based on the determined nanoribbon orientation, nanoribbon width, spacing between nanoribbons and length of the nanoribbon.

[0016] In some embodiments of the present invention, the double-layer two-dimensional material is a double-layer graphene, and the obtained nanotube array is a carbon nanotube array.

[0017] In some embodiments of the present invention, the double-layer two-dimensional material is a double-layer boron nitride two-dimensional material, a double-layer molybdenum sulfide two-dimensional material, a double-layer molybdenum selenide two-dimensional material or a double-layer tungsten sulfide two-dimensional material; the obtained nanotube array is a boron nitride nanotube array, a molybdenum sulfide nanotube array, a molybdenum selenide nanotube array or a tungsten sulfide nanotube array.

[0018] In some embodiments of the present invention, the nanoribbon orientation is obtained based on the following orientation formula:

[0019]

[0020] The nanoribbon width is obtained based on the following width formula:

[0021] Where ψ0 represents the nanoribbon orientation, w represents the nanoribbon width, a is the lattice constant of the two-dimensional material, and n and m are the chiral indices of the nanotube; or

[0022] The nanoribbon orientation and the nanoribbon width are obtained by introducing deviations into the orientation formula and the width formula, respectively.

[0023] Another aspect of the present invention provides a nanotube array prepared by the above method.

[0024] Another aspect of the present invention provides a semiconductor device (such as a carbon nanotube transistor) manufactured using the aforementioned nanotube array.

[0025] The nanotube array preparation method provided by the present invention can prepare a nanotube array with controllable density, orientation and chirality.

[0026] Furthermore, in some embodiments, a high-density, highly oriented, fully semiconducting single-walled carbon nanotube array with controllable chirality can be prepared. Since the density is controllable, the carbon nanotubes are evenly distributed without aggregation and stacking.

[0027] Additional advantages, purposes, and features of the present invention will be described in part in the following description, and will become apparent to those skilled in the art after studying the following, or may be learned from the practice of the present invention. The purposes and other advantages of the present invention may be achieved and obtained by the structures specifically indicated in the specification and the accompanying drawings.

[0028] Those skilled in the art will appreciate that the objectives and advantages that can be achieved with the present invention are not limited to the above specific description, and the above and other objectives that can be achieved by the present invention will be more clearly understood from the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The drawings described herein are used to provide a further understanding of the present invention, constitute a part of the present application, and do not constitute a limitation of the present invention. In the drawings:

[0030] Figure 1 Schematic diagram of the chirality of carbon nanotubes.

[0031] FIG. 2A to FIG. 2C Schematic diagram of the geometric relationship between the chirality of double-layer graphene nanoribbons and carbon tubes in one embodiment of the present invention.

[0032] Figure 3 FIG. 4 is a schematic diagram of a process for preparing a nanotube array according to an embodiment of the present invention.

[0033] Figure 4 Schematic diagram of the preparation process of a carbon nanotube array in one embodiment of the present invention. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments and the accompanying drawings. Here, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0035] It should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the solutions according to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0036] It should be emphasized that the term “include / comprises” when used herein refers to the presence of features, elements, steps or components, but does not exclude the presence or addition of one or more other features, elements, steps or components.

[0037] It should also be noted that, unless otherwise specified, the term “connection” herein may refer not only to a direct connection but also to an indirect connection involving an intermediate.

[0038] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the accompanying drawings, the same reference numerals represent the same or similar components, or the same or similar steps.

[0039] It should be emphasized here that the step marks mentioned below are not intended to limit the order of the steps, but it should be understood that the steps can be executed in the order mentioned in the embodiment, or in a different order from the embodiment, or several steps can be executed simultaneously.

[0040] The present invention aims at the problem that the density, orientation and chirality of the existing carbon nanotube array are difficult to be controlled simultaneously, thus resulting in uneven array orientation, local agglomeration, uneven distribution of stacking, or inconsistent chirality. A new method for preparing a single-walled carbon nanotube array with controllable chirality based on double-layer graphene is proposed. The method provided by the present invention is a new means for selecting and controlling the chirality of carbon nanotubes (or carbon tubes for short) from top to bottom, which can adjust the density p of the single-walled carbon nanotube array within the following range: 0<ρ≤350 roots / μm, and can keep the single-walled carbon nanotubes in the array highly consistent in orientation. In addition, the chirality of the carbon nanotubes can be controlled, that is, single-walled carbon nanotubes with specific chirality can be manufactured. Furthermore, gold half-junctions or chiral junctions with different band gaps can be introduced as needed to meet the needs of high-performance carbon nanotube transistors and integrated circuits for channel materials.

[0041] The principle of the method for preparing a nanotube array of the present invention will be described below by taking the preparation of a single-walled carbon tube using double-layer graphene as an example, and then the method for preparing a nanotube array of the present invention will be described in detail.

[0042] like Figure 1 As shown, the geometric structure of a single-walled carbon nanotube can be viewed as a layer of graphene curled along a chiral vector Ch. Depending on the direction and size of the chiral vector Ch, the curled carbon nanotube has different chirality, which can also be represented by Ch. Figure 1 The vectors a1 and a2 indicated by the arrows represent the basis vectors of the single-layer graphene lattice. In the present invention, the two zigzag edges of graphene are used as basis vectors to describe the geometric relationships involved in the present invention, including but not limited to angle relationships and length relationships. The principle derivation of different geometric descriptions but structural equivalence due to different basis vector selection methods is also covered within the protection scope of the present invention.

[0043] The chiral vector Ch of carbon nanotubes can be represented by basis vectors a1 and a2. When Ch=na1+ma2, the chirality of carbon nanotubes is (n, m). The electronic structure of carbon nanotubes is related to their chiral index. When nm is divisible by 3, carbon nanotubes are metallic; when nm is not divisible by 3, carbon nanotubes are semiconductors. At the same time, the band gap of carbon nanotubes is also affected by the size of Ch. The larger Ch is, the smaller the band gap is. Therefore, controlling the chirality of carbon nanotubes can control the electronic structure of carbon nanotubes. Figure 1 In the figure, θ represents the angle between the chiral vector and the graphene basis vector, and T represents the radial direction of the carbon nanotube.

[0044] like Figure 2A As shown in Figure 2, when a single layer of graphene is folded in half along 1 / 2Ch, the following Figure 2B The double-layer graphene nanoribbon shown. The geometric topology between the double-layer graphene nanoribbon at this time and the single-layer graphene before folding has not changed. If the carbon atoms of the upper and lower layers of the edges of the double-layer graphene nanoribbon on both sides are connected and the entire planar double-layer structure is bulged into a cylindrical shape, a carbon nanotube with a chiral vector of Ch is obtained. The inventors found that the edge of the double-layer graphene will form a bulging closed structure under annealing conditions. Based on this phenomenon, the inventors of the present application innovatively use double-layer graphene as a template for preparing a parallel array of carbon tubes, and then convert the double-layer graphene into a double-layer graphene nanoribbon array whose orientation and width match the chiral parameters of the carbon tubes by etching, and use thermal excitation treatments such as annealing to convert the double-layer graphene nanoribbon array into a single-walled carbon nanotube array. Therefore, the present invention proposes a method for obtaining a target chiral carbon nanotube by preparing a double-layer graphene nanoribbon of a specific relative angle and a specific width, and then by thermal excitation treatment (such as annealing).

[0045] The chirality of carbon nanotubes is determined by the relative angle θ0 between the lattice orientations of the two layers of graphene and the width w of the nanoribbon. FIG. 2A to FIG. 2C , for the target chiral vector C h , direction is θ, size is |C h | carbon nanotubes, according to the geometric relationship, the relationship between the target chirality (n, m) of the carbon nanotubes and the width w of the double-layer graphene nanoribbon and the relative angle θ0 of the lattice orientation between the double-layer graphene (i.e., the angle between the basis vectors of the two layers of graphene) is as follows (Formula Group 1):

[0046] θ0=60-2*θ;

[0047] w=0.5*|C h |;

[0048] The relative angle θ0 of the lattice orientation between the two layers of graphene determines the direction of the chiral vector Ch of the carbon nanotube (i.e., the angle θ between the chiral vector and the graphene basis vector), and the width w of the two-layer nanoribbon determines the size of the chiral vector Ch of the carbon nanotube. h |. The relationship between the chiral index (n, m) and the direction and magnitude of the chiral vector is (Formula Group 2):

[0049]

[0050]

[0051] Where a is the lattice constant of graphene, d t is the diameter of the target carbon tube, and θ is related to |C h |Substitute into Formula Group 1, and we can get the relationship between the width w of the double-layer graphene nanoribbon, the relative angle θ0 of the interlayer lattice orientation, and the target carbon tube chiral index (n, m) (Formula Group 3):

[0052]

[0053]

[0054] According to the relationship in the above formula, the present invention designs a double-layer graphene nanoribbon with a specific relative angle θ0 and a specific width w, and performs heat treatment such as annealing on the double-layer graphene nanoribbon to obtain carbon nanotubes with corresponding chirality.

[0055] The method of the present invention is not limited to the preparation of single-walled carbon nanotube arrays. Since the edges of double-layer two-dimensional material nanobelts generally close after annealing, by replacing the double-layer graphene with other two-dimensional material templates, the method designed by the present invention can also be applied to the production and processing of other one-dimensional nanotubes and their arrays. For example, based on double-layer boron nitride two-dimensional materials, molybdenum sulfide two-dimensional materials, molybdenum selenide two-dimensional materials and tungsten sulfide two-dimensional materials, boron nitride nanotube arrays, molybdenum sulfide nanotube arrays, molybdenum selenide nanotube arrays and tungsten sulfide nanotube arrays and other nanotube arrays can be prepared respectively. When calculating the orientation and width of the nanobelt to be etched, the lattice constant a of the graphene in the previous formula needs to be replaced with the lattice constant of the corresponding crystal. These new one-dimensional nanotube arrays also have the advantages of precise control of array density, orientation, and chirality. The nanotube arrays listed here are only examples, and the present invention is not limited to this.

[0056] Figure 3 FIG. 4 is a schematic diagram of a process for preparing a nanotube array according to an embodiment of the present invention. Figure 3 As shown, the method includes the following steps S110 to S130:

[0057] In the template preparation step S110, a double-layer two-dimensional material having a lattice orientation with a relative angle is prepared on a substrate, and the double-layer two-dimensional material is used as a template.

[0058] When the two-dimensional material is graphene, this method corresponds to the preparation of single-walled carbon nanotubes. In the embodiment of the present invention, there is no special requirement for the rotation of the substrate, and in principle, it can withstand the annealing temperature. However, since the nanotubes prepared by the method of the present invention have a high degree of cleanliness and can be used for the preparation of high-performance semiconductor devices, from the perspective of convenience for the subsequent direct preparation of semiconductor devices, the substrate can be a surface-insulated substrate, such as a surface-insulated silicon substrate, and more specifically, a silicon wafer covered with silicon dioxide, but the present invention is not limited to this.

[0059] The nanoribbon array etching step S120 determines the chiral parameters of the nanotubes to be prepared corresponding to the relative angle of the lattice orientation of the double-layer two-dimensional material, determines the nanoribbon orientation and the nanoribbon width based on the determined chiral parameters, determines the spacing between the nanoribbons based on the density of the nanotubes to be prepared and the nanoribbon width, and etches the double-layer two-dimensional material based on the determined nanoribbon orientation, nanoribbon width and the spacing between the nanoribbons to obtain a nanoribbon array of the double-layer two-dimensional material.

[0060] In the nanotube array generation step S130, the obtained nanotube array of double-layer two-dimensional material is subjected to thermal excitation treatment to obtain a nanotube array.

[0061] Based on the above steps, a nanotube array with determined chirality can be obtained.

[0062] In step S110, two layers of two-dimensional materials with relative lattice orientation angles are prepared on a substrate as a template. When the preparation method is used to prepare single-walled carbon nanotubes, the two layers of two-dimensional materials used as templates are double-layer graphene.

[0063] For a carbon nanotube array of a specified chirality (n, m), according to the relationship between the relative angle θ0 of the double-layer graphene and the chiral index (n, m) in Formula Group 3, it is first necessary to prepare a double-layer graphene with a relative interlayer rotation angle of θ0. There are many methods for preparing double-layer graphene with a relative interlayer rotation angle of θ0, for example, including: (1) mechanical exfoliation combined with a controllable angle transfer method (mechanical exfoliation + controllable angle transfer method); (2) liquid phase transfer combined with a controllable angle transfer method (liquid phase transfer + controllable angle transfer method); or (3) a single-layer graphene folding method.

[0064] (1) Mechanical peeling + controlled angle transfer method

[0065] The preparation of double-layer graphene by mechanical exfoliation + controlled angle transfer method means first using a mechanical exfoliation method to obtain two single-layer graphenes by two mechanical exfoliations respectively, and then using a controlled angle transfer technology to transfer the two single-layer graphenes obtained by the two mechanical exfoliations to a substrate to obtain double-layer graphene.

[0066] Among them, the mechanical exfoliation method is used to obtain single-layer graphene, that is, to separate the graphene sheets from the graphite crystal by applying mechanical force (such as friction and / or tension, etc.) to the graphite crystal. Since the mechanical exfoliation method for obtaining single-layer graphene is an existing mature technology, it will not be described in detail here.

[0067] The process of obtaining double-layer graphene using controlled angle transfer technology specifically includes:

[0068] After mechanical peeling is used to obtain two single-layer graphenes respectively, they can be kept on a transparent substrate such as PDMS (polydimethylsiloxane) and PMMA (polymethyl methacrylate) so that the relative superposition angle of the two single-layer graphenes can be controlled by an optical angle control console later; here, the material used for the transparent substrate is only an example, and the present invention is not limited to this.

[0069] In the process of controlling the relative superposition angle of two single-layer graphenes by using an optical angle control console, the lattice orientations of the two single-layer graphenes are determined and marked by means of angle-resolved Raman, crystallographic structure (such as edge angle, etc.) measurement or low-energy electron beam diffraction, and the two single-layer graphenes with determined crystallographic orientations are bonded together at a specific relative angle by using the optical angle control console at a controllable angle, thereby preparing a double-layer graphene with a relative angle of a specific lattice orientation;

[0070] Subsequently, the obtained double-layer graphene with a relative angle of a specific lattice orientation can be transferred to a substrate using a transfer technique such as a dry method or a wet method.

