JPH0321518B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention produces a carbon thin film having a highly oriented graphite structure by a relatively low-temperature pyrolytic chemical vapor deposition method (pyrolytic CVD method). Regarding the method, it is a technique that uses a specific hydrocarbon as a starting material and uses a single crystal substrate to grow a uniformly flat carbon deposit with metallic luster on the substrate, and is useful for creating new functional devices. This established a useful basic material manufacturing technology.

<Conventional technology and its problems> Artificial synthesis of graphite, which is chemically stable, does not undergo phase transformation even at high temperatures of 3000°C or higher, and has significant anisotropy in terms of thermal and electrical conductivity, usually requires a long period of time. A manufacturing process with extensive high temperatures and pressures was required. for example,
When using methane as a starting material, heat treatment at high temperature and high pressure is used to thermally decompose it at a high temperature (approximately 2000°C or higher) and to further improve orientation. Methods of forming carbon thin films using special organic compounds as starting materials and utilizing dehydrogenation reactions, dehydrohalogenation reactions, decarboxylation reactions, dehydration reactions, etc. are also frequently used. However, in this case, highly oriented carbon deposits cannot be obtained and it has not been possible to realize a functional material or a functional element. A method of obtaining fibrous carbon by treating polymer fibers at high temperatures has also been known for a long time. Although the material obtained by this method has already been considered for application as a structural material, its physical properties are unstable and reproducibility cannot be obtained, so it is necessary to utilize electrical and thermal properties (heteromorphism) Application to functional materials or functional devices is difficult.

<Purpose of the Invention> The present invention has been made in view of the above-mentioned current state of the art, and is intended to enable the realization of functional materials or functional devices that utilize anisotropy. The purpose of the present invention is to provide a method for producing a carbon thin film having a lead-containing structure at a relatively low temperature.

<Summary of the Invention> The method for producing a carbon thin film having a graphite structure according to the present invention uses an aromatic hydrocarbon or an unsaturated hydrocarbon as a starting material, uses a single crystal substrate as a substrate, and uses a relatively low-temperature pyrolysis chemical vapor phase. It is characterized by manufacturing a carbon thin film by a deposition method.

<Example> FIG. 1 is a block diagram of a carbon thin film production apparatus used in an example of the present invention.

Although hydrocarbon compounds can be used as starting materials, it is preferred to use aromatic or unsaturated hydrocarbons, which are thermally decomposed at about 1000°C.

Specific hydrocarbon names include benzene, biphenyl, anthracene, hexamethylbenzene,
Examples include 1,2-dibromoethylene, 2-butyne, acetylene, and diphenylacetylene. Depending on the type of hydrocarbon used, the method of supplying it to the reaction tube, such as the bubbler method, evaporation method, or sublimation method, as described below, may be used.
The supply rate is controlled at a constant rate of several millimoles or less per hour. This fixed amount is strongly dependent on the type of starting material. If the supply amount is set above this certain value, sooty carbon deposits 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 must satisfy the conditions that it does not deteriorate at a reaction temperature of approximately 1000°C. The bubbler method uses hydrogen, preferably argon, as a carrier gas. FIG. 1 shows the configuration of an apparatus using the bubbler method.
This device can also perform low-pressure CVD.
In this case, it is possible to achieve a more uniform thickness of the carbon deposit layer than in the case of atmospheric pressure CVD.

The manufacturing process will be explained below.

Argon gas is supplied from the argon gas control system 2 into the bubble container 1 containing benzene that has been purified by vacuum distillation to bubble the benzene, and the benzene is transferred to the quartz reaction tube 4 via the Pyrex glass tube 3. Feed molecules. At this time, the temperature of the liquid benzene in the bubble container 1 is kept constant, the argon gas flow rate is adjusted by the bubbles 5, and the amount of benzene molecules supplied into the reaction tube 4 is controlled to be constant at millimoles per hour. On the other hand, argon gas is flowed from the dilution line 6 to the glass tube 3 just before being fed to the reaction tube 4.
Optimize the number density of benzene molecules in argon gas. A sample stage 7 on which a growth substrate made of a single crystal of silicon or the like mentioned above is mounted is disposed in the reaction tube 4, and a heating furnace 8 is provided around the outer periphery of the reaction tube 4. The growth substrate of the reaction tube 4 is maintained at a temperature of about 1000° C. by the heating furnace 8 . When the benzene molecules are fed into the reaction tube 4, the benzene molecules are thermally decomposed within the reaction tube 4, and a carbon deposit with a metallic luster is generated on the growth substrate. Further, a white plate-like crystalline byproduct is produced at the rear of the reaction tube 4. This was confirmed to be biphenyl by infrared absorption spectrum, DSC, and gas chromatography. The gas in the reaction tube 4 is led out to the exhaust system 10 via the exhaust pipe 9 and removed from the reaction tube 4.

The density of carbon deposits obtained using a floating method using a mixed solution of carbon tetrachloride and methane dibromide was measured. As a result, the thin film of carbon deposit had a density α=2.1±0.1 g/cm ² . Furthermore, according to infrared absorption experiments, carbon deposits contain −CH,
It was found that no absorption based on the presence of -CH ₂ and -CH ₃ was observed.

FIG. 2 shows a schematic diagram of the RHEED pattern on the surface of a carbon thin film deposited by the above method on a silicon single crystal substrate. In the figure, (002), (004), and (006) represent the plane index of graphite crystal, and the diffraction pattern becomes a spot. It was found that the C-axis orientation was much better than that of conventional carbon thin films deposited using conventional methods.

Benzene molecules introduced into reaction tube 4 are at 1000℃
The material is heated to a temperature of about 100 to 100°C to thermally decompose, and is sequentially grown and formed on the growth substrate. In this case, the grown carbon thin film inherits the crystallinity of the growth substrate and becomes a thin film with good crystallinity, and since benzene has the same six-membered ring structure as graphite, it is High orientation is achieved at low temperatures. In addition, since the amount of benzene molecules introduced into the reaction tube 4 is controlled at a constant level, the thickness of the carbon deposit formed on the growth substrate is uniform, and together with improved crystallinity, it has a metallic luster and mirror surface. A thin film exhibiting this is obtained.

<Effects of the Invention> According to the method of the present invention using an aromatic hydrocarbon or an unsaturated hydrocarbon as a starting material and using a single crystal substrate as a substrate, by using an aromatic hydrocarbon or an unsaturated hydrocarbon as a starting material, Due to this effect and the effect of using a single crystal substrate, a carbon thin film having an anisotropic graphite structure with good crystallinity and high orientation can be produced at a relatively low temperature. This is expected to promote application to functional electronic materials.

[Brief explanation of the drawing]

Fig. 1 is a block configuration diagram of a carbon thin film production device used to explain one embodiment of the present invention, Fig. 2 is a schematic diagram of the RHEED pattern on the surface of the carbon thin film according to the embodiment, and Fig. 3 is a schematic diagram of the RHEED pattern on the surface of the carbon thin film according to the embodiment. FIG. 2 is a schematic diagram of a RHEED pattern. 1... Benzene container, 2... Argon gas control system, 3... Glass tube, 4... Reaction tube, 6... Dilution line, 7... Sample stand, 8... Heating furnace.

Claims (1)

[Claims] 1. Using an aromatic hydrocarbon or an unsaturated hydrocarbon as a starting material and using a single crystal substrate as a substrate, the hydrocarbon is thermally decomposed at a low temperature, thereby forming a chemical vapor phase on the single crystal substrate. A method for producing a carbon thin film having a graphite structure, the method comprising forming the carbon thin film by a deposition method.