JP2018035010A - Production method of multi-layer graphene and multi-layer graphene laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of multi-layer graphene according to a novel method called layer exchange process.SOLUTION: A production method of the multi-layer graphene includes: a metal film forming step for forming a metal film by forming a metal dissolvable in carbon without forming a compound with carbon on an arbitrary substrate; a carbon film forming step of forming an amorphous carbon film on the metal film; a layer exchange step of exchanging layers of the metal film and the carbon film and of crystallizing the carbon film by heating the laminate in which the substrate, the metal film, and the carbon film are sequentially laminated; and a removing step of removing the metal film exposed on a surface by the layer exchange step.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing multilayer graphene and a multilayer graphene laminate.

  Graphene is composed of inexpensive carbon and has high electrical conductivity, high thermal conductivity, and high mechanical strength. Therefore, application in various fields such as high-speed transistors, sensors, transparent electrodes, large-scale integrated circuit (LSI) wiring, capacitors, and heat exhaust materials is expected.

  Multilayer graphene composed of such graphene has been attracting attention because it exhibits unique properties while inheriting the unique properties of graphene. For example, it is said that multilayer graphene has better electrical conductivity and thermal conductivity than graphene.

  Here, the multilayer graphene means a graphene layered in a plurality of layers. Multilayer graphene includes graphite in a broad sense. When the layer thickness is in units of μm to mm, it is expressed as graphite, and when it is less than that, it is often expressed as multilayer graphene.

  As a method for producing multilayer graphene, a mechanical peeling (transfer) method, a SiC surface thermal decomposition method, a thermal CVD method on a metal foil, and the like are known. Non-Patent Document 1 describes a method of producing a carbon film by a mechanical peeling (transfer) method. Non-Patent Document 2 describes a method of laminating a metal catalyst on a carbon film and producing multilayer graphene by a catalytic reaction of the metal catalyst.

Japanese Patent Laying-Open No. 2015-018882

K. S. Novoselov et al., Science 306 (2004) 666. K Gumi et al., Japanese Journal of Applied Physics 51 (2012) 06FD12-1. M Sato et al., Japanese Journal of Applied Physics 51 (2012) 04DB01-1.

  Among the application uses of multilayer graphene, for use as an electrode, LSI wiring, heat exhaust material, etc., it is necessary to handle a larger amount of electricity / heat, that is, to be able to flow a large amount of electricity / heat. In order to handle a larger amount of electricity and heat, the graphene film is required to have multiple layers and high crystallinity. In addition, since it is formed on a glass or LSI chip as a substrate, there is a demand for synthesis in a low temperature range where the substrate can withstand heat.

  However, using any of the methods described in Non-Patent Documents 1 to 3, high-quality multilayer graphene could not be obtained at low temperatures.

  With the method described in Non-Patent Document 1, multilayer graphene cannot be obtained with good reproducibility. The transfer process requires very delicate work. Therefore, the surface of graphene may be contaminated in the transfer process, or defects or wrinkles may be generated in the graphene, so that large-scale production of multilayer graphene is impossible.

  Further, the methods described in Non-Patent Documents 2 and 3 require high-temperature heating exceeding 600 ° C., and cannot be produced at a low temperature. The softening temperature of commercially available glass is about 550 ° C., and the types of substrates that can be used are limited. In addition, in the method using a catalytic reaction, the crystallinity and crystal orientation of multilayer graphene cannot be said to be sufficient, and high-quality multilayer graphene cannot be obtained.

  In addition, the other thermal CVD on metal foil requires heating at a temperature of 800 ° C. to 1000 ° C., and the SiC surface pyrolysis requires heat treatment at a high temperature of 1200 ° C. or higher. In addition, transfer is necessary to form multilayer graphene on an arbitrary substrate.

  The present invention has been made in view of the above problems, and an object thereof is to obtain a method for producing multilayer graphene by a new method.

As a result of intensive studies, the present inventors have found that multilayer graphene can be synthesized at a low temperature by layer exchange. In the field of semiconductors, Si and Ge have been known to exchange layers with metal films (metal catalyst induced growth method) (Patent Document 1), but it has been found that carbon can be exchanged with metal films. It has been done. Moreover, it discovered that the multilayer graphene obtained by layer exchange was high quality.
The present invention provides the following means in order to solve the above problems.

(1) In the method for producing multilayer graphene according to one embodiment of the present invention, a metal film forming step of forming a metal film on an arbitrary substrate by forming a metal that can be dissolved in carbon without forming a compound with carbon. A carbon film forming step of forming an amorphous carbon film on the metal film, and heating the laminate in which the substrate, the metal film, and the carbon film are sequentially laminated, and the metal film and the The method includes a layer exchange step for crystallizing the carbon film and a removal step for removing the metal film exposed on the surface by the layer exchange step.

(2) In the method for producing multilayer graphene according to the above aspect, the metal constituting the metal film is Ni, Co, Au, Pt, Cu, Ir, Ge, Os, P, Pb, Pd, Re, Rh, Ru. And any one selected from the group consisting of Ag.

(3) In the manufacturing method of the multilayer graphene concerning the said aspect, you may set the film thickness of the said metal film according to the film thickness of the multilayer graphene to produce.

(4) In the method for producing multilayer graphene according to the above aspect, the carbon constituting the carbon film may be more easily diffused than the metal constituting the metal film.

(5) In the method for producing multilayer graphene according to the above aspect, the heating atmosphere of the stacked body may be an oxygen-free atmosphere.

(6) In the manufacturing method of the multilayer graphene concerning the said aspect, 300 degreeC-1000 degreeC may be sufficient as the heating temperature of the said laminated body.

(7) A multilayer graphene laminate according to one embodiment of the present invention includes a substrate having a heat resistant temperature of 600 ° C. or less and multilayer graphene formed on the substrate, and the number of layers of the multilayer graphene is 10 or more. It is.

(8) The multilayer graphene laminated body concerning the said aspect WHEREIN: The said multilayer graphene may contain the metal below a solid solubility limit.

(9) In the multilayer graphene laminate according to the above aspect, an I _G / _ID ratio that is an intensity ratio of a G band peak and a D band peak in a Raman spectrum of the multilayer graphene may be 1.5 or more.

  According to the method for producing multilayer graphene according to the above aspect, multilayer graphene can be produced by a new method called layer exchange.

It is the schematic diagram which showed the manufacturing method of the multilayer graphene concerning 1 aspect of this invention. It is a phase diagram of carbon and nickel. It is a phase diagram of carbon and cobalt. It is the figure which showed the process of the layer exchange process typically. It is the result of having analyzed the section of the layered product after carrying out layer exchange, using Ni as a metal film. It is a graph which shows the result of the energy dispersive X ray analysis (EDX) of the multilayer graphene obtained by removing surface Ni from the laminated body measured in FIG. It is the figure which showed the Raman spectrum of the multilayer graphene manufactured by the manufacturing method of the multilayer graphene concerning this embodiment. It is a Raman spectrum of multilayer graphene obtained by changing the heating conditions in the layer exchange step. It is a schematic diagram of the graphene layered product concerning one mode of the present invention. It is a schematic diagram of the multilayer graphene laminated body produced with the conventional method.

  Hereinafter, a method for producing multilayer graphene according to one embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In the drawings used in the following description, in order to make the characteristics of the present invention easier to understand, there are cases where the characteristic parts are enlarged for the sake of convenience, and the dimensional ratios of the respective components are different from actual ones. is there. The materials, dimensions, and the like exemplified in the following description are examples, and the present invention is not limited to them, and can be appropriately modified and implemented without departing from the scope of the invention.

"Production method of multilayer graphene"
The manufacturing method of multilayer graphene concerning one mode of the present invention includes a metal film formation process, a carbon film formation process, a layer exchange process, and a metal film removal process. FIG. 1 is a schematic view illustrating a method for producing multilayer graphene according to one embodiment of the present invention.

<Metal film formation process>
As shown in FIG. 1A, in the metal film forming step, a metal capable of forming a solid solution with carbon without forming a compound with carbon is formed on an arbitrary substrate 1 to form a metal film 2.

  The substrate 1 may be made of any material. In the method for producing multilayer graphene according to one embodiment of the present invention, the heating temperature necessary for producing the multilayer graphene can be arbitrarily set. Therefore, the heat resistance of the substrate 1 is not questioned as a condition for selecting the substrate 1.

  Moreover, the shape of the board | substrate 1 is not ask | required. Both the metal film 2 and the carbon film 3 described later are formed on the substrate 1 by film formation. Therefore, the substrate is not limited to the flat substrate shown in FIG. 1A, and a substrate having an arbitrary shape can be used. Further, the substrate 1 can cope with a large area.

  The metal film 2 is formed on the substrate 1. The metal film 2 is made of a metal that can form a solid solution with carbon without forming a compound with carbon. Here, the metal that does not form a compound with carbon means a metal that does not bond to carbon at the atomic level. That is, it means that the chemical formula corresponding to the compound is not known, and is generally called a eutectic metal. Further, the metal capable of solid solution of carbon means a metal having a carbon solid solubility of about 0.1 atm% or more.

It can be confirmed from the phase diagram that the metal does not form a compound with carbon and can form a solid solution. FIG. 2 is a phase diagram of carbon and nickel. FIG. 3 is a phase diagram of carbon and cobalt. 2 and 3, the horizontal axis represents the carbon composition ratio (x _c ), and the vertical axis represents the temperature. 2 and 3, LIQUID means a liquid phase state, FCC_A1 means a face-centered cubic crystal structure, and HCP_A1 means a hexagonal close-packed crystal structure. Both nickel and cobalt are metals in which carbon does not form a compound and carbon can be dissolved.

It can be confirmed from FIGS. 2 and 3 that nickel and cobalt do not form a compound with carbon. For example, in the region where the carbon ratio is high (x _c ≧ 0.1), the graphite and the metal exist separately, except when melted at a high temperature. This is indicated by “+” in FIGS. 2 and 3. That is, it can be said that nickel and cobalt are not bonded to carbon and do not form a compound.

It can also be confirmed from FIGS. 2 and 3 that carbon can be dissolved in nickel and cobalt. 2 and 3, there is a triangular region represented by FCC_A1 in a region where the carbon ratio is low (x _c <0.1) and in a temperature region of 2000 ° C. or lower. Within this triangular region, the crystal has a face-centered cubic structure, and nickel, cobalt, and carbon do not exist separately. That is, it can be said that carbon is dissolved in nickel and cobalt.

Thus, a metal that does not form a compound with carbon and can form a solid solution can be selected from the phase diagram. Specific examples of metals having such a phase diagram include Ni, Co, Au, Pt, Cu, Ir, Ge, Os, P, Pb, Pd, Re, Rh, Ru, and Ag.

  The method for forming the metal film 2 on the substrate 1 is not particularly limited. For example, a sputtering method, a vapor deposition method, a chemical vapor deposition method (CVD method), or the like can be used.

  The film thickness of the metal film 2 matches the film thickness of the finally synthesized multilayer graphene. Therefore, it is preferable to set the thickness of the metal film 2 in accordance with the required thickness of the multilayer graphene. In other words, the film thickness of the multilayer graphene finally synthesized can be controlled by the film thickness of the metal film 2.

<Carbon film formation process>
Next, as shown in FIG. 1A, an amorphous carbon film 3 </ b> A is formed on the metal film 2.

  The carbon film 3A is formed in an amorphous state. When the carbon film 3A is laminated in a crystalline state, the carbon film 3A is stabilized in terms of energy, and layer exchange described later does not occur.

  The method for forming the carbon film 3A is not particularly limited. It can be formed by the same method as the metal film 2. The metal film 2 and the carbon film 3A may be formed continuously or intermittently. When the film is continuously formed, the time required for releasing the atmosphere and evacuating again can be shortened. On the other hand, when the film is formed intermittently, an oxide film for controlling the speed of mutual diffusion is formed at the interface between the layers, and the resulting multilayer graphene has high quality. Depending on the required use and the required production efficiency, it can be changed as appropriate.

<Layer exchange process>
Next, as shown in FIG. 1B, the stacked body 5 in which the substrate 1, the metal film 2, and the carbon film 3A are sequentially stacked is heated. The carbon film 3A undergoes layer exchange with the metal film 2 by heating and crystallizes. A multilayer graphene 3B is formed between the substrate 1 and the metal film 2.

  FIG. 4 is a diagram schematically showing the process of the layer exchange process. When the stacked body 5 is heated, the carbon atoms constituting the carbon film 3A diffuse to the substrate 1 side. Carbon atoms diffuse mainly through the crystal grain boundaries of the metal film 2 and the like. Therefore, a columnar portion 3a composed of diffusing carbon atoms is formed between the substrate 1 and the carbon film 3A.

  When the heating is continued, the columnar portion 3 a spreads in the in-plane direction of the stacked body 5. The metal film 2 is pushed up in a direction away from the substrate 1 by the columnar portion 3a extending in the in-plane direction. As a result, the positional relationship between the carbon film 3A and the metal film 2 in the stacked body 5 is reversed. At this time, the carbon film 3A is crystallized to become multilayer graphene 3B.

  The carbon film 3A is amorphous and unstable in energy. Therefore, when energy is given by heating, an energy stable state is selected and crystallized. The carbon film 3A is not crystallized in situ but crystallized between the substrate 1 and the metal film 2.

  This is considered to be influenced by the diffusion rate of carbon atoms constituting the carbon film 3A increased by heating and the rate at which the carbon film 3A crystallizes. When the carbon film 3A is heated, the diffusion rate of carbon atoms constituting the carbon film 3A increases. If this diffusion rate is faster than the rate of carbon crystallization, the carbon atoms constituting the carbon film 3A will first diffuse. As a result, it is considered that the carbon atoms constituting the carbon film 3 </ b> A diffuse in the metal film 2 and are crystallized at the interface between the substrate 1 and the metal film 2.

Further, it is preferable that the carbon constituting the carbon film 3 </ b> A is more easily diffused than the metal constituting the metal film 2. In other words, the diffusion coefficient of the metal constituting the metal film 2 is preferably smaller than the diffusion coefficient of the carbon constituting the carbon film 3A.
When the metal constituting the metal film 2 diffuses faster than the carbon constituting the carbon film 3A, the metal diffuses into the carbon film 3A. In this case, the columnar portion 3a as shown in FIG. 4 is hardly formed, and layer exchange may not occur.

  The atmosphere when heating the laminated body 5 is preferably an atmosphere not containing oxygen. For example, a rare gas atmosphere such as Ar or a nitrogen atmosphere is preferable. In an oxygen atmosphere, oxygen and carbon constituting the carbon film 3A react to form carbon dioxide or the like. When the carbon film 3A performs an unnecessary reaction, the generation efficiency of the multilayer graphene 3B is lowered.

  It is preferable that the temperature which heats the laminated body 5 is 300 to 1000 degreeC from a viewpoint of productivity and the selectivity of the board | substrate 1. FIG. In order to perform the layer exchange reaction, it is necessary to apply a predetermined heat load to the carbon film 3A. The heat load is a value determined by the heating temperature and the heating time. For example, when the heating temperature is 1000 ° C., layer exchange occurs when heated for about 2 minutes. When the heating temperature is 500 ° C., layer exchange occurs when heated for about 6 hours.

  The time for heating the stacked body 5 varies depending on the heating temperature as described above. Considering the production efficiency, it is preferable that the heating time is short.

  FIG. 5 shows the result of analyzing the cross section of the laminate after layer exchange using Ni as the metal film. FIG. 5A is a HAADF image of a scanning transmission electron microscope (STEM). A HAADF image can be obtained as a contrast image depending on the size of the atomic number. FIG. 5B shows the result of energy dispersive X-ray analysis (EDX). FIG. 5C is a transmission electron microscope (TEM) image, and FIG. 5D is an enlarged view of the dotted line portion of FIG. The Ni and carbon films were formed by sputtering, and heating in the layer exchange step was performed in an Ar atmosphere at 600 ° C. for 10 minutes.

As shown in FIG. 5, it can be confirmed that a carbon layer is formed between Ni as the metal film 2 and SiO _{2 as} the substrate 1 by any measurement method. That is, the metal film 2 and the carbon film 3 are exchanged by heating. Further, as shown in FIG. 5D, the carbon layer after the layer exchange is composed of multilayer graphene oriented in one direction.

<Metal film removal process>
Finally, as shown in FIG. 1C, the metal film 2 exposed on the surface is removed by the layer exchange process. The method for removing the metal film 2 is not particularly limited. Various methods such as chemical etching, physical etching, polishing, and ion beam can be used.

  FIG. 6 is a graph showing the results of energy dispersive X-ray analysis (EDX) of multilayer graphene obtained by removing Ni on the surface of the laminate measured in FIG. Ni was etched using an iron chloride solution.

As shown in FIG. 6, no Ni-derived peak was confirmed in the EDX results after Ni removal. Further, the peak of C derived from the multilayer graphene is confirmed, and it can be confirmed that the multilayer graphene is maintained even after etching.
In addition, since EDX also obtains information in the thickness direction of about several μm, a peak derived from SiO _{2 of} the substrate has been confirmed at the same time.

  By removing the metal film 2, the multilayer graphene 3 </ b> B remains on the substrate 1. That is, multilayer graphene is formed on an arbitrary substrate 1.

FIG. 7 is a diagram showing a Raman spectrum of multilayer graphene manufactured by the multilayer graphene manufacturing method according to the present embodiment. The Raman spectrum shown in FIG. 7 is a Raman spectrum obtained by measuring the multilayer graphene of the laminate measured in FIG. 5 from the substrate side. SiO ₂ is transparent, and the Raman spectrum can be measured from the substrate side.

  As shown in FIG. 7, in the Raman spectrum, peaks of D band, G band, and 2D band peculiar to graphene were confirmed. That is, multilayer graphene is appropriately formed on the substrate.

  In the Raman spectrum, the D band is a defect-derived peak, the G band is a graphite-derived peak, and the 2D peak is a peak derived from the number of graphite layers. In the Raman spectrum shown in FIG. 7, multilayer graphene having a small D-band peak and high crystallinity is obtained. It can also be seen from the ratio of the G band peak to the 2D peak that three or more layers of graphite are laminated.

  FIG. 8 is a Raman spectrum of multilayer graphene obtained by changing the heating conditions in the layer exchange step. The bottom graph in FIG. 8 is multilayer graphene obtained by heating at 500 ° C. for 6 hours. The second graph from the bottom in FIG. 8 is the same as FIG. 7, and is a multilayer graphene obtained by heating at 600 ° C. for 10 minutes. The second graph from the top in FIG. 8 is multilayer graphene obtained by heating at 800 ° C. for 5 minutes. The top graph in FIG. 8 is multilayer graphene obtained by heating at 1000 ° C. for 2 minutes. Under either condition, multilayer graphene with high crystallinity is obtained.

  As described above, according to the method for producing multilayer graphene according to one embodiment of the present invention, multilayer graphene can be produced by a new method called layer exchange. Since layer exchange occurs even at a temperature of 600 ° C. or lower, high-quality multilayer graphene can be produced even at low temperatures.

"Multilayer graphene laminate"
A multilayer graphene laminate according to one embodiment of the present invention is manufactured by the above-described multilayer graphene manufacturing method.

  FIG. 9 is a schematic view of a graphene laminate according to one embodiment of the present invention. As shown in FIG. 9, the graphene laminated body 10 concerning 1 aspect of this invention is equipped with the board | substrate 1 and the multilayer graphene 3B.

  The substrate 1 has a heat resistant temperature of 600 ° C. or lower. Here, the heat resistant temperature means a deflection temperature under load determined by the substrate JIS 7191 for the substrate 1, and means a softening temperature when the substrate 1 is made of glass or the like. That is, it means a temperature at which the substrate 1 can no longer maintain its shape against a load or the like.

  The multilayer graphene 3B has 10 or more layers. In order to form the multilayer graphene 3B having 10 or more layers on the substrate 1 having a low heat resistant temperature, it is necessary to synthesize the multilayer graphene 3B at a low temperature. Therefore, the multilayer graphene 3B can be realized by the multilayer graphene manufacturing method according to one embodiment of the present invention.

The I _G / _ID ratio, which is the intensity ratio of the G band peak to the D band peak in the Raman spectrum of the multilayer graphene 3B, is preferably 1.5 or more, and more preferably 2.0 or more. A large I _G / _ID ratio means that the multilayer graphene 3B has good crystallinity. That is, it can be said that the crystal constituting the multilayer graphene 3B has a large grain size and the graphene constituting the crystal is oriented in one direction. In FIG. 8, the result of heating at 500 ° C. is an I _G / _ID ratio of 2.2, the result of heating at 600 ° C. is an I _G / _ID ratio of 2.4, and the result of heating at 800 ° C. is _IG / _{I D} ratio is 2.4, 1000 ° C. the results of the heating are 2.7 _I G / _{I D} ratio.

  Electrons and heat responsible for electrical conduction travel along the graphene layer. Therefore, the multilayer graphene 3B having excellent crystallinity is excellent in electrical conductivity and thermal conductivity.

FIG. 10 is a schematic diagram of a multilayer graphene laminate 11 produced by a conventional method. Here, as an example of a conventional method, there is a method of heat-treating an amorphous carbon film at a high temperature.
As shown in FIG. 10, the crystallinity of multilayer graphene 3B ′ produced by a conventional method is not sufficient. That is, the multilayer graphene 3B ′ is composed of a collection of small multilayer graphene crystals, and the orientation in which the graphene is oriented varies. Therefore, it cannot be said that the multilayer graphene 3B ′ of the multilayer graphene laminate 11 has sufficient electrical conductivity and thermal conductivity. In the methods of Non-Patent Documents 2 and 3, crystallization does not occur in the treatment at 600 ° C., and a multilayer graphene film cannot be obtained on a substrate having a heat resistance of 600 ° C. or lower.

  The multilayer graphene 3B contains a metal having a solid solubility limit or less. Actually, it contains a metal having a solid solubility limit. This metal is a metal constituting the metal film formed in the above-described multilayer graphene manufacturing method.

As described in the above-described method for producing multilayer graphene (FIG. 4), the multilayer graphene 3B is formed between the substrate 1 and the metal film 2 with the metal film 2 interposed therebetween. Therefore, the multilayer graphene 3B contains a metal having a solid solubility limit. For example, when the metal film 2 is made of Ni, the Ni content is about 10 ¹⁹ cm ⁻³ or less.

  As described above, in the multilayer graphene laminate according to the present embodiment, multilayer graphene is laminated on a substrate having low heat resistance. Therefore, it can be directly applied to an electrode of an integrated circuit or the like without performing transfer or the like, and has wide versatility.

  The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific embodiments, and various modifications can be made within the scope of the gist of the present invention described in the claims. Can be modified or changed.

  According to this method for producing a multilayer graphene film, a multilayer graphene film can be produced on an arbitrary substrate at a low temperature. Therefore, it can be used in the fields of various electronic devices such as electrodes of integrated circuits, heat spreaders, and storage battery electrodes.

DESCRIPTION OF SYMBOLS 1 ... Board | substrate, 2 ... Metal film, 3A ... Carbon film, 3B, 3B '... Multi-layer graphene, 3a ... Columnar part, 5 ... Laminated body, 10, 11 ... Multi-layer graphene laminated body

Claims (9)

A metal film forming step of forming a metal film on an arbitrary substrate by forming a metal that can be dissolved in carbon without forming a compound with carbon; and
A carbon film forming step of forming an amorphous carbon film on the metal film;
A layer exchange step of heating the substrate, the laminate of the metal film and the carbon film in order, exchanging the metal film and the carbon film, and crystallizing the carbon film;
And a removal step of removing the metal film exposed on the surface by the layer exchange step.   The metal constituting the metal film is any one selected from the group consisting of Ni, Co, Au, Pt, Cu, Ir, Ge, Os, P, Pb, Pd, Re, Rh, Ru, and Ag. Item 2. A method for producing multilayer graphene according to Item 1.   The manufacturing method of the multilayer graphene in any one of Claim 1 or 2 which sets the film thickness of the said metal film according to the film thickness of the multilayer graphene to produce.   The method for producing multilayer graphene according to any one of claims 1 to 3, wherein carbon constituting the carbon film is more easily diffused than metal constituting the metal film.   The manufacturing method of the multilayer graphene as described in any one of Claims 1-4 with which the heating atmosphere of the said laminated body does not contain oxygen.   The method for producing multilayer graphene according to any one of claims 1 to 5, wherein a heating temperature of the laminate is 300 ° C to 1000 ° C. A substrate having a heat-resistant temperature of 600 ° C. or lower;
Multilayer graphene formed on the substrate,
A multilayer graphene laminate in which the number of layers of the multilayer graphene is 10 or more.   The multilayer graphene laminate according to claim 7, wherein the multilayer graphene contains a metal having a solid solubility limit or less. 9. The multilayer graphene laminate according to claim 7, wherein an I _G / _ID ratio that is an intensity ratio of a G band peak and a D band peak in a Raman spectrum of the multilayer graphene is 1.5 or more.