JPH0413425B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for synthesizing a carbon intercalation compound in which metal atoms or metal compounds are inserted between layers of a layered structure of graphite.

<Prior art and its problems> It has long been known that graphite intercalation compounds can be synthesized by focusing on the layered structure of graphite and inserting metal atoms, metal halides, acids, etc. between the layers. . Traditional synthetic methods utilize control of the vapor pressure of the intercalating material or electrochemical reactions to
A different substance is inserted between layers of natural graphite or highly oriented graphite. However, in these methods, the graphite intercalation compound obtained is not susceptible to heat, moisture,
It is unstable to oxygen in the air, and the substances that can be inserted are limited to those that can easily enter and exit between the layers. Applications to batteries that take advantage of the easy ingress and egress of intercalated substances are almost being put into practical use, but on the other hand, applications to electronic materials that utilize the anisotropy of intercalation compounds by fixing intercalated substances between layers are currently in progress. However, it is not bearing fruit.

<Objective of the Invention> The present invention aims to provide a new manufacturing technology for synthesizing a carbon intercalation compound by simultaneously inserting metal atoms or metal compounds between the layers of a graphite structure and at the same time synthesizing a carbon deposit exhibiting metallic luster. This is the purpose.

<Summary of the Invention> Graphite is a metalloid in which there are approximately the same number of electron carriers and hole carriers. Therefore, if an electron-donating or electron-withdrawing atom or compound can be inserted into this semimetal, an N-type or P-type electrical conductor can be realized. This has been known for a long time, and since the insert has a stage structure between graphite layers, research has focused on the unique electrical, optical, or magnetic properties caused by this structure. In order to synthesize a graphite intercalation compound, the invention uses a hydrocarbon pyrolysis CVD method to produce carbon deposits with metallic luster, instead of the method of later introducing substances to be inserted into natural or synthesized highly oriented graphite. It is characterized in that it makes it possible to mass-produce carbon intercalation compounds with good reproducibility by introducing atoms or compounds to be inserted during the process of synthesizing carbon intercalation compounds. The material intercalated between the layers in the method of the present invention is thermally decomposed into metal atoms or metal compounds at the temperature at which metallic luster carbon deposits are formed (e.g., about 600°C to 1100°C), and is formed into metal atoms or metal compounds in the carbon deposits. It is inserted between the existing graphite layer structure. This is because when hydrocarbons and organometallic raw material gases are simultaneously thermally decomposed in the same reaction system, the reaction system contains carbon bodies with a hexagonal network planar structure produced by the decomposition of the hydrocarbons and metals produced by the decomposition of the organometallics. Because gas-phase pyrolytic carbon has the special characteristic of being formed by stacking carbon bodies with a hexagonal network planar structure, layered deposition of carbon bodies with a hexagonal network planar structure occurs. This is because at the same time, metal atoms are also deposited and captured between them. Therefore, in addition to conventionally used inserts such as highly reactive alkali metals, halogens, strong acids, and strong bases, metals or metal compounds with low reactivity can also be used as inserts. Carbon deposits with metallic luster not only have a two-dimensional hexagonal structure based on carbon SP ² bonds, but also have some carbon SP ³ bonds, so metal atoms or metal compounds inserted between graphite layers are Effectively prevents entry and exit from between the layers. By thus fixing the insert between the layers of the graphite structure and utilizing the anisotropy of the graphite structure, it becomes possible to apply carbon intercalation compounds to electronic materials.

<Example> The drawing is a block structural diagram of a carbon intercalation compound generating apparatus used in one example of the present invention.

The hydrocarbon compound used as a starting material is preferably an aliphatic hydrocarbon, preferably an aromatic hydrocarbon or an unsaturated hydrocarbon.
It is thermally decomposed before and after. Specific hydrocarbon names include cyclohexane, n-hexane, benzene, biphenyl, anthracene, hexamethylhensen, 1,2-dibromoethylene, 2-butyne,
There are acetylene, diphenylacetylene, etc. Depending on the type of hydrocarbon used, a bubbler method, evaporation method, sublimation method, or the like is used as the method of supplying the hydrocarbon to the reaction tube, which will be described later, and the supply rate is controlled at a constant amount of several mmol or less per hour. This constant value strongly depends on the type of starting material. If the supply amount is set above this certain value, the surface unevenness of the resulting carbon deposit will become severe and a soot-like carbon deposit will be generated.

