KR101798720B1

KR101798720B1 - Method for manufacturing graphene using pre-doping and multy-layer graphene manufactured by the same

Info

Publication number: KR101798720B1
Application number: KR1020150158376A
Authority: KR
Inventors: 염근영; 김경남; 이세한; 오종식; 오지수; 비에트 펑 팜
Original assignee: 성균관대학교산학협력단
Priority date: 2015-11-11
Filing date: 2015-11-11
Publication date: 2017-11-17
Also published as: KR20170055617A

Abstract

The present invention provides high throughput, low sheet resistance, high thermal stability and high flexibility due to a simple and efficient process involving trapping doped chlorine by moving additional graphene on chlorine pre-doped single-layer graphene And a multilayer graphene produced from the graphene using the pre-doping method, wherein the graphene can be easily produced, and the thickness and electrical characteristics of the graphene can be easily controlled.

Description

METHOD FOR MANUFACTURING GRAPHENE USING PRE-DOPING AND MULTI-LAYER GRAPHENE MANUFACTURED BY THE SAME [0002]

The present invention relates to a method of making graphene using pre-doping, and to multilayer graphenes prepared therefrom, and more particularly to a method of preparing graphene by pre-doping by transferring additional graphene onto chlorine pre- Graphene having high permeability, low surface resistance, high thermal stability and high flexibility can be easily produced by a simple and efficient process including trapping the chlorine after the chlorine doping and then chlorine doping the additional graphene again The present invention also relates to a method for producing graphene using pre-doping which facilitates control of thickness and electrical characteristics of graphene, and multilayer graphene produced therefrom.

Carbon materials of nanomaterials have excellent physical and chemical properties and are used in various industrial fields. Particularly, carbon materials such as graphene, graphite, carbon nanotube, and fullerene are attracting attention as materials for electric and electronic devices, optical devices and filter devices.

Among them, graphene has a honeycomb shape in which carbon atoms are connected in a ring arrangement, and has a planar planar structure (two-dimensional structure). And, graphite has a structure (one-dimensional structure) in which two-dimensional graphenes are laminated. Graphene is attracting attention as a new material of the future because it has superior metallic properties and thermal conductivity as well as electrical properties and elasticity than carbon materials such as graphite having a one-dimensional structure, carbon nanotubes and fullerene having a zero dimensional structure, and In addition to being very stable and excellent in electrical, mechanical and chemical properties, it is also an excellent conductive material that transports electrons much faster than silicon and allows much greater current to flow than copper, It has been proven through experimentation that it has been discovered, and many studies have been carried out to date.

Such graphene can be formed in a large area, has electrical, mechanical and chemical stability, and has excellent conductivity. Thus, graphene is attracting attention as a basic material for electronic circuits. . Some of the important properties of graphene are that they are suitable for producing transparent conductive films due to their high conductivity, high transparency and excellent flexibility. Due to these excellent properties, graphene has been studied as a replaceable alternative to indium tin oxide (ITO).

However, a serious disadvantage of graphene is that it has a relatively high sheet resistance compared to indium tin oxide under similar light transmittance conditions.

The ideal sheet resistance of graphene is much lower than the reported sheet resistance of CVD graphene. The higher surface resistance of the CVD graphene is derived from the crystal, wrinkling, and grain and domain size of the actually grown graphene layers.

For this reason, the prior art has made efforts to improve the surface resistance of graphene through various doping methods including chemical methods, plasma and photochemical methods.

However, despite the application of such a doping method, many problems still remain to be solved, such as having a higher surface resistance than ITO under similar light transmittance conditions, reduced transmittance during chemical doping, thermal instability during plasma doping, and severe damage .

For example, in the case of wet chemical doping, ACS by F. Gunes et al. Nano, 2010, 4, 4595 ~ 4600, which has obtained a surface resistance of 54 Ω using four graphene layers, showing the possibility of achieving low surface resistance by chemical doping. However, the doping process showed a relatively low transmittance of 85% due to the entanglement of Au ions in AuCl ₃ used in the process.

