Laminate and method for manufacturing laminate

Abstract

Provided is a laminate having a high graphene-film single layer ratio.　A laminate has a metal film that contains copper, and a graphene film that is adjacent to the metal film, the metal film having a first direction that satisfies requirement 1 in an in-plane direction.　Requirement 1: The volume fraction of crystals in which the orientation direction of the crystals is the <100> direction is 55% or greater when the first direction is the [100] direction and pole point measurement by X-ray diffraction is performed.

Description

Laminate and method for manufacturing laminate

[0001] The present invention relates to a laminate and a method for manufacturing the laminate, more particularly to a laminate having a graphene film and a method for manufacturing the laminate.

[0002] Graphene is one of the allotropes of carbon. ２ Graphene is a sheet-like substance bound together by bonds, and graphite is made up of stacked graphene sheets. Graphene has a hexagonal lattice structure (hexagonal mesh plane) formed by carbon atoms and their bonds.

[0003] Graphene has been reported to have carrier mobilities that exceed those of silicon (Si) and gallium arsenide (GaAs), and its application to devices such as biosensors, optical sensors, electromagnetic wave sensors, transistors, metasurfaces, and transparent electrodes is being considered.

[0004] A known method for producing graphene is to supply carbon-containing molecules such as methane to the surface of a copper-containing metal film and form a graphene film by thermal chemical vapor deposition. It is well known that the properties of the formed graphene film depend on the properties of the metal film that serves as the substrate. Here, Non-Patent Document 1 describes a method for obtaining a single-crystal metal foil by "contact-free annealing."

[0005] Sunghwan Jin, et al., "Colossal grain growth yields single-crystal metal foils by contact-free annealing", Science, 30 November 2018, 362, p.1021-1025

[0006] Considering the device applications of graphene, it is preferable to obtain a single-layer graphene film. The present inventors annealed a copper foil by the method described in Non-Patent Document 1, and formed a graphene film by thermal chemical vapor deposition using the annealed copper foil as a substrate. They found that there was room for improvement in the single-layer ratio of the formed graphene film (the ratio of single-layer graphene film to the formed graphene film). That is, the present inventors found that there was room for improvement in the single-layer ratio of the graphene film in a laminate having a metal film and a graphene film adjacent to the surface of the metal film.

[0007] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a laminate having a high single-layer ratio of graphene films. Another object of the present invention is to provide a method for producing a laminate by which a laminate having a high single-layer ratio of graphene films can be obtained.

[0008] As a result of extensive research into the above-mentioned problems, the present inventors have found that a laminate having a metal film in a predetermined orientation state has a high single-layer ratio of graphene films, leading to the completion of the present invention.

[0009] That is, the inventors have found that the above-mentioned problems can be solved by the following configuration. [1] A laminate having a metal film containing copper and a graphene film adjacent to the metal film, wherein the metal film has a first direction in an in-plane direction that satisfies the following requirement 1. Requirement 1: When the first direction is the

[100] direction and pole point measurement is performed by X-ray diffraction, the volume fraction of crystals whose orientation direction is the <100> direction is 55% or more. [2] The laminate according to [1], which satisfies the following requirement 2. Requirement 2: When the first direction is the

[100] direction and pole point measurement is performed by X-ray diffraction, the volume fraction of crystals whose orientation direction is the <100> direction is 60% or more. [3] The laminate according to [1] or [2], wherein the metal film is a copper foil, and the angle between the first direction and the rolling direction of the copper foil is 0 to 10° or 80 to 90°. [4] The laminate according to any one of [1] to [3], wherein the metal film is a copper foil, and the angle between the first direction and the rolling direction of the copper foil is 0 to 10°. [5] The laminate according to any one of [1] to [4], wherein the graphene film has a single-layer ratio of 95% or more. [6] The graphene film has a G-band peak intensity I obtained by Raman spectroscopy. Ｇ The peak intensity of the 2D band I ２Ｄ Intensity ratio I ２Ｄ / I Ｇ The average value of the intensity ratio I is 1.75 or more, ２Ｄ / I Ｇ

[0023]

[0024] The laminate according to any one of [1] to [5], wherein the standard deviation of ...

[10] The method for producing a laminate according to [9], wherein the metal film is a copper foil, and the metal film is heated in a state in which the angle between the rolling direction of the copper foil and the direction of gravity is 0 to 10° or 80 to 90°.

[11] The method for producing a laminate according to any one of [8] to

[10] , wherein the metal film is subjected to an oxidation treatment before being heated.

[12] The method for producing a laminate according to any one of [8] to

[11] , wherein preheating is performed before the formation of graphene by the thermal chemical vapor deposition method, and the metal film is heated while applying tensile stress by the preheating.

[13] The method for producing a laminate according to

[12] , wherein the preheating time is 1 hour or more.

[14] The method for producing a laminate according to

[12] or

[13] , wherein the preheating temperature is 1000°C or more.

[15] The method for producing a laminate according to any one of [7] to

[14] , wherein the graphene film is formed by thermal chemical vapor deposition at 1050° C. or higher.

[0010] According to the present invention, it is possible to provide a laminate having a high single-layer ratio of graphene films. Also, according to the present invention, it is possible to provide a method for producing a laminate, which can obtain a laminate having a high single-layer ratio of graphene films.

[0011] 1 is a schematic cross-sectional view of an embodiment of the laminate of the present invention, and is a view for explaining a region of the laminate where Raman spectroscopy is performed.

[0012] The present invention will be described in detail below. The following description of the components may be based on representative embodiments of the present invention, but the present invention is not limited to such embodiments.

[0013] The meanings of terms used in the present invention 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.

[0014] In this specification, a notation including three integers written in parentheses refers to a specific plane expressed in Miller indices. For example, an (hkl) plane refers to a specific plane expressed in Miller indices h, k, and l. In addition, in this specification, a notation including three integers written in curly brackets refers to a notation that collectively represents equivalent planes in the crystal system. For example, the {100} plane in a cubic crystal is a notation that collectively represents six equivalent directions: the (100) plane, the (010) plane, the (001) plane, the (-100) plane, the (0-10) plane, and the (00-1) plane. In addition, in this specification, a notation including three integers written in square brackets refers to a specific direction expressed in Miller indices. For example, the [hkl] direction refers to a specific direction expressed in Miller indices h, k, and l. In the case of a cubic crystal, the [hkl] direction is parallel to the normal direction of the (hkl) plane. In this specification, notations including three integers in angle brackets are notations that summarize equivalent directions in the crystal system. For example, the <100> direction in a cubic crystal is a notation that summarizes six equivalent directions: the

[100] direction, the

[010] direction, the

[001] direction, the [-100] direction, the [0-10] direction, and the [00-1] direction. Furthermore, the term "hkl diffraction line" refers to a diffraction line derived from the (hkl) plane.

[0015] In this specification, "XRD" is an abbreviation for X-ray diffraction. In this specification, an "XRD chart" is a chart (diagram) obtained by performing an XRD measurement, in which the horizontal axis represents the angle and the vertical axis represents the detected intensity of the X-rays. "Out-of-plane XRD" is a method of obtaining an XRD chart by rotating the detector of the incident direction of the X-rays and the diffracted X-rays around an axis parallel to the surface of the measurement sample. In out-of-plane XRD, diffraction lines from lattice planes approximately parallel to the surface of the measurement sample are easily obtained. Note that out-of-plane XRD is also called θ-2θ scanning.

[0016] <Laminate> The laminate of the present invention includes a metal film containing copper and a graphene film adjacent to the metal film. In the laminate of the present invention, the metal film has a first in-plane direction that satisfies the following requirement 1: Requirement 1: When the first direction is defined as the

[100] direction and pole point measurement is performed by X-ray diffraction, the volume fraction of crystals whose orientation direction is the <100> direction is 55% or more.

[0017] Fig. 1 shows a schematic cross-sectional view of one embodiment of a laminate of the present invention. The laminate 10 shown in Fig. 1 comprises a metal film 12 and a graphene film 14 adjacent to the surface of the metal film 12. The metal film 12 has the first direction described above.

[0018] Although the mechanism by which the monolayer ratio of the graphene film increases in a laminate of the present invention having a metal film and a graphene film adjacent to the surface of the metal film is not entirely clear, the inventors speculate as follows. The metal film of the laminate of the present invention has a first direction that satisfies the above-mentioned requirement 1. By performing pole point measurement using X-ray diffraction with the first direction as the

[100] direction, the crystal orientation direction that generates the diffraction line of each crystal plane and the volume fraction of the crystal can be calculated. In the laminate of the present invention, the volume fraction of crystals whose crystal orientation direction is the <100> direction is 55% or more using the above-mentioned method. When the volume fraction is 55% or more, it is thought that many crystals in the metal film are growing along the first direction, and that crystal grain domains on the surface of the metal film often grow with their crystal grains facing a predetermined direction. The graphene film grows on the surface of the metal film, and when the metal film has many crystal grain domains and these domains face multiple directions, many crystal grain boundaries are likely to be present. It is presumed that the presence of grain boundaries makes it easy for defects to occur in the graphene film starting from the grain boundaries, and that multilayer growth is likely to occur. On the other hand, when the domains of the crystal grains grow in a predetermined direction as in the laminate of the present invention, it is thought that the number of grain boundaries that are likely to cause defects or multilayer growth is likely to decrease, resulting in a high single-layer ratio of the graphene film.

[0019] The laminate of the present invention will be described below. Hereinafter, in a laminate having a metal film and a graphene film adjacent to the surface of the metal film, a high monolayer rate of the graphene film will also be simply referred to as "a high monolayer rate of the graphene film." The laminate of the present invention can be produced by a first embodiment or a second embodiment of the method for producing a laminate of the present invention, which will be described later.

[0020] [Metal Film] The metal film of the laminate of the present invention contains copper, and has a first direction in its in-plane direction that satisfies the above-mentioned requirement 1. Hereinafter, the first direction that satisfies the above-mentioned requirement 1 will be described. The first direction is one of the in-plane directions of the metal film. Whether or not an arbitrary in-plane direction of the metal film is the first direction, that is, whether or not an arbitrary in-plane direction of the metal film satisfies requirement 1, is determined by pole measurement using X-ray diffraction according to the following procedure. Hereinafter, the direction in which it is confirmed whether or not an arbitrary in-plane direction of the metal film is the first direction will also be referred to as the "measurement direction."

[0021] First, a measurement direction is determined, which is one of the in-plane directions of the metal film. The measurement direction is defined as the

[100] direction. Furthermore, the in-plane direction of the metal film that is perpendicular to the measurement direction is defined as the

[010] direction, and the direction perpendicular to the surface of the metal film is defined as the

[001] direction. The

[100] ,

[010] , and

[001] directions are defined so that, when the x-axis, y-axis, and z-axis are defined in this order, the three directions form a right-handed system. Next, the X-ray incidence angle and the angle of the X-ray detector are determined so that the positional relationship of the diffraction lines from the previously measured fundamental index planes is achieved. More specifically, when the incidence direction of the X-rays on the surface of the metal film is defined as θ°, the positional relationship is determined so that the detection angle of the detector is 2θ° relative to the incidence direction of the X-rays. The diffraction lines from the fundamental index planes are, for example, the 200 diffraction line, the 111 diffraction line, and the 220 diffraction line in a face-centered cubic lattice. The position of the 2θ° angle varies depending on the crystal species contained in the metal film, but can be measured in advance by θ-2θ scanning (out-of-plane XRD). For example, if the metal film is made of copper, the 2θ° angle at which the 200 diffraction line appears is 50°, the 2θ° angle at which the 111 diffraction line appears is 43°, and the 2θ° angle at which the 220 diffraction line appears is 74°. Pole measurement is performed in the positional relationship determined above, with the X-ray incident angle (θ) and the X-ray detector angle (2θ) fixed at predetermined values. Pole measurement is a type of X-ray diffraction measurement method in which the orientation of crystal planes tilted in various directions is measured while the tilt angle (sometimes referred to as ψ or α) of the metal film and the in-plane rotation angle (sometimes referred to as φ or β) of the metal film are changed while the θ and 2θ angles are fixed as described above. Performing pole measurement using the above procedure makes it possible to determine the orientation in which the base index planes preferentially grow in the metal film. In the pole measurement, the measurement is performed with the

