JP7613728B2 - Carbon compounds and their manufacturing methods - Google Patents

Description

The present invention relates to a carbon compound and a method for producing the same.

Currently, fullerenes and carbon nanotubes are attracting attention as carbon materials of the future. The atoms that make up these materials are carbon (C), the same as those in graphite and diamond, but they have a spherical or tubular structure in which the atoms are bonded in closed bonds. Carbon nanotubes, which have a nano-sized tubular bond structure, are particularly expected to be used in semiconductor device materials, battery materials, conductive materials, hydrogen storage materials, capacitor materials, superhard materials, pharmaceuticals, resist materials, and more.

A typical fullerene structure is one in which 60 atoms are bonded together in the shape of a soccer ball, and in addition to the uses mentioned above, it is expected to be used in superconducting and ultrahard materials.

Introduction to Carbon (https://www.toyotanso.co.jp/introduction/future.html)

However, the only crystal structures currently known for carbon compounds are those with graphite and diamond structures, in addition to the special structures such as fullerenes and carbon nanotubes mentioned above, and there are naturally limitations to how well their properties can be improved.

The present invention aims to provide a carbon compound with a new crystal structure that can provide new properties not found in conventional crystal structures.

In order to achieve the above object, the present invention is as follows.
(1) A laminate comprising a crystalline silicon substrate and a carbon multilayer film, the C-axis direction of silicon constituting the crystalline silicon substrate and the carbon multilayer film are aligned parallel to each other, the carbon multilayer film is formed on the crystalline substrate and contains a phase of a spinel type crystal structure , and the crystalline silicon substrate and the carbon multilayer film are crosslinked .
(2) The stack according to (1), in which a C-axis direction of the silicon and a stacking direction of the carbon multilayer film are arranged parallel to each other.
( 3 ) The laminate according to (1) or (2) , characterized in that it contains, continuous to the phase of the spinel type crystal structure, a phase having a structure in which graphite is laminated in multiple stages on the side opposite to the substrate.
( 4 ) The laminate according to any one of (1) to (3) , characterized in that the resistivity at a thickness of 100 nm or less is 10 ⁻⁵ to 10 ⁻¹⁰ Ω·m.
( 5 ) The laminate according to any one of (1) to ( 4 ), wherein the resistivity decreases with increasing thickness of the carbon compound.
( 6 ) A method for manufacturing a laminate, comprising the steps of: disposing a cathode having an electron source disposed thereon and an anode having a crystalline silicon substrate disposed opposite the cathode; disposing a gate electrode on the cathode side and an acceleration electrode on the anode side between the cathode and the anode; flowing an acetylene-based hydrocarbon between the gate electrode and the acceleration electrode, decomposing the acetylene-based gas with electrons emitted from the electron source and a voltage applied to the gate electrode, thereby obtaining at least one of ionized carbon and hydrocarbon; and accelerating the at least one of the carbon and hydrocarbon by the voltage applied to the acceleration electrode, and irradiating the crystalline silicon substrate of the anode with the carbon and hydrocarbon .

As described above, the present invention can provide a carbon compound with a new crystal structure that can provide new properties not found in conventional crystal structures.

FIG. 1 is a diagram showing a schematic configuration of an apparatus for producing a carbon compound according to an embodiment. 1 is a SEM photograph of a carbon compound in an example. 1 is an electron beam transmission image of a carbon compound in an example. 1 is an electron beam transmission image of a carbon compound in an example. FIG. 2 is a diagram of an apparatus for measuring electrical properties of a carbon compound in the examples.

Hereinafter, details and other features of the present invention will be described based on embodiments.
(Carbon compounds)
The carbon compound of the present invention is formed on a crystalline substrate and contains a phase of a spinel-type crystal structure bridging the substrate. Since no carbon compound with such a structure has existed in the past, it is expected to exhibit various properties.

For example, due to its spinel crystal structure, it is expected to exhibit magnetism that has not existed in conventional carbon.

Also, changes can be seen in the electrical properties, for example, the resistivity at a thickness of 100 nm or less is about 10 ^-5 to 10 ^-10 Ω·m, which is similar to that of metallic aluminum, and it is found to have metallic properties. The minimum thickness at which this resistivity is exhibited is, for example, 20 nm.

Furthermore, the carbon compound of the present invention exhibits a decrease in resistivity with increasing thickness, and thus exhibits properties similar to those of a thin metal film, and thus has metallic properties. For example, the resistivity decreases from 10 ^-5 to 10 ^-10 Ω·m as the thickness increases from 0.02 μm to 1.2 μm.

Currently, it is believed that the above-mentioned properties, especially the metallic properties, depend not only on the spinel-type crystal structure in the carbon compound, but also on the property of the carbon compound that it contains a polycarbon phase in which graphite is laminated in multiple layers on the side opposite the substrate, continuous with the spinel-type crystal structure phase.

In this invention, "crosslinking" does not mean a reaction that mainly occurs in polymer chemistry, in which polymers are linked together and their physical and chemical properties are changed, but rather means a bonding state in a broad sense in which the crystal structures of the polymers are bonded together as if they were bridged, as is clear from the results of the following examples.

(Method for producing carbon compounds)
Next, an example of the method for producing the carbon compound will be described. Fig. 1 is a schematic diagram showing an example of an apparatus 10 for producing a carbon compound.

As shown in FIG. 1, the carbon compound manufacturing apparatus 10 of this embodiment has a cathode 11 and an anode 12 arranged to face the cathode 11. An electron source 14 is arranged on the cathode 11, with an ITO transparent conductive film 13 as an electrode. In addition, a crystalline substrate 15 for forming the desired carbon compound is arranged on the anode 12.

Furthermore, between the cathode 11 and the anode 12, a gate electrode 16 is disposed on the cathode 11 side, and an acceleration electrode 17 is disposed on the anode 12 side.

The cathode 11, anode 12, gate electrode 16, and acceleration electrode 17 can be made of metals with excellent electrical conductivity, such as aluminum, gold, silver, and copper, or iron, cobalt, nickel, tungsten, molybdenum, and alloys of these metals with excellent heat resistance.

The electron source 14 is also not particularly limited, but is preferably made of carbon nanotubes from the viewpoint of stable electron emission, and is particularly preferably made of highly crystalline single-walled carbon nanotubes.

The substrate 15 is not particularly limited as long as it has crystallinity, and semiconductors such as silicon and ceramics such as zinc oxide can be used.

As described below, since acetylene-based gas is used to produce carbon compounds, it is preferable to place the entire production apparatus 10 in a container such as a vacuum chamber as necessary.

The size of the manufacturing device 10 can be set appropriately, for example, the distance between the cathode 11 and the anode 12 can be 0.1 to 1.0 cm, the distance between the cathode 11 and the gate electrode 14 can be 0.005 to 0.02 cm, and the distance between the anode 12 and the acceleration electrode 17 can be 0.1 to 0.5 cm.

After preparing the manufacturing apparatus 10 as described above, acetylene-based gas 18 is flowed between the cathode 11 and the anode 12, more specifically between the gate electrode 14 and the acceleration electrode 17. Acetylene-based gas 18 refers to so-called acetylene-based hydrocarbons, meaning substances that have triple bonds between carbon atoms. Specific examples include acetylene, propyne, and 1-butyne, but acetylene is generally used because it is the most reactive, inexpensive, and easily available.

When an acetylene-based gas 18 is flowed at a predetermined flow rate, electrons are emitted from the carbon nanotubes 14 at a current density (dose) of, for example, 70 nA/ ^cm2 or more, and a voltage of, for example, 18 to 40 V is applied to the gate electrode 16, the acetylene-based gas 18 is decomposed and becomes ionized carbon or hydrocarbons.

Next, the ions are accelerated by applying a voltage of, for example, 200 to 600 V to the acceleration electrode 17, and are then irradiated onto the substrate 15. This causes the formation of a carbon compound on the substrate 15 that includes at least the phase having the spinel-type crystal structure described above.

In this way, according to this embodiment, a cathode with an electron source and an anode with a substrate are opposed to each other, a gate electrode and an acceleration electrode are disposed between them, an acetylene-based gas is decomposed by the gate electrode, and the ions obtained by the decomposition by the acceleration electrode are accelerated and irradiated toward the substrate. This is a simple operation that uses the principle of field electron emission, and it is possible to obtain a carbon compound having the desired phase of a spinel-type crystal structure.

Example 1
A carbon compound having a spinel-type crystal structure phase was produced using a production apparatus 10 as shown in FIG.

The cathode 11 and anode 12 were made of a metal or semiconductor substrate, and the gate electrode 16 and acceleration electrode 17 were made of a stainless steel processed plate. Next, the distance between the cathode 11 and the anode 12 was set to 0.35 cm, the distance between the cathode 11 and the gate electrode 16 was set to 0.01 cm, and the distance between the anode 12 and the acceleration electrode 17 was set to 0.17 cm.

Further, a highly crystalline single-walled carbon nanotube having an electron emission size of 15×15 mm ² was used as the electron source 14, and the voltage applied to the gate electrode 16 was set to 22 V. Furthermore, the voltage applied to the acceleration electrode 17 was set to 500 V.

In this embodiment, the entire manufacturing apparatus 10 was housed in a vacuum chamber, and acetylene gas was introduced so that the internal pressure was 1.6 Pa. Zinc oxide formed by wet synthesis was used as the substrate 15.

Figure 2 is an SEM photograph of the obtained carbon compound. The SEM photograph shown in Figure 2 was taken of a test piece in which the obtained carbon compound was embedded in resin and then processed by focused ion beam processing to produce a flake.

As is clear from Figure 2(a), although fine gaps can be seen inside the carbon compound, it is understood that it has an elliptical shape on a macroscopic level. Also, Figure 2(b) is an enlarged view of the white circle part in Figure 2(a), and it can be seen that the zinc oxide particles, which were originally granular, are selectively cross-linked in the crystal C-axis direction by the non-equilibrium excitation reaction field, resulting in elliptical particles. It can also be seen that a carbon film is coated between these elliptical zinc oxide particles.

Figure 3 shows a transmission image of the crystal structure near the interface between zinc oxide and the carbon film, observed using a high-resolution electron beam equivalent microscope (HRTEM: manufactured by JEOL Ltd.) with an acceleration voltage of 300 kV.

Figure 3 (a) shows a high-resolution electron transmission image of the interface between zinc oxide and a carbon film, which shows that a carbon film of about 20 nm is formed on the zinc oxide surface, and that a clear interface between the zinc oxide and the carbon film can be confirmed.

Figures 3(b) and 3(c) show the diffraction pattern and Fourier transform image of the zinc oxide side. From the images in Figures 3(a) to (c), it is clear that the C-axis direction of the zinc oxide and the carbon multilayer film are aligned parallel to each other.

Furthermore, the diffraction pattern of the multilayer film was imaged and its Fourier transform image was obtained (see Figure 4(d)). As a result, it was found that the multilayer film has a spinel-type crystal structure.

At this time, as described above, the phase having a spinel-type crystal structure and the C-axis of zinc oxide are bonded parallel to each other, and therefore it can be seen that the phase and zinc oxide are cross-linked.

As is clear from Figure 3(e), the carbon film away from the zinc oxide surface was found to be a polycarbon phase in which graphite layers were stacked in multiple stages.

Example 2
A carbon compound was formed under the same conditions using the same manufacturing apparatus 10 as in Example 1, except that the substrate was changed from zinc oxide to a silicon substrate having a thickness of 0.625 mm.

Figure 4 shows a transmission image of the crystal structure near the interface between zinc oxide and the carbon film, observed using a high-resolution electron beam equivalent microscope (HRTEM: manufactured by JEOL Ltd.) with an acceleration voltage of 300 kV.

As is clear from Figure 4, in this embodiment, as in Example 1, it was found that the C-axis direction of silicon and the carbon multilayer film were aligned parallel to each other, and the diffraction pattern of the multilayer film was imaged and its Fourier transform image was obtained. As a result, it was found that this multilayer film has a spinel-type crystal structure.

In addition, the phase having a spinel crystal structure and the C-axis of zinc oxide are bonded parallel to each other, which indicates that the phase is cross-linked with silicon.

Furthermore, when the resistivity of the carbon compound having a spinel-type crystal structure phase obtained as described above was measured using the apparatus shown in FIG. 5, it was found to have a resistivity of about ^10-3 to ^10-5 Ω·cm at a thickness of 0.03 μm, which is as low as that of aluminum, that is, high conductivity.

It was also confirmed that the resistivity decreased from 10 ^-5 Ω·cm to 10 ^-8 Ω·cm when the thickness increased from 0.03 μm to 1.2 μm.

Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their modifications are included within the scope and gist of the invention, and are included in the scope of the invention and its equivalents as set forth in the claims.

REFERENCE SIGNS LIST 10 Carbon compound manufacturing apparatus 11 Cathode 12 Anode 13 ITO transparent conductive film 14 Electron source 15 Substrate 16 Gate electrode 17 Acceleration electrode 18 Acetylene-based gas

Claims (6)

It has a crystalline silicon substrate and a multilayer of carbon.
the C-axis direction of silicon constituting the crystalline silicon substrate and the multilayer film of carbon are aligned parallel to each other;
the carbon multilayer film is formed on the crystalline silicon substrate and includes a phase having a spinel type crystal structure;
The crystalline silicon substrate and the carbon multilayer are crosslinked . The stack according to claim 1 , wherein a C-axis direction of the silicon and a stacking direction of the carbon multilayer film are arranged parallel to each other. 3. The laminate according to claim 1, further comprising a phase having a structure in which graphite is laminated in multiple stages on the side opposite to the substrate, the phase being continuous with the phase having the spinel type crystal structure. 4. The laminate according to claim 1, wherein the resistivity at a thickness of 100 nm or less is 10 ⁻⁵ to 10 ⁻¹⁰ Ω·m. 5. A laminate according to claim 1, wherein the resistivity decreases with increasing thickness of the carbon compound. providing a cathode having an electron source disposed thereon and an anode having a crystalline silicon substrate disposed opposite the cathode;
a step of disposing a gate electrode on the cathode side and an acceleration electrode on the anode side between the cathode and the anode;
a step of flowing an acetylene-based hydrocarbon between the gate electrode and the acceleration electrode, and decomposing the acetylene-based gas by electrons emitted from the electron source and a voltage applied to the gate electrode to obtain at least one of ionized carbon and hydrocarbon;
and accelerating at least one of the carbon and the hydrocarbon by a voltage applied to the acceleration electrode and irradiating the crystalline silicon substrate of the anode.