CN114314569B

CN114314569B - Method for forming graphene on substrate

Info

Publication number: CN114314569B
Application number: CN202210021236.8A
Authority: CN
Inventors: 丁松园; 孙力; 韩业创
Original assignee: Xiamen University
Current assignee: Xiamen University
Priority date: 2022-01-10
Filing date: 2022-01-10
Publication date: 2024-01-09
Anticipated expiration: 2042-01-10
Also published as: CN114314569A

Abstract

The present invention provides a method of forming a graphene film on a substrate, the substrate comprising a silicon carbide portion; the method comprises the following steps: heating at least a partial region of the silicon carbide portion in a vacuum, inert atmosphere or reducing atmosphere, the heating having the following temperature program: (i) Heating the heated region from the first temperature to a target temperature of 1400-2700 ℃ at a heating rate of 500 ℃/s or more; (ii) maintaining at the target temperature for 0-60s; (iii) And cooling the heated region from the target temperature to a second temperature at a cooling rate of 500 ℃/s or more.

Description

Method for forming graphene on substrate

Technical Field

The invention belongs to the field of graphene materials, and particularly relates to a method for forming graphene on a substrate.

Background

Graphene (Graphene) is a planar film with hexagonal honeycomb lattice composed of carbon atoms in sp2 hybridized orbitals.

Graphene may be produced via solid state graphitization by decomposition or sublimation of silicon atoms from the silicon carbide surface. (Berger C, et al J. Phys. Chem,2004,108 (52): 19912-19916.)

The related art adopts the following scheme to form graphene on the surface of a substrate. The 4H-SiC (0001) surface of the substrate was cleaned and smoothed by hydrogen and propane, respectively, followed by cleaning and smoothing by silane to remove surface oxides. Thereafter, graphene is grown on the surface by evaporating silicon at 1590-1610 ℃ and 890-910mbar (mbar) argon pressure for 30-60 minutes.

Disclosure of Invention

The inventors have found that excessively long heating times are detrimental to one or more properties of the product. For example, the microscopic morphology of a substrate is easily destroyed after 30-60 minutes of heat treatment for the substrate having the microscopic morphology.

In a first aspect, the present application provides a method of forming a graphene film on a substrate, the substrate comprising a silicon carbide portion;

the method comprises the following steps:

heating at least a partial region of the silicon carbide portion in a vacuum, inert atmosphere or reducing atmosphere, the heating having the following temperature program:

(i) Heating the heated region from the first temperature to a target temperature of 1400-2700 ℃ at a heating rate of 500 ℃/s or more;

(ii) Maintaining at the target temperature for 0-60s;

(iii) And cooling the heated region from the target temperature to a second temperature at a cooling rate of 500 ℃/s or more.

In some embodiments, in step i), the temperature increase rate is 500-800 ℃/s, 800-1100 ℃/s, 1100-1400 ℃/s, 1400-1700 ℃/s, 1700-2000 ℃/s, 2000-2300 ℃/s, 2300-2500 ℃/s, 2500-2800 ℃/s.

In some embodiments, in step iii), the cooling rate is 500-800 ℃/s, 800-1100 ℃/s, 1100-1400 ℃/s, 1400-1700 ℃/s, 1700-2000 ℃/s, 2000-2300 ℃/s, or 2300-2500 ℃/s.

In some embodiments, the target temperature is 1400-1600 ℃, 1600-1800 ℃, 1800-2000 ℃, 2000-2200 ℃, 2200-2400 ℃, 2400-2600 ℃, 2600-2700 ℃.

In some embodiments, the inert atmosphere is selected from argon, nitrogen, or a combination thereof.

In some embodiments, the reducing atmosphere is an atmosphere containing hydrogen.

In some embodiments, the first temperature is 300 ℃ or less, such as 0-50 ℃, 50-100 ℃, 100-150 ℃, 150-200 ℃, 200-250 ℃, or 250-300 ℃.

In some embodiments, the second temperature is 300 ℃ or less, such as 0-50 ℃, 50-100 ℃, 100-150 ℃, 150-200 ℃, 200-250 ℃, or 250-300 ℃.

In some embodiments, the silicon carbide portion contains one or more of the following silicon carbide materials: single crystal silicon carbide material, polycrystalline silicon carbide material, amorphous silicon carbide material, or a combination thereof.

In some embodiments, the silicon carbide portion contains one or more of the following silicon carbide materials: a silicon carbide material having a clean surface, a silicon carbide material having an impurity layer coated on the surface, or a combination thereof. The impurity layer may be selected from a carbide layer, an oxide layer, or a combination thereof.

In some embodiments, the morphology of the matrix is selected from: at least one of granule, wire, film, block, and powder.

In some embodiments, the silicon carbide portion has a dimension in one dimension of 1000 μm or less, such as 1nm to 10nm, 10nm to 100nm, 100nm to 1000nm, 1 micron to 10 microns, 10 microns to 100 microns, 100 microns to 1000 microns.

In some embodiments, the silicon carbide portions have dimensions in two mutually perpendicular dimensions of 1000 μm or less, for example 1nm to 10nm, 10nm to 100nm, 100nm to 1000nm, 1 micron to 10 microns, 10 microns to 100 microns, 100 microns to 1000 microns, respectively.

In some embodiments, the silicon carbide portions have dimensions in three mutually perpendicular dimensions of 1000 μm or less, for example 1nm to 10nm, 10nm to 100nm, 100nm to 1000nm, 1 micron to 10 microns, 10 microns to 100 microns, 100 microns to 1000 microns, respectively.

In some embodiments, the heating is performed in one or more of the following ways: joule heating, electromagnetic induction heating, arc heating, resistance heating, laser heating, electron beam heating, plasma arc heating, fuel combustion heating, torch flame heating, microwave heating, radio frequency radiation heating, or combinations thereof.

In some embodiments, the heating comprises joule heating comprising the operations of:

(i) Placing the substrate in proximity to a heating element of a joule heating device;

(ii) The heating program is executed by applying a joule heating current to the heating element.

In some embodiments, the heating element is selected from the group consisting of: carbon materials (e.g., carbon fibers), refractory metals, or combinations thereof;

the melting point of the high-melting point metal is above 1400 ℃. The refractory metal is, for example, tantalum, niobium, tungsten, nickel, or alloys thereof.

In some embodiments, the heating element is carbon paper or carbon cloth.

In some embodiments, the joule heating device comprises a first heat generator and a second heat generator, with the substrate disposed between the first heat generator and the second heat generator of the joule heating device.

In some embodiments, the heating comprises laser heating comprising the operations of: at least a partial region of the silicon carbide portion is irradiated by a laser beam.

In some embodiments, the silicon carbide portion comprises a predetermined region to be formed with graphene, and the method comprises said heating the region to be formed with graphene. Based on this, a graphene film can be formed in a region of the silicon carbide portion where graphene is to be formed. When the region where graphene is to be formed is a patterned region, a patterned graphene film can be formed on the silicon carbide portion.

FIG. 9 illustrates a schematic diagram of forming graphene on a substrate using laser heating in one embodiment. As shown, the laser 701 emits a laser beam 702 to pattern a specific region of the silicon carbide portion 412, and the irradiated region of the silicon carbide portion 412 is heated to form a patterned graphene film 413.

In some embodiments, the matrix includes a substrate and the silicon carbide portion is a cover film disposed on the substrate.

In some embodiments, the silicon carbide portion is a patterned overcoat. Based on the scheme, the graphene film is formed on the surface of the silicon carbide part after the silicon carbide part is subjected to heat treatment, and the graphene film inherits the patterning morphology of the silicon carbide part, namely, the patterning graphene film is formed on the surface of the substrate.

In some embodiments, fig. 10 shows a schematic flow diagram of one embodiment forming a graphene film on a substrate. As shown in the figure, the method for forming the graphene film on the surface of the substrate comprises the following steps:

(1) Providing a substrate 421 and depositing a silicon carbide cap layer 422 on the substrate;

the technique for depositing the silicon carbide cap layer 422 on the substrate 421 may employ any suitable technique known in the art. For example, using inductively coupled Plasma Enhanced Chemical Vapor Deposition (PECVD) techniques, a silicon carbide cap layer 422 is deposited on a substrate 421 (e.g., carbon paper) using methane and silane as raw materials under an argon atmosphere.

(2) Patterning silicon carbide cap layer 422

The techniques for patterning the silicon carbide cap layer 422 may employ any suitable technique known in the art, such as electron beam lithography. In this technique, a photoresist layer 423 (e.g., PMMA) is first applied to the surface of the silicon carbide cap layer 422. Then, a photolithography step is performed, that is, a desired pattern is etched on the photoresist layer 423 by using an electron beam lithography technique, and the product after the photolithography is developed in a developing solution to obtain a patterned photoresist film required during etching. An etching step is then performed to etch the surface of the patterned product using an inductively coupled plasma etcher to form a patterned silicon carbide cap layer 424. And after etching, carrying out a photoresist removing step again to remove the patterned photoresist film. Through the above steps, a patterned silicon carbide cap layer 424 is formed on the substrate 421.

(3) The substrate 421 with the patterned silicon carbide coating 424 on the surface is subjected to heat treatment by any one of the methods, after the heat treatment, graphene 425 is formed on the patterned silicon carbide coating 424, and the graphene film 425 inherits the morphology of the patterned silicon carbide coating 424. Through the above steps, a patterned graphene film 425 is formed on the substrate 421.

In some embodiments, the silicon carbide portion is located on a surface of the substrate.

In some embodiments, the matrix is comprised of the silicon carbide portion.

In some embodiments, the matrix includes an inner core and the silicon carbide portion is a shell that encapsulates the inner core.

In some embodiments, the shape morphology of the core is selected from: at least one of granule, wire, and film.

In some embodiments, the material of the inner core is an optical material. In some embodiments, the optical material is selected from: quartz (e.g., fused silica, natural quartz), glass (e.g., aluminate glass, aluminophosphate glass, aluminosilicate glass, borate glass, borogermanate glass, borophosphate glass, borosilicate glass, chalcogenide glass, fluoride glass, fluorophosphate glass, germanate glass, halide glass, phosphate glass, phosphosilicate glass, silicate glass, and/or tellurate glass), or combinations thereof

In some embodiments, the methods of the present application can be used to prepare graphene optical fibers. Fig. 11 shows a schematic diagram of a graphene optical fiber of one embodiment. In this embodiment, the graphene optical fiber includes an inner core 431 and a silicon carbide portion 432, the inner core 431 is a linear optical material, and the silicon carbide portion 432 is a skin layer coating the inner shell. Based on this scheme, after the graphene film 433 is formed on the surface of the silicon carbide portion 432 after being heated, the optical fiber product (i.e., graphene optical fiber) coated with the graphene film is obtained.

In some embodiments, the methods of preparation of the present application can be used to prepare graphene optical fiber products. The preparation method can be used for preparing various graphene optical fiber products. For example, any graphene optical fiber product described in the following documents: wang Xiaoyu graphene optical fiber preparation and application research progress [ J ]. Yan Shanda school journal, 2020.

In some embodiments, the graphene film has a ratio of D peak to G peak in the raman spectrum of 0.5 or less (e.g., 0.05-0.1, 0.1-0.2, 0.2-0.3, 0.3-0.4, or 0.4-0.5).

In some embodiments, the number of layers of the graphene film is 1-10, e.g., the number of layers of the graphene film is 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10.

In a second aspect, the present application provides a composite comprising a substrate and a graphene film, at least part of the surface of the substrate being covered by the graphene film, the composite being prepared by the method of any one of the preceding claims.

In some embodiments, the graphene film is a patterned graphene film.

In some embodiments, the complex is a graphene optical fiber. The graphene optical fiber comprises a linear optical material and a graphene layer coating at least part of the surface of the linear optical material.

Interpretation of the terms

The terms "first," "second," and the like, as used herein, may be used to describe various objects, but these objects are not limited by these terms. These terms are only used to distinguish one object from another. For example, a first object may be referred to as a second object, and similarly, a second object may be referred to as a first object, without departing from the scope of the invention.

The term "about" is used to indicate that the value modified by the term has an understanding range associated with it, where the range may be ± 20%, ±15%, ±10%, ±5% or ± 1%. The term "substantially" is used to indicate that the value is near the target value, within 80% of the target value, within 85% of the target value, within 90% of the target value, within 95% of the target value, or within 99% of the target value.

The term "joule heating," also known as ohmic heating or resistive heating, may refer to the process of passing an electric current through a material to generate heat. Without being bound by theory of operation, joule heating may be caused by interactions between moving particles (typically, but not always, electrons) that form an electrical current and atomic ions that make up the bulk of the conductor. Charged particles in the circuit may be accelerated by the electric field, but give up some of their kinetic energy whenever they collide with ions. The increase in kinetic or vibrational energy of the ions is manifested as an increase in heat and conductor temperature. Thus, energy may be transferred from the power source to the conductor and any material in thermal contact therewith.

The term "powder" generally refers to a solid material composed of a plurality of fine particles.

The term "sheet-like" generally refers to an object having a dimension in two directions that is significantly greater (e.g., more than 2 times) than the dimension in a third direction.

The term "linear" generally refers to an object having a dimension in one direction that is significantly greater (e.g., more than 2 times) than the dimensions of the other two directions.

The term "heating" includes heating the substrate directly or heating a medium in the vicinity of the substrate.

The term "optical material" generally refers to a material that allows light or light energy to propagate therein or therethrough.

The invention has the beneficial effects that:

one or more technical schemes of the application have one or more of the following beneficial effects:

(1) According to the method for forming the graphene on the substrate, the microscopic morphology of the substrate can be effectively maintained, and after the graphene is formed on the substrate, the microscopic morphology of the substrate can be effectively maintained.

(2) The graphene obtained by the method for forming graphene on a substrate has improved quality, I _D /I _G The value is lower.

(3) The graphene film number obtained by the method for forming graphene on the substrate is small.

(4) The method for forming the graphene on the substrate can form the patterned graphene covering layer on the surface of the substrate.

(5) The method for forming graphene on the substrate is suitable for preparing graphene optical fibers.

Drawings

Fig. 1 shows a schematic diagram of a joule heating apparatus of some embodiments.

Fig. 2 shows a schematic diagram of a heating element of a joule heating apparatus of some embodiments.

Fig. 3 (a), (b) and (c) show XRD lines of three raw materials, β -SiC polycrystalline powder (matrix I), 4H-SiC single crystal flakes (matrix IV), siC amorphous film (matrix V), respectively.

Fig. 4 (a), (b) and (c) show raman spectral lines of three raw materials, respectively, β -SiC polycrystalline powder (matrix I), 4H-SiC single crystal flakes (matrix IV) and SiC amorphous film coating (matrix V).

Fig. 5 (a) and (b) show raman spectral lines of the products of example 2 and comparative example 1, respectively.

Fig. 6 (a) (b) (c) shows a scanning electron micrograph of the substrate I, the product of example 2, and the product of comparative example 2, respectively.

Fig. 7 (a) (b) (c) shows an atomic force microscope topography photograph of the substrate IV, the product of example 8, and the product of comparative example 3, respectively.

Fig. 8 (a) (b) (c) shows an atomic force microscope topography photograph of a substrate V, the product of example 9, and the product of comparative example 4, respectively.

FIG. 9 illustrates a schematic diagram of forming a patterned graphene film on silicon carbide portions using laser heating, according to one embodiment.

Fig. 10 is a schematic flow chart of forming a patterned graphene film on a substrate according to one embodiment.

Fig. 11 shows a schematic diagram of a graphene optical fiber of one embodiment.

The figures are numbered as follows: 1, a power supply; 2, a vacuum pump; 3, a heating body; 4, heating the object; 51 a first electrode; 52 a second electrode; 6, an air inlet valve; and 7, an air outlet valve.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. It will be apparent that the described embodiments are some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

1. Raw materials

The raw materials used in the following experiments are shown in the following table.

TABLE 1

2. Heating device

In the following experiments a joule heating device was used to heat the substrate.

Referring to fig. 1, fig. 1 shows a schematic view of the joule heating apparatus. The joule heating device comprises a power supply 1, a first electrode 51, a second electrode 52 and a heating body 3, wherein the heating body 3 is electrically connected with the anode and the cathode of the power supply through the first electrode 51 and the second electrode 52 respectively. When the joule heating device is operated, a current flowing through the heating element 3 connected to the power supply 1 flows through the heating element 3, and when the current flows through the heating element 3, electric energy is converted into heat energy (joule heat) due to resistance loss. The joule heating device further comprises a working chamber 7, the heater 3 being located within the working chamber 7. The working chamber 7 is used to provide a vacuum environment or a specific atmosphere. The working chamber 7 includes an intake valve 61 and an exhaust valve 62. The inlet valve 61 and the outlet valve 62 may be connected to a gas system for providing a specific atmosphere to the working chamber 7. The joule heating device further comprises a vacuum system 2, the vacuum system 2 being connected to the working chamber 7 for providing a vacuum environment for the working chamber 7.

Referring to fig. 2, fig. 2 shows a schematic view of the heating element 3 of the joule heating apparatus. As shown in the drawing, the heat generating body 3 includes a first heat generating layer 31 and a second heat generating layer 32, and both the upper heat generating portion 31 and the lower heat generating portion 32 are electrically connected to a first electrode 51 and a second electrode 52. When the joule heating device is operated, the first heat generating layer 31 and the second heat generating layer 32 are laminated, and the heating target 4 is located between the first heat generating layer 31 and the second heat generating layer 32.

In the following examples, the first heat generating layer 31 and the second heat generating layer 32 were each carbon paper with a size of 1cm×3cm.

3. Experimental procedure

Example 1

(1) Surface cleaning treatment

beta-SiC polycrystalline powder from Alfa Aesar was provided as an experimental raw material. Pretreatment is performed to remove impurities (mainly a carbonized layer and an oxidized layer) on the surface of the SiC polycrystalline powder, wherein the pretreatment comprises:

removing a carbonization layer: placing beta-SiC in a tube furnace, heating to 650 ℃, and calcining in air for 2 hours to remove a carbonized layer on the surface;

oxide layer removal: soaking the product in 20wt% hydrofluoric acid solution to eliminate SiO completely ₂ A residue;

cleaning: and washing and centrifuging the product of the last step with deionized water and absolute ethyl alcohol for a plurality of times, and placing the product in a 60 ℃ oven for drying to obtain SiC powder with clean surface, wherein the number is matrix I.

(2) Heat treatment

10mg of the substrate I was used as a heating target. The substrate I is placed between the first heating layer 31 and the second heating layer 32 of the joule heating device. The working chamber 7 is evacuated by means of the vacuum pump 2 to a pressure of less than 0.1Pa. The power supply 1 of the Joule heating device is started to electrify the heating body 3. The operating voltage of the joule heating device during operation was about 30V, the operating current was about 40A, and the energization time was 1s. The temperature program for heating the heating target 4 includes:

(1) The temperature was increased from the first temperature to a peak temperature of 1400 c at a heating rate of 2000 c/s.

(2) Preserving heat for 1s at the peak temperature;

(3) Cooling from the peak temperature to a second temperature at a cooling rate of 600 ℃/s.

The first and second temperatures herein are about 25 ℃ and about 40 ℃, respectively, as follows.

Examples 2 to 3

Examples 2 to 3 were identical to example 1 in terms of heating target and heating equipment, except that the temperature program during heating was different, and reference was made to example 1 for other step parameters.

The operating current in example 2 was set to 60A and the energization time was 5s. The temperature program in the heat treatment step of example 2 thus includes:

(1) The temperature was increased from the first temperature to a peak temperature of 1800 c at a heating rate of 2400 c/s.

(2) Preserving heat for 5s at peak temperature;

The operating current in example 3 was set to 80A and the energization time was 30s. The temperature program in the heat treatment step of example 3 thus includes:

(1) The temperature was increased from the first temperature to a peak temperature of 2200 c at a ramp rate of 2800 c/s.

(2) Preserving heat for 30s at peak temperature;

Examples 4 to 5

Examples 4 to 5 differ from example 2 in that the heating target is different, and other step parameters are referred to in example 1.

In example 4, the object to be heated was SiC polycrystalline powder (number: matrix II) having a carbonized layer on the surface. The method for obtaining the composition comprises the following steps: beta-SiC polycrystalline powder from Alfa Aesar was provided as an experimental raw material. Placing the beta-SiC polycrystalline powder into a 20wt% hydrofluoric acid solution for fully soaking so as to completely remove SiO ₂ Residue, namely SiC polycrystalline powder with a carbonized layer on the surface is obtained;

the heated substrate in example 5 was SiC polycrystalline powder (numbered substrate III) with an oxide layer on the surface. The method for obtaining the composition comprises the following steps: beta-SiC polycrystalline powder from Alfa Aesar was provided as an experimental raw material. beta-SiC polycrystalline powder. Placing the mixture in a tube furnace, heating to 650 ℃, and calcining in air for 2 hours to remove the carbonized layer on the surface, thus obtaining the SiC polycrystalline powder with the oxidized layer on the surface.

Examples 6 to 7

Examples 6-7 differ from example 2 in that the atmosphere of the working chamber during heating is different and other step parameters are referred to in example 2.

In example 6, the atmosphere of the working chamber was argon gas, and the flow rate was 100sccm.

In example 7, the atmosphere of the working chamber was hydrogen gas, and the flow rate was 100sccm.

Examples 8 to 9

Examples 8 to 9 differ from example 2 in the object to be heated, and reference is made to example 2 for other step parameters.

Example 8 a 4H-SiC sheet-like single crystal (number substrate IV) having a clean surface was used as a heating target.

Example 9 was conducted using an amorphous SiC plating film (No. V as a substrate) as a heating target. The method for obtaining the SiC amorphous coating comprises the following steps: and (3) depositing a 50nm thick SiC amorphous coating on the carbon paper by using an inductively coupled Plasma Enhanced Chemical Vapor Deposition (PECVD) system and using methane and silane as raw material gases in an argon atmosphere.

Comparative example 1

Comparative example 1 uses the same heating and heating apparatus as example 2, except that the temperature program during heating was different. Comparative example 1 the temperature program in the heat treatment step included:

(1) The temperature was increased from the first temperature to a peak temperature of 1360 ℃ at a heating rate of 2000 ℃/s.

(2) Preserving heat for 5s at peak temperature;

Comparative example 2

Comparative example 2 uses the same heating target (substrate I) as example 2, except that the heating apparatus and the temperature program used are different:

comparative example 2 a tube furnace was used as the heating apparatus. The atmosphere in the tube furnace was argon gas at a flow rate of 100sccm. The heating program includes:

(1) The temperature was increased from the first temperature to a peak temperature of 1600 c at a ramp rate of 16 c/min.

(2) Preserving heat for 60min at peak temperature;

(3) And cooling from the peak temperature to a second temperature at a cooling rate of 30 ℃/min.

Comparative example 3

Comparative example 3 uses the same heating target (substrate IV) as example 8, except that the heating apparatus and the temperature program used are different:

comparative example 3 a tube furnace was used as the heating apparatus. The atmosphere in the tube furnace was argon gas at a flow rate of 100sccm. The heating program includes:

(2) Preserving heat for 60min at peak temperature;

Comparative example 4

Comparative example 4 uses the same heating target (substrate V) as example 9, except that the heating apparatus and the temperature program used are different:

comparative example 4 a tube furnace was used as the heating apparatus. The atmosphere in the tube furnace was argon gas at a flow rate of 100sccm. The heating program includes:

(2) Preserving heat for 60min at peak temperature;

4. Analytical detection

1. XRD analysis

X-ray diffraction analysis was performed on three raw materials of β -SiC polycrystalline powder (matrix I), 4H-SiC flaky single crystal (matrix IV) and SiC amorphous coating film (matrix V) by using a Rigaku SmartLab-SE X-ray diffractometer, which were manufactured by Japanese national institute, inc., to obtain XRD spectra of (a), (b) and (c) in FIG. 3, respectively.

As shown in fig. 3 (a), XRD lines of the β -SiC polycrystal powder have (111), (002), (022), (113) and (222) diffraction peaks, and are represented as typical polycrystal structures. As shown in FIG. 3 (b), XRD patterns of the 4H-SiC plate-like single crystal had diffraction peaks of (004) and (008), and exhibited a typical single crystal structure. As shown in fig. 3 (c), the characteristic peak pattern of SiC was not substantially detected in the XRD spectrum of the SiC amorphous plating film, indicating that the SiC amorphous plating film was amorphous.

2. Raman spectrum analysis

The heating object and the product of examples and comparative examples were subjected to raman spectroscopic analysis using a micro laser raman spectrometer (Renishaw inVia confocal Raman microscope). The instrument parameters were set as follows: excitation wavelength 532nm, exposure time 10s, laser power 0.05mW, spot diameter 1.5 μm.

Fig. 4 (a), (b) and (c) show raman spectral lines of three heating objects (matrix I, matrix II and matrix II), respectively.

As shown in FIG. 4 (a), only the Si-C vibrational peak (located at 793.6 cm) was identified in the Raman spectrum of the matrix I ^-1 Where) indicates that the surface of the SiC polycrystalline powder is cleaner.

As shown in FIG. 4 (b), the Si-C vibrational peak (located at 793.6 cm) can be identified simultaneously in the Raman spectrum of the substrate II ^-1 Where) and characteristic peaks of carbon (D, G, and 2D peaks), indicating the presence of a carbonized layer on the surface of the SiC polycrystalline powder.

As shown in fig. 4 (c), raman spectrum of matrix IIIIn which the Si-C vibration peak and the Si-O vibration peak (located at 960.8 cm) can be identified simultaneously ^-1 Where) indicates the presence of an oxide layer on the surface of the SiC polycrystalline powder.

Fig. 5 (a) and (b) show raman spectral lines of the products of example 2 and comparative example 1, respectively. Characteristic peaks of graphene, including those located at 1345.6cm, can be identified in FIG. 5, respectively ^-1 D peak of (2) at 1577.8cm ^-1 G peak sum at 2693.2cm ^-1 Is a 2D peak of (2). Graphene formed by the substrates of example 2 and comparative example 1 after heating is described.

As shown in fig. 5 (a), in the raman spectrum of the product of example 2, the 2D peak reflecting the quality of graphene is sharp and sharp, and the D peak reflecting the defect represented by graphene has low intensity. D peak and G peak (I _D /I _G ) The ratio of the peak intensities of (2) is 0.12, and the ratio is lower, so that the quality of the graphene can be deduced to be higher.

As shown in fig. 5 (b), in the raman spectrum of the product of comparative example 1, the 2D peak reflecting the mass of graphene was weak, and the D peak intensity reflecting the defect represented by graphene was strong. Peak intensity ratio of D peak to G peak (I _D /I _G ) The ratio is 2.71, and therefore, it can be inferred that the defect density of graphene is large.

In addition, the peak intensity ratio (I _2D /I _G ) Judging the number of layers of the graphene approximately, when I _2D /I _G When=2, graphene is a monolayer; when I _2D /I _G =1, graphene is bilayer. The graphene films of the products of examples 1-9 were about 1-4 layers.

The peak intensity ratio (I) of the D peak to the G peak in the Raman spectra of the products of examples 1 to 9 and comparative examples 1 to 4 _D /I _G ) And the peak intensity ratio of 2D peak to G peak (I _2D /I _G ) Are recorded in Table 2, respectively.

3. BET specific surface area analysis

The specific surface area of the β -SiC polycrystalline powder and product used in the examples was analyzed by the gas adsorption BET method using a fully automatic physicochemical adsorber of ASAP2020, american microphone company. By comparing the specific surface areas of the beta-SiC polycrystalline powder and the product, the effect of heating on the powder dispersibility can be reflected.

The specific surface area test steps and parameters were set as follows:

(1) Pretreatment: about 100mg of the material to be tested is taken for pretreatment, the temperature is raised to 90 ℃ at the heating rate of 10 ℃/min, the heat is preserved for 1h for dehydration, the temperature is raised to 300 ℃ at the heating rate of 10 ℃/min, and the heat is preserved for 4h for degassing treatment.

(2) BET test: and after the pretreatment of the material is finished, weighing the mass of the treated sample, calculating the net weight at the moment, inputting the net weight to directly start the test, and waiting for the end of the test to obtain the specific surface area value.

The specific surface area of the beta-SiC polycrystalline powder (matrix I) with clean surface is 28.70m ² And/g. beta-SiC polycrystalline powder (matrix II) having a carbonized layer on the surface thereof had a specific surface area of 29.30m ² And/g. The specific surface area of the beta-SiC polycrystalline powder (matrix III) with an oxide layer on the surface thereof was 29.60m ² /g。

The BET specific surface areas of the products of examples 1-7 and comparative examples 1-2 are reported in Table 2. As shown in Table 2, the products obtained in examples 1-7 using the specific heating temperature procedure of the present application have a relatively high specific surface area and are substantially free of particle agglomeration due to the heat treatment. Comparative example 2 has a remarkably reduced specific surface area of the product due to the long incubation time of 60 min.

4. Scanning electron microscope analysis

The morphology analysis of the substrate I and the heat-treated product thereof was carried out using a HATACHI S-4800 microscope from Hitachi Japan. The microscope uses an acceleration voltage of 15KV.

As can be seen by comparing fig. 6 (a) and (b), the product of example 2 substantially conforms to the morphology of the substrate I. The product of example 2 has good particle analysis and no significant agglomeration.

As can be seen by comparing FIGS. 6 (a) and (c), the morphology of the product of comparative example 2 is significantly different from that of matrix I. The product morphology of comparative example 2 has serious agglomeration sintering phenomenon, and the original morphology of the matrix I is lost.

5. Atomic force microscope analysis

And carrying out atomic force microscope surface analysis on the substrate IV, the substrate V and the products after the substrate V and the substrate V are subjected to heating treatment by adopting a Dimension Icon model atomic force microscope. Based on the atomic force imaging of the surface, the surface roughness values can be measured, as detailed in table 2.

Fig. 7 (a) (b) (c) shows an atomic force microscope topography photograph of the substrate IV, the product of example 8, and the product of comparative example 3, respectively. As can be seen from comparing fig. 7 (a) and (b), the product of example 8 has a substantially similar morphology to the substrate IV, and the product of example 8 has a smoother and smoother surface. The surface roughness ra= 0.0971nm of the substrate IV, the surface roughness ra=0.652 nm of the product of example 8. As can be seen from comparing fig. 7 (a) and (c), the morphology difference between the product of comparative example 3 and the substrate IV is evident, the surface of the product of comparative example 2 is more rough, and the roughness reaches ra=6.02 nm.

Fig. 8 (a) (b) (c) shows an atomic force microscope topography photograph of a substrate V, the product of example 9, and the product of comparative example 4, respectively. As can be seen by comparing fig. 8 (a) and (b), the product of example 9 has a substantially similar morphology to the substrate V, and the product of example 9 has a relatively flat surface. The surface roughness Ra of the substrate v=29.7 nm, and the surface roughness Ra of the product of example 9=31.6 nm. As can be seen from comparing fig. 8 (a) and (c), the morphology difference between the product of comparative example 4 and the substrate V is evident, the surface of the product of comparative example 4 is rougher, and the roughness reaches ra=208 nm.

5. Conclusion(s)

In summary, embodiments 1-9 above employ the method of forming a graphene film on a substrate including a silicon carbide portion of the present application, the method comprising:

(ii) Maintaining at the target temperature for 0-60s;

The formation of graphene films on a substrate of examples 1-9 above has one or more of the following advantages:

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method of forming a graphene film on a substrate, the substrate comprising a silicon carbide portion; the method comprises the following steps:

(i) Heating the heated region from a first temperature to a target temperature of 1400-2700 ℃ at a heating rate of 800-2800 ℃/s;

(ii) Maintaining at the target temperature for 0-5s;

(iii) Cooling the heated region from the target temperature to a second temperature at a cooling rate of 500-1100 ℃/s;

wherein,

the first temperature is 0-300 ℃;

the second temperature is 0-300 ℃.

2. The method according to claim 1, characterized in that:

-the inert atmosphere is selected from argon, nitrogen or a combination thereof;

-the reducing atmosphere is an atmosphere containing hydrogen.

3. The method of claim 1, the silicon carbide portion comprising one or more of the following silicon carbide materials: single crystal silicon carbide material, polycrystalline silicon carbide material, amorphous silicon carbide material.

4. The method of claim 1, the silicon carbide portion comprising one or more of the following silicon carbide materials: silicon carbide material with clean surface, silicon carbide material coated with impurity layer.

5. The method of claim 1, wherein the morphology of the substrate is selected from the group consisting of: at least one of granule, wire, film, block, and powder.

6. The method of claim 1, having one or more of the following features:

-the silicon carbide fraction has a size in one dimension of 1000 μm or less;

-the silicon carbide portions have dimensions in two mutually perpendicular dimensions of 1000 μm or less, respectively;

the silicon carbide portions have dimensions of respectively 1000 μm or less in three mutually perpendicular dimensions.

7. The method of claim 1, wherein the heating is performed in one or more of the following ways: joule heating, electromagnetic induction heating, arc heating, resistance heating, laser heating, electron beam heating, plasma arc heating, fuel combustion heating, torch flame heating, microwave heating, and radio frequency radiation heating.

8. The method of claim 1, wherein the heating comprises joule heating comprising the operations of:

9. A method according to claim 8, wherein the heating element is made of a material selected from the group consisting of: a carbon material, a refractory metal, or a combination thereof; the melting point of the high-melting point metal is above 1400 ℃.

10. The method according to claim 9, wherein the heating element is made of a material selected from the group consisting of: carbon fiber, refractory metal, or a combination thereof; the melting point of the high-melting point metal is above 1400 ℃.

11. The method of claim 1, the heating comprising laser heating comprising: at least a partial region of the silicon carbide portion is irradiated by a laser beam and the heating is localized to the region where graphene is to be formed.

12. The method of claim 1, the silicon carbide portion comprising a predetermined region to be formed with graphene, the method comprising performing the heating on the region to be formed with graphene and localizing the heating to the region to be formed with graphene.

13. The method of claim 1, the base comprising a substrate and the silicon carbide portion, the silicon carbide portion being a cover film disposed on the substrate.

14. The method of claim 1, the silicon carbide portion being located on a surface of the substrate.

15. The method of claim 1, the matrix comprising an inner core and the silicon carbide portion, the silicon carbide portion being a shell coating the inner core.

16. The method of claim 15, having one or more of the following features:

-the shape morphology of the core is selected from: at least one of granular, linear and membranous;

-the material of the inner core is an optical material.

17. The method of claim 1, wherein the graphene film has a ratio of D peak to G peak in a raman spectrum of 0.5 or less.

18. The method of claim 1, wherein the number of layers of the graphene film is 1-2.

19. A composite comprising a substrate and a graphene film, at least part of the surface of the substrate being covered by the graphene film, the composite being prepared by the method of any one of claims 1-18.

20. The composite of claim 19, at least a portion of a surface of the substrate being covered by a patterned graphene film.

21. The complex of claim 19 or 20, which is a graphene optical fiber.