CN107416808B - Preparation method of graphene-carbon nanotube nano composite structure - Google Patents
Preparation method of graphene-carbon nanotube nano composite structure Download PDFInfo
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- CN107416808B CN107416808B CN201710729825.0A CN201710729825A CN107416808B CN 107416808 B CN107416808 B CN 107416808B CN 201710729825 A CN201710729825 A CN 201710729825A CN 107416808 B CN107416808 B CN 107416808B
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Abstract
The invention relates to a method for preparing a graphene-carbon nanotube nano composite structure in one step. The method is based on the principle of plasma enhanced chemical vapor deposition, and comprises the steps of directly growing carbon nanotubes on a metal or semiconductor substrate containing catalytic elements, and simultaneously, directly epitaxially growing graphene on the walls of the carbon nanotubes to form a graphene sheet composite structure taking the carbon nanotubes as a substrate; under the condition that the growth conditions are met, the sizes of the carbon nano tube and the graphene sheet are simultaneously increased; the interface of the graphene and the carbon nano tube forms ohmic contact characteristic in a carbon-carbon chemical bond combination mode. The method is simple, the simultaneous growth of the graphene and the carbon nano tube is realized in one step, and the novel carbon nano composite structure has important application in devices such as electron emission, energy conversion, energy storage and the like.
Description
Technical Field
The invention relates to a preparation method of a nano structure, in particular to a self-assembly growth method of a two-dimensional atomic crystal structure based on a one-dimensional carbon nano structure, belonging to the field of nano materials and electronic materials.
Technical Field
Carbon nanostructures have attracted considerable attention in the fields of electronic information, energy, and the like due to their unique physical and chemical properties. How to exert the respective characteristic advantages of different carbon nano structures to cooperatively obtain high-performance structures and materials has important significance for promoting the realization of wide application of the carbon nano materials.
The graphene is formed by sp carbon atoms2The hybrid orbit forms a single-layer atomic structure material with hexagonal honeycomb lattice arrangement, and the application of the single-layer atomic structure material with excellent and unique physical and chemical characteristics such as high electron mobility, high thermal conductivity and the like in photoelectric devices such as super capacitors, field emission electron sources, solar cells and the like can bring about innovation of device performance. For example, the vertical graphene has the characteristics of single atomic state tip and large surface area in structure, and has high electron mobility and high thermal conductivity in characteristics, and the vertical graphene serving as a field electron emitter is favorable for obtaining large currentAn emission characteristic.
The field electron emission (field emission for short) refers to a physical process in which the width and height of a potential barrier on the surface of an object are reduced under the action of an electric field, and electrons in the object penetrate through the surface potential barrier to enter vacuum, and is a method for rapidly and efficiently obtaining electron emission. One-dimensional nanostructures represented by carbon nanotubes bring about a strong electric field enhancement of the emission end face due to their particularly high numerical aspect ratio, and thus exhibit electron emission characteristics at low electric fields and are applied to field emission cold cathode electron sources. How can one achieve low electric field and high current emission capability characteristics of nanostructure emitters? The invention provides an idea of utilizing a composite structure to exert respective characteristic advantages of a one-dimensional nano structure and two nano structures and cooperatively obtain a nano structure emitter with low electric field and high current emission capability, and the idea is realized on a graphene-carbon nano tube nano composite structure. Specifically, the graphene-carbon nanotube nanocomposite structure integrates a graphene sheet and a carbon nanotube emitter, and electron emission is simultaneously from the end faces of the carbon nanotube and the end faces of the graphene sheet; the interface between the graphene sheet and the carbon nanotube is in ohmic contact, so that a good electron transmission channel is provided and the Joule heat of the interface is reduced; due to the abundant surface area of the graphene sheet, a heat dissipation channel is greatly increased in the field emission process, and the current endurance characteristic is improved. Such a composite structure will also be suitable for use as an electrode material for energy storage devices and the like.
Disclosure of Invention
The invention provides a method for synthesizing a graphene-carbon nanotube nano composite structure in one step, and simultaneously provides a nano structure with high-current electron emission capability. The technical scheme of the invention is as follows:
a preparation method of a graphene-carbon nanotube nano composite structure is characterized in that a carbon nanotube grows on a substrate with a catalytic element based on a plasma enhanced chemical vapor deposition principle, and graphene directly grows on the wall of the carbon nanotube in an epitaxial manner to form a graphene sheet composite structure taking the carbon nanotube as a matrix.
Preferably, the method for growing the graphene-carbon nanotube nanocomposite structure comprises the following steps:
a) selecting metal or semiconductor containing carbon nanotube growth catalytic element component as substrate material;
b) reducing and heating the substrate under the action of low-temperature plasma, and forming nanoparticles with catalytic activity on the surface of the substrate selected in the step a);
c) the method is characterized in that a plasma enhanced chemical vapor deposition method is adopted to synthesize and grow the carbon nano tube on the substrate of the nano particles with catalytic activity, and simultaneously, graphene is directly epitaxially grown on the wall of the carbon nano tube.
d) And maintaining a certain growth time, and growing the graphene on the wall of the carbon nanotube at a certain angle to form a sheet structure.
Preferably, the reaction temperature for synthesizing the graphene-carbon nanotube nano composite structure by the plasma enhanced chemical vapor deposition method is 500-950 ℃, and the graphene is directly grown from the wall of the carbon nanotube by carbon atoms in an ordered structure mode.
Preferably, in the synthetically grown carbon nanocomposite structure, graphene and carbon nanotubes are bonded by means of chemical bonds to form a connection with ohmic contact characteristics.
Preferably, the catalytic element comprises an oxide of chromium, iron, manganese, nickel or a solid solution thereof.
Preferably, the substrate comprises metal and semiconductor substrates into which catalytic elements are introduced by various methods, including magnetron sputtering methods, and evaporation deposition methods.
The method is simple, the simultaneous growth of the graphene and the carbon nano tube is realized in one step, and the novel carbon nano composite structure has important application in devices such as electron emission, energy conversion, energy storage and the like.
Drawings
Fig. 1 is a schematic diagram of a graphene-carbon nanotube nanocomposite structure grown on a substrate, wherein 1 represents a substrate, 2 represents a carbon nanotube, and 3 represents graphene;
fig. 2 is a diagram of the morphology of graphene-carbon nanotubes, fig. 2a and 2b respectively show scanning electron microscope images of the top morphologies of a graphene-carbon nanotube film and a single nanostructure, fig. 2c respectively shows a high power transmission electron microscope image of the interface of graphene and carbon nanotubes, and fig. 2d shows an atomic arrangement image obtained by inverse fourier transform of the interface;
fig. 3 is an electrical characteristic representation of a single graphene-carbon nanotube nanocomposite structure, fig. 3a is a schematic diagram of an interfacial conductance test of graphene and carbon nanotubes, and fig. 3b is an I-V characteristic curve. Fig. 3c is a schematic diagram of a field emission characteristic test of a single graphene-carbon nanotube, and fig. 3d is an I-V characteristic curve.
The abstract is as follows: 1 represents a substrate, 2 represents a carbon nanotube, and 3 represents graphene.
Detailed Description
The contents and technical solutions of the present invention are further illustrated by the following specific examples, which should not be construed as limiting the present invention. It is within the scope of the present invention to make simple modifications or alterations to the methods, procedures or conditions of the present invention without departing from the spirit of the invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art.
The specific implementation process of the invention is as follows:
step 1: and cleaning the substrate. Selecting stainless steel containing carbon nanotube growth catalytic element components as a substrate material, and ultrasonically cleaning the stainless steel substrate with acetone, ethanol and deionized water in sequence for more than 10min each.
Step 2: preparation of the growth environment. And (3) placing the cleaned substrate on a sample table close to a microwave source by adopting microwave plasma enhanced chemical vapor deposition equipment, and pumping the vacuum degree of the equipment to be below 10 Pa.
And step 3: substrate H2And (4) preprocessing. After the vacuum is pumped to below 10Pa, 100sccm of H is introduced2And maintaining the pressure at 220Pa, turning on a microwave source with 500W power, adding substrate bias voltage to 100V, exciting the gas, generating low temperature plasma, maintaining the process for 20min, removing oxide and other pollutants on the surface of the substrate, and raising the temperature of the substrate to about 400 ℃.
And 4, step 4: and (4) growing the nano composite structure. After the step 3 lasts for 20min, the microwave source and the growth bias voltage are cut off, and CH with the volume of 7sccm is introduced4Maintaining the gas pressure at 220Pa, turning on the microwave source with micropower of 500W, and exciting H under bias of 200V2，CH4Gas, generating carbon-containing reactive radicals, which lasts for 30 min. In such a low-temperature plasma atmosphere containing carbon, short carbon nanotubes grow on the stainless steel substrate at an early stage; then, nucleating and epitaxially growing graphene at the wall defect of the carbon nanotube; under the condition of sufficient carbon source supply, the sizes of the graphene and the carbon nano tube are simultaneously increased along with the increase of time, and finally the graphene-carbon nano tube nano composite structure is obtained.
And 5: cutting off the microwave source, growing bias voltage and gas source, vacuumizing to below 10Pa, cooling to room temperature, and taking out the sample.
The implementability of the technical scheme is illustrated by the characterization of the interface morphology structure and the electricity of the graphene and the carbon nanotube and the characterization of the field emission characteristic of a single graphene-carbon nanotube nano composite structure.
And analyzing the appearance and the interface of the sample by using a scanning electron microscope and a high-resolution transmission electron microscope. Fig. 2a and 2b show the morphology of the graphene-carbon nanotube film and the top region of a single graphene-carbon nanotube, respectively. The single graphene-carbon nanotubes exhibit a tree-like structure and are independently distributed from each other. FIG. 2c shows the distribution of lattice fringes at the interface between graphene and carbon nanotubes in the nanocomposite structure, with a fringe spacing of 0.35 nm; and performing inverse Fourier transform analysis on the interface region to obtain a graphene and carbon nanotube interface atom arrangement diagram 2d, wherein the interfaces of the graphene and the carbon nanotube are connected in a carbon-carbon chemical bond mode, which implies that carbon atoms are bonded with carbon atoms of the carbon nanotube at the defect position of the carbon nanotube wall, and the epitaxial growth of the graphene on the carbon nanotube wall is realized.
And characterizing the conductive characteristic of the interface of the graphene and the carbon nano tube and the field emission characteristic of a single graphene-carbon nano tube nano composite structure. Two nanoprobes were contacted with graphene and carbon nanotubes, respectively, as in FIG. 3a, using a self-contained voltage source of model Keithley 6487The picoampere meter is used as a device for recording I-V characteristic characterization, and a test system is vacuumized to 1 x 10-4About Pa, a voltage can be applied to record the I-V characteristic. As shown in fig. 3b, the obtained I-V characteristic curve between the graphene and the carbon nanotube is a straight line, which indicates that the graphene and the carbon nanotube are combined together in an ohmic contact manner, and a good electron transport channel is provided. In addition, in order to characterize the field emission characteristics, a sample to be tested is used as a field emission cold cathode, a tungsten nanoprobe is used as a test anode, the distance between the anode and the cathode is fixed at 1 mu m, and as shown in fig. 3c, a Piano table with a Keithley 6487 self-contained voltage source is also used as a device for recording I-V characteristic characterization. FIG. 3d is a graph of 8I-V curves and corresponding F-N curves obtained from a single graphene-carbon nanotube sample undergoing 8I-V rounds. The maximum field emission current of the single graphene-carbon nanotube is 90.65 muA.
In summary, the present invention provides a method for growing graphene-carbon nanotube nano composite structure on a metal or semiconductor substrate having a catalytic element based on the plasma enhanced chemical vapor deposition principle. The carbon atoms are arranged at the defects of the carbon nanotube wall in an ordered structure mode, so that the epitaxial growth of the graphene on the carbon nanotube wall is realized. The main advantages of the invention include: firstly, the preparation method is simple, and the simultaneous growth of the carbon nano tube and the graphene is realized without any pretreatment and post-treatment; secondly, the carbon nano composite structure is a large-current emitter with an integrated structure formed by integrating a nano-scale tip and an atomic-scale thickness tip, and ohmic contact is formed between the nano-scale tip and the atomic-scale thickness tip, so that the conductivity between the nano-scale tip and the atomic-scale thickness tip is enhanced, and the joule heat at the interface between the nano-scale tip and the atomic-scale thickness tip is reduced; in the carbon nano composite structure, the graphene sheet has rich surface area, so that the heat dissipation channel is greatly increased in the field emission process or the electron transportation process, and the flow resistance is improved.
Claims (5)
1. A preparation method of a graphene-carbon nanotube nano composite structure is characterized by comprising the following steps: based on the principle of plasma enhanced chemical vapor deposition, the carbon nano tube grows on a metal or semiconductor substrate with catalytic elements, and simultaneously graphene directly grows on the wall of the carbon nano tube in an epitaxial manner, and the method specifically comprises the following steps:
a) selecting a substrate containing carbon nano tube growth catalytic element components;
b) reducing and heating the substrate under the action of low-temperature plasma, and forming nanoparticles with catalytic activity on the surface of the substrate selected in the step a);
c) synthesizing and growing carbon nanotubes on a substrate of nanoparticles with catalytic activity by adopting a plasma enhanced chemical vapor deposition method, and epitaxially growing graphene on the wall of the carbon nanotube;
d) and keeping the growth time for a certain time, and growing the graphene on the wall of the carbon nanotube at a certain angle to form a sheet structure.
2. The method of claim 1, wherein the graphene-carbon nanotube nanocomposite structure comprises: the reaction temperature of the plasma enhanced chemical vapor deposition method for synthesizing and growing the carbon nano tube is between 500 and 950 ℃, and the carbon atoms epitaxially grow the graphene from the wall of the carbon nano tube in an ordered structure mode.
3. The method of claim 1, wherein the graphene-carbon nanotube nanocomposite structure comprises: the graphene and the carbon nano tube which are synthesized and grown are combined in a chemical bond mode to form connection with the ohmic contact characteristic.
4. The method of claim 1, wherein the graphene-carbon nanotube nanocomposite structure comprises: the catalytic element comprises an oxide of chromium, iron, manganese, nickel or a solid solution thereof.
5. The method of claim 1, wherein the graphene-carbon nanotube nanocomposite structure comprises: the substrate comprises a metal and semiconductor material substrate with a catalytic element introduced by various methods, wherein the catalytic element is introduced by a magnetron sputtering method or an evaporation deposition method.
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| KR102601607B1 (en) * | 2018-10-01 | 2023-11-13 | 삼성전자주식회사 | Method of forming graphene |
| CN111092155B (en) * | 2019-10-28 | 2023-01-17 | 温州大学 | Metal nanoparticle-containing single-walled carbon nanotube intramolecular junction and preparation method and application thereof |
| CN111607763B (en) * | 2020-06-17 | 2022-02-11 | 武汉纺织大学 | Method for rapidly growing metal single atom on carbon-based carrier by microwave-induced metal discharge and application thereof |
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