CN108910868B

CN108910868B - Method for preparing graphene dendrite on insulating substrate

Info

Publication number: CN108910868B
Application number: CN201810903586.0A
Authority: CN
Inventors: 许士才; 李迎仙; 张晶; 孙丽; 于法鹏; 王吉华; 赵显�
Original assignee: Shandong University; Dezhou University
Current assignee: Shandong University; Dezhou University
Priority date: 2018-08-09
Filing date: 2018-08-09
Publication date: 2020-04-03
Anticipated expiration: 2038-08-09
Also published as: CN108910868A

Abstract

The invention relates to a method for preparing graphene dendrites on an insulating substrate, which belongs to the technical field of microelectronic materials, and comprises the steps of cleaning and drying the insulating substrate; putting the substrate into the outer wall of a quartz inner tube in a CVD tube furnace, vacuumizing the tube furnace, heating to 200-300 ℃, introducing hydrogen, and etching the surface of the substrate at constant temperature when the temperature is raised to 800-900 ℃; slowly raising the temperature after hydrogen etching, raising the temperature to 1050-1080 ℃, keeping the temperature constant, and introducing a carbon source and hydrogen to grow graphene; and after the growth is finished, stopping introducing the gas, cooling to 700-800 ℃, and naturally cooling to room temperature. The form of the graphene dendrite is dendritic and is distributed at the top ends of the branches, and the growth of the graphene on the insulating substrate into a dendritic structure is realized by controlling the conditions such as the introduction amount of methane, the ratio of methane to hydrogen and the like in the preparation method. Compared with the reticular graphene, the dendritic graphene has better mechanical and electrical properties.

Description

Method for preparing graphene dendrite on insulating substrate

Technical Field

The invention belongs to the technical field of microelectronic materials, and particularly relates to a method for preparing graphene dendrites on an insulating substrate.

Background

Graphene is a honeycomb crystal structure in which carbon atoms are densely arranged by sp2 hybridization, and is a two-dimensional material having a thickness of only a single atomic layer. In 2004, it was produced by mechanical exfoliation of Highly Oriented Pyrolytic Graphite (HOPG) by two scientists, Geim and Novoselov, united kingdom. Graphene is also a basic unit constituting other materials, and it can be wrapped with zero-dimensional fullerene, rolled into one-dimensional carbon nanotubes, and stacked into three-dimensional graphite. The unique structure of graphene determines its unique properties. The ideal graphene material has the electron mobility of 200000cm at room temperature²V · s; high specific surface area; thermal conductivity at room temperature is 5000WV (m · K); the light transmittance is high, and the light transmittance of single graphene can reach 97%; the graphene has high strength, is a material with the highest strength in the world, and has wide application prospects in transparent electrodes, field effect transistors, energy storage devices and the like due to the excellent electrical, mechanical, optical, thermal and other properties.

After many years of research by scientists, the preparation method of graphene has been developed in various ways, including: a mechanical peeling method; silicon carbide (SiC) epitaxial growth; a redox method and a Chemical vapor deposition method (CVD). The chemical vapor deposition method is an effective way for preparing large-area and high-quality graphene due to the advantages of low cost, simple and easy process flow and the like, and the main principle is to utilize methane (CH)₄) And decomposing the carbon source at high temperature by using carbon-containing gas as a carbon source to perform chemical reaction to generate graphene.

Dendrites refer to a dendritic-like crystal morphology that grows in a non-equilibrium state. Dendrites are common in nature, for example, snow is a type of dendrite, and many metals and alloys also exhibit a dendritic morphology. In the field of materials, scientific researchers pay attention to the fields of sensing, catalysis and the like due to the advantages of larger specific surface area, good conductivity and the like of the dendrites.

Graphene dendrites can be regarded as a derivative of graphene. So far, few reports on graphene dendrites have been made. The traditional graphene preparation mainly comprises the preparation of film-shaped graphene, and the film-shaped graphene is weaker than graphene dendrite in the aspects of electrical properties and the like.

Chinese patent CM103172058A discloses a method for preparing three-dimensional reticular graphene, wherein electrodes are inserted into two ends of a graphite oxide solution, after positive and negative pulse voltages are applied to the electrodes, graphite oxide is subjected to two processes of positive pulse voltage adsorption and negative pulse voltage reduction on the same electrode, graphite oxide particles are adsorbed and reduced on the surface of the electrode, grow upwards in a tree form, and are finally accumulated to form the three-dimensional reticular graphene. The patent uses graphite oxide as raw material, and applies positive and negative pulse voltage to electrodes at two ends of the graphite oxide through a signal generator so as to reduce and adsorb the graphite oxide. The raw material graphite oxide used in the method contains elements such as hydrogen, oxygen and the like, the sample is easily polluted due to insufficient reaction in the reduction process, the structure of the graphite oxide is complex, the particle layer is thick, and dendritic crystals are easily accumulated together to form the three-dimensional reticular graphene.

Chinese patent CN103834993A discloses a method for preparing graphene dendrites and graphene dendrites thereof, wherein after square-wave electrical signals are applied to two ends of a graphene oxide solution, the current density actually used exceeds the limit current density by regulating and controlling the duty ratio, frequency and voltage, the diffusion overpotential is sharply increased, graphene oxide particles are seriously lacked near the electrodes, and only part of crystal faces that the particles can reach continue to grow as whisker-shaped dendrites, namely the graphene dendrites. The method also can not avoid the pollution of impurity elements such as hydrogen, oxygen and the like to the dendritic crystal sample of the graphene.

Chinese patent CN105417525A discloses a preparation method of dendritic three-dimensional graphene, which is prepared by adding CuSO₄,NiSO₄And H₂SO₄The mixed solution is prepared by taking Cu as a working electrode to deposit Cu clusters or CuNi clusters as a substrate for depositing dendritic crystal of graphene, cleaning nano metal clusters in ultrapure water, filtering and freeze-drying, placing the freeze-dried nano metal clusters in a vacuum furnace, firstly carrying out reduction treatment in a hydrogen atmosphere at an experimental temperature, then introducing mixed gas of hydrogen and methane at the experimental temperature to carry out graphene deposition treatment, and finally utilizing (NH)₄)₂SO₄Solutions or FeCl₃Removing the alloy substrate by the solution to obtain the dendritic graphene. The substrate acted by the method is a metal substrate, in practical application, the substrate needs to be etched by using a chemical reagent and transferred to an insulating substrate by using organic matter assistance, and the method causes damage and pollution of a sample to a certain extent.

Disclosure of Invention

In view of the above problems in the prior art, it is an object of the present invention to provide a method for preparing graphene dendrites on an insulating substrate. The method for preparing the graphene dendrite by using the chemical vapor deposition method is simple to operate and good in repeatability, and the excellent graphene dendrite can be prepared.

In order to solve the technical problems, the technical scheme of the invention is as follows:

a method for preparing graphene dendrites on an insulating substrate comprises the following specific steps:

1) cleaning and blow-drying the insulating substrate;

2) putting the dried substrate in the step 1) into the outer wall of a quartz inner tube in a CVD tube furnace, vacuumizing the tube furnace, heating to 200-300 ℃, introducing hydrogen, and etching the surface of the substrate at constant temperature when the temperature is increased to 800-900 ℃;

3) slowly raising the temperature after hydrogen etching, raising the temperature to 1050-1080 ℃, keeping the temperature constant, and introducing a carbon source and hydrogen to grow graphene;

4) and after the growth is finished, stopping introducing the gas, cooling to 700-800 ℃, and naturally cooling to room temperature to obtain the graphene dendrite.

The graphene dendrite is prepared on the insulating substrate, the form of the graphene dendrite is dendritic and is distributed at the top end of the branch, and the graphene is arranged on the Si surface or SiO of the substrate₂The surface is firstly formed into a spherical shape, branches grow out from the top end of the spherical shape, and branches grow into a tree shape. The surface of hydrogen sculpture substrate makes carbon source and better combination of substrate, and methane decomposes the back, and the carbon source grows at the substrate surface under high temperature, and after the sculpture, the influence of remaining oxygen to the experiment in carbon source and hydrogen let in simultaneously can avoiding experimental to hydrogen can keep the slow decomposition of methane, improves the quality of graphite alkene dendritic crystal. Compared with graphene prepared on an insulating substrate in the prior art, the dendritic graphene crystal with the dendritic shape is prepared, and the dendritic graphene crystal has better mechanical and electrical properties. The substrate is located the quartz inner tube outer wall of CVD tube furnace and has better effect and can be abundant utilization methane than the position of placing in prior art, has improved the utilization efficiency of methane, and the graphite alkene dendritic crystal effect of formation is better.

Preferably, the insulating substrate in the step 1) is a silicon wafer, the thickness of the silicon wafer is 400-600 μm, and the surface of the silicon wafer is amorphous SiO₂Silicon wafer of layer, said SiO₂The thickness of the layer is 100-400nm, SiO₂The surface of the layer is polished, and the surface of the Si layer is not polished.

Further preferably, the silicon wafer is 550 μm thick, and the SiO film is formed of SiO₂The thickness of the layer was 200-350 nm.

Preferably, in the step 1), a chemical cleaning agent is adopted for ultrasonic cleaning, and chemical cleaning agents of acetone, ethanol and deionized water are sequentially adopted for cleaning, wherein the cleaning time is 8-12 min; the cleaning time is 9-11 min.

Preferably, the vacuum degree pressure in the CVD tube furnace in the step 2) is 10^-5～10^-4mbar。

Preferably, the purity of the hydrogen in the step 2) is more than 99.9%, and the hydrogen flow is 15-25 sccm.

Further preferably, the hydrogen flow rate in the step 2) is 15 to 20 sccm.

Preferably, the heating rate of the temperature rising to 200-300 ℃ in the step 2) is 8-12 ℃/min, and the heating rate of the temperature rising to 800-900 ℃ is 8-12 ℃/min.

Preferably, the time of the hydrogen constant-temperature etching in the step 2) is 30-60 min.

Further preferably, the time of hydrogen constant-temperature etching is 30-40 min.

Preferably, the temperature rising rate in the step 3) is 4-6 ℃/min when the temperature rises to 1050-1080 ℃, the temperature is kept for 30-120 min, and the pressure is the same as that in the step 2). Further preferably, the temperature is kept constant for 100-120 min in the step 3).

Preferably, the carbon source introduced in the step 3) is methane, the purity of the methane is more than 99.9%, and the flow rate of the methane is 15-60 sccm; the ratio of the introduced methane to the introduced hydrogen is 2: 3-4: 1.

Further preferably, the flow rate of methane is 25 to 40 sccm.

Preferably, the cooling rate of the temperature in the step 4) to 700-800 ℃ is 100-200 ℃/min.

The method for preparing the graphene dendrite on the insulating substrate is used for preparing the graphene dendrite growing on the insulating substrate.

The application of the graphene dendrite growing on the insulating substrate in preparing a microelectronic device.

The invention has the beneficial effects that:

1. the experimental operation is simple, the raw material cost is low, and the experimental repeatability is good;

2. directly depositing and growing on the insulating substrate without chemical transfer, and being directly applied to the field of electronic devices;

3. the method comprises the steps of firstly carrying out hydrogen etching on a substrate to improve the structure of the surface of the substrate, enabling the surface of the substrate to form certain defects, then enabling graphene to grow on the substrate, enabling the substrate and the graphene to be combined more tightly,

4. the condition such as the introduction amount of methane, the ratio of methane to hydrogen and the like in the preparation method is controlled to realize that the graphene grows to be a dendritic structure on the insulating substrate;

5. the substrate is positioned on the outer wall of the quartz inner tube in the CVD tube furnace, and the inventor finds that the carbon source on the outer wall of the quartz inner tube is easier to deposit, can obtain a better deposition effect and is easier to grow dendritic crystals.

6. The original method for preparing the graphene dendrite uses a graphene oxide raw material, the graphene oxide structure is complex, three-dimensional reticular graphene is easy to form, and the dendritic graphene has better mechanical and electrical properties compared with the reticular graphene.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the application and, together with the description, serve to explain the application and are not intended to limit the application.

FIG. 1 is an experimental schematic diagram of a chemical vapor deposition-based method for preparing graphene dendrites;

FIG. 2 is a scanning electron microscope image of graphene dendrites on the side of a silicon substrate;

FIG. 3 is SiO on a silicon substrate₂And a Raman spectrum image of the graphene dendrite on the Si surface;

FIG. 4 is a scanning electron microscope image of graphene dendrites on the surface of a silicon substrate;

FIG. 5 is a selected area diffraction spot image of a silicon substrate graphene dendrite sample.

Detailed Description

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

All instruments and raw materials of the invention are commercial products

The invention will be further illustrated by the following examples

Fig. 1 is a schematic diagram of the principle of preparing graphene dendrites on an insulating substrate according to the present invention, the substrate is placed on the outer wall of a quartz inner tube of a tube furnace, methane, hydrogen and a mixed gas enter the tube furnace, the methane is decomposed, and carbon is deposited on the substrate to grow into graphene dendrites.

Example 1

A method for preparing graphene dendrites on an insulating substrate using SiO₂The method takes a/Si substrate as an example and comprises the following steps:

(1) SiO with a thickness of 500 μm₂And ultrasonically cleaning the Si substrate and drying.

(2) Putting the dried silicon substrate in the step (1) into the outer wall of a quartz inner tube in a CVD tube furnace, vacuumizing the tube furnace, and keeping the vacuum pressure at 10^-5mbar, heating to 300 ℃, heating rate of 10 ℃/min, and closing the molecular pump; heating to 800 ℃, keeping the temperature for 30min, and introducing hydrogen for hydrogen etching, wherein the hydrogen flow is 15 sccm; slowly heating to 1050 deg.C, heating at a rate of 5 deg.C/min, introducing methane and methane AThe flow rate of the alkane is 30sccm, and the temperature is kept for 60 min. And the graphene dendrite can be obtained in the deposition process after the methane is continuously decomposed.

(3) After the growth is finished, the furnace box of the tubular furnace is slid, the temperature is naturally reduced to 600 ℃, the temperature reduction rate is 150 ℃/min, and then the temperature is slowly reduced to the room temperature.

The morphology of the graphene dendrite prepared in example 1 on the side of the substrate is dendritic, and the SiO of the substrate₂The surface was free of dendritic graphene growth. The morphology of the graphene dendrite prepared in example 1 at the side of the substrate is shown in fig. 2.

Example 2

(2) Putting the dried silicon substrate in the step (1) into the outer wall of a quartz inner tube in a CVD tube furnace, vacuumizing the tube furnace, and keeping the vacuum pressure at 10^-5mbar, heating to 300 ℃, heating rate of 10 ℃/min, and closing the molecular pump; heating to 800 ℃, keeping the temperature for 30min, and introducing hydrogen for hydrogen etching, wherein the hydrogen flow is 25 sccm; slowly heating to 1050 ℃, heating at the speed of 5 ℃/min, introducing methane with the flow of 15sccm, and keeping the temperature for 30 min. And the graphene dendrite can be obtained in the deposition process after the methane is continuously decomposed.

After the growth is finished, the furnace box of the tubular furnace is slid, the temperature is naturally reduced to 600 ℃, the temperature reduction rate is 150 ℃/min, and then the temperature is slowly reduced to the room temperature.

As shown in FIG. 3, the graphene dendrite prepared under the conditions of example 2 is SiO on the substrate₂The surface is spherical, and crystal branches grow on the spherical surface. There is no dendritic growth on the sides of the substrate.

Example 3

(2) Putting the dried silicon substrate in the step (1) into the outer wall of a quartz inner tube in a CVD tube furnace, vacuumizing the tube furnace, and keeping the vacuum pressure at 10^-5mbar, heating to 300 ℃, heating rate of 10 ℃/min, and closing the molecular pump; heating to 800 ℃, keeping the temperature for 30min, and introducing hydrogen for hydrogen etching, wherein the hydrogen flow is 15 sccm; slowly heating to 1050 ℃, heating at the speed of 5 ℃/min, introducing methane with the flow rate of 25sccm, and keeping the temperature for 120 min. And the graphene dendrite can be obtained in the deposition process after the methane is continuously decomposed.

SiO of graphene dendrite on substrate prepared under the conditions of example 3₂The surface is spherical, and crystal branches grow on the spherical surface. The Si surface of the substrate is spherical, and crystal branches grow on the spherical surface. The side of the substrate has dendritic morphology. The topography of the Si surface of the substrate of example 3 is shown in fig. 4.

FIG. 4 shows a Raman spectrum of graphene dendrites on the insulating substrate prepared in example 3, from which SiO crystals can be obtained₂And the Raman spectrum of the sample of Si shows three characteristic peaks of graphene, and further proves that the substance is graphene.

Example 4

(2) Putting the dried silicon substrate in the step (1) into the outer wall of a quartz inner tube in a CVD tube furnace, vacuumizing the tube furnace, and keeping the vacuum pressure at 10^-5mbar, heating to 300 ℃, heating rate of 10 ℃/min, and closing the molecular pump; heating to 800 ℃, keeping the temperature for 30min, and introducing hydrogen for hydrogen etching, wherein the hydrogen flow is 15 sccm; slowly heating to 1050 ℃, heating at the rate of 5 ℃/min, introducing methane with the flow rate of 45sccm, and keeping the temperature for 40 min. And the graphene dendrite can be obtained in the deposition process after the methane is continuously decomposed.

The morphology of the graphene dendrite prepared under the condition on the side surface of the substrate is dendritic, and the SiO of the substrate₂The surface had no spherical graphene growth.

Example 5

(2) Putting the dried silicon substrate in the step (1) into the outer wall of a quartz inner tube in a CVD tube furnace, vacuumizing the tube furnace, and keeping the vacuum pressure at 10^-5mbar, heating to 300 ℃, heating rate of 10 ℃/min, and closing the molecular pump; heating to 800 ℃, keeping the temperature for 30min, and introducing hydrogen for hydrogen etching, wherein the hydrogen flow is 15 sccm; slowly heating to 1050 ℃, heating at the speed of 5 ℃/min, introducing methane with the flow rate of 60sccm, and keeping the temperature for 60 min. And the graphene dendrite can be obtained in the deposition process after the methane is continuously decomposed.

SiO of graphene dendrite prepared under the conditions of example 5 on a substrate₂The surface is spherical, and crystal branches grow on the spherical surface. There is no dendritic growth on the sides of the substrate.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing graphene dendrites on an insulating substrate is characterized in that: the method comprises the following specific steps:

1) cleaning and blow-drying the insulating substrate;

2) putting the dried substrate in the step 1) into a CVD (chemical vapor deposition) tube furnace, vacuumizing the tube furnace, heating to 200-300 ℃, introducing hydrogen, and etching the surface of the substrate at constant temperature when the temperature is increased to 800-900 ℃;

4) stopping introducing gas after growth is finished, cooling to 700-800 ℃, and naturally cooling to room temperature to obtain graphene dendrites;

in the step 1), the insulating substrate is a silicon wafer, and the thickness of the silicon wafer is 400-600 mu m; the surface of the silicon chip is amorphous SiO₂Layer of said SiO₂The thickness of the layer is 100-400 nm; SiO 2₂The surface of the layer is polished, and the surface of the Si is not polished.

2. The method of claim 1, wherein: the thickness of the silicon wafer is 450-550 mu m.

3. The method of claim 1, wherein: the SiO₂The thickness of the layer was 200-350 nm.

4. The method of claim 1, wherein: in the step 1), a chemical cleaning agent is adopted for ultrasonic cleaning, and chemical cleaning agents of acetone, ethanol and deionized water are sequentially adopted for cleaning for 8-12 min.

5. The method of claim 1, wherein: the vacuum degree and the pressure in the CVD tube furnace in the step 2) are 10^-5～10^-4mbar。

6. The method of claim 1, wherein: in the step 2), the heating rate of heating to 200-300 ℃ is 8-12 ℃/min, and the heating rate of heating to 800-900 ℃ is 8-12 ℃/min; in the step 2), the purity of the hydrogen is more than 99.9%, and the hydrogen flow is 15-25 sccm; the time for constant-temperature etching in the step 2) is 30-60 min.

7. The method of claim 6, wherein: the hydrogen flow in the step 2) is 15-20 sccm.

8. The method of claim 6, wherein: the time for constant-temperature etching in the step 2) is 30-40 min.

9. The method of claim 1, wherein: and 3) raising the temperature to 1050-1080 ℃ in the step 3), wherein the temperature raising rate is 4-6 ℃/min, the temperature is kept for 30-120 min, and the pressure is the same as that in the step 2).

10. The method of claim 9, wherein: and (3) keeping the temperature constant for 100-120 min.

11. The method of claim 1, wherein: the carbon source introduced in the step 3) is methane, the purity of the methane is more than 99.9%, and the flow rate of the methane is 15-60 sccm; the ratio of the introduced methane to the introduced hydrogen is 2: 3-4: 1.

12. The method of claim 11, wherein: the flow rate of the methane in the step 3) is 25-40 sccm.

13. The method of claim 1, wherein: the cooling rate of the temperature in the step 4) to 700-800 ℃ is 100-200 ℃/min.

14. The method of making a graphene dendrite on an insulating substrate of any one of claims 1-13 produces a graphene dendrite that grows on an insulating substrate.

15. Use of the graphene dendrite grown on an insulating substrate of claim 14 for the preparation of a microelectronic device.