CN108396377A - A kind of preparation method of high quality monolayer polycrystalline graphite alkene film - Google Patents

Abstract

The invention relates to a graphene new material and its chemical vapor deposition (CVD) preparation technology, in particular to a preparation method of high-quality single-layer polycrystalline graphene, which is suitable for preparing high-quality single-layer polycrystalline graphene film. Using CVD technology, metals with medium carbon solubility are used as growth substrates, and graphene crystal nuclei with controllable density are formed through infiltration and precipitation, and polycrystalline graphene films with uniform and adjustable grain size are obtained through surface growth. Adopting the present invention can obtain a high-quality single-layer polycrystalline graphene film with small grain size, uniform controllability, and perfectly assembled grain boundaries, which can be used in nanoelectronic devices, optoelectronic devices, photonic devices, gas sensors, thin film electronic devices, etc. Lay the foundation for applications in the fields of electronics, optoelectronics, and thermoelectricity.

Description

A kind of preparation method of high-quality monolayer polycrystalline graphene film

Technical field:

The invention relates to a graphene new material and its chemical vapor deposition (CVD) preparation technology, in particular to a preparation method of high-quality single-layer polycrystalline graphene, which is suitable for preparing high-quality single-layer polycrystalline graphene film.

Background technique:

Graphene is a single-layer carbon atom crystal tightly packed into a two-dimensional honeycomb crystal structure, and is the basic unit for constructing carbon materials of other dimensions. This strictly two-dimensional crystalline material has excellent electrical, thermal, mechanical and optical properties, such as: electron mobility up to 200,000cm ² /V·s at room temperature, thermal conductivity up to 5000W·m ^-1 ·K ^{- 1.} The Young's modulus is as high as 1TPa, and the visible light absorption rate is only 2.3%. These excellent properties of graphene make it expected to be widely used in the fields of multifunctional nanoelectronic devices, transparent conductive films, composite materials, energy storage materials and gas sensors. Therefore, since its discovery in 2004, it has quickly become the most active research frontier in the fields of materials science, condensed matter physics, and chemistry.

At present, there are many methods for preparing graphene, mainly including micromechanical exfoliation method, chemical exfoliation method, chemical redox method, silicon carbide epitaxial growth method, and chemical vapor deposition (CVD). Among them, the CVD method has the advantages of simplicity, high-quality graphene, large-scale growth, and easy transfer. Therefore, it is widely used in the preparation of graphene field-effect transistors and transparent conductive films. The main method of graphene film. Grain boundary is an important structural feature of graphene prepared by CVD method, which will affect many properties of graphene. Therefore, the preparation of high-quality single-layer polycrystalline graphene films with uniform and adjustable grain size is of great significance for adjusting the electrical, optoelectronic, and thermoelectric properties of graphene.

However, under the condition of ensuring single-layer graphene, it is difficult to realize the preparation of large-scale single-crystal or nanocrystalline graphene films simply by reducing or increasing the nucleation density. For example, for a copper substrate with a low carbon concentration, graphene growth follows a surface adsorption mechanism, and a high-concentration carbon source increases the nucleation density of graphene, but at the same time brings multilayer domains. On the contrary, for the nickel substrate with high carbon concentration, graphene growth follows the infiltration precipitation mechanism, and it is difficult to obtain single-layer graphene. Therefore, up to now, the grain size of graphene films is mostly distributed between 1 micron and 1 mm. How to prepare high-quality single-layer polycrystalline graphene with uniform and controllable grain size by CVD method has always been a difficulty in the field of graphene research.

Invention content:

The purpose of the present invention is to provide a method for preparing high-quality single-layer polycrystalline graphene, which has the advantages of low cost, simple operation, good controllability, etc., so it can be used as a method suitable for preparing high-quality single-layer polycrystalline Ideal approach for graphene.

Technical scheme of the present invention is:

The invention provides a method for preparing high-quality single-layer polycrystalline graphene. The method first adopts chemical vapor deposition technology. In the presence of hydrogen, the metal substrate is annealed in the first step, and a larger flow rate is used to The carbon source gas is catalytically cracked on the surface of the metal substrate at high temperature to grow a graphene film; the second step is to etch the graphene on the surface of the substrate by changing the growth atmosphere to an inert gas, and then use a trace amount of hydrogen to make the carbon dissolved in the substrate Atoms are precipitated to the surface of the substrate to form a graphene crystal nucleus with adjustable density; the third step is to introduce a small amount of carbon source gas to re-grow the surface of the graphene crystal nucleus. Controlled high-quality single-layer polycrystalline graphene films.

In the present invention, the metal substrate used is a flat platinum, ruthenium or iridium metal sheet or film, with a purity greater than 98wt% and a thickness of not less than 300nm, preferably 50μm-200μm.

In the present invention, the metal substrate used is ultrasonically cleaned in one or more of acetone, ethyl lactate, water, isopropanol and ethanol, respectively, and the time is not less than 10 minutes, preferably 1 hour to 2 hours.

In the present invention, the metal substrate used needs to be annealed and heat-treated, and the treatment temperature is 800°C-1600°C, preferably 1000°C-1100°C; the atmosphere is hydrogen (or a mixed gas of hydrogen and nitrogen or argon, etc.), wherein The ratio is not less than 1%, the gas flow rate is not less than 20 sccm, and the annealing time is not less than 10 minutes. Preferably, the hydrogen molar ratio is 90-100%, the gas flow rate is 500-700 sccm, and the annealing time is 8 hours-10 hours.

In the present invention, high-quality single-layer polycrystalline graphene is prepared by chemical vapor deposition, and the carbon source used is one or more of hydrocarbons such as methane, ethane, acetylene, ethylene, ethanol, etc., and the carrier is hydrogen. (or a mixed gas of hydrogen and nitrogen or argon, etc.), the purity of the carbon source and the carrier gas are greater than 98% (volume).

In the present invention, the molar ratio of carbon source to hydrogen in the first step of growth is 0.004-1, preferably 0.01-0.1. The growth temperature is 500°C to 1300°C, preferably 600°C to 1050°C. The growth time is not less than 10 minutes, preferably 30 minutes to 1 hour.

In the present invention, in the etching method used in the second step, the etching temperature is 500°C to 1300°C, preferably 600°C to 1050°C, the etching time is not less than 10 minutes, preferably 20 minutes to 2 hours, and the atmosphere is inert Gases and their dispersed impurities.

In the present invention, in the method for preparing high-density graphene grains used in the second step, the precipitation temperature is 500°C to 1300°C, preferably 600°C to 1050°C. The precipitation time is not less than 10 minutes, preferably 30 minutes to 3 hours. The molar ratio of hydrogen to inert gas is 0.005-0.1, preferably 0.007-0.05.

In the present invention, in the regrowth method used in the third step, the regrowth temperature is 500°C to 1300°C, preferably 600°C to 1050°C, and the regrowth time is not less than 20 minutes, preferably 1 hour to 6 hours. The regrowth atmosphere is a mixed gas of carbon source and hydrogen, and the carbon source used is one or more of methane, ethane, acetylene, ethylene, and ethanol hydrocarbons. The molar ratio of carbon source to hydrogen is 0.005-0.1, preferably 0.01-0.05.

In the present invention, after the growth is completed, the metal substrate needs to be rapidly cooled to below 200°C, preferably 100°C to 150°C, under the protection of a carrier containing hydrogen; the carrier gas is a mixed gas of hydrogen, nitrogen or argon, and the hydrogen molar ratio Not less than 1%, preferably 50-80%; rapid cooling rate not less than 50°C/sec, preferably 80-100°C/sec.

In the present invention, the crystal grain size of the single-layer polycrystalline graphene film prepared by the method is continuously adjustable from 10 nanometers to 1 micron (the general range is 50 nanometers to 1 micron).

Features and beneficial effects of the present invention are:

1. The present invention adopts chemical vapor deposition technology, takes platinum, iridium and other medium carbon-soluble metals as the growth substrate, and uses hydrocarbons as the carbon source. In the presence of hydrogen, the metal substrate is first annealed, and utilizes relatively A large flow of carbon source gas is catalytically cracked on the surface of the metal substrate at high temperature to grow a graphene film; then by changing the growth atmosphere to an inert gas, the graphene on the surface of the substrate is etched, and then a trace amount of hydrogen is used to make the carbon dissolved in the substrate Atoms are precipitated to the surface of the substrate, and high-density graphene nuclei with adjustable density are formed by infiltration and precipitation; then a small amount of carbon source gas is introduced again to re-grow the surface, and finally a high-quality graphene with uniform and controllable grain size and perfect grain boundaries is obtained. Monolayer polycrystalline graphene film.

2. The technological process of the present invention is simple, easy to operate, low in cost, and can be expected to be produced in large quantities.

3. Adopting the present invention can obtain high-quality graphene film with small grain size, the grain size can be adjusted within 10 nanometers to 1 micron, and the grain boundaries are perfectly assembled. Transparent conductive films, gas sensors, thin-film electronic devices and other applications in the fields of electronics, optoelectronics, and thermoelectrics have laid a foundation.

Description of drawings:

Figure 1 is a schematic diagram of an experimental setup for growing polycrystalline graphene by CVD. In the figure, 1 gas inlet; 2 metal substrate; 3 thermocouple; 4 gas outlet; 5 mass flow meter.

Fig. 2 is a schematic diagram of the growth of polycrystalline graphene film after growth-etching-precipitation-re-growth and scanning electron micrographs of corresponding stages. Wherein, Fig. 2 (A) is a schematic diagram of the growth process; Fig. 2 (B) is the graphene film prepared for the first growth; Fig. 2 (C) is the platinum substrate surface after Fig. 2 (B) is etched; Fig. 2 (D) is the high-density graphene grain after the precipitation of Fig. 2 (C); Fig. 2 (E) is the single-layer polycrystalline graphene film after the regrowth of Fig. 2 (D), see embodiment 1.

Figure 3(A) and Figure 3(B) are the Raman spectra of high-density graphene grains and corresponding polycrystalline graphene, respectively.

Figure 4. Characterization of nuclei with different grain sizes and corresponding polycrystalline graphene films. Fig. 4 (A), Fig. 4 (B), Fig. 4 (C) and Fig. 4 (D) are high-density graphene crystal nuclei under 900 ℃, 950 ℃, 1000 ℃ and 1040 ℃ respectively for the precipitation temperature; Fig. 4(E), Fig. 4(F), Fig. 4(G) and Fig. 4(H) are TEM images of polycrystalline graphene films with grain sizes of about 200 nm, 500 nm, 700 nm and 1 micron, respectively. Field image, the scale bar in the figure is 500 nm. Fig. 4 (I) and Fig. 4 (J) are the high-resolution transmission electron micrographs of the polycrystalline graphene thin film of grain size about 200 nanometers and 700 nanometers respectively, and the scale in the figure is 1 nanometer; Fig. 4 (K), Fig. 4(L), Fig. 4(M) and Fig. 4(N) are the corresponding grain size statistics.

Figure 5 shows the thermal and electrical properties of polycrystalline graphene as a function of grain size. Among them, Fig. 5(A) and Fig. 5(B) respectively show the relationship between the thermal conductivity and its reciprocal of the polycrystalline graphene film and the grain size and its reciprocal. Figure 5(C) and Figure 5(D) show the relationship between sheet resistance and conductivity of polycrystalline graphene films as a function of grain size, respectively.

Detailed ways:

In the specific implementation process, the present invention adopts chemical vapor deposition technology, uses metals such as platinum and iridium as the growth substrate, and uses hydrocarbons as the carbon source. In the presence of a carrier gas containing hydrogen, the metal substrate is first annealed. , and use the carbon source gas to catalyze the cracking on the surface of the metal substrate at high temperature to grow a graphene film; then change the growth atmosphere to an inert gas, use the impurity in the atmosphere to etch the graphene on the surface of the substrate, and then use a trace Hydrogen gas precipitates the carbon atoms dissolved in the matrix to the surface of the matrix to form high-density graphene nuclei with uniform and adjustable sizes, and then introduces carbon source gas to re-grow it, and finally obtains a polycrystalline graphene film. This high-quality single-layer polycrystalline graphene film with uniform and controllable grain size not only provides a material basis for in-depth understanding of the influence of grain size on the electrical and thermal properties of macroscopic graphene films, but also plays an important role in the regulation of graphene electrical, optoelectronic, and thermoelectric properties. Properties and other aspects have important technical prospects, laying the foundation for the application of graphene in optoelectronic and thermoelectric fields such as nanophotonic devices, optoelectronic devices, nano light sources, transparent conductive films, and gas sensors.

The present invention is further described in detail below by way of examples and accompanying drawings.

Example 1

As shown in Figure 1, the present invention adopts horizontal type reaction furnace to grow graphene, and horizontal type reaction furnace two ends are respectively provided with gas inlet 1 and gas outlet 4, and metal substrate 2 (this embodiment is platinum) is placed in horizontal type reaction furnace In the high temperature zone, the thermocouple 3 is located in the high temperature zone of the horizontal reactor to monitor the reaction temperature in real time. First, a polycrystalline platinum sheet (thickness 180 μm, length×width=20mm×20mm) was ultrasonically cleaned in acetone, water and isopropanol for 40 minutes respectively. After cleaning, put the platinum sheet into a high-temperature furnace and anneal at 1100°C for 10 hours to fully remove the carbon atoms dissolved into the platinum matrix. Then, the platinum sheet after the annealing is placed in the horizontal reaction furnace (the diameter of the furnace tube is 22 millimeters, and the length of the reaction zone is 40 millimeters) in the central area (reaction zone, there is a thermocouple at this position to monitor the furnace temperature in real time); in the atmosphere of hydrogen Heating to 900 DEG C (hydrogen flow rate is 700 milliliters/minute in the heating process, heating rate 50 DEG C/min), heat treatment for 30 minutes; feed the mixed gas of methane and hydrogen after heat treatment finishes (gas flow rate is respectively methane 7 milliliters/minute, Hydrogen 700 milliliters/minute), start to grow graphene, and the growth time is 10 minutes, feeds argon gas (gas flow rate is 700 milliliters/minute) rapidly after growing, and turns off methane and hydrogen gas simultaneously. Graphene is etched, and the etching time is 20 minutes. After the etching is completed, hydrogen gas will be introduced, and the flow rate is adjusted to 5 ml/min, so that small graphene grains are precipitated on the surface of the platinum substrate. The precipitation time is 20 minutes, and finally Methane gas is fed again, the flow rate is adjusted to 0.1 ml/min, graphene appears to re-grow, and the re-growth time is 1 hour. After the growth is completed, it is rapidly cooled to below 200°C at a rate of 100°C/s to obtain high-quality single-layer polycrystalline graphene (see Figure 2).

Scanning electron microscopy, resonance laser Raman spectroscopy, and transmission electron microscopy observations show that the obtained graphene is a high-quality polycrystalline structure. The graphene grain size is about 200 nanometers, and the graphene crystal structure is continuous and intact, with high quality, and all are single layers. The thermal conductivity of the polycrystalline graphene film is only 600W·m ^-1 K ^-1 , and the electrical conductivity can reach 1.2×10 ⁶ S·m ^-1 .

Example 2

As shown in Figure 1, the present invention adopts horizontal type reaction furnace to grow graphene, and horizontal type reaction furnace two ends are respectively provided with gas inlet 1 and gas outlet 4, and metal substrate 2 (this embodiment is platinum) is placed in horizontal type reaction furnace In the high temperature zone, the thermocouple 3 is located in the high temperature zone of the horizontal reactor to monitor the reaction temperature in real time. First, a polycrystalline platinum sheet (thickness 180 μm, length×width=20mm×20mm) was ultrasonically cleaned in acetone, water and isopropanol for 40 minutes respectively. After cleaning, put the platinum sheet into a high-temperature furnace and anneal at 1100°C for 10 hours to fully remove the carbon atoms dissolved into the platinum matrix. Then, the platinum sheet after the annealing is placed in the horizontal reaction furnace (the diameter of the furnace tube is 22 millimeters, and the length of the reaction zone is 40 millimeters) in the central area (reaction zone, there is a thermocouple at this position to monitor the furnace temperature in real time); in the atmosphere of hydrogen Heating to 950 DEG C (hydrogen flow rate is 700 ml/min in the heating process, heating rate 50 DEG C/min), heat treatment for 30 minutes; after heat treatment is completed, feed a mixed gas of methane and hydrogen (gas flow rate is respectively methane 7 ml/min, Hydrogen 700 milliliters/minute), start to grow graphene, and the growth time is 8 minutes, feeds argon gas (gas flow rate is 700 milliliters/minute) rapidly after growing, and turns off methane and hydrogen gas simultaneously. The graphene is etched, and the etching time is 20 minutes. After the etching is completed, hydrogen gas will be introduced, and the flow rate is adjusted to 10 ml/min, so that the small graphene grains are precipitated on the surface of the platinum substrate. The precipitation time is 20 minutes, and finally Methane gas is fed again, the flow rate is adjusted to 0.1 ml/min, graphene appears to re-grow, and the re-growth time is 1 hour. After the growth is completed, it is rapidly cooled to below 200° C. at a rate of 100° C./s to obtain high-quality single-layer polycrystalline graphene (see FIG. 4 ).

Scanning electron microscopy, resonance laser Raman spectroscopy, and transmission electron microscopy observations show that the obtained graphene is a high-quality polycrystalline structure. The graphene grain size is about 500 nanometers, and the graphene crystal structure is continuous and intact without damage, has high quality, and is a single layer. The thermal conductivity of the polycrystalline graphene film is only 1500W·m ^-1 K ^-1 , and the electrical conductivity can reach 1.6×10 ⁶ S·m ^-1 .

Example 3

As shown in Figure 1, the present invention adopts horizontal type reaction furnace to grow graphene, and horizontal type reaction furnace two ends are respectively provided with gas inlet 1 and gas outlet 4, and metal substrate 2 (this embodiment is platinum) is placed in horizontal type reaction furnace In the high temperature zone, the thermocouple 3 is located in the high temperature zone of the horizontal reactor to monitor the reaction temperature in real time. First, a polycrystalline platinum sheet (thickness 180 μm, length×width=20mm×20mm) was ultrasonically cleaned in acetone, water and isopropanol for 40 minutes respectively. After cleaning, put the platinum sheet into a high-temperature furnace and anneal at 1100°C for 10 hours to fully remove the carbon atoms dissolved into the platinum matrix. Then, the platinum sheet after the annealing is placed in the horizontal reaction furnace (the diameter of the furnace tube is 22 millimeters, and the length of the reaction zone is 40 millimeters) in the central area (reaction zone, there is a thermocouple at this position to monitor the furnace temperature in real time); in the atmosphere of hydrogen Heating to 1000 DEG C (hydrogen flow rate is 700 milliliters/minute in the heating process, heating rate 50 DEG C/min), heat treatment 30 minutes; After heat treatment is finished, feed the mixed gas of methane and hydrogen (gas flow rate is respectively methane 7 milliliters/minute, Hydrogen 700 milliliters/minute), start to grow graphene, growth time is 5 minutes, feeds argon gas (gas flow rate is 700 milliliters/minute) rapidly after growing, and turns off methane and hydrogen gas simultaneously. The graphene is etched, and the etching time is 20 minutes. After the etching is completed, the hydrogen gas will be introduced, and the flow rate will be adjusted to 15 ml/min, so that the small graphene grains are precipitated on the surface of the platinum substrate. The precipitation time is 20 minutes, and finally Feed methane gas again, the flow rate is adjusted to 0.1 ml/min, and the graphene appears to re-grow, and the re-growth time is 50 minutes. After the growth is completed, it is rapidly cooled to below 200° C. at a rate of 100° C./s to obtain high-quality single-layer polycrystalline graphene (see FIG. 4 ).

Scanning electron microscopy, resonance laser Raman spectroscopy, and transmission electron microscopy observations show that the obtained graphene is a high-quality polycrystalline structure. The graphene grain size is about 700 nanometers, the graphene crystal structure is continuous and intact, has high quality, and is a single layer. The thermal conductivity of the polycrystalline graphene film is only 2000W·m ^-1 K ^-1 , and the electrical conductivity can reach 2.1×10 ⁶ S·m ^-1 .

Example 4

As shown in Figure 1, the present invention adopts horizontal type reaction furnace to grow graphene, and horizontal type reaction furnace two ends are respectively provided with gas inlet 1 and gas outlet 4, and metal substrate 2 (this embodiment is platinum) is placed in horizontal type reaction furnace In the high temperature zone, the thermocouple 3 is located in the high temperature zone of the horizontal reactor to monitor the reaction temperature in real time. First, a polycrystalline platinum sheet (thickness 180 μm, length×width=20mm×20mm) was ultrasonically cleaned in acetone, water and isopropanol for 40 minutes respectively. After cleaning, put the platinum sheet into a high-temperature furnace and anneal at 1100°C for 10 hours to fully remove the carbon atoms dissolved into the platinum matrix. Then, the platinum sheet after the annealing is placed in the horizontal reaction furnace (the diameter of the furnace tube is 22 millimeters, and the length of the reaction zone is 40 millimeters) in the central area (reaction zone, there is a thermocouple at this position to monitor the furnace temperature in real time); in the atmosphere of hydrogen Heating to 1040 DEG C (hydrogen flow rate is 700 milliliters/minute in the heating process, heating rate 50 DEG C/min), heat treatment 30 minutes; Pass the mixed gas of methane and hydrogen after heat treatment is finished (gas flow rate is respectively methane 7 milliliters/minute, Hydrogen 700 milliliters/minute), start to grow graphene, growth time is 3 minutes, feeds argon gas (gas flow rate is 700 milliliters/minute) rapidly after growth finishes, and turns off methane and hydrogen gas simultaneously. The graphene is etched, and the etching time is 20 minutes. After the etching is completed, hydrogen gas will be introduced, and the flow rate is adjusted to 20 ml/min, so that the small graphene grains are precipitated on the surface of the platinum substrate. The precipitation time is 20 minutes, and finally Feed methane gas again, the flow rate is adjusted to 0.1 ml/min, graphene appears to re-grow, and the re-growth time is 30 minutes. After the growth is completed, it is rapidly cooled to below 200° C. at a rate of 100° C./s to obtain high-quality single-layer polycrystalline graphene (see FIG. 4 ).

Scanning electron microscopy, resonance laser Raman spectroscopy, and transmission electron microscopy observations show that the obtained graphene is a high-quality polycrystalline structure. The grain size of graphene is about 1 micron, the crystal structure of graphene is continuous and intact, has high quality, and is a single layer. The thermal conductivity of the polycrystalline graphene film is only 2500W·m ^-1 K ^-1 , and the electrical conductivity can reach 2.5×10 ⁶ S·m ^-1 .

Example 5

As shown in Figure 1, the present invention adopts horizontal type reaction furnace to grow graphene, and horizontal type reaction furnace two ends are respectively provided with gas inlet 1 and gas outlet 4, and metal substrate 2 (this embodiment is platinum) is placed in horizontal type reaction furnace In the high temperature zone, the thermocouple 3 is located in the high temperature zone of the horizontal reactor to monitor the reaction temperature in real time. First, a polycrystalline platinum sheet (thickness 180 μm, length×width=20mm×20mm) was ultrasonically cleaned in acetone, water and isopropanol for 40 minutes respectively. After cleaning, put the platinum sheet into a high-temperature furnace and anneal at 1100°C for 10 hours to fully remove the carbon atoms dissolved into the platinum matrix. Then, the platinum sheet after the annealing is placed in the horizontal reaction furnace (the diameter of the furnace tube is 22 millimeters, and the length of the reaction zone is 40 millimeters) in the central area (reaction zone, there is a thermocouple at this position to monitor the furnace temperature in real time); in the atmosphere of hydrogen Heating to 800 DEG C (hydrogen flow rate is 700 milliliters/minute in the heating process, heating rate 50 DEG C/min), heat treatment 30 minutes; After heat treatment is finished, feed the mixed gas of methane and hydrogen (gas flow rate is respectively methane 10 milliliters/minute, Hydrogen 700 milliliters/minute), start to grow graphene, and the growth time is 10 minutes, feeds argon gas (gas flow rate is 700 milliliters/minute) rapidly after growing, and turns off methane and hydrogen gas simultaneously. Graphene is etched, and the etching time is 50 minutes. After the etching is completed, hydrogen gas will be introduced, and the flow rate is adjusted to 3 ml/min, so that small graphene grains are precipitated on the surface of the platinum substrate. The precipitation time is 1 hour, and finally Then feed methane gas, the flow rate is adjusted to 0.1 ml/min, graphene appears to re-grow, and the re-growth time is 3 hours. After the growth is completed, it is rapidly cooled to below 200°C at a rate of 200°C/s to obtain high-quality single-layer polycrystalline graphene.

Scanning electron microscopy, resonance laser Raman spectroscopy, and transmission electron microscopy observations show that the obtained graphene is a high-quality polycrystalline structure. The graphene grain size is about 50 nanometers, and the graphene crystal structure is continuous and intact without damage, with high quality, and all are single layers.

Example 6

As shown in Figure 1, the present invention adopts horizontal type reaction furnace to grow graphene, and horizontal type reaction furnace two ends are respectively provided with gas inlet 1 and gas outlet 4, and metal substrate 2 (this embodiment is platinum) is placed in horizontal type reaction furnace In the high temperature zone, the thermocouple 3 is located in the high temperature zone of the horizontal reactor to monitor the reaction temperature in real time. First, a polycrystalline platinum sheet (thickness 180 μm, length×width=20mm×20mm) was ultrasonically cleaned in acetone, water and isopropanol for 40 minutes respectively. After cleaning, put the platinum sheet into a high-temperature furnace and anneal at 1100°C for 10 hours to fully remove the carbon atoms dissolved into the platinum matrix. Then, the platinum sheet after the annealing is placed in the horizontal reaction furnace (the diameter of the furnace tube is 22 millimeters, and the length of the reaction zone is 40 millimeters) in the central area (reaction zone, there is a thermocouple at this position to monitor the furnace temperature in real time); in the atmosphere of hydrogen Heating to 700°C (hydrogen flow rate in the heating process is 700 ml/min, heating rate 50°C/min), heat treatment for 30 minutes; after heat treatment is completed, feed a mixed gas of methane and hydrogen (gas flow rate is respectively 20 ml/min of methane, Hydrogen 700 milliliters/minute), start to grow graphene, and the growth time is 15 minutes, feeds argon gas (gas flow rate is 700 milliliters/minute) rapidly after growing, and turns off methane and hydrogen gas simultaneously. Graphene is etched, and the etching time is 1 hour. After the etching is completed, hydrogen gas will be introduced, and the flow rate will be adjusted to 1 ml/min, so that small graphene grains will be precipitated on the surface of the platinum substrate. The precipitation time will be 2 hours, and finally Feed methane gas again, the flow rate is adjusted to 0.1 milliliters/minute, graphene appears to re-grow, and the re-growth time is 5 hours. After the growth is completed, it is rapidly cooled to below 200°C at a rate of 200°C/s to obtain high-quality single-layer polycrystalline graphene (see Figure 2).

Scanning electron microscopy, resonance laser Raman spectroscopy, and transmission electron microscopy observations show that the obtained graphene is a high-quality polycrystalline structure. The grain size of graphene is about 10 nanometers, the crystal structure of graphene is continuous and intact, has high quality, and is a single layer.

Example 7

As shown in Figure 1, the present invention adopts horizontal type reaction furnace to grow graphene, and horizontal type reaction furnace two ends are respectively provided with gas inlet 1 and gas outlet 4, and metal substrate 2 (this embodiment is iridium) is placed in horizontal type reaction furnace In the high temperature zone, the thermocouple 3 is located in the high temperature zone of the horizontal reactor to monitor the reaction temperature in real time. First, a polycrystalline iridium sheet (thickness 180 microns, length×width=20mm×20mm) was placed in acetone, water and isopropanol for ultrasonic cleaning for 40 minutes respectively. After cleaning, put the iridium sheet into a high-temperature furnace and anneal at 1200°C for 10 hours to fully remove the carbon atoms dissolved into the iridium matrix. Then, the iridium sheet after the annealing is placed in the horizontal reaction furnace (22 mm in diameter of the furnace tube, and the length of the reaction zone is 40 mm) in the central area (reaction zone, there is a thermocouple at this position to monitor the furnace temperature in real time); in the atmosphere of hydrogen Heating to 900 DEG C (hydrogen flow rate is 700 milliliters/minute in the heating process, heating rate 50 DEG C/min), heat treatment for 30 minutes; feed the mixed gas of methane and hydrogen after heat treatment finishes (gas flow rate is respectively methane 7 milliliters/minute, Hydrogen 700 milliliters/minute), start to grow graphene, and the growth time is 10 minutes, feeds argon gas (gas flow rate is 700 milliliters/minute) rapidly after growing, and turns off methane and hydrogen gas simultaneously. Graphene is etched, and the etching time is 20 minutes. After the etching is completed, hydrogen gas will be introduced, and the flow rate is adjusted to 5 ml/min, so that small graphene grains are precipitated on the surface of the iridium substrate. The precipitation time is 20 minutes, and finally Methane gas is fed again, the flow rate is adjusted to 0.1 ml/min, graphene appears to re-grow, and the re-growth time is 1 hour. After the growth is completed, it is rapidly cooled to below 200°C at a rate of 100°C/s to obtain high-quality single-layer polycrystalline graphene.

Scanning electron microscopy, resonance laser Raman spectroscopy, and transmission electron microscopy observations show that the obtained graphene is a high-quality polycrystalline structure. The graphene grain size is about 100 nanometers, and the graphene crystal structure is continuous and intact, with high quality, and all are single layers.

Example 8

As shown in Figure 1, the present invention adopts horizontal type reaction furnace to grow graphene, and horizontal type reaction furnace two ends are respectively provided with gas inlet 1 and gas outlet 4, and metal substrate 2 (this embodiment is iridium) is placed in horizontal type reaction furnace In the high temperature zone, the thermocouple 3 is located in the high temperature zone of the horizontal reactor to monitor the reaction temperature in real time. First, a polycrystalline iridium sheet (thickness 180 microns, length×width=20mm×20mm) was placed in acetone, water and isopropanol for ultrasonic cleaning for 40 minutes respectively. After cleaning, put the iridium sheet into a high-temperature furnace and anneal at 1200°C for 10 hours to fully remove the carbon atoms dissolved into the iridium matrix. Then, the iridium sheet after the annealing is placed in the horizontal reaction furnace (22 mm in diameter of the furnace tube, and the length of the reaction zone is 40 mm) in the central area (reaction zone, there is a thermocouple at this position to monitor the furnace temperature in real time); in the atmosphere of hydrogen Heating to 800 DEG C (hydrogen flow rate is 700 milliliters/minute in the heating process, heating rate 50 DEG C/min), heat treatment 30 minutes; After heat treatment is finished, feed the mixed gas of methane and hydrogen (gas flow rate is respectively methane 10 milliliters/minute, Hydrogen 700 milliliters/minute), start to grow graphene, and the growth time is 10 minutes, feeds argon gas (gas flow rate is 700 milliliters/minute) rapidly after growing, and turns off methane and hydrogen gas simultaneously. Graphene is etched, and the etching time is 50 minutes. After the etching is completed, hydrogen gas will be introduced, and the flow rate is adjusted to 3 ml/min, so that small graphene grains are precipitated on the surface of the iridium substrate. The precipitation time is 1 hour, and finally Feed methane gas again, the flow rate is adjusted to 0.1 milliliters/minute, graphene appears to re-grow, and the re-growth time is 5 hours. After the growth is completed, it is rapidly cooled to below 200°C at a rate of 200°C/s to obtain high-quality single-layer polycrystalline graphene.

Scanning electron microscopy, resonance laser Raman spectroscopy, and transmission electron microscopy observations show that the obtained graphene is a high-quality polycrystalline structure. The graphene grain size is about 20 nanometers, and the graphene crystal structure is continuous and intact without damage, has high quality, and is a single layer.

As shown in Figure 1, one end of the gas inlet 1 in the figure is provided with a plurality of mass flow meters 5, which can selectively control the introduction of gases such as hydrogen, methane, ethylene, acetylene or argon. The liquid carbon source (such as: ethanol, methanol, benzene, toluene or cyclohexane, etc.) is placed in a Montessori washing bottle and brought in by bubbling argon or a mixture of argon and nitrogen.

As shown in Figure 2, after growth-etching-precipitation, graphene has a large number of high-density crystal nuclei, and the grain size is only about 50 nanometers. The graphene film after re-growth is complete and monolayer, which proves that this method can prepare single-layer polycrystalline graphene film.

As shown in Figure 3, it can be seen from the Raman spectrum of graphene that the graphene crystal grain density prepared by this method is extremely high, showing that the intensity of the 1340cm ^-1 (D mode) position in the Raman spectrum is very high, However, after the graphene crystal grains are assembled into a film, the D mode almost disappears, indicating that the single-layer polycrystalline graphene film prepared by this method has high quality.

As shown in Figure 4, the nuclei density of graphene can be precisely tuned by the precipitation temperature. From the transmission electron microscope photos of graphene on platinum, it can be seen that the polycrystalline graphene film is spliced by graphene grains with different orientations, and the splicing parts are all five or seven rings, which further shows that the graphene film has a high quality.

As shown in Figure 5, the thermal conductivity of polycrystalline graphene grown by this method is only 600W·m ^-1 K ^-1 , and the electrical conductivity can reach 1.2×10 ⁶ S·m ^-1 , which shows that the grain boundaries can be large The thermal properties are greatly reduced but the electrical properties are not greatly affected, which lays the foundation for the application of graphene in optoelectronic and thermoelectric fields such as nanoelectronic devices, photonic devices, gas sensors, and thin film electronic devices.

The results of the examples show that the present invention proposes to grow, etch, and precipitate graphene by comprehensively regulating the concentration of hydrogen, argon, and carbon sources, and adjust the distribution density of graphene crystal nuclei by changing the precipitation temperature, and then adjust the reaction atmosphere again to make It re-grows, and finally obtains a high-quality single-layer polycrystalline graphene film with tunable grain size. Breakthroughs in this direction lay the foundation for promoting the application of graphene, especially in the fields of optoelectronics and thermoelectrics such as nanoelectronic devices, photonic devices, gas sensors, and thin film electronic devices.

Claims (10)

1. a kind of preparation method of high quality monolayer polycrystalline graphite alkene film, which is characterized in that chemical vapour deposition technique is used, In the presence of hydrogen, the first step makes annealing treatment metallic matrix, and utilizes the carbon-source gas high temperature of larger air-flow Under in metal base surface catalytic pyrolysis, gas flow rate is not less than 20sccm, grows graphene film；Second step will be by that will give birth to Long atmosphere is changed to inert gas, is performed etching to matrix skin graphene, the carbon for making to be dissolved in intrinsic silicon using trace hydrogen Atom is precipitated to matrix surface, forms the adjustable graphene nucleus of density；Third step, which introduces carbon-source gas, makes graphene nucleus table Face regrowth, it is final to obtain polycrystalline graphite alkene film；The crystallite dimension of graphene film is effectively adjusted using this method, is obtained brilliant Uniform controllable, crystal boundary perfection split the high quality monolayer polycrystalline graphite alkene film of particle size.

2. the preparation method of high quality monolayer polycrystalline graphite alkene film described in accordance with the claim 1, it is characterised in that：Gold used Belong to the thin slice or film that matrix is the platinum of surfacing, ruthenium or iridium metals, purity is more than 98wt%, and thickness is not less than 300nm, base The molten carbon amounts of body is in 0.01wt% between 0.2wt%.

3. the preparation method of high quality monolayer polycrystalline graphite alkene film described in accordance with the claim 1, it is characterised in that：Gold used Belong to matrix in the one or more of acetone, ethyl lactate, water, isopropanol and ethyl alcohol to be respectively cleaned by ultrasonic, the time is many In 10 minutes.

4. the preparation method of high quality monolayer polycrystalline graphite alkene film described in accordance with the claim 1, it is characterised in that：Gold used It is 800 DEG C~1600 DEG C to belong to matrix annealing temperature, and atmosphere is hydrogen；Alternatively, atmosphere is hydrogen and nitrogen or inert gas Mixed gas, wherein hydrogen molar ratio be not less than 1%, annealing time is no less than 10 minutes.

5. the preparation method of high quality monolayer polycrystalline graphite alkene film described in accordance with the claim 1, it is characterised in that：Carbon used Source be methane, ethane, acetylene, ethylene, in ethyl alcohol hydrocarbon one or more, carrier is hydrogen, alternatively, carrying Body is the mixed gas of hydrogen and nitrogen or inert gas, and the bulk purity of carbon source and carrier gas is all higher than 98%.

6. the preparation method of high quality monolayer polycrystalline graphite alkene film described in accordance with the claim 1, it is characterised in that：The first step In growth temperature be 500 DEG C~1300 DEG C, the molar ratio of carbon source and hydrogen is 0.004~1, and growth time is not less than 10 points Clock.

7. the preparation method of high quality monolayer polycrystalline graphite alkene film described in accordance with the claim 1, it is characterised in that：Second step Middle etching temperature is 500 DEG C~1300 DEG C, and etch period is not less than 10 minutes, and atmosphere is the impure of inert gas and its dispersion Object；The Precipitation Temperature of graphene is 500 DEG C~1300 DEG C in second step, and the precipitation time is not less than 10 minutes, hydrogen and indifferent gas The molar ratio of body is 0.005~0.1.

8. the preparation method of high quality monolayer polycrystalline graphite alkene film described in accordance with the claim 1, it is characterised in that：Third walks Middle regrowth temperature is 500 DEG C~1300 DEG C, and regrowth time is not less than 20 minutes, and the molar ratio of carbon source and hydrogen is 0.005 ~0.1.

9. the preparation method of high quality monolayer polycrystalline graphite alkene film described in accordance with the claim 1, it is characterised in that：Grown junction Shu Hou, metallic matrix are quickly cooled to 200 DEG C hereinafter, hydrogen molar ratio is not small in carrier gas under the carrier protection containing hydrogen In 1%, the rate being quickly cooled down is not less than 50 DEG C/sec.

10. the preparation method of high quality monolayer polycrystalline graphite alkene film described in accordance with the claim 1, it is characterised in that：It is made The crystallite dimension of standby graphene film can continuously adjust on a large scale, and grain size distribution is at 10 nanometers~1 micron.