Method for controlling density of single-walled carbon nanotube horizontal array by regulating and controlling width of crystal face step
By regulating the atomic step width of the crystal plane of the zirconia substrate (1 1 0) and combining with the chemical vapor deposition method, the problem of difficulty in simultaneously improving the density and orientation of the single-wall carbon nanotubes is solved, and a high-density and high-oriented single-wall carbon nanotube horizontal array is achieved.
Patent Information
- Application Number
- CN202411590054.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-08
- Publication Date
- 2025-03-25
AI Technical Summary
In the preparation of single-wall carbon nanotube horizontal arrays, the orientation degree or density is poor, making it difficult to achieve simultaneous control of high density and high orientation degree.
By selecting the crystal plane of the zirconia substrate (1 1 0), controlling the atomic step width by heat treatment, combined with the atmospheric chemical vapor deposition method, controllable growth of the horizontal array density of single-wall carbon nanotubes is achieved.
A horizontal array of single-wall carbon nanotubes with high density and high orientation is realized, with density adjustable to 130 wires/μm, overcoming the problem that density and orientation are difficult to simultaneously improve in traditional methods.
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Abstract
Description
Technical Field
[0001] The present invention relates to the field of controllable preparation of single-walled carbon nanotube horizontal arrays, and specifically to a method for controlling the density of single-walled carbon nanotube horizontal arrays by regulating the width of crystal plane steps. The method utilizes the strong restriction effect of single-crystalline zirconia substrate steps on single-walled carbon nanotubes to regulate the density of single-walled carbon nanotube horizontal arrays on the single-crystalline zirconia substrate, thereby achieving controllable preparation of high-density single-walled carbon nanotube horizontal arrays and providing a new candidate substrate for the preparation of single-walled carbon nanotube horizontal arrays. Background Art
[0002] Oriented single-walled carbon nanotubes can be used as electrode materials, interconnect wires and field effect transistor channel materials for nanoelectronic devices and chips. Parallel arrays of single-walled carbon nanotubes can be used to construct high-frequency and high-speed devices, thereby realizing radio frequency, logic and storage functions, and are one of the ideal candidate materials for building high-performance devices.
[0003] At present, there are two main methods for preparing single-walled carbon nanotube parallel arrays: post-processing and direct growth. The post-processing method is to disperse the single-walled carbon nanotube powder in a solution and perform dimensionally restricted self-assembly on the substrate surface, such as the pulling method or the DNA template method (Reference 1, Liu LJ; Han J.; Peng LMet.al.; Science, 2020, 368(6493); Document 2, Shi H.W.; Zhang ZY; Peng LMet al.; Nature Electronics, 2021, 4(6); Document 3, Zhao MY; Chen YH; Sun W.et al.; Science, 2020, 368(6493)). The direct growth method is to disperse metal nanoparticles on a single crystal substrate such as sapphire or quartz, and catalytically grow single-walled carbon nanotubes on the surface of the substrate through high-temperature chemical vapor deposition. The single-walled carbon nanotubes grow along the steps or lattice direction of the substrate to form parallel horizontal arrays (Reference 4, Li P., Hu, Y., Zhang, J., et.al.; Advanced Functional Materials, 2022, 2209391; Reference 5, Zhao X.; Peng LM; Li Y; Nano Research, 2023, 16 (11)).
[0004] The main problems faced in preparing parallel arrays of single-walled carbon nanotubes are: the post-treatment self-assembly method can obtain high-density single-walled carbon nanotube arrays, but its orientation is poor, and it is particularly susceptible to interference from longer single-walled carbon nanotubes, forming a wavy arrangement; the single-walled carbon nanotube horizontal arrays grown by direct catalytic chemical vapor deposition have a high degree of orientation, but the catalyst is easily deactivated due to carbon supersaturation during the growth process, resulting in a low density of the horizontal array. In particular, on a quartz substrate with lattice orientation, due to the weak interaction between the atomic lattice and the single-walled carbon nanotubes, non-oriented disordered single-walled carbon nanotubes often appear; and the step width of the sapphire substrate that has been heat-treated at 1100℃ for more than 10h is large (>7.5nm), so the current single-walled carbon nanotube horizontal array density directly grown is up to 130 / μm, while the horizontal array density usually prepared is less than 50 / μm.
