JPH01197391A - Method for synthesizing diamond - Google Patents

Abstract

PURPOSE:To precipitate and deposit diamond contg. less impurities efficiently at a high deposition rate on a base material by exciting gaseous raw materials consisting of CO, H2 and oxygen-contg. compds. except CO and CO2 and bringing the same into contact with the surface of the base material. CONSTITUTION:The gaseous raw materials consisting of the gaseous carbon monoxide, the gaseous hydrogen and the oxygen-contg. compds. except the carbon monoxide and carbon dioxide are prepd. The oxygen itself or the compds. which generate oxygen by decomposing at a high temp. are used for the oxygen-contg. compds.; the more specific examples include water, hydrogen peroxide water, methanol, acetaldehyde, etc. The resulted gaseous raw materials are then introduced from an introducing port 1 into a reaction vessel 2 and are subjected to plasma decomposition by the microwaves or high frequency waves introduced therein by a waveguide 3, by which said materials are activated. The carbon in the excited state contained in the activated gases is deposited on the base material 4, by which the diamond film is obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for synthesizing diamond, and more specifically, a method that can efficiently produce diamond with a high deposition rate on a substrate and with few impurities. Concerning diamond synthesis methods.

[Prior art and its problems] In recent years, diamond synthesis technology has made remarkable progress, including various protective films for tools and optical materials.

Diamond has come to be widely used in electronic materials, chemical engineering materials, etc.

Methods for synthesizing such diamonds include pyrolysis synthesis, in which hydrocarbon gas is thermally decomposed using a filament, and diamond is deposited on the surface of a seed crystal, and diamond film is formed on the substrate surface using a non-uniform chemical reaction. A chemical transport synthesis method to obtain carbon, a plasma decomposition synthesis method in which hydrocarbon gas is plasma decomposed to deposit diamond on a substrate, or a hot cathode PIG gun, a cold cathode PIG gun, a sputter gun, etc. are used to knock out carbon. ζ is known as an ionization vapor deposition method in which carbon is ionized in an arc discharge space and then deposited on a substrate.

By the way, the conventionally proposed method uses hydrocarbon or a mixed gas of hydrocarbon and hydrogen as the jX material gas, but the
JP-A-58-110494, JP-A-58-135
117, JP-A-59-FI3732, JP-A-60-103099, etc.) In these methods, in order to improve the diamond deposition rate, When using a mixed gas as a raw material gas, it is necessary to increase the amount of hydrocarbons.

By increasing the amount of hydrocarbons, the diamond deposition rate increases, but on the other hand,
There is a problem in that impurities other than diamond, such as graphite, are mixed into the resulting diamond film.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for synthesizing diamond, which solves the above-mentioned problems and allows diamond to be synthesized on a substrate at a high deposition rate, efficiently, and with less impurities.

[Means for Solving the Problems] In order to solve the above-mentioned problem i, the inventor has made extensive studies and found that in the method of synthesizing diamond in the gas phase, conventional carbonization is not used as a carbon source. When carbon monoxide gas, hydrogen gas, and oxygen-containing compounds are used instead of hydrogen gas, diamonds with fewer impurities can be deposited on the substrate at a faster deposition rate and more efficiently than with conventional methods. This invention was achieved by discovering that it is possible to obtain a membrane.

That is, the configuration of the present invention is to bring a gas obtained by exciting a raw material gas consisting of carbon monoxide gas, hydrogen gas, and an oxygen-containing compound other than carbon monoxide and carbon dioxide onto a base material. This is a diamond synthesis method characterized by precipitating diamond.

In the method of the present invention, a raw material gas consisting of carbon monoxide gas, hydrogen gas, and an oxygen-containing compound other than carbon monoxide and carbon dioxide, or a mixed gas containing these gases can be used.

There are no particular restrictions on the carbon monoxide gas, and for example, it can be produced by sufficiently refining generator gas or water gas obtained by hot reaction of coal, coke, etc. with air or steam.1 Usually reprinted. Carbon monoxide gas in a cylinder or cracked gas obtained by decomposing methanol can be used.

Since methanol cracked gas contains hydrogen gas, carbon monoxide gas and hydrogen gas in the raw material gas in this invention may be prepared by simply adding hydrogen gas to this cracked gas. Use of this cracked gas avoids the dangers associated with using carbon monoxide gas in cylinders.

The hydrogen gas can be used in combination with carbon monoxide gas.1. ! 8 or form atomic hydrogen etc. by electric discharge. This atomic hydrogen and the like is thought to have the function of removing the graphite-structured carbon that is precipitated at the same time as the diamond, and the function of maintaining the 5p3 structure of the carbon atoms in the precipitated diamond crystals even at high temperatures.

Examples of hydrogen gas that can be used include water electrolysis,
Those obtained by denaturation of water gas, reaction of iron and steam, gasification of petroleum, denaturation of natural gas, gasification of coal, etc. can be sufficiently purified and used.

In the method of the present invention, the oxygen-containing compounds other than carbon monoxide and carbon dioxide are not particularly limited as long as they are oxygen itself or decompose at high temperatures to generate oxygen.

As something that decomposes at high temperatures and generates oxygen.

For example, water, hydrogen peroxide, or methanol, ethanol, propatool, isopropyl alcohol, butanol, isobutyl alcohol.

Aliphatic alcohols such as S-butyl alcohol and t-butyl alcohol, alicyclic alcohols such as cyclopentanol and cyclohexanol, aromatic alcohols such as phenol and naphthol, ethylene glycol,
Polyhydric alcohols such as diethylene glycol, propylene glycol, dipropylene glycol, and glycerin, aldehydes such as formaldehyde, acetaldehyde, and acrolein, acetone, ethyl methyl ketone,
Ketones such as inbutyl ketone, aliphatic carboxylic acids and their anhydrides such as acetic acid, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, and benzoic acid, phthalic acid, terephthalic acid, isophthalic acid, and phthalic anhydride. Acids, aromatic carboxylic acids such as trimellitic acid, trimellitic anhydride, pyromellitic acid, and pyromellitic anhydride, and their anhydrides can be mentioned.

Among the oxygen-containing compounds, oxygen, water and hydrogen peroxide are preferred.

In the method of the present invention, an inert gas may be used together with the source gas.

The inert gas functions as a carrier gas for the raw material gas, and also functions to protect the quartz tube for plasma generation by mixing with the hydrogen gas and flowing it to the wall surface of the reaction tube. Furthermore, it also has the effect of stabilizing plasma as a plasma gas. Examples of the inert gas that can be used include argon gas, neon gas, xenon gas, and nitrogen gas. Among these, argon gas is particularly preferred.

In the method of the present invention, it is used as a raw material gas consisting of the carbon monoxide gas, hydrogen gas, and an oxygen-containing compound other than carbon monoxide and carbon dioxide.

The usage ratios of carbon monoxide gas, hydrogen gas, and the oxygen-containing compound in the raw material gas are as follows when expressed in mol%.

In other words, carbon monoxide gas has a ratio of 0.05 to hydrogen gas.
The amount of the oxygen-containing compound is 0.05 to 10 mol%, preferably 0.1 to 10 mol%, based on the total amount of gas.

If the amount of the oxygen-containing compound is less than 0.05 mol% or more than 10 mol%, no improvement in the diamond deposition rate may be observed, or if impurities such as graphite are mixed in. There is.

In the present invention, a diamond film is formed on Omura.

The base material may be of various shapes, such as a plate shape such as a disk shape or a square plate shape, a rod shape, or a tube shape.

Further, as the material of the base material, for example, silicon,
Metals such as aluminum, titanium, tungsten, molybdenum, cobalt, and chromium, their oxides, nitrides and carbides, such as WC-Co alloys, WC-
Cemented carbide such as TiC-Go alloy JC-TiC-TaC-Co alloy, zOs-Fe system, 4iC-Xi system, Tic-Co system, 84C-Fe system, TiN system, Ti
Cermets such as C-TiN and various ceramics can be used.

Means for decomposing the raw material gas to obtain a gas containing excited carbon include a plasma generation method using a thermionic emitting material such as a hot filament, a plasma generation method using a direct current or alternating current arc discharge method, and a high frequency induction method. Any method such as plasma generation method or microwave discharge method can be adopted, and conventionally known methods such as sputtering method, ionization vapor deposition method, ion beam evaporation method, thermal filament method, chemical transport method, etc. can be used. be able to.

In the method of this invention, the reaction proceeds under the following conditions, and diamond is precipitated in the gas phase.

The reaction pressure is usually 10-' to 103 Torr, preferably.

There is a range of 1 to 800 Torr.

The reaction temperature is 400 to 1,200°C, preferably 45°C.
If the reaction temperature, which is 0 to 1,100°C, is less than 400°C, the diamond deposition rate may not be improved or diamond may not be precipitated.

1. If the temperature exceeds 200°C, the diamond may be etched away and no improvement in the diamond deposition rate may be observed.

The reaction under the above conditions can be carried out using, for example, a reaction apparatus as shown in FIG.

FIG. 1 is a conceptual diagram of a reaction apparatus that can be used in the method of the present invention.

That is, a raw material gas containing carbon monoxide gas, hydrogen gas, and an oxygen-containing compound is introduced into the reaction vessel 2 from the raw material gas inlet 1 . The raw material gas introduced into the reaction vessel 2 is plasma decomposed and activated by microwaves or high frequency waves guided by the waveguide 3, and the excited carbon contained in this activated gas is transferred onto the base material 4. Alternatively, if necessary, the diamond film is deposited on the substrate 4 whose surface has been cleaned to form a diamond film.

The diamond that can be obtained by the method of the present invention can be suitably used for various types of protective SS such as surface protective films for tools, optical materials, fitter materials, chemical industrial materials, etc., and especially for cutting tools and It can be suitably used as a surface protective film for polishing tools.

[Example] Next, Examples and Comparative Examples of the present invention will be shown to further specifically explain the present invention.

(Example 1) A microwave power source with a frequency of 2 to 45 GHz was used, a silicon wafer was used as a base material, and carbon monoxide, hydrogen, and oxygen were used as gases. Carbon monoxide flow 170scc
m (66.7 mol%), hydrogen flow rate 30 sccm (2
8,6 mol %), oxygen flow ii 5 sccm (4,
Diamond was synthesized under a pressure of 50 torr for 1 hour under a pressure of 50 torr to obtain a 20 IL thick composite on a substrate controlled at 900°C. Raman branch analysis was performed on the obtained compost.

We confirmed that the diamond was free of impurities.

(Example 2) In Example 1, WC-Co (Coa11
2%) and 8 sccm of water instead of oxygen.
(5.7 mol%) Nt stitch was used to synthesize 1:0m tm diamond, and a thickness of 15ILm was deposited on the substrate.
A compost plant was obtained. When the obtained compost was subjected to Raman spectroscopic analysis, it was confirmed that it was a diamond free of impurities.

[Effects of the Invention] According to the present invention, diamond can be synthesized using a mixed gas of carbon monoxide, hydrogen, and an oxygen-containing compound as a raw material, so that 1. It is possible to provide an industrially advantageous method for synthesizing diamond, which has effects such as being able to form diamonds without any impurities.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of a reaction apparatus that can be used in the method of the present invention. 1...-raw material gas inlet, 2, φ, reaction vessel, 3...
Waveguide, 4. Base material. Figure 1

Claims (1)

[Claims] (1) By bringing a gas obtained by exciting a raw material gas consisting of carbon monoxide gas, hydrogen gas, and an oxygen-containing compound other than carbon monoxide and carbon dioxide onto the substrate,
A diamond synthesis method characterized by precipitating diamond.