[0071] (2) Liquid phase transfer + controlled angle transfer method

[0072] The preparation of double-layer graphene by liquid phase transfer + controlled angle transfer method refers to obtaining two single-layer graphene by using two liquid phase transfers, and obtaining double-layer graphene by transferring the two single-layer graphenes obtained by the two liquid phase transfers to a substrate using controlled angle transfer technology.

[0073] The method of obtaining single-layer graphene by liquid phase transfer includes:

[0074] Liquid phase transfer is used to obtain two single-layer graphene substrates grown by chemical vapor deposition (CVD), molecular beam epitaxy (MBE), chemical vapor transport (CVT), etc. Then, the two obtained single-layer graphenes are kept on a transparent substrate such as PDMS, PMMA, etc., so that the relative superposition angle can be controlled by the subsequent angle control console.

[0075] In the process of controlling the relative superposition angle of two single-layer graphenes by using an optical angle control console, the lattice orientations of the two single-layer graphenes are determined and marked by means of angle-resolved Raman, crystallographic structure (such as edge angle, etc.) measurement or low-energy electron beam diffraction, and the two single-layer graphenes with determined crystallographic orientations are bonded together at a specific relative angle by using the optical angle control console at a controllable angle, thereby preparing a double-layer graphene with a relative angle of a specific lattice orientation;

[0076] Subsequently, the obtained double-layer graphene with a relative angle of a specific lattice orientation can be transferred to a substrate using a transfer technique such as a dry method or a wet method.

[0077] (3) Single-layer graphene folding method

[0078] A single layer of graphene can be obtained by mechanical exfoliation or liquid phase transfer, and then the obtained single layer of graphene is folded according to a set orientation to obtain a double-layer two-dimensional material with a relative angle of lattice orientation.

[0079] A double-layer two-dimensional material with a relative angle of lattice orientation can also be directly grown by growth methods such as chemical vapor deposition, molecular beam epitaxy or physical vapor deposition. By using the above methods, graphene can be replaced with other two-dimensional materials, and a double-layer two-dimensional material with a relative angle of lattice orientation can also be prepared on a substrate. Therefore, in a similar manner, a double-layer of two-dimensional materials such as boron nitride, molybdenum sulfide, molybdenum selenide, tungsten sulfide, etc. can also be obtained on a substrate in step S110, and the relative angle between each layer can be controlled.

[0080] In addition, in an embodiment of the present invention, for double-layer graphene with an arbitrary interlayer relative rotation angle θ0, such as double-layer graphene obtained by a direct growth method, the chiral index (n, m) that can be processed to meet the electronic structure requirements when the interlayer rotation angle is θ0 can also be inferred based on the actual required electronic structure of the carbon nanotube, such as semiconductor properties.

[0081] In step S120, before etching the nanoribbon array, it is first necessary to determine the chiral parameters of the nanotubes to be prepared, such as the chiral index (n, m), and then based on the determined chiral parameters of the nanotubes, determine the orientation of the nanoribbon array to be etched, that is, the angle ψ0 of the nanoribbon array to be etched relative to the lattice orientation of the double-layer two-dimensional material, and further determine the nanoribbon width and the spacing between the nanoribbons.

[0082] Taking the etching of a double-layer graphene nanoribbon array as an example, before etching the double-layer graphene nanoribbon array, it is necessary to first determine the angle ψ0 of the nanoribbon array to be etched relative to the double-layer graphene lattice. Due to the structural symmetry, the orientation of the nanoribbon should simultaneously satisfy the angle ψ with the basis vector direction of the two layers of graphene. Figure 2A-2C The geometric relationship shown in Figure 1 shows that when the angle between the chiral vector Ch and the graphene basis vector a1 is θ, we have:

[0083]

[0084] The crystallographic orientation of the double-layer graphene can be determined in a variety of ways, including but not limited to one or a combination of the following ways: optical microscopy, scanning electron microscopy, low-energy electron diffraction, electron diffraction, angle-resolved photoelectron spectroscopy, Raman spectroscopy, and high-resolution transmission electron microscopy, etc. Based on the determined crystallographic orientation of the double-layer graphene, the angle ψ of the orientation of the nanoribbon array to be etched relative to the double-layer graphene lattice can be determined, that is, the orientation of the double-layer graphene nanoribbon array can be determined.

[0085] After determining the orientation of the double-layer graphene nanoribbon array, the width of a single nanoribbon is determined by w in Formula Group 3, and the spacing Δx between nanoribbons is determined by the required carbon nanotube density ρ (the number of carbon nanotubes per unit length), which can be expressed as:

[0086] Δx=1 / ρ-w;

[0087] From the above formula, we can know that by adjusting the gap between the double-layer graphene nanoribbons (the width of the gap between the nanoribbons) Δx, the carbon nanotube array density ρ can be controlled. In addition, when Δx is 0, the carbon nanotube density ρ reaches the maximum value ρ max , the maximum density ρ max The diameter d of the target chiral carbon nanotubes t So it can be expressed as:

[0088] ρ max =1 / w=1 / (0.5*d t *π);

[0089] The control range of the density of carbon nanotubes in the carbon tube array in the present invention is 0<ρ<ρ maxIn addition, the length L of the graphene nanoribbon determines the length of the carbon nanotube formed after annealing, and the length L of the nanoribbon can be selected according to actual experimental requirements.

[0090] After determining the nanoribbon orientation, nanoribbon width, spacing between nanoribbons, and nanoribbon length, the nanoribbon array can be etched based on these parameters. There are many etching methods for double-layer graphene nanoribbon arrays, including but not limited to: laser lithography, electron beam lithography, focused ion beam, high-energy electron beam, mask method, chemical etching, etc., and one etching method can be selected to etch the nanoribbon.

[0091] In a manner similar to etching a graphene nanoribbon array, a nanoribbon array of two-dimensional materials such as a two-layer boron nitride nanoribbon array, a two-layer molybdenum sulfide nanoribbon array, a two-layer molybdenum selenide nanoribbon array, or a two-layer tungsten sulfide nanoribbon array can be prepared. These materials are only examples and the present invention is not limited thereto.

[0092] Similarly, the step S130 is described by taking the thermal excitation treatment of the double-layer graphene nanoribbon array as an example. There are many methods for the thermal excitation treatment in this step, as long as sufficient external excitation can be provided to cause the double-layer graphene nanoribbon to undergo edge closure reconstruction. As an example, the thermal excitation treatment may include one or more of the following treatments: annealing, laser excitation, Joule heating, and high-energy ray irradiation, but the present invention is not limited thereto.

[0093] Taking annealing as an example, in some embodiments of the present invention, the temperature of the annealing treatment of the double-layer graphene nanoribbon array can be, for example, between 250°C and 1300°C, and the range of the annealing time can be, for example, between 0.1s and 600s depending on the heating temperature, or annealing can be performed at different temperatures in different time periods, but the present invention is not limited thereto. The annealing treatment of the double-layer graphene nanoribbon array can be performed under vacuum conditions or in an inert gas environment.

[0094] When other thermal excitation treatment methods such as laser excitation, Joule heating or high-energy ray irradiation are used to replace annealing of the double-layer graphene nanoribbon array, the heating temperature range of these other thermal excitation treatment methods can also be between 250°C and 1300°C, and the heating time range can be, for example, between 0.1s-600s depending on the heating temperature.

[0095] After etching, the double-layer graphene nanoribbons have the same orientation ψ, nanoribbon spacing Δx, interlayer relative rotation angle θ0 and nanoribbon width w. The process of generating single-walled carbon nanotubes by thermal excitation only involves reconstructing the unsaturated carbon atoms on both sides of the double-layer graphene nanoribbons through thermal excitation. Therefore, the carbon nanotubes after thermal excitation have the same orientation ψ as the graphene nanoribbons, and the intertube spacing Δx is tube Since the planar structure changes to a tubular structure after forming the tube, it becomes Δxtube =Δx+wd t Since each carbon tube is transformed from a double-layer graphene with the same width w and the same relative angle θ0, each single-walled carbon nanotube in the array has the same chirality (n, m). Therefore, after the double-layer graphene nanoribbon array is thermally excited, the present invention can obtain single-walled carbon nanotubes with the same orientation ψ (high orientation) and the same spacing Δx tube (High uniformity), consistent chirality, all (n, m) (chirality controllable), density 0<ρ<ρ max Single-walled carbon nanotube arrays with adjustable spacing (i.e., high density and adjustable spacing).

[0096] At the same time, since the method of the present invention does not require catalyst growth and polymer centrifugal pulling and other means of growing, selecting and arranging carbon nanotubes, the impurity level only depends on the cleanliness of graphene and the residue of conventional semiconductor process flow. Therefore, the prepared carbon nanotube array has a cleanliness level that can be directly used for the preparation of high-performance devices.

[0097] Similar to the treatment of a double-layer graphene nanoribbon array, a double-layer nanoribbon array of other two-dimensional materials (such as a boron nitride nanoribbon array, a molybdenum sulfide nanoribbon array, a molybdenum selenide nanoribbon array or a tungsten sulfide nanoribbon array) obtained in step S120 is also thermally stimulated in the temperature range of 250°C to 1300°C. Since the tube forming temperatures of different materials are different, the thermal stimulation treatment temperature can be adaptively adjusted, and a nanotube array can also be obtained, such as a boron nitride nanotube array, a molybdenum sulfide nanotube array, a molybdenum selenide nanotube array or a tungsten sulfide nanotube array.

[0098] As can be seen from the above, the method of the present invention can prepare a carbon nanotube array with high orientation, high density, controllable chirality, adjustable spacing, uniform distribution and high cleanliness using double-layer graphene as a template. In addition, nanotube arrays of other materials can also be prepared in the same manner.

[0099] In some embodiments of the present invention, one or two layers of the double-layer graphene used to prepare single-walled carbon nanotubes can be replaced with p-type doped graphene or n-type doped graphene. When both layers are doped, the two layers of graphene can be of the same or different doping types. If the doping types of the two layers are the same, the carbon nanotubes prepared using this as a template are p-type carbon nanotube arrays or n-type carbon nanotube arrays. If one layer is replaced with p-type doped graphene and the other layer is replaced with n-type doped graphene, the carbon nanotube array prepared using this as a template is a carbon nanotube array with radial pn junctions.

[0100] In some embodiments of the present invention, since the chirality (n, m) of the prepared carbon nanotubes is regulated by the interlayer relative angle θ0 and the nanoribbon width w of the double-layer graphene nanoribbon, different relative angles θ0 and / or widths w can be introduced into the same double-layer graphene nanoribbon, so that carbon nanotubes spliced ​​by different chiralities can be formed, and the carbon nanotubes of different chiralities are connected by chiral junctions. The change of the interlayer angle θ0 can be caused by the introduction of grain boundaries. In comparison, the width w of the nanoribbon is better regulated and can be regulated by changing the etching template. More specifically, by converting one or two layers of graphene in the double-layer graphene into polycrystalline graphene, the graphene nanoribbons on both sides of the grain boundary can have different angles θ0. For the realization of different widths w, during the etching process, the retained nanoribbon width can be controlled to make different sections in the length direction of the same double-layer graphene nanoribbon correspond to different nanoribbon widths w.

[0101] Expanding to double-layer two-dimensional materials, when at least one layer of the two-dimensional material in the double-layer two-dimensional material can be a two-dimensional material with grain boundaries, different regions of the same double-layer two-dimensional material prepared in the template preparation step will have relative angles of different lattice orientations; correspondingly, the nanotube array obtained in the nanotube array generation step is an array of nanotubes with different chiralities spliced ​​together.

[0102] Similar treatment is also applicable to double-layer two-dimensional materials such as boron nitride, molybdenum sulfide, molybdenum selenide, and tungsten sulfide.

[0103] Figure 4 A schematic process for preparing single-walled carbon nanotube arrays on a substrate is shown in FIG.

[0104] like Figure 4 As shown in (a), double-layer graphene 20 and 30 having a relative angle θ0 of lattice orientation are prepared on a surface insulating substrate (such as a silicon wafer covered with silicon dioxide) 10. For example, a single-layer graphene 20 is peeled off from the surface of a graphite crystal by mechanical peeling, and the peeled single-layer graphene 20 is transferred to a substrate 10 with a predetermined orientation, and then the mechanical peeling and transfer steps are performed again to place the single-layer graphene 30 peeled off again on the single-layer graphene 20 peeled off for the first time, forming a stacked double-layer graphene as a template and the relative angle of the lattice orientation between the double-layer graphene is controlled to be θ0 during the transfer operation. In some embodiments of the present invention, θ0 can be any value between 0°-360°. In an alternative embodiment of the present invention, in the step of transferring, a double-layer graphene can also be placed on the substrate 10 at an arbitrary angle, and after the double-layer graphene is formed, the crystallographic relative angle is determined by means of a scanning electron microscope, a transmission electron microscope, etc.

[0105] Figure 4(b) shows that the double-layer graphene obtained in (a) is etched using a mask 40 to obtain a double-layer graphene nanoribbon array. First, the nanoribbon orientation (such as the angle ψ0 between the nanoribbon orientation and the graphene lattice orientation) and the nanoribbon width are determined based on the chiral parameters corresponding to the relative angle θ0, the spacing between the nanoribbons is determined based on the carbon tube density to be prepared and the nanoribbon width, and the double-layer graphene is etched based on the determined nanoribbon orientation, nanoribbon width and spacing between the nanoribbons to obtain a double-layer graphene nanoribbon array 50, as shown in FIG. Figure 4 The double-layer graphene nanoribbon array is annealed at a temperature between 250°C and 1300°C for a time between 0.1s and 600s. Depending on the annealing temperature, the obtained Figure 4 (d) shows a carbon nanotube array 60.

[0106] In the preparation process of the carbon nanotube array of the present invention, when there are errors in processing graphene nanoribbons, such as when there are width Δw, orientation Δψ errors and interlayer relative angle errors Δθ0 in the nanoribbons, at this time, since the perfect connection cannot be maintained geometrically, topological defects such as 5-8 rings and 5-7-7-5 rings will exist in the formed carbon nanotubes. As the error increases, the mismatch density of the edge of the double-layer graphene nanoribbon will increase accordingly, and the defect density in the formed carbon tube will also increase. However, since the edge of the double-layer graphene nanoribbon tends to form a closed structure to reduce energy under high temperature conditions, a carbon tube structure can always be formed. In the case of extreme degradation, if w, ψ0 and θ0 are not determined strictly in accordance with the geometric relationship described above, a carbon nanotube array can also be formed, which also has the characteristics of uniformity, high density, high cleanliness and adjustable spacing, but loses chirality controllability and introduces a large number of topological defects in the carbon nanotubes. However, this degradation technology for preparing carbon nanotube arrays should also be included in the protection scope of the present invention.

[0107] By using the geometric relationship between w, ψ0 and θ0 in the above formula, the present invention can also construct carbon nanotubes with gold half junctions and chiral junctions. At this time, the double-layer graphene is a double-layer graphene with at least one layer of grain boundaries, and different regions between the double-layer graphene have different relative angles. In addition, in the nanoribbon array etching step, in the nanoribbon array etching step, different chiral parameters of carbon nanotubes to be prepared from double-layer graphene with different relative angles are determined, and different nanoribbon widths corresponding to different chiral parameters in different sections in the nanoribbon orientation and the length direction of the nanoribbon can be further determined based on the determined different chiral parameters. The following is an example: different relative angles θ are introduced into the same double-layer graphene nanoribbon. 0A ,θ 0B With width w A With w B, where different relative angles are generated by the grain boundaries during graphene growth, and different widths can be set by the etching parameters during exposure and etching. After annealing such double-layer graphene nanoribbons to form carbon nanotubes, θ 0A , w A The chiral index of the segment (n A , m A ) and θ 0B , w B The chiral index of the segment (n B , m B ) can be obtained from the above formula, and at this time, a chiral carbon nanotube with a chiral difference is formed. On the contrary, the present invention can be based on the pre-designed chiral index (n A , m A ) and (n B , m B ) Use the formula to derive the processing parameters 0 0A ,θ 0B With w A , w B Since the chiral index determines the metallic and semiconducting properties of carbon nanotubes, when one side of the carbon nanotube is metallic and the other side is semiconducting, a carbon nanotube with a gold half-junction is formed. The number of chiral junctions and gold half-junctions depends on how many different processing parameter combinations w, ψ0 and θ0 are introduced into the same double-layer graphene strip.

[0108] The existing technology cannot simultaneously meet the requirements of high orientation, high density, full semiconductor, adjustable spacing, uniform distribution (referring to uniform spacing of carbon tubes, no agglomeration, no stacking), etc. On this basis, there is also a lack of effective means for controlling the chirality of carbon tubes. The existing CVD method for growing carbon nanotube arrays has a low and uncontrollable density of carbon nanotubes, a wide and non-single chirality distribution (i.e., the chirality is uncontrollable), and catalyst residues. The existing liquid phase pulling method for preparing carbon nanotube arrays has too high a density and is uncontrollable, and can only obtain semiconductor chirality (the chirality is not completely controllable). The nanotubes have complex orientations and stacking phenomena, and the prepared carbon nanotubes have polymer dirt. In contrast, the carbon nanotubes prepared by the method for preparing carbon nanotubes of the present application have controllable density and chirality, and can prepare both semiconductor carbon nanotubes and metallic carbon nanotubes. In addition, the spacing between carbon tubes is uniform and the surface is clean. Therefore, the method of the present invention can provide a single-walled carbon nanotube array that meets the requirements of controllable density, orientation and chirality, and the cleanliness of the prepared single-walled carbon nanotube array meets the requirements of carbon nanotube (CNT) transistors and their integrated circuits for carbon nanotube materials.

[0109] By using the carbon nanotube array with better performance prepared by the above method to construct a carbon nanotube transistor, device performance loss caused by carbon nanotube stacking, surface dirt, and tube diameter distribution can be avoided, and a carbon nanotube transistor with better performance can be obtained.

[0110] It should be clear that the present invention is not limited to the specific configuration and processing described above and shown in the figures. For the sake of simplicity, a detailed description of the known method is omitted here. In the above embodiments, several specific steps are described and shown as examples. However, the method process of the present invention is not limited to the specific steps described and shown, and those skilled in the art can make various changes, modifications and additions, or change the order between the steps after understanding the spirit of the present invention.

[0111] In the present invention, features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, and / or combined with features of other embodiments or replace features of other embodiments.

[0112] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the embodiments of the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a nanotube array, characterized in that: The method comprises the following steps: a template preparation step, preparing a double-layer two-dimensional material having a relative angle of lattice orientation on a substrate, wherein the double-layer two-dimensional material serves as a template; a nanoribbon array etching step, determining the chiral parameters of the nanotubes to be prepared corresponding to the relative angle of the lattice orientation of the double-layer two-dimensional material, determining the nanoribbon orientation and the nanoribbon width based on the determined chiral parameters, determining the spacing between the nanoribbons based on the density of the nanotubes to be prepared and the nanoribbon width, and etching the double-layer two-dimensional material based on the determined nanoribbon orientation, nanoribbon width and spacing between the nanoribbons to obtain a nanoribbon array of the double-layer two-dimensional material; The nanotube array generation step is to subject the obtained double-layer two-dimensional material nanotube array to thermal excitation treatment to obtain a nanotube array.

2. The method according to claim 1, characterized in that The method of preparing a double-layer two-dimensional material having a relative angle of lattice orientation on a substrate comprises: Using mechanical exfoliation combined with a controlled angle transfer method or using liquid phase transfer combined with a controlled angle transfer method to prepare a double-layer two-dimensional material with a relative angle of lattice orientation on the substrate; or Mechanical exfoliation or liquid phase transfer is used to obtain a single-layer two-dimensional material, and the obtained single-layer two-dimensional material is folded according to a set orientation to obtain a double-layer two-dimensional material with a relative angle of lattice orientation; or A double-layer two-dimensional material with a relative angle of lattice orientation is directly grown by a growth method, wherein the growth method includes one of the following: chemical vapor deposition, molecular beam epitaxy or physical vapor deposition.

3. The method according to claim 1, characterized in that The etching of the double-layer two-dimensional material based on the determined nanoribbon orientation, nanoribbon width and spacing between nanoribbons comprises: The double-layer two-dimensional material is etched based on the determined nanobelt orientation, nanobelt width and spacing between nanobelts using the following etching techniques: laser lithography, electron beam lithography, focused ion beam, high-energy electron beam, mask method or chemical etching.

4. The method according to claim 1, characterized in that The thermal excitation treatment includes one or more of the following treatments: annealing, laser excitation, Joule heating, and high-energy ray irradiation.

5. The method according to claim 1, characterized in that At least one layer of the two-dimensional material in the double-layer two-dimensional material is a p-type doped or n-type doped two-dimensional material.

6. The method according to claim 1, characterized in that At least one layer of the two-dimensional material in the double-layer two-dimensional material is a two-dimensional material having a grain boundary; Different regions of the same double-layer two-dimensional material prepared in the template preparation step have different relative angles of lattice orientation, and / or different sections of the same double-layer two-dimensional material nanoribbon in the nanoribbon array etching step correspond to different nanoribbon widths; The nanotube array obtained in the nanotube array generation step is an array of nanotubes spliced ​​with different chirality.

7. The method according to claim 1, characterized in that The nanoribbon array generation step further includes: determining the length of the nanoribbons based on the length of the nanotubes to be prepared; The etching of the double-layer two-dimensional material based on the determined nanoribbon orientation, nanoribbon width and spacing between nanoribbons includes: etching the double-layer two-dimensional material based on the determined nanoribbon orientation, nanoribbon width, spacing between nanoribbons and length of the nanoribbons.

8. The method according to any one of claims 1 to 7, characterized in that: The double-layer two-dimensional material is a double-layer graphene, and the obtained nanotube array is a carbon nanotube array.

9. The method according to claim 8, characterized in that The double-layer two-dimensional material having a relative angle of lattice orientation is at least one layer of double-layer graphene having a grain boundary, and different regions between the double-layer graphene have different relative angles; In the nanoribbon array etching step, different chiral parameters of carbon nanotubes to be prepared from double-layer graphene with different relative angles are determined, and different nanoribbon widths corresponding to different chiral parameters in different sections along the nanoribbon orientation and the nanoribbon length direction are determined based on the determined different chiral parameters.

10. The method according to any one of claims 1 to 7, characterized in that: The double-layer two-dimensional material is a double-layer boron nitride two-dimensional material, a double-layer molybdenum sulfide two-dimensional material, a double-layer molybdenum selenide two-dimensional material or a double-layer tungsten sulfide two-dimensional material; The obtained nanotube array is a boron nitride nanotube array, a molybdenum sulfide nanotube array, a molybdenum selenide nanotube array or a tungsten sulfide nanotube array.

11. The method according to claim 8, characterized in that: The nanoribbon orientation is obtained based on the following orientation formula: The nanoribbon width is obtained based on the following width formula: Where ψ0 represents the nanoribbon orientation, w represents the nanoribbon width, a is the lattice constant of the two-dimensional material, and n and m are the chiral indices of the nanotube; or The nanoribbon orientation and the nanoribbon width are obtained by introducing deviations into the orientation formula and the width formula, respectively.

12. A nanotube array, characterized in that: The nanotube array is prepared by the nanotube array preparation method according to any one of claims 1 to 11.

13. A carbon nanotube transistor prepared using a carbon nanotube array, characterized in that: The carbon nanotube array is prepared by the method according to claim 8 or 9.

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