[100] direction, the

[010] direction, and the

[001] direction as references.

[0022] The specific conditions for performing the pole measurement are as follows: Measurement device: D8 DISCOVER Plus manufactured by Bruker Corporation X-ray source: Cu-Kα ray X-ray source output: 45 kV, 120 mA Range of tilt angle ψ: 10 to 72° Range of rotation angle φ: 0 to 360° Step time: 3 s / step φ range: 120 divisions around the circumference in 3° / step increments Incident pattern optical system: multilayer mirror, 0.3 mmφ microslit, Ni0.02 filter, 0.3 mmφ collimator Receiving side optical system: EIGER multimode detector 2D mode Conditions with XY axis oscillation: X axis range 3 mm, Y axis range 3 mm, X axis amplitude speed 3 mm / s, Y axis amplitude speed 5 mm / s

[0023] When pole measurements are performed using the above measurement method, pole figures for each base index plane are obtained. For example, when pole measurements are performed on a metal film containing face-centered cubic lattice crystals, pole figures for the {200} plane, the {111} plane, and the {220} plane are obtained. Using each pole figure, an analysis is performed to determine the preferential orientation of a specific crystal plane. The analysis is performed using a component fit method based on the

[100] direction, the

[010] direction, and the

[001] direction. The component fit method is a method in which, from each of the measured pole figures, multiple crystal components are assumed in which a specific plane faces a specific direction, and pole figures for each of the assumed crystal components are generated as many times as the number of crystal components. Each generated pole figure is weighted to minimize the error between the generated pole figure and the measured pole figure. This method allows the volume fraction of each crystal component to be analyzed.

[0024] More specifically, the analysis is performed using the component fitting method under the following conditions. As a specific example, the analysis conditions for a copper metal film assuming a face-centered cubic lattice are described below. Software used: Diffrac. TEXTURE manufactured by Bruker. Lattice constant a: 0.3615 nm. Specifically, the fitting method involves assuming crystalline components from the pole figures of the {200} plane, the {111} plane, and the {220} plane, and fitting the respective peak positions and intensities using the least-squares method. The volume fraction of the assumed crystalline components is obtained by fitting using the least-squares method. The number of crystalline components used in the fitting is increased to a maximum of five so as to reduce the chi-square value, and the analysis is continued until the chi-square value becomes 400 or less.

[0025] By performing the above procedure, when pole measurements are performed based on the

[100] direction, which is the measurement direction, the volume fraction of crystals whose orientation direction is the <100> direction can be calculated. By performing pole measurements in the in-plane direction of the metal film using the above procedure, it is possible to determine whether the metal film has a first direction. In other words, by performing measurements using the above procedure while changing the measurement direction in the in-plane direction, it is possible to determine whether the metal film has a first direction. As described above, the first direction is a direction that satisfies Requirement 1.

[0026] It is also preferable that the first direction satisfy the following requirement 2. Requirement 2: When the first direction is the

[100] direction and pole measurement is performed by X-ray diffraction, the volume fraction of crystals whose orientation direction is the <100> direction is 60% or more. The volume fraction of crystals in requirement 2 can be calculated in the same way as requirement 1.

[0027] It is also preferable that the first direction satisfy the following requirement 3. Requirement 3: When the first direction is the

[100] direction and pole measurement is performed by X-ray diffraction, the volume fraction of crystals whose orientation direction is the <100> direction is 65% or more. The volume fraction of crystals in requirement 3 can be calculated in the same way as requirement 1.

[0028] In addition, the upper limit of the volume fraction of crystals whose orientation direction is the <100> direction in Requirement 1, Requirement 2, and Requirement 3 may be 100%, 99% or less, 90% or less, 80% or less, or 70% or less, respectively.

[0029] Those skilled in the art will readily understand that analysis can be performed using similar procedures even when the metal film contains other atoms and crystals of other crystal lattices.

[0030] The metal film of the laminate of the present invention is not particularly limited as long as it contains copper and has a first direction in the in-plane direction that satisfies the above-mentioned requirement 1. The crystal lattice of the metal film is preferably a cubic crystal lattice, more preferably a face-centered cubic crystal lattice. The metal film contains copper (Cu), and the content of copper atoms relative to all atoms in the metal film is preferably 30 atomic % or more, more preferably 50 atomic % or more, even more preferably 80 atomic % or more, and particularly preferably 90 atomic % or more. The content of copper atoms relative to all atoms in the metal film may be 100 atomic %, and is often 99.999 atomic % or less. The metal film may contain elements other than copper. The metal film may contain elements other than copper, such as one or more elements selected from the group consisting of nickel (Ni), cobalt (Co), manganese (Mn), gold (Au), molybdenum (Mo), carbon (C), silicon (Si), germanium (Ge), indium (In), tin (Sn), silver (Ag), and iron (Fe).

[0031] The metal film of the laminate of the present invention may be a deposited film disposed in indirect or direct contact with another substrate, or may be a free-standing film that can be handled independently without contacting another substrate, etc. When the metal film of the laminate of the present invention is a deposited film, the laminate of the present invention preferably has a substrate. The substrate is not particularly limited, but is preferably amorphous. An amorphous substrate means that, when out-of-plane XRD measurement of the substrate alone is performed, no clear diffraction peak derived from the substrate is observed, or even if a diffraction peak is observed, the FWHM (Full Width at Half Maximum) of the diffraction peak with the highest intensity is 1.0° or more in 2θ.

[0032] The substrate is also preferably a quartz substrate. The substrate is also preferably an amorphous quartz substrate. The term "quartz substrate" means that the material constituting the substrate is quartz. Examples of quartz include synthetic quartz and fused quartz, with synthetic quartz being preferred.

[0033] The thermal expansion coefficient of the substrate is 2.0 × 10 －６ (K －１ ) or less, and 1.5 × 10 －６ (K －１ ) or less is more preferable, and 1.0 × 10 －６ (K －１ The lower limit of the thermal expansion coefficient of the substrate is, for example, −10.0×10 －６ (K －１ In this specification, the thermal expansion coefficient means the thermal expansion coefficient at 300K.

[0034] The substrate may be a commercially available product, and examples of commercially available substrates include "AQ" and "QJ" manufactured by AGC Electronics Inc.

[0035] The thickness of the substrate is preferably 0.2 mm or more, more preferably 0.5 mm or more, and even more preferably 1 mm or more. The upper limit of the thickness of the substrate is, for example, 10 mm.

[0036] In addition, when the metal film of the laminate of the present invention is a deposited film, an oxide film may be provided between the metal film and the substrate. Examples of the oxide film include oxides of metals such as alkaline earth metals, transition metals, and rare earth metals. Among them, MgO (magnesium oxide), Al ２ O ３ (sapphire), LaAlO ３ , or TiO ２ is preferable, and MgO or Al ２ O ３ is more preferred.

[0037] When the metal film of the laminate of the present invention is a free-standing film, the metal film is preferably copper foil. The term "copper foil" means that the thickness of the metal film is 1 to 200 μm, preferably 10 μm or more, and more preferably 15 μm or more. When the metal film is copper foil, the thickness of the metal film is preferably 150 μm or less, more preferably 100 μm or less. Furthermore, the term "copper foil" means that the copper atom content relative to all atoms in the metal film is 50 atomic % or more. When the metal film is copper foil, the copper atom content relative to all atoms in the metal film is preferably 80 atomic % or more, more preferably 90 atomic % or more. When the metal film is copper foil, the copper atom content relative to all atoms in the metal film may be 100 atomic %, but is often 99.999 atomic % or less.

[0038] Furthermore, when the metal film is a copper foil, the angle between the first direction and the rolling direction of the copper foil is preferably 0 to 10° or 80 to 90°, and more preferably 0 to 5° or 85 to 90°. Furthermore, the angle is preferably 0 to 10°, and more preferably 0 to 5°. The rolling direction of the copper foil can be confirmed by observing the rolling marks on the copper foil.

[0039] The surface of the metal film is preferably flat. The surface roughness Ra of the metal film surface is preferably 10 nm or less, more preferably 5 nm or less, and even more preferably 2 nm or less. The surface roughness Ra is often 0.1 nm or more. Ra can be measured using an atomic force microscope (AFM), for example, by scanning an area of ​​1.5 μm square and calculating from the height mapping obtained. The surface roughness Ra is a value measured by a method conforming to JIS B0601:2001 (ISO4287:1997).

[0040] The shape of the metal film when viewed from the normal direction of the surface of the metal film is not particularly limited and can be adjusted appropriately depending on the application. For example, the shape of the metal film may be circular, square, or rectangular. The metal film may also have a pattern of a desired shape. The size of the metal film is adjusted appropriately depending on the application. For example, the area of ​​the metal film may be 1 to 1,000,000 mm ２ and 100 to 10,000 mm ２ is preferred.

[0041] [Graphene Film] The graphene film in the laminate of the present invention has a high single-layer ratio. The single-layer ratio of the graphene film in the laminate of the present invention is preferably 90.0% or more, more preferably 95.0% or more. The upper limit of the single-layer ratio is not particularly limited and may be 100.0%. The single-layer ratio of graphene in the laminate of the present invention is measured by the following method. First, a laminate to be measured is prepared. For the prepared laminate, a region where a metal film is present (hereinafter also referred to as a "metal film region") is equally divided into nine parts. For example, if the metal film region is square, the metal film region is divided into three parts along one side and then into three parts along a direction perpendicular to the side. As a specific example, the square-shaped metal film region shown in FIG. 2 (the hatched area in FIG. 2) is divided into three parts in the left-right direction and the top-bottom direction of the page, thereby dividing the region into regions A1 to A9. Raman spectroscopy is performed on regions A1 to A9 other than the regions including the vertices of the square-shaped metal film region. That is, among the regions A1 to A9 shown in FIG. 2, Raman spectroscopy is performed in the regions A2, A4, A5, A6, and A8.

[0042] In this specification, Raman spectroscopy is performed using a microscopic laser Raman device (Horiba, Ltd., LabRAM HR800). The measurement conditions are as follows: excitation light wavelength: 532 nm, excitation light irradiation diameter: 2.5 μm, excitation light output: 400 mW, slit width: 100 μm, and grating: 600 g / mm.

[0043] The Raman spectroscopy measurement is performed at any nine points within a predetermined range in each of the regions (regions A2, A4, A5, A6, and A8). A Raman spectrum is obtained by performing the Raman spectroscopy measurement. For example, when evaluating a 25 mm square synthetic substrate, the predetermined range may be a 2.4 mm square range from the center of the 8.33 mm square region A2. The nine-point measurement range can be 28.8% of the maximum length of each region. Even when the metal film region is circular, each region can be set in the same manner as above, and the measurement points can be determined. When a Raman spectrum of a graphene film is obtained, peaks corresponding to the G band, which originates from the in-plane motion of carbon atoms in the graphene film, and the 2D band (also called the G' band), which originates from second-order phonon scattering, are observed. The G band is observed at 1590 cm －１ The 2D band is observed around 2700 cm －１ The D band, which is caused by the disorder and defects in the graphene film, is observed around 1350 cm －１ At the nine measurement points in each of the above regions, the G-band peak intensity I Ｇ , the peak intensity of the 2D band I ２Ｄ Intensity ratio (I ２Ｄ / I Ｇ That is, Raman spectroscopy was performed at a total of 45 points, and the above I ２Ｄ / I Ｇ Calculate the above I ２Ｄ / I Ｇ is 1 or more, the graphene film is determined to be a single layer at that measurement point.

[0044] On the other hand, when a G-band peak is observed in the Raman spectrum obtained by the above-mentioned Raman spectroscopy measurement, it suggests the presence of a compound containing sheet-like carbon atoms at that measurement point. It is also understood that graphene films are not formed on substrates or oxide films, but only on metal films. Therefore, when a G-band peak is observed in the Raman spectrum, it can be said that a metal film and a compound containing sheet-like carbon atoms are present at that measurement point.

[0045] The monolayer ratio of the graphene film is determined by observing the peak of the G band and ２Ｄ / I Ｇ is 1 or more, by the number of measurement points where a G band peak is observed among the above measurement points (45 points), and multiplying the result by 100. The preferable range of the graphene monolayer ratio is as described above.

[0046] In the laminate of the present invention, when determining the monolayer ratio of the graphene film, the intensity ratio I ２Ｄ / I Ｇ The average value (arithmetic mean value) of the intensity ratio I is preferably 1.50 or more, more preferably 1.75 or more, and even more preferably 1.80 or more. ２Ｄ / I Ｇ The arithmetic mean value of is often 7.00 or less, and may be 5.00 or less.

[0047] In addition, in the laminate of the present invention, when determining the graphene monolayer ratio, the intensity ratio I ２Ｄ / I Ｇ The standard deviation is preferably 0.50 or less, more preferably 0.35 or less, and even more preferably 0.32 or less. The standard deviation is not particularly limited, and is often 0.01 or more, and may be 0.10 or more.

[0048] The size of the graphene film in the in-plane direction is adjusted appropriately depending on the application of the laminate or the graphene film, but is, for example, 1 to 1,000,000 mm ２ is.

[0049] The thermal expansion coefficient of graphene is (-8.0±0.7) × 10 －６(K －１ ), and it is preferable that the thermal expansion coefficient of the graphene film is also in the above range. In the laminate, the difference between the thermal expansion coefficient of the substrate and the thermal expansion coefficient of the graphene film is 2×10 －６ (K －１ ) or less is preferable, and 1 × 10 －６ (K －１ ) The following is more preferred.

[0050] The carrier mobility of the graphene film is 1000 (cm ２ / V·s) or more, and 3000 (cm ２ A graphene film having a carrier mobility in the above range is excellent in various properties such as device characteristics as a sensor and a transistor, and SPP (surface plasmon polariton) radio wave characteristics. The upper limit of the carrier mobility of the graphene film is not particularly limited, but is preferably 200,000 (cm ２ / V·s) or less, and 20000 (cm ２ / V·s) or less.

[0051] [Other Layers] The laminate of the present invention may optionally have layers other than the metal film and the graphene film. Examples of the other layers that the laminate may have include, in addition to the substrate and oxide film described above, an electrode, an insulating layer, a protective layer, and the like.

[0052] In the embodiment shown in FIG. 1 , the laminate 10 has the graphene film 14 on only one surface of the metal film 12. However, the laminate of the present invention may have graphene films on both surfaces of the metal film.

[0053] <Applications of Laminate> The graphene film of the laminate of the present invention has a high single-layer ratio and the properties of the graphene film are fully exhibited, and therefore the laminate is preferably applied to devices such as biosensors, optical sensors, electromagnetic wave sensors, transistors, metasurfaces, and transparent electrodes.

[0054] <Method for Producing Laminate (First Embodiment)> In a first embodiment of the method for producing a laminate of the present invention, a graphene film is formed on a metal film containing copper by thermal chemical vapor deposition. In the first embodiment of the method for producing a laminate of the present invention, the metal film has a first direction that satisfies the following requirement 1. Requirement 1: When the first direction is the

[100] direction and pole point measurement is performed by X-ray diffraction, the volume fraction of crystals whose orientation direction is the <100> direction is 55% or more. According to the first embodiment of the method for producing a laminate of the present invention, it is thought that a graphene film with a high single-layer ratio can be easily formed on the surface of the metal film for the same reasons as in the case of the laminate of the present invention.

[0055] Requirement 1 in the first embodiment of the method for producing a laminate of the present invention is the same as Requirement 1 satisfied by the metal film of the laminate of the present invention described above, and the first direction is the same as the first direction in the metal film of the laminate of the present invention described above. Furthermore, examples and preferred aspects of the metal film in the first embodiment of the method for producing a laminate of the present invention are the same as the examples and preferred aspects of the metal film of the laminate of the present invention described above.

[0056] An example of a method for preparing a metal film having the first direction is a method of heating a copper-containing metal film while applying tensile stress to the metal film. The temperature at which the metal film is heated is preferably 700°C or higher, more preferably 800°C or higher, even more preferably 900°C or higher, and particularly preferably 1000°C or higher. The atmosphere at which the metal film is heated may be an inert atmosphere or a reducing atmosphere. Examples of inert atmospheres include an inert gas atmosphere such as nitrogen gas and argon gas. Examples of reducing atmospheres include an atmosphere containing the inert gas and hydrogen gas. For details of the method for heating a copper-containing metal film while applying tensile stress to the metal film, a method similar to the method described later in the second embodiment of the laminate of the present invention can be appropriately adopted. For example, the tensile stress is preferably gravity acting on the metal film.

[0057] It is also preferable to perform an oxidation treatment before heating the metal film. Examples of the oxidation treatment include a method of heating the metal film in an oxidizing atmosphere at a temperature lower than the heating temperature. The heating temperature in the oxidation treatment is preferably 100°C or higher, more preferably 150°C or higher, and even more preferably 200°C or higher. The heating temperature in the oxidation treatment is often 500°C or lower, and preferably 300°C or lower. The oxidizing atmosphere is preferably an atmosphere containing oxygen, and may be an air atmosphere. Heating the metal film while applying tensile stress after the oxidation treatment makes it easier to obtain a metal film having the first direction.

[0058] When preparing the metal film having the first direction, it is preferable to use copper foil as the metal film. As the copper foil, copper foil having a {110} plane preferentially oriented in the thickness direction is preferable. Furthermore, the copper foil is preferably made of oxygen-free copper. Furthermore, it is preferable that the surface roughness of the copper foil is small (for example, a surface roughness Ra of 10 nm or less, more preferably 5 nm or less, and even more preferably 2 nm or less).

[0059] The oxidation treatment and the heating of the metal film may be performed inside an apparatus that performs thermal chemical vapor deposition (thermal CVD). Alternatively, the oxidation treatment may be performed outside an apparatus that performs thermal CVD, and the heating of the metal film may be performed inside the apparatus that performs thermal CVD. Alternatively, the oxidation treatment may be performed outside an apparatus that performs thermal CVD, and the heating of the metal film may be performed outside the apparatus that performs thermal CVD.

[0060] A method for forming a graphene film by thermal CVD includes a method in which gaseous carbon-containing molecules are brought into contact with the surface of a heated metal film under a pressure lower than atmospheric pressure, thereby growing graphene.

[0061] Examples of carbon-containing molecules used to form graphene films include hydrocarbons and heteroatom-containing molecules. Hydrocarbons with 10 or fewer carbon atoms are preferred, with those with 5 or fewer carbon atoms being more preferred. Specific 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. Examples of heteroatom-containing molecules include heteroatom-containing hydrocarbons with 10 or fewer carbon atoms, with those with 5 or fewer carbon atoms and containing a heteroatom selected from oxygen, nitrogen, and boron being more preferred. Specific examples of heteroatom-containing molecules include alcohols such as methanol and ethanol, and carbon monoxide. In CVD, the carbon-containing molecules are preferably supplied at a constant pressure into a chamber containing a metal film. Examples of methods for supplying the carbon-containing molecules include supplying gaseous carbon-containing molecules into a chamber together with inert gases such as helium and argon, and hydrogen gas. The pressure of the carbon-containing molecules in the chamber is, for example, subatmospheric pressure, －５ ~10 ５ Pa is preferred, 10 －３ ~10 ５ Pa is more preferred.

[0062] The heat treatment temperature in thermal CVD is preferably 300 to 1200°C, more preferably 500 to 1100°C, in terms of a fast graphene film formation rate and a graphene film with few defects. The heat treatment temperature in thermal CVD is also preferably 1050°C or higher. The heat treatment time is preferably 1 to 300 minutes, more preferably 10 to 120 minutes. Examples of heating means for the heat treatment include induction heating, radiant heat, laser, infrared rays, microwaves, plasma, and ultraviolet rays.

[0063] It is also preferable to perform preheating before graphene formation by thermal CVD. It is also preferable that the heating temperature of the preheating be 1000°C or higher. Preheating also preferably involves hydrogen annealing the metal film. Hydrogen annealing reduces the surface of the metal film, which tends to improve the crystallinity of the surface of the metal film at the high temperature used for CVD. It is also effective to perform hydrogen annealing at a low temperature followed by hydrogen annealing at the temperature used for CVD. The metal film is hydrogen annealed by placing the metal film in a chamber used for CVD and heating the metal film. The hydrogen annealing temperature is, for example, 300 to 1100°C. The preheating time is preferably 30 minutes or more, more preferably 1 hour or more, in order to improve the crystallinity of the metal film and the quality of the graphene film. Furthermore, the preheating time is preferably 10 hours or less, more preferably 8 hours or less, and even more preferably 6 hours or less. During the hydrogen annealing, hydrogen is preferably supplied into the chamber together with an inert gas. The hydrogen supply rate is, for example, 10 to 600 sccm. It should be noted that "sccm" represents the flow rate under standard conditions, that is, mL / min at 0° C. and atmospheric pressure.

[0064] The details of the physical properties of the graphene formed are the same as those of the graphene film of the laminate of the present invention.

[0065] <Laminate Manufacturing Method (Second Embodiment)> In a second embodiment of the laminate manufacturing method of the present invention, a copper-containing metal film is heated while a tensile stress is applied to the metal film, and a graphene film is formed on the heated metal film by thermal chemical vapor deposition. In this second embodiment of the laminate manufacturing method of the present invention, an angle between a surface of the metal film and the direction in which the tensile stress acts is 0 to 10 degrees.

[0066] According to the second embodiment of the method for producing a laminate of the present invention, a graphene film with a high single-layer ratio is easily formed on the surface of a metal film. The reason for this is not entirely clear, but the inventors speculate as follows: It is thought that when a copper-containing metal film is heated while a tensile stress is applied to the metal film, crystal grain domains are likely to face a predetermined direction on the surface of the metal film, leading to crystal growth. When the crystal grain domains face a predetermined direction, the number of origins of defects in the graphene film is likely to be reduced, and the resulting graphene film is thought to have a high single-layer ratio.

[0067] The angle between the surface of the metal film and the direction in which the tensile stress is applied is preferably 0 to 5°, and more preferably 0 to 3°. The method for heating the metal film while applying the tensile stress is not particularly limited, but examples include a method in which both ends of the metal film are held by gripping parts and a tensile stress is applied to the metal film in a predetermined direction via the gripping parts, and a method using gravity, which will be described later.

[0068] The tensile stress is also preferably derived from gravity acting on the metal film. That is, it is also preferable to heat the metal film while the surface of the metal film is at an angle of 0 to 10° with the direction of gravity, and then form a graphene film on the heated metal film by thermal chemical vapor deposition (thermal CVD). An example of a method for applying gravity-induced tensile stress to the metal film is a method of suspending the metal film. More specifically, one side of a rectangular metal film is gripped, and the side opposite the side is left as a free end, and the metal film is suspended by the gripping part. Another example of such a method is to form a hole on one side of the rectangular metal film and hang the metal film by passing a rod through the hole. Another example of such a method is to bend one side of the rectangular metal film and hang the metal film by hanging it on a rod. Alternatively, the metal film may be bent at the center of the rectangular metal film and hung on a rod.

[0069] The angle between the surface of the metal film and the direction of gravity is preferably 0 to 5°, and more preferably 0 to 3°. The metal film is also preferably a copper foil. The definition of the metal film being a copper foil is the same as that of the copper foil in the laminate of the present invention, and the preferred embodiments of the copper foil are also the same as those of the metal film in the laminate of the present invention. It is also preferable that the metal film is a copper foil, and that the metal film is heated in a state where the angle between the rolling direction of the copper foil and the direction of gravity is 0 to 10° or 80 to 90°. The angle between the rolling direction of the copper foil and the direction of gravity is more preferably 0 to 5° or 85 to 90°. The angle is preferably 0 to 10°, and more preferably 0 to 5°.

[0070] The heating of the metal film while applying the tensile stress may be performed by preheating for thermal CVD. That is, preheating may be performed before forming graphene by thermal CVD, and the metal film may be heated while applying the tensile stress by the preheating. Regarding the preheating, the aspects described in the first embodiment of the laminate manufacturing method of the present invention can be adopted, and preferred aspects are also the same. For example, the preheating time is preferably 1 hour or more. It is also preferable that the preheating temperature is 1000°C or higher. The metal film may be heated by a device other than a thermal CVD device.

[0071] As the metal film, it is preferable to use the same metal film (preferably copper foil) as in the first embodiment of the method for producing a laminate of the present invention.

[0072] It is also preferable to perform an oxidation treatment on the metal film before heating the metal film. The oxidation treatment can be the same as the oxidation treatment described in the first embodiment of the method for producing a laminate of the present invention. The preferred aspects of the oxidation treatment are also the same as those in the first embodiment. Performing the oxidation treatment in advance tends to increase the monolayer ratio of the resulting graphene film.

[0073] In a second embodiment of the method for producing a laminate of the present invention, a graphene film is formed on the heated metal film by thermal chemical vapor deposition (thermal CVD). The method for forming the graphene film by thermal CVD is the same as the method in the first embodiment of the method for producing a laminate of the present invention, and preferred embodiments are also the same.

[0074] Specifically, the second embodiment of the method for producing a laminate of the present invention can be carried out, for example, by the following procedure: An example of the second embodiment of the method for producing a laminate of the present invention is a method in which a metal film is subjected to the above-mentioned oxidation treatment, the oxidized metal film is suspended by the above-mentioned method, the metal film is placed in a thermal CVD apparatus so that the angle with the direction of gravity is 0 to 10°, and the preheating and thermal CVD are carried out in the thermal CVD apparatus.

[0075] The present invention will be described in more detail below based on examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. 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. Note that Examples 1 and 2 described below are examples, and Examples 3 and 4 are comparative examples.

[0076] Example 1: A rolled copper foil (product number HA-V2, size 25 mm × 50 mm, thickness 35 μm) manufactured by JX Nippon Mining & Metals Corporation was prepared as a metal film. Hereinafter, this rolled copper foil will be referred to as "copper foil A." First, copper foil A was subjected to a heat treatment (oxidation treatment) at 250°C in an air atmosphere for 45 minutes. Thereafter, one end of copper foil A was bent and held with a holding rod, and copper foil A was suspended and held. In other words, copper foil A was held so that the angle between the surface of copper foil A and the direction of gravity was 0°. Furthermore, the angle between the rolling direction of copper foil A and the direction of gravity was 0°.

[0077] Next, the copper foil A held in the above state was placed in the center of a quartz tube attached to a tubular furnace (thermal CVD apparatus), and after preheating, a graphene film was formed on the surface of the copper foil A by thermal CVD. Specifically, the temperature was raised to 1050°C in an Ar atmosphere, and then preheated by hydrogen annealing in a hydrogen-containing atmosphere while maintaining the temperature at 1050°C. The preheating time was 300 minutes. The flow rates of argon gas and hydrogen gas during hydrogen annealing were 500 sccm and 20 sccm, respectively. Next, while maintaining the temperature at 1050°C, methane and hydrogen were flowed into the quartz tube as carbon raw materials to form a graphene film by thermal CVD. Next, the atmosphere inside the quartz tube was replaced with argon gas, and the copper foil A on which the graphene film was formed was slowly cooled. The total gas flow rate during thermal CVD was 4500 sccm, and the flow rates of methane gas and hydrogen gas were 0.91 volume% and 2.0 × 10, respectively, of the total flow rate. －３ % by volume.

[0078] The copper foil A on which the graphene film was formed was removed from the tubular furnace to obtain a laminate of Example 1. The obtained laminate was subjected to pole measurement by X-ray diffraction using the method described above to confirm whether it had a first direction satisfying Requirement 1. Furthermore, Raman spectroscopy was performed using the method described above to obtain values ​​such as the monolayer ratio described above. The results are shown in the table below.

[0079] Example 2 A laminate of Example 2 was obtained in the same manner as in Example 1, except that the preheating time was changed to 40 minutes and the content of methane gas during thermal CVD was adjusted to the value shown in the table below. Furthermore, as with the laminate of Example 1, pole point measurement by X-ray diffraction and Raman spectroscopy were performed on the laminate of Example 2.

[0080] Example 3 The laminate of Example 3 was obtained in the same manner as in Example 1, except that the copper foil A was placed on a quartz substrate and introduced into a tubular furnace. That is, preheating and thermal CVD were performed in a state where the angle between the surface of the copper foil A and the direction of gravity was 90°. Furthermore, as with the laminate of Example 1, pole point measurement by X-ray diffraction and Raman spectroscopy were performed on the laminate of Example 3.

[0081] Example 4 A laminate of Example 4 was obtained in the same manner as in Example 1, except that the copper foil A was changed to copper foil B (manufactured by Nilaco Corporation, purity 3N, size 25 mm × 50 mm, thickness 80 μm) and the preheating time was changed to 720 minutes. Furthermore, as with the laminate of Example 1, pole point measurement by X-ray diffraction and Raman spectroscopy were performed on the laminate of Example 4.

[0082] <Results> Table 1 shows the processing conditions for each laminate in Examples 1 to 4 above, and the measurement results for each laminate. In Table 1, the notation "hanging" in the "Installation method" column indicates that the copper foil was held by hanging. On the other hand, the notation "flat" indicates that it was placed on a quartz substrate. In Table 1, the column "Volume fraction of crystals oriented in the <100> direction" indicates the volume fraction value in the direction in which the volume fraction of crystals oriented in the <100> direction is maximum when the measurement direction is set to the

[100] direction and the measurement direction is changed in the in-plane direction. In Table 1, the column "Angle between the rolling direction and the maximum measurement direction" indicates the angle between the rolling direction and the measurement direction showing the volume fraction listed in the above column "Volume fraction of crystals oriented in the <100> direction."

[0083]

[0084] The results shown in Table 1 confirm that when a metal film has a first direction in the in-plane direction that satisfies the above-described Requirement 1, the graphene film has an excellent monolayer ratio. Requirement 1 is as follows: Requirement 1: When the first direction is the

[100] direction and pole point measurement is performed using X-ray diffraction, the volume fraction of crystals whose orientation direction is the <100> direction is 55% or more. Furthermore, a comparison between Example 1 and Example 2 confirms that the monolayer ratio of the graphene film is higher when the volume fraction of crystals whose orientation is the <100> direction is 65% or more. The entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2024-146415, filed on August 28, 2024, are incorporated herein by reference.

[0085] 10 laminate 12 metal film 14 graphene film

Claims

1. A laminate having a copper-containing metal film and a graphene film adjacent to the metal film, wherein the metal film has a first in-plane direction that satisfies the following requirement 1. Requirement 1: When the first direction is the [100] direction and pole point measurement is performed by X-ray diffraction, the volume fraction of crystals whose orientation direction is the <100> direction is 55% or more.

2. The laminate according to claim 1, which satisfies the following requirement 2: Requirement 2: When the first direction is the [100] direction and pole measurement is performed by X-ray diffraction, the volume fraction of crystals whose orientation direction is the <100> direction is 60% or more.

3. The laminate according to claim 1, wherein the metal film is copper foil, and the angle between the first direction and the rolling direction of the copper foil is 0 to 10 degrees or 80 to 90 degrees.

4. The laminate according to claim 1, wherein the metal film is copper foil, and the angle between the first direction and the rolling direction of the copper foil is 0 to 10 degrees.

5. The laminate according to any one of claims 1 to 4, wherein the graphene film has a single-layer ratio of 95% or more.

6. G band peak intensity I obtained by Raman spectroscopy of the graphene film Ｇ The peak intensity of the 2D band I ２Ｄ Intensity ratio I ２Ｄ / I Ｇ The average value of the intensity ratio I is 1.75 or more, ２Ｄ / I Ｇ The laminate according to any one of claims 1 to 4, wherein the standard deviation of 7. A method for manufacturing a laminate, in which a graphene film is formed on a metal film containing copper by thermal chemical vapor deposition, wherein the metal film has a first in-plane direction that satisfies the following requirement 1: Requirement 1: When the first direction is the [100] direction and pole point measurement is performed by X-ray diffraction, the volume fraction of crystals whose orientation direction is the <100> direction is 55% or more.

8. A method for manufacturing a laminate, comprising heating a copper-containing metal film while applying a tensile stress to the metal film, and forming a graphene film on the heated metal film by thermal chemical vapor deposition, wherein an angle between a surface of the metal film and the direction in which the tensile stress acts is 0 to 10 degrees.

9. The method for producing a laminate according to claim 8, wherein the tensile stress is derived from gravity acting on the metal film.

10. The method for producing a laminate according to claim 9, wherein the metal film is a copper foil, and the metal film is heated in a state where the angle between the rolling direction of the copper foil and the direction of gravity is 0 to 10° or 80 to 90°.

11. The method for producing a laminate according to any one of claims 8 to 10, wherein the metal film is subjected to an oxidation treatment before being heated.

12. The method for producing a laminate according to any one of claims 8 to 10, wherein preheating is performed before the formation of graphene by thermal chemical vapor deposition, and the metal film is heated while a tensile stress is applied by the preheating.

13. The method for producing a laminate according to claim 12, wherein the preheating time is 1 hour or more.

14. The method for producing a laminate according to claim 12, wherein the preheating temperature is 1000°C or higher.

15. The method for producing a laminate according to any one of claims 7 to 10, wherein the graphene film is formed by thermal chemical vapor deposition at 1050°C or higher.

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