JPH048366B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field> The present invention relates to a method for synthesizing a graphite intercalation compound in which metal atoms are inserted between the layers by simultaneously thermally decomposing a hydrocarbon compound and a metal halide.

<Conventional techniques and their problems> Graphite intercalation compounds have traditionally been synthesized by a method in which a different substance is inserted between the layers of natural graphite or highly oriented graphite by bringing an intercalation substance into contact with graphite in a liquid or gas phase. There is. However, this method is limited to cases in which the chemical species inserted often have a low melting point or a relatively high vapor pressure, allowing easy access to and from the interlayers. For this reason, graphite intercalation compounds obtained using conventional methods are unstable to heat, moisture, oxygen in the air, etc., and only alkali metals and alkaline earth metals have been confirmed as intercalated metal elements. It's just that. In order to realize functional electronic materials or functional devices that utilize the anisotropy of graphite intercalation compounds, it is necessary to establish a technology to stably fix metal atoms between layers and synthesize intercalation compounds that exhibit a remarkable stage structure. .

<Purpose of the Invention> The present invention has been made in view of the above-mentioned conventional situation, and involves inserting metal atoms between the layers of the graphite structure during the growth process of pyrolytic carbon or pyrolytic graphite, thereby creating a stable and prominent stage even in the air. The purpose of this invention is to provide a new manufacturing technology for synthesizing intercalation compounds exhibiting a structure.

<Summary of the invention> In order to synthesize a graphite intercalation compound, the present invention employs a method of simultaneous thermal decomposition of a hydrocarbon compound and a metal halide, instead of the method of introducing a substance to be inserted later into natural or synthesized highly oriented graphite. By introducing a certain amount of metal atoms to be inserted into the formal process of carbon deposits with metallic luster or highly oriented pyrolytic carbon, graphite intercalation compounds exhibiting a remarkable stage structure can be synthesized with good reproducibility. The present invention is characterized in that by controlling the mixing ratio of both, it is also possible to control the number of stages of the intercalation compound.

<Example> The drawing is a block diagram of a carbon intercalation compound generating apparatus used in one example of the present invention. Hydrocarbon compounds used as starting materials for graphite include aromatic compounds or unsaturated compounds (e.g. benzene, biphenyl, anthracene, hexamethylbenzene, acetylene, 1,2-dibromoethylene, 2-butyne, diphenylacetylene, etc.) is preferred, while metal halides used as starting materials for the metal to be inserted include tin tetrachloride, titanium tetrachloride, tungsten hexafluoride, molybdenum hexafluoride, chromium hexafluoride, technetium hexafluoride, Those with relatively low melting points such as vanadium tetrachloride and rhenium hexafluoride are desirable. These 2
Various starting materials are simultaneously thermally decomposed at a reaction temperature of around 1000°C. As the substrate on which the carbon intercalation compound is formed, single crystals such as quartz glass, silicon, sapphire, silicon carbide (α-type and β-type), boron nitride, Kitshu graphite, or highly oriented graphite are used.
It must satisfy the condition that it does not deteriorate even at a reaction temperature of 1000℃.

A normal pressure bubbler method or a reduced pressure method is used to supply raw materials to the reaction tube. In either method, by controlling the supply amount and ratio of each raw material as described later, a carbon intercalation compound exhibiting a remarkable staging structure can be obtained, and the number of stages can also be controlled. In the normal pressure bubbler method, hydrogen or argon gas is used as a carrier gas. Although the drawing shows a device configuration that uses the normal pressure bubbler method, it is also possible to use the low pressure CVD method with this device.
In this case, it is possible to achieve a more uniform film thickness of the carbon intercalation compound than in the normal pressure bubbler method.

The manufacturing process will be explained below.

Argon gas is supplied from the argon gas control system 2 into the bubble containers 1 and 1' in which benzene and tin tetrachloride, which have been purified by vacuum distillation, are collected, respectively, to bubble benzene and tin tetrachloride independently, Benzene molecules and titanium tetrachloride molecules are simultaneously fed into a quartz reaction tube 4 through a Pyrex glass tube 3. At this time, the temperatures of the liquid benzene and liquid tin tetrachloride in the bubble containers 1 and 1' are kept constant, and the argon gas flow rate is adjusted independently with the valve 5. The amount of supply to each area is controlled at a constant level. On the other hand, argon is flowed through the dilution line 9 to optimize the number density and flow rate of the benzene molecule and tin tetrachloride mixed gas fed to the reaction tube 4. Reaction tube 4
A sample stage 7 on which a growth substrate made of a single crystal of silicon or the like mentioned above is mounted is installed, and a heating furnace 8 is provided around the outer periphery of the reaction tube 4 .
The growth substrate in the reaction tube 4 is maintained at a temperature of about 1000° C. by the heating furnace 8 .

The mixed gas of benzene and tin tetrachloride introduced into the reaction tube 4 is heated to a temperature of around 1000°C.
Each gas is pyrolyzed simultaneously. On this occasion,
The carbon deposit formed on the substrate incorporates tin atoms generated by thermal decomposition of tin tetrachloride in the reaction atmosphere during its growth process, and the resulting carbon deposit is a carbon intercalation compound with tin atoms inserted. Become.

In the obtained carbon intercalation compound, the distance between the carbon layers sandwiching the tin atomic layer was 4.2 Å according to an X-ray diffraction experiment.
It was confirmed that

Furthermore, when the supply amount of tin tetrachloride introduced into the reaction tube 4 is changed, the number density of tin atoms produced by thermal decomposition also changes, so the period (staging) of the tin atomic layer between carbon layers changes. Control is also possible, and it has been confirmed that this carbon intercalation compound turns silver in color when the tin atomic layer is most densely packed (first stage). In addition, it was confirmed by a similar method that the stage structure of the intercalation compound obtained in this way did not change even if it was left in the air.

Note that similar results were obtained when titanium tetrachloride was used instead of tin tetrachloride as the metal halide forming the intercalation compound.

<Effects of the Invention> As described above, the method for synthesizing a carbon intercalation compound according to the present invention makes it possible to stably insert various metal atoms between the layers of the layered structure of graphite, and also makes it possible to control the number of stages. Since this is possible, it is possible to create new functional electronic materials that utilize anisotropy.

[Brief explanation of drawings]

The accompanying drawing is a block diagram of a carbon intercalation compound generating apparatus for explaining one embodiment of the present invention. 1, 1'...Bubble container, 2...Argon gas control system, 3...Glass tube, 4...Reaction tube, 6,9
...Dilution line, 7...Sample stand, 8...Heating furnace.

Claims (1)

[Claims] 1. Pyrolytic decomposition of an aromatic compound or unsaturated compound in a reaction system to deposit a metallic luster or highly oriented carbon thin film layer on a substrate, and at the same time thermally decomposing a metal halide with a relatively low melting point in the reaction system. A method for synthesizing a graphite intercalation compound, comprising inserting metal atoms of the metal halide between the carbon thin film layers.