KR20130028582A - Method for getting graphene - Google Patents

Abstract

PURPOSE: A method of obtaining graphene is provided to prevent damage to the graphene, and to reduce the catalyst metal removal time by gradually removing catalyst metals. CONSTITUTION: A method of obtaining graphene comprises the following steps: forming the graphene on one surface of a catalyst metal(S110); forming a support on the surface of the graphene without the catalyst metal(S120); partially removing the catalyst metal by a wet-etching process using a first etching solution(S130); removing the rest of the catalyst metal by a wet-etching process using a second etching solution, and exposing the graphene(S140); and transmitting the exposed graphene to a target film(S160). [Reference numerals] (AA) Start; (BB) End; (S110) Forming graphene on one surface of a catalyst metal; (S120) Forming a support; (S130) Previously removing the catalyst metal; (S140) Finally removing the catalyst metal; (S150) Washing and drying; (S160) Transferring the graphene on a target film; (S170) Removing the support

Description

Method for obtaining graphene {Method for getting graphene}

The present invention relates to a method for obtaining graphene, and more particularly, to a method for obtaining graphene, which shortens the removal time of the catalyst metal.

Graphene is a material in which carbon is connected to each other in a hexagonal shape to form a honeycomb two-dimensional planar structure, and its thickness is very thin, transparent, and has a very high electrical conductivity. Many attempts have been made to apply graphene to a transparent display or a flexible display using this characteristic of graphene. As interest in graphene increases, a method for mass production of high quality graphene is required.

The graphene is synthesized on the catalytic metal, and then the catalytic metal must be removed to transfer the graphene. These catalyst metals are removed at one time using one etchant, which takes at least about 30 minutes to remove the catalyst metal. In addition, when an etchant having a strong removal ability is used to shorten the catalyst metal removal time, the graphene is damaged and thus the sheet resistance of the graphene is increased, and thus the electrical characteristics of the graphene are degraded.

One embodiment of the present invention is to provide a method for obtaining graphene that does not damage the graphene while reducing the catalyst metal removal time.

According to one aspect of the invention, the step of forming graphene on one surface of the catalyst metal; Forming a support on a surface of the graphene on which the catalyst metal is not disposed; A preliminary step of removing a portion of the catalyst metal by a wet etching process using a first etchant; A final removal step of exposing the graphene by removing the remaining catalyst metal by a wet etching process using a second etching solution; And transferring the exposed graphene to a target film. It provides a method for obtaining graphene comprising a.

According to another feature of the invention, the first etchant is a solution capable of removing the catalyst metal at a faster rate than the second etchant.

According to another feature of the invention, the first etchant is a solution of iron chloride (FeCl ₃ ) or persulfate type.

According to another feature of the invention, the first etchant is a solution of higher concentration than the second etchant.

According to another feature of the invention, the first etchant or the second etchant is iron chloride (FeCl ₃ ), iron nitrate (Fe (No ₃ ) ₃ ), copper chloride (CuCl ₂ ), ammonium persulfate ((NH ₄ ) ₂ S ₂ O ₈ ), at least one of sodium persulfate (Na ₂ S ₂ O ₈ ) solution and persulfate type solution.

According to another feature of the invention, the line removal step is characterized in that it is carried out a plurality of times.

According to another feature of the invention, when the pre-removal step is carried out a plurality of times, the type or concentration of the etchant used in each step is different.

According to another feature of the invention, the catalytic metal remaining in the pre-removal step is characterized in that 0.15% to 50% of the thickness of the initial catalyst metal.

According to another feature of the invention, the final removal step is characterized in that to remove the catalytic metal so that the sheet resistance of the graphene within the range of 10 Ohm / sq to 3000 Ohm / sq.

According to another feature of the present invention, the first etchant and the second etchant are supplied to the catalyst metal through any one of spray-type, bath-type, or a combination thereof.

According to another feature of the invention, the cleaning step of removing the first etchant and the second etchant remaining in the graphene after the final removal step; .

According to another feature of the invention, the catalyst metal is nickel (Ni), cobalt (Co), iron (Fe), platinum (Pt), gold (Au), aluminum (Al), chromium (Cr), copper (Cu ), Magnesium (Mg), manganese (Mn), rhodium (Rh), silicon (Si), tantalum (Ta), titanium (Ti), tungsten (W), uranium (U), vanadium (V), zirconium (Zr) and combinations thereof.

According to another feature of the invention, the graphene is made of a single layer or multiple layers.

According to another feature of the invention, the support is a thermal peeling film or polymer coating.

According to the method for obtaining graphene according to an aspect of the present invention, by removing the catalyst metal step by step, the catalyst metal removal time is shortened as compared with the prior art, and does not damage the graphene.

1 is a flow chart schematically showing a graphene transfer method according to an embodiment of the present invention.
2A to 2F are schematic side cross-sectional views of the graphene film corresponding to each step of FIG. 1.

Hereinafter, a method for obtaining graphene according to embodiments of the present invention will be described in detail with reference to the drawings.

1 is a flowchart schematically showing a graphene transfer method according to an embodiment of the present invention, Figures 2a to 2f is a schematic side cross-sectional view of the graphene film corresponding to each step of FIG. In the drawings, the thicknesses of the catalyst metal 301, the graphene 302, the support 303, and the target film 304 are exaggerated for convenience of description.

First, the graphene 302 forming process is performed (S110). In detail, as illustrated in FIG. 2A, graphene 302 is formed on at least one surface of the catalytic metal 301.

The catalytic metal 301 is nickel (Ni), cobalt (Co), iron (Fe), platinum (Pt), gold (Au), aluminum (Al), chromium (Cr), copper (Cu), magnesium (Mg) , Manganese (Mn), rhodium (Rh), silicon (Si), tantalum (Ta), titanium (Ti), tungsten (W), uranium (U), vanadium (V), zirconium (Zr) and their At least one selected from combinations.

In the present embodiment, the case where the catalyst metal 301 is a single layer has been described, but the present invention is not limited thereto.

Although not shown, a pretreatment process is performed to clean the surface of the catalyst metal before the graphene 302 is formed on the catalyst metal 301. The pretreatment process is to remove foreign substances present on the surface of the catalytic metal 301 and may use hydrogen gas. Alternatively, by cleaning the surface of the catalyst metal 301 using an acid / alkaline solution, defects may be reduced when the graphene 302 is formed, which is a subsequent process. The step of cleaning the surface of the catalytic metal 301 may be omitted as necessary.

After the pretreatment process, the catalytic metal 301 is transferred to the graphene formation space (for example, the chamber), the carbonaceous carbon source is added to the graphene formation space and heat treated. The heat treatment consists of heating and cooling. Chemical Vapor Deposition (CVD), Thermal Chemical Vapor Deposition (TCVD), Rapid Thermal Chemical Vapor Deposition (RTCVD), inductive coupling in the graphene formation process (S110). Various processes such as Inductive Coupled Plasma Chemical Vapor Deposition (ICP-CVD) and Atomic Layer Deposition (ATLD) may be used.

A carbon source of the vapor is methane (CH _4), carbon monoxide (CO), ethane (C ₂ H _6), ethylene (CH _2), ethanol (C ₂ H _5), acetylene (C ₂ H _2), propane (CH ₃ CH ₂ CH _3), propylene (C ₃ H _6), butane (C ₄ H _10), pentane _{(CH 3 (CH 2) 3} CH 3), pentene (C ₅ H _10), dicyclopentadiene (C ₅ H ₆ carbon atoms such as hexane (C ₆ H ₁₄ ), cyclohexane (C ₆ H ₁₂ ), benzene (C ₆ H ₆ ), and toluene (C ₇ H ₈ ). Such a gaseous carbon source is separated into carbon atoms and hydrogen atoms at high temperatures.

The separated carbon atoms are deposited on the heated catalyst metal 301 and are formed of graphene 302 as the catalyst metal 301 cools. In FIG. 2A, although graphene 302 is formed on both surfaces of the catalyst metal 301, the graphene 302 may be formed only on one surface of the catalyst metal 301.

The graphene 302 may be formed as a single layer, but is not limited thereto and may be formed as a multilayer of two or more layers.

Next, the support forming step (S120) proceeds.

As shown in FIG. 2B, the support 303 is formed on one surface of the graphene 302 in which the catalytic metal 301 is not disposed. The support 303 may be a heat peelable film or a polymer coating.

First, when the support 303 is a heat peeling film, the support 303 is formed by attaching the heat peeling film to one surface of the graphene 302 on which the catalyst metal 301 is not disposed. Although one surface of the heat-peelable film has adhesiveness at room temperature, it has a property of losing adhesiveness when heated above a predetermined peeling temperature, and a product having various peeling temperatures can be selected. Meanwhile, in the above embodiment, a heat peeling film is used as the support 303, but the present invention is not limited thereto. Of course, if the graphene 302 is used to transfer the transfer object film, a variety of carrier films can be used in addition to the thermal peeling film.

Meanwhile, when the support 303 is a polymer coating, the support 303 is formed by drop coating a liquid polymer on one surface of the graphene 302 where the catalyst metal is not disposed. Polymers include polymethylmethacrylate (PMMA), polyamide (PA), polybutylene terephthalate (poly (butylenes terephtalate): PBT), polycarbonate (PC), polyethylene (PE) ), Poly (oxymethylene): POM, polypropylene (PP), polyphenylether (PPE), polystyrene (PS), polysulfone (PSU), liquid Liquid crystal polymer (LCP), polyetheretherketone (PEEK), polyetherimide (PEI), polylactide (PLA), polydimethylsiloxane (poly ( At least one of dimethylsiloxane: PDMS) and cycloolefin copolymer (COC) may be used.

Next, a process (S130, S140) of removing the catalyst metal 301 is performed.

According to one embodiment of the present invention, the process of removing the catalytic metal is performed in stages, and proceeds to a wet etching process.

First, a portion of the catalyst metal is removed by a wet etching process using the first etchant in the pre-removal step (S130).

The first etchant is iron chloride (FeCl ₃ ), iron nitrate (Fe (No ₃ ) ₃ ), copper chloride (CuCl ₂ ), ammonium persulfate ((NH ₄ ) ₂ S ₂ O ₈ ), sodium persulfate (Na ₂ S ₂ O ₈ ) solution and a persulfate type solution may be used. Preferably, the first etchant uses a solution capable of shortening the catalyst metal removal time by quickly removing the catalyst metal. In addition, the first etchant uses a cheap solution in consideration of economics during mass production. For example, the first etchant is a solution of iron chloride (FeCl ₃ ) or persulfate type, which has the advantage of faster catalytic metal removal time and lower price per unit volume than other solutions.

On the other hand, the first etchant can reduce the metal catalyst removal time using a high concentration solution compared to the second etchant used in the final removal step. For example, even when both the first etchant and the second etchant are made of persulfuric acid, when the concentration of the first etchant is about 2 times higher than the concentration of the second etchant, the etching rate may be about 1.2 to 2 times faster.

Fruit tree (mL) Sulfuric acid (mL) Additive (mL) Sheet resistance (Ω / sq) Required time (Min) 0.09 0.03 0.08 655 20 0.19 0.03 0.08 726 12

In Table 1 above, the sheet resistance means surface resistance per unit area of graphene, and in Table 1, the time required for removing the metal catalyst is exemplary, and the time required for removing the metal catalyst may vary depending on temperature and saturation of the catalyst metal. have.

The thickness t1 of the catalytic metal 301 remaining after removal in the pre-removal step S130 is about 0.15% to 50% of the initial catalyst metal thickness t. That is, in the pre-removal step S130, about 50% to 99.85% of the catalyst metal may be removed. In FIG. 2C t1 may be about 0.15% to 50% of t.

If the catalyst metal 301 is left in excess of about 50% of the initial catalyst metal thickness in the preliminary removal step S130, it takes a long time to remove the remaining catalyst metal 301 in the final removal step S140. Since the catalyst metal removal time depends on the final removal step (S140), in this case, there is a problem in that the catalyst metal removal time is not shortened compared to the prior art.

In addition, in the pre-removal step (S130), if the catalyst metal 301 remains less than about 0.15% of the thickness of the initial catalyst metal, damage occurs to the graphene 302, thereby increasing the sheet resistance of the graphene 302 and eventually There is a problem that the electrical characteristics of the pin 302 is degraded. In detail, the catalytic metal 301 is unevenly etched. That is, since the metal crystal direction, domain, electrolysis, rolling, etc. of the catalyst metal 301 are not uniform on the surface of the catalyst metal 301, the degree of penetration and reaction of the etchant in each part of the surface of the catalyst metal 301 is respectively. It is different. Thus, the catalytic metal 301 is etched unevenly overall. In order to reduce the damage of the graphene 302, the graphene 302 of a certain thickness must remain in the final removal step (S140), and the remaining thickness is determined as a step value of the catalytic metal 301. Experimentally, the catalytic metal 301 should remain at least about 0.05um to 35um, which is about 0.15% in terms of the thickness of the total metal catalyst.

Meanwhile, the line removing step S130 may be performed a plurality of times. That is, the catalyst metal 301 can be removed little by little over a plurality of times. As such, when the pre-removal step S130 is performed a plurality of times, the type and concentration of the etchant used in each step are different from each other. The type of etchant may be selected from the various types of first etchant described above.

Next, all remaining catalyst metals are removed by the wet etching process using the second etchant in the final removal step (S140).

The second etching solution is iron chloride (FeCl ₃ ), iron nitrate (Fe (No ₃ ) ₃ ), copper chloride (CuCl ₂ ), ammonium persulfate ((NH ₄ ) ₂ S ₂ O ₈ ), sodium persulfate (Na ₂ S ₂ O ₈ ) solution and a persulfate type solution may be used. Preferably, the second etchant, unlike the first etchant, uses a solution that can reduce damage to graphene. For example, even if the second etchant uses the same type as the first etchant used in the pre-removal step, it is possible to reduce damage of graphene by using a low concentration solution compared to the first etchant.

In the final removal step (S140), as shown in FIG. 2D, all remaining catalyst metal 301 is removed in the pre-removal step (S130) to expose the graphene 302. Therefore, since the second etchant can only contact the graphene 302, the second etchant must use a solution that can reduce damage to the graphene, unlike the first etchant.

In detail, the final removal step (S140) is characterized in that the catalytic metal 301 is removed such that the sheet resistance of the graphene 302 is in the range of about 10 ohms / sq to 3000 ohms / sq.

The reason is that when the sheet resistance of the graphene 302 becomes greater than about 3000 ohms / sq by the removing process of the final removing step S140, the graphene 302 cannot be used in the resistive touch screen. In this case, the sheet resistance becomes excessively large, and thus graphene cannot function as an electrode. On the other hand, if the sheet resistance of the graphene 302 is less than about 10 ohms / sq, it is difficult to achieve by the current technology, but may have a sheet resistance to a smaller range, preferably in accordance with future technology development.

Meanwhile, the sheet resistance of the graphene 302 is related to whether the graphene 302 is damaged. Graphene 302 is a film in which carbon is connected to each other in the form of a hexagon to form a honeycomb-shaped two-dimensional planar structure. The sheet resistance becomes large. That is, if the sheet resistance of the graphene 302 is greater than about 3000 ohms / sq, it means that the graphene 302 has excessive damage.

According to one embodiment of the present invention, by performing the catalytic metal removal step by at least two or more steps, there is an effect of reducing the catalyst metal removal time and maintaining the sheet resistance of the graphene 302 within a certain range. That is, in the pre-removal step (S130), the entire catalyst metal removal time is shortened by removing about 50% to 99.85% of the catalyst metal 301 using a first etchant having a high concentration and rapid etching rate. On the other hand, in the final removal step (S140) by removing all the remaining catalyst metal 301 using a second etchant having a low concentration and the sheet resistance of the graphene 302 in the range of about 10 ohms / sq to 3000 ohms / sq, Reduce the damage of the graphene 302. To this end, the first etchant may mainly use a solution of iron chloride (FeCl ₃ ) or persulfate type.

On the other hand, in the first removal step (S130) and the final removal step (S140), the first etchant and the second etchant is a catalyst of any one of spray-type (spray-type), bath-type (bath-type) or a combination thereof Supplied to the metal 301.

In the case of the spray type, the etchant is sprayed and supplied to the catalyst metal 301, and the catalyst metal 301 can be removed with a small amount of the etchant. In case of the bath type, the etching solution is filled in the tank and the catalyst metal 301 is immersed in the etching solution to remove the etching solution. However, the etching solution is required to contact the entire catalyst metal in order to perform etching.

Next, the washing and drying process (S150) is performed. In the cleaning and drying process, the first etchant and the second etchant remaining in the graphene 302 are removed. The cleaning process may be performed by wiping out residual impurities with ultrapure water (D.I water).

Next, the graphene transfer process (S160) is performed. Referring to FIG. 2E, the target film 304 is disposed on the exposed surface of the graphene 302, whereby the graphene 302 is transferred to the target film 304. As the target film 304, at least one of polyethylene terephthalate (PET), polyimide (PI), polydimethylsiloxane (PDMS: polydimethylsiloxane), plastic, synthetic rubber, and natural rubber may be used. The PET (polyethylene terephthalate) film 304 to which the graphene 302 is transferred may be used for a flexible display, an organic light emitting device, a solar cell, a touch screen, and the like.

Next, the support removal process (S170) is performed. When the support 303 is a heat peeling film, the graphene 302 and the heat peeling film are separated by applying a predetermined heat and pressure. On the other hand, when the support 303 is a polymer coating, the polymer coating is removed with an organic solvent such as acetone. 2F shows the graphene 302 film with the support 303 removed.

Finally, the graphene 302 doping process, drying process and analysis process may be further performed on the graphene 302 film of FIG. 2F.

On the other hand, Tables 2 to 4 are shown in contrast to one embodiment and a comparative example of the present invention to show the effect of the present invention.

In the Example, the metal catalyst removal step was performed in two steps as in the graphene obtaining method according to an embodiment of the present invention, and in Comparative Examples 1 and 2, the metal catalyst was removed in one step. In Example, the etchant 1 was used in the pre-removal step, and the etchant 2 was used in the final removal step. The type of etchant 1 is iron chloride, persulfate, and the like, and the type of etchant 2 is persulfate, SPS (sodium persulfate), and APS (ammonium persulfate). The etchant 1 used a solution having a faster etching rate than the etchant 2, and the etchant 2 used a solution capable of reducing the sheet resistance of graphene within a range of about 10 ohms / sq to 3000 ohms / sq. In the pre-removal step of Example, the thickness of the catalyst metal was about 2 μm to 3 μm. Meanwhile, in Comparative Example 1, the metal catalyst was removed only with the etching solution 1, and in Comparative Example 2, the metal catalyst was removed only with the etching solution 2. On the other hand, it may be a solvent such as the balance% water in the first etching solution.

First etchant type and concentration
Fruit tree: sulfuric acid (%) Second etchant type and concentration
Ammonium Persulfate (M) Total etching time
(minute) Sheet resistance of graphene
(Ohm / sq) Example 25:10 0.2 About 12 About 400

First etchant type and concentration
Fruit tree: sulfuric acid (%) Total etching time (minutes) Graphene Sheet Resistance (Ohms / sq) Comparative Example 1 25:10 About 8 About 3200

Second etchant type and concentration
Ammonium Persulfate (M) Total etching time (minutes) Graphene Sheet Resistance (Ohms / sq) Comparative Example 2 0.2 80 minutes About 400

As can be seen from the results of Table 2 and Table 3, the total etching time of the Example was almost similar to that of Comparative Example 1, but the sheet resistance of graphene was significantly lower in the Example than in Comparative Example 1. In addition, as can be seen from the results of Table 2 and Table 4, the sheet resistance of the graphene was almost similar to that of Comparative Example 2, but the total etching time was significantly shorter in the Example than in Comparative Example 2.

That is, in the case of the embodiment, by performing the catalytic metal removal step by step, the type and concentration of the etchant that can shorten the removal time of the catalyst metal in the pre-removal step, it is possible to reduce the damage of the graphene in the final removal step By using the type and concentration of the etchant, there is an advantage in that graphene with less damage can be obtained in less time than the comparative examples.

On the other hand, according to another embodiment of the present invention, the pre-removal step may be performed by a dry etching method, not a wet etching method. For example, plasma etching or polishing of one surface of the catalyst metal 301 on which the graphene 302 is not formed may be shortened before wet etching, which will be described later, to shorten the entire etching process time.

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

301: catalytic metal
302: graphene
303 support
304: target film

Claims (14)

Forming graphene on one surface of the catalytic metal;
Forming a support on a surface of the graphene on which the catalyst metal is not disposed;
A preliminary step of removing a portion of the catalyst metal by a wet etching process using a first etchant;
A final removal step of exposing the graphene by removing the remaining catalyst metal by a wet etching process using a second etching solution; And
Transferring the exposed graphene to a target film;
Obtaining graphene comprising a. The method of claim 1,
The first etching solution is a method for obtaining graphene is a solution that can remove the catalyst metal at a faster rate than the second etching solution. The method of claim 2,
The first etching solution is a method of obtaining graphene is a solution of iron chloride (FeCl ₃ ) or persulfate type. The method of claim 1,
The first etching solution is a method of obtaining graphene is a solution of a higher concentration than the second etching solution. 5. The method of claim 4,
The first etchant or the second etchant is iron chloride (FeCl ₃ ), iron nitrate (Fe (No ₃ ) ₃ ), copper chloride (CuCl ₂ ), ammonium persulfate ((NH ₄ ) ₂ S ₂ O ₈ ), sodium per A method for obtaining graphene using at least one of a sulfate (Na ₂ S ₂ O ₈ ) solution and a persulfate type solution. The method of claim 1,
The method of obtaining graphene, characterized in that the line removal step is carried out a plurality of times. The method according to claim 6,
When the pre-removal step is performed a plurality of times, the type or concentration of the etchant used in each step is different, the method for obtaining graphene. The method of claim 1,
The method of obtaining graphene, characterized in that the catalyst metal removed in the pre-removal step is 0.15% to 50% of the thickness of the initial catalyst metal. The method of claim 1,
The final removal step is a method for obtaining graphene, characterized in that to remove the catalytic metal so that the sheet resistance of the graphene is in the range of 10 ohm / sq to 3000 ohm / sq. The method of claim 1,
And the first etchant and the second etchant are supplied to the catalytic metal through any one of spray-type, bath-type, or a combination thereof. The method of claim 1,
A cleaning step of removing the first etchant and the second etchant remaining in the graphene after the final removal step; Obtaining graphene further comprising a. The method of claim 1,
The catalyst metal is nickel (Ni), cobalt (Co), iron (Fe), platinum (Pt), gold (Au), aluminum (Al), chromium (Cr), copper (Cu), magnesium (Mg), manganese From (Mn), rhodium (Rh), silicon (Si), tantalum (Ta), titanium (Ti), tungsten (W), uranium (U), vanadium (V), zirconium (Zr) and combinations thereof Obtaining graphene comprising at least one selected. The method of claim 1,
The graphene is a method for obtaining graphene consisting of a single layer or multiple layers. The method of claim 1,
The support is a method of obtaining graphene is a thermal peeling film or a polymer coating.

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