Copper base material and laminate

Abstract

Provided is a copper base material capable of generating graphene having a higher single layer ratio than in conventional art. This copper base material has a reduced peak height (Spk) on at least one surface of 0.0475 to 0.0700 μm, and a skewness (Ssk) of -1.0 to less than 0.0.

Description

Copper substrate and laminate

[0001] The present invention relates to a copper substrate and a laminate. In particular, the present invention relates to a copper substrate that, when used in graphene production, can yield graphene with a high monolayer ratio, and a laminate including such a copper substrate.

[0002] Graphite has a layered structure consisting of many flatly arranged layers of six-membered carbon rings stacked on top of each other, and graphene is a material with a single atomic layer to a few atomic layers. Graphene is extremely thin, about 1 nm thick, light, flexible, and transparent, and has the strength of a diamond while being easily bendable. Graphene's electrical conductivity is higher than that of silver, and its thermal conductivity is about 10 times that of copper. In light of these properties, its high chemical and heat resistance have made it attractive as a substitute for silicon and precious metals, and it is therefore attracting attention as a material for batteries, semiconductors, sensors, and other applications.

[0003] A known method for producing graphene is to peel off graphite with adhesive tape (a so-called "top-down" production method). However, this method has problems such as the number of graphene layers being inconsistent, making it difficult to obtain large-area graphene, and being a batch process, which makes it unsuitable for mass production.

[0004] Meanwhile, a so-called "bottom-up" manufacturing method is known, which involves contacting a carbon-based substance with a sheet-like single-crystal graphitizing metal catalyst and then heat-treating the catalyst to grow a graphene sheet (chemical vapor deposition (CVD) method) (Patent Document 1). Metal substrates such as Ni, Cu, and W are disclosed as examples of this single-crystal graphitizing metal catalyst. In bottom-up CVD manufacturing methods, productivity can be improved by using a roll-to-roll process that uses a substrate.

[0005] JP 2009-143799 A

[0006] In bottom-up manufacturing methods such as CVD, copper substrates are considered preferable as graphene growth catalysts because they do not dissolve carbon derived from graphene precursor gases, but they have not yet achieved high-quality graphene and have not yet been put into full-scale mass production. Generally, graphene synthesized by CVD has a low monolayer ratio, which hinders electron transfer due to interactions between layers, resulting in a significant decrease in carrier mobility.

[0007] The present invention has been completed in view of the above-mentioned problems, and an object of the present invention is to provide a copper substrate capable of producing graphene with a higher single-layer ratio than conventional techniques in one embodiment of the present invention. In another embodiment, an object of the present invention is to provide a laminate including such a copper substrate.

[0008] As a result of extensive research, the present inventors have found that controlling the peak height (Spk) and skewness (Ssk) of the surface of a copper substrate is effective as a copper substrate characteristic for increasing the monolayer rate of graphene. By controlling the Spk and Ssk of a copper substrate within an appropriate range, when the copper substrate is used to produce graphene, the monolayer rate of the produced graphene is higher than that of conventional techniques, thereby expanding the possibility of mass production of high-quality graphene. The present invention has been completed based on the above findings, and is exemplified below.

[0009] [1] A copper base material having a peak height (Spk) of 0.0475 μm or more and 0.0700 μm or less on at least one surface, and a skewness (Ssk) of −1.0 or more and less than 0.0. [2] The rolled copper base material according to [1], wherein the Ssk is −0.6 or more and less than 0.0. [3] The rolled copper base material according to [1], wherein the Ssk is −0.7 or more and less than 0.0. [4] The copper base material according to any one of [1] to [3], which is used for producing graphene. [5] A laminate obtained by laminating graphene on at least one surface of the copper base material according to any one of [1] to [4]. [6] A relative intensity ratio I of the 2D band to the G band of the graphene measured by Raman spectroscopy. 2D / I G[7] A laminate according to [5], wherein a relative intensity ratio I of the 2D band to the G band of the graphene measured by Raman spectroscopy is 2.0 or more. 2D / I G a laminate having a peak height (Spk) of 2.0 or more. "8" A method for producing graphene, comprising the steps of: preparing a copper base having a peak height (Spk) of 0.0475 μm or more and 0.0700 μm or less on at least one surface; placing the copper base under a reaction gas containing a graphene precursor gas; and reacting the reaction gas on the at least one surface of the copper base at 1000°C to 1085°C. [9] A method for producing graphene according to [8], further comprising: a surface skewness (Ssk) of -1.0 or more and less than 0.0.