Single-crystal substrates on which carbon thin films are formed include silicon, sapphire, silicon carbide (α-type and β-type),
Using boron nitride, hard graphite, highly oriented graphite, etc.
It is necessary to select a material that satisfies the conditions of not deteriorating at a reaction temperature of approximately 1000°C.

Benzene molecules are supplied to a quartz reaction tube 3 via a Pyrex glass tube 2 from a raw material container 1 containing benzene that has been purified by vacuum distillation. Benzene molecules evaporated from the raw material container 1 are supplied to the glass tube 2 through the opening/closing operation of the pot 4, and then the glass capillary 5 interposed in the glass tube 2.
The amount of benzene molecules supplied is determined by In addition, a chamber 6 containing tetraphenyltin is located in the middle of the glass tube 2.
Tetraphenyltin is then mixed and benzene molecules and tetraphenyltin are simultaneously supplied to the reaction tube 3. The glass tube 2 is covered with a heating tape 7 to keep it warm. The glass tube 2 and the reaction tube 3 are connected to each other by a Pyrex-quartz return joint 8. The reaction tube 3 is inserted into a heating furnace 9 and heated to a reaction temperature, and a holding table 10 on which a single crystal substrate on which a carbon deposit is to be grown is placed inside the reaction tube 3. The remainder of the steam introduced into the reaction tube 3 is exhausted to the outside via the exhaust pipe 11.

Raise the temperature of the heating furnace 9 to bring the inside of the reaction tube 3 to 900~
Benzene molecules and tetraphenyltin molecules, which are maintained at about 1000° C. and whose supply amount is controlled by a capillary 5, are supplied into the reaction tube 3 at a constant amount of a total of several millimoles or less per hour. The benzene molecules introduced into the reaction tube 3 are thermally decomposed, and a carbon deposit exhibiting metallic luster is grown and formed on the single crystal substrate. At this time, tetraphenyltin is also thermally decomposed and tin atoms are inserted between the layers of the carbon deposit, so that the resulting carbon deposit becomes a carbon intercalation compound. The produced carbon intercalation compound inherits the crystallinity of the single-crystal substrate and becomes a thin film with good crystallinity, and high orientation can be achieved at a lower temperature than in the past. Furthermore, since the benzene molecules and organometallic tetraphenyltin molecules introduced into the reaction tube 3 are controlled to a constant level, the thickness of the carbon laminate produced on the substrate is uniform, and it exhibits metallic luster with improved crystallinity. A surface is obtained.

The uniform presence of tin was confirmed by taking an X-ray image of tin atoms in the carbon thin film using an electron microscope. Furthermore, according to X-ray diffraction, in addition to the (002) reflection of graphite, it was also possible to observe a reflection corresponding to the sum of the atomic radius of tin and the interlayer distance of graphite.

Note that similar results were obtained when tetraphenyl lead was used in place of tetraphenyltin as the organometallic compound forming the intercalation compound.

<Effects of the Invention> As described above, the method for synthesizing a carbon intercalation compound with metallic luster according to the present invention makes it possible to efficiently and stably insert various metal atoms or metal compounds between the layers of a layered structure of graphite. It is expected that new electronic materials can be created using this anisotropy.

[Brief explanation of drawings]

The accompanying drawing is a block diagram of a carbon intercalation compound generating apparatus used in one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Raw material container, 2... Glass tube, 3... Reaction tube, 4... Capillary, 9... Heating furnace, 10... Holding stand, 11... Exhaust pipe.

Claims (1)

[Claims] 1. Depositing a carbon thin film layer on a substrate by thermally decomposing a hydrocarbon in a reaction system, and simultaneously thermally decomposing an organic metal in the reaction system to insert metal atoms of the organic metal between the layers of the carbon thin film. A method for synthesizing carbon intercalation compounds characterized by: