KR20140003354A - Preparing method of graphene sheet, graphene laminate, preparing method of transformation-affordable graphene sheet, transformation-affordable graphene sheet and device using the same - Google Patents

Abstract

The application relates to a graphene sheet manufacturing method which includes a step of growing graphene on a graphene growth supporter including a metallic catalyst thin film for the growth of graphene by using a chemical vapor deposition method; a graphene laminate; a transformation-affordable graphene sheet manufacturing method; a transformation-affordable graphene sheet; and a device using the same. [Reference numerals] (AA) Injecting carbon gas; (BB) Cooling; (CC,FF,GG) Etching; (DD) Stamping; (EE) transforming a graphene layer on a target substrate; (HH) Floating the graphene layer

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a graphene sheet, a graphene laminate, a method of producing a graphene sheet, a water-soluble graphene sheet, TRANSFORMATION-AFFORDABLE GRAPHENE SHEET AND DEVICE USING THE SAME}

The present invention relates to a method for producing a graphene sheet on a thin film of a metal catalyst for graphene growth using a chemical vapor deposition method, a graphene laminate, a method for producing a strain water-soluble graphene sheet, a deformable water-soluble graphene sheet and a device using the same will be.

Graphene is a conductive material with a thickness of one layer of atoms, with the carbon atoms forming a honeycomb arrangement in a two-dimensional fashion. Graphite is piled up in three dimensions, carbon nanotubes rolled up in one dimension, and fullerene, which is a zero-dimensional structure, when it becomes a ball shape. Graphene is not only structurally and chemically stable, but it is also a very good conductor that is expected to move electrons 100 times faster than silicon and carry about 100 times more current than copper. These properties of graphene were experimentally confirmed by the discovery of a method for separating graphene from graphite in 2004, which has been enthusiasm for scientists around the world for many years.

Graphene has the advantage that it is very easy to process one-dimensional or two-dimensional nanopatterns made of carbon, which is a relatively light element. It is also possible to manufacture a wide range of functional devices such as sensors and memories. In 2008, it was selected as one of the 100 best future technologies selected by MIT. Recently, Korea Institute of Science and Technology Evaluation and Samsung Economic Research Institute also selected graphene-related technology as the top 10 technologies to change our lives within 10 years. Domestic research on graphene is still in its infancy, as small-scale national projects began last year, and is far behind the US, Japan, and Europe.

In spite of the excellent electrical / mechanical / chemical properties of graphene mentioned above, since the mass synthesis method has not been developed in the meantime, the research on practical applicable technology has been very limited. In the conventional mass synthesis method, graphite was mechanically pulverized and dispersed in a solution, followed by self-assembly to form a thin film. The advantage of being able to synthesize at a relatively low cost, however, is that the electrical and mechanical properties of the graphene pieces are not as expected due to the overlapping structure of the graphene pieces.

The global transparent electrode market is expected to grow to 20 trillion won within the next 10 years due to the rapidly growing demand for flat panel displays. Due to the nature of the display industry in Korea, the domestic demand for transparent electrodes has reached several hundred billion won each year, but it is largely dependent on imports due to lack of source technology. Indium Tin Oxide (ITO), which is a representative transparent electrode, has been widely used in displays, touch screens, solar cells, etc. Recently, due to the depletion of indium, the unit price has risen and urgent development of substitute materials has been required. In addition, due to the property of ITO which is easy to break, application has been greatly restricted to next generation electronic products which can be folded, warped or stretched. Graphene, on the other hand, was expected to have the advantage of being able to synthesize and pattern in a relatively simple manner while having excellent stretchability, flexibility and transparency. These graphene electrodes are expected to revolutionize the entire next-generation flexible electronic industry as well as import substitution if mass production technology can be established in the future.

However, there is still a growing need for development of graphene because of the development of graphene and the practical application of graphene application through it.

The present inventors have completed the present invention by variously developing a new manufacturing technique of a graphene sheet which obtains a graphene sheet by forming a graphene sheet by providing a carbon source on a thin film of a metal catalyst for graphene growth by chemical vapor deposition. These techniques can make large-area graphene sheets economically easy to manufacture with a large area.

The present invention relates to a method for producing a graphene sheet on a thin film of a metal catalyst for graphene growth using a chemical vapor deposition method, a graphene laminate, a method for producing a strain water-soluble graphene sheet, Or an opaque stretchable element.

Further, in the present invention, it is intended to produce a water-soluble graphene sheet by forming a wrinkle which imparts strain water-solubility to the graphene sheet during the manufacturing process of the graphene sheet. The deformable water-soluble graphene sheet may control strain water solubility or impart additional strain water solubility.

However, the problem to be solved by the present application is not limited to the above-mentioned problem, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

One aspect of the present invention is a process for producing a graphene sheet, comprising growing graphene on the support by providing a graphene growth support comprising a metal catalyst thin film for graphene growth, Of the present invention.

Another aspect of the present invention provides a graphene sheet comprising graphene grown by chemical vapor deposition on a graphene growth support comprising a metal catalyst thin film for graphene growth.

Another aspect of the present application is a graphene laminate comprising a graphene sheet transferred onto an elastic substrate, the graphene sheet having a chemical vapor phase on a graphene growth support comprising a metal catalyst thin film for graphene growth Wherein the graphene layer comprises graphene grown by vapor deposition.

According to another aspect of the present invention, graphene grown by chemical vapor deposition on a graphene growth support containing a metal catalyst thin film for graphene growth is immersed in an etching solution to separate the graphene from the support to form a substrate, And transferring the graft sheet onto a recording medium.

Another aspect of the present invention provides a device comprising a graphene sheet comprising graphene grown by chemical vapor deposition on a graphene growth support comprising a metal catalyst thin film for graphene growth.

Another aspect of the present application is a graphene laminate comprising a graphene sheet transferred onto an elastic substrate, the graphene sheet having a chemical vapor phase on a graphene growth support comprising a metal catalyst thin film for graphene growth Wherein the graphene layer comprises graphene grown by vapor deposition.

Yet another aspect of the present invention provides a method of growing a graphene sheet, comprising: providing a graphene growth support comprising a metal catalyst for graphene growth to a carbon source and heat to grow a graphene sheet on the support; Cooling at least one of the support and the graphene sheet to form a corrugation on the graphene sheet; Soluble graphene sheet having a thermal expansion coefficient different from that of the graphene.

Yet another aspect of the present application is a graphene sheet grown on a graphene growth support comprising a metal catalyst for graphene growth wherein the support is a graphene sheet from which the graphene sheet is separated or contacted, Soluble graphene sheet.

Another aspect of the present application is an element comprising a deformable water soluble graphene sheet, wherein the deformable water soluble graphene sheet is a graphene sheet grown on a graphene growth support comprising a metal catalyst for graphene growth, Wherein the graphene sheet is a graphene sheet that is separated or tangent, and wherein the graphene sheet is wrinkled.

A large area graphene film pattern having a centimeter size or more can be easily manufactured by depositing a metal thin film pattern on a substrate and synthesizing graphene using a chemical vapor deposition method. Further, by etching and transferring the produced graphene film pattern, it is possible to produce graphene electrodes of various patterns on a desired substrate. In addition, a carbon source may be provided on a growth support of graphene containing a metal catalyst for graphene growth to form wrinkles imparting strain water solubility to the graphene sheet in the process of forming the graphene sheet. This makes it easy to impart strain water solubility to the graphene sheet. The deformation water solubility of the graphene sheet can be controlled by adjusting the size of the wrinkles. Further, strain water solubility can be further imparted to the deformable water-soluble graphene sheet. The fabricated deformable water-soluble graphene sheet can be used as an electrode material or the like in various devices, so that the performance of the deformable water-soluble graphene sheets can be maintained even when there is deformation of the device shape.

Accordingly, a large area graphene film pattern can be easily manufactured by the present invention, and various patterns of graphene electrodes can be manufactured on a desired substrate using the prepared large area graphene film. Accordingly, it is expected that the graphene film pattern and the stretchable electrode / wire using the graphene film pattern will be used not only as a core material of flexible electronic devices but also as a substitute for conventional electrode / wire materials such as ITO / copper.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram illustrating a process of synthesis, etching, and transfer of a graphene sheet according to an embodiment of the present invention; FIG.
Figure 2 is a schematic diagram illustrating a process of graphene sheet synthesis, etching, and transfer according to one embodiment of the present application: a) a synthesis process, b) etching and transfer of a metal catalyst thin film for graphene growth, c) Post - etching of metal catalyst thin films for growth of graphene films.
FIG. 3A is an optical microscope image of a graphene film according to the reaction time and the catalyst thickness, and FIG. 3B is an optical microscope image showing a very large grain size of 100 micrometers or more after the graphene grown under optimum conditions . Figure 3c is a graph comparing the number of graphene layers grown under different conditions of reaction time and catalyst thickness.
Fig. 4 is data showing the characteristics of the graphene film analyzed by various methods: a) scanning electron microscope photograph, b) transmission electron microscope photograph, c) optical microscope and atomic probe microscope (AFM) Spectrometer analysis results.
FIG. 5 is a photograph showing the process of etching a metal catalyst thin film with FeCl ₃ and then transferring it to various substrates: a) a graphene film formed from a Ni thin film, b) a graphene film separated from a 1M FeCl ₃ aqueous solution, c) Gf) transferring the graphene pattern onto the insulating substrate by stamping, df) contacting and etching on the PDMS substrate, gh) transferring the graphene pattern onto the insulating substrate by stamping.
Fig. 6 is data showing electrical and optical characteristics of the graphene film: a) the light transmittance according to the wavelength change and the light transmittance according to the UV-ozone etching time, b) the quantum of the nano device using the synthesized graphene (Quantum Hall) conduction phenomenon, and (c) folding property test results of graphene film transferred on transparent PET film. d) Tensile property test result of graphene film transferred onto stretchable transparent PDMS substrate.
Figure 7 is a photograph illustrating the manner in which the relative position of the sample on the CVD reactor is regulated and cooled.
8A is a schematic diagram illustrating individual corrugations formed on a graphene sheet according to one embodiment of the present disclosure.
FIG. 8B is a schematic plan view of the corrugation formed on the graphene sheet according to one embodiment of the present invention. FIG.
8C is a schematic diagram showing a cross section (AA 'section) of individual pleats formed in the graphene sheet according to one embodiment of the present application.
9 is a schematic diagram illustrating two examples of methods of imparting additional strain water solubility according to one embodiment of the present disclosure.
10 is a schematic diagram illustrating two aspects of a graphene sheet having a profile repeating rising and falling according to one embodiment of the present disclosure;
11 is a graph showing resistance changes (Rx, Ry) along each axis (x, y axis) when the deformable water-soluble substance according to the second embodiment is bent and deformed in the uniaxial (y axis) direction. The X-axis of the graph represents the bending radius (mm), which is the radius of the curved portion when bending the deformable water-soluble material, and the Y-axis represents the resistance (kΩ).
12 is a graph showing changes in resistance along the y-axis while stretching the water-soluble substance according to the second embodiment in a single axis (y-axis) direction. The X-axis of the graph represents the stretching ratio (%) and the Y-axis represents the resistance (kΩ).
13 is a graph showing changes in resistance along the y-axis while stretching the deformable water-soluble substance according to the fifth embodiment in the uniaxial (y-axis) direction. The X-axis of the graph represents the stretching ratio (%) and the Y-axis represents the resistance (kΩ).
14 is a graph showing resistance changes (Rx, Ry) of each axis (x, y axis) when the deformable water-soluble substance according to the sixth embodiment is stretched in two axes (x and y axes). The X-axis of the graph represents the stretching ratio (%) and the Y-axis represents the resistance (Ω).
15A and 15B are views showing a pattern of a pattern of a herringbone shape formed by isotropic expansion. After a rubber substrate is isotropically expanded by applying a force, a silicone film is adhered onto an isotropically expanded rubber substrate And then removing the force applied to the rubber substrate.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. It should be understood, however, that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

Throughout this specification, when an element is referred to as " including " an element, it is understood that the element may include other elements as well, without departing from the other elements unless specifically stated otherwise. Throughout this specification, the term " to " does not mean " a step for. &Quot;

Throughout this specification, it is to be understood that when a layer or member is "on" another layer or member, it is not only the case where a layer or member is in contact with another layer or member, Or < / RTI > another member is present. Also, when an element is referred to as "comprising ", it means that it can include other elements as well, without departing from the other elements unless specifically stated otherwise.

The terms " about ", " substantially ", etc. used to the extent that they are used throughout the specification are intended to be taken to mean the approximation of the manufacturing and material tolerances inherent in the stated sense, Accurate or absolute numbers are used to help prevent unauthorized exploitation by unauthorized intruders of the referenced disclosure.

In the present description, a deformation means all possible shape changes such as bending, swelling, stretching, compression, creep, warping, wrinkling, etc., and includes not only a change in one direction but also a change in shape in all directions. Thus, the term deformability means a meaning including, for example, compression or stretchable, bendable, flexible, and the like.

In the present specification, the strain water solubility refers to a property capable of preventing or reducing changes in physical properties such as electrical and / or mechanical properties such as resistance due to deformation when a strain is present or disappears after the strain is present.

Herein, the corrugation means that the corrugation shows a discontinuous rising or falling profile at a part based on the flat surface of the graphene sheet.

In the present application, the width of the corrugation is the length from the point where the corrugation starts to rise or fall to the point where the corrugation starts to descend or rise on the cross section of the individual corrugations, and the height of the corrugation is the inflection point To a flat surface of the graphene sheet at the inflection point) of the graphene sheet.

In the present invention, in the profile repeatedly rising and falling, the height is the height of the inflection point changing from rising or falling to falling or rising, that is, a vertical length from the inflection point to the flat surface when there is no corresponding rise or fall , And the width means the length from the point where it starts to rise or fall to the point where it completes the descent or rise.

In the present application, the wave shape means a shape in which the graphene sheet and the elastic body in contact with the graphene sheet together exhibit a profile repeatedly rising and falling.

In the present application, the buckle shape means a shape in which the graphen sheet contacts the elastic body at an inflection point, having a profile repeatedly rising and falling on the elastic body.

As used herein, the graphene growth support may be comprised of a metal catalyst for graphene growth to grow graphene or may comprise an additional substrate formed thereon, such as a sacrificial layer, have.

One aspect of the present invention is a process for producing a graphene sheet, comprising growing graphene on the support by providing a graphene growth support comprising a metal catalyst thin film for graphene growth, Of the present invention. By this method, it is possible to easily produce a large area graphen having a transverse or longitudinal length ranging from 1 mm to 1000 m, and also to provide a large area graphene having a homogeneous structure with few defects Can be manufactured. The graphene film may comprise a single layer or multiple layers of graphene.

In an exemplary embodiment of the present application, the method may further include cooling at least one of the support and the graphene sheet, but is not limited thereto.

In an exemplary embodiment of the invention, the metal catalyst thin film for graphene growth may be patterned, but is not limited thereto. For example, the metal catalyst thin film for graphene growth may be patterned before the graphene growth reaction so as to have various shapes and line width pattern shapes. The patterning of the metal catalyst thin film for graphene growth can be performed by a person skilled in the art among the methods known in the art. By controlling the shape of the pattern of the metal catalyst thin film for graphene growth, a desired shape of the graphene pattern can be grown thereon.

 In an exemplary embodiment of the present invention, the metal catalyst for graphene growth is selected from the group consisting of Ni, Co, Fe, Pt, Au, Al, Cr, Cu, Mg, Mn, Mo, Rh, Si, Ta, But is not limited to, one or more metals or alloys selected from the group consisting of Al, V, Zr, brass, bronze, stainless steel and Ge. In one embodiment, the metal catalyst thin film for graphene growth may have a thickness of 10 nm or more. For example, the thickness of the metal catalyst thin film for graphene growth may be 10 nm to 100 탆, or 10 nm to 10 탆, or 10 nm to 1 탆, or 10 nm to 500 nm, or 10 nm to 300 nm, But is not limited to, 100 nm to 100 탆, or 100 nm to 10 탆, or 100 nm to 1 탆, or 100 nm to 500 nm, or 100 nm to 300 nm.

In an exemplary embodiment of the present invention, the thickness of the graphene sheet can be controlled by the thickness of the metal catalyst thin film for graphene growth, the reaction time, or the cooling rate, but is not limited thereto.

In one embodiment of the invention, the graphene sheet may be grown by chemical vapor deposition (CVD), which may be formed on a graphene growth support comprising a metal catalyst thin film for graphene growth. The graphene can be grown by providing a carbon source and heat to a graphene growth support comprising the metal catalyst thin film for graphene graphene growth. The carbon source may be, for example, carbon monoxide, carbon dioxide, methane, ethane, For example, at a temperature of 300 to 2000 占 폚 while supplying a carbon source such as ethylene, ethanol, acetylene, propane, butane, butadiene, pentane, pentene, cyclopentadiene, hexane, cyclohexane, benzene, The carbon components present in the carbon source are combined to form a hexagonal plate-like structure, and graphene is grown.

According to an exemplary embodiment of the present invention, the method of manufacturing a graphene sheet includes forming an ion or a neutral plasma while controlling the pressure and concentration of the reaction gas to promote separation of the reaction gas, Including, but not limited to, < RTI ID = 0.0 >

In an exemplary embodiment of the invention, the graphene sheet may comprise a single layer or multiple layers of graphene, but is not limited thereto.

Another aspect of the present invention provides a graphene sheet comprising graphene grown by chemical vapor deposition on a graphene growth support comprising a metal catalyst thin film for graphene growth. The method of manufacturing the graphene sheet may be applied to the graphene sheet.

Another aspect of the present invention provides an element comprising the graphene sheet. For example, since the graphene has high transparency, it can be applied to the manufacture of various electric and electronic devices, and particularly applicable to the production of electrodes for various electric and electronic devices. For example, Practical use of graphene transparent electrodes for photoelectronic applications in the manufacture of electrodes for electronic and electronic devices, or in solar cells, touch sensors and related flexible electronic technologies can be realized.

Another aspect of the present application is a graphene laminate comprising a graphene sheet transferred onto an elastic substrate, the graphene sheet having a chemical vapor phase on a graphene growth support comprising a metal catalyst thin film for graphene growth Wherein the graphene layer comprises graphene grown by vapor deposition.

In an exemplary embodiment of the invention, the stretchable substrate may be pre-stretched in one, both, or all directions prior to transfer of the graphene sheet, but is not limited thereto.

 In the exemplary embodiments herein, the stretchable substrate may be transparent, but is not limited thereto. The stretchable base material may be a transparent stretchable base material known in the art without any particular limitation. For example, various organic and inorganic polymers such as plastic and silicone polymers may be used.

Yet another aspect of the invention provides an element comprising the graphene laminate. For example, since the graphene has high transparency, it can be applied to the production of various electric and electronic devices, and can be particularly useful for manufacturing electrodes of various electric and electronic devices. For example, the practical use of graphene transparent electrodes for photoelectronic applications in the manufacture of electrodes for various electronic devices, such as next generation field effect transistors or diodes, or in the field of solar cells, touch sensors and related flexible electronic technologies have.

 According to another aspect of the present invention, graphene grown by chemical vapor deposition on a graphene growth support containing a metal catalyst thin film for graphene growth is immersed in an etching solution to separate the graphene from the support to form a substrate, And transferring the graft sheet onto a recording medium.

In an exemplary embodiment of the present invention, the etching solution may include, but is not limited to, the metal catalyst thin film for graphene growth or an echant capable of removing the graphene growth support. The etching solution may include, but is not limited to, for example, HF, BOE, Fe (NO ₃ ) ₃ , or iron (III) chloride.

Hereinafter, one embodiment of large area graphene fabrication using Chemical Vapor Deposition (CVD) according to the present invention will be described, but the present invention is not limited thereto.

Hydrocarbons on conventional reactive nickel or transition-metal-carbide surfaces can produce a thin graphite layer by chemical vapor deposition, but a large amount of carbon source adsorbed on nickel foils is It is known that there is a problem of forming a graphite crystal (Fig. 3A) thicker than the fin film. Accordingly, the above problem can be solved by growing graphene by a chemical vapor deposition method using a metal catalyst thin film for graphene growth.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram illustrating a process of synthesis, etching, and transfer of a graphene sheet according to an embodiment of the present invention; FIG.

In one embodiment, the catalyst is used as a catalyst for graphene growth by using a thermal evaporator, an e-beam evaporator, a sputter or an electro-plating method or the like (B), bronze, stainless steel (B), and at least one selected from the group consisting of Ni, Co, Fe, Pt, Au, Al, Cr, Cu, Mg, Mn, Mo, Rh, Si, Ta, Ti, W, a metal catalyst thin film 30 for graphene growth comprising at least one metal or alloy selected from the group consisting of stainless steel and Ge is formed on the substrate 10 or the sacrificial layer 20 formed on the substrate, ₂ layer (Fig. 1A).

When the metal catalyst thin film 30 for growing graphene is patterned, various pattern masks are formed on the substrate by using typical photolithography or electron-beam lithography. Subsequently, using a thermal evaporator, an e-beam evaporator, a sputter, or an electro-plating method, Ni, which acts as a catalyst for graphene growth, (B), bronze, stainless steel (Co), Fe, Pt, Au, Al, Cr, Cu, Mg, Mn, Mo, Rh, Si, Ta, Ti, W, U, V, Zr, steel, and Ge may be formed on the surface of the catalyst layer.

The deposited metal catalyst thin film for graphene growth is placed in a reactor and hydrogen gas is flowed while heating to remove the oxide layer and impurities of the metal thin film layer. Then, the treated metal catalyst thin film for graphene growth is heated to a high temperature, and a gas containing carbon, such as carbon monoxide, carbon dioxide, methane, ethane, ethylene, ethanol, acetylene, propane, butane , At least one gas selected from butadiene, pentane, pentene, cyclopentadiene, hexane, cyclohexane, benzene, toluene and the like is injected into the reactor (FIG. After increasing the degree of vacuum, an electric field is applied to generate a plasma Chemical vapor deposition [Plasma-Enhanced; (PE) CVD] method can be used to lower the growth temperature. When a sufficient amount of carbon is absorbed by the metal catalyst thin film layer for graphene growth and then rapidly cooled, carbon is separated from the metal catalyst thin film layer for graphene growth and crystallized as it exits to the surface. Depending on the amount of carbon, Thereby forming a thin film structure (see FIG. 1C; FIGS. 3 to 6). The thickness of the graphene film 50 formed as described above can be controlled by changing the reaction time, the thickness of the catalyst metal thin film, and the cooling rate. The shorter the reaction time and the thinner the metal thin film, the thinner the graphene film is formed.

It is possible to separate the formed graphene sheet or graphene pattern from the metal catalyst thin film for graphene growth using various acids or HF, BOE, FeCl ₃ , Fe (NO ₃ ) ₃ and the like to transfer them to various substrates. The formed graphene sheet can be regulated in thickness by irradiating UV having a strength of tens of W at normal temperature / normal pressure.

Etching the metal catalyst thin film for graphene growth and transferring the separated graphene sheet to another substrate is important for device application. Normally, metal catalysts such as nickel can be etched by strong acids such as HNO ₃ , but these acids often produce hydrogen droplets and damage the graphene.

Accordingly, in one embodiment of the present invention, an aqueous solution (1 M) of iron (III) chloride (FeCl ₃ ) may be used as an oxidizing etchant to remove the metal catalyst thin film for graphene growth. The net ionic equation can be expressed, for example, when the metal catalyst thin film for graphene growth includes Ni:

^{2Fe 3 + (aq) + Ni} (s) -> 2Fe 2 + (aq) + Ni 2 + (aq).

This oxidation-reduction process can slowly etch the nickel film effectively in a mild pH range without forming gaseous products or precipitates. After several minutes, the graphene film separated from the substrate floats above the surface of the solution (Figs. 1g and 1h; see Figs. 5a and 5b), and the floating graphene film can be transferred onto another target substrate.

In another embodiment, the sacrificial layer 20 is removed using a buffered oxide etchant (BOE) or hydrogen fluoride solution to remove the graphene sheet 50 and the metal catalyst thin film for graphene growth 30) floats on the surface of the solution (Fig. 1G). The remaining metal catalyst thin film for graphene sheet / graphene floating on the surface of the solution is completely removed by further reaction with BOE or hydrogen fluoride solution (FIG. 1H). The metal catalyst thin film 30 for graphene growth is removed and the suspended graphene film 50 can be transferred to the target substrate 70 (FIG. 1F, FIG. 2C).

In another embodiment, the graphene film can be dry-transferred using a soft substrate such as polydimethylsiloxane (PDMS). The PDMS stamp 60 is brought into contact with the graphene film grown by chemical vapor deposition on the metal catalyst thin film for growing graphene (FIG. 1d; FIG. 5d). The metal catalyst thin film 30 for growing graphene is etched using an etchant as described above to attach the graphene film 50 on the PDMS stamp 60 (see FIG. 1E, FIG. 5E). The pre-patterned metal catalyst film for graphene growth (see FIG. 5C) can be used to transfer the graphene film of various sizes and shapes to any substrate (FIG. 1F). The dry-transfer process would be very useful in fabricating large-scale graphene electrodes and devices without additional lithography processes (Figures 5f-5h).

The graphen sheet or pattern can be transferred to a flexible plastic substrate or a rubber substrate having a very good elasticity. For example, when a stretchable substrate is pulled in advance and then transferred, very stable electric characteristics can be obtained. It is more stable when pulled uniformly in two directions or all directions perpendicular to each other and then transferred.

Further, as shown in the photograph of FIG. 7, the cooling rate can be easily adjusted by changing the relative positions of the reactor and the sample (FIG. 7). By extending this concept, it is possible to continuously process the synthesis of graphene electrodes. In this regard, the substrate can be preheated, deposited, and cooled all at once as it passes through the reactor where the growth temperature is maintained.

In addition, in the exemplary embodiments of the present application, the graphene film pattern prepared as described above may be transferred onto a stretchable substrate pre-stretched in one, both or all directions to obtain stable electrical characteristics . By using the stretchable substrate on which the graphene film pattern is transferred, a stretchable electrode having various electrical characteristics and various electric / electronic devices can be manufactured.

Yet another aspect of the present invention provides a method of growing a graphene sheet comprising the steps of: providing a graphene growth support comprising a metal catalyst thin film for graphene growth to a carbon source and heat to grow a graphene sheet on the support; And cooling the at least one of the support and the graphene sheet to form a corrugation on the graphene sheet, wherein the thermal expansion rate of the support is different from that of the graphene, to provide.

Yet another aspect of the present application is a graphene sheet grown on a graphene growth support comprising a metal catalyst for graphene growth wherein the support is a graphene sheet from which the graphene sheet is separated or contacted, And the corrugation provides a deformable water-soluble graphene sheet formed by a difference in thermal expansion coefficient between the support and the graphene sheet.

Another aspect of the present application is an element comprising a deformable water soluble graphene sheet, wherein the deformable water soluble graphene sheet is a graphene sheet grown on a graphene growth support comprising a metal catalyst for graphene growth, Wherein the graphene sheet has wrinkles formed thereon, the wrinkles providing a device formed by a difference in thermal expansion coefficient between the support and the graphene sheet.

In exemplary embodiments of the invention, a carbon source and heat are provided on a growth support of graphene comprising a metal catalyst for graphene growth to grow a graphene sheet, followed by cooling of the support and the graphene sheet. Here, the support and the graphene sheet have a difference in thermal expansion coefficient. Therefore, when the graphene sheet and the support in contact with the graphene sheet are cooled together, the graphene sheet can be formed with wrinkles in a process in which the thermally expanded graphene sheet and the support shrink to different degrees to each other. Here, in order to form the corrugation of the graphen sheet, a support including a catalyst layer having a thermal expansion coefficient higher than that of the graphene is used.

The formed corrugations may impart strain water solubility to the graphene sheet. For example, in the case of a graphene sheet without wrinkles, various deformation occurs due to the application of an external strain, resulting in mechanical damage such as cracks or fractures, for example, Electrical resistance value and the like can be increased. The corrugation may provide a role of preventing or preventing an increase in the electrical resistance value or reducing the degree of increase in the graphene sheet, that is, deformation water solubility.

Furthermore, by imparting a profile that repeats rising and falling to the corrugated graphene sheet, the deformation water solubility can be further increased. In a profile repeating the up and down movements, the height and width are greater than the height and width of the corrugations (e.g., about 10 to 30 times the difference).

As a non-limiting example of a metal catalyst for graphene growth that is used in exemplary embodiments, at least one metal selected from the group consisting of Ni, Co, Fe, Pt, Au, Al, Cr, Cu, Mg, Mn, Mo, Rh, , W, U, V, Zr, brass, bronze, stainless steel and Ge. The metal catalyst layer for graphene growth may be a thin film or a thick film. When the metal catalyst film for growing graphene is a thin film, the thickness may be 1 nm to 1000 nm. When the metal catalyst layer for growing graphene is a thick film, the thickness may be 0.01 mm to 5 mm.

Here, the manufacturer can adjust the thickness of the graphene by adjusting the thickness of the metal catalyst film for graphene growth. That is, the manufacturer can form a desired number or thickness of layers of graphene by controlling the thickness of the formation of the metal catalyst layer for graphene growth.

On the other hand, the manufacturer can increase the size of the metal crystal grains of the metal catalyst layer for graphene growth by reducing the defects such as grain boundaries through H ₂ gas, heat treatment process, The electrical, optical, and chemical properties of the pin can be improved.

There are various methods for forming graphene by providing a carbon source and heat on a graphene growth support such as a metal catalyst film for graphen growth or a metal catalyst film for graphening growth formed on a substrate such as, for example, silicon oxide.

Non-limiting examples of such methods include chemical vapor deposition (CVD) methods in which graphene is grown by introducing a gaseous carbon source in the presence of a metal catalyst film for graphene growth and performing a heat treatment process. Specifically, a metal catalyst for graphene growth is formed in the form of a film, which is then placed in a chamber and a gas containing carbon monoxide, carbon dioxide, methane, ethane, ethylene, ethanol, acetylene, propane, butane, butadiene, pentane, pentene, cyclopentadiene, When a carbon source such as cyclohexane, benzene, toluene or the like is introduced into the gas phase while being subjected to a heat treatment at a temperature of, for example, 300 to 2000 ° C, the carbon components present in the carbon source combine to form a hexagonal plate- .

Thereafter, when the sheet is cooled to room temperature at a cooling rate of about 30 ° C to 600 ° C per minute (30 ° C / min to 600 ° C / min), a graphene sheet having a wrinkled shape and having a uniform arrangement can be obtained. Such wrinkles are formed due to the difference in thermal expansion coefficient between the graphene and the metal catalyst for graphene growth. For example, yes, and coefficient of thermal expansion of the pin is about 0.5 to 0.75 x 10 ^-5 / K, the coefficient of thermal expansion pin is yes if you are using a metal catalyst for the growth of Ni is about 1.4 x 10 ^-5 / K.

Here, the manufacturer can adjust the number of layers of graphene synthesized by controlling the cooling rate. That is, the manufacturer can control the cooling rate directly or indirectly with respect to the metal catalyst film for graphene and / or graphene growth so that the number of graphene layers (total thickness of graphene) can be formed to a desired degree .

Meanwhile, in order to perform the heat treatment process, a furnace for heating the chamber is used. According to the present invention, a method of separating the furnace from the chamber during the cooling process can be used. To do this, the designer can design the furnace and chamber so that they can easily move and separate the furnace from the chamber if necessary. In this case, the heat is applied to the chamber during the heat treatment process, and since the furnace itself can be moved away from the chamber during the cooling process, the cooling rate can be controlled quickly.

Also, contrary to the above case, it is possible to use a method of separating the chamber from the furnace during the cooling step, and the designer can easily separate the chamber in which the graphene is located from the furnace, a furnace can be designed. In this case, since heat can be applied to the chamber during the heat treatment process and the chamber can be moved away from the furnace during the cooling process, the cooling rate can be controlled quickly.

In addition, during the cooling process, the furnace and chamber can be fixed and the cooling rate can be controlled by moving the catalyst substrate where graphene growth occurs. With this method, it is possible to mass-produce graphene by continuous heating-growth-cooling through a process of putting a roll-shaped catalyst substrate into a reactor and winding it from the other side while loosening from one side .

As another non-limiting example, there is a so-called carburization process in which, for example, a metal catalyst for graphene growth is brought into contact with a liquid carbonaceous material, carbon decomposed from the liquid carbonaceous material is permeated into the metal catalyst for graphene growth by a preliminary heat treatment And then heat is applied thereto to form graphene on the metal catalyst film for graphene growth. The graphene is cooled to a temperature of about 30 to 600 ° C (30 ° C / min to 600 ° C / min) Graphene sheet having a wrinkled state can be obtained. As described above, the corrugation is formed due to the difference in thermal expansion coefficient between the graphene and the metal catalyst for graphene growth. The direction of the corrugation can be arbitrarily set and can be adjusted when graphene is formed or adhered to a catalyst layer having a different thermal expansion coefficient in a specific direction or a carrier physically stretched in a specific direction.

The contacting process between the metal catalyst for graphene growth and the liquid carbonaceous material may be performed by a process such as dipping. Examples of such liquid carbonaceous materials include organic solvents, and any liquid carbonaceous material including carbon and capable of being thermally decomposed by the metal catalyst for graphene growth can be used without limitation. As a non-limiting example, a polar or nonpolar organic solvent having a boiling point of 60 to 400 ° C may be used. As such an organic solvent, an alcohol organic solvent, an ether organic solvent, a ketone organic solvent, an ester organic solvent, an organic acid organic solvent, or the like can be used. Alcohol-based and ether-based organic solvents can be used in view of ease of adsorption to a metal catalyst for growth of graphene, good reactivity, and excellent reducing power. When the liquid carbonaceous material is used, the carburization process can be performed by a preliminary heat treatment process, and the liquid carbonaceous material can be pyrolyzed by the metal catalyst for graphene growth by the preliminary heat treatment process. The preliminary heat treatment for pyrolysis may be carried out under agitation so that sufficient mixing of the liquid carbonaceous material and the catalyst can be performed, and may be performed at a temperature of 100 to 400 ° C. for 10 minutes to 24 hours.

In addition to the exemplary methods described above, exemplary embodiments herein may utilize any method that forms and then cools a graphene sheet on a graphene growth support comprising a metal catalyst for graphene growth, and is not limited to any particular method.

The prepared graphene sheet is a graphene sheet in which a plurality of carbon atoms are linked to each other through a covalent bond (usually sp ² bond) to form a polycyclic aromatic molecule. The graphene sheet has locally folded wrinkles It may have occurred. In the graphene sheet, carbon atoms linked by a covalent bond form a 6-membered ring as a basic repeating unit. However, it is also possible that the graphene sheet further includes a 5-membered ring and / or a 7-membered ring. The structure of the corrugated graphene sheet may vary depending on the content of the 5-membered ring and / or the 7-membered ring which may be contained in the graphene. Generally, the side ends of the graphene sheet are saturated with hydrogen atoms.

Illustratively, the corrugated graphene sheet may be a large area graphene sheet having a transverse and longitudinal length ranging from 1 mm to 1,000 m. It may also be a graphene sheet having a homogeneous structure with few defects. The width and width of the corrugation in these graphene sheets vary with the degree of cooling.

The growth support of the graphene sheet, such as the metal catalyst film for graphene growth, which is in contact with the back surface of the produced graphene sheet, can be used without removing or removing it. For example, when a graphene sheet is applied to a substrate or an element or a plate-like elastic body as described later, the graphene sheet from which the support is removed can be transferred to a substrate or element or transferred directly without removing the support if necessary. As the method of removing the support, a wet or dry etching method using an acid solution, a salt solution, an organic oxidizing solvent, or the like can be used.

FIG. 8A is a schematic diagram showing individual pleats formed in a graphene sheet in an exemplary embodiment of the present disclosure, and FIG. 8B is a schematic plan view generally showing corrugations formed in a graphene sheet in the exemplary embodiment of the present disclosure; FIG.

Referring to FIG. 8A, corrugations are formed on the graphen sheet. Referring to FIG. 8B, it can be seen that the corrugations are irregularly formed in the graphene sheet. As described above, the corrugation is formed due to the difference in thermal expansion coefficient between the graphene growth support and the graphene sheet.

The corrugation may impart strain water solubility to the graphene sheet. If graphene sheets are subjected to external forces that cause various deformation such as bending, stretching, elongation, compression, creep, warpage, creasing, etc., in graphene sheets in a completely flat state, cracks or breakage Mechanical damage such as fracture may occur. Such mechanical damage can lead to an impairment of electrical properties such as an increase in electrical resistance value. In the case of forming a wrinkle on the graphene sheet when forming the graphen sheet, even if an external force is applied to the graphene sheet, the wrinkle can be coped with by folding or stretching. Such a countermeasure can prevent or suppress the possibility of changes in physical properties due to deformation of the graphene sheet such as bending, stretching, elongation, compression, crevice, warping, wrinkling, The local correspondence of the corrugation to the external force is in contrast to the whole sheet corresponding to the force from the outside. It is easy to prevent or suppress the occurrence of mechanical damage such as cracking or breakage due to the presence of the wrinkles and it is easy to prevent or suppress the change of the electrical characteristics of the graphene sheet.

The corrugated graphene sheet may, for example, allow it to accommodate a deformation of greater than 0% to 5% (e.g., 5% of the elongation strain).

FIG. 8C is a schematic diagram showing a cross section (AA 'section) of individual pleats formed in the graphene sheet in the exemplary embodiment of the present disclosure; FIG. 8C, the pleats have a height h and a width w. The height h may be 50 nm to 300 nm and the width w may be 10 nm to 200 nm. The height (h) and the width (w) of the corrugation may vary within the above range depending on the cooling rate and / or the thickness of the graphene. For reference, the height (h) and the width (w) of the wrinkles are about 10 to 30 times larger than the height and width in the ascending and descending profile, such as wave shape or buckle shape, And the like. This difference may vary depending on the strain applied to the elastic body, the thickness of the graphene, and the like.

The measurement of the wrinkle, wave shape, and height and width in the buckle shape can use AFM (Atomic Force Microscopy) at a level of several micrometers, and optical profiler can be used when the height and width are larger.

In the exemplary embodiments of the present application, when forming a graphene sheet on a graphene growth support comprising a metal catalyst for graphene growth, the cooling rate is adjusted during cooling to decrease the rate of formation of the wrinkles, irregularity in shape of wrinkles, Height, width of wrinkles and the like can be adjusted.

If there is a difference in the coefficient of thermal expansion between the graphene support and graphene, if the cooling rate is high, the rate of occurrence of wrinkles due to rapid cooling may become large, and the height of wrinkles may become large and the width may be narrowed. Conversely, the smaller the cooling rate, the lower the wrinkle height and the wider the width.

Illustratively, when forming a graphene sheet on a graphene growth support comprising a graphenic metal catalyst and cooling, the cooling rate can be controlled in the range of 30 ° C to 200 ° C per minute. If the cooling rate is faster than the above range, cracks of the support may occur. If the cooling speed is slower than the cooling speed range, wrinkles may not be generated. In the cooling rate range, the height and width of the corrugations may be 50 nm to 300 nm and 10 nm to 200 nm, respectively, as described above.

In the exemplary embodiments of the present application, when a graphene sheet is formed on a graphene growth support including a metal catalyst for graphene growth, by adjusting the thickness of the graphene sheet, the wrinkle formation ratio of the graphene sheet, irregularity in shape of wrinkles, The height of the wrinkles, the width of the wrinkles, and the like can be adjusted.

The graphene sheet may be composed of a single layer of raffinate or a plurality of layers may be laminated to form a plurality of layers (up to 300 layers). Depending on the thickness of the graphene sheet, the ratio of formation of wrinkles, irregularity of wrinkles, It can be adjusted.

Illustratively, the thickness of the graphene sheet can be adjusted in the range of 1 to 50 layers. If grains larger than the above range are formed, the physical properties of the graphene itself as well as the physical properties of the graphite can be obtained. Also, the thickness of the graphene layer is too thick, which may make it difficult to produce wrinkles. In the thickness range, the folds may have a height and a width of 50 nm to 300 nm and 10 nm to 200 nm, respectively, as described above.

Hereinafter, a method of imparting strain water solubility to the deformed water-soluble graphene sheet prepared above will be described.

The corrugation imparts strain water solubility to the graphene sheet. In addition to such wrinkles, by imparting a profile to the sheet repeatedly rising and falling more than the wrinkles, the deformation water solubility imparted by the wrinkles can be further imparted.

As such a method for imparting strain water solubility, for example, an elongated plate-like elastic body can be used.

That is, as described above, the graphene sheet having the deformation water-soluble property through the wrinkle is contacted with the elongated plate-like elastic body, and then the elastic body is contracted again from the stretched state, Can now repeat the rising and falling profiles with the wrinkles having a greater height and width than the wrinkles.

Here, the plate-like elastic body may be obtained by, for example, stretching in the uniaxial direction, or stretching in the biaxial direction. In the case of using the plate-shaped elastic body drawn in the uniaxial direction, a graphene sheet having a profile repeatedly rising and falling in the uniaxial direction will be obtained. In the case of using the plate-like elastic body drawn in the biaxial direction, It is possible to obtain a graphen sheet having a profile repeatedly rising and falling. It is also possible to use those obtained by stretching the plate-shaped elastic material in the direction of three or more axes. For example, a plate-like elastic body drawn in the directions of four axes can be used. Further, for example, a plate-like elastic body drawn in all directions of the plate-like elastic body, that is, in all directions in the radial direction, may be used. In this case, the graphene sheets brought into contact with the plate-like elastic body are subjected to isotropic expansion, and wrinkles are formed on the graphene sheet by isotropic expansion. The pattern shape of the wrinkles at that time is a shape of a herringbone ).

As a non-limiting example of the elastic body, a polymer elastic body having a silicone or ethylene chain such as polydimethylsiloxane (PDMS) can be used.

The deformable water-soluble graphene sheet, which is primarily wrinkled to be shrunk by using the stretched plate-shaped elastic body, may be used as it is in a sheet form or in a ribbon form.

Accordingly, the graphene sheet having the increased water solubility can have a ribbon shape repeatedly rising and falling in the uniaxial or biaxial direction, or a sheet shape repeatedly rising and falling in the uniaxial or biaxial direction .

Figure 9 is a schematic diagram illustrating two examples of methods of imparting additional strain water solubility in exemplary embodiments of the present disclosure.

Referring to FIG. 9A, a graphene sheet to which deformation water-solubility is imparted by forming a wrinkle primarily lies on a base material 100 so as to have a ribbon shape. For reference, the substrate 100 may be a graphene growth substrate or a substrate different from the growth substrate onto which the graphene sheet is transferred. The case of FIG. 9B is also the same.

After the ribbon-shaped graphene sheet 51 is brought into contact with the uniaxially stretched (L + DELTA L) plate-shaped elastic body 81 and the elastic body is again shrunk (L), a shrunk ribbon- The sheet 51 is contracted together and a profile repeatedly rising and falling in the uniaxial direction may appear on the contracted graphene sheet 52 in the form of a ribbon in contact with the contracted elastic body 83. [ The repetition of the rising and falling may be periodic or aperiodic. Here, the shrinkage of the elastic body does not necessarily have to be a shrinkage to the original state, and it is of course possible to shrink the shrinkage to an arbitrary intermediate state between the stretched state and the original state.

Referring to Fig. 9B, a graphene sheet 53 having a sheet-like deformation-water-accepting property is formed on the base material 100 by firstly forming wrinkles.

The graphene sheet 53 to which the sheet-like strain water solubility is imparted is brought into contact with the biaxially stretched [(L + DELTA L) x (L + DELTA L)] plate-like elastic body 82 and transferred, The sheet-like graphene sheet 53 is contracted together with the shrinkage (LxL) so that the shrunk sheet-like graphene sheet 54 in contact with the contracted elastic body 83 is also raised and lowered in the biaxial direction Lt; RTI ID = 0.0 > a < / RTI > The repetition of the rising and falling may be periodic or aperiodic. Here, the shrinkage of the elastic body is not necessarily shrunk to the original state, and it is of course possible to shrink it to an arbitrary intermediate state between the drawn state and the original state.

The profile repeatedly provided by the shrinkage after stretching of the elastic body can be imparted with additional strain water solubility to the graphene sheet to which deformation water solubility is imparted by forming a wrinkle primarily.

That is, in the case where a profile is repeatedly applied to the graphene sheets together with the wrinkles, when the force from the outside is applied to the graphene sheet, not only the wrinkles are folded or unfolded, The profile can also be accommodated by expanding or folding in response to external forces. Accordingly, the ability to prevent or suppress the occurrence of mechanical damage such as cracking or breakage can be increased, and as a result, the ability to prevent or suppress the change in the electrical characteristics of the graphene sheet can be increased. That is, formation of a profile that repeats the above-described rise or fall can be said to impart additional strain-accepting property to the graphene sheet.

As described above, the graphene sheet provided with the profile of repeatedly rising and falling with wrinkles can accommodate a deformation of more than 0% but not more than 30% (for example, not less than 0% but not more than 30% of the elongation deformation). Furthermore, the graphene sheet can accommodate 10% to 30% deformation (e.g., 10% to 30% stretch deformation) beyond 5% deformation. This strain water solubility is a result of addition of deformation water solubility as compared with the case where the water solubility is formed within the range of about 5% or less by forming only wrinkles at first.

As described above, the method of forming the wrinkles on the graphene sheet by the difference of the thermal expansion coefficients using the elongated plate-like elastic body has been described in order to impart strain water solubility to the graphene sheet, but the present invention is not limited thereto. That is, according to the present invention, wrinkles can be formed without using a plate-like elastic body. For example, graphene sheets may be transferred in a state of being stretched by applying a force to a substrate to which the graphene is to be transferred, and then the graphene sheet may be subjected to deformation and water solubility by removing the applied force to form wrinkles on the graphene sheet . That is, at least a part of the graphene substrate to be transferred is pulled and stretched, and graphenes are transferred to the graphene sheet to form wrinkles on the graphene sheet, and the wrinkles thus formed impart gravability to the graphene sheet .

For example, the graphen sheet can be stretched by applying a force directly to the substrate to which the graphen sheet is to be attached in all the directions of the graphen sheet, that is, in all directions in the radial direction. Specifically, after the edge of the substrate to which the graphen sheet is to be attached is fixed, a force is applied to the center of the substrate to stretch the substrate. In this case, the substrate is isotropically expanded. When the graphene is transferred while the isotropic expansion of such a substrate is performed and the force applied to the substrate is removed, wrinkles are formed on the graphen sheet. The pattern shape of the wrinkle at that time may be a herringbone shape (see Fig. 15).

10 is a schematic diagram illustrating two aspects of a graphene sheet having a profile repeating rising and falling in an exemplary embodiment of the present disclosure;

10, the graphene sheet on the elastic body 80 has a profile that repeats rising and falling with the elastic body 80, that is, a wavy shape (W in FIG. 10A) A buckle (B in Fig. 10B), which is repeatedly raised and lowered while contacting only the inflection point portion.

Such a profile that repeats the rising and falling can be further reduced in response to the force from the outside or extremely extensively stretched to give the graphene sheet additional wrinkle and strain water solubility. Accordingly, the graphene sheet can prevent or reduce changes in electrical properties, mechanical properties, and the like. For reference, the buckle shape can impart more deformation water solubility to the case of the wave shape. The buckle shape may be a result of imparting a deformation more than the wave shape (for example, increasing the elongation ratio of the elastic body and contracting). For example, if the deformation is less than 10%, the wave image may start to appear, and if it exceeds 10%, the buckle shape may start to appear mainly. When the deformation is in the vicinity of 10%, the wave shape and the buckle shape may appear. On the other hand, in addition to the case where there is a high degree of deformation exceeding 10%, buckling may occur when the adhesive force with the elastic substrate is weak.

Here, the individual wave or buckle has a height and a width. The height may be 1 탆 to 10 탆, and the width may be 1 탆 to 30 탆. These waves and the height and width of the buckle are compared with the height of the wrinkles of 50 탆 to 300 탆, which is the wrinkle height, and 10 탆 to 200 탆, which is the wrinkle width. The height and / or width of the wave or buckle may be about 10 to 30 times greater than the height and / or width of the wrinkles.

In the exemplary embodiments of the present invention, a flexible elastomer can be used as a deformable water-soluble material by contacting a graphene sheet having a water-solubility imparted thereto as a substrate. Here, the graphene sheet to which the strain water-solubility is imparted is one which is primarily imparted with strain water solubility through wrinkles, and in addition, the graphene sheet which is subjected to the upward and downward repetitions, May be a graphen sheet.

The deformable water-soluble graphene sheet or deformed water-soluble material thus produced can prevent or suppress changes in electrical properties and mechanical properties corresponding to various strains. Also, since graphene has high transparency, it can be utilized as an electrode material for various electric and electronic devices requiring flexibility and the like.

For example, electrode materials of various electronic and electric devices such as next generation field effect transistors and diodes which are required to be deformable such as compressible or stretchable, bendable, flexible and flexible, It can be applied to various devices such as tapes, future surgical gloves, surface sensors of articulated robots, and high performance sensors such as hemispherical optoelectronic devices, Can be maintained.

The deformable water-soluble graphene sheet or deformable water-soluble substance thus produced can be applied by compression or stretching in one direction, two directions, or all directions, in which case the conductor-semiconductor characteristics can be controlled. Since graphene compressed in two or more directions has little resistance to folding or rolling, it can be used as an electrode material for flexible electronic devices requiring mechanical deformation such as folding or pulling.

In addition, the deformable water-soluble graphene sheet or deformed water-soluble substance thus produced can control the resistance according to the degree of expansion and contraction. Such properties can be used for electronic devices, sensors, and the like.

Hereinafter, one of the exemplary implementations will be described in more detail by way of non-limiting and exemplary embodiments.

A nickel film with a thickness of 300 nm or less was deposited on a SiO ₂ / Si substrate using an electron-beam evaporator, and the sample was then heated in a quartz tube to 1,000 ° C. under argon air. The reaction gas mixture (CH ₄ : H ₂ : Ar = 50: 65: 200 standard cubic centimeters / minute), and the sample was rapidly cooled to room temperature (~ 25 ° C) at a rate of ~ 10 ° C s ^-1 using flowing argon. It has been found that this rapid cooling rate is important in inhibiting the formation of multilayer graphene and in efficiently separating the graphene layer from the substrate in a post-process.

A scanning electron microscope (SEM; Jeol, JSM6490) image of the graphene film (sheet) formed on the nickel thin film shows a clear contrast between the areas with different numbers of graphene layers (Fig. 4A). A transmission electron microscope (TEM; Jeol, JEM 3010) image (FIG. 3b) shows that the film is mostly composed of fewer layers of graphene. After transferring the film to a silicon substrate with a 300-nm thick SiO ₂ layer, an optical confocal scanning Raman microscope (CRM 200, Witech) image (Figures 4c and 4d) was measured for the same area. The lightest region in Figure 4d corresponds to a monolayer, and the darkest region consists of more than ten layers of graphene. The bilayer structure appears to prevail in TEM and Raman images for the sample grown on a 300-nm thick nickel layer for 7 minutes. Thus, the growth of graphene for various applications can be controlled, and the average number of the graphene layers, the domain size, and the application range of the substrate can be controlled by varying the nickel thickness and growth time during the growth process (Fig. 3).

Nanoscopes IIIa and E, Digital Instruments (AFM) images show a ripple structure caused by the difference in the thermal expansion coefficients of nickel and graphene (inset portion of FIG. 4c). As will be discussed later, such wrinkles can make the graphene film more stable to mechanical stretching and render the film more stretchable. Multilayer graphene samples are desirable in terms of mechanical strength to support large area film structures, while thinner graphene films have higher optical transparency. The above-described nickel layer with shorter growth time provided a dominant monolayer and a two-layer graphene film for microelectronic devices (FIG. 3C).

Nickel thin film etching and thus transfer of the separated graphene film to another substrate is important for device applications. Normally, nickel can be etched by strong acids such as HNO ₃ , but these acids often produce hydrogen droplets and damage the graphene. In this embodiment, an aqueous solution (1 M) of iron (III) chloride (FeCl ₃ ) was used as an oxidizing etchant to remove the nickel thin film. The net ionic equation of this etching etch reaction can be expressed as:

^{2Fe 3 + (aq) + Ni} (s) -> 2Fe 2 + (aq) + Ni 2 + (aq).

This oxidation-reduction process slowly etched the nickel film effectively in a mild pH range without forming gaseous products or precipitates. After a few minutes, the graphene film separated from the substrate was suspended above the surface of the solution (FIGS. 5A and 5B), and this floating graphene film could be transferred onto another target substrate. In the case of using a buffered oxide etchant (BOE) or a hydrogen fluoride solution, the silicon dioxide layer was removed and the patterned graphene and the nickel film were floated on the surface of the solution together. The floating patterned graphene / nickel thin film was completely removed from the remaining nickel thin film by further reaction with BOE or hydrogen fluoride solution (FIG. 2C). Thereafter, the floating graphene film from which the nickel thin film was removed was transferred to a target substrate.

On the other hand, the graphene film was dry-transferred using a soft substrate such as polydimethylsiloxane (PDMS). The PDMS stamp was brought into contact with the graphene film grown by chemical vapor deposition on the nickel thin film (Fig. 5D). The nickel thin film was etched using FeCl ₃ as described above to leave a graphene film adhered on the PDMS substrate (see FIG. 5E). Using the pre-patterned nickel film (Figure 5c), the graphene films of various sizes and shapes were transferred to any substrate. The dry-transfer process will be very useful in fabricating large-area graphene electrodes and devices without additional lithography processes (Figures 5f-5h). A small number of layers of the transferred graphene film exhibit a linear crack pattern with an angle of 60 ° or 120 °, indicating a particular crystallographic edge with large crystalline domains ). In addition, the Raman spectrum measured for the graphene film on the nickel film shows strongly suppressed defect-related D-band peaks, which increase only slightly after the transfer process (FIG. 4c) Showing the overall good quality of the resulting graphene film. Further optimization of the transfer process using the substrate control allows for a transfer yield close to 99%.

For macroscopic transport electrode applications, the optical and electrical properties of a 1 × 1 cm ² graphene film were determined using an ultraviolet-visible spectrometer and a four-probe Van der Pauw method Pauw methods) (Figs. 6A and 6B). The suspended graphene film was transferred to a quartz plate, and the transmittance was measured using ultraviolet-visible spectrum (UV-3600, Shimazdu) (FIG. 6A). In the visible light range, the transmittance of the graphene film grown on a 300-nm thick nickel film for 7 minutes is ~ 80%, which is similar to that found for previously prepared films. This transmittance value indicates that the average number of graphene layers is 6 to 10 since the transmittance of the individual graphene layers is ~ 2.3%. The transmittance can be increased to ~ 93% by further reducing the growth time and nickel thickness to produce a thinner graphene film (Figure 3). Ultraviolet / ozone etching (UV / ozone cleaner, 60 W, BioForce) is also useful in controlling the transmittance (FIG. 6A, top inset). Indium electrodes were deposited on each corner of the square to minimize contact resistance (Figure 6a, bottom inset). The minimum sheet resistance is ~ 280 ohms per square, which is ~ 30 times smaller than the lowest sheet resistance measured on the produced film. The value of the sheet resistance increases with ultraviolet / ozone treatment time and coincides with the decrease in the graphene layer (Fig. 6A).

For microelectronic response, the mobility of the graphene film is important. To measure the intrinsic mobility of the single-domain graphene samples, the graphene samples from the PDMS stamps were transferred to a 300 nm deep, doped silicon wafer with a thermally grown oxide layer. The single layer graphene samples were easily located on the substrate from the optical contrast and confirmed by Raman spectroscopy. Electron-beam lithography was used to make a multi-terminal device (Fig. 6B, bottom inset). Remarkably, the multi-terminal electrical measurement showed that the electron mobility was ~ 3,750 cm ² V ^-1 s ^-1 at a carrier density of ~ 5 × 10 ^-2 cm ^-2 (FIG. 6b). For the high magnetic field of 8.8 T, a half-integer quantum Hall effect corresponding to the single-layer graphene was observed (Fig. 6b), indicating that the quality of the CVD-grown graphene is excellent.

On a silicon substrate having a size of 5 cm x 5 cm, a 300 nm thick SiO ₂ layer and a 10 nm to 600 nm thick Ni layer were sequentially coated to form a graphene growth support.

This support was charged into the furnace of a quartz tube. First, to remove the oxide film on the surface of Ni and increase the grain size of the Ni catalyst, it was flowed at 900 ° C to 1100 ° C for 1 hour at H ₂ / Ar = 100/200 sccm. Then, the same temperature was maintained at a flow rate of CH ₄ / H ₂ / Ar = 50/65/200 sccm for 30 seconds to 20 minutes to prepare a graphene sheet having a thickness of 10 or less on the graphene growth support. Referring to FIG. 3, it can be seen that the number of graphene layers can be controlled by controlling the catalyst layer thickness and the reaction time. The shorter the reaction time and the thinner the catalyst layer, the greater the distribution of the single-layer graphene.

Thereafter, the sheet was cooled at a rate of 100 deg. C / minute while flowing Ar = 200 sccm to form a corrugated graphene sheet. Here, the graphene growth support has a thermal expansion coefficient of 1.4 x 10 < ^-5 > / K and the graphene has a thermal expansion coefficient of 0.5 to 0.75 x 10 < ^-5 > / K.

The obtained sample can be expressed as a Si / SiO ₂ / Ni / graphene sheet. This Si / SiO ₂ / Ni / graphene sheet sample was immersed in a water bath containing an aqueous 1M FeCl ₃ solution to etch Ni. Of course, instead of direct etching of Ni as described above, SiO ₂ is etched first and then Ni is etched. For reference, SiO ₂ etching has a relatively longer etching time than Ni etching.

Ni was etched and the graphen sheet was separated. Since the graphene sheet is hydrophobic, it floated on the FeCl ₃ aqueous solution. The graphene sheet was transferred to a separate substrate and then taken out of the water tank to recover the graphene sheet. The recovered graphene sheet was formed with wrinkles having a height of 50 nm to 70 nm and a width of 70 nm to 100 nm. For reference, the height and width of the wrinkles were measured by AFM (Atomic Force Microscopy). The same is true for the following embodiments.

In order to confirm that the wrinkle height and width can be controlled by adjusting the cooling rate, the same procedure as in Example 2 was carried out except that the cooling rate was changed to 200 ° C./min. As a result, the height and width of the wrinkles were changed from 90 nm to 120 nm and from 50 nm to 70 nm, respectively.

In order to confirm that the wrinkle height and width can be adjusted by controlling the thickness of the graphene sheet, the graphene sheet was manufactured in the same manner as in Example 2 except that the thickness of the graphene sheet was changed to 20 layers. As a result, the height and width of the wrinkles varied from 30 nm to 50 nm and from 100 nm to 120 nm, respectively.

In Example 2, the graphene sheet was transferred to a separate substrate and taken out from the water tank, and then the graphene sheet on the substrate was transferred to a polydimethylsiloxane (PDMS) substrate as an elongated elastic substrate. The elastic substrate was originally 4 cm x 4 cm and extended in the uniaxial direction to have a length of 4 cm x 5 cm. Here it is also possible to use a method of directly transferring the case of using the elastomer substrate, for example a polydimethylsiloxane (PDMS) substrate stretching having a hydrophobic surface properties to emerge graphene sheet with FeCl ₃ aqueous solution surface in the elastic surface of the substrate from FeCl ₃ aqueous solution surface .

After the graphene sheet was transferred, the elastic substrate was shrunk to 4 cm x 4 cm. Equipment capable of stretching and compressing the elastic substrate was directly manufactured to shrink the elastic substrate.

The graphene sheet thus obtained exhibited a wave or buckle-like profile repeatedly rising and falling on the elastic substrate in the uniaxial direction. Here, the formed wave or buckle has a height of 1 占 퐉 to 10 占 퐉 and a width of 1 占 퐉 to 30 占 퐉.

The same procedure as in Example 5 was carried out except that the elastic substrate was originally stretched so as to have 5 cm x 5 cm by biaxially stretching the original substrate 4 cm x 4 cm by 1 cm. After the graft sheet was transferred, the elastic substrate was shrunk again to make 4 cm x 4 cm.

The graphene sheet thus obtained exhibited a wave or buckle-like profile repeatedly rising and falling on the elastic substrate in the biaxial direction. The wave or buckle formed here also had a height of 1 탆 to 10 탆 and a width of 1 탆 to 30 탆.

[Experiment]

The graphene sheet of Example 2 was transferred onto a polydimethylsiloxane substrate as an elastic substrate. In the case of Examples 5 and 6, since the elastic substrate was bonded to the graphene sheet, the same was used. These are referred to as modified water-soluble substances according to the respective examples.

The deformable water-soluble substance of Example 2 was placed in a bending apparatus manufactured directly and the resistance value according to bending was measured. In addition, the resistance values according to the stretching ratios were measured while being drawn into a compression or stretching machine which was produced directly for Examples 1, 4 and 5, and stretched. For reference, the elongation was measured by measuring the ratio of the elongated length to the original length, and the resistance value was measured using a 4-probe device.

11 is a graph showing resistance changes (Rx, Ry) along each axis (x, y axis) when the deformable water-soluble substance according to the second embodiment is bent and deformed in the uniaxial (y axis) direction. The X-axis of the graph represents the bending radius (mm), which is the radius of the curved portion when bending the deformable water-soluble material, and the Y-axis represents the resistance (kΩ).

Referring to FIG. 11, when the bending radius is 3.5 mm, there is not much difference in resistance. The resistance slightly increased at 2.3 mm bending radius, and increased to 0.8 mm and then returned to original resistance when re-expanded.

12 is a graph showing changes in resistance along the y-axis while stretching the water-soluble substance according to the second embodiment in a single axis (y-axis) direction. The X-axis of the graph represents the stretching ratio (%) and the Y-axis represents the resistance (kΩ). Referring to Fig. 12, it can be seen that the resistance value is reversibly restored when the stretching strain is restored from the stretching strain when the stretch strain ratio is up to 5%.

13 is a graph showing changes in resistance along the y-axis while stretching the deformable water-soluble substance according to the fifth embodiment in the uniaxial (y-axis) direction. The X-axis of the graph represents the stretching ratio (%) and the Y-axis represents the resistance (kΩ). Referring to FIG. 13, even when the elongation reaches 14%, the change in resistance value is small. When the elongation was increased to 21%, the resistance value slightly increased. However, when the elongation was recovered from the elongation, the resistance value returned to the original value.

14 is a graph showing resistance changes (Rx, Ry) of each axis (x, y axis) when the deformable water-soluble substance according to the sixth embodiment is stretched in two axes (x and y axes). The X-axis of the graph represents the stretching ratio (%) and the Y-axis represents the resistance (Ω). Referring to FIG. 14, it can be seen that the change in the resistance value is not large even when the stretching ratio of Rx as well as Ry is 10% or less and the resistance value is not more than 10%. It is also understood that even when the elongation strain rate reaches 30%, the change of the resistance value is not so large.

In FIG. 3, a is an optical microscope photograph of the graphene film according to the reaction time and the catalyst thickness. As the catalyst thickness is thinner and the reaction time is shorter, thinner graphenes are formed. b is an optical micrograph showing a very large grain size of 100 mu m or more after the graphene grown under the optimal conditions. c is a comparison of the number of graphene layers grown under conditions of different reaction times and catalyst thicknesses. The thinner the catalyst and the shorter the reaction time, the wider the area of the single graphene grains.

It will be understood by those of ordinary skill in the art that the foregoing description of the embodiments is for illustrative purposes and that those skilled in the art can easily modify the invention without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

10: substrate
20: sacrificial layer
30: Metal catalyst thin film for growth of graphene
40: carbon layer
50: graphene film (or sheet)
51: Deformation of ribbon shape Water-soluble graphene sheet
52: Shrinkage of deformed ribbon shape Water soluble graphene sheet
53: sheet-like deformation water-soluble graphene film
54: shrunk sheet-like deformation water-soluble graphene film
60: Stamp
70: target substrate
80: elastomer
81: Platelet-like elastic body stretched in one axis
82: Plate-shaped elastic body drawn in two axes
83: shrinked plate-shaped elastic body
100: substrate

Claims (1)

A method for producing a graphene sheet comprising growing the graphene on the support by providing a reaction gas containing a carbon source and heat to the graphene growth support comprising a metal catalyst thin film for graphene growth.

Images