CN105483824A - Method for preparing monocrystal double-layer graphene - Google Patents

Abstract

The invention discloses a method for preparing single-crystal double-layer graphene, comprising the following steps: a) putting a copper catalyst into a reactor, and feeding a non-oxidizing gas into the reactor so that the non-oxidizing gas is full of reaction device, the copper catalyst is single crystal copper or polycrystalline copper or copper film; b) heating the copper catalyst to the target temperature, and then keeping the temperature constant for 30-120 minutes, the temperature range of the target temperature is: 1000 ° C ~ 1070 °C; c) then lower the temperature of the copper catalyst to reach 900 °C to 500 °C or keep the temperature constant. Single-crystal bilayer graphene was obtained on the surface of the copper catalyst. The invention utilizes an isothermal or non-isothermal atmospheric pressure chemical vapor deposition method to prepare large-size single-crystal double-layer graphene on a copper catalyst. The method is easy to operate, simple and easy to implement, and can be used for high-end electronic devices and integrated circuits.

Description

Method for preparing single crystal bilayer graphene

technical field

The invention relates to a method for preparing single-crystal double-layer graphene, which belongs to the technical field of graphene.

Background technique

At present, graphene is an ultra-thin single-atom two-dimensional material. Its unique physical structure endows it with excellent electrical, optical, and mechanical properties, making it sought after by researchers in various fields. Initially, graphene was prepared by micromechanical exfoliation of highly oriented pyrolytic graphite, and high-quality graphene with a mobility of up to 200,000V ^-1 S ^-1 was obtained. At present, the chemical vapor phase method is used to prepare graphene on the surface of transition metal substrate Ni or Cu, and square meter-scale single-layer, double-layer or multi-layer graphene can already be obtained.

The unique zero-bandgap dispersion relationship of single-layer graphene limits its application in logic switches and memories. In order to open the graphene band gap, people have adopted various methods, such as: cutting graphene film into graphene nanobelts or graphene nets, chemical doping or physical adsorption, using a uniaxial stress to stretch graphene, etc. . Although these methods can open the band gap of graphene, they seriously destroy the lattice structure of graphene and lose the excellent electrical properties of graphene, especially the carrier mobility of graphene is inevitably severely attenuated. Therefore, A new way to open the bandgap of graphene needs to be found. At this time, double-layer graphene came into people's sight. Bilayer graphene has a unique parabolic-like energy band structure, which can easily open the band gap under the action of an external electric field, making it attract more and more attention, and has been obtained from theoretical simulations and experimental operations. It has been verified that by adding a strong electric field in the vertical direction of bilayer graphene, a bandgap of ~250meV can be opened. Therefore, the preparation of large-area and high-quality bilayer graphene has become a hot spot in current research.

The polycrystalline graphene film prepared by general chemical vapor deposition method has a single crystal size of about several microns or tens of microns. The high density of grain boundaries in these polycrystalline graphene films leads to instability in the electronic properties of graphene. Although relevant studies say that polycrystalline graphene prepared by this chemical vapor deposition method has a high mobility comparable to that of exfoliated graphene, the overall transport properties of polycrystalline thin film graphene are still affected by defects at grain boundaries. Therefore, how to prepare large-scale single-crystal graphene is an important challenge for the integration of graphene-based electronic and optoelectronic devices.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a method for preparing single-crystal double-layer graphene. The present invention can prepare single-crystal bilayer graphene under mild conditions without using complicated high-vacuum bilayer graphene.

In order to solve the problems of the technologies described above, the technical solution of the present invention is a method for preparing single-crystal double-layer graphene, comprising the following steps:

a) putting the copper catalyst into the reactor, and passing non-oxidizing gas into the reactor, so that the non-oxidizing gas is filled with the reactor, and the copper catalyst is single crystal copper or polycrystalline copper or copper thin film;

b) heating the copper catalyst to the target temperature, and then keeping the temperature constant for 30-120 minutes, the temperature range of the target temperature being: 1000°C to 1070°C;

c) Continue to keep the temperature constant, and pass the non-oxidizing gas carrying the carbon source into the reactor, so that single-crystal double-layer graphene can be obtained on the surface of the copper catalyst.

The present invention also discloses another method for preparing single-crystal double-layer graphene, comprising the following steps:

a) putting the copper catalyst into the reactor, and passing non-oxidizing gas into the reactor, so that the non-oxidizing gas is filled with the reactor, and the copper catalyst is single crystal copper or polycrystalline copper or copper thin film;

b) heating the copper catalyst to the target temperature, and then keeping the temperature constant for 30-120 minutes, the temperature range of the target temperature being: 1000°C to 1070°C;

c) Then lower the temperature of the copper catalyst to 900°C to 500°C. During the above cooling process, a non-oxidizing gas carrying a carbon source is passed into the reactor, and a single crystal double layer can be obtained on the surface of the copper catalyst. Graphene.

Further, the carbon source described in step c) is methane and/or acetylene and/or polystyrene and/or coronene.

Further, in step c), for the gaseous carbon source, the gaseous carbon source and the non-oxidizing gas are fed into the reactor at the same time.

A method for introducing a solid carbon source is further provided. In step c), for the solid carbon source, the solid carbon source is placed at one end of the reactor where the gas flow is introduced, and a heating belt is used to heat the position of the solid carbon source, heating The temperature range is: 200°C-400°C.

Further in order to obtain pure graphene, after step c), also include step d), at first PMMA or PDMS are spin-coated on the substrate surface that grows graphene, and heating on heating stage, then put into ferric chloride Or copper sulfate or ammonium persulfate solution for 1-24 hours to remove copper, then wash with deionized water, dilute hydrochloric acid, isopropanol, dry, transfer to the target substrate, and finally use hot acetone to remove PMMA or PDMS layer.

After adopting the above technical scheme, the present invention utilizes isothermal or non-isothermal atmospheric pressure chemical vapor deposition to prepare large-scale single-crystal double-layer graphene on a copper catalyst. This method is easy to operate, simple, and can be used for high-end electronic devices and integrated circuit; in addition, the single-crystal double-layer graphene prepared by the non-isothermal method of the present invention has the advantages of larger size and fewer defects compared with the single-crystal double-layer graphene prepared by the isothermal method.

Description of drawings

Fig. 1 is the schematic diagram of the reactor when carbon source of the present invention is gaseous carbon source;

Fig. 2 is the schematic diagram of the reactor when the carbon source of the present invention is a solid carbon source;

Fig. 3 is the scanning electron microscope photograph of the monocrystalline bilayer graphene prepared by embodiment one;

Fig. 4 is the scanning electron micrograph of the monocrystalline bilayer graphene prepared by embodiment two;

Fig. 5 is the optical micrograph of the monocrystalline double-layer graphene prepared by embodiment three;

Fig. 6 is the scanning electron micrograph of the monocrystalline bilayer graphene prepared by embodiment three;

Fig. 7 is the Raman spectrum corresponding to selecting different points on the single-crystal double-layer graphene prepared by embodiment three;

Fig. 8 is the transmission electron micrograph of the single-crystal double-layer graphene edge layer structure prepared by embodiment three;

Fig. 9 is a selected area electron diffraction photo of the single crystal in Fig. 8;

Fig. 10 is the selected area electron diffraction intensity corresponding to Fig. 9;

Fig. 11 is the scanning electron micrograph of the monocrystalline bilayer graphene prepared in embodiment four;

Fig. 12 is the scanning electron micrograph of the monocrystalline bilayer graphene prepared in embodiment five

In the figure, No. 1 and No. 1 inlet pipes, No. 2 and No. 2 inlet pipes, 3. Carbon source, 4. Copper catalyst, 5. Reactor.

detailed description

In order to make the content of the present invention more clearly understood, the present invention will be further described in detail below based on specific embodiments and in conjunction with the accompanying drawings.

Embodiment one:

As shown in Figure 1, the carbon source is methane, of course it can also be acetylene, the copper catalyst is single crystal copper foil, the reactor is a quartz tube, the No. 1 tube is an argon tube, the No. 2 tube is a hydrogen tube, and the No. 3 tube is methane trachea.

A method for preparing single-crystal double-layer graphene, comprising the following steps:

a) Place the single crystal copper foil in the middle of a clean quartz tube, evacuate the quartz tube, then pass in argon gas, evacuate, pass in hydrogen gas, evacuate again, and repeat three times to remove the Air, then pass 500-1000sccm argon-hydrogen mixed gas into the quartz tube;

b) heating the single crystal copper foil so that the temperature in the central area of the quartz tube reaches 1000°C, and then keeping the temperature constant for 60 minutes, annealing the surface of the single crystal copper foil;

c) Continue to keep the temperature at 1000°C constant, pass methane into the argon-hydrogen mixed gas, and pass it into the quartz tube together, the reaction starts, and carbon is deposited on the surface of the single-crystal copper foil to form single-crystal double-layer graphene.

After the reaction was carried out for 100 minutes, the feeding of methane was stopped, while the furnace cover was opened, the electric furnace was turned off, and the argon-hydrogen mixed gas was continued to be fed until it was cooled to room temperature. Of course, it could also be slowly cooled with the furnace.

As shown in Figure 3, it can be seen from the figure that the hexagonal single crystal structure is illustrated as graphene.

Embodiment two:

As shown in Figure 1, the carbon source is methane, of course it can also be acetylene, the copper catalyst is single crystal copper foil, the reactor is a quartz tube, the No. 1 tube is an argon tube, the No. 2 tube is a hydrogen tube, and the No. 3 tube is methane trachea.

A method for preparing single-crystal double-layer graphene, comprising the following steps:

a) Place the single crystal copper foil in the middle of a clean quartz tube, evacuate the quartz tube, then pass in argon gas, evacuate, pass in hydrogen gas, evacuate again, and repeat three times to remove the Air, then pass 500-1000sccm argon-hydrogen mixed gas into the quartz tube;

b) heating the single crystal copper foil so that the temperature in the central area of the quartz tube reaches 1000°C, and then keeping the temperature constant for 90 minutes, annealing the surface of the single crystal copper foil;

c) Slowly cool down the central area of the quartz tube to 500°C. During the cooling process, feed methane into the argon-hydrogen mixed gas, and pass it into the quartz tube together. The reaction begins, and carbon is deposited on the surface of the single crystal copper foil. Generate graphene.

After the reaction was carried out for 100 minutes, the feeding of methane was stopped, while the furnace cover was opened, the electric furnace was turned off, and the argon-hydrogen mixed gas was continued to be fed until it was cooled to room temperature. Of course, it could also be slowly cooled with the furnace.

As shown in Figure 4, it can be seen from the figure that the hexagonal single crystal structure is illustrated as graphene.

Embodiment three:

As shown in Figure 1, the carbon source is methane, the copper catalyst is polycrystalline copper foil, the reactor is a quartz tube, the No. 1 tube is an argon tube, the No. 2 tube is a hydrogen tube, and the No. 3 tube is a methane gas tube.

A method for preparing single-crystal double-layer graphene, comprising the following steps:

a) The polycrystalline copper foil is ultrasonically cleaned with deionized water, ethanol, acetone, and isopropanol in sequence, then blown dry with nitrogen, and then placed in the middle of the quartz tube of the chemical vapor deposition system, vacuumizes the quartz tube, and blows it to the quartz tube. Introduce argon and hydrogen into the tube to fill the reactor with argon-hydrogen mixed gas, repeat vacuuming three times to completely remove the air in the tube, and then inject argon-hydrogen mixed gas into the quartz tube again;

b) Heating the polycrystalline copper foil so that the temperature in the central area of the quartz tube reaches 1070°C. When the temperature in the central area of the quartz tube reaches 1070°C, feed 400 sccm argon into the quartz tube and feed 50 sccm hydrogen as reduction Inert gas, and maintain the temperature at this time for 30 minutes, and anneal the surface of the polycrystalline copper foil;

c) Then lower the temperature of the polycrystalline copper foil to 900°C. During the cooling process in which the temperature in the central area of the tube is lowered from 1070°C to 900°C, methane is introduced into the argon-hydrogen mixed gas, and the quartz In the tube, single-crystal double-layer graphene can be obtained on the surface of polycrystalline copper foil.

After step c), also include step d), at first PMMA is spin-coated on the surface of the polycrystalline copper foil that grows graphene, and heating on heating platform, puts into ferric chloride solution corrosion 24 hours then and removes copper , can also be a copper sulfate solution, or an ammonium persulfate solution, and then wash it with deionized water, dilute hydrochloric acid, and isopropanol in sequence, dry it, transfer it to a 300nm thick silicon dioxide/silicon substrate, and finally use it Hot acetone removes the PMMA layer.

Fig. 5 is an optical micrograph of the product on a silicon wafer, and Fig. 6 is a scanning electron micrograph of the product, from which the hexagonal structure and uniform contrast of the product can be observed, indicating that it is a single crystal graphene. At the same time, the Raman spectrum in Figure 7, the transmission electron micrograph in Figure 8, the selected area electron diffraction photo in Figure 9, and the selected area electron diffraction intensity in Figure 10 all prove that it is a single-crystal double-layer graphene.

Embodiment four:

As shown in Figure 2, the carbon source is coronene, the copper catalyst is polycrystalline copper foil, the reactor is a quartz tube, the No. 1 tube is an argon tube, and the No. 2 tube is a hydrogen tube.

A method for preparing single-crystal double-layer graphene, comprising the following steps:

a) Put the clean polycrystalline copper foil into the middle of the quartz tube of the chemical vapor deposition system, evacuate the quartz tube, and feed argon and hydrogen into the quartz tube to fill the reactor with the mixed gas of argon and hydrogen, repeat three times Vacuumize to completely remove the air in the tube, and then pass the argon-hydrogen mixed gas into the quartz tube again;

b) Heat the polycrystalline copper foil so that the temperature in the central area of the quartz tube reaches 1050°C. When the temperature in the central area of the quartz tube reaches 1050°C, feed 400 sccm argon into the quartz tube and feed 50 sccm hydrogen as a reduction Inert gas, and maintain the temperature at this time for 40 minutes, and anneal the surface of the polycrystalline copper foil;

c) Then cool down the polycrystalline copper foil to make it reach 600°C. During the cooling process in which the temperature in the central area of the tube is lowered from 1050°C to 600°C, use a heating belt to heat the part where the coronene is located so that the temperature rises to At 200°C, sufficient carbon source is provided for graphene growth, and single-crystal double-layer graphene can be obtained on the surface of polycrystalline copper foil.

Figure 11 is a scanning electron micrograph of the product, from which a two-dimensional film-like hexagonal structure with wrinkled stripes can be observed, indicating that it is a single-crystal double-layer graphene.

Embodiment five:

As shown in Figure 2, the carbon source is polystyrene, the copper catalyst is a copper film deposited on a silicon wafer, the reactor is a quartz tube, the No. 1 tube is an argon tube, and the No. 2 tube is a nitrogen tube.

The copper thin film can be deposited on the substrate by chemical vapor deposition, physical vapor deposition, vacuum thermal evaporation, magnetron sputtering, plasma enhanced chemical vapor deposition and printing using a pure copper target. The substrate is then placed into a quartz tube of a chemical vapor deposition system.

A method for preparing single-crystal double-layer graphene, comprising the following steps:

a) Put the copper thin film deposited on the silicon wafer into the middle of the quartz tube, vacuumize the quartz tube, and feed argon and nitrogen into the quartz tube to fill the reactor with argon-hydrogen mixed gas, and repeat the vacuum pumping three times. The air in the tube is completely removed, and then argon-nitrogen mixed gas is introduced into the quartz tube again;

b) Heating the copper film deposited on the silicon wafer so that the temperature of the central area of the quartz tube reaches 1030°C, when the temperature of the central area of the quartz tube reaches 1030°C, feed argon and nitrogen into the quartz tube, and keep this The temperature at the time was 120 minutes, and the copper film was annealed;

c) Then lower the temperature of the copper film deposited on the silicon wafer to 800°C, and during the cooling process in which the temperature in the central area of the tube is lowered from 1030°C to 800°C, heat the position of the polystyrene with a heating belt, Raise the temperature to 400°C to provide enough carbon source for the growth of graphene, and obtain single-crystal double-layer graphene on the surface of the copper film.

After step c), also include step d), at first PDMS is spin-coated on the copper thin film surface that grows graphene, and heating on heating platform, then puts into copper sulfate solution and corrodes for 12 hours to remove copper, after that, successively use Wash with deionized water, dilute hydrochloric acid, and isopropanol, dry, transfer to the target substrate, and finally use hot acetone to remove the PDMS layer.

Figure 12 is a scanning electron micrograph of the product, from which a two-dimensional film-like hexagonal structure with wrinkled stripes can be observed, which is illustrated as graphene.

The present invention utilizes isothermal or non-isothermal atmospheric pressure chemical vapor deposition to prepare large-size single-crystal double-layer graphene on copper catalysts. The method is easy to operate, simple and easy to implement, and can be used for high-end electronic devices and integrated circuits; in addition, the present invention Compared with the single-crystal bilayer graphene prepared by isothermal method, the single-crystal bilayer graphene prepared by non-isothermal method has the advantages of larger size and fewer defects.

The specific embodiments described above have further described the technical problems, technical solutions and beneficial effects solved by the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the present invention. 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 (7)

1. prepare a method for monocrystalline bilayer graphene, comprise the following steps:

A) copper catalyst is put into reactor, and pass into non-oxidizing gas in reactor, make non-oxidizing gas be full of reactor, described copper catalyst is single crystal Cu or polycrystalline copper or Copper thin film;

B) copper catalyst is heated to target temperature, then keep homo(io)thermism 30-120 minute, the temperature range of described target temperature is: 1000 DEG C ~ 1070 DEG C;

C) continue to keep homo(io)thermism, the non-oxidizing gas carrying carbon source is passed in reactor, monocrystalline bilayer graphene can be obtained on copper catalyst surface.

2. prepare a method for monocrystalline bilayer graphene, comprise the following steps:

A) copper catalyst is put into reactor, and pass into non-oxidizing gas in reactor, make non-oxidizing gas be full of reactor, described copper catalyst is single crystal Cu or polycrystalline copper or Copper thin film;

B) copper catalyst is heated to target temperature, then keep homo(io)thermism 30-120 minute, the temperature range of described target temperature is: 1000 DEG C ~ 1070 DEG C;

C) then carrying out cooling to copper catalyst makes it reach 900 DEG C ~ 500 DEG C, in above-mentioned temperature-fall period, passes in reactor by the non-oxidizing gas carrying carbon source, can obtain monocrystalline bilayer graphene on copper catalyst surface.

3. the method preparing monocrystalline bilayer graphene according to claim 1 and 2, is characterized in that: step c) described in carbon source be methane and/or acetylene and/or polystyrene and/or coronene.

4. the method preparing monocrystalline bilayer graphene according to claim 3, is characterized in that: in step c) in, for gaseous carbon sources, gaseous carbon sources and non-oxidizing gas pass in reactor simultaneously.

5. the method preparing monocrystalline bilayer graphene according to claim 4, it is characterized in that: in step c) in, for solid carbon source, solid carbon source is placed on one end that reactor passes into air-flow, and with heating zone, position, solid carbon source place is heated, the temperature range of heating is: 200 DEG C-400 DEG C.

6. the method preparing monocrystalline bilayer graphene according to claim 1, it is characterized in that: in step c) after, also comprise steps d), first PMMA or PDMS is spin-coated on the substrate surface that growth has Graphene, and heat on warm table, then put into iron(ic) chloride or copper sulfate or ammonium persulfate solution and corrode 1-24 hour removing copper, clean with deionized water, dilute hydrochloric acid, Virahol successively afterwards, dry, transfer in target substrate, finally use hot acetone removing PMMA or PDMS layer.

7. the method preparing monocrystalline bilayer graphene according to claim 1 and 2, is characterized in that: described non-oxidizing gas is argon gas and/or nitrogen and/or hydrogen.