[10] A method for producing graphene according to [9], wherein the Ssk is -0.7 or more and less than 0.0.

[11] A method for producing graphene according to [9], wherein the Ssk is -0.6 or more and less than 0.0.

[12] A method for producing a laminate, comprising the step of bonding graphene produced by the method according to any one of [8] to

[11] , and a semiconductor base.

[0010] According to an embodiment of the present invention, a copper substrate capable of producing graphene with a higher monolayer ratio than conventional techniques can be provided. Also, according to an embodiment of the present invention, a laminate including such a copper substrate can be provided.

[0011] Next, embodiments of the present invention will be described. The present invention is not limited to the following embodiments, and it should be understood that appropriate design changes, improvements, and the like can be made based on the common knowledge of those skilled in the art without departing from the spirit of the present invention. The multiple components disclosed in the following embodiments can be appropriately combined to form various inventions. For example, some components may be deleted from all of the components shown in the following embodiments, or components from different embodiments may be appropriately combined. In this specification, "ppm" and "%" are expressed by mass unless otherwise specified. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits, unless otherwise specified. In this specification, a numerical range with "greater than" or "less than" attached to a numerical value means a range that does not include the numerical value as the lower or upper limit. Regarding numerical ranges described in stages in this specification, the upper limit of a certain numerical range may be replaced with the upper limit of another numerical range described in stages or a value shown in an example. Furthermore, in the numerical ranges described in stages in this specification, the lower limit value of a certain numerical range may be replaced with the lower limit value of another numerical range described in stages or a value shown in an example.

[0012] (Composition of copper substrate) There is no particular limitation on the form of the copper substrate that can be used in this embodiment. Typically, the copper substrate used in the present invention is copper foil. Copper foils are broadly divided into two types: rolled copper foils and electrolytic copper foils. Generally, rolled copper foils are manufactured by repeatedly performing plastic working using rolling rolls and heat treatment. Rolled copper foils are often used in applications that require flexibility.

[0013] In addition, in this specification, the term "copper substrate" means a substrate that is formed independently, and does not include copper formed depending on another substrate, such as plated copper formed on a resin carrier.

[0014] As the material for the copper substrate, in addition to commonly used high-purity copper such as tough pitch copper or oxygen-free copper, copper alloys such as Sn-containing copper, Ag-containing copper, copper alloys containing P, Cr, Zr, Mg, etc., and Corson copper alloys containing Ni, Si, etc., can also be used. In this specification, when the term "copper substrate" is used alone, it also includes copper alloy substrates.

[0015] The thickness of the copper substrate is not particularly limited, but may be, for example, 1 to 1000 μm, alternatively 1 to 500 μm, alternatively 1 to 300 μm, alternatively 3 to 100 μm, alternatively 5 to 70 μm, alternatively 6 to 35 μm, or alternatively 9 to 18 μm.

[0016] The copper substrate of the present embodiment can be suitably used for producing graphene, typically, for producing graphene by a CVD method.

[0017] The copper substrate of this embodiment has a protruding peak height (Spk) of 0.0475 μm or more and 0.0700 μm or less on at least one surface. Spk represents the average height of the protruding peaks in a target region on the surface, and the higher Spk, the higher the average height of the protruding peaks. The copper substrate of this embodiment has a skewness (Ssk) of -1.0 or more and less than 0.0 on at least one surface. Ssk represents the symmetry of the height distribution in a target region on the surface, and when Ssk is 0, the height distribution is symmetrical from top to bottom, and when Ssk > 0, the surface has more peaks than valleys. When Ssk < 0, the surface has more valleys than peaks. The inventors have discovered that when the surface of a copper substrate has an Spk of 0.0475 μm or more and 0.0700 μm or less and an Ssk of -1.0 or more and less than 0.0, the monolayer ratio of graphene formed on the surface can be increased. Furthermore, it was also discovered that when Ssk is -1.0 or more and less than 0.0, defects in the graphene formed on the surface can be reduced. In other words, it was discovered that a copper substrate surface with more valleys than peaks is advantageous for forming graphene with fewer defects. The lower limit of Ssk is preferably -0.9 or more, more preferably -0.8 or more, even more preferably -0.7 or more, and even more preferably -0.6 or more. A preferred range for Ssk is -0.9 or more and less than 0.0, more preferably -0.7 or more and less than 0.0, and even more preferably -0.6 or more and less than 0.0.

[0018] As described below, Spk and Ssk are calculated after measuring the roughness data of the copper substrate surface using a Keyence laser microscope VK-X1000 (controller unit) / 1050 (head unit) or an equivalent device in accordance with ISO 25178-2: 2012. As described above, Spk and Ssk are important parameters for increasing the monolayer rate when graphene is grown on the surface of a copper substrate. Therefore, when a surface treatment is performed on a copper substrate, Spk and Ssk are measured for the copper substrate before the surface treatment.

[0019] The surface treatment layer may include one or more layers selected from the group consisting of a heat-resistant layer, an anti-rust layer, a chromate treatment layer, and a silane coupling treatment layer. These layers can be provided using known techniques. An anti-rust layer is particularly preferred. As the anti-rust layer, the compound that forms a complex with copper and has a boiling point of 200-1000°C is not particularly limited as long as it is a compound that can react with copper to form a complex, and examples thereof include nitrogen-containing heterocyclic compounds. The nitrogen-containing heterocyclic compound is not particularly limited, and examples thereof include nitrogen-containing heterocyclic aromatic compounds in which a benzene ring and a nitrogen-containing heterocycle are bonded together and share one side. The nitrogen-containing heterocyclic aromatic compound in which a benzene ring and a nitrogen-containing heterocycle are bonded together by sharing one side is not particularly limited, but examples thereof include benzoxazole, compounds having a benzoxazole skeleton (benzoxazole derivatives), benzotriazole, compounds having a benzotriazole skeleton (benzotriazole derivatives), benzothiazole, compounds having a benzothiazole skeleton (benzothiazole derivatives), and benzimidazole, compounds having a benzimidazole skeleton (benzimidazole derivatives). Benzotriazole and carboxybenzotriazole are particularly preferred. The benzoxazole derivative is not particularly limited as long as it is a compound having a benzoxazole skeleton, but examples thereof include 2-mercaptobenzoxazole.The benzotriazole derivative is not particularly limited as long as it is a compound having a benzotriazole skeleton, and examples thereof include 1,2,3-benzotriazole, 1,2,3-benzotriazole sodium salt, carboxybenzotriazole, carboxybenzotriazole phenyl ester, carboxybenzotriazole methyl ester, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)benzotriazole, 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-tert-octylphenol], 6-(2-benzotriazolyl)-4-tert-octyl-6'-tert-butyl-4'-methyl-2,2'-methylenebisphenol, 1-[N,N-bis(2-ethylhexyl)aminomethyl]methylbenzotriazole, 2,2'-[(methyl-1H-benzotriazol-1-yl)methyl]iminobisethanol, and the like. The benzothiazole derivative is not particularly limited as long as it is a compound having a benzothiazole skeleton, and examples thereof include 2-mercaptobenzothiazole, 2-(methylthio)-2-benzothiazole, dodecanethioic acid S-benzothiazol-2-yl ester, dibenzyldithiocarbamic acid benzothiazol-2-yl ester, 1-(1,2-benzisothiazol-3-yl)piperazine, N,N-bis(2-ethylhexyl)-2-benzothiazolylsulfenamide, 2-(2-hydroxyphenyl)benzothiazole, benzothiazylthio-propionic acid, 3-(2-benzothiazylthio)propionic acid, and 2-aminobenzothiazole.The benzimidazole derivative is not particularly limited as long as it is a compound having a benzimidazole skeleton, and examples thereof include 2-mercaptobenzimidazole, 2-mercapto-5-methoxybenzimidazole, 2-mercapto-carboxybenzimidazole, 1,3-dihydro-1-phenyl-2H-benzimidazole-2-thione, 2-mercapto-5-nitrobenzimidazole, and 2-mercapto-5-aminobenzimidazole. These compounds may be used alone or in combination of two or more. Benzotriazole and carboxybenzotriazole are particularly preferred.

[0020] The anticorrosion layer is formed on the surface of the copper substrate of this embodiment by immersing the copper substrate in a solution in which the organic substance is dissolved in a polar solvent and then drying. By using an organic substance with a boiling point of 200 to 1000°C as the anticorrosion agent, the anticorrosion agent is removed from the copper substrate surface together with the attached organic substance during pretreatment for graphene deposition, and the copper substrate is exposed to the source gas during the graphene deposition stage, making it easier to form a graphene film with low defects.

[0021] A laminate in which graphene is laminated can be produced by growing graphene on at least one of the surfaces of the copper substrate of this embodiment by a CVD method or the like. Specifically, the rolled copper substrate of this embodiment is placed under a reaction gas containing a graphene raw material gas. The graphene raw material gas may be a hydrocarbon gas. The reaction gas may contain hydrogen gas and a carrier gas. An example of the carrier gas is argon gas. The reaction gas is then reacted on the copper substrate at a reaction temperature to obtain graphene.

[0022] It is preferable to include a step of removing organic contaminants and the anticorrosive layer by heating the copper substrate of this embodiment to 1000°C or higher under a vacuum, an inert gas, or a weakly reducing atmosphere. This treatment is more preferable because it enables the removal of the oxide layer formed on the surface of the rolled copper substrate. The reaction temperature is preferably between 1000°C and 1085°C. The reaction temperature refers to the temperature of the reaction gas. Graphene film formation may be performed using a conveying system or a batch system, but it can be said that the conveying system film formation method has higher productivity. In the conveying system film formation method, the source gas and hydrogen may be sprayed on one side or both sides of the copper substrate. In the conveying system, by sufficiently separating the position where heating to 1000°C from the position where the source gas and hydrogen gas are sprayed, impurities can be avoided from being mixed into the source gas, and graphene with fewer defects can be obtained. In the case of the batch method, the copper substrate is heated to 1000°C and a sufficient time is allowed before the raw material gas and hydrogen gas are sprayed, or the atmosphere is temporarily evacuated, thereby preventing impurities from being mixed into the raw material gas and producing graphene with fewer defects.

[0023] Graphene can be peeled or transferred from the copper substrate and graphene laminate by a known method and further laminated on a target substrate such as another semiconductor substrate to produce a laminate. The other target substrate can be any semiconductor. Examples of semiconductors include Si, SiC, GaN, SiN, and GaO. ３ , GeO, diamond, MoS, WS, TiS, ZrS, HfS, ReS, SnS, FeS, NiS, GeS, SnS, BiS, PtS, TaS, NbS, MoSe, WSe, InSe, InSe, BiSe, GeSe, TaSe, NbSe, VSe, GeTe, SbTe, BiTe, PdTe, MoO, WO, TiC, and TiN. These semiconductors may be used alone or in combination with two or more semiconductors to form a laminate having the graphene obtained in this embodiment sandwiched therebetween.

[0024] In this specification, a high single-layer ratio of graphene means high carrier mobility. When graphene is multi-layered, carriers not only move within a plane but also move between layers, resulting in a decrease in carrier mobility in the entire multi-layer graphene. On the other hand, in single-layer graphene, carrier movement within a plane is dominant, resulting in a high carrier mobility as single-layer graphene. The single-layer ratio of graphene is determined by the 2D band (2680 cm) of graphene measured by Raman spectroscopy. -1 (nearby) and G band (1580 cm -1 Relative intensity ratio I 2D / I G In this specification, a high monolayer ratio of graphene can be evaluated by the ratio I 2D / I G It means that the ratio I is 2.0 or more. 2D / I G is 2.1 or more, and more preferably, the ratio I 2D / I G is 2.2 or more, and even more preferably, the ratio I 2D / I G is 2.3 or more, and even more preferably, the ratio I 2D / I G is 2.4 or more, and even more preferably, the ratio I 2D / I G The Raman spectroscopy analysis conditions are as follows: In this specification, the graphene has few defects when the D band (1380 cm) of graphene measured by Raman spectroscopy is small. －１ (nearby) and G band (1580 cm －１ This means that the relative intensity ratio I D / I G of the two peaks (near each other) is 0.20 or less. Preferably, the ratio I D / I G is 0.19 or less, more preferably, the ratio I D / I G is 0.18 or less, even more preferably, the ratio I D / I G is 0.17 or less, even more preferably, the ratio I D / I G is 0.16 or less, and even more preferably, the ratio I D / I G is 0.15 or less.

[0025] The graphene film formed on the copper substrate was transferred to a silicon wafer with an oxide film. The graphene transferred to the wafer was then subjected to Raman spectroscopy at 1,200 points within a measurement area of ​​80 μm × 40 μm using an excitation light wavelength of 532 nm.

[0026] (Manufacturing Method) The manufacturing method of the copper base material of this embodiment is not particularly limited as long as the above-mentioned Spk and Ssk can be controlled within the range of this embodiment. However, as a method that can easily manufacture the copper base material without surface treatment, a method of rolling an ingot of copper or a copper alloy can be adopted.

[0027] In the method for producing a copper substrate according to this embodiment, raw materials are first melted in a melting furnace to obtain a molten metal having a desired composition. This molten metal is then cast into an ingot. Subsequently, hot rolling, cold rolling, and annealing are appropriately performed to finish the material into a foil having a predetermined thickness. After the heat treatment, the surface may be pickled or polished to remove any surface oxide film formed during the heat treatment. In the final cold rolling, the heat-treated material is repeatedly passed through a rolling mill to finish the material to a predetermined thickness. In the method for producing a copper substrate according to this embodiment, it is important that the parameter t, expressed by the following formula, in the final rolling pass of the final cold rolling step falls within the range of 50 to 180. Parameter t = (rolling oil viscosity [cst]) × {(roll peripheral speed [mm / s]) + (entrance side passing speed [mm / s])} / [(roll bite angle [rad]) × {(rolling load per unit area [MPa]) - (back tension [MPa])}]

[0028] The rolling oil viscosity is measured in accordance with JIS-K2283. The entry-side threading speed is calculated from the peripheral speed of the exit-side take-up reel, taking into account the rolling reduction rate of the corresponding rolling pass. The roll peripheral speed is calculated from the peripheral speed of the exit-side take-up reel, assuming no slippage between the roll and the material. The roll engagement angle is calculated using the following formula. The Young's modulus and Poisson's ratio of the roll were determined using the values ​​listed in the roll manufacturer's catalog and the literature values ​​for the roll material. The roll radius was obtained by measuring the diameter using a roll diameter measuring device capable of measuring to 0.0005 mm. The rolling load was calculated from the pressure measured by the hydraulic sensor of the rolling machine's hydraulic cylinders, using the diameter and number of cylinders. The reduction was calculated from the material thickness before and after threading. The material thickness can be measured, for example, in accordance with the mass thickness measurement method of JIS-C6515. Roll bite angle={(roll reduction amount [mm] / (roll flattening radius [mm])} 0.5 Roll flattening radius = (roll radius [mm]) x [1 + 16 x {1 - (roll Poisson's ratio)} 2} / {π×(Young's modulus of roll [kg / mm 2 ])} × (rolling load [kg]) / {average plate thickness [mm]) × (rolling reduction [mm])}] The rear tension is calculated from the outer diameter of the coil during rolling, the torque current value of the reel drive motor on the unwinding side, and the cross-sectional area of ​​the material on the inlet side.

[0029] The present invention will be specifically described below with reference to examples, but the description here is for the purpose of illustration only and is not intended to be limiting.

[0030] (Copper Base Material According to Examples) First, for Examples 1 and 2, an ingot of copper or copper alloy with a copper content of 99.9% was produced and hot-rolled. Then, cold-rolling and annealing in an annealing furnace set at a temperature of 300 to 800°C were repeated at least once, followed by cold-rolling to obtain a rolled plate with a thickness of 0.1 to 1.0 mm. This rolled plate was annealed in an annealing furnace set at a temperature of 300 to 800°C for recrystallization, and finally cold-rolled. As a result, rolled copper foils with a thickness of 0.012 mm and parameter t of 125 (Example 1) and 73 (Example 2) were obtained. After removing rolling oil from the surface of the obtained rolled copper foil using normal paraffin, the rolled copper foil was immersed for 20 seconds in a benzotriazole aqueous solution with a concentration of 0.02%, a solution temperature of 45°C, and a pH of 6.5 to 8.0, and the rolled copper foil was dried.

[0031] (Copper substrate according to reference examples) A ​​tough pitch copper ingot was produced and subjected to hot rolling, cold rolling, etc. to obtain a rolled copper foil (Reference Example 1) having a parameter t of 210. Furthermore, a rolled copper foil (Reference Example 2) was obtained in the same manner as in Example 1, except that the parameter t was set to 183. The rolling oil was removed from the obtained rolled copper foil in the same manner as in Examples 1 and 2, and the foil was treated with an aqueous benzotriazole solution.

[0032] The rolled copper foils of the Examples and Reference Examples prepared as described above were used as copper substrates and various evaluations were carried out as follows. The results are shown in Table 1.

[0033] (Measurement of protruding peak height (Spk) and skewness (Ssk)) Shape measurement was carried out using a Keyence laser microscope VK-X1000 (controller unit) / 1050 (head unit). Thereafter, Spk and Ssk were measured using analysis software (multi-file analysis application, Ver. 2.1.1.111) for the Keyence laser microscope VK-X1000 (controller unit) / 1050 (head unit). At this time, a 1 mm × 1 mm area (specifically, 1 mm 2) was measured. In order to eliminate the influence of tilt and waviness of the surface of the workpiece when it was placed during shape measurement, Spk and Ssk were calculated after performing plane tilt correction and waviness removal (correction strength 5) as surface shape correction for the measurement area during analysis using analysis software. The environmental temperature for measuring Spk using a laser microscope was set to 20 to 25°C. The main setting conditions for the laser microscope and analysis software are as follows: <Measurement settings> Measurement mode: Basic measurement Scan mode: Laser confocal Measurement size: Standard (1024 x 768) Measurement quality: High precision Measurement pitch: 0.13 μm RPD: ON Brightness 1: Approximately 6500 to 7500 (varies with fine focus adjustment) Brightness 2: OFF Lighting filter 1: Approximately 10 to 30% (varies with fine focus adjustment) Lighting filter 2: OFF Double scan: OFF Number of averages: 1 Do not acquire color images: OFF Fine mode: ON Enable noise area processing: OFF <Lighting> Coaxial incident illumination: 100 Ring illumination: OFF <Z axis> Z axis mode: Recommended settings Upper measurement limit: Approximately 9900 to 10100 μm (varies with fine focus adjustment) Lower measurement limit: Approximately 10000 to 10100 μm (varies with fine focus adjustment) Fixed Z measurement distance: OFF <Camera settings> Brightness mode: Auto Brightness (auto): Approximately 120 to 140 (varies with fine focus adjustment) Edge emphasis: 5 <Laser settings> Gamma coefficient (gamma correction value): 0.45 Gamma offset: 0% Black and white inversion: OFF Edge emphasis type: None Edge emphasis direction: Horizontal Edge emphasis strength: Weak <Other condition settings shown on the worksheet> Measurement mode: Surface profile Optical zoom magnification: 1.0x Filter: OFFCamera gain: 0 dB Shutter speed: Auto White balance mode: Manual White balance R: 0 White balance B: 0 Received light intensity correction mode: γ correction Head type: VK-X105 Vividness: 5 Contrast: 5 Brightness: 0 AI noise reduction: OFF Slope noise filter: OFF <Analysis conditions> Image processing: Surface shape correction performed (plane tilt correction, waviness removal (correction strength 5)) Surface roughness settings (filter settings) Filter type: Gaussian S-filter (low-pass filter): None F-operation (shape correction): None L-filter (high-pass filter): None End effect correction: ON

[0034] (Method for Producing Graphene) Each copper substrate according to the Examples and Reference Examples was cut out (50 x 50 mm) and placed at the center of the diameter of a 200 mm tubular furnace. While flowing a gas containing 2.5 vol% hydrogen and the remainder argon, the temperature was increased from room temperature to 1000°C over 40 minutes, and then maintained at 1000°C for 40 minutes. Thereafter, while flowing a gas of the same composition, the temperature was increased to 1075°C over 20 minutes, and methane was introduced so that the mixture was 2.5 vol% hydrogen, 10 ppm methane, and the remainder argon, and the temperature was maintained for 90 minutes. Thereafter, the mixture was allowed to cool over 120 minutes while flowing a gas containing 2.5 vol% hydrogen and the remainder argon, and graphene was grown on the surface of the copper substrate. The flow rate of the gas of each composition was 400 mL / min.

[0035] (Analysis by Raman Spectroscopy) The graphene obtained on the sample of each Example and Reference Example was analyzed by Raman spectroscopy under the following conditions, and the 2D band (2680 cm) of graphene was measured. -1 (nearby) and G band (1580 cm -1 Relative intensity ratio I 2D / I G and D band (1380 cm -1 (nearby) and G band (1580 cm -1 Relative intensity ratio I D / I G Measurement device: Nanofinder 30 (Tokyo Instruments) Excitation light wavelength: 532 nm Measurement range: 80 μm × 40 μm I2D / I G : Intensity I of the 2D band at each of the 1200 points in the above range 2D , D-band intensity I D , and the G-band intensity I G I 2D / I G and I 2D / I G The arithmetic mean value of 1200 points was calculated. The measurement results are shown in Table 1.

[0036]

[0037] (Discussion) In Examples 1 and 2, the Spk of the copper substrate surface was 0.0475 μm or more and 0.0700 μm or less, and the Ssk was −1.0 or more and less than 0.0, so that good-quality graphene with a high graphene monolayer rate and few defects could be obtained. On the other hand, in Reference Examples 1 and 2, the surface Spk and Ssk did not satisfy the above-mentioned ranges, so that the graphene monolayer rate was lower than in Examples 1 and 2.

[0038] (Potential Contribution to SDGs) According to one embodiment of the present invention, a copper substrate capable of producing graphene with a higher single-layer rate than conventional techniques can be provided, which may contribute to the miniaturization and / or high performance of electronic devices. In order to realize an AI / IoT society, miniaturization and / or high performance of electronic devices are required. Therefore, one embodiment of the present invention may contribute to Goal 9 of the Sustainable Development Goals (SDGs) led by the United Nations, which is to "Build resilient infrastructure, promote inclusive and sustainable industrialization, and foster innovation."

Claims

1. A copper base material having a peak height (Spk) of at least one surface of 0.0475 μm or more and 0.0700 μm or less, and a skewness (Ssk) of -1.0 or more and less than 0.

0.

2. The copper substrate according to claim 1, wherein the Ssk is greater than or equal to -0.6 and less than 0.

0.

3. A laminate in which graphene is laminated on the surface of the copper substrate according to claim 1.

4. The relative intensity ratio I of the 2D band and the G band of the graphene measured by Raman spectroscopy 2D / I G The laminate according to claim 3, wherein the σ is 2.0 or more.

5. A stack having a semiconductor and graphene, wherein the relative intensity ratio I of the 2D band to the G band of the graphene measured by Raman spectroscopy 2D / I G The laminate has a value of 2.0 or more.

6. A method for producing graphene, comprising the steps of: preparing a copper base having a peak height (Spk) of 0.0475 μm or more and 0.0700 μm or less on at least one surface; placing the copper base under a reaction gas containing a graphene precursor gas; and reacting the reaction gas on the surface of the copper base at 1000°C to 1085°C.

7. The graphene production method according to claim 6, further comprising the step of: providing the surface skewness (Ssk) of -1.0 or more and less than 0.

0.

8. The graphene production method according to claim 7, wherein the Ssk is equal to or greater than -0.6 and less than 0.

0.

9. A method for producing a laminate, comprising a step of bonding graphene produced by the method according to any one of claims 6 to 8 to a semiconductor substrate.

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