WO2014189271A1

WO2014189271A1 - Large-surface-area single-crystal monolayer graphene and production method therefor

Info

Publication number: WO2014189271A1
Application number: PCT/KR2014/004517
Authority: WO
Inventors: 박호범; 김한수; 윤희욱; 박선미; 이민용
Original assignee: 한양대학교 산학협력단
Priority date: 2013-05-21
Filing date: 2014-05-21
Publication date: 2014-11-27

Abstract

The present invention relates to: large-surface-area single-crystal monolayer graphene in which a graphene layer is formed on a single-crystal metal catalyst layer oriented only in the (111) crystal plane, on a substrate or without a substrate; and a method for producing large-surface-area single-crystal monolayer graphene oriented only in the (111) crystal plane, by means of a heat treatment of a metal precursor and chemical vapour deposition. According to the present invention, a single-crystal metal catalyst layer oriented only in the (111) crystal plane can be formed, on a substrate or even without a substrate, in various modes of foil, flat plate, block or tube, and, by producing large-surface-area single-crystal monolayer graphene in which a graphene layer is formed on the catalyst layer, it is possible to commercialise high-quality large-surface-area graphene thin films by means of volume production, and it is possible to use the invention as a transparent electrode material and a material for display elements, semiconductor elements, separating films, fuel cells, solar cells or various types of sensor.

Description

Large area single crystal single film graphene and its manufacturing method

The present invention relates to a large area single crystal single film graphene and a method for manufacturing the same, and more particularly, to a large area single crystal single crystal having a graphene layer formed on a single crystal metal catalyst layer oriented only on a (111) crystal plane without a substrate or without a substrate. The present invention relates to a film graphene and a method for producing a single-crystal single film graphene having a large area oriented only to the (111) crystal plane through heat treatment and chemical vapor deposition of a metal precursor.

Graphene is a two-dimensional structure of one atom thick in which carbon atoms are each connected by sp ² bonds, and benzene-shaped hexagonal carbon rings form a honeycomb crystal structure. Such graphene is very transparent and exhibits high transmittance with respect to visible light, and has excellent mechanical properties and excellent conductivity, and thus has been spotlighted as a transparent electrode material, a semiconductor device, a separator, or various sensor materials.

Current methods for preparing graphene films include mechanical exfoliation of graphite, chemical exfoliation by oxidation-reduction reaction of graphene, epitaxial growth on silicon carbide substrates, chemical vapor deposition (CVD) on transition metal catalyst layers. ). Among these, CVD method is a CVD method that can lead to commercialization by producing large-area graphene at low cost, but in general, when graphene film is manufactured by CVD method, graphene is deposited on a polycrystalline transition metal catalyst layer. Because of the deposition, it is known that it is impossible for the growing graphene to become single-crystal over a large area.

Further, in order to obtain a large area of single crystal graphene, a single crystal transition metal catalyst layer is formed on a single crystal substrate such as sapphire or magnesium oxide by thermal evaporation, electron beam evaporation or sputtering, and the graphene is deposited on the catalyst layer by CVD. There is a known technique for producing a single crystal graphene by the use, but there is a disadvantage that an expensive single crystal substrate such as sapphire or magnesium oxide must be used in forming the single crystal transition metal catalyst layer, thereby producing a large area of graphene There is a problem in that it is difficult to commercialize because it is economical (Patent Document 1).

In addition, there is an example of finally manufacturing a single-layer graphene, including forming a transition metal catalyst layer such as copper on the substrate and crystallizing the transition metal catalyst layer by heat treatment under a condition of 800 to 1,000 ° C. and 1 to 760 torr. This example also inevitably requires a substrate, and furthermore, since the transition metal catalyst layer crystallized according to the heat treatment does not have a single crystal structure, it is difficult to commercialize because it does not grow to a high quality large area single crystal single film graphene finally (Patent Document 2).

Therefore, in order to uniformly deposit graphene on a metal catalyst layer such as copper by using a CVD method without using an expensive single crystal substrate, process variables related to injection rate and injection rate of hydrocarbon gas precursor, hydrogen or argon, etc. By controlling, 95-97% of single-layer graphene is produced, but the single-layer graphene contains about 3 to 5% of bilayers, triple layers, or more multilayers. As a result, even in the case of 95-97% single layer graphene, grains and grains meet and migrate to form a large grain single crystal, but do not grow into large crystals, but have multiple orientations with grain boundaries. To form a layer.

Therefore, recently, a research result of producing single crystal single-layer graphene, which reaches almost 100% by growing the crystal nuclei on the copper catalyst layer by controlling the process variables by the CVD method without using an expensive single crystal substrate, is known. There is a bar. However, the hexagonal graphene domainrs manufactured here have an edge-to-edge distance of up to 2.3 mm and a surface area of up to 4.5 mm ^{2, which} is about 20 times higher than those reported previously. It is reported as large, but in practice it is formed on top of a copper foil layer measuring at most 1 cm x 1 cm, so the area is still very small for single crystal monolayer graphene for commercialization. Non-Patent Document 1).

In addition, a graphitization catalyst such as a commercially available copper foil may be pre-heated at 500 to 3,000 ° C. for 10 minutes to 24 hours, and chemically polished to prepare a single layer graphene. Although it is not possible to have a single crystal structure, in the case of the experimental example using a copper foil having a size of about 1 cm x 1 cm as the graphitization catalyst, single film graphene can be prepared, but it has a single crystal structure that crystallizes high quality. There is a problem that single film graphene cannot be manufactured in a large area (Patent Document 3).

Patent Document 1. Korean Patent Publication No. 10-2013-0020351

Patent Document 2. Korean Registered Patent No. 10-1132706

Patent Document 3. Korean Patent Publication No. 10-2013-0014182

[Non-Patent Document 1] Zheng Yan et al., ACS Nano 2012, 6 (10), 9110-9117

The present invention has been made in view of the above problems, and an object of the present invention is to form a single crystal metal catalyst layer oriented only on the (111) crystal plane on or without a substrate, and a large area in which a graphene layer is formed on the catalyst layer. It is to provide a method for producing a single-crystal single film graphene of a large area of the single crystal graphene oriented only to the (111) crystal surface through the heat treatment and chemical vapor deposition of the metal catalyst layer.

The present invention for achieving the above object is a single crystal metal catalyst layer oriented only on the (111) crystal plane on or without a substrate; And a graphene layer formed on the single crystal metal catalyst layer.

The substrate is characterized in that the single crystal substrate or non-monocrystalline substrate.

The substrate may be a silicon substrate, a metal oxide substrate, or a ceramic substrate.

The substrate is silicon (Si), silicon dioxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), zinc oxide (ZnO), zirconium dioxide (ZrO ₂ ), nickel oxide (NiO), hafnium oxide (HfO ₂ ), oxidizing agent Cobalt (CoO), cupric oxide (CuO), ferric oxide (FeO), magnesium oxide (MgO), alpha-aluminum oxide (a-Al ₂ O ₃ ), aluminum oxide (Al ₂ O ₃ ), strontium titanate (SrTiO ₃ ), lanthanum aluminate (LaAlO ₃ ), titanium dioxide (TiO ₂ ), tantalum dioxide (TaO ₂ ), niobium dioxide (NbO ₂ ), and boron nitride (BN) It is done.

The single crystal metal catalyst layer is copper (Cu), nickel (Ni), cobalt (Co), iron (Fe), ruthenium (Ru), platinum (Pt), palladium (Pd), gold (Au), silver (Ag), Aluminum (Al), Chromium (Cr), Magnesium (Mg), Manganese (Mn), Molybdenum (Mo), Rhodium (Rh), Silicon (Si), Tantalum (Ta), Titanium (Ti), Tungsten (W) ), Uranium (U), vanadium (V), iridium (Ir), and zirconium (Zr) is characterized in any one selected from the group consisting of.

The single crystal metal catalyst layer is characterized in that the shape of the foil, plate, block or tube.

In addition, the present invention comprises the steps of: i) preparing a polycrystalline metal precursor having a variety of crystal plane orientation without the crystal plane is biased in either direction;

ii) forming a single crystal metal catalyst layer oriented only to the (111) crystal plane by heat-treating the metal precursor of step i) and simultaneously chemical vapor deposition; And

iii) forming a graphene layer on the single crystal metal catalyst layer of step ii).

The metal precursor of step i) is copper (Cu), nickel (Ni), cobalt (Co), iron (Fe), ruthenium (Ru), platinum (Pt), palladium (Pd), gold (Au), silver ( Ag), aluminum (Al), chromium (Cr), magnesium (Mg), manganese (Mn), molybdenum (Mo), rhodium (Rh), silicon (Si), tantalum (Ta), titanium (Ti), It is characterized in that any one selected from the group consisting of tungsten (W), uranium (U), vanadium (V), iridium (Ir), and zirconium (Zr).

The metal precursor of step i) is characterized in that the shape of the foil, plate, block or tubular.

The metal precursor of step i) is characterized in that the commercialized copper foil.

The commercialized copper foil is characterized in that the thickness ranges from 5 μm to 18 μm.

Heat treatment of step ii) is characterized in that performed for 1 to 5 hours at 900 ~ 1,200 ℃, 1 torr ~ 760 torr in a hydrogen or mixed gas atmosphere of hydrogen and argon.

The hydrogen, or a mixed gas atmosphere of hydrogen and argon is characterized in that the injection of hydrogen 10 ~ 100 sccm, or hydrogen 10 ~ 100 sccm / argon 10 ~ 100 sccm.

Chemical vapor deposition of step ii) is carried out for 10 minutes to 3 hours at 900 ~ 1,200 ℃, 0.1 torr ~ 760 torr in a mixed gas atmosphere of hydrogen and carbon-containing gas.

The mixed gas atmosphere of the hydrogen and carbon-containing gas is characterized in that the injection of hydrogen 1 ~ 100 sccm / carbon-containing gas 10 ~ 100 sccm.

The carbon-containing gas is characterized in that any one selected from the group consisting of hydrocarbon gas, gaseous hydrocarbon compound, gaseous alcohol having 1 to 6 carbon atoms, carbon monoxide, and mixtures thereof.

The hydrocarbon gas is characterized in that any one selected from the group consisting of methane, ethane, propane, butane, ethylene, propylene, butylene, acetylene, butadiene, and mixtures thereof.

The gaseous hydrocarbon compound is characterized in that any one selected from the group consisting of pentane, hexane, cyclohexane, benzene, toluene, xylene, and mixtures thereof.

After the step iii), characterized in that it further comprises an artificial cooling step.

The cooling step is characterized in that it is carried out slowly at a cooling rate of 10 ~ 50 ℃ / min.

The cooling step is characterized in that it is carried out while injecting hydrogen at 10 ~ 1,000 sccm.

In addition, the present invention provides a transparent electrode including the large area single crystal graphene graphene.

In addition, the present invention provides a display device including the large area single crystal single layer graphene.

In addition, the present invention provides a semiconductor device including the large area single crystal single film graphene.

In addition, the present invention provides a separation membrane comprising the large area single crystal graphene graphene.

In addition, the present invention provides a fuel cell comprising the large area single crystal single film graphene.

In addition, the present invention provides a solar cell including the large area single crystal single film graphene.

In addition, the present invention provides a sensor comprising the large area single crystal single film graphene.

According to the present invention, it is possible to form a single crystal metal catalyst layer oriented on the (111) crystal plane only on a substrate or without a substrate in various shapes such as foil, flat plate, block, or tubular shape, and the graphene layer is formed on the catalyst layer. It is possible to commercialize high-quality large-area graphene thin film by mass production by manufacturing single crystal single film graphene, which can be applied to transparent electrode material, display device, semiconductor device, separator, fuel cell, solar cell or various sensor materials. It can be applied.

1 (a) and (b) show a graphene layer chemically vapor deposited on a copper 100 single crystal grown on a conventional single crystal 100 sapphire substrate, and a copper grown directly on a single crystal (111) magnesium oxide substrate, respectively. 111) A graph showing the chemical vapor deposition on the single crystal.

2 is a scanning electron microscope (SEM) image of a commercialized copper foil according to Example 1 of the present invention.

3 is an X-ray diffraction (XRD) pattern of a commercialized copper foil according to Example 1 of the present invention.

4 is a scanning electron microscope (SEM) image when graphene is formed on a commercialized copper foil catalyst layer according to Example 1 of the present invention.

5 is an X-ray diffraction (XRD) pattern when graphene is formed on a commercialized copper foil catalyst layer according to Example 1 of the present invention.

6 is an electron backscattering diffraction (EBSD) pattern of a copper catalyst layer formed according to Example 1 of the present invention.

7 is a Raman Spectrum (Raman Spectrum) of the graphene layer formed according to Example 1 of the present invention.

8 is a Raman map of the graphene layer formed according to Example 1 of the present invention.

9 is a scanning electron microscope (SEM) image when graphene is formed on a commercially available copper foil catalyst layer according to Comparative Example 1 of the present invention.

10 is a scanning electron microscope (SEM) image when graphene is formed on a copper foil catalyst layer commercialized according to Comparative Example 2 of the present invention.

11 is an electron backscattering diffraction (EBSD) pattern of a copper catalyst layer formed according to Comparative Example 2 of the present invention.

12 is an X-ray diffraction (XRD) pattern when graphene is formed on a copper foil catalyst layer commercialized according to Comparative Example 2 of the present invention.

FIG. 13 is a scanning electron microscope (SEM) image of graphene formed on a copper foil catalyst layer commercialized according to Comparative Example 3 of the present invention. FIG.

FIG. 14 is a graph showing sheet resistance values of single crystal single layer graphene prepared from Example 1 of the present invention and sheet resistance values of polycrystalline single layer graphene published in the related art.

FIG. 15 is a graph showing values of carrier mobility of single crystal single layer graphene prepared from Example 1 of the present invention and values of current carrier mobility of polycrystalline single layer graphene published in the related art. .

FIG. 16 is a graph showing values of the transmittance of single crystal single layer graphene prepared from Example 1 of the present invention and values of the polycrystalline single layer graphene published in the related art.

Hereinafter, a single crystal metal catalyst layer oriented only on the (111) crystal plane on or without a substrate according to the present invention; And a graphene layer formed on the single crystal metal catalyst layer; a large-area single crystal single film graphene including a method and a manufacturing method thereof will be described in detail with reference to the accompanying drawings.

In general, when a metal catalyst layer is formed on an amorphous substrate such as a silicon oxide film (SiO ₂ ), the metal catalyst layer has a polycrystalline structure and is formed on a metal foil or sheet such as copper, nickel, or cobalt without a substrate. Even when the graphene is formed directly on the metal foil or the sheet itself is polycrystalline by the conventional chemical vapor deposition method, the formed graphene also has domains and domain boundaries, resulting in poor quality and difficult to realize large area graphene. .

As shown in FIG. 1 (a), the graphene layer formed by the chemical vapor deposition method on the copper 100 single crystal grown directly on the conventional single crystal 100 sapphire substrate has two (0, 30 degree) directions, As shown in FIG. 1 (b), the graphene layer formed by the chemical vapor deposition method on the copper (111) single crystal grown directly on the conventional single crystal (111) magnesium oxide substrate produces a single surface without grain boundary, that is, a single crystal single film. can do. However, in order to directly grow a copper thin film having such a (111) crystal plane, an expensive single crystal (111) magnesium oxide or sapphire substrate was necessary.

However, when the graphene hexagonal structure layer on the hexagonal (111) plane is formed on the layer due to the chemical reaction due to its physical properties, the graphene meets and migrates without defects even if each nucleus grows in any direction. ), It is possible to form a single crystal single film without grain boundaries.

Thus, in the present invention, a special heat treatment of a polycrystalline metal foil having various crystal surface orientations without any bias in any direction and simultaneously performed without expensive substrates for single crystal growth having a copper (111) crystal surface unlike conventional By forming an in-situ chemical vapor deposition, a single crystal metal foil layer oriented only to the (111) crystal plane and a graphene layer formed on the single crystal metal foil layer could realize a large area of single crystal single film graphene. .

That is, the present invention provides a single crystal metal catalyst layer oriented only on the (111) crystal plane on or without a substrate; And a graphene layer formed on the single crystal metal catalyst layer.

In the present invention, it is one of the technical features that the single crystal metal catalyst layer can be formed without an expensive single crystal substrate such as magnesium oxide or sapphire, but, of course, the conventional single crystal substrate can be used to form the single crystal metal catalyst layer. Non single-crystalline substrates may also be used.

In the case of using a single crystal substrate or a non-single crystal substrate, the substrate may be a silicon substrate, a metal oxide substrate, or a ceramic substrate, and examples thereof include silicon (Si), silicon dioxide (SiO ₂ ), and silicon nitride (Si ₃ N _4). ), Zinc oxide (ZnO), zirconium dioxide (ZrO ₂ ), nickel oxide (NiO), hafnium oxide (HfO ₂ ), cobalt oxide (CoO), cuprous oxide (CuO), ferric oxide (FeO), magnesium oxide (MgO ), Alpha-aluminum oxide (a-Al ₂ O ₃ ), aluminum oxide (Al ₂ O ₃ ), strontium titanate (SrTiO ₃ ), lanthanum aluminate (LaAlO ₃ ), titanium dioxide (TiO ₂ ), dioxide Any one selected from the group consisting of tantalum (TaO ₂ ), niobium dioxide (NbO ₂ ), and boron nitride (BN) may be used, but is not limited thereto.

In addition, the single crystal metal catalyst layer oriented only to the (111) crystal plane of the present invention includes copper (Cu), nickel (Ni), cobalt (Co), iron (Fe), ruthenium (Ru), platinum (Pt), and palladium (Pd). ), Gold (Au), silver (Ag), aluminum (Al), chromium (Cr), magnesium (Mg), manganese (Mn), molybdenum (Mo), rhodium (Rh), silicon (Si), tantalum (Ta), titanium (Ti), tungsten (W), uranium (U), vanadium (V), iridium (Ir), and zirconium (Zr), any one selected from the group consisting of, copper (Cu) The catalyst layer is more preferred, but is not limited thereto.

In addition, the single crystal metal catalyst layer oriented only to the (111) crystal plane of the present invention may be formed regardless of its shape, and may be in any form including a foil, a flat plate, a block, or a tubular shape, but a foil shape is preferable. Do.

A graphene layer is formed on the single crystal metal catalyst layer oriented only to the (111) crystal plane to obtain a large area single crystal graphene graphene according to the present invention. A large area single crystal graphene graphene is prepared by the following manufacturing method. It can be manufactured.

That is, in the present invention, i) preparing a polycrystalline metal precursor having a variety of crystal surface orientation without the crystal plane is biased in either direction;

ii) thermally treating the metal precursor of step i) and simultaneously forming a single crystal metal catalyst layer oriented only to the (111) crystal plane through chemical vapor deposition; And

First, in the present invention, since graphene is deposited on a polycrystalline transition metal catalyst layer when a graphene film is manufactured by a conventional chemical vapor deposition method, it is known that it is impossible for the growing graphene to become a single crystal over a large area. In order to overcome the limitation, as a precursor for forming a single crystal metal catalyst layer, a polycrystalline metal precursor having various crystal surface orientations is prepared without shifting the crystal plane in one direction as in the prior art.

Examples of the polycrystalline metal precursors having various crystal plane orientations include copper (Cu), nickel (Ni), cobalt (Co), iron (Fe), ruthenium (Ru), platinum (Pt), palladium (Pd), and gold (Au). , Silver (Ag), aluminum (Al), chromium (Cr), magnesium (Mg), manganese (Mn), molybdenum (Mo), rhodium (Rh), silicon (Si), tantalum (Ta), titanium ( Any one selected from the group consisting of Ti), tungsten (W), uranium (U), vanadium (V), iridium (Ir), and zirconium (Zr) can be used, and also in the form of the metal precursor. It may be of any type, including flat, block, or tubular, but is preferably in the form of a foil for the formation of a homogeneous single crystal metal catalyst layer by heat treatment, and particularly preferably a commercially available copper foil, which is readily available and inexpensive. Can be used.

In the present invention, as the precursor for the heat treatment of step ii), it is important that the crystal plane of the polycrystalline metal precursor has various crystal plane orientations without being biased in one direction, and in fact, the (100) crystal plane has a predominantly dominant orientation ( 111) Since the polycrystalline metal precursors having a predominant orientation in a crystal plane direction other than the crystal plane do not have various crystal plane orientations, the crystal plane direction does not change even by heat treatment or cannot have a single crystal structure oriented only in the (111) crystal plane. do.

In the present invention, in addition to the crystallinity and crystal surface orientation of the metal precursor, the thickness is another important variable as an important factor capable of forming a single crystal metal catalyst layer oriented only on the (111) crystal plane. In particular, when the metal precursor is in the form of a foil, since it affects the solid solubility of carbon in the process of graphene formation by recrystallization and chemical vapor deposition after heat treatment according to the thickness, according to the present invention It is preferable that the thickness of a metal precursor is 5 micrometers-18 micrometers. When the thickness of the metal precursor is less than 5 μm, it is too thin to perform a smooth heat treatment and chemical vapor deposition process, so recrystallization cannot be expected, and when it exceeds 18 μm, only the (111) crystal plane is oriented even if heat treatment is performed under the same conditions. A single crystal metal catalyst layer can never be obtained, only a metal catalyst layer having various crystal plane directions as a metal precursor or having a crystalline structure in which the (100) crystal plane is dominant is obtained, and also formed by chemical vapor deposition carried out simultaneously with the heat treatment. In the graphene layer, a large number of grain boundaries exist, such that a single layer is not obtained.

Next, in step ii), the crystal plane prepared in step i) is crystallized by heat treatment and chemical vapor deposition at the same time without crystallization in either direction and crystallized by chemical vapor deposition. A single crystal metal catalyst layer is formed.

The heat treatment of step ii) is performed in a hydrogen atmosphere to prevent oxidation of the metal catalyst layer, or in a mixed gas atmosphere of hydrogen and argon for 1 to 5 hours at 900 ~ 1,200 ℃, 1 torr ~ 760 torr, When hydrogen, or a mixed gas atmosphere of hydrogen and argon is preferably heat treatment while injecting hydrogen 10 ~ 100 sccm, or hydrogen 10 ~ 100 sccm / argon 10 ~ 100 sccm. The heat treatment process is a variable temperature, pressure, time and hydrogen, or the rate of injection of hydrogen and argon gas, especially the pressure conditions are very important, out of the above range, single crystal metal oriented only to the (111) crystal plane A catalyst layer is not formed, and thus a high quality graphene thin film is difficult to obtain. Therefore, in the present invention, by controlling the process parameters for the heat treatment of step ii) within the above range to crystallize the metal precursor to form a single crystal metal catalyst layer oriented only to the (111) crystal plane, and then in step iii) high quality single crystal A single layer graphene layer can be formed.

As a result, the present invention is fundamentally different from the technical idea of forming a single crystalline metal thin film on a substrate using a conventional single crystal substrate, or forming a polycrystalline metal catalyst layer by heat treating a metal precursor even when the substrate is not used. In fact, compared to conventional graphene forming using a copper foil precursor of 1 cm x 1 cm at most, the present invention is heat-treated and chemical vapor phase of the metal precursor having any size as it is, regardless of the size of the metal precursor Since it is possible to produce single crystal single film graphene having a large area (arbitrary area) by evaporation, commercialization by mass production can be realized.

Finally, the chemical vapor deposition of step ii) is carried out for 10 minutes to 3 hours at 900 ~ 1,200 ℃, 0.1 torr ~ 760 torr in a mixed gas atmosphere of hydrogen and carbon containing gas, wherein the hydrogen and carbon containing gas The mixed gas atmosphere is preferably injected at 1-100 sccm of hydrogen / 10-100 sccm of carbon-containing gas. The carbon-containing gas may be any one selected from the group consisting of a hydrocarbon gas, a gaseous hydrocarbon compound, a gaseous alcohol having 1 to 6 carbon atoms, carbon monoxide, and a mixture thereof, and in particular, a hydrocarbon gas may be preferably used.

As the hydrocarbon gas, any one selected from the group consisting of methane, ethane, propane, butane, ethylene, propylene, butylene, acetylene, butadiene, and mixtures thereof, and using methane gas that is easy to handle is used. More preferred. The gaseous hydrocarbon compound may be any one selected from the group consisting of pentane, hexane, cyclohexane, benzene, toluene, xylene, and mixtures thereof, but is not limited thereto.

On the other hand, in the present invention, when the process of step ii) is finished, it is possible to obtain a single crystal single layer graphene having a large area as a target in step iii), but may further include an artificial cooling step after the step iii), if necessary. There is, the cooling step is preferably carried out slowly at a cooling rate of 10 ~ 50 ℃ / min. In particular, if the rapid cooling over the range of the cooling rate is necessary to pay attention because the graphene is uniformly grown and can be cracked in the process of uniformly arranged. In addition, in order to prevent the oxidation atmosphere that may occur in the cooling step may be cooled while injecting hydrogen at 10 ~ 1,000 sccm.

In addition, according to the present invention, it is possible to provide a transparent electrode, a display device, a semiconductor device, a separator, a fuel cell, a solar cell or various sensors including the large-area single crystal single film graphene produced in the present invention.

Hereinafter, specific embodiments will be described in detail.

(실시예 1)(Example 1)

As a metal precursor, a copper foil (HOHSEN, 99.9%, Japan) having a thickness of 18 μm and a length of 10 cm x 10 cm was placed in a chamber, and heat-treated while injecting hydrogen at 100 sccm for 2 hours at 1,005 ° C and 500 torr. The copper catalyst layer was formed, and at the same time, a graphene layer was formed on the copper catalyst layer by performing a chemical vapor deposition (CVD) process while injecting hydrogen / methane at a ratio of 5 sccm / 20 sccm for 60 minutes at 1,005 ° C. and 0.5 torr.

Table 1 below shows the heat treatment and CVD process parameters according to Examples 1-3 and Comparative Examples 1-3.

Table 1

Example	Thickness (μm)	Temperature ¹⁾ (℃)	Pressure ¹⁾ (torr)	Atmosphere (Hydrogen) ¹⁾ Time	Temperature ²⁾ (℃)	Pressure ²⁾ (torr)	Atmosphere (Hydrogen / Methane) ²⁾ Time
Example 1	18	1,005	500	100 sccm2 hours	1,005	0.5	5/20 sccm60 minutes
Example 2	18	1,005	500	50 sccm2 hours	1,005	0.5	5/20 sccm60 minutes
Example 3	18	1,005	500	100 sccm2 hours	1,020	500	5/20 sccm30 minutes
Comparative Example 1	18	None	None	None	1,005	0.5	5/20 sccm60 minutes
Comparative Example 2	18	1,005	0.5	20 sccm2 hours	1,005	0.5	5/20 sccm60 minutes
Comparative Example 3	75	1,005	500	100 sccm2 hours	1,005	0.5	5/20 sccm60 minutes

* Copper foil all measures 10 cm x 10 cm (width x length)

¹⁾ heat treatment

²⁾ CVD

2 shows a scanning electron microscope (SEM) image of a commercially available copper foil as a metal precursor according to Example 1 of the present invention. As shown in FIG. 2, it can be seen that grains and grain boundaries exist. And Figure 3 is to measure the X-ray diffraction pattern to determine the crystallinity of the commercialized copper foil, it was confirmed that the polycrystalline (polycrystalline) having a variety of crystal plane orientation.

FIG. 4 is a scanning electron microscope (SEM) image when graphene is formed after heat treatment and chemical vapor deposition (CVD) of the commercialized copper foil according to Example 1 of the present invention, and the copper catalyst layer has a grain boundary. From the X-ray diffraction pattern of FIG. 5, it was confirmed that a single crystal catalyst layer oriented only to the (111) crystal plane was formed due to recrystallization by heat treatment and chemical vapor deposition.

6 shows electron backscatter diffraction (EBSD) characteristics in order to further analyze the crystal plane orientation of the copper catalyst layer formed according to Example 1 of the present invention, and has no grain boundaries and defects in the entire area. It was confirmed that the single crystal catalyst layer oriented only on the (111) plane was formed.

In addition, Figure 7 shows the Raman spectrum of the graphene layer formed in accordance with Example 1 of the present invention, the G peak, which is a characteristic peak of graphene is found around 1580 cm ^-1 , in particular around 2700 cm ^-1 A strong and sharp 2D peak was found at, indicating that the graphene layer was formed as a monolayer. In addition, the D peak intensity near 1340 cm ⁻¹ found in conventional graphene was measured so weakly that it was unknown, and it was found that the graphene formed according to Example 1 of the present invention had almost no defects, and the G peak intensity The relative ratio of the D peak intensity to about was also measured about 0.22 to confirm that the crystallinity is very high.

8 shows a Raman map of the graphene layer formed according to Example 1 of the present invention, in which defects such as wrinkles, cracks, grain boundaries, etc. are not found when D1 is mapped. When the mapping of D2, the entire surface was measured only by the peak of D2, and it was found that the graphene was composed of only a single layer. The Raman mapping also confirmed the large-area single-crystal single-layer graphene prepared according to the present invention. It became.

In addition, compared with Example 1 of the present invention, Example 2, which differs only in the hydrogen injection rate as a heat treatment atmosphere, and Example 3, which changed the CVD process conditions, were able to obtain the same result as Example 1 of the present invention (not shown). city).

On the other hand, when the heat treatment of the copper foil according to Comparative Example 1 of the present invention as can be seen in Figure 9, even if the chemical vapor deposition under the same conditions as in Example 1, grains and grain boundaries exist as it is It was found that the single crystal monolayer graphene could not be obtained.

In addition, as shown in the scanning electron microscope (SEM) image of FIG. 10 and the EBSD image of FIG. 11, the heat treatment of the copper foil commercialized according to Comparative Example 2 of the present invention under relatively low pressure was carried out in Example 1 and Even though the CVD process is performed under the same conditions, it can be seen that the copper grains and grain boundaries are still present in the copper catalyst layer. Also, from the X-ray diffraction pattern of FIG. It was confirmed that it did not change even after performing.

In addition, as shown in FIG. 13, when the copper foil having a thickness of 75 m was used as the metal precursor as in Comparative Example 3, the copper catalyst layer was coated with copper grains even though the heat treatment and CVD processes were performed under the same conditions as in Examples 1 to 3. It can be seen that the grain boundaries exist as it is, but the heat treatment and CVD process for copper foils of various thicknesses, which are not described in Table 1 above, show that the single-crystal single film graphene has a thickness of more than 18 m. On the other hand, if the thickness was less than 5 m, it was too thin to perform a smooth heat treatment and CVD process.

In addition, sheet resistance, current carrier mobility, and transmittance were measured to confirm the electrical and optical properties of the single crystal single layer graphene prepared in the present invention. The results are shown in FIGS. 14-16 with the values published in the prior art.

FIG. 14 is a graph showing the measurement of sheet resistance of single crystal single-layer graphene prepared from Example 1 of the present invention using a 4-point probe according to ASTM D257. [ACS NANO, VOL 5, 6916 (2011)] is shown with the sheet resistance value of the polycrystalline single-layer graphene, the single crystal single-layer graphene prepared from Example 1 of the present invention has a sheet resistance value compared to the conventional polycrystalline single-layer graphene As a result of the significant reduction, it can be seen that the improvement effect is about 80%. This is because the electron mean free path is improved by decreasing the defect density such as grain boundary in the single crystal single film. Therefore, the single crystal single layer graphene manufactured in the present invention is expected to be applicable to a flexible OLED or a solar cell device as a display device of low power and high efficiency beyond the touch screen level.

In addition, Figure 15 is measured according to the conventional Hall effect measurement (carrier mobility) of the single crystal single-film graphene prepared from Example 1 of the present invention known Appl. Phys. Lett., 102, 163102 (2013) is shown with the current carrier mobility value of the polycrystalline single-layer graphene published in the present invention, the monocrystalline single-layer graphene prepared from Example 1 of the present invention is a conventional polycrystalline single-layer graphene As a result of the significant increase of the current carrier mobility compared to the fin, it can be seen that the improvement effect is about 300%. This is because the scattering rate of the charge carrier is improved by reducing the defect density such as grain boundary in the single crystal single film. Therefore, the single crystal single layer graphene manufactured in the present invention may be applied to low power rapid next generation semiconductor logic devices or next generation 10 nm or less ultra fine channel materials.

In addition, FIG. 16 shows the transmittances of the single crystal single layer graphene prepared from Example 1 of the present invention and the polycrystalline single layer graphene published in the publication [Nature Nanotechnology, Vol 5, August (2010)]. The monocrystalline single film graphene prepared from Example 1 of the present invention has an increase in the transmittance value of about 0.8% compared to the conventional polycrystalline single film graphene, which is the highest value ever published. This result is interpreted to be due to the improvement of scattering and refraction upon transmission of light by decreasing defect density such as grain boundary in the single crystal single film according to the present invention. Furthermore, in the general case, the transmittance is improved as the thickness decreases and the resistance is increased as the thickness increases, so that the transmittance and resistance have a trade-off relationship with respect to the thickness. It can be seen that the effect is shown.

Therefore, the single crystal single film graphene prepared from the embodiment of the present invention has a grain and grain boundary through heat treatment and chemical vapor deposition of the metal precursor without an expensive substrate, compared to the single layer graphene prepared by the comparative example or the conventional method. It is possible to obtain high quality single crystal single layer graphene which does not exist, and in particular, since the metal precursor is heat-treated and chemical vapor deposition as it is, irrespective of the size and shape of the metal precursor, the large area of the metal precursor intact is as large as it is. Has a surprising effect of producing single crystal single layer graphene.

Therefore, the large-area single crystal graphene graphene prepared according to the present invention is expected to be applicable to transparent electrodes, display devices, semiconductor devices, separators, fuel cells, solar cells or various sensors.

Claims

A single crystal metal catalyst layer oriented only on the (111) crystal plane on or without a substrate; And

Single-crystal graphene graphene having a large area comprising a; graphene layer formed on the single crystal metal catalyst layer.
The large-area single crystal single layer graphene of claim 1, wherein the substrate is a single crystal substrate or a non-monocrystalline substrate.
The large-area single crystal graphene of claim 1 or 2, wherein the substrate is a silicon substrate, a metal oxide substrate, or a ceramic substrate.
The substrate of claim 3, wherein the substrate is silicon (Si), silicon dioxide (SiO 2 ), silicon nitride (Si 3 N 4 ), zinc oxide (ZnO), zirconium dioxide (ZrO 2 ), nickel oxide (NiO), hafnium oxide. (HfO 2 ), cobalt oxide (CoO), cupric oxide (CuO), ferric oxide (FeO), magnesium oxide (MgO), alpha-aluminum oxide (a-Al 2 O 3 ), aluminum oxide (Al 2 O 3 ) , Strontium titanate (SrTiO 3 ), lanthanum aluminate (LaAlO 3 ), titanium dioxide (TiO 2 ), tantalum dioxide (TaO 2 ), niobium dioxide (NbO 2 ), and boron nitride (BN) Large-area single crystal single layer graphene, characterized in that any one selected.
The method of claim 1, wherein the single crystal metal catalyst layer is copper (Cu), nickel (Ni), cobalt (Co), iron (Fe), ruthenium (Ru), platinum (Pt), palladium (Pd), gold (Au) , Silver (Ag), aluminum (Al), chromium (Cr), magnesium (Mg), manganese (Mn), molybdenum (Mo), rhodium (Rh), silicon (Si), tantalum (Ta), titanium ( A large-area single crystal graphene graphene, characterized in that any one selected from the group consisting of Ti), tungsten (W), uranium (U), vanadium (V), iridium (Ir), and zirconium (Zr).
2. The large-area single crystal single film graphene of claim 1, wherein the single crystal metal catalyst layer is in the form of a foil, a plate, a block, or a tube.
i) preparing a polycrystalline metal precursor having a variety of crystal plane orientations without the crystal planes biased in either direction;

ii) thermally treating the metal precursor of step i) and simultaneously forming a single crystal metal catalyst layer oriented only to the (111) crystal plane through chemical vapor deposition; And

iii) forming a graphene layer on the single crystal metal catalyst layer of step ii).
The metal precursor of step i) is copper (Cu), nickel (Ni), cobalt (Co), iron (Fe), ruthenium (Ru), platinum (Pt), palladium (Pd), gold (Au), silver (Ag), aluminum (Al), chromium (Cr), magnesium (Mg), manganese (Mn), molybdenum (Mo), rhodium (Rh), silicon (Si), tantalum (Ta) , Single crystal single layer graphene, characterized in that any one selected from the group consisting of titanium (Ti), tungsten (W), uranium (U), vanadium (V), iridium (Ir), and zirconium (Zr) Method of manufacturing pins.
8. The method of claim 7, wherein the metal precursor of step i) is in the form of a foil, a plate, a block, or a tube.
10. The method of claim 7 or 9, wherein the metal precursor of step i) is a commercialized copper foil.
The method of claim 10, wherein the commercially available copper foil has a thickness in the range of 5 μm to 18 μm.
8. The large-area single crystal of claim 7, wherein the heat treatment in step ii) is performed at 900 to 1,200 ° C. and 1 torr to 760 torr in a mixed gas atmosphere of hydrogen or hydrogen and argon. Method of manufacturing single film graphene.
13. The large-area single crystal single layer graphene of claim 12, wherein the hydrogen or a mixed gas atmosphere of hydrogen and argon is injected at 10-100 sccm of hydrogen or 10-100 sccm of hydrogen / 10-100 sccm of argon. Method of manufacturing pins.
The method according to claim 7, wherein the chemical vapor deposition of step ii) is carried out for 10 minutes to 3 hours at 900 ~ 1,200 ℃, 0.1 torr ~ 760 torr in a mixed gas atmosphere of hydrogen and carbon-containing gas Method for producing single crystal single film graphene.
15. The method of claim 14, wherein the mixed gas atmosphere of hydrogen and carbon-containing gas is injected at 1-100 sccm of hydrogen / 10-100 sccm of carbon-containing gas.
The carbon-containing gas according to claim 14 or 15, wherein the carbon-containing gas is any one selected from the group consisting of hydrocarbon gas, gaseous hydrocarbon compound, gaseous alcohol having 1 to 6 carbon atoms, carbon monoxide, and mixtures thereof. Method for producing single crystal single film graphene.
17. The single crystal single crystal of claim 16, wherein the hydrocarbon gas is any one selected from the group consisting of methane, ethane, propane, butane, ethylene, propylene, butylene, acetylene, butadiene, and mixtures thereof. Method for preparing membrane graphene.
18. The method of claim 16, wherein the gaseous hydrocarbon compound is any one selected from the group consisting of pentane, hexane, cyclohexane, benzene, toluene, xylene, and mixtures thereof. Manufacturing method.
The method of claim 7, further comprising an artificial cooling step after the step iii).
20. The method of claim 19, wherein the cooling step is performed slowly at a cooling rate of 10 to 50 DEG C / min.
21. The method of claim 19 or 20, wherein the cooling step is performed while injecting hydrogen at 10 to 1,000 sccm.
A transparent electrode comprising the large-area single crystal single film graphene according to claim 1.
A display device comprising the large-area single crystal single film graphene according to claim 1.
A semiconductor device comprising the large-area single crystal single film graphene according to claim 1.
Separation membrane comprising a large area single crystal graphene graphene according to claim 1.
A fuel cell comprising the large-area single crystal single film graphene according to claim 1.
A solar cell comprising the large-area single crystal single film graphene according to claim 1.
A sensor comprising a large area single crystal graphene graphene according to claim 1.