JPS59184791A - Vapor phase synthesis of diamond - Google Patents

Abstract

PURPOSE:To synthesize artificial diamond having complete crystalline property on the diffusion layer by charging a base body having a surface diffusion layer into a reaction furnace, specifying the distance between the diffusion layer and a filament, and temperature condition, and flowing a regulated gaseous reaction mixture. CONSTITUTION:Over one kinds among C, N, and B are diffused on the surface of a base material comprising a metal (or alloy) of 4a, 5a, or 6a. Said surface treated base material is charged in a reaction furnace, and a filament comprising W, Ta, Mo, or graphite is positioned at a position separated 0.5-3cm apart from the surface-diffusion layer of the base material. In this state, a gaseous reaction mixture having regulated proportion of CH4/H2 to 0.001-0.05 is flowed through said filament to collide with the surface diffusion layer. The reaction is carried out by maintaining the temp. of the surface of the diffusion layer at 500-1,200 deg.C, and the temp. of the filament at 1,800-2,500 deg.C. By this method, particles or film of artificial diamond having complete crystalline property are formed on the surface diffusion layer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for depositing diamond in the form of granules or films using a vapor phase synthesis method.

Since diamond is the hardest material in existence and has excellent thermal conductivity and electrical insulation, it is used in a wide range of fields as an industrially useful material.

In addition to naturally occurring diamonds, we also use ultra-high pressure synthesis equipment to produce diamonds. Graphite powder is placed together with a catalyst in an ultra-high pressure generation container at a temperature of 1,600°C or higher and a pressure of 60°C.
There is an artificial diamond produced by subjecting graphite to phase transformation into diamond through a reaction at high temperatures and pressures exceeding 1,000 kb. This artificial diamond can be made with various particle sizes by fully controlling the particle size of the raw material powder and the reaction time.
However, not only is the equipment itself large-sized, but there is a limit to the amount of production per time, so there is a problem in terms of productivity, and it is inevitable that the cost system will be used. I can't do it. In addition, there is a method of synthesizing diamonds [for example, a method of converting graphite into diamond by using the impact force from the explosion of gunpowder, but the artificial diamonds produced by this method cannot be produced by the ultra-high pressure synthesis method described above. Although it is somewhat cheaper than those manufactured in China, it is difficult to obtain one with perfect crystallinity, and therefore there are problems in terms of properties.

Therefore, from the above-mentioned viewpoint, the present inventors conducted research in order to manufacture perfectly crystalline artificial diamonds with high productivity and at low cost without using large press equipment, etc. As a result, As a substrate on which diamond is deposited, a normal surface is formed on the surface of a substrate member made of one of the metals of groups 4a, 5a, and 6a of the periodic table of elements, or an alloy mainly composed of these metals. Carbon (C) by carbonization, surface nitridation, or surface boronization.

Using a surface-treated base part A'A'k having a surface diffusion layer formed by completely diffusing one or more of nitrogen (N) and boron (B), by a vapor phase synthesis method, At a position 0.5 to 3 c1n away from the surface diffusion layer of the base member,
With a filament made of VJ, Ta, Mo, or graphite positioned, the capacity ratio of CH4 and H2, that is, OH4/Hzk 0.001 to 0.05 V
C. While flowing the adjusted mixed reaction gas so as to pass through the filament and hit the surface diffusion layer, the temperature of the surface diffusion layer is 2500 to 1200 °C, and the temperature of the filament is 1800 to 2500 °C. It was discovered that when the reaction was carried out, diamond with perfect crystallinity was formed in the form of grains or films on the surface diffusion layer.

In addition, in the method of the present invention, when the distance between the surface diffusion layer and the filament is relatively small within the surrounding area, the density of diamond precipitation nuclei becomes high; Because they are arranged side by side densely, they are film-like, but when the separation distance becomes too large, they become granular.In addition, the surface diffusion layer is essential for uniformly precipitating diamond nuclei with a fast reaction. Therefore, if this surface diffusion does not exist, the precipitation of diamond will be extremely slow and it will not be possible to uniformly precipitate diamond nuclei at the desired rate.

VC, the reason why the manufacturing conditions are limited to the above-mentioned conditions in the method of the present invention will be explained.

(a) Temperature of the filament The filament decomposes methane (CH4), and at the same time,
It is thought that the C and H2 formed as a result are activated and contribute to diamond formation, but the temperature is 18
Below 00°C, the reaction gas is not activated sufficiently,
On the other hand, if the temperature exceeds 2500°C, thermal radiation becomes too large, and in either case, diamond formation becomes insufficient.
The temperature was set at 0°C.

(b) Temperature of the surface diffusion layer The temperature of the surface diffusion layer is determined by the radiant heat from the filament and the heating temperature of the second part itself.
Below 1200, the diamond precipitation rate is slow;
Since diamond does not precipitate at a temperature exceeding .degree. C., the temperature was set at 500 to 1200.degree. C. above that temperature.

(C) Ratio of CH4/H2 in the mixed reaction gas If this ratio is less than 0001, the rate of diamond formation is extremely slow, while if this ratio exceeds 0.05, graphite will be mixed in the diamond. , C
The ratio of H4/H2 was determined to be 0001 to 0.05.