[0005] Therefore, there is an urgent need to develop a method that can simply and efficiently control the horizontal array density of single-walled carbon nanotubes to promote their application in the field of high-speed and high-frequency carbon-based nanoelectronic devices. Summary of the invention
[0006] The purpose of the present invention is to provide a method for controlling the density of a single-walled carbon nanotube horizontal array by regulating the width of a crystal plane step. The method can simply and efficiently regulate the density of a single-walled carbon nanotube horizontal array by regulating the width of a crystal plane step. The width of the atomic step of the growth substrate determines the number of steps on the substrate surface, and then determines the density of the single-walled carbon nanotubes grown on the edge of the attached step. By utilizing the strong confinement effect of the step on the single-walled carbon nanotube, a high-orientation, high-density carbon nanotube horizontal array can be obtained.
[0007] The technical solution of the present invention is:
[0008] A method for regulating the step width of a crystal plane to control the density of a horizontal array of single-walled carbon nanotubes. The method comprises the following steps: selecting a zirconium oxide substrate (1 1 0) crystal plane, regulating the atomic step width of the zirconium oxide substrate by heat treatment, wherein the heat treatment temperature is 775 to 900°C, the holding time is 3 to 15 minutes, and the atomic step width of the zirconium oxide substrate (1 1 0) crystal plane ranges from 5 to 15 nm. A normal pressure chemical vapor deposition method is adopted to realize the controllable growth of the horizontal array density of single-walled carbon nanotubes by utilizing the confined space provided by the steps.
[0009] In the method for regulating the crystal plane step width to control the single-walled carbon nanotube horizontal array density, the heat treatment atmosphere is an oxygen-free atmosphere, and parallel, ordered, and width-adjustable steps are obtained after the heat treatment.
[0010] In the method for regulating the crystal plane step width to control the density of the single-walled carbon nanotube horizontal array, the oxygen-free atmosphere for heat treatment is argon, hydrogen or carbon monoxide.
[0011] The method for regulating the crystal plane step width to control the horizontal array density of single-walled carbon nanotubes is as follows: when the heat treatment temperature is 775-800°C, the atomic step width of the zirconium oxide substrate (1 1 0) crystal plane ranges from 4 to 6 nm; when the heat treatment temperature is 825-850°C, the atomic step width of the zirconium oxide substrate (1 1 0) crystal plane ranges from 7.5 to 12 nm; when the heat treatment temperature is 875-900°C, the atomic step width of the zirconium oxide substrate (1 1 0) crystal plane ranges from 11 to 17.5 nm.
[0012] The method for controlling the crystal plane step width to control the horizontal array density of single-walled carbon nanotubes is to control the atomic step width of the zirconium oxide substrate crystal plane and deposit more than 1000 / μm on the zirconium oxide substrate (1 1 0) crystal plane. 2 High density of catalyst nanoparticles.
[0013] The method for regulating the step width of the crystal plane to control the horizontal array density of single-walled carbon nanotubes adopts atmospheric pressure chemical vapor deposition to directly regulate the different step widths on the surface of the zirconia substrate, deposit catalysts and grow single-walled carbon nanotubes, the growth temperature is 775-800°C, and the carbon source is carbon monoxide with a flow rate of 25-30sccm.
[0014] The method for regulating the step width of the crystal plane to control the density of the horizontal array of single-walled carbon nanotubes is characterized in that the catalyst is prepared by a block copolymer assembly method, a spin coating method, a magnetron sputtering method or an immersion pulling method.
[0015] In the method for regulating the crystal plane step width to control the horizontal array density of single-walled carbon nanotubes, the catalyst is nanoparticles of transition metals Fe, Co or Ni.
[0016] According to the method for regulating the crystal plane step width to control the density of the single-walled carbon nanotube horizontal array, the density of the single-walled carbon nanotube horizontal array reaches 130 tubes / μm.
[0017] The design concept of the present invention is:
[0018] With a face-centered cubic (FCC) structure and a lattice constant of Zirconia with a melting point of 2715℃ is used as the substrate. Its (1 1 0) plane has atomic gaps with the same orientation and parallel arrangement. High-temperature heat treatment can produce oxygen vacancies, causing the constituent atoms to shift and the lattice to distort. The higher the temperature, the greater the change in the crystal structure, making the width of the atomic steps wider as the temperature rises. Therefore, by subjecting the FCC structure single crystal zirconia substrate to high-temperature heat treatment, steps with adjustable width can be obtained; the strong interaction of the steps on the crystal plane with the single-walled carbon nanotubes can be used to control the growth of a horizontal array of single-walled carbon nanotubes with controllable density.
[0019] The present invention controls the width of the step by heat treating the oxide substrate of a specific crystal plane at different temperatures; adopts atmospheric pressure chemical vapor deposition to prepare single-walled carbon nanotube horizontal arrays of different densities using steps of different widths to achieve density control. The present invention controls the interaction between single-walled carbon nanotubes and crystal plane atoms by designing the crystal plane of the zirconium oxide substrate and controlling the step width, thereby providing a new method and new idea for controlling the density of single-walled carbon nanotubes and providing a new candidate substrate for the preparation of single-walled carbon nanotube horizontal arrays.
[0020] The advantages and beneficial effects of the present invention are:
[0021] (1) The present invention selects a new type of single-crystal zirconia as a substrate, and adjusts the atomic step width of the substrate (1 1 0) crystal plane by simple heat treatment, thereby achieving control over the step width of the substrate crystal plane; and then uses atmospheric pressure chemical vapor deposition to grow a density-adjustable single-walled carbon nanotube horizontal array on the zirconia substrate steps, laying a material foundation for exploring the development of high-frequency and high-speed carbon nanotube-based nanoelectronic devices and their application in carbon-based chips.
[0022] (2) The present invention explores a new type of single crystal substrate with adjustable step width, and uses the influence of atomic step width on the horizontal array density of single-walled carbon nanotubes to provide a new idea for substrate control of the horizontal array density of single-walled carbon nanotubes.
[0023] (3) The present invention overcomes the uncontrollability and low repeatability of increasing catalyst density and activity in the traditional chemical vapor deposition method, and utilizes the width of the step to achieve the horizontal array density of single-walled carbon nanotubes, which has the advantages of strong controllability, good repeatability, and easy scalability. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 Typical atomic force micrographs of (1 1 0) crystal plane zirconia substrates heat treated at different temperatures. (a) 775℃; (b) 825℃; (c) 875℃; (d) step width statistics, the horizontal axis Temperature is the temperature (℃), and the vertical axis Stepwidth is the step width (nm).
[0025] Figure 2 .(1 1 0) Morphology of Co catalyst nanoparticles on the crystalline zirconia substrate: (a) Atomic force microscope photo; (b) Statistical distribution of particle size, with the horizontal axis Diameter being the diameter (nm) and the vertical axis Counts being the counts.
[0026] Figure 3.Horizontal arrays of single-walled carbon nanotubes grown on (1 1 0) zirconia substrates with different step widths at 865°C: (ac) typical atomic force microscopy images, with step widths of 5.9 nm, 9 nm and 15 nm, respectively; (b) scanning electron microscopy images, with step widths of 5.9 nm, 9 nm and 15 nm, respectively.
[0027] Figure 4 .(1 1 0) Single-walled carbon nanotubes grown on the step-free surface of a zirconia substrate: (a) typical atomic force microscopy image, (b) scanning electron microscopy image.
[0028] Figure 5 .(a) Atomic force microscopy morphology of spinel (1 1 0) crystal plane; (b) Step width statistics of spinel (1 1 0) crystal plane, the horizontal axis MgAl2O4 (1 1 0) is the spinel (1 1 0) crystal plane, and the vertical axis Step width is the step width (nm); (c) Scanning electron microscope photograph of a horizontal array of single-walled carbon nanotubes grown at 865℃. DETAILED DESCRIPTION
[0029] In the specific implementation process, the present invention uses single-crystal zirconium oxide with exposed (1 1 0) crystal plane as a substrate, and obtains highly consistent and uniform atomic steps through heat treatment at 775-900°C for 3-15 minutes, and its width is adjustable in the range of 5-15nm; a metal nanoparticle catalyst is prepared on the surface of the zirconium oxide substrate, and a horizontal array of single-walled carbon nanotubes with different densities is grown on the surface of the crystal face steps by chemical vapor deposition.
[0030] The method of the present invention for regulating the step width of the crystal plane to control the horizontal array density of single-walled carbon nanotubes comprises the following specific steps:
[0031] (1) Pretreatment of zirconia substrate:
[0032] The single crystal zirconia substrate with the (1 1 0) crystal plane exposed was ultrasonically cleaned in N,N-dimethylformamide and isopropanol for 10 to 15 minutes, and then dried with a nitrogen gun. It was placed in a quartz boat and pushed into a tube furnace for heat treatment at 775 to 800°C, 825 to 850°C, and 875 to 900°C for 3 to 15 minutes, respectively, and then cooled to room temperature and taken out. The atomic force microscope morphology and step width statistics are shown in the figure. Figure 2 As shown, it can be seen that atomic steps suitable for the growth of single-walled carbon nanotubes are uniformly and orderly distributed on the substrate, and the step widths are 4-6nm, 7.5-12nm and 11-17.5nm respectively.
[0033] (2) A uniform solution is obtained by heating and stirring a certain concentration of organic matter and inorganic salt, and then suspended and dropped on the crystal surface of the zirconium oxide substrate at a speed of 3000-8000 rpm, and then oxidized at 415-520°C and reduced with H2 at 521-800°C to obtain catalyst nanoparticles.
[0034] (3) Growth of single-walled carbon nanotubes by chemical vapor deposition
[0035] At a temperature of 775-800° C., 25-30 sccm CO is used as a carbon source to grow a single-walled carbon nanotube horizontal array for 3-5 minutes.
[0036] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention is described in detail below through embodiments and drawings, but this is not intended to limit the scope of protection of the present application.
[0037] Example 1
[0038] In this embodiment, a method for regulating the step width of the crystal plane to control the density of the horizontal array of single-walled carbon nanotubes is provided, and the specific steps are as follows:
[0039] (1) Zirconia substrate pretreatment
[0040] Zirconia with exposed (1 1 0) crystal plane was selected as the substrate, and the above specific step (1) was used for pretreatment. The heat treatment temperatures were 775°C for 15 min, 825°C for 9 min, and 875°C for 6 min, respectively. The heat treatment atmosphere was Ar. The atomic step width of the substrate was regulated by the heat treatment conditions. Figure 1 ac), the step width distribution range of (1 10) crystal plane is ~5.5nm, ~9nm and ~13nm ( Figure 1 d), the width of the step becomes wider with the increase of heat treatment temperature.
[0041] (2) Catalyst preparation
[0042] The Co catalyst with a particle size of 1 to 2 nm was assembled on the (1 1 0) crystal plane zirconia treated at 775°C in step (1) by a chemical self-assembly method, and the average particle size was 1.5 nm ( Figure 2 ab), density is ~1500 particles / μm 2 This laid the foundation for the subsequent control of the diameter, conductivity and even chirality of single-walled carbon nanotubes. The preparation conditions of other high-temperature heat treatment steps were similar, and high-density catalyst nanoparticles were obtained.
[0043] In this embodiment, a polystyrene-b-poly 4-vinylpyridine PS-b-P4VP (such as PS3500-b-P4VP3100 produced by Polymer Source Inc.) polymer and cobalt nitrate Co(NO3)2 are heated and stirred at 75°C to obtain a uniform solution, the organic matter concentration is 0.3wt%, the inorganic salt concentration is 0.3mM, and the solvent is dimethylacetamide; the solution is suspended and dropped on the crystal surface of the zirconium oxide substrate at a speed of 3000rpm, and oxidation at 500°C and H2 reduction treatment at 775°C are carried out in sequence to obtain catalyst nanoparticles.
[0044] (3) Growth of single-walled carbon nanotubes by chemical vapor deposition
[0045] Single-walled carbon nanotubes were grown at 775°C with 30 sccm CO as the carbon source for 5 min. Typical AFM morphologies of single-walled carbon nanotubes obtained at different step widths are shown in Figure 2. Figure 3 The scanning electron microscope morphology is shown in Fig. Figure 3 As shown in df, the density of single-walled carbon nanotubes prepared with a step width of ~5.5nm is ~130 / μm, which is the highest value of directly grown horizontal arrays at present; the density of single-walled carbon nanotubes prepared with a step width of ~9nm is 90 / μm, and the density of single-walled carbon nanotubes prepared with a step width of ~13nm is 60 / μm. It can be seen that the narrower the step width, the more steps per unit length of the substrate, and the higher the density of the single-walled carbon nanotube horizontal array grown. This provides a new optional substrate and a new idea for density control for single-walled carbon nanotube horizontal arrays.
[0046] Comparative Example 1: Growth of Single-walled Carbon Nanotubes on a Step-free Zirconia Substrate
[0047] In order to illustrate the effect of the step width of the single crystal zirconia substrate on the horizontal array density of single-walled carbon nanotubes, a (1 1 0) crystal plane zirconia without pre-heat treatment and step formation was selected as the substrate, and the methods of steps (2) and (3) of Example 1 were used to prepare catalyst nanoparticles and grow single-walled carbon nanotubes. Typical atomic force microscope morphology and scanning electron microscope morphology are shown in Figure 4 ab. It can be seen that the lack of step restriction causes the single-walled carbon nanotubes to grow too fast and without orientation, confirming the decisive role of the (1 1 0) crystal plane steps on the zirconia substrate in the high orientation and high density growth of the horizontal array.
[0048] Comparative Example 2: Growth of single-walled carbon nanotubes on the (1 1 0) crystal plane of a spinel substrate
[0049] (1) MgAl2O4 spinel with exposed (1 1 0) crystal plane was selected as the substrate, and the substrate was pretreated at 825°C according to step (1) in Example 1, and catalyst nanoparticles and single-walled carbon nanotubes were prepared according to steps (2) and (3). The atomic force microscope morphology and scanning electron microscope morphology are shown in FIG. Figure 5 a, c, the step width statistics are shown in Figure 5 b. It can be seen that the average step width is ~23nm, and the density of the grown single-walled carbon nanotubes is ~30 / μm, which is smaller than the density of the single-walled carbon nanotube horizontal array prepared on the zirconia substrate with a narrower step width (1 1 0) (5.5-13nm), further verifying the density difference of the single-walled carbon nanotube horizontal arrays grown with different step widths.
[0050] The embodiments and comparative examples illustrate that the present invention selects zirconium oxide as the substrate, and by adjusting the heat treatment conditions, the atomic step width on its (1 1 0) surface is regulated, and then the density of the single-walled carbon nanotube horizontal array is regulated by chemical vapor deposition, and the density can be regulated to 60 / μm, 90 / μm and 130 / μm. The mechanism of step-by-step regulation of array density is explained, and a new candidate substrate and new ideas are provided for the control of the density of the single-walled carbon nanotube horizontal array, which is expected to lay a material foundation for the application of single-walled carbon nanotubes in the materials of high-frequency and high-speed carbon-based devices.
Claims
1. A method for controlling the horizontal array density of single-walled carbon nanotubes by regulating the step width of the crystal plane, characterized in that: The (1 1 0) crystal plane of the zirconia substrate was selected, and the atomic step width of the zirconia substrate was regulated by heat treatment. The heat treatment temperature was 775-900°C, and the holding time was 3-15 min. The atomic step width of the (1 1 0) crystal plane of the zirconia substrate ranged from 5 to 15 nm. The atmospheric pressure chemical vapor deposition method was used to realize the controllable growth of the horizontal array density of single-walled carbon nanotubes by utilizing the confined space provided by the steps.
2. The method for controlling the horizontal array density of single-walled carbon nanotubes by adjusting the step width of the crystal plane according to claim 1, characterized in that: The heat treatment atmosphere is an oxygen-free atmosphere, and parallel, orderly, and width-adjustable steps are obtained after the heat treatment.
3. The method for controlling the horizontal array density of single-walled carbon nanotubes by adjusting the step width of the crystal plane according to claim 2, characterized in that: The oxygen-free atmosphere for heat treatment is argon, hydrogen or carbon monoxide.
4. The method for controlling the horizontal array density of single-walled carbon nanotubes by adjusting the step width of the crystal plane according to claim 2 or 3, characterized in that: When the heat treatment temperature is 775-800°C, the atomic step width of the (1 1 0) crystal plane of the zirconia substrate is in the range of 4-6nm; when the heat treatment temperature is 825-850°C, the atomic step width of the (1 1 0) crystal plane of the zirconia substrate is in the range of 7.5-12nm; when the heat treatment temperature is 875-900°C, the atomic step width of the (1 1 0) crystal plane of the zirconia substrate is in the range of 11-17.5nm.
5. The method for controlling the horizontal array density of single-walled carbon nanotubes by adjusting the step width of the crystal plane according to claim 1, characterized in that: By adjusting the atomic step width of the zirconia substrate crystal surface, more than 1000 atoms / μm are deposited on the (1 1 0) crystal surface of the zirconia substrate. 2 High density of catalyst nanoparticles.
6. The method for controlling the horizontal array density of single-walled carbon nanotubes by adjusting the step width of the crystal plane according to claim 1 or 5, characterized in that: The atmospheric pressure chemical vapor deposition method is used to directly control the different step widths on the surface of the zirconia substrate, deposit catalysts and grow single-walled carbon nanotubes. The growth temperature is 775-800°C, and the carbon source is carbon monoxide with a flow rate of 25-30sccm.
7. The method for controlling the horizontal array density of single-walled carbon nanotubes by adjusting the step width of the crystal plane according to claim 6, characterized in that: The catalyst is prepared by a block copolymer assembly method, a spin coating method, a magnetron sputtering method or an immersion and pulling method.
8. The method for controlling the horizontal array density of single-walled carbon nanotubes by adjusting the step width of the crystal plane according to claim 6, characterized in that: The catalyst is nanoparticles of transition metals Fe, Co or Ni.
9. The method for controlling the horizontal array density of single-walled carbon nanotubes by adjusting the step width of the crystal plane according to claim 1, characterized in that: The density of single-walled carbon nanotube horizontal arrays reaches 130 tubes / μm.