CN108203090B

CN108203090B - Preparation method of graphene

Info

Publication number: CN108203090B
Application number: CN201611170148.5A
Authority: CN
Inventors: 汪爱英; 刘盼盼; 张栋; 郭婷; 李汉超; 柯培玲
Original assignee: Ningbo Institute of Material Technology and Engineering of CAS
Current assignee: Ningbo Institute of Material Technology and Engineering of CAS
Priority date: 2016-12-16
Filing date: 2016-12-16
Publication date: 2021-03-26
Anticipated expiration: 2036-12-16
Also published as: CN108203090A

Abstract

The invention provides a preparation method of graphene. The method combines a cathode vacuum arc deposition technology, an electron beam evaporation technology and a vacuum annealing technology, and by optimizing process parameters, firstly an amorphous carbon film with high sp3 content is obtained by deposition on the surface of a substrate, then a catalyst film is evaporated on the surface of the substrate by electron beams, and finally the substrate is annealed at 450-500 ℃ to diffuse and separate out carbon elements to the surface of the catalyst film, so that the structure of the catalyst film is converted into a graphene structure, and thus few-layer or multi-layer graphene is formed. Compared with the existing graphene preparation process, the method has the advantages of simple and feasible process, low annealing temperature and cost reduction; the used carbon source is not gas but solid, and the number of layers of the graphene can be controlled by controlling the thickness of the carbon source, so that the controllable preparation of the graphene is realized.

Description

Preparation method of graphene

Technical Field

The invention relates to the technical field of graphene, in particular to a preparation method for converting amorphous carbon into graphene.

Background

The graphene is represented by sp²The hybridized carbon atoms are bonded to form a two-dimensional atomic crystal with a hexagonal honeycomb crystal structure. Graphene is a basic unit constituting carbon nanotubes, fullerenes, graphite bulk materials, and the like.

In 2004, Novoselov and geom et al, scientists in the united kingdom, used micromechanical exfoliation to obtain stand-alone high quality graphene and found that graphene has unique electronic properties, raising the hot tide of graphene research. The graphene has high carrier mobility, high thermal conductivity, high light transmittance, good chemical stability and the like, and has wide application prospects in various fields such as electronic devices, transparent electrode materials, energy storage materials, functional composite materials and the like.

The preparation method of the graphene mainly comprises a mechanical stripping method, a silicon carbide epitaxial growth method, a graphite oxide reduction method, a chemical vapor deposition method and the like. The graphene prepared by the mechanical stripping method has high quality and simple process, and the size reaches the millimeter level, but the method has long preparation time and high cost, and the number of layers and the size of the graphene are uncontrollable and difficult to be widely applied; the silicon carbide epitaxial growth method can be used for preparing large-size graphene, but the silicon carbide is expensive and has harsh preparation conditions, and ultrahigh vacuum and high temperature of over 1200 ℃ are required; graphene prepared by a graphite oxide reduction method has many defects; at present, the most applied method is Chemical Vapor Deposition (CVD), and large-scale growth can be realized, but the carbon source of the method is carbon-containing gas, high-temperature decomposition (the temperature is 900-1000 ℃) is needed, and more influencing factors such as air pressure, flow and the like exist.

Disclosure of Invention

Aiming at the technical current situation, the invention provides a preparation method of graphene, which is simple and feasible and has low cost.

The technical scheme of the invention is as follows: a preparation method of graphene comprises the following steps:

step 1: cleaning the surface of the substrate Si and then drying;

step 2: adopting a cathode vacuum arc deposition device, putting a substrate Si into a vacuum cavity, wherein a target material is a high-purity graphite target, and an amorphous carbon film with the thickness of 2-30 nm is deposited on the surface of the substrate Si, and the deposition conditions are as follows: the vacuum degree of the vacuum chamber for film deposition reaches 3.0 multiplied by 10^-3Introducing argon gas of 15-25 sccm and arc flow of 55-60A below Pa, applying pulse negative bias of-300V-350V to the substrate, pulse frequency of 330-370 kHz, pulse width of 0.9-1.2 mus, and deposition time of 1-10 min;

and step 3: washing the amorphous carbon film on the surface of the substrate Si by using a high-purity nitrogen gun, and preparing a metal catalyst film on the surface of the amorphous carbon film by adopting an electron beam evaporation technology, wherein the film coating conditions are as follows: vacuum-pumping to 2 × 10^-3Below Pa, electron gun power 8 ℃20W, deposition rate

/s；

And 4, step 4: vacuum-pumping is carried out in a vacuum annealing furnace to ensure that the vacuum degree in the furnace reaches 3.0 multiplied by 10^-2And (4) raising the temperature in the furnace to 450-500 ℃ below Pa, then putting the Si/amorphous carbon/metal catalyst sample, preserving the temperature for 15-20 min, and then air-cooling.

The purity of the high-purity graphite target is preferably more than 99.999%.

The cathode vacuum arc deposition device is a device for depositing a film by using a cathode vacuum arc deposition method. The cathodic vacuum arc deposition method is a method of forming a thin film on the surface of a substrate by attracting plasma generated from a vacuum arc evaporation source to the substrate by means of a negative bias voltage or the like. The cathode vacuum arc deposition method has the advantages of high ionization rate, high ion energy, low deposition temperature, high deposition rate, good film-substrate combination and the like.

The cathode vacuum arc source film deposition device comprises a cathode vacuum arc evaporation source, a film deposition vacuum cavity, a vacuum pumping device and a gas channel for introducing inert gas. Wherein the cathode vacuum arc evaporation source evaporates a cathode target by vacuum arc discharge, thereby generating plasma containing a cathode target material.

In the step 1, as a preferable embodiment, the surface of the substrate Si is cleaned by ultrasonic waves in an alcohol solution.

In the step 2, the sp3 content in the amorphous carbon film obtained by deposition by using a cathode vacuum arc deposition technology is higher than 80%.

In the step 2, the deposition rate of the amorphous carbon film is preferably 1-3 nm/min.

In the step 4, the preferable metal catalyst is copper, nickel and the like, and the preferable thickness of the catalyst is 70-100 nm.

In order to reduce the deposition of macro-large particles on the surface of a substrate, reduce the roughness of a film and improve the surface smoothness, preferably, the cathode vacuum arc source film deposition device further comprises a magnetic filtering part which consists of a tube body and a magnetic field generating device arranged on the outer periphery of the tube body, the tube body comprises a tube body inlet end face and a tube body outlet end face, at least one bent tube is arranged between the tube body inlet end face and the tube body outlet end face, and the included angle between the axes of the tube body on the two sides of the bent tube is 135 degrees. More preferably, a direct current positive bias is applied to the bend pipe, and the direct current positive bias is preferably 5 to 10V. The roughness Ra of the amorphous carbon film obtained by deposition by using the bending magnetic filtering cathode vacuum arc deposition device is less than 0.2 nm.

In summary, the invention combines a cathode vacuum arc deposition technology, an electron beam evaporation technology and a vacuum annealing technology, and optimizes process parameters, firstly an amorphous carbon film with high sp3 content is deposited on the surface of a substrate, then a catalyst film is evaporated on the surface of the substrate by electron beams, and finally carbon elements are diffused and separated out on the surface of the catalyst film by annealing heat treatment, and the structure of the catalyst film is converted into a graphene structure, so that few-layer or multi-layer graphene is formed. Compared with the existing graphene preparation process, the preparation method has the following beneficial effects:

(1) the process is simple and easy to implement and low in cost;

(2) the used carbon source is not gas but solid, and the surface smoothness of the amorphous carbon film can be improved by optimizing the cathode vacuum arc deposition device, so that the roughness of the amorphous carbon film is less than 0.2 nm; in addition, the deposition rate in the cathode vacuum arc deposition technology can be as low as 1-3 nm/min, and the number of layers of the generated graphene can be controlled by controlling the deposition rate and the thickness of the carbon film;

(3) by optimizing the process parameters in the cathode vacuum arc deposition, the amorphous carbon film has high sp3 content and low annealing temperature in annealing treatment, and can obtain graphene at low annealing temperature of less than 500 ℃, compared with the CVD method at high temperature of more than 1000 ℃, the generation temperature is greatly reduced, the cost is reduced, and the development of the controllable preparation technology of graphene with low cost and large area is promoted.

Drawings

FIG. 1 is a schematic structural view of a cathode vacuum arc source thin film deposition apparatus in example 1 of the present invention;

FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1;

FIG. 3 is a Raman spectrum of a sample before annealing in example 1 of the present invention;

FIG. 4 is a Raman spectrum of a sample of example 1 of the present invention after annealing;

fig. 5 is a raman spectrum of the sample in comparative example 1 after annealing.

Detailed Description

The present invention will be described in further detail with reference to the following embodiments, which are not intended to limit the invention, but are to facilitate understanding of the invention.

The reference numerals in fig. 1-2 are: a cathode 1, an anode 2, an elbow 3, an arc source coil 4, a pulling coil 5, a bending coil 6, an output coil 7, a scanning coil 8, a permanent magnet 9, a barrier plate 10, a threaded rod 11, a trigger electrode 12, a gas passage 13, a pneumatic valve 14, an observation window 15, an insulating washer 16, a stainless steel ring 17, a stainless steel ring 18, a large plate 19, a small plate 20, an air exhaust port 21, a bias power supply 22, a film deposition vacuum chamber 23, an air exhaust port 24, an insulating washer 25, a stainless steel ring 26, a stainless steel ring 27, an insulating washer 28, a stainless steel ring 29, a stainless steel ring 30, an arc source coil dc power supply 31, an arc pulse power supply 32, a pulling coil dc power supply 33, a bending coil dc power supply 34, an output coil dc power supply 35, a scanning coil ac power supply 36, a bias power supply 37, a cathode arc vacuum evaporation source 39, a first elbow 40, and a second elbow 41.

Example 1:

step 1: the substrate Si is cleaned by ultrasonic wave in alcohol solution and then dried.

Step 2: deposition of amorphous carbon films

The film deposition device using the cathode vacuum arc source is structurally shown in figures 1 and 2 and comprises a cathode vacuum arc evaporation source 39, a magnetic filtering part and a film deposition vacuum cavity 23 provided with a substrate, which are connected in sequence in a sealing way.

The cathode vacuum arc evaporation source 39 includes a trapezoidal columnar cathode 1, a cylindrical ring anode 2 coaxial with the cathode 1, a trigger electrode 12 provided between the cathode 1 and the anode 2 for exciting an arc, and a pneumatic valve 14 for the trigger electrode 12. In this embodiment, the trigger electrode 12 is an arc needle. The permanent magnet 9 and the anode 2 are coaxially arranged on two sides of the cathode 1, the permanent magnet 9 is connected with a threaded rod 11, and the distance between the permanent magnet 9 and the cathode 1 can be adjusted by screwing in and out the threaded rod 11. The cathode vacuum arc evaporation source 39 is provided with an arc source coil 4 and an arc source coil power supply 31 connected thereto at its outer periphery. In addition, the cathode vacuum arc evaporation source 39 further includes a gas passage 13 and an observation window 15.

The magnetic filtering part comprises a pipe body and a magnetic field generating device arranged on the periphery of the outside of the pipe body, the pipe body comprises a pipe body inlet end face and a pipe body outlet end face, at least one bent pipe 3 is arranged between the pipe body inlet end face and the pipe body outlet end face, and an included angle between the axes of the pipe bodies on two sides of the bent pipe 3 is 135 degrees. The body is the stainless steel return bend 3 that has interlayer water-cooling in this embodiment, and 3 cross sections of return bend are circular, and return bend 3 comprises two parts: a first bend 40 with an angle of 135 degrees and a second bend 41 with an angle of 135 degrees, wherein the stainless steel ring 26 at the outlet of the first bend 40 is tightly connected with the stainless steel ring 27 at the inlet of the second bend 41 through an insulating gasket 25. The pipe wall of the elbow is provided with an electromagnetic coil group and an electromagnetic coil power supply for supplying power to the electromagnetic coil group, and the electromagnetic coil power supply comprises a dragging coil 5 arranged at the inlet of the pipe body, a turning coil 6 arranged at the elbow 3 of the pipe body and an output coil 7 arranged at the outlet of the pipe body. The pull-down coil 5 is connected to a pull-down coil dc power supply 33, the bend coil 6 is connected to a bend coil dc power supply 34, and the output coil 7 is connected to an output coil dc power supply 35.

The film deposition vacuum chamber 23 includes a work carrier at the middle bottom, on which a large plate 19 revolvable and a small plate 20 rotatable on the large plate 19 are formed. When the film deposition is carried out, a workpiece needing to deposit the film is fixed on the small disc 20, and the small disc can rotate to improve the uniformity of the film deposited on the surface of the workpiece. To vary the energy of the deposited ions, a negative bias can be applied to the workpiece by a bias power supply 22. In addition, the film deposition vacuum chamber 23 further includes a suction port 21 and a discharge port 24, and the suction port 21 is connected to a vacuum pumping device of the film deposition apparatus of the cathode vacuum arc source.

The stainless steel ring 17 on the cathode vacuum arc evaporation source 39 is tightly connected with the stainless steel ring 18 on the inlet of the elbow pipe through an insulating gasket 16, and the stainless steel ring 29 on the outlet of the second elbow pipe 41 is tightly connected with the stainless steel ring 30 on the inlet of the film deposition vacuum chamber 23 through an insulating gasket 28.

Putting the substrate Si into a small disc 20 in a vacuum cavity 23, rotating the small disc, wherein the cathode target material 1 is a circular graphite target with the purity of 99.999 percent, and when the vacuum in the vacuum cavity 23 reaches 3.0 multiplied by 10^-3Starting coating when Pa is below, wherein the coating conditions are as follows:

argon gas is introduced into the reactor for 20sccm, the arc flow is 55A, a bias power supply 37 of the elbow 3 applies a direct current positive bias voltage of 8V to the elbow, a bias power supply 22 applies a pulse negative bias voltage of-350V to the substrate, the pulse frequency is 350kHz, and the pulse width is 1.1 mus.

The deposition time is 10min under the coating condition, and the thickness of the deposited film is 10 nm.

And step 3: cleaning the substrate Si deposited with the amorphous carbon film by using a high-purity nitrogen gun, putting the substrate Si into a vacuum coating chamber, and preparing a nickel catalyst film on the surface of the amorphous carbon film by adopting an electron beam evaporation technology, wherein the coating conditions are as follows: vacuum-pumping to 2 × 10^- ³Pa below, setting the power of the electron gun to 10W, and the deposition rate to

And/s, the thickness of nickel is 100 nm.

And 4, step 4: a vacuum annealing furnace is adopted, and the vacuum degree in the furnace reaches 3.0 multiplied by 10^-2Pa, when the temperature reaches 500 ℃, putting the substrate Si on which the catalyst film and the amorphous carbon film are deposited, preserving the heat for 20min, and then cooling in air.

Raman spectrum detection was performed on the sample surfaces of the base Si/amorphous carbon film obtained in step 2 and the Si/amorphous carbon/metal catalyst film subjected to the heat treatment obtained in step 4, and the results are shown in fig. 3 and 4. It was found from FIG. 3 that the carbon film before the heat treatment was an amorphous carbon structure, in which the sp3 content was 85% as measured by XPS; it was found from fig. 4 that, after the heat treatment, G peaks and 2D peaks representing graphene were obtained, confirming that amorphous carbon was converted into graphene.

Comparative example 1:

this example is a comparative example to example 1.

In this embodiment, the preparation method of graphene is basically the same as that in embodiment 1, except that: the coating conditions in step 2 are as follows:

introducing argon gas of 2sccm, wherein the arc flow is 70A, applying a direct current positive bias voltage of 8V to the bent pipe, applying a pulse negative bias voltage of-100V to the substrate, and having a pulse frequency of 350kHz and a pulse width of 1.1 mu s;

depositing for 2min under the coating condition, wherein the thickness of the deposited film is 10 nm.

And (4) carrying out Raman spectrum detection on the sample surfaces of the substrate Si/amorphous carbon film prepared in the step (2) and the Si/amorphous carbon/metal catalyst film subjected to heat treatment prepared in the step (4). The carbon film before heat treatment was found to be an amorphous carbon structure, in which the sp3 content was 85% as measured by XPS; the raman spectrum after heat treatment is shown in fig. 5, which shows only the D peak and the G peak of amorphous carbon, and no 2D peak appears, demonstrating that no graphene is obtained.

Example 2:

step 1: the substrate was the same as in example 1, and the treatment method was the same as in step 1 of example 1;

step 2: deposition of amorphous carbon films

Essentially the same as step 2 in example 1, except that: the coating conditions in step 2 are as follows:

argon gas is introduced into the reactor for 20sccm, the arc flow is 60A, the elbow applies a direct current positive bias voltage of 10V, the magnitude of a pulse negative bias voltage applied to the substrate is-100V, the pulse frequency is 350kHz, and the pulse width is 1.1 mu s;

and depositing for 8min under the coating condition to obtain a film with the thickness of 15 nm.

And step 3: same as step 3 in example 1;

and 4, step 4: a vacuum annealing furnace is adopted, and the vacuum degree in the furnace reaches 3.0 multiplied by 10^-2Pa, putting the substrate Si after the catalyst film is evaporated into the substrate Si after the temperature reaches 450 ℃, preserving the temperature for 20min, and then cooling in air.

And (4) carrying out Raman spectrum detection on the sample surfaces of the substrate Si/amorphous carbon film prepared in the step (2) and the Si/amorphous carbon/metal catalyst film subjected to heat treatment prepared in the step (4). The carbon film before heat treatment is found to be an amorphous carbon structure, and the content of sp3 in the carbon film is 80% by XPS measurement; after heat treatment, a G peak and a 2D peak representing graphene are obtained, and the conversion of amorphous carbon into graphene is proved.

Example 3:

step 2: deposition of amorphous carbon films

Essentially the same as step 2 in example 1, except that: the coating conditions in step 2 are as follows: argon gas is introduced into the reactor for 20sccm, the arc flow is 60A, the elbow applies a direct current positive bias voltage of 10V, the magnitude of a pulse negative bias voltage applied to the substrate is-100V, the pulse frequency is 350kHz, and the pulse width is 1.1 mu s;

the film is deposited for 10min under the condition of the film coating, and the thickness of the film obtained by deposition is 20 nm.

And step 3: washing the substrate Si deposited with the amorphous carbon film by using a high-purity nitrogen gun, putting the substrate Si into a vacuum coating chamber, and preparing a copper catalyst film on the surface of the amorphous carbon film by adopting an electron beam evaporation technology, wherein the coating conditions are as follows: vacuum-pumping to 2 × 10^- ³Pa below, setting the power of the electron gun at 20W, and the deposition rate at

And/s, the copper thickness is 100 nm.

And 4, step 4: a vacuum annealing furnace is adopted, and the vacuum degree in the furnace reaches 3.0 multiplied by 10^-2Pa, putting the substrate Si after the catalyst film is evaporated into the substrate Si after the temperature reaches 450 ℃, preserving the temperature for 15min, and then cooling in air.

The embodiments described above are intended to illustrate the technical solutions of the present invention in detail, and it should be understood that the above-mentioned embodiments are only specific embodiments of the present invention, and are not intended to limit the present invention, and any modification, supplement or similar substitution made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A preparation method of graphene is characterized by comprising the following steps:

step 1: cleaning the surface of the substrate Si and then drying;

step 2: putting a substrate Si into a vacuum cavity by adopting a cathode vacuum arc deposition device, wherein the target material is a high-purity graphite target, and depositing an amorphous carbon film with the thickness of 2-30 nm on the surface of the substrate Si, and sp in the amorphous carbon film³The content is more than 80%, and the deposition conditions are as follows: the vacuum degree of the vacuum chamber for film deposition reaches 3.0 multiplied by 10^-3Introducing argon gas of 15-25 sccm and arc flow of 55-60A below Pa, applying pulse negative bias of-300V-350V to the substrate, pulse frequency of 330-370 kHz, pulse width of 0.9-1.2 mus, and deposition time of 1-10 min;

and step 3: washing the amorphous carbon film on the surface of the substrate Si by using a high-purity nitrogen gun, and preparing a metal catalyst film on the surface of the amorphous carbon film by adopting an electron beam evaporation technology, wherein the film coating conditions are as follows: vacuum-pumping to 2 × 10^-3Less than Pa, electron gun power of 8-20W, deposition rate

2. The method for producing graphene according to claim 1, wherein in step 1, the surface of the substrate Si is cleaned with ultrasonic waves in an alcohol solution.

3. The method for producing graphene according to claim 1, wherein in the step 2, the purity of the high-purity graphite target is 99.999% or more.

4. The method according to claim 1, wherein in step 4, the metal catalyst is copper or nickel.

5. The method for preparing graphene according to claim 1, wherein in the step 4, the thickness of the catalyst thin film is 70-100 nm.

6. The method of preparing graphene according to claim 1, wherein in the step 2, the deposition rate of the amorphous carbon film is 1 to 3 nm/min.

7. The method according to any one of claims 1 to 6, wherein the cathode vacuum arc source thin film deposition apparatus comprises a magnetic filter portion, which is composed of a tube body and a magnetic field generating device disposed at the outer periphery of the tube body, the tube body comprises a tube body inlet end surface and a tube body outlet end surface, there is at least one bend between the tube body inlet end surface and the tube body outlet end surface, and the included angle between the axes of the tube body on both sides of the bend is 135 °.

8. The method for preparing graphene according to claim 7, wherein a direct current positive bias voltage of 5-10V is applied to the magnetic filter part.

9. The method of claim 8, wherein in the step 4, the amorphous carbon film has a roughness Ra of less than 0.2 nm.