(d) Surface diffusion layer of base member and filament!・Distance between If this distance tfl is less than 0.5 cm, the temperature of the surface diffusion layer will exceed 1200°C due to the radiant heat of the filament, and diamond precipitation will not occur. When the distance exceeds 3 m, the density of diamond nucleus formation decreases rapidly, so the distance was set at 05 to 3 cm.

Further, when carrying out the method of the present invention, the reaction atmosphere is preferably a 2-m vacuum atmosphere with a pressure within the range of 5 to 100 torr, and a pressure less than 5 torr is preferable. This is because the precipitation rate is extremely slow, and on the other hand, if the pressure exceeds 100 torr, graphite will be mixed in.

Note that the diamond synthesized by the method of this invention contains W, which is a filament constituent, as an unavoidable impurity.
, Mo, Ta, etc. may be contained in the range of 1 to 10 atoms, but such an impurity content does not have any adverse effect on the diamond properties.

At the end, the method of the present invention will be specifically explained using examples.

Each of the examples had the component composition shown in Table 1, and IOm
A base part having dimensions of mx thickness: 2 mx is prepared, and the surface of this base part is treated with the surface treatment method shown in Table 1, that is, the gas surface carbonization method.

A surface diffusion layer having an average layer thickness shown in Table 1 is formed under normal conditions using one of the gas surface nitriding method, solid surface carbonization method, and solid surface boriding method, and then the resulting surface treatment is performed. The surface diffusion layer of the base portion Ay+ was subjected to a gas phase synthesis reaction for diamond formation under the conditions also shown in Table 1, thereby forming methods 1 to 10 of the present invention and comparative method 1.
- 7 were carried out, and after the execution, the average layer thickness of the synthetic diamond formed on the surface was measured and the state thereof was observed. These results are also shown in Table 1.

In addition, Comparative Methods 1 to 7 are all conducted under conditions where the gas phase synthesis conditions for diamond formation are outside the scope of this invention (the conditions marked with * in Table 1 are outside the scope of this invention). This was carried out at

From the results shown in Table 1, it can be seen that in all methods 1 to 10 of the present invention, diamonds were synthesized in good condition, whereas in comparative methods 1 to 7, diamonds were synthesized in satisfactory condition in all cases. It is clear that no synthesis takes place.

Note that all of the diamond 'l-J synthesized by methods 1 to 10 of the present invention exhibited hardness and electrical resistance equivalent to those of natural diamond.

According to the method of the present invention, a completely crystalline artificial diamond can be grown into a surface diffusion layer of a substrate without using large-scale equipment and with high productivity. Diamond can be synthesized in the form of granules or films. Therefore, when diamond is synthesized in the form of granules, it is mechanically scraped off from the surface of the component to form a powder, and then polished with a whetstone or polished. Alternatively, it can be used as a raw material powder for powder metallurgy, and when formed into a thin film, it can be used as a base material. Alternatively, it may be used as an IC or LSI that requires thermal conductivity or electrical insulation, and may also be an insulating film,
I3. In combination with doping with components such as P and M, it can be applied to applications such as semiconductor films, etc., thereby bringing about useful effects in industry.

Applicant: Mitsubishi Metals Co., Ltd. Agent: Tomi 1) Written amendment by Kazuo and one other person (Jiri, September 2, 1981, Kazuo Wakasugi, Commissioner of the Japan Patent Office, 1, Patent Application No. 57043-1982, Patent Application No. 57043, Patent Application No. 58-57043) Name of the invention Diamond Qi 4 eye synthesis method 3 Person making the amendment 4 Representative IJ Kasui Tokyo Chiyo 1111-ku Kami+11.l Nishikicho-
1] No. 23 Sponsored (1) Specification, page 7, Detailed Description of the Invention, line 1, ``Pressure within the range of 15 to 1.00 torr''
"Pressure within the range of 5 to 100 torr using a Virani set vacuum gauge (this pressure corresponds to 01 to 10 torr when measured with a diaphragm type vacuum gauge, hereinafter the pressure will be expressed as the pressure measured with a Pirani set vacuum gauge)" correct.

that's all

Claims (1)

[Scope of Claims] Consisting of any of the metals of Groups 4a, 5a, and 6a of the Periodic Table of the Elements, or an alloy containing these metals as a main component, and one of carbon, nitrogen, and boron. Alternatively, a surface-treated substrate structure having a surface diffusion layer in which two or more species are diffused is charged into a reactor, and the second surface diffusion layer of the substrate portion and W, Ta, Mo. Or, the distance between the filament made of graphite is 05~3
While holding it in a bowl, change the CH4/H2 ratio from 0001 to
While flowing the mixed reaction gas adjusted within the range of 0.05 into the gold reactor, the temperature of the surface diffusion layer: 500 to 120
0℃, and filament temperature 1800-2500℃
A method for vapor phase synthesis of diamond, characterized in that diamond is precipitated in the form of granules or a film on the surface diffusion layer by carrying out a vