Method for producing graphene

Abstract

Provided is a method for producing graphene, in which heat bias inside a reaction vessel can be suppressed.　Provided is a method for producing graphene using a thermal CVD device, wherein the thermal CVD device has a cylindrical reaction vessel inside of which a base material for graphene production is accommodated, a gas supply unit that is connected to the reaction vessel and supplies a hydrocarbon-containing raw material gas toward the base material, a gas discharge unit that discharges gas, a heater that covers the periphery of a region including a region in which the base material is accommodated and that heats the inside of the reaction vessel, and a shielding member that is disposed inside the reaction vessel and intercepts the movement of heat. The shielding member is disposed at least between the gas supply unit and the substrate and between the substrate and the gas discharge unit, and the relationship of formula (x1) holds, where W is the flow rate of the raw material gas introduced from the gas supply unit, S is the internal cross-sectional area of the reaction vessel, and x is the inside diameter of the reaction vessel.　Formula (x1): W / S ≤ 54.97 × exp{–0.128 × (x – 4.0)}

Description

How graphene is produced

[0001] The present invention relates to a method for producing graphene using a thermal CVD (Chemical Vapor Deposition) apparatus.

[0002] Graphene is a material in which carbon atoms are sp ２ Graphite is made up of stacked graphene sheets, with carbon atoms and their bonds forming a hexagonal lattice structure (hexagonal mesh).

[0003] Patent Literature 1 describes a method for producing graphene, in which the surface of a substrate is oxidized to form an oxide layer, and a nanocarbon material layer (graphene layer) is formed on the surface of the oxide layer. More specifically, the method describes a method in which the substrate is placed in a reaction vessel, a gaseous carbon source is supplied into the reaction vessel, and the substrate in the reaction vessel is heated to form a nanocarbon material layer on the oxide layer formed on the substrate. Note that the method for forming a graphene layer described in Patent Literature 1 corresponds to CVD.

[0004] Japanese Patent Application Laid-Open No. 2021-178760

[0005] The present inventors have studied the production method described in Patent Document 1 and found that uneven heat distribution may occur inside the reaction vessel. When uneven heat distribution occurs inside the reaction vessel, problems such as inefficient production of graphene may occur. Such a decrease in efficiency during graphene production may become more significant when the diameter of the reaction vessel is increased.

[0006] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a method for producing graphene that can suppress uneven heat distribution inside a reaction vessel.

[0007] As a result of extensive research into the above-mentioned problems, the inventors have found that the heat bias can be suppressed by adjusting the gas flow rate so that a predetermined relationship is satisfied between the internal cross-sectional area, the inner diameter of the reaction vessel, and the flow rate of the raw material gas, and have arrived at the present invention.

[0008] That is, the inventors have found that the above problems can be solved by the following configuration. a gas discharge part connected to the reaction vessel on the side opposite to the gas supply part and discharging gas from inside the reaction vessel; a heater covering a periphery of an area of ​​the reaction vessel including an area where the substrate is accommodated and heating the inside of the reaction vessel; and a shielding member disposed inside the reaction vessel and blocking heat transfer inside the reaction vessel, the shielding member being disposed at least between the gas supply part and the substrate and between the substrate and the gas discharge part, the graphene production method satisfying a relationship in formula (x1) described below, where W is a flow rate of the source gas introduced from the gas supply part, S is an internal cross-sectional area of ​​the reaction vessel, and x is an inner diameter of the reaction vessel. [2] The graphene production method according to [1], wherein the shielding members include a first shielding member, a second shielding member, a third shielding member, and a fourth shielding member arranged in this order inside the reaction vessel from the gas supply part side toward the gas discharge part side of the reaction vessel, the second shielding member and the third shielding member being arranged in a region of the reaction vessel that is covered by the heater, and the first shielding member and the fourth shielding member being arranged in a region of the reaction vessel that is not covered by the heater. [3] The graphene production method according to [2], wherein the first shielding member, the second shielding member, the third shielding member, and the fourth shielding member each include one or two or more shielding plates, each of the shielding plates having one or more holes, and an opening ratio of each of the shielding plates with respect to an internal cross-sectional area of ​​the reaction vessel is 0.1 to 40%.[4] The graphene production method according to [3], wherein the first shielding member, the second shielding member, the third shielding member, and the fourth shielding member each include two or more shielding plates arranged at a constant interval d1, and a ratio D12 / d1 of a distance D12 between the first shielding member and the second shielding member to the interval d1, and a ratio D34 / d1 of a distance D34 between the third shielding member and the fourth shielding member to the interval d1 are each 0.03 to 52.88. [5] The graphene production method according to [4], wherein, when the length of the first shielding member is length L1, the length of the second shielding member is length L2, the length of the third shielding member is length L3, and the length of the fourth shielding member is length L4, a ratio D12 / L1 of the distance D12 to the length L1 and a ratio D12 / L2 of the distance D12 to the length L2 are each 0.01 to 23.27, and a ratio D34 / L3 of the distance D34 to the length L3 and a ratio D34 / L4 of the distance D34 to the length L4 are each 0.01 to 23.27. [6] The graphene production method according to [4] or [5], wherein, when a distance from an end of the region covered by the heater on the gas supply unit side to the first shielding member is defined as a distance D1H, a value X1H calculated by the following formula (1) using the distance D12 is 0.01 or more, and when a distance from an end of the region covered by the heater on the gas discharge unit side to the fourth shielding member is defined as a distance D4H, a value X4H calculated by the following formula (2) using the distance D34 is 0.01 or more. Formula (1) X1H=(D12-D1H) / D12 Formula (2) X4H=(D34-D4H) / D34 [7] The graphene production method according to [6], wherein the values ​​X1H and X4H are 0.60 to 1.00. [8] The graphene production method according to any one of [3] to [7], wherein an aperture ratio of the shielding plate in the first shielding member is larger than an aperture ratio of the shielding plate in the second shielding member, and an aperture ratio of the shielding plate in the fourth shielding member is larger than an aperture ratio of the shielding plate in the third shielding member.[9] The graphene production method according to any one of [3] to [8], wherein a product of the aperture ratios of the shielding plates constituting the first shielding member and the second shielding member and a product of the aperture ratios of the shielding plates constituting the third shielding member and the fourth shielding member are each 0.0009 to 0.0700%.

[10] The graphene production method according to any one of [3] to [9], wherein the second shielding member comprises two or more shielding plates, and the second shielding member includes the shielding plates having different aperture ratios, and the third shielding member comprises two or more shielding plates, and the second shielding member includes the shielding plates having different aperture ratios.

[11] The graphene production method according to any one of [3] to

[10] , wherein the second shielding member includes two or more shielding plates, and the aperture ratio of the shielding plate of the second shielding member arranged closest to the third shielding member is smaller than the aperture ratio of the shielding plate of the second shielding member arranged closest to the first shielding member, and the third shielding member includes two or more shielding plates, and the aperture ratio of the shielding plate of the third shielding member arranged closest to the second shielding member is smaller than the aperture ratio of the shielding plate of the third shielding member arranged closest to the fourth shielding member.

[12] The graphene production method according to any one of [3] to

[11] , wherein the first shielding member includes two or more shielding plates, and the aperture ratio of the shielding plate of the first shielding member arranged closest to the gas supply unit is smaller than the aperture ratio of the shielding plate of the first shielding member arranged closest to the second shielding member, and the fourth shielding member includes two or more shielding plates, and the aperture ratio of the shielding plate of the fourth shielding member arranged closest to the gas discharge unit is smaller than the aperture ratio of the shielding plate of the fourth shielding member arranged closest to the third shielding member.

[13] The graphene production method according to any one of [3] to

[12] , wherein the shielding plate comprises at least one selected from the group consisting of silicon oxide, silicon nitride, graphite, aluminum oxide, aluminum nitride, tantalum oxide, tantalum carbide, niobium oxide, niobium carbide, and molybdenum oxide.

[14] The graphene production method according to any one of [3] to

[13] , wherein the second shielding member and the third shielding member are made of metal.

[15] The graphene production method according to any one of [1] to

[14] , wherein a value obtained by dividing a temperature measured at the following first position by a temperature measured at the following second position is 0.62 or more. First position: a position in the axial direction of the reaction vessel on the surface of the first shielding member facing the substrate. Second position: a position in the axial direction of the reaction vessel on the center of the substrate, wherein the temperatures measured at the first position and the second position are expressed in °C.

[16] The graphene production method according to any one of [1] to

[15] , wherein the reaction vessel has an inner diameter of 12.7 to 38.1 cm.

[17] The graphene production method according to any one of [1] to

[16] , wherein the reaction vessel has an inner diameter of 15.24 to 35.56 cm.

[18] The graphene production method according to any one of [1] to

[17] , wherein the reaction vessel has an inner diameter of 20.32 to 30.48 cm.

[19] The graphene production method according to any one of [1] to

[18] , wherein the reaction vessel contains silicon dioxide.

[20] The graphene production method according to any one of [1] to

[19] , comprising placing the substrate including a metal film containing at least one selected from the group consisting of copper, nickel, and iron in the reaction vessel, supplying a raw material gas containing a hydrocarbon from the gas supply unit, and heating the inside of the reaction vessel to 900 to 1,100°C with the heater, to form a graphene layer on the metal film.

[0009] According to the present invention, a method for producing graphene can be provided that can suppress uneven heat distribution inside a reaction vessel.

[0010] Fig. 1 is a cross-sectional schematic diagram of one embodiment of a thermal CVD apparatus used in the graphene production method of the present invention. Fig. 2 is a cross-sectional schematic diagram of a first shielding member 11. Fig. 3 is a schematic diagram of the first shielding member 11 as viewed from the gas supply unit 22 side. Fig. 4 is a cross-sectional schematic diagram of a shielding plate portion of the first shielding member in a reaction chamber of the thermal CVD apparatus.

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments. Various modifications and substitutions can be made to the following embodiments without departing from the scope of the present invention.

[0012] The meanings of terms used in this specification are as follows: A numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0013] In this specification, graphene includes not only single-layer graphene consisting of a single graphene sheet, but also multi-layer graphene consisting of stacked single-layer graphene sheets. The number of layers of the graphene sheets in the multi-layer graphene is preferably 2 to 10, more preferably 2 to 5. Note that the graphene sheet is an sp ２ Graphene is a sheet of carbon atoms bonded together in a plane by bonds, with a thickness of one carbon atom. A graphene sheet has a carbon atom at each vertex of the hexagonal mesh.

[0014] The graphene production method of the present invention (hereinafter also referred to as "the present production method") is a production method for producing graphene using a thermal CVD apparatus. The thermal CVD apparatus has a gas supply unit connected to a reaction vessel and supplying a source gas containing a hydrocarbon toward a substrate accommodated inside the reaction vessel, and a gas discharge unit connected to the reaction vessel on the side opposite to the gas supply unit and discharging gas from inside the reaction vessel. In addition, the thermal CVD apparatus used in the present production method has a heater that surrounds an area of ​​the reaction vessel including an area where the substrate is accommodated and heats the inside of the reaction vessel. The thermal CVD apparatus has a cylindrical reaction vessel that accommodates a substrate for graphene production inside, and a gas supply unit connected to the reaction vessel and supplying a source gas containing a hydrocarbon toward the substrate accommodated inside the reaction vessel. The reaction vessel further comprises a gas discharge section connected to the side opposite to the gas supply section and discharging gas from inside the reaction vessel, a heater surrounding an area of ​​the reaction vessel including an area where the substrate is accommodated and heating the inside of the reaction vessel, and a shielding member disposed inside the reaction vessel and blocking heat transfer inside the reaction vessel. The shielding member is disposed at least between the gas supply section and the substrate and between the substrate and the gas discharge section. Furthermore, in this production method, when the flow rate of the raw material gas introduced from the gas supply section is W, the internal cross-sectional area of ​​the reaction vessel is S, and the inner diameter of the reaction vessel is x, the relationship of the following formula (x1) is satisfied: W / S ≦ 54.97 × exp {−0.128 × (x − 4.0)} Formula (x1) In formula (x1), W is in cm ３ / min, which represents the gas flow rate per minute converted into a volume value at 1 atmosphere and 0°C. In formula (x1), the unit of S is cm ２ In formula (x1), the unit of x is cm.

[0015] The manufacturing method will be described below in detail with a detailed description of the thermal CVD apparatus used in the manufacturing method. After the thermal CVD apparatus used in the manufacturing method is described, the manufacturing method will be described in detail.

[0016] <Thermal CVD Apparatus> The thermal CVD apparatus used in this production method has a reaction vessel in which a substrate for graphene production is accommodated. The thermal CVD apparatus used in this production method further has a gas supply unit connected to the reaction vessel and supplying a source gas containing a hydrocarbon toward the substrate accommodated inside the reaction vessel, a gas discharge unit connected to the side of the reaction vessel opposite the gas supply unit side and discharging gas from inside the reaction vessel, and a gas discharge unit connected to the side of the reaction vessel opposite the gas supply unit side. In addition, the thermal CVD apparatus used in this production method has a heater that surrounds the area of ​​the reaction vessel including the area in which the substrate is accommodated and heats the inside of the reaction vessel.

[0017] The thermal CVD apparatus used in this manufacturing method is described below with reference to the drawings.

[0018] FIG. 1 shows a schematic cross-sectional view of one embodiment of a thermal CVD apparatus used in this manufacturing method. The thermal CVD apparatus 100 includes a cylindrical reaction vessel 10. A substrate S1 for graphene production is placed inside the reaction vessel 10. The substrate S1 is placed on a boat B1. A gas supply unit 22 is connected to one end of the reaction vessel 10, and a gas discharge unit 24 is connected to the other end of the reaction vessel 10. A hydrocarbon-containing source gas is supplied from the gas supply unit 22 to the substrate S1 through a pipe (not shown) connected to the gas supply unit 22 (see the open arrow in FIG. 1 ). The gas supplied from the gas supply unit 22 and used in the reaction inside the reaction vessel 10 is discharged from the gas discharge unit 24 (see the filled arrow in FIG. 1 ). The reaction vessel 10 includes a region A2, including a region A1 containing the substrate S1, surrounded by a heater 26. The region A2, covered by the heater 26, can heat the interior of the reaction vessel 10.

[0019] A first shielding member 11, a second shielding member 12, a third shielding member 13, and a fourth shielding member 14 are arranged in this order from the gas supply unit 22 side within the reaction vessel 10. In the thermal CVD apparatus 100, a source gas is supplied from the gas supply unit 22, the substrate S1 and the source gas are heated by the heater 26, and graphene is produced on the substrate S1 by thermal CVD.

[0020] In the thermal CVD apparatus 100, the second shielding member 12 and the third shielding member 13 are disposed in an area A2 of the reaction vessel 10 that is covered by the heater 26. Specifically, the second shielding member 12 is disposed in the reaction vessel 10 on the side where the substrate S1 is disposed relative to an imaginary line VL1 that indicates the end of the heater 26 on the gas supply unit 22 side in Fig. 1. On the other hand, the third shielding member 13 is disposed in the reaction vessel 10 on the side where the substrate S1 is disposed relative to an imaginary line VL2 that indicates the end of the heater 26 on the gas discharge unit 24 side in Fig. 1.

[0021] In the thermal CVD apparatus 100, the first shielding member 11 and the fourth shielding member 14 are disposed in an area A3 of the reaction vessel 10 that is not covered by the heater 26. Specifically, the first shielding member 11 is disposed in the reaction vessel 10 on the gas supply unit 22 side of the imaginary line VL1 indicating the end of the heater 26 in Fig. 1. On the other hand, the fourth shielding member 14 is disposed in the reaction vessel 10 on the gas discharge unit 24 side of the imaginary line VL2 indicating the end of the heater 26 in Fig. 1.

[0022] The first shielding member 11, the second shielding member 12, the third shielding member 13, and the fourth shielding member 14 each include three shielding plates. Details of each shielding member will be described later. In the embodiment shown in FIG. 1 , the first shielding member 11, the second shielding member 12, the third shielding member 13, and the fourth shielding member 14 are used as the shielding members. However, in the present manufacturing method, for example, the second shielding member 12 and the third shielding member 13 may be omitted. In another embodiment, the first shielding member 11 and the fourth shielding member 14 may be omitted. The shielding members may be disposed at least between the gas supply unit 22 and the substrate S1 and between the substrate S1 and the gas discharge unit 24, and may be disposed in a manner other than that shown in FIG. 1 .

[0023] By using thermal CVD apparatus 100 (the thermal CVD apparatus used in this manufacturing method) and adjusting it so as to satisfy the relationship of the above formula (x1), it is possible to suppress uneven distribution of heat inside reaction vessel 10. The mechanism by which this manufacturing method can suppress uneven distribution of heat inside reaction vessel 10 is not entirely clear, but the inventors speculate as follows.

[0024] In the thermal CVD apparatus 100 shown in FIG. 1 , shielding members are disposed in the above-described positions within the reaction vessel 10. More specifically, the first shielding member 11 and the second shielding member 12 are disposed between the gas supply unit 22 and the substrate S1, and the third shielding member 13 and the fourth shielding member 14 are disposed between the substrate S1 and the gas discharge unit 24. Each shielding member prevents heat from the heater 26 from transferring to the gas supply unit 22 side and the gas discharge unit 24 side of the reaction vessel 10. Here, when the source gas is supplied from the gas supply unit 22 so as to satisfy the relationship of the above formula (x1), the supply amount of the source gas becomes relatively small relative to the inner diameter of the reaction vessel 10. In this case, the source gas supplied from the gas supply unit 22 is likely to be sufficiently heated by the heater 26 before being supplied toward the substrate S1. As a result, the source gas is preheated before being introduced toward the region A1 where the substrate S1 is placed, so that uneven distribution of heat inside the reaction vessel 10 can be suppressed.

[0025] The following describes in detail the configuration of the thermal CVD apparatus 100 and other configurations that may be included in the thermal CVD apparatus 100. The thermal CVD apparatus used in this manufacturing method may be configured in a manner other than that shown in Fig. 1. That is, the configuration of the thermal CVD apparatus may be modified to the following manner.

[0026] The reaction vessel 10 is cylindrical, and its inner diameter is, for example, 10 cm or more, preferably 12.7 cm or more, more preferably 15.24 cm or more, and even more preferably 20.32 cm or more. The inner diameter is, for example, 50 cm or less, and is preferably 38.1 cm or less, more preferably 35.56 cm or less, and even more preferably 30.48 cm or less, in order to further suppress uneven distribution of heat inside the reaction vessel 10.

[0027] The wall thickness of the reaction vessel 10 is, for example, preferably 1 to 50 mm, more preferably 2 to 40 mm. The length of the reaction vessel 10 is not particularly limited, but may be, for example, 20 m or less, preferably 10 m or less. The length of the reaction vessel 10 may be, for example, 0.5 m or more, preferably 1 m or more.

[0028] It is preferable that the reaction vessel 10 does not deform or otherwise deteriorate when heated by the heater 26. Examples of materials constituting the reaction vessel 10 include materials containing at least one selected from the group consisting of silicon oxide, silicon nitride, graphite, aluminum oxide, aluminum nitride, tantalum oxide, tantalum carbide, niobium oxide, niobium carbide, and molybdenum oxide. More specifically, silicon oxide (quartz glass) is preferred.

[0029] The gas supply unit 22 is not particularly limited as long as it can supply a hydrocarbon-containing source gas and can control the supply amount of the source gas so as to satisfy the relationship shown in formula (x1) above. For example, the gas supply unit 22 is connected to a flow control valve and a gas supply source, and supplies the source gas from a gas reservoir while controlling the supply amount with the flow control valve. Furthermore, the source gas supplied from the gas supply unit 22 may be a mixed gas, as described below. When a mixed gas is supplied as the source gas from the gas supply unit 22, a gas mixing unit may be provided. The gas mixing unit mixes gases supplied from gas supply sources that supply the respective components constituting the mixed gas. When a mixed gas is supplied as the source gas, a flow control valve is preferably provided between the gas mixing unit and the gas supply source. Examples of gas supply sources include known gas cylinders. Examples of the flow control valve include known mass flow controllers. The source gas will be described in detail later.

[0030] A pressure gauge may be connected to the gas supply unit 22. The supply amount of the source gas supplied from the gas supply unit 22 may be controlled based on the pressure measured by the pressure gauge. A known pressure gauge may be applied as the pressure gauge depending on the desired pressure.

[0031] The gas discharge part 24 is not particularly limited as long as it can discharge gas from the inside of the reaction vessel 10. For example, the gas discharge part 24 connects the reaction vessel 10 to the outside via a valve (for example, a check valve, a pressure regulating valve, etc.). The gas discharge part 24 may also be connected to a known exhaust gas treatment means. Examples of the exhaust gas treatment means include a combustion type exhaust gas treatment device that combusts hydrocarbons and the like contained in the discharged gas.

[0032] A pressure gauge may be connected to the gas discharge unit 24. The supply amount of the source gas supplied from the gas supply unit 22 may be controlled based on the pressure measured by the pressure gauge. The opening of the pressure regulating valve may also be adjusted based on the measured pressure. A known pressure gauge may be used as the pressure gauge depending on the desired pressure.

[0033] Furthermore, a vacuum exhaust means may be connected to the gas exhaust section 24. A known vacuum pump can be used as the vacuum exhaust means connected to the gas exhaust section 24. When the vacuum exhaust means is connected to the gas exhaust section 24, the vacuum exhaust means and the gas exhaust section 24 may be connected via the valve, and the vacuum exhaust means may be connected to the outside.

[0034] The heater 26 surrounds the area A2 of the reaction vessel 10, including the area A1 in which the substrate S1 is accommodated, and heats the inside of the reaction vessel 10. When the inside of the reaction vessel 10 is heated, the substrate S1 accommodated inside the reaction vessel 10 and the supplied raw material gas are heated, and graphene is formed on the substrate S1. The heater 26 is preferably capable of heating the inside of the reaction vessel 10 to 900°C or higher, preferably 950°C or higher, and preferably 1,000°C or higher. The upper limit of the temperature to which the heater 26 can heat the reaction vessel 10 is not particularly limited, but may be, for example, 1,200°C or lower.

[0035] The heater 26 is not particularly limited as long as it can heat the inside of the reaction vessel 10, and examples thereof include a heater 26 composed of a heat source and a heat-resistant plate disposed between the heat source and the reaction vessel 10. Examples of the heat source include a heat source that generates heat by resistance heating. The heat-resistant plate is composed of, for example, aluminum oxide (alumina, etc.) fibers.

[0036] The first shielding member 11 and the second shielding member 12 prevent heat from the heater 26 from transferring to the gas supply part 22 side of the reaction vessel 10. The third shielding member 13 and the fourth shielding member 14 prevent heat from the heater 26 from transferring to the gas discharge part 24 side of the reaction vessel 10. Hereinafter, the first shielding member 11 will be described as a representative shielding member.

[0037] 2A and 2B , the details of the first shielding member 11 of the embodiment shown in FIG. 1 will be described. FIG. 2A shows a cross-sectional schematic diagram of the first shielding member 11. The first shielding member 11 shown in FIG. 2A includes three shielding plates 110a, 110b, and 110c. The three shielding plates 110a, 110b, and 110c are connected to each other by connecting rods 112 and arranged at a predetermined interval d1. FIG. 2B shows a schematic diagram of the first shielding member 11 shown in FIG. 1 as viewed from the gas supply unit 22 side in the left-right direction of the paper surface of FIG. 1. Note that FIG. 2B shows only the shielding plate 110a, which is arranged closest to the gas supply unit 22 among the three shielding plates (shielding plates 110a, 110b, and 110c) that make up the first shielding member 11. 2B, the shielding plate 110a has seven holes, holes H1 to H7. Holes H1 to H6 are arranged at positions that are sextuple-symmetric with respect to the center of the circular shielding plate 110a, and hole H7 is arranged at the center position of the circular shielding plate 110a.

[0038] The material constituting the shielding plate 110a preferably includes at least one selected from the group consisting of silicon oxide (e.g., quartz glass), silicon nitride, graphite, aluminum oxide, aluminum nitride, tantalum oxide, tantalum carbide, niobium oxide, niobium carbide, and molybdenum oxide. The material constituting the shielding plate 110a may also be a metal. Examples of the metal include known metals such as iron, niobium, and molybdenum. The metal may also be an alloy, such as steel or stainless steel. The thickness of the shielding plate 110a is not particularly limited, but is often 0.1 mm or more, and preferably 0.5 mm or more. The thickness of the shielding plate 110a is often 5.0 mm or less.

[0039] The size (e.g., diameter) of the shielding plate 110a is smaller than the size (e.g., diameter) of the cross section of the interior of the reaction vessel 10, since it is installed inside the reaction vessel 10. Therefore, as shown in FIG. 3, a gap C1 is formed between the shielding plate 110a and the inner wall surface of the reaction vessel 10. When the reaction vessel 10 is cylindrical, the value obtained by subtracting the diameter of the shielding plate 110a from the inner diameter (diameter) of the reaction vessel 10 is preferably 0.1 cm or more, more preferably 0.3 cm or more. Furthermore, the value is preferably 3.0 cm or less.

[0040] Here, the aperture ratio of the shielding plate 110a relative to the internal cross-sectional area of ​​the reaction vessel 10 is preferably 0.1% or more, more preferably 1% or more, even more preferably 5% or more, and particularly preferably 10% or more. The aperture ratio is preferably 65% ​​or less, more preferably 32% or less, and even more preferably 16% or less. The aperture ratio is defined as the ratio of the shaded area in FIG. 3 to the internal cross-sectional area of ​​the reaction vessel 10. FIG. 3 is a schematic cross-sectional view of the shielding plate 110a of the first shielding member 11 in the reaction vessel 10 of the thermal CVD apparatus 100 shown in FIG. 1. That is, when determining the aperture ratio, first, the area of ​​the shielding plate 110a minus the holes (holes H1 to H7) in the shielding plate 110a is determined as the area value of the shielding plate 110a. Next, the opening ratio (unit: %) is calculated by subtracting the area of ​​the shielding plate 110a from the internal cross-sectional area of ​​the reaction vessel 10, dividing the obtained value by the internal cross-sectional area of ​​the reaction vessel 10, and multiplying the result by 100. The opening ratio corresponds to the ratio of the area of ​​the portion not shielded by the shielding plate 110a (portion through which the source gas can pass) to the internal cross-sectional area of ​​the reaction vessel 10.

[0041] The aperture ratios of the shielding plates 110b and 110c are also determined in the same manner as above. The preferred range of the aperture ratios of the shielding plates 110b and 110c is the same as the preferred range of the aperture ratio of the shielding plate 110a.

[0042] The aperture ratio of the shielding plate 110a can be adjusted by the number and size of the holes in the shielding plate 110a, for example, by the sizes of the holes H1 to H7 in the shielding plate 110a.

[0043] The configuration of the shielding plates 110b and 110c constituting the first shielding member 11 may be the same as or different from that of the shielding plate 110a. For example, in the first shielding member 11, the aperture ratios of the shielding plates 110a, 110b, and 110c may be different from each other or may be the same as each other.

[0044] It is also preferable that the first shielding member 11 includes shielding plates 110a, 110b, and 110c with different aperture ratios. When the first shielding member 11 includes shielding plates with different aperture ratios, it is preferable that the aperture ratio of the shielding plate arranged closest to the gas supply unit 22 is smaller than the aperture ratio of the shielding plate arranged closest to the second shielding member 12. In other words, when the first shielding member 11 includes shielding plates with different aperture ratios, it is preferable that the aperture ratio of the shielding plate 110a is smaller than the aperture ratio of the shielding plate 110c.

[0045] Furthermore, the product of the aperture ratios of the shielding plates constituting the first shielding member 11 is preferably 0.0005% or more, more preferably 0.0008% or more, and even more preferably 0.0010% or more. Furthermore, the product of the aperture ratios is preferably 80.0000% or less, more preferably 10.0000% or less, still more preferably 6.0000% or less, and particularly preferably 1.0000% or less. Specifically, the product of the aperture ratios is obtained by multiplying the aperture ratio of shielding plate 110a by the aperture ratio of shielding plate 110b by the aperture ratio of shielding plate 110c.

[0046] The shielding plate 110a may have a configuration other than that shown in FIG. 2B . For example, the arrangement of the holes, the number of holes, and the size of the holes can be changed as appropriate. The shielding plate 110b and the shielding plate 110c may have the same configuration as the shielding plate 110a. Furthermore, the shielding plate 110a, the shielding plate 110b, and the shielding plate 110c may have the same configuration as each other, may have partially the same configuration, or may have different configurations. Furthermore, when the first shielding member 11 includes three or more shielding plates, the distances between adjacent shielding plates may be the same or different.

[0047] 1, the first shielding member 11 includes three shielding plates, but the first shielding member 11 may include only one shielding plate. When the first shielding member is configured with only one shielding plate, the product of the aperture ratios of the shielding plates is the aperture ratio of that shielding plate. Alternatively, the first shielding member 11 may include two or more shielding plates (for example, 2 to 10 plates, preferably 2 to 6 plates).

[0048] Examples of the second shielding member 12, the third shielding member 13, and the fourth shielding member 14 are similar to the examples of the first shielding member 11, and therefore description thereof will be omitted. In particular, it is preferable that the aperture ratio of the shielding plates in the first shielding member 11 is greater than the aperture ratio of the shielding plates in the second shielding member 12, and that the aperture ratio of the shielding plates in the fourth shielding member 14 is greater than the aperture ratio of the shielding plates in the third shielding member 13. The aperture ratio of the shielding plates in the first shielding member 11 refers to the aperture ratio of the shielding plates when the first shielding member 11 includes only one shielding plate, and refers to the aperture ratio of the shielding plate with the smallest aperture ratio among the shielding plates that constitute the first shielding member 11 when the first shielding member 11 includes two or more shielding plates. The difference between the aperture ratio of the shielding plates in the first shielding member 11 and the aperture ratio of the shielding plates in the second shielding member 12 is preferably 0 to 12.4%. The difference between the aperture ratio of the shielding plates in the fourth shielding member 14 and the aperture ratio of the shielding plates in the third shielding member 13 is preferably 0 to 12.4%. In order to further suppress heat imbalance inside the reaction vessel 10, it is also preferable that the difference between the aperture ratio of the shielding plates in the first shielding member 11 and the aperture ratio of the shielding plates in the second shielding member 12 is 0 to 1%, and that the difference between the aperture ratio of the shielding plates in the fourth shielding member 14 and the aperture ratio of the shielding plates in the third shielding member 13 is 0 to 1%.

[0049] It is also preferable that the second shielding member 12 includes two or more shielding plates, and that the aperture ratio of the shielding plate of the second shielding member 12 arranged closest to the third shielding member 13 is smaller than the aperture ratio of the shielding plate of the second shielding member 12 arranged closest to the first shielding member 11. It is also preferable that the third shielding member 13 includes two or more shielding plates, and that the aperture ratio of the shielding plate of the third shielding member 13 arranged closest to the second shielding member 12 is smaller than the aperture ratio of the shielding plate of the third shielding member 13 arranged closest to the fourth shielding member 14. The difference in aperture ratio between the shielding plate of the second shielding member 12 arranged closest to the third shielding member 13 and the shielding plate arranged closest to the first shielding member 11 is preferably 0 to 12.4%. The difference in aperture ratio between the shielding plate of the third shielding member 13 that is arranged closest to the second shielding member 12 and the shielding plate that is arranged closest to the fourth shielding member 14 is preferably 0 to 12.4%. It is also preferable that the fourth shielding member 14 includes two or more shielding plates, and the aperture ratio of the shielding plate of the fourth shielding member 14 that is arranged closest to the gas discharge section 24 is smaller than the aperture ratio of the shielding plate of the fourth shielding member 14 that is arranged closest to the third shielding member 13. The difference in aperture ratio between the shielding plate of the fourth shielding member 14 that is arranged closest to the gas discharge section 24 and the shielding plate that is arranged closest to the third shielding member 13 is preferably 0 to 12.4%.

[0050] Furthermore, the value obtained by multiplying the product of the aperture ratios of the shielding plates constituting the first shielding member 11 by the product of the aperture ratios of the shielding plates constituting the second shielding member 12 is preferably 0.0004% or more, more preferably 0.0006% or more, even more preferably 0.0008% or more, and particularly preferably 0.0010% or more. The value obtained by multiplying the product of the aperture ratios is preferably 0.0700% or less, more preferably 0.0100% or less, and even more preferably 0.0020% or less. The value obtained by multiplying the product of the aperture ratios of the shielding plates constituting the third shielding member 13 by the product of the aperture ratios of the shielding plates constituting the fourth shielding member 14 is preferably 0.0004% or more, more preferably 0.0006% or more, even more preferably 0.0008% or more, and particularly preferably 0.0010% or more. Moreover, the value obtained by multiplying the product of the aperture ratios is preferably 0.0700% or less, more preferably 0.0100% or less, and even more preferably 0.0020% or less.

[0051] 1 , the distance between the first shielding member 11 and the second shielding member 12 is defined as distance D12, and the distance between the third shielding member 13 and the fourth shielding member 14 is defined as distance D34. Note that distance D12 refers to the distance from the end of the first shielding member 11 closest to the second shielding member 12 to the end of the second shielding member 12 closest to the first shielding member 11. Similarly, distance D34 refers to the distance from the end of the third shielding member 13 closest to the fourth shielding member 14 to the end of the fourth shielding member 14 closest to the third shielding member 13. Also, consider a case where the first shielding member 11, the second shielding member 12, the third shielding member 13, and the fourth shielding member 14 are each formed of two or more shielding plates arranged at a fixed interval d1 (see FIG. 2A ). In this case, the ratio D12 / d1 of the distance D12 to the spacing d1 is preferably 0.03 or more, more preferably 1.2 or more, and even more preferably 2.7 or more, in order to allow the source gas to remain between the first shielding member 11 and the second shielding member 12 for a longer period of time to be preheated and to further suppress uneven heat distribution within the reaction vessel 10. The ratio D12 / d1 is preferably 52.88 or less, more preferably 23.50 or less, and even more preferably 3.8 or less, in order to allow the source gas to remain between the shielding members for a longer period of time to be preheated and to further suppress uneven heat distribution within the reaction vessel 10. In addition, the ratio D34 / d1 of the distance D34 to the spacing d1 is preferably 0.03 or more, more preferably 1.2 or more, and even more preferably 2.7 or more, in order to allow the gas to remain between the third shielding member 11 and the fourth shielding member 12 for a longer period of time to be heated and to further suppress uneven heat distribution within the reaction vessel 10. The ratio D34 / d1 is preferably 52.88 or less, more preferably 23.50 or less, and even more preferably 3.8 or less, in that it allows the gas to remain between the shielding plates for a longer period of time and be heated, thereby further suppressing heat imbalance within the reaction vessel 10.

[0052] 1, the length of the first shielding member 11 is defined as length L1, the length of the second shielding member 12 as length L2, the length of the third shielding member 13 as length L3, and the length of the fourth shielding member 14 as length L4. The lengths of the shielding members refer to the lengths from one end of the shielding member to the other. The ratio D12 / L1 of the distance D12 to the length L1 and the ratio D12 / L2 of the distance D12 to the length L2 are each preferably 0.01 or greater, more preferably 0.43 or greater, and even more preferably 1.00 or greater. Furthermore, the ratios (the ratios D12 / L1 and D12 / L2) are each preferably 23.27 or less, more preferably 10.34 or less, and even more preferably 1.39 or less. In this case, the ratio D34 / L3 of the distance D34 to the length L3 and the ratio D34 / L4 of the distance D34 to the length L4 are each preferably 0.01 or more, more preferably 0.43 or more, and even more preferably 1.00 or more. Furthermore, the ratios (ratios D34 / L3 and D34 / L4) are each preferably 23.27 or less, more preferably 10.34 or less, and even more preferably 1.39 or less.

[0053] 1, the distance from the end (imaginary line VL1) of the region A2 where the reaction vessel 10 is covered by the heater 26 on the gas supply section 22 side to the first shielding member 11 is defined as distance D1H. Also, the distance from the end (imaginary line VL2) of the region A2 where the reaction vessel 10 is covered by the heater 26 on the gas discharge section 24 side to the fourth shielding member 14 is defined as distance D4H. In this case, it is preferable that the value X1H calculated by the following formula (1) is 0.01 or more. It is also preferable that the value X4H calculated by the following formula (2) is 0.01 or more. When the values ​​X1H and X4H are each within the above ranges, the uneven distribution of heat within the reaction vessel 10 is further suppressed. Formula (1) X1H = (D12 - D1H) / D12 Formula (2) X4H = (D34 - D4H) / D34

[0054] The value X1H indicates the ratio of the length of the region of the distance D12 that is not covered by the heater 26 to the distance D12. Similarly, the value X4H indicates the ratio of the length of the region of the distance D34 that is not covered by the heater 26 to the distance D34. When the value X1H is 1.00, this indicates that the end of the heater 26 on the gas supply unit 22 side coincides with the end of the first shielding member 11 on the second shielding member 12 side. Similarly, when the value X4H is 1.00, this indicates that the end of the heater 26 on the gas discharge unit 24 side coincides with the end of the fourth shielding member 14 on the third shielding member 13 side. The value X1H is preferably 0.60 or greater, and more preferably 0.80 or greater, in order to further suppress heat distribution bias within the reaction vessel 10. The value X4H is preferably 0.60 or greater, and even more preferably 0.80 or greater, in order to further suppress heat distribution bias within the reaction vessel 10. The maximum values ​​of the above values ​​X1H and X4H are both 1.00.

[0055] Furthermore, when the second shielding member 12 and the third shielding member 13 are omitted, the distances D1H and D4H are each preferably 50 cm or less, and more preferably 15 cm or less. Furthermore, the distances D1H and D4H may each be 0 cm. When the second shielding member 12 and the third shielding member 13 are omitted, the first shielding member 11 is preferably positioned closer to the gas supply unit 22 than the virtual line VL1. When the second shielding member 12 and the third shielding member 13 are omitted, the fourth shielding member 14 is preferably positioned closer to the gas discharge unit 24 than the virtual line VL2.

[0056] When the second shielding member 12 and the third shielding member 13 are omitted, the product of the aperture ratios of the shielding plates constituting the first shielding member 11 is preferably 0.0004% or more, more preferably 0.0006% or more, even more preferably 0.0008% or more, and particularly preferably 0.0010% or more. Furthermore, the value obtained by multiplying the products of the aperture ratios is preferably 0.0700% or less, more preferably 0.0100% or less, and even more preferably 0.0020% or less. When the second shielding member 12 and the third shielding member 13 are omitted, the product of the aperture ratios of the shielding plates constituting the fourth shielding member 14 is preferably 0.0004% or more, more preferably 0.0006% or more, even more preferably 0.0008% or more, and particularly preferably 0.0010% or more. Moreover, the value obtained by multiplying the product of the aperture ratios is preferably 0.0700% or less, more preferably 0.0100% or less, and even more preferably 0.0020% or less.

[0057] The boat B1 is arranged to hold the substrate S1. Typically, the boat B1 is loaded into the reaction vessel 10 with the substrate S1 placed on it. The upper surface of the boat B1, on which the substrate S1 is placed, may be flat, or may be provided with rails, claws, etc. for fixing the substrate S1. It is preferable that the boat B1 does not deform when heated by the heater 26. Examples of materials that can be used to form the boat B1 include the same materials as those that can be used to form the shielding plate.

[0058] Although the boat B1 in the embodiment shown in FIG. 1 holds one substrate S1, the boat B1 may hold two or more substrates S1. In this case, the substrates S1 may be arranged in the boat B1 in the left-right direction of the paper surface of FIG. 1, in the front-rear direction of the paper surface, or in the up-down direction of the paper surface. Among these, an embodiment in which the substrates S1 are arranged in the up-down direction of the paper surface is preferred from the viewpoint of facilitating uniform supply of the source gas. Note that when producing graphene on the substrate S1 using the thermal CVD apparatus 100, the boat B1 may be omitted if unnecessary. Furthermore, the boat B1 may be replaced with a holder or the like on which the substrate S1 can be placed.

[0059] <Graphene Manufacturing Method> The graphene manufacturing method of the present invention (the present manufacturing method) uses the thermal CVD apparatus (for example, the thermal CVD apparatus 100 shown in FIG. 1 ) used in the present manufacturing method described above. Specifically, a source gas containing a hydrocarbon is supplied from the gas supply unit 22 to the substrate S1 accommodated in the reaction vessel 10, and the source gas and the substrate S1 in the reaction vessel 10 are heated by the heater 26, thereby forming graphene on the substrate S1. As described above, the present manufacturing method may use a thermal CVD apparatus of a configuration other than that shown in FIG. 1 . The supply amount of the source gas is adjusted so as to satisfy the relationship of the above-mentioned formula (x1).

[0060] The substrate S1 preferably has a metal film. The metal film is preferably disposed on the surface of the substrate S1. The metal film is preferably a metal film containing at least one selected from the group consisting of copper, nickel, and iron, more preferably a metal film containing copper or nickel, and even more preferably a metal film containing copper. The metal film may be a simple metal or an alloy containing the metal. The metal film preferably has an exposed surface that matches the lattice constant of graphene. Specifically, the (111) surface of copper and the (111) surface of nickel are preferably exposed. It is more preferable that the metal film has only the exposed surface with the Miller index.

[0061] The substrate S1 preferably has an oxide layer as an underlayer for the metal film. The oxide layer preferably has a lattice constant that matches that of the metal film. Examples of such an oxide layer include oxide films containing one or more elements selected from the group consisting of magnesium, aluminum, titanium, and lanthanum, and oxide films containing magnesium or aluminum are preferred. Preferred examples of oxide films include MgO (magnesium oxide), α-Al ２ O ３ (alumina), LaAlO ３ , and TiO ２ and the like, and MgO or α-Al ２ O ３ is preferred.

[0062] One embodiment of the substrate S1 including an oxide layer and a metal film is a substrate made of the material of the oxide layer, on which a metal film is formed. Another embodiment of the substrate S1 including an oxide layer and a metal film is a substrate made of the material of the oxide layer, on which the oxide layer and the metal film are formed in this order. Examples of materials constituting the substrate include SiO ２ (quartz) is an example of a material containing the substrate. It is also preferable that the substrate has a small coefficient of linear thermal expansion.

[0063] The source gas contains a hydrocarbon. In addition to the hydrocarbon, the source gas may contain at least one of an inert gas and a reducing gas. Examples of hydrocarbons include methane, ethane, ethylene, acetylene, propane, propylene, butane, butadiene, pentane, pentene, cyclopentadiene, hexane, cyclohexane, benzene, and toluene. These may be used alone or in combination of two or more. Examples of inert gases include nitrogen gas, helium gas, neon gas, argon gas, and krypton gas. These may be used alone or in combination of two or more. Examples of reducing gases include hydrogen gas.

[0064] Consider a case where the source gas contains a hydrocarbon, an inert gas, and a reducing gas. In this case, the hydrocarbon content is preferably 0.00001 vol% or more, more preferably 0.0001 vol% or more, based on the total volume of the source gas. The hydrocarbon content is preferably 0.1 vol% or less, more preferably 0.01 vol% or less. In this case, the inert gas content is preferably 90 vol% or more, more preferably 95 vol% or more, and even more preferably 98 vol% or more, based on the total volume of the source gas. The inert gas content is often 99.9 vol% or less. In this case, the reducing gas content is preferably 0.01 vol% or more, more preferably 0.1 vol% or more, based on the total volume of the source gas. The reducing gas content is preferably 5 vol% or less, more preferably 2 vol% or less.

[0065] As described above, the supply amount of the source gas is adjusted so as to satisfy the relationship of the following formula (x1). Specifically, the supply amount of the source gas satisfies the relationship of the following formula (x1), where W is the flow rate of the source gas introduced from the gas supply unit 22, S is the internal cross-sectional area of ​​the reaction vessel 10, and x is the inner diameter (diameter) of the reaction vessel 10. Formula (x1) W / S≦54.97×exp{−0.128×(x−4.0)} In formula (x1), the unit of W is cm ３ / min, which represents the gas flow rate per minute converted into a volume value at 1 atmosphere and 0°C. In formula (x1), the unit of S is cm ２ In formula (x1), the unit of x is cm. The value obtained by dividing the value on the left side of formula (x1) by the value on the right side is preferably 0.01 or more, more preferably 0.1 or more, even more preferably 0.3 or more, and particularly preferably 0.5 or more. In addition, the value is 1 or less, and preferably 0.97 or less.

[0066] The heating temperature inside the reaction vessel 10 by the heater 26 is preferably 900°C or higher, more preferably 950°C or higher, and even more preferably 1,000°C or higher. The heating temperature inside the reaction vessel 10 by the heater 26 is preferably 1,200°C or lower, more preferably 1,150°C or lower, and even more preferably 1,100°C or lower. The heating temperature inside the reaction vessel 10 can be measured, for example, by inserting a thermocouple into the boat B1 and the substrate S1. The heating time inside the reaction vessel 10 by the heater 26 is preferably 5 minutes or longer, and more preferably 10 minutes or longer. The heating time is preferably 120 minutes or shorter, and more preferably 60 minutes or shorter.

[0067] The heating of the inside of the reaction vessel 10 by the heater 26 may be divided into a plurality of regions, and the heating temperature of each region may be controlled to a different temperature. For example, in the embodiment shown in FIG. 1 , the region A2 is divided into a region A2a from the imaginary line VL1 to the end of the second shielding member 12 on the substrate S1 side, a region A2b from the end of the second shielding member 12 on the substrate S1 side to the end of the third shielding member 13 on the substrate S1 side, and a region A2c from the end of the third shielding member 13 on the substrate S1 side to the imaginary line VL2. When the region A2 is divided into the regions A2a, A2b, and A2c as described above, the regions A2a, A2b, and A2c may be controlled to different temperatures. For example, it is preferable to control the heating temperature of region A2b within the range described above for the heating temperature inside the reaction vessel 10 by the heater 26, and it is preferable to control the heating temperatures of region A2a and region A2c to a temperature 180 to 280°C (more preferably, 200 to 260°C) higher than the heating temperature of region A2b.

[0068] It is also preferable that the value obtained by dividing the temperature (°C) measured at the first position described below by the temperature (°C) measured at the second position described below is 0.62 or greater. First position: A position in the axial direction of the reaction vessel 10 on the surface of the first shielding member 11 facing the substrate S1. Second position: A position in the axial direction of the reaction vessel 10 at the center of the substrate S1. The axial direction of the reaction vessel 10 refers to the longitudinal direction of the reaction vessel 10 (the left-right direction on the paper surface of FIG. 1). Examples of methods for measuring the temperatures at the first and second positions include a method in which known thermocouples are placed at the above positions to measure the temperature. The above value is more preferably 0.9 or greater. Furthermore, the above value is often 1.0 or less. Examples of methods for adjusting the temperature difference include dividing the region A2 into the regions A2a, A2b, and A2c described above and controlling each region to a different temperature. The preferred temperatures are as described above.

[0069] It is also preferable that the value obtained by dividing the temperature (°C) measured at the third position described below by the temperature (°C) measured at the second position described above is 0.62 or more. Third position: A position in the axial direction of the reaction vessel 10 on the surface of the fourth shielding member 14 on the substrate S1 side. Methods for measuring the temperature at the third position include methods similar to those for measuring the temperatures at the first and second positions described above. The value is more preferably 0.9 or more. In addition, the value is often 1.0 or less. In addition, an example of a method for adjusting the temperature difference is to divide the region A2 into the regions A2a, A2b, and A2c described above, and control each to a different temperature. The preferred temperatures are as described above.

[0070] After graphene is formed on the substrate S1 by the above procedure, a procedure of cooling the inside of the reaction vessel 10 may be carried out. When cooling the inside of the reaction vessel 10, the gas supplied from the gas supply unit 22 may contain hydrocarbons or may not contain hydrocarbons. The cooling may be carried out by removing the heater 26 from the reaction vessel 10 and air-cooling the reaction vessel 10, or by furnace-cooling the reaction vessel 10 with the heater 26 still attached.

[0071] In the graphene production method of the present invention, the thermal CVD apparatus 100 used in the present production method described above is used, a source gas containing a hydrocarbon is supplied from the gas supply unit 22 to the substrate S1 accommodated in the reaction vessel 10, the source gas and the substrate S1 in the reaction vessel 10 are heated by the heater 26, and graphene is formed on the substrate S1; however, other steps may also be included.

[0072] The other procedure includes a procedure of placing the first shielding member 11, the second shielding member 12, the third shielding member 13, and the fourth shielding member 14, as well as the boat B1 and the substrate S1, in the reaction vessel 10 before graphene formation.

[0073] Another example of the above-mentioned procedure is to supply a gas containing a reducing gas but not containing a hydrocarbon to the substrate S1 contained in the reaction vessel 10 from the gas supply unit 22 and heat the reaction vessel 10 with the heater 26 before graphene formation. By performing the above-mentioned procedure, the surface of the substrate S1 is reduced, making it easier to form graphene. The gas supplied in the above-mentioned procedure preferably contains the above-mentioned inert gas in addition to the reducing gas. The heating temperature by the heater 26 in the above-mentioned procedure can be adjusted appropriately depending on the material contained in the substrate S1; for example, the temperature may be 300 to 1,200°C, and preferably 500 to 1,100°C. When performing the above-mentioned procedure, it is also preferable to supply a gas containing a reducing gas from the gas supply unit 22, and then supply only the inert gas from the gas supply unit 22 to replace the atmosphere in the reaction vessel 10 with the inert gas, and then supply a raw material gas containing a hydrocarbon to start graphene formation.

[0074] <Applications> The graphene formed on the substrate S1 can be used for various applications. For example, it can be used in electromagnetic wave detection elements, electromagnetic wave sensors, electronic devices, and structures. In particular, a laminate having a graphene single film with excellent SPP propagation characteristics can be preferably used as a detection element, an amplification element, and an oscillation element for broadband electromagnetic waves.

[0075] The above-mentioned elements and the like can be manufactured by using graphene formed on the substrate S1 by a known method. For example, the formed graphene can be processed into a desired shape by applying photolithography and electron beam lithography. Furthermore, the formed graphene can be connected to desired electrodes and the like by a known semiconductor manufacturing process and used as an element.

[0076] The present invention will be described in more detail below based on examples. The materials, amounts used, ratios, treatment details, and treatment procedures shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the examples shown below. Examples 1 to 4 are examples, and Examples 5 to 8 are comparative examples.

[0077] Example 1 A fourth shielding member 14, a third shielding member 13, a boat B1 and a substrate S1, a second shielding member 12, and a first shielding member 11 were inserted in this order into a quartz glass reaction vessel 10 having a length of 170 cm and an inner diameter of 14 cm. The center position of the substrate S1 was adjusted so that it coincided with the axial center position of the reaction vessel 10. Next, a gas supply unit 22 and a gas discharge unit 24 were connected to both ends of the reaction vessel 10. A gas mixing unit (not shown) was connected to the gas supply unit 22. An argon gas cylinder serving as an argon gas supply source, a hydrogen gas cylinder serving as a hydrogen gas supply source, and a methane gas cylinder serving as a hydrocarbon supply source were each connected to the gas mixing unit via a mass flow controller (none of which are shown).

[0078] A heater 26 was positioned in the reaction vessel 10 so as to cover the periphery of region A2, including region A1 in which the substrate S1 was accommodated. More specifically, the heater 26 was positioned so as to cover an area of ​​52.5 cm on both sides from the axial center position of the reaction vessel 10. The first shielding member 11, the second shielding member 12, the third shielding member 13, and the fourth shielding member 14 each consisted of three shielding plates, and the aperture ratio of the shielding plates was 16%. The positional relationship of each shielding member was adjusted so as to be positioned to obtain the calculated values ​​shown in Table 1 below.

[0079] In addition, thermocouples (not shown) were inserted into the reaction vessel 10 to monitor the temperature of the inner wall surface of the reaction vessel 10 at various positions. Specifically, the thermocouples were positioned so that the temperature measuring parts of the thermocouples were located at the center of the substrate S1 and at positions 35 cm on both sides of the center of the substrate S1 in the axial direction of the reaction vessel 10. That is, the center of the substrate S1 was set as the origin, and the thermocouples were located at positions −35 cm, 0 cm, and 35 cm in the axial direction of the reaction vessel 10.

[0080] In order to calculate the heat distribution within the reaction vessel 10 by thermal fluid simulation, a model was created in which each component was placed within the reaction vessel 10. In this model, argon gas was supplied at the flow rate shown in the table below, and the output was adjusted so that the surface temperature of the heater 26 was 1,050°C. The simulation was run until a steady state was reached. The maximum temperature difference in the temperature distribution when the steady state was reached was used as an index of the heat distribution. Note that the temperature distribution is the temperature distribution in a plane parallel to the axial direction of the reaction vessel 10 and perpendicular to the surface of the substrate S1.

[0081] Examples 2 to 8: Except for adjusting the shielding members and conditions to achieve the conditions shown in the table below, an index of heat distribution in the reaction vessel 10 was obtained in the same manner as in Example 1. Note that, for example, in Example 2, the second shielding member 12 and the third shielding member 13 were omitted.

[0082] <Results> Table 1 shows the shielding members and conditions for each example, as well as the heat bias index for each example. In Table 1, the aperture ratio refers to the aperture ratio of each shielding plate provided in each shielding member. In Table 1, the maximum temperature difference is a value calculated using the method described above. In Table 1, the values ​​of D12 / L1, D12 / L2, D34 / L3, D34 / L4, X1H, and X4H are each values ​​determined using the method described above.

[0083]

[0084] From the results in Table 1, and by comparing Examples 1 to 4 with Examples 5 and 6, it was confirmed that when the relationship of the above formula (x1) is satisfied (the value in the column "(right side) - (left side) of formula (x1)" in Table 1 is positive), heat bias within reaction vessel 10 is suppressed. Furthermore, from a comparison between Examples 1 and 3 and Examples 2 and 4, it was confirmed that heat bias within reaction vessel 10 is further suppressed when the shielding members are a first shielding member, a second shielding member, a third shielding member, and a fourth shielding member, arranged in this order from the gas supply part side to the gas discharge part side of the reaction vessel, the second shielding member and the third shielding member are arranged in an area of ​​the reaction vessel covered by the heater, and the first shielding member and the fourth shielding member are arranged in an area of ​​the reaction vessel not covered by the heater.

[0085] <Formation of Graphene> A rolled copper foil (manufactured by JX Nippon Mining & Metals Corporation) was used as the substrate S1, and graphene was formed on the substrate S1. More specifically, under the conditions of Example 2, a mixed gas of argon gas and hydrogen gas (argon gas: 96.4 vol %, hydrogen gas: 3.6 vol %) was first supplied from the gas supply unit 22 at 500 sccm, and the heater 26 was heated until the temperature measured by a thermocouple installed at the center of the substrate S1 reached 1,050°C. After the temperature of the thermocouple reached 1,050°C, the temperature of the thermocouple was maintained at 1,050°C for 40 minutes.

[0086] Next, the gas being supplied was switched to a source gas containing hydrocarbon. The source gas contained 0.000658 vol% methane gas, 0.911392 vol% hydrogen gas, and 99.087950 vol% argon gas. After switching the gas being supplied to the source gas, the thermocouple temperature was maintained at 1,050°C for 41 minutes. Thereafter, the gas being supplied was switched to a gas containing only argon gas, the output of the heater 26 was set to 0 W, and the inside of the reaction vessel 10 was cooled. After cooling, the substrate S1 was removed from the reaction vessel 10.

[0087] When the surface of the substrate S1 obtained by the above procedure was examined, it was confirmed that a film was attached to the surface. When the film was analyzed by Raman spectroscopy, a single-layer graphene sheet was confirmed. When examined with an optical microscope, it was found that 35.8% of the surface area of ​​the substrate S1 was covered with graphene.

[0088] The entire contents of the specification, claims, drawings and abstract of Japanese Patent Application No. 2023-220821 filed on December 27, 2023 are hereby incorporated by reference as the disclosure of the present invention.

[0089] REFERENCE SIGNS LIST 10 Reaction vessel 11 First shielding member 12 Second shielding member 13 Third shielding member 14 Fourth shielding member 22 Gas supply unit 24 Gas exhaust unit 26 Heater 100 Thermal CVD device 110a, 110b, 110c Shielding plate

Claims

1. A method for manufacturing graphene using a thermal CVD apparatus, wherein the thermal CVD apparatus includes: a cylindrical reaction vessel in which a substrate for graphene production is accommodated; a gas supply unit connected to the reaction vessel and supplying a raw material gas containing hydrocarbon toward the substrate accommodated inside the reaction vessel; a gas discharge unit connected to the side of the reaction vessel opposite to the gas supply unit side and discharging gas from inside the reaction vessel; a heater covering the periphery of a region including the region where the substrate is accommodated in the reaction vessel and heating the inside of the reaction vessel; and a shielding member disposed inside the reaction vessel and blocking heat transfer inside the reaction vessel, the shielding member being disposed at least between the gas supply unit and the substrate and between the substrate and the gas discharge unit, and when the flow rate of the raw material gas introduced from the gas supply unit is W, the internal cross-sectional area of the reaction vessel is S, and the inner diameter of the reaction vessel is x, satisfying the relationship of the following formula (x1). Formula (x1) W / S ≦ 54.97 × exp{−0.128 × (x − 4.0)} In formula (x1), the unit of W is cm ３ / min, representing the gas flow rate per minute converted to the volume value at 1 atm and 0°C. In formula (x1), the unit of S is cm ２ ². In formula (x1), the unit of x is cm.

2. In the reaction vessel, as the shielding members, a first shielding member, a second shielding member, a third shielding member, and a fourth shielding member are arranged in this order from the gas supply part side to the gas discharge part side of the reaction vessel. The second shielding member and the third shielding member are arranged in a region covered by the heater of the reaction vessel. The first shielding member and the fourth shielding member are arranged in a region not covered by the heater of the reaction vessel. The method for producing graphene according to claim 1.

3. The first shielding member, the second shielding member, the third shielding member, and the fourth shielding member each include one or more shielding plates. Each of the shielding plates has one or more holes. The aperture ratio of each of the shielding plates is 0.1 to 40% with respect to the internal cross-sectional area of the reaction vessel. The method for producing graphene according to claim 2.

4. The first shielding member, the second shielding member, the third shielding member, and the fourth shielding member are each formed by arranging two or more of the shielding plates at a constant interval d1. The ratio D12 / d1 of the distance D12 between the first shielding member and the second shielding member to the interval d1, and the ratio D34 / d1 of the distance D34 between the third shielding member and the fourth shielding member to the interval d1 are each 0.03 to 52.

88. The method for producing graphene according to claim 3.

5. When the length of the first shielding member is length L1, the length of the second shielding member is length L2, the length of the third shielding member is length L3, and the length of the fourth shielding member is length L4, the ratio D12 / L1 of the distance D12 to the length L1, and the ratio D12 / L2 of the distance D12 to the length L2 are each 0.01 to 23.

27. The ratio D34 / L3 of the distance D34 to the length L3, and the ratio D34 / L4 of the distance D34 to the length L4 are each 0.01 to 23.

27. The method for producing graphene according to claim 4.

6. When the distance from the end on the gas supply unit side of the region covered by the heater to the first shielding member is defined as distance D1H, the value X1H calculated by the following formula (1) using the distance D12 is 0.01 or more. When the distance from the end on the gas discharge unit side of the region covered by the heater to the fourth shielding member is defined as distance D4H, the value X4H calculated by the following formula (2) using the distance D34 is 0.01 or more. The method for producing graphene according to claim 4 or 5. Formula (1) X1H = (D12 - D1H) / D12 Formula (2) X4H = (D34 - D4H) / D34 7. The method for producing graphene according to claim 6, wherein the value X1H and the value X4H are 0.60 to 1.

00.

8. The opening ratio of the shielding plate in the first shielding member is larger than the opening ratio of the shielding plate in the second shielding member, and the opening ratio of the shielding plate in the fourth shielding member is larger than the opening ratio of the shielding plate in the third shielding member. The method for producing graphene according to any one of claims 3 to 5.

9. The product of the opening ratios of the respective shielding plates constituting the first shielding member and the second shielding member, and the product of the opening ratios of the respective shielding plates constituting the third shielding member and the fourth shielding member are each 0.0009 to 0.0700%. The method for producing graphene according to any one of claims 3 to 5.

10. The second shielding member includes two or more of the shielding plates, and the second shielding member includes the shielding plates having different opening ratios. The third shielding member includes two or more of the shielding plates, and the second shielding member includes the shielding plates having different opening ratios. The method for producing graphene according to any one of claims 3 to 5.

11. The second shielding member includes two or more of the shielding plates, and the aperture ratio of the shielding plate of the second shielding member disposed closest to the third shielding member is smaller than the aperture ratio of the shielding plate of the second shielding member disposed closest to the first shielding member. The third shielding member includes two or more of the shielding plates, and the aperture ratio of the shielding plate of the third shielding member disposed closest to the second shielding member is smaller than the aperture ratio of the shielding plate of the third shielding member disposed closest to the fourth shielding member. The method for manufacturing graphene according to any one of claims 3 to 5.

12. The first shielding member includes two or more of the shielding plates, and the aperture ratio of the shielding plate of the first shielding member disposed closest to the gas supply portion is smaller than the aperture ratio of the shielding plate of the first shielding member disposed closest to the second shielding member. The fourth shielding member includes two or more of the shielding plates, and the aperture ratio of the shielding plate of the fourth shielding member disposed closest to the gas discharge portion is smaller than the aperture ratio of the shielding plate of the fourth shielding member disposed closest to the third shielding member. The method for manufacturing graphene according to any one of claims 3 to 5.

13. The shielding plate includes at least one selected from the group consisting of silicon oxide, silicon nitride, graphite, aluminum oxide, aluminum nitride, tantalum oxide, tantalum carbide, niobium oxide, niobium carbide, and molybdenum oxide. The method for manufacturing graphene according to any one of claims 3 to 5.

14. The second shielding member and the third shielding member are made of metal. The method for manufacturing graphene according to any one of claims 3 to 5.

15. The value obtained by dividing the temperature measured at the following first position by the temperature measured at the following second position is 0.62 or more. The method for manufacturing graphene according to any one of claims 1 to 5. First position: The axial position of the reaction vessel on the surface of the substrate side of the first shielding member. Second position: The axial position of the center of the substrate in the reaction vessel. However, the units of the temperature measured at the first position and the temperature measured at the second position are °C.

16. The inner diameter of the reaction vessel is 12.7 to 38.1 cm. The method for manufacturing graphene according to any one of claims 1 to 5.

17. The method for producing graphene according to any one of claims 1 to 5, wherein the inner diameter of the reaction vessel is 15.24 to 35.56 cm.

18. The method for producing graphene according to any one of claims 1 to 5, wherein the inner diameter of the reaction vessel is 20.32 to 30.48 cm.

19. The method for producing graphene according to any one of claims 1 to 5, wherein the reaction vessel contains silicon dioxide.

20. The method for producing graphene according to any one of claims 1 to 5, wherein the substrate including a metal film containing at least one selected from the group consisting of copper, nickel, and iron is housed in the reaction vessel, a raw material gas containing a hydrocarbon is supplied from the gas supply unit, and the inside of the reaction vessel is heated to 900 to 1,100 °C by the heater to form a graphene layer on the metal film.

Images