KR20170043472A - Low-temperature transfer method of graphene - Google Patents

Abstract

The present invention relates to a method for producing a substrate to which a graphene thin film having a clean surface free from polymer residue is transferred by using a polymer-mediated graphene transfer process; a method for removing a polymer from a graphene surface without residue; a method for forming a polymer pattern on graphene; a method for fixing a polymer layer on graphene so that a polymer layer may not be removed during the treatment with an organic solvent; and an electric/electronic device comprising a substrate to which a graphene thin film having a clean surface free from polymer residue is transferred. According to the present invention, the metal surface state of a metal-containing layer which increases the surface energy of a graphene thin film on the metal-containing layer is determined, and then conditions for changing the metal-containing layer into the thus determined metal surface state are determined.

Description

{LOW-TEMPERATURE TRANSFER METHOD OF GRAPHENE}

The present invention relates to a method for producing a substrate on which a graphene thin film having a clean surface without a polymer residue is transferred by using a polymer-mediated graphen transcription method; A method of removing a polymer from a graphene surface without a residue; A method of forming a graphene polymer pattern; A method of fixing the polymer layer on the graphene so that the polymer layer is not removed during the organic solvent treatment; And a substrate on which a graphene thin film having a clean surface without a polymer residue is transferred.

Graphene and other two-dimensional transition metal dichalcogenide (TMDC) materials have received considerable interest in recent years in terms of high specific surface area, chemical stability, mechanical strength, flexibility and high electrical conductivity.

In particular, graphene is a transparent conductive material with a layer thickness of atoms, with the carbon atoms forming a hexagonal arrangement. Graphene is not only very structurally and chemically stable, it is also a material that has received the Nobel Prize in 2010 due to its outstanding optical, electrical and mechanical properties and is now attracting much attention. Graphene has many possibilities in electricity, display and energy devices because it has an atomic-size thickness and is an ideal two-dimensional material. In particular, graphene has a very high light transmittance in visible light and is also attracting much attention as a transparent electrode that can be turned because it can be wheeled.

Polymers acting as support layers of polymethacrylate metal (PMMA), polystyrene (PS), photoresist (PR) and the like must be surely used in the graphene transfer process to apply such grafts need. In addition, there is a need for a process to remove the polymer that acts as a support layer from graphene.

Conventionally, graphene-coated polymers are removed using organic solvents such as acetic acid, acetone, and chloroform. However, unlike a general bulk polymer, a polymer with a thin molecular film, which is in contact with graphene, was not easily dissolved in the organic solvent and thus was difficult to remove. For this reason, in the prior art, many attempts have been made to remove graphene-coated polymers by post-treatment through heat treatment at a temperature of 200 ° C or higher in hydrogen or a vacuum atmosphere for several tens of minutes or more.

However, the post-treatment process through such heat treatment is not only costly but also incompatible with the substrate of the flexible device, which is the direction in which the technology will be developed in the future. This is because the substrate (PS, PE, PU, etc.) generally used in the manufacturing process of the flexible device is carried out at a temperature near 300 ° C., which is higher than the melting point and the glass transition temperature.

JP 2013-530124 A

It is an object of the present invention to provide a graphene transfer method that does not leave a polymer residue on graphene even by a general polymer removal method without any additional post-treatment such as heat treatment.

A first aspect of the present invention is a method for producing a substrate on which a graphene thin film having a clean surface without a polymer residue is transferred using a polymer-mediated graphene transfer process, comprising the steps of: Graphene thin film; And a polymer layer; A second step of removing the metal-containing layer under a low-temperature condition in which the surface energy of the graphene thin film on the metal-containing layer (upper) is increased and the metal-containing layer is prevented from changing to a metal surface state; And a third step of transferring the complex containing the metal-containing layer to the substrate, and then removing the polymer, wherein the graft film and the polymer layer are removed. .

A second aspect of the present invention is a method for removing a polymer from a graphene surface without residues, comprising the steps of: Graphene thin film; And a polymer layer; Determining a metal surface state of the metal-containing layer that increases the surface energy of the graphene thin film on the metal-containing layer, and determining a condition that the metal-containing layer does not change in the determined metal surface state; Until the polymer layer is completely removed, under the conditions determined in the previous step, a metal-containing layer; Graphene thin film; And maintaining a complex comprising the polymer layer; And removing the polymer layer. The present invention also provides a method for removing graphene polymer.

In a third aspect of the present invention, there is provided a method for forming a graphene polymer pattern, comprising: sequentially forming a metal-containing layer; Graphene thin film; And a step of forming a composite having a polymer layer; (B) treating the composite under conditions that change the surface state of the metal-containing layer to increase the surface energy of the graphene thin film on the metal-containing layer; And a step C for forming a polymer pattern on the graphene by removing a part of the polymer layer, wherein a metal-containing layer is formed in the composite in the pattern corresponding to the polymer pattern, or a metal- The polymer layer corresponding to the polymer pattern is fixed on the graphene by changing the state of the metal surface to increase the surface energy of the graphene thin film to form a polymer pattern on the graphene when the polymer layer is removed in Step C The present invention also provides a method for forming a graphene-based polymer pattern.

In a fourth aspect of the present invention, there is provided a method of fixing a polymer layer on a graphene so that a polymer layer is not removed during an organic solvent treatment, Graphene thin film; And a polymer layer; Determining a metal surface state of the metal-containing layer that increases the surface energy of the graphene thin film on the metal-containing layer, and determining a condition for changing the metal-containing layer to the determined metal surface state; And a metal-containing layer under conditions that change the metal-containing layer to a metal surface state determined in a previous step; Graphene thin film; And a step of fixing the polymer layer on the graphene by treating the composite with the polymer layer.

A fifth aspect of the present invention provides an electric / electronic device comprising a base material onto which a graphene thin film is transferred, produced according to the first aspect.

Hereinafter, the present invention will be described in detail.

So far, despite extensive research into graphene, important polymers (such as PMMA) have been reported to be used when graphene is used in a variety of applications involving polymer-mediated transfers or polymer coatings for patterning, - There is very little reporting of graphene interaction.

Despite the fact that graphene in theory does not form any chemical bonds because it is inert, from many experimental results it is well known that polymer residues that can not be removed with solvents are clearly present in these systems. Despite many studies to address these problems, little effort has been made to identify the cause.

The present invention has identified the main contributors to the polymer adsorption from the PMMA / graphene / copper structure to the graphene phase.

Generally, a method of transferring graphene from a copper foil to a substrate is performed in three steps; i) a spin-coating step, ii) an annealing step, iii) a copper etching and cleaning step. If PMMA binds to graphene in the spin-coating step, it can be thought that this is due to strong interaction between PMMA and graphene. However, in Example 1, the irrelevance of the first spin-coating step was confirmed. On the other hand, if the annealing step and the etching step lead to polymer adsorption, respectively, it is thought to be due to thermal energy and copper etching related processes. Through Examples 2 and 3, it was found that the conditions of the annealing step and the etching step were the main factors that could cause polymer residue problems on the graphene surface. In particular, it has been found that, despite not annealing the PMMA / graphene / Cu foil system, there is still residue in the copper etching and cleaning steps.

As a result of the study, the present inventors have found that the physical and / or chemical state of the copper surface under graphene plays a crucial role in binding PMMA to graphene. The copper surface etched at room temperature not only physically differs from the etched copper surface at low temperatures, but also has a chemically different composition. In short, it has been found that such physical states (surface roughness) and / or chemical states (oxidation state of copper or defective states of the surface) induce the adsorption of the polymer, and such defects of copper are a major factor.

Based on the surprising discovery that the metal material induces or changes interactions such as polymer adsorption on the graphene adjacent to the top of the metal depending on the state of the metal surface, the present invention can induce or change the interaction of the graphene and the polymer The metal surface state of the metal-containing layer is determined, and processing conditions suitable for each process step are determined so as to change, maintain or suppress the metal surface state.

The present invention is also characterized in that it has been found that the surface state of the metal-containing layer under graphene can control the upper surface energy of the graphene.

In addition, the present invention relates to a metal-containing layer capable of inducing or changing the interaction between graphene and a corresponding polymer, by changing the surface energy of the metal-containing layer (upper) But can be determined from surface energy increase.

Surface energy is an intrinsic property of the interface that the interface between all materials has. When the surface energy is higher, the reactivity is high. This high surface energy means that the surface is unstable, reducing the surface area or increasing the tendency to contact other surfaces.

The surface energy of the solid can be measured by measuring the contact angle of the droplet. For example, a change in surface energy can be measured by a change in the water contact angle. A hydrophilic surface means a surface on which water spreads well on the surface.

Further, in the present invention, adsorption of the polymer on the graphene can be suppressed or the polymer can be fixed using the above-identified metal surface state and treatment conditions. For example, Cu surface roughness and defect states are main factors for determining the degree of PMMA adsorption on graphenes, and thus, in the present invention, the etching rate is lowered to suppress the adsorption of the polymer. This can be achieved by lowering the temperature of the system performing the etching process in the chiller (FIG. 8). Therefore, the present invention has made use of this discovery to design a graft transfer process free of PMMA residues by executing an "ice etching method" or an "ice transfer method.

The ice transfer method developed by the present invention can be applied to various substrates irrespective of the type and structure of the substrate, and an example in which graphene is transferred to a substrate which is not general in FIG. 5 is shown. The AAO template is a typical example of a substrate that can not withstand annealing at temperatures higher than 300 DEG C and has a high aspect ratio structure with a large minimum width of feature size. Prior approaches to removing polymers from graphene surfaces have two approaches, such as thermal annealing and mechanical cleaning steps. However, due to the low glass transition temperature, it is difficult to perform thermal annealing on polymeric substrates such as PET, and nanostructured or high contrast substrates such as AAO essentially make it difficult to use mechanical cleaning methods. In recent years, although a transfer method such as an electrostatic technique or a press method which does not require a polymer protective film has been developed, a transfer method using a polymeric protective film is also necessary.

Accordingly, another feature of the present invention is to remove the metal-containing layer under low temperature conditions that inhibit the physical / chemical state of the metal-containing layer which increases the surface energy of the (upper) graphene film on the metal-containing layer. At this time, the low-temperature condition may be 4 ° C or lower and higher than the freezing point of the solution for removing the metal-containing layer.

< Grapina  Polymer removal without residue from surface>

According to the present invention, there is provided a method for producing a substrate on which a graphene thin film having a clean surface without polymer residue is transferred by using a polymer-mediated graphene transfer method

A metal-containing layer; Graphene thin film; And a polymer layer;

A second step of removing the metal-containing layer under a low-temperature condition in which the surface energy of the graphene thin film on the metal-containing layer (upper) is increased and the metal-containing layer is prevented from changing to a metal surface state; And

And a third step of transferring the complex having the thin film and the polymer layer from which the metal-containing layer has been removed to a substrate and then removing the polymer.

The first step is to change the metal oxide state of the metal-containing layer which increases the surface energy of the upper (upper) graphene thin film on the surface of the graphene thin film formed on the metal-containing layer Forming a polymer layer under a low-temperature condition in which the metal-containing layer; Graphene thin film; Containing layer that increases the surface energy of the (upper) graphene thin film on the metal-containing layer (s) with respect to the composite comprising the polymeric layer and the polymer layer.

Meanwhile, according to the present invention, a method of removing a polymer from a graphene surface without residues

A metal-containing layer; Graphene thin film; And a polymer layer;

Determining a metal surface state of the metal-containing layer that increases the surface energy of the graphene thin film on the metal-containing layer, and determining a condition that the metal-containing layer does not change to the determined metal oxide state;

Until the polymer layer is completely removed, under the conditions determined in the previous step, a metal-containing layer; Graphene thin film; And maintaining a complex comprising the polymer layer; And

And removing the polymer layer.

The conditions may include not only the temperature condition but also the kind of reactants such as process speed and oxidizing agent.

At this time, the step of maintaining the composite may include: providing a metal-containing layer in the determined condition; Graphene thin film; And removing the metal-containing layer from the composite having the polymer layer.

Further, after the step of removing the polymer layer, a metal-containing layer; And removing the metal-containing layer from the composite having the graphene thin film.

The metallic surface state of the metal-containing layer, for example, the surface roughness, which increases the surface energy of the graphene thin film on the metal-containing layer (upper), closely matches the surface roughness range or surface roughness The range of the roughness which can not be determined can be determined in consideration of the case where the radius of curvature of the section where the strain applied to the graphene is saturated is the maximum value.

In the present invention, when the metal-containing layer is a copper foil, the surface of the copper that increases the surface energy of the graphene thin film on the copper foil has defects or bends that apply strain to the graphene.

When the metal-containing layer is a copper foil, the surface state of copper which increases the surface energy between the copper foil and the graphene thin film may have a roughness of 10 nanometers or more, preferably 500 nanometers or more (FIG. On the other hand, the metal-containing layer is a copper foil, and the surface state of copper, which interferes with adsorption of polymers and other organic substances, is independent of the graphene film on the copper foil (graphene is not attached to the bottom) The surface roughness can be about 5-10 nanometers.

An example of copper defects is the oxidation state of copper, such as Cu ^II . Cu ^I less affects the surface energy of graphene.

Various defects of the metal which cause the surface of the metal to change the surface of the graphene so that the organic material adheres to the surface of the graphene more easily. For example, the very rough metal surface or the metal surface including the heteroelement, Which may be an energy-unstable surface compared to the metal surface of the metal.

Graphene can be synthesized and patterned in a relatively simple manner while having excellent stretchability, flexibility and transparency.

A good graphene can be obtained by removing graphene from graphite using a tape. Also, graphite oxide can be dispersed in a solvent such as water using a strong acid to form a graphene sheet. In addition, a large amount of high quality graphene can be synthesized by a chemical vapor deposition (CVD) method in which graphene is synthesized in a vapor phase using a catalyst such as copper (Cu) or nickel (Ni).

As used herein, a "graphene thin film" is one in which a plurality of carbon atoms are covalently linked to one another to form a polycyclic aromatic molecule, wherein the graphene forms a layer or sheet form. The carbon atoms linked by the covalent bond may form a 6-membered ring as a basic repeating unit, but may further include a 5-membered ring and / or a 7-membered ring. Thus, the graphene thin film appears as a single layer of covalently bonded carbon atoms (usually sp2 bonds) to each other. The graphene thin film may have various structures, and such a structure may vary depending on the content of the 5-membered ring and / or the 7-membered ring which may be contained in the graphene. The graphene thin film may be formed of a single layer of graphene, but they may be stacked to form a plurality of layers.

Further, the graphene thin film may be a single layer or multilayer graphene or graphite oxide such as graphene laminated graphite, single layer graphene, multilayer graphene, graphene oxide, graphite oxide, etc., graphene fluoride, Graphene having a functional group such as sulfone group (SO ₃ H), graphene functional group or its reduced product, graphene or graphite prepared through synthesis, graphene peeled off from expanded graphite or the like, graphene or graphite Low molecular weight, high molecular weight graphene or graphite, silver (Au) particles such as a two-dimensional carbon isotope, didodecyldimethylammonium bromide graphene, phenylisocyanate graphite oxide, alkylaminated graphene, , Platinum (Pt), palladium (Pd), and the like, and graphene Can be included.

Examples of the method of forming the graphene thin film include a mechanical peeling method, a chemical peeling method, a chemical vapor deposition method, an epitaxy synthesis method, an organic synthesis method, etc. Preferably, the graphene thin film is grown by chemical vapor deposition It can be a pin.

On the other hand, the metal-containing layer serves as a graphene formation catalyst, and graphene can be synthesized on the metal-containing layer. That is, the metal-containing layer may be a metal catalyst layer for growing graphene. Wherein the metal catalyst layer for graphene growth comprises at least one of Ni, Co, Fe, Pt, Au, Al, Cr, Cu, Mg, Mn, Rh, Si, Ta, Ti, W, U, V, Zr, Fe, Brass, Bronze, stainless steel, Ge, or a combination thereof.

Non-limiting examples of carbon sources for use in forming graphene on a metal catalyst layer for graphene growth include carbon monoxide, carbon dioxide, methane, ethane, ethylene, ethanol, acetylene, propane, propylene, butane, butylene, butadiene, pentane, , Pentene, pentadiene, cyclopentane, cyclopentadiene, hexane, hexene, cyclohexane, cyclohexadiene, benzene, toluene, and combinations thereof.

The metal catalyst layer for graphene growth helps to form a hexagonal plate-like structure by bonding carbon components provided from a carbon source by contacting with a carbon source.

When forming a metal-containing layer on a substrate, in particular, a metal catalyst layer for graphen growth, various deposition methods known in the art can be used, for example, electron-beam evaporation, thermal evaporation, sputtering and the like. If the substrate is a metal foil, it is not necessary to further form the metal-containing layer on the substrate. In the case of a metal foil for a graphene growth catalyst, graphene can be directly formed on the substrate. Non-limiting examples of the metal foil may be aluminum foil, zinc foil, copper foil, nickel foil, ruthenium foil, gold foil or platinum foil. The thickness of the metal foil may be 0.1 to 100 탆.

The metal-containing layer in the composite can be a thin film or a thick film, for example, if it is a thin film, its thickness can be from about 1 nm to about 1000 nm, or from about 1 nm to about 500 nm, or from about 1 nm to about 300 nm And, in the case of a thick film, its thickness may be from about 1 mm to about 5 mm.

The thickness of the graphene thin film may be about 1 to about 300, but is not limited thereto.

The thickness of the metal-containing layer is preferably 0.1 to 10 mu m. If it is less than 0.1 탆, graphene growth can not be smoothly performed, and if it is more than 10 탆, it may take a lot of time and cost for a subsequent metal etching process.

The polymer used in the polymer-mediated graphene transfer method according to the present invention is coated on the graphene thin film to serve to support the graphene thin film when the metal-containing layer is removed, and the mechanical strength Can be reinforced.

Thus, non-limiting examples of polymers used in the polymer-mediated graphene transcription method include polydimethylsiloxane (PDMS), polymethyl methacrylate (PMMS), polymethacrylate metal (PMMA) ), Polystyrene (PS), photoresist (PR), and polycarbonate (PC).

In the present invention, the polymer used for the polymer layer may be a polymer compound having? -Electrons. The sp ² electrons of the graphene can be bonded to the polymer layer by an attractive force (e.g., van der Waals force) with? -Electrons present on the surface of the polymer layer. Non-limiting examples include polyacrylate, polyethylene etherphthalate, polyethylene phthalate, polyethylene naphthalate, polybuthylene phthalate, polycarbonate, For example, polystyrene, polyether imide, polyether sulfone, polydimethyl siloxane (PDMS), polyimide, and combinations thereof.

Non-limiting examples of the method of forming the polymer layer on the graphene thin film include a dropping coating method, a spin coating method, a low temperature vapor deposition method, a method of filling in a sandwich cell, a doctor blade, A paint brushing method, a spray coating method, and a dip coating method.

The thickness of the polymer layer may be less than 200 nm to be as thin as possible so as not to apply physical pressure to the graphene with a thickness of more than 50 nm so as to have mechanical stability.

In the present invention, after the formation of the polymer layer on the graphene thin film, the high-temperature annealing which causes the change of the metal surface state of the metal-containing layer which increases the surface energy of the graphene thin film on the metal- .

The present invention removes the metal-containing layer under a low-temperature condition that suppresses the change of the surface state of the metal-containing layer for increasing the surface energy of the (upper) graphene film on the metal-containing layer.

The low-temperature condition may be 4 ° C or lower, preferably 0 ° C or lower, or higher than the freezing point of the solution for removing the metal-containing layer.

The metal containing layer may be removed by an etching process using an etching solution comprising an acid, a salt, FeCl _3, or a combination thereof. The metal etching solution should be a solution that does not freeze at low temperatures, and thus may contain an antifreeze such as ethylene glycol in a water-based solution.

According to the third step of the present invention, when the complex containing the metal-containing layer and the polymer layer is transferred onto the substrate, the substrate to be used at this time may be selected and used without limitation, A silicon substrate for a semiconductor, a flexible plastic substrate for an electrode, a transparent glass substrate, or the like. The substrate may have transparency, flexibility, or both.

Non-limiting examples of the polymer removing solution that can be used in removing the polymer after transferring the composite including the graphene thin film and the polymer layer from which the metal containing layer has been removed to the substrate may be acetic acid, acetone, or chloroform.

6 to 8, the graphene transferring method of the present invention will be described step by step. A graphene 2 is formed on the top of the metal foil 1 through chemical vapor deposition. The polymer 3 is coated on the graphene 2 (S10). The metal foil 1 is etched (S11) by immersing the formed composite foil 1 / graphene 2 / polymer 3 composite film in a metal etching solution at 4 ° C or lower. After the metal foil 1 is etched, the composite membrane of the graphene 2 / polymer 3 is transferred to the desired substrate 4 and the polymer 3 is dissolved (S12).

< Grapina  An electric / electronic element comprising a substrate onto which a thin film is transferred>

The present invention provides an electrical and electronic element comprising a graphene transferred substrate produced by the transfer method of the present invention.

Non-limiting examples of the electric / electronic device may include all electric / electronic devices including a semiconductor device, a display, a solar cell, a battery, a sensor, and an electrode.

According to the present invention, a substrate on which a graphene thin film having a clean surface without a polymer residue is transferred can be used for various purposes. It can be used as a transparent electrode due to its excellent conductivity and transparency.

In particular, a substrate onto which a graphene thin film is transferred can be synthesized and patterned in a relatively simple manner with excellent electrical properties, mechanical properties, and optical characteristics as well as excellent stretchability, flexibility, transparency, and easy bending properties So it can be used throughout the next generation of flexible electronics industry technology.

In addition, when used as a panel conductive thin film of various display elements or the like, the desired conductivity can be exhibited even in a small amount, and the light transmission amount can be improved.

In addition, when the substrate on which the graphene thin film is transferred is formed into a tube shape, it can be used as an optical fiber and can be used as a membrane that selectively permeates a hydrogen storage material or hydrogen.

< Grapina  Prize Polymer layer  Fixation and Polymer Pattern Formation>

The discovery that induce or change interactions such as polymer adsorption on the graphene adjacent to the upper part of the metal surface depending on the state of the metal surface can be applied to the formation of graphene polymer layer and polymer pattern formation.

Therefore, the method of fixing the polymer layer on the graphene so that the polymer layer is not removed during the organic solvent treatment according to the present invention

A metal-containing layer; Graphene thin film; And a polymer layer;

Determining a metal surface state of the metal-containing layer that increases the surface energy of the graphene thin film on the metal-containing layer, and determining a condition for changing the metal-containing layer to the determined metal surface state; And

A metal-containing layer under the condition of changing the metal-containing layer to the metal surface state determined in the previous step; Graphene thin film; And fixing the polymer layer on the graphene by treating the composite having the polymer layer; And

Optionally, after the step of fixing the graphene polymer layer, a metal-containing layer; Graphene thin film; And removing the metal-containing layer from the composite having the polymer layer.

According to another aspect of the present invention, there is provided a method of forming a graphene polymer pattern,

A metal-containing layer; Graphene thin film; And a step of forming a composite having a polymer layer;

(B) treating the composite under conditions that change the surface state of the metal-containing layer to increase the surface energy of the graphene thin film on the metal-containing layer; And

And a step (C) of removing a part of the polymer layer to form a polymer pattern on the graphene,

A metal-containing layer is formed in the composite in a pattern corresponding to the polymer pattern,

The polymer layer corresponding to the polymer pattern is fixed on the graphene by changing the state of the metal surface to increase the surface energy of the graphene thin film only in the metal containing layer corresponding to the polymer pattern, And a polymer pattern is formed on the signal graphene.

When the metal-containing layer is a copper foil, a copper foil and yes surface conditions of the copper to increase the surface energy between the pin thin film is 10 nm or larger, preferably 500 nm defects on the branches or surface meters or more roughness (Cu ^II ) Is a large number.

According to the graphene low-temperature transfer method of the present invention, graphene low-temperature transfer process technology can be used to secure the source transfer technology of graphene, which is a spotlight in next-generation transparent electrode materials, The pin can be obtained.

FIG. 1 shows AFM images and XPS analysis results of a graphene / Cu foil after application and removal of a PMMA film in Examples 1 and 2. FIG.
FIG. 2 shows changes in the surface energy (contact angle) according to the heat treatment temperature, the distribution of the PMMA residues on the surface according to the heat treatment temperature (b), and the size of the PMMA particles according to the heat treatment temperature.
3 shows the AFM image and XPS analysis results of the graphene surface on the SiO ₂ substrate according to Example 3. FIG.
4 is a scatter plot of Raman peak parameters of the graphene thin film according to Example 3. FIG.
FIG. 5 (a) is a schematic view of graphene transferred onto an AAO template, and FIG. 5 (b) is an SEM image of a graphene sheet transferred on an AAO substrate by ice transfer according to Example 4. Figures 5 (c) and 5 (d) compare AFM surface topology images of graphene sheets transferred by ice transfer and conventional transfer onto these substrates.
6 is a schematic view of a graphene low temperature transfer process according to one embodiment of the present invention.
7 is a flowchart showing a graphene low temperature transfer process according to one embodiment of the present invention.
8 is a photograph of a graphene low temperature transfer process according to one embodiment of the present invention.

Hereinafter, the present invention will be described in more detail with reference to the following examples and experimental examples. However, the following Examples and Experimental Examples are for illustrating the present invention, and the scope of the present invention is not limited by the following Examples and Experimental Examples.

< Example  1>

On a Cu foil (46986, made by Alfa aeser, based on 99.8% metal) with a length and a length of 6 cm and a thickness of 25 μm using a methane precursor by low pressure chemical vapor deposition (LPCVD) Film was synthesized. After growth, the PMMA film was spin-coated at 4000 ppm and coated on a graphene / Cu foil. The PMMA / graphene / Cu foil was placed in an acetone solution and the PMMA film was removed at room temperature for 15 minutes.

Figure 1 (a) is an AFM image of a graphene / Cu foil after application and removal of the PMMA film, showing a very clean surface, indicating that the graphene surface is chemically stable. As a result of XPS analysis on the same sample, the sp3 carbon peak profile was similar to the pristine sample before application of the PMMA film (Fig. 1 (g) and (i)). These results clearly show that PMMA residues normally found on graphene surfaces are derived by other factors, not by simple spin coating of graphene external material.

< Example  2>

The PMMA / graphene / Cu foil prepared in the same manner as in Example 1 was heated at a temperature of 50 ° C in the range of 70 ° C to 270 ° C for 15 minutes, and then the PMMA was removed using acetone.

As shown in FIGS. 1 (b) to 1 (f), at temperatures above 170 ° C., the residue species appearing as falsely colored violet on the Cu surface gradually increase. The C 1s peak profile of these regions showed significant deviations from the clean graphene, with a significant change in the typical binding energy (~ eV) of PMMA. Also interestingly, the Cu oxidation state in these regions was mainly Cu ^II , with binding energies centered at 933.8 eV, as was the case for CuO, Cu (OH) ₂ and Cu (COOH) ₂ . As the number of sites with Cu ^II oxidation state increased, the amount of PMMA adsorbed on graphene also increased. The surface energy of the graphene / Cu foil gradually increased from a low temperature to a high temperature to form a relatively hydrophilic surface (Fig. 2 (a)). This tendency is mainly due to the fact that as the temperature is increased, both the density and the diameter of the oxide nanoparticles increase as shown in Figs. 2 (b) and 2 (c). Therefore, the method of avoiding PMMA bonding is to prevent the annealing temperature from exceeding 120 캜.

< Example  3>

The PMMA / graphene / Cu foil prepared in the same manner as in Example 1 was subjected to a copper etching and cleaning step at room temperature without annealing, and then the PMMA / graphene was transferred onto the SiO ₂ substrate and then acetone was used To remove PMMA.

3 (a) and (b) using the intermediate transfer method PMMA- at room temperature for graphene / from the copper foil yes] After transferring the pin on the SiO ₂ base material substrate onto SiO ₂ Yes are AFM images of the pin surface. As shown in the figure, the rough surface still suggests that there is a large amount of PMMA residue on the graphene.

To determine what part of the Cu etching process is involved in this phenomenon, the Cu foil was etched for a short time (about 1 minute) and its surface was analyzed by SEM and XPS. As can be seen in FIG. 3 (c), which is an SEM image of the etched Cu surface, when the foil is dissolved in the etchant at room temperature, it forms a unique polyhedral microstructure which affects the surface roughness. Also, as shown in Figure 3 (d), as in the case of thermal annealing, according to the XPS results, the chemical state of these features was highly biased toward the Cu ^II state. These results suggest that PMMA residues can nucleate on graphene in a manner similar to thermal annealing when the chemical etching of the Cu foil occurs at room temperature during the transfer process.

The Cu surface state is a major factor in determining the adsorption rate of PMMA on graphene. Therefore, by lowering the temperature of the system for performing the etching process in the cooler, the etching rate was lowered to suppress the adsorption of the polymer.

According to thermovision images, the PMMA / graphene / copper foil was cooled to a low temperature of about -30 ° C in the cooler. Surprisingly, "ice etching method" a SiO ₂ phase graphene prepared using had a very clean surface (see Fig. 3 (e) and (f)). These results indicate that the Cu foil surface is relatively gentle at low temperatures and Cu ^II Can be explained by the absence of the oxidation state. According to the XPS profile, when the copper foil is etched in the chiller, Cu ^I The oxidation state is mainly developed (Fig. 3 (h)). More interestingly, the gloss and micro-morphology of the copper surface etched at room temperature and at low temperatures shows sharply different shapes as in Figs. 3 (c) and 3 (g).

Scatter plots of the Raman peak parameters of the graphene thin films respectively prepared by the conventional transfer method (etching at 25 캜) and the ice transfer method according to the present invention are shown in Figs. 4 (a) to (c). In the case of ice transfer, the observed dotted trend circle was small in size, indicating that the G and 2D Raman peaks independent of the data acquisition point are more uniform. Both the peak positions and the FWHMs in the ice-transferred graphene have a smaller deviation. As shown in Fig. 4 (a), the G peak and the 2D peak position are rather independent of the transfer method. In the case of the conventional transfer method, this deviation is larger, but the average peak positions agree well. In Figs. 4 (b) and 4 (c), in the case of the conventional transfer method, a wider G peak position range indicates n- or p-doping from the PMMA residue. This tendency is in good agreement with previous reports that Raman peaks on SiO ₂ substrates are wider than h-BN substrates due to charge fluctuations from electron-hole pools. Also, in the case of the graphene sheet transferred by the ice transfer method, the intensity of Raman peaks as well as peak positions and FWHM values have more uniform values as shown in Figs. 4 (d) and 4 (e) It is important. In other words, the ice transfer method of the present invention shows uniform graphene characteristics over the entire area since the graphene surface exhibits the characteristic of the graphene surface without the PMMA residue on the graphene surface, unlike the case of transferring at room temperature. On the other hand, there are various sizes and amounts of PMMA residues on the surface of graphene transferred at room temperature. Raman peaks with various distributions are observed because they distort the characteristics of graphene.

< Example 4 >

The graft-transferred AAO substrate was prepared by using the ice transfer method in the same manner as in Example 3, except that an AAO (anodic aluminum oxide) template was used instead of the SiO ₂ substrate.

5 (a) is a schematic diagram of graphene transferred onto an AAO template. FIG. 5 (b) is an SEM image of the AAO composed of nano-sized pores. Figures 5 (c) and 5 (d) compare AFM surface topology images of graphene sheets transferred by ice transfer and conventional transfer onto these substrates. As shown in the above image, the contamination degree between the two cases is remarkably contrasted. The graphene sheet transferred at low temperature shows a cleaner surface and even the folds formed in the layer can be observed due to the strain derived from the hole of the AAO template.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. I will understand. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

1: metal foil 2: graphene
3: polymer 4: substrate

Claims (20)

A method for producing a substrate on which a graphene thin film having a clean surface without a polymer residue is transferred by using a polymer-mediated graphene transfer method,
A metal-containing layer; Graphene thin film; And a polymer layer;
A second step of removing the metal-containing layer under a low-temperature condition in which the surface energy of the graphene thin film on the metal-containing layer (upper) is increased and the metal-containing layer is prevented from changing to a metal surface state; And
A third step of transferring the complex having the metal-containing layer to the substrate and removing the polymer,
Wherein the graphene thin film is transferred onto the substrate. The method of manufacturing a substrate according to claim 1, wherein the low-temperature condition in the second step is at most 4 ° C, and is at or above the freezing point of the solution for removing the metal-containing layer. The method according to claim 1, wherein the first step is a step of forming a metal-containing layer on the surface of the metal-containing layer, the metal-containing layer increasing the surface energy of the graphene thin film on the metal- Forming a polymer layer under a low-temperature condition for suppressing a change to a surface state; Graphene thin film; Containing layer for increasing the surface energy of the graphene thin film on the metal-containing layer (for the composite with the polymer layer), characterized in that the high-temperature annealing which causes the change to the metal surface state of the metal- And transferring the transferred substrate. The method of manufacturing a substrate according to claim 1, wherein the metal-containing layer is a metal catalyst layer for growing graphene. 5. The method of claim 4, wherein the metal catalyst layer for graphene growth is selected from the group consisting of Ni, Co, Fe, Pt, Au, Al, Cr, Cu, Mg, Mn, Rh, Si, Ta, Ti, W, Wherein the graphene film is selected from the group consisting of Fe, brass, bronze, stainless steel, Ge, and combinations thereof. The method of claim 1, wherein the metal-containing layer is a metal foil. The method of claim 1, wherein the metal-containing layer is a copper foil, and the oxidation state of copper which increases the surface energy of the graphene thin film on the copper foil is Cu ^II . The method of claim 1, wherein the metal-containing layer is a copper foil and the surface state of the copper for increasing the surface energy of the graphene thin film on the copper foil is an average surface roughness of 10 nm or more. Gt; The method of producing a substrate according to claim 1, wherein the substrate is selected from the group consisting of glass, polymer, semiconductor, metal, and mixtures thereof. The method of claim 1, wherein the substrate has transparency, flexibility, or both. The method for producing a substrate according to claim 1, wherein the second step uses a metal etching solution, and the third step uses a polymer removing solution for dissolving the polymer. A method for removing a polymer from a graphene surface without a residue,
A metal-containing layer; Graphene thin film; And a polymer layer;
Determining a metal surface state of the metal-containing layer that increases the surface energy of the graphene thin film on the metal-containing layer, and determining a condition that the metal-containing layer does not change in the determined metal surface state;
Until the polymer layer is completely removed, under the conditions determined in the previous step, a metal-containing layer; Graphene thin film; And maintaining a complex comprising the polymer layer; And
And removing the polymer layer. 13. The method of claim 12, wherein maintaining the composite comprises: providing a metal-containing layer in the determined condition; Graphene thin film; And removing the metal-containing layer from the composite having the polymer layer. 13. The method of claim 12, further comprising: after the polymer layer removal step, a metal-containing layer; And removing the metal-containing layer from the composite having the graphene thin film. In the method for forming a graphene polymer pattern,
A metal-containing layer; Graphene thin film; And a step of forming a composite having a polymer layer;
(B) treating the composite under conditions that change the surface state of the metal-containing layer to increase the surface energy of the graphene thin film on the metal-containing layer; And
And a step (C) of removing a part of the polymer layer to form a polymer pattern on the graphene,
A metal-containing layer is formed in the composite in a pattern corresponding to the polymer pattern,
The polymer layer corresponding to the polymer pattern is fixed on the graphene by changing the state of the metal surface to increase the surface energy of the graphene thin film only in the metal containing layer corresponding to the polymer pattern, Wherein the polymer pattern is formed on a graphene graphene. 16. The method according to claim 15, wherein the surface condition of the copper which increases the surface energy of the graphene thin film on the copper foil is copper foil of the metal-containing layer has an average surface roughness of 10 nanometers or more and the oxidation state of copper is Cu ^II Wherein the graphene-based polymer pattern is formed on the substrate. A method for fixing a polymer layer on a graphene layer so that a polymer layer is not removed during an organic solvent treatment,
A metal-containing layer; Graphene thin film; And a polymer layer;
Determining a metal surface state of the metal-containing layer that increases the surface energy of the graphene thin film on the metal-containing layer, and determining a condition for changing the metal-containing layer to the determined metal surface state; And
A metal-containing layer under the condition of changing the metal-containing layer to the metal surface state determined in the previous step; Graphene thin film; And a step of fixing the polymer layer on the graphene by processing the composite having the polymer layer. 18. The method of claim 17, further comprising: after the graphene polymer layer fixing step, a metal-containing layer; Graphene thin film; And removing the metal-containing layer from the composite having the polymer layer. An electric / electronic device comprising a base material onto which a graphene thin film is transferred, produced according to any one of claims 1 to 11. 20. The electrical and electronic device according to claim 19, wherein the substrate onto which the graphene thin film is transferred is a flexible electrode.

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