CN113089094A

CN113089094A - Method for preparing double-layer single crystal graphene

Info

Publication number: CN113089094A
Application number: CN202110215730.3A
Authority: CN
Inventors: 徐小志; 梁智华; 曾凡凯; 王然; 唐志列
Original assignee: South China Normal University
Current assignee: South China Normal University
Priority date: 2021-02-26
Filing date: 2021-02-26
Publication date: 2021-07-09
Anticipated expiration: 2041-02-26
Also published as: CN113089094B

Abstract

The invention relates to a method for preparing double-layer single crystal graphene, which comprises the following steps: 1) placing a carbon-containing compound and a copper foil in a corundum box, and then placing the corundum box in a vapor deposition furnace; 2) introducing argon and hydrogen into the vapor deposition furnace, and heating the vapor deposition furnace to a high temperature of 1030-1045 ℃; 3) maintaining the temperature of the vapor deposition furnace, increasing the introduction amount of hydrogen, and annealing the copper foil; 4) introducing methane into the vapor deposition furnace, reducing the introduction amount of hydrogen, and starting the growth process of the double-layer single crystal graphene on the copper foil; 5) and after the growth of the double-layer single crystal graphene is finished, stopping introducing methane, and naturally cooling the vapor deposition furnace to room temperature in the atmosphere of hydrogen and argon. The method optimizes the growth of the double-layer graphene in a simple and convenient manner, grows the high-quality double-layer single crystal graphene, and has the advantages of simple steps and easily controlled preparation conditions.

Description

Method for preparing double-layer single crystal graphene

Technical Field

The invention relates to the technical field of material preparation, in particular to a method for preparing double-layer single crystal graphene.

Background

Graphene is a two-dimensional lattice structure formed by arranging carbon atoms in a hexagonal manner, has a thickness of about 0.335nm, is thin, and is very firm and hard. As a simple substance, graphene has a faster speed of transferring electrons at room temperature than many conductors and semiconductors; and the theoretical specific surface area of the graphene is up to 2630m²Per g, is a very potential energy storage active material. Graphene materials have unique physical properties and wide application prospects, so that the graphene materials are widely concerned and researched in recent years.

The double-layer graphene consists of two carbon atom layers, and due to the coupling effect between the atom layers, a band gap appears in an energy band structure, so that the graphene has a wide application prospect in the field of photoelectron. Double-layer graphene with different stacking directions has considerable application potential due to its unique electronic, optical and mechanical properties. For example, AB-stacked double-layer graphene (60 ° stack orientation angle) has been used in the fabrication of devices such as tunnel field effect transistors, high-switching-ratio digital transistors, tunable laser diodes, and infrared laser detectors due to its tunable band structure and high mobility.

At present, when graphene is prepared by a chemical vapor deposition method, after the self-limiting effect of catalyst copper is overcome, double-layer graphene grows on the basis of single-layer graphene, but at high temperature, black quartz particles are easily generated by a quartz tube of a vapor deposition furnace and fall on the surfaces of copper foil and graphene, particle impurities easily form nucleation sites, so that the growth orientation of single-layer and double-layer graphene domains is inconsistent, and high-quality double-layer single-crystal graphene cannot grow.

Disclosure of Invention

Based on this, the invention aims to provide a method for preparing double-layer single crystal graphene, which optimizes the growth of the double-layer graphene in a simple and convenient manner to grow the high-quality double-layer single crystal graphene and has the advantages of simple steps and easily controlled preparation conditions.

The technical scheme adopted by the invention is as follows:

a method for preparing double-layer single crystal graphene comprises the following steps:

1) placing a carbon-containing compound and a copper foil in a corundum box, and then placing the corundum box in a vapor deposition furnace;

2) introducing argon and hydrogen into the vapor deposition furnace, and heating the vapor deposition furnace to a high temperature of 1030-1045 ℃;

3) keeping the temperature of the vapor deposition furnace at high temperature 1030-1045 ℃, increasing the introduction amount of hydrogen, and annealing the copper foil;

4) introducing methane into the vapor deposition furnace, reducing the introduction amount of hydrogen, and starting the growth process of the double-layer single crystal graphene on the copper foil;

5) and after the growth of the double-layer single crystal graphene is finished, stopping introducing methane, closing a power supply of the vapor deposition furnace, and naturally cooling the vapor deposition furnace to room temperature in the atmosphere of hydrogen and argon.

According to the method, the copper foil and the carbon-containing compound are placed in an incompletely sealed corundum box which can allow gas to enter, then the corundum box and the corundum box are placed in a vapor deposition furnace together, quartz particles generated by a quartz tube are shielded by the corundum box, and the influence of impurities on the deposition process is reduced, so that high-quality double-layer single crystal graphene grows.

Moreover, the method adopts methane as a gas carbon source, and simultaneously adds a carbon-containing compound (graphite powder, PMMA and the like) as an additional carbon source. If only methane is used as a single carbon source, due to the self-limiting effect of copper, no exposed copper is used as a catalyst after the single-layer graphene grows, and therefore, an additional carbon source needs to be provided for growing the double-layer graphene. The added carbon-containing compound is put into the corundum box, so that the carbon source in the corundum box can be ensured to be sufficient, and the growth of the double-layer graphene is facilitated.

The method optimizes the growth of the double-layer graphene in a simple and convenient manner, can grow the high-quality double-layer single crystal graphene, and has the advantages of simple steps and easily controlled preparation conditions.

Further, in the step 1), a crucible containing the carbon-containing compound is placed at the front end in the corundum box.

Further, in step 1), the corundum box is placed on a quartz plate and then placed into the vapor deposition furnace together.

Further, in step 2), the temperature of the vapor deposition furnace is raised to 1030-1045 ℃ within 1 hour.

Further, in the step 2), the amount of hydrogen gas introduced was 10 sccm.

Further, in the step 3), the introduction amount of hydrogen gas was increased to 80sccm, and the annealing time was 40 minutes.

Further, in the step 4), the flow rate of methane was 1.5sccm, and the flow rate of hydrogen was reduced to 10 sccm.

Further, in step 4), the duration of the growth process is 60-240 minutes.

Further, the carbon-containing compound is graphene or polymethyl methacrylate.

Further, in the steps 1) to 5), the flow rate of argon gas was maintained at 500 sccm.

For a better understanding and practice, the invention is described in detail below with reference to the accompanying drawings.

Drawings

Fig. 1 is a schematic view of an apparatus for preparing double-layered single crystal graphene according to the present invention;

FIG. 2 is a schematic diagram showing the adjustment of the methane introduction amount, the hydrogen introduction amount and the temperature in examples 1 to 3;

FIG. 3 is a schematic diagram of the present invention for preparing double-layered single crystal graphene;

fig. 4 is an SEM image of the growth of a first and second layer of graphene;

FIG. 5 is an SEM image of a tiled first layer of graphene and a grown second layer of graphene;

fig. 6 is an SEM image of the confluent double-layered single crystal graphene;

fig. 7 is a raman spectrum of the double-layered single crystal graphene prepared in example.

Fig. 8 is an optical diagram of a double-layered single crystal graphene prepared by a comparative example.

Detailed Description

Referring to fig. 1, the method for preparing double-layered single crystal graphene according to the present invention includes the following steps:

1) the carbon-containing compound and the copper foil were placed in a closed but not completely sealed corundum box, which was allowed to enter gas, and the corundum box was placed in a vapour deposition furnace. Specifically, a crucible containing the carbon-containing compound, which may be graphite powder, PMMA, or the like, is placed at the front end (which is determined according to the direction of the gas flow in the vapor deposition furnace) in the corundum box. The corundum boxes are placed on a quartz plate and then placed together in the vapor deposition furnace. The vapor deposition furnace is matched equipment of a CVD system, and is specifically a tubular furnace.

2) Introducing argon and hydrogen into the vapor deposition furnace, and heating the vapor deposition furnace to a high temperature of 1030-1045 ℃; preferably, the temperature of the vapor deposition furnace is raised to 1030-1045 ℃ within 1 hour; the amount of hydrogen gas introduced was 10 sccm.

3) And keeping the temperature of the vapor deposition furnace at the high temperature of 1030-1045 ℃, increasing the introduction amount of hydrogen, and annealing the copper foil. Specifically, the amount of hydrogen gas introduced was increased to 80sccm, and the annealing time was 40 minutes.

In the step, hydrogen has the functions of reducing copper oxide and removing impurities at high temperature, and hydrogen with large flow can reduce the whole copper foil into fresh copper, reduce surface defects and remove surface impurities.

4) And introducing methane into the vapor deposition furnace, reducing the introduction amount of hydrogen, and starting the growth process of the double-layer single crystal graphene on the copper foil. Specifically, the flow rate of methane was 1.5sccm, the flow rate of hydrogen was reduced to 10sccm, and the duration of the growth process was 60 to 240 minutes.

In the step, since the hydrogen can etch the graphene besides reducing the copper, the too large amount of hydrogen can inhibit the growth of the graphene in the growth process, and even the graphene is etched cleanly, the introduction amount of the hydrogen needs to be properly reduced, and the growth rate of the graphene is limited by the hydrogen, so that the graphene is kept balanced in the etching process and the growth epitaxy process, and the high-quality graphene is grown.

Specifically, in the steps 1) to 6), the flow rate of argon gas is kept at 500 sccm.

Referring to fig. 3-6, fig. 3 is a schematic diagram of preparing a double-layer single crystal graphene according to the present invention; FIG. 4 is an SEM image of a first layer and a second layer of graphene grown in the preparation process of the invention, and isolated domain double-layer graphene can be seen from the SEM image, and the first layer and the second layer of graphene are in consistent orientation; fig. 5 is an SEM image of a confluent first layer of graphene and a second layer of graphene grown, from which it can be seen that the confluent first layer of graphene, the second layer of graphene is uniformly oriented; fig. 6 is an SEM image of the confluent double-layered single crystal graphene.

Example 1

As shown in fig. 1 and 2, this example prepares double-layer single crystal graphene according to the following steps:

1) preparing single crystal copper foil with proper size, such as copper (111), copper (112), copper (110) and the like, placing the copper foil in a corundum box, placing a crucible filled with graphite powder (providing an additional carbon source for growing double-layer graphene) at the front end in the corundum box, and covering the corundum box with a cover, wherein the corundum box is used for protecting the surface of the copper foil from being clean, and the structure of the corundum box is shown in figure 1.

2) The corundum box is placed on a quartz plate and then placed into a vapor deposition furnace of a CVD system, argon gas of 500sccm is introduced as protective gas, hydrogen gas of 10sccm is introduced, and the vapor deposition furnace is set to be heated to 1030 ℃ within one hour.

3) And annealing the copper foil when the temperature of the vapor deposition furnace reaches 1030 ℃, and simultaneously changing the introduction amount of hydrogen to 80sccm and the annealing time to 40 minutes.

4) Introducing 1.5sccm of methane as a growth carbon source, changing the introduction amount of hydrogen to 10sccm, and starting the growth process, wherein the duration of the growth process is 60 minutes.

5) And after the growth is finished, closing the methane, closing the power supply of the vapor deposition furnace, and naturally cooling the vapor deposition furnace to room temperature in the atmosphere of 10sccm hydrogen and 500sccm argon.

Example 2

4) Introducing 1.5sccm of methane as a growth carbon source, changing the introduction amount of hydrogen to 10sccm, and starting the growth process, wherein the duration of the growth process is 140 minutes.

Example 3

4) Introducing 1.5sccm of methane as a growth carbon source, changing the introduction amount of hydrogen to 10sccm, and starting the growth process, wherein the duration of the growth process is 240 minutes.

Comparative example 1

The comparative example prepared graphene as follows:

1) directly putting a single crystal copper foil and graphite powder into a vapor deposition furnace of a CVD system, putting the graphite powder at the front end of airflow, putting the copper foil behind the graphite powder and keeping a proper distance with the copper foil, introducing 500sccm argon as a protective gas, introducing 10sccm hydrogen, and setting the vapor deposition furnace to heat up to 1030 ℃ within one hour.

2) And annealing the copper foil when the temperature of the vapor deposition furnace reaches 1030 ℃, and simultaneously changing the introduction amount of hydrogen to 80sccm and the annealing time to 40 minutes.

3) Introducing 1.5sccm of methane as a growth carbon source, changing the introduction amount of hydrogen to 10sccm, and starting the growth process, wherein the duration of the growth process is 60 minutes.

4) And after the growth is finished, closing the methane, closing the power supply of the vapor deposition furnace, and naturally cooling the vapor deposition furnace to room temperature in the atmosphere of 10sccm hydrogen and 500sccm argon.

Comparative example 2

The comparative example prepared graphene as follows:

3) Introducing 1.5sccm of methane as a growth carbon source, changing the introduction amount of hydrogen to 10sccm, and starting the growth process, wherein the duration of the growth process is 140 minutes.

Test results

Examples 1-3 according to the method of the present invention, a copper foil and a carbon-containing compound were loaded into a corundum case and then placed into a vapor deposition furnace, to obtain double-layered single crystal graphene, whose SEM images are shown in fig. 4-6, and whose raman spectrum shown in fig. 7 indicates high quality; the optical diagram shown in fig. 8 is that in comparative examples 1-2, copper foil and carbon-containing compounds (graphite powder, PMMA, etc.) are directly placed in a vapor deposition furnace of a CVD system, and the grown double-layer graphene has impurities to affect growth orientation, so that large-area double-layer single-crystal double-layer graphene cannot be prepared. Therefore, the method provided by the invention introduces the corundum box to optimize the growth of graphene on the single crystal copper foil and isolate impurities, so that high-quality double-layer single crystal graphene is grown.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention.

Claims

1. A method for preparing double-layer single crystal graphene is characterized by comprising the following steps: the method comprises the following steps:

2. The method of claim 1, wherein: in the step 1), a crucible containing the carbon-containing compound is placed at the front end in the corundum box.

3. The method of claim 2, wherein: in the step 1), the corundum box is placed on a quartz plate and then is placed into the vapor deposition furnace together.

4. The method of claim 1, wherein: in the step 2), the temperature of the vapor deposition furnace is raised to 1030-1045 ℃ within 1 hour.

5. The method of claim 1, wherein: in the step 2), the introduction amount of the hydrogen gas is 10 sccm.

6. The method of claim 5, wherein: in the step 3), the introduction amount of the hydrogen is increased to 80sccm, and the annealing time is 40 minutes.

7. The method of claim 6, wherein: in the step 4), the introduction amount of methane was 1.5sccm, and the introduction amount of hydrogen was reduced to 10 sccm.

8. The method of claim 7, wherein: in step 4), the duration of the growth process is 60-240 minutes.

9. The method of claim 1, wherein: the carbon-containing compound is graphene or polymethyl methacrylate.

10. The method of claim 1, wherein: in the steps 1) to 5), the introduction amount of argon gas is kept at 500 sccm.