In addition, various other chemical doping processes for improving sheet resistance and permeability are described, for example, in J. Mater. Chem., 2011, 21, 3335-3345; Prog. Mater. Sci., 2014, 64, 200-247; Adv. Mater., 2008, 20, 4442-4449; Carbon, 2011, 49, 2905-2916; Carbon, 2011, 49, 2905-2916; Carbon, 2011, 49, 2538-2548; ACS. Nano, 2011, 7, 6039-6051. However, these methods also fail to satisfy both surface resistance and high transmittance.

[Non-Patent Document 1] ACS. Nano, 2010, 4, 4595-4600, F.Gunes etc. [Non-Patent Document 2] J. Mater. Chem., 2011, 21, 3335-3345 [Non-Patent Document 3] Prog. Mater. Sci., 2014, 64, 200-247 [Non-Patent Document 4] Adv. Mater., 2008, 20, 4442-4449 [Non-Patent Document 5] Carbon, 2011, 49, 2905-2916 [Non-Patent Document 6] Carbon, 2011, 49, 2905-2916 [Non-Patent Document 7] Carbon, 2011, 49, 2538-2548 [Non-Patent Document 8] ACS. Nano, 2011, 7, 6039-6051

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to solve the above-mentioned problems of the prior art, and it is an object of the present invention to overcome the above-mentioned conventional problems by moving additional graphene on chlorine pre- And then chlorine doping the further graphene again.

Another object of the present invention is to provide a multilayer graphene produced by a manufacturing method including chlorine pre-doping, which has low sheet resistance, high transmittance and high thermal stability while maintaining the characteristics of general graphene.

In order to achieve the above object, a method of manufacturing graphene using pre-doping according to an embodiment of the present invention includes the following steps:

(1) preparing graphene;

(2) chlorine pre-doping graphene;

(3) transferring the pre-doped graphene onto the substrate;

(4) moving additional graphene on the pre-doped graphene;

(5) annealing the result of step (4); And

(6) chlorine doping the further annealed graphene.

According to the method for manufacturing graphene using pre-doping according to an embodiment of the present invention, the step (4) to (6) may be repeated one or more times.

According to the method of manufacturing graphene using pre-doping according to an embodiment of the present invention, the step (1) may be performed by synthesizing graphene on a metal.

Graphene can be synthesized on the metal by reacting and providing a reaction gas and heat containing a carbon source on the metal.

The synthesis of the graphene can be performed by inductively coupled plasma chemical vapor deposition, low pressure chemical vapor deposition, or atmospheric pressure chemical vapor deposition.

The metal may be at least one selected from the group consisting of Au, Ag, Al, Pt, Mn, Fe, Ni, Co, Ti, Pd). &Lt; / RTI >

According to the method of manufacturing graphene using pre-doping according to an embodiment of the present invention, when the step (1) is performed by synthesizing graphene on the metal, the step of removing the metal before the step (3) As shown in FIG.

According to the method of manufacturing graphene using pre-doping according to an embodiment of the present invention, in the step (2), chlorine pre-doping can be performed by chlorine plasma treatment.

The chlorine plasma treatment may be doped with chlorine on the graphene by implanting chlorine gas.

According to the method of manufacturing graphene using pre-doping according to an embodiment of the present invention, the step (2) may further include coating a polymer on the chlorine pre-doped graphene.

The polymer material may be at least one selected from polymethylmethacrylate (PMMA), poly (dimethylsiloxane) (PDMS), poly (bisphenol A carbonate) (PC), and polystyrene (PS).

According to the method of manufacturing graphene using pre-doping according to an embodiment of the present invention, when the method further comprises a step of coating the polymer on the chlorine pre-doped graphene after the step (2) The step 4) may further include removing the polymer.

In the step (3), the substrate may be made of at least one selected from glass, polyethylene terephthalate, quartz, and SiO ₂ / Si wafers.

In the step (4), the additional graphene may be formed by attaching graphene on a separate substrate and coating the polymer on the graphene.

According to the method of manufacturing graphene using pre-doping according to an embodiment of the present invention, when the additional graphene is a polymer coated on a graphene attached on a separate substrate, After the step, the step of removing the polymer contained in the further graphene may be further included.

In the step (5), the annealing may be performed at 200 to 500 ° C for 1 to 10 hours.

The multi-layer graphene according to another embodiment of the present invention can be manufactured by a method of manufacturing graphene using pre-doping according to the present invention.

According to the method of manufacturing graphene using pre-doping of the present invention, by manufacturing multilayer graphene including trapping doped chlorine by moving additional graphene on chlorine pre-doped single-layer graphene, Has an effect of exhibiting low sheet resistance, high transmittance, and thermal stability while maintaining the characteristics of graphene.

1 (a) is a view showing a process of a graphene manufacturing method using general doping.
Fig. 1 (b) is a view showing a step of the method for producing graphene of Example 1 of the present invention.
Figure 2 shows an ICP system used in an embodiment of the present invention in which a dual mesh grid assembly is introduced between a plasma source and a substrate having a geometric transparency of at least 62% 2 cm apart.
The mesh grid assembly acts like a solid potential surface in a plasma, and more effectively limits the plasma, so that chlorine plasma doping can be achieved with a minimum of low energy.
FIG. 3 is a graph showing sheet resistance and light transmittance analysis according to various dopants. FIG.
4 is a graph showing respective sheet resistances of pre-doped single-layer pre-doping, Comparative Example 1 and the graphene produced in Example 1. Fig.
5 is a graph showing the sheet resistance values of the single-layer graphene, the graphene of Example 1 and Example 2 together.
6 (a) is a graph showing the results of measurement of Raman spectra for undoped pristine, pre-doped single-layer graphene, and graphene of Example 1. FIG. 6 (b) And Fig. 6 (c) is an enlarged graph of a certain section of Fig. 6 (a).
FIG. 7 is a graph showing the degree of the CC, C-Cl and CO bonding states of carbon in undoped graphene, pre-doped single-layer graphene, and graphene of Example 1 and Comparative Example 1 using XPS to be.
FIG. 8 is a diagram showing the element bonding structure of undoped graphene, pre-doped single-layer graphene, and Comparative Example 1 and graphene of Example 1. FIG.
9 is a graph showing the results of annealing for 100 hours in order to measure the thermal stability of the graphene of Comparative Example 1 without pre-doping and the graphene of Example 1. Fig.
10 is a graph showing the light transmittance of a polyethylene terephthalate (PET) film, pre-doped single-layer graphene, and graphenes of Examples 1 and 2.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. To fully disclose the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

Unless defined otherwise, all terms (including technical and scientific terms) used herein may be used in a sense commonly understood by one of ordinary skill in the art to which this invention belongs. Also, commonly used predefined terms are not ideally or excessively interpreted unless explicitly defined otherwise.

Hereinafter, a method for producing graphene by pre-doping according to the present invention will be described in detail.

A method of manufacturing graphene using pre-doping according to an embodiment of the present invention is characterized by comprising the following steps:

(1) preparing graphene;

(2) chlorine pre-doping graphene;

(3) transferring the pre-doped graphene onto the substrate;

(4) moving additional graphene on the pre-doped graphene;

(5) annealing the result of step (4); And

(6) chlorine doping the further annealed graphene.

The carbon source may comprise a carbon-containing compound having from 1 to 10 carbon atoms, for example the carbon source may be selected from the group consisting of carbon monoxide, carbon dioxide, methane, ethane, ethylene, ethanol, acetylene, propane, , Butadiene, pentane, pentene, pentene, pentadiene, cyclopentane, cyclopentadiene, hexane, hexene, cyclohexane, cyclohexadiene, benzene, toluene and combinations thereof.

The step of removing the metal is not particularly limited, and for example, the metal may be removed using an etchant. As the etchant, an acid solution may be used, and the acid solution may include at least one selected from H ₂ SO ₄ , HNO ₃ , HPO ₄ , and HCl, though not limited thereto.

The chlorine plasma treatment may be performed by supplying chlorine gas at a process pressure of 10 to 100 mTorr and an RF power of less than 100 W, Gas at a flow rate of 10 to 90 sccm for 5 seconds to 130 seconds, and the driving frequency, the input power, and the process pressure of the input power for discharging the plasma may be changed.

The chlorine plasma process is a process capable of reducing defects by minimizing damage on the graphene surface. In general, ion energy plays an important role in doping by plasma. Therefore, the energy of the ions incident on the graphene is preferably less than 4.9 eV, because the C-C bond strength of graphene is very sensitive (4.9 eV).

If the pre-doping is performed before transferring the graphene onto the substrate as described above, the pre-doped chlorine remains even when the graphene is transferred onto the substrate, thereby further improving the sheet resistance at the graphene surface.

The polymer material may be at least one selected from polymethylmethacrylate, poly (dimethylsiloxane) (PDMS), poly (bisphenol A carbonate) (PC), and polystyrene (PS).

In the step (5), the annealing is preferably performed at 200 to 500 ° C for 1 to 10 hours. If the annealing temperature is out of the above range, the transferred graphene is damaged.

According to the present invention, there is provided a multi-layer graphene produced by the above-described method for producing graphene using pre-doping.

Hereinafter, the present invention will be described in detail with reference to examples and experimental results of graphene according to the present invention. However, the following examples are for illustrative purposes only, and the present invention is not limited to the following examples.

&Lt; Measurement of physical properties &

The sheet resistance of the graphene film was measured using a sheet resistance meter (Dasoleng, FPP-2400) at room temperature for graphene on a PET substrate (or a SiO ₂ / Si wafer). Optical properties were measured with UV-Vis-NIR absorption spectroscopy (Shimadzu, 3600) and Raman spectroscopy (Renishaw, RM-1000 Invia) with excitation energy of 2.41 eV (514 nm, Ar ⁺ ion laser) The damage caused by the plasma on the film was investigated. The graphene surface was irradiated with X-ray photoelectron spectroscopy (XPS, ESCA2000, VH Microtech Inc.) using a Mg K? Twin-anode source. To observe the carbon bonding state near the graphene surface, the take-off angle was adjusted to 45 °.

&Lt; Chlorine doping apparatus and method >

Figure 2 shows an ICP source, as used in the Examples and Comparative Examples, in which a dual mesh grid assembly is mounted in a chamber between a source and a substrate to perform chlorine plasma doping. An ICP source made of a Cu induction coil and a dielectric window separated from the processing chamber is located at the top of the processing chamber. The processing chamber and the substrate holder are made of anodized aluminum, and the inner diameter of the process chamber and the diameter of the substrate holder are 32 cm and 16 cm, respectively. The chlorine (Cl ₂ ) plasma lasted at a pressure of 13.56 MHz and 10 mTorr of RF power of 20 W for the ICP source. The chlorine (Cl ₂ ) gas flow rate was maintained at 60 sccm and the chlorine doping was performed at 10 to 120 seconds. A graphene film on the PET substrate or SiO ₂ / Si substrate, a load in a vacuum - were inserted in the processing chamber by using the lock system, the substrate is cooled by the cooler of 15 ℃.

Example 1 and 2 and Comparative Example 1 to 6

Example One: free - using doping and additional doping Double layer Grapina Produce

(One) free - Doped fault Grapina Produce

Copper foils of 100 x 90 cm < 2 > and 75 [mu] m thickness were placed in a vacuum quartz CVD vacuum chamber. First, the discharged chamber was filled with H ₂ gas at a flow rate of 10 sccm, and then the copper foil was annealed at 1050 ° C under H ₂ . The graphene was then synthesized at the same temperature under H ₂ / CH ₄ (10/20 sccm) for 30 minutes and then the chamber was cooled to room temperature with H ₂ gas (10 sccm) for 1 hour. After synthesizing graphene, the graphene-synthesized copper foil was cut into small pieces of 3 x 3 cm 2. Small pieces of the copper foil synthesized by these graphenes were attached to a glass substrate using a tape. The glass substrate was used as an assembly of the small pieces. The graphene was doped with chlorine by injecting chlorine gas at 10 mTorr for 90 seconds at a flow rate of 60 sccm at 20 W of rf power on the graphene deposited on the glass substrate. Then polymethylmethacrylate (PMMA) was spin-coated on the grains doped with chlorine and then immersed in a copper etchant (FeCl ₃ ) to remove the copper foil. The copper foil was washed several times in deionized water to completely remove the etchant , And then attached to a polyethylene terephthalate (PET) substrate. Then, polymethylmethacrylate coated on the graphene surface with acetone and deionized water was removed to obtain a single-layer graphene pre-doped with chlorine adhered onto the substrate.

(2) Addition Doped Double layer Grapina Produce

On the pre-doped monolayer graphene deposited on the substrate obtained above, additional graphene (in the form of coated polymer (PMMA) on graphene deposited on a separate substrate) was transferred. The PMMA was removed with acetone and deionized water for 30 minutes to remove the coated PMMA on the further graphene. After removing the PMMA, chlorine was doped into the graphene by injecting chlorine gas for 90 seconds at 10 mTorr at a flow rate of 60 sccm at 20 W of rf power on the additional graphene. Then, chlorine-doped graphene was annealed at 230 DEG C for 3 hours to prepare double layer graphene.

Example 2: free - using doping and additional doping Triple layer Grapina Produce

After transferring and attaching further graphene on the graphene of the double layer obtained in Example 1 (in the form of coated with polymer (PMMA) on graphene attached on a separate substrate), acetone and deionized water And PMMA was removed for 30 minutes. Then, chlorine gas was injected onto the additional graphene at a flow rate of 60 sccm at 20 W of rf power and 90 seconds at 10 mTorr, chlorine doped, and annealed at 230 캜 for 3 hours to pre-dop , Further doped triplet graphene was prepared.

Comparative Example One

Grapina Produce

Copper foils of 100 x 90 cm < 2 > and 75 [mu] m thickness were placed in a vacuum quartz CVD vacuum chamber. First, the discharged chamber was filled with H ₂ gas at a flow rate of 10 sccm, and then the copper foil was annealed at 1050 ° C under H ₂ . The graphene was then synthesized at the same temperature under H ₂ / CH ₄ (10/20 sccm) for 30 minutes and then the chamber was cooled to room temperature with H ₂ gas (10 sccm) for 1 hour. After synthesizing graphene, the graphene-synthesized copper foil was cut into small pieces of 3 x 3 cm 2. Small pieces of the copper foil synthesized by these graphenes were attached to a glass substrate using a tape. The glass substrate was used as an assembly of the small pieces. Polymethylmethacrylate (PMMA) was spin-coated on the graphene adhered on the glass substrate, then immersed in a copper etching solution (FeCl ₃ ) to remove the copper foil, and then adhered to a PET substrate. Then, And polymethylmethacrylate coated on the graphene surface with deionized water were removed to obtain graphene adhered on the substrate.

Doped Double layer Grapina Produce

Further graphene (in the form of a polymer coated on graphene adhered on a separate substrate) was transferred and adhered onto the graphene adhered on the substrate obtained above, and then coated with 30 Min. &Lt; / RTI > To effect chlorine doping on the additional graphene from which the PMMA had been removed, chlorine gas was injected at a flow rate of 60 sccm at 20 W of rf power and for 90 seconds at 10 mTorr. Then, chlorine-doped graphene was annealed at 230 DEG C for 3 hours to prepare double layer graphene.

Experimental Example One: On the dopant Following Sheet resistance And light transmission analysis

In addition to the doping using the chlorine plasma used in the present invention, the light transmittance and the sheet resistance of variously doped single-layer graphenes were measured by using nitric acid (HNO ₃ ), gold chloride (AuCl ₃ ), or polyvinyl alcohol as a dopant, The results are shown in Fig.

As shown in FIG. 3, the surface resistance of graphene doped with chlorine plasma was the most excellent at 240 Ω / sq of sheet resistance and transmittance of 97.7% at 550 nm than that of graphene using other dopants.

Experimental Example 2: Sheet resistance analysis

The sheet resistances of the graphenes of Example 1 and Comparative Example 1 were measured. The results are shown in FIG. 4, and the sheet resistance of graphene of Example 2 was measured. The results are shown in FIG.

Referring to FIG. 4, in the case of the sheet resistance of Comparative Example 1, since the doping concentration with respect to the graphene surface was increased, it decreased to 610-280? / Sq due to an increase in chlorine plasma exposure. However, the decrease in sheet resistance saturates to 280 OMEGA / sq in 30 seconds, and no further decrease in sheet resistance was observed.

However, in the case of Example 1, the lowest sheet resistance value of 240 OMEGA / sq was obtained, which is related to the strong C-Cl bond formed on the surface of the graphene, even if pre-doped graphene is transported onto the substrate Since the pre-doped chlorine remained on the surface of the graphene, a low sheet resistance value was obtained.

FIG. 5 also shows the sheet resistance values of the single-layer graphenes and the graphenes of the first and second embodiments, and it can be seen that the graphene of Example 2 exhibits a very low sheet resistance value of 100? / Sq.

Experimental Example 3: Raman analysis

In order to confirm the effect of less damaging chlorine doping according to the method of the present invention, Raman analysis was performed.

FIG. 6 (a) shows the doped pristine, the pre-doped single-layer pre-doping prepared in step (1) of Example 1, and the double doped single layer doped graphene of Example 1 6 (b) and 6 (c) are enlarged spectra of the G peak and the 2D peak in Fig. 6 (a), respectively.

In the Raman spectroscopy, when the sp ² -bonded carbon network of graphene is damaged by active ions and electrons in the plasma, a disorder-induced D band peak characteristic located near 1350 cm ^-1 is emitted and 2670 The 2D band peak intensity near cm ^-1 decreases, and the G band peak near 1590 cm ^-1 becomes broad.

As shown in Fig. 6 (a), in Example 1 in which the chlorine plasma treatment was performed with the double mesh assembly, no emission of graphene D peak intensity was observed after 90 seconds, and in the sp ² network of graphene during chlorine doping, No appreciable disturbances were observed and no further changes were observed in the G and 2D peaks.

However, Figure 6 (b) and 6 (c), landscape, as shown in - after (pre-doped single-layer graphene), G, and each bit blue direction 2D peak location to 3cm and 4cm ^-1 ^-1 doped And further shifted to ¹ cm ^-1 and 3 cm ^{-1 in} the case of Example 1. Movement of the G and 2D peaks in the blue direction is associated with p-type hole doping by C-Cl bonds in graphene.

Thus, since the normal doping and the pre-doped single-layer graphene generate hole doping on the graphene surface without damaging the graphene network, as shown in Fig. 3, the pre-doped single-layer graphene phase Example 1, in which graphene was laminated and doped again, exhibited the lowest sheet resistance values without damaging the graphene network.

Experimental Example 4: C- Cl Bond analysis

The sheet resistance of graphene is almost always related to the C-Cl bond percent of graphene, regardless of doping time or doping type.

Thus, the doping of the carbon in bilayer graphene of undoped pristine, pre-doped monolayer pre-doping, bilayer graphene of normal doping and Example 1 (combined doping) The degree of the C-Cl bonding state was examined using XPS, and the results are shown in FIG.

As shown in Fig. 7, in the undoped graphene only the CC bond associated with the sp ² bond was observed. However, after chlorine doping, the peak associated with the C-Cl bond was observed at 286.2 eV and CO _x binding, which was also assumed to be contaminated by the PMMA residue, was also observed. The percentages of CC, C-Cl, and CO _x bonds at XPS C 1s peak intensities were determined by deconvolution of XPS C 1s peaks, and the results are shown in Table 1.

In the case of Comparative Example 1 in Table 1, the bonding percentage of C-Cl was 43.11%, while the percentage of C-Cl bonding of pre-doped single-layer graphene was 15.63%.

In the case of Comparative Example 1, the defect sites in the graphene were already bonded to contaminants such as oxygen during the graphene transfer process to form strong CO bonds, and during the chlorine doping, only weak C- Cl bonds.

On the other hand, Example 1 showed a higher C-Cl bond percent of 47.22% and a lower CO _x percentage.

Experimental Example 5: Grapina Elemental bond structure analysis

Figure 8 shows the elemental bonding structure for undoped graphene, pre-doped single-layer graphene, and Comparative Example 1 and double layer graphene of Example 1, wherein the CVD graphene grown on the copper foil is dislocated ), And major defects such as grain boundaries. During the doping, the defective graphene is exposed to the chlorine plasma, and the chlorine is intimately bound to the defect through a strong C-Cl bond, since the carbon at the defect site does not tightly bond to the carbon in the sp ² bond. And these C-Cl bonds still remain after the transfer process. Therefore, an increase in the defect (increase in the D peak intensity in Raman spectroscopy) is not observed because the existing defect is combined with the chlorine.

In the case of undoped graphene, these defect sites are exposed to contaminants during the transfer process of the graphene. Thus, these sites bind oxygen, hydrogen, and the like. Therefore, in the case of Comparative Example 1, during the exposure of the chlorine plasma, the chlorine is adsorbed on the surface of the carbon network such as weak C-Cl bonds (such as ionic bonds). During the subsequent wet transfer process, these C-Cl bonds are easily removed due to the weak bonding of carbon-chlorine.

However, in the case of Example 1, in addition to the formation of strong C-Cl bonds on the defect sites during pre-doping, weak C-Cl bonds are formed on the graphene surface during further doping, Higher C-Cl bond percentages were obtained.

Experimental Example 6: Thermal Stability Analysis

9 is a graph showing the results of annealing for 100 hours in order to measure the thermal stability of the graphene of Comparative Example 1 and the graphene of Example 1. Fig.

In the case of the graphene of Comparative Example 1 in which the pre-doping was not performed, the sheet resistance was increased and the result was not thermally stable. However, the graphene of Example 1 was kept at a low sheet resistance even after annealing at 230 DEG C for 100 hours It can be seen that it is thermally stable.

Experimental Example 7: Light transmittance analysis

In general, the optical transmittance of undoped graphene is reduced by 2.3 to 2.5% over the polyethylene terephthalate film. 10 shows that the pre-doped single-layer graphene and the graphenes of Examples 1 and 2 were excellent in light transmittance due to a very small decrease in light transmittance compared to the polyethylene terephthalate film even though chlorine doping was performed .

As can be seen from the above experimental results, Examples 1 and 2 according to the present invention have excellent sheet resistance, light transmittance and thermal stability characteristics as compared with Comparative Example 1. [

Therefore, the multi-layer graphene produced by the method of manufacturing graphene using pre-doping according to the present invention can be applied to a flexible touch screen, a flexible organic light emitting diode display, a smart window, an electronic paper, a photodetector, It can be used for pin electrodes.

Claims

A method for preparing graphene using pre-doping comprising the steps of:
(1) preparing graphene;
(2) chlorine pre-doping graphene;
(3) transferring the pre-doped graphene onto the substrate;
(4) moving additional graphene on the pre-doped graphene;
(5) annealing the result of step (4); And
(6) chlorine doping the further annealed graphene.

The method according to claim 1,
Further comprising repeating the steps (4) to (6) one or more times.

The method according to claim 1,
Wherein the step (1) is performed by synthesizing graphene on a metal.

The method of claim 3,
Wherein the graphene is synthesized on the metal by reacting and reacting the metal with a reaction gas and heat containing a carbon source.

5. The method of claim 4,
Wherein the synthesis of the graphene is carried out by inductively coupled plasma chemical vapor deposition, low pressure chemical vapor deposition, or atmospheric pressure chemical vapor deposition.

The method of claim 3,
The metal may be at least one selected from the group consisting of Au, Ag, Al, Pt, Mn, Fe, Ni, Co, Ti, Pd). &Lt; RTI ID = 0.0 > 8. < / RTI >

The method of claim 3,
Further comprising the step of removing the metal before the step (3).

The method according to claim 1,
In the step (2), chlorine pre-doping is performed by chlorine plasma treatment.

9. The method of claim 8,
Wherein the chlorine plasma treatment is performed by doping chlorine on graphene by injecting chlorine gas.

The method according to claim 1,
The method of claim 1, further comprising, after step (2), coating the polymer on the chlorine pre-doped graphene.

11. The method of claim 10,
Wherein the polymer material is at least one selected from polymethylmethacrylate, poly (dimethylsiloxane) (PDMS), poly (bisphenol A carbonate) (PC) and polystyrene (PS) Method of manufacturing graphene.

11. The method of claim 10,
The method of any preceding claim, further comprising removing the polymer prior to step (4).

The method according to claim 1,
In the step (3), the substrate is at least one selected from the group consisting of glass, polyethylene terephthalate, quartz, and SiO ₂ / Si wafers.

The method according to claim 1,
Wherein the additional graphene is formed by coating a polymer on a graphene attached to a separate substrate in the step (4).

15. The method of claim 14,
Further comprising, after the step (4), removing the polymer coated on the further graphene.

The method according to claim 1,
Wherein the annealing process is performed at 200 to 500 DEG C for 1 to 10 hours in the step (5).

17. A multi-layer graphene produced by the process for producing graphene according to any one of claims 1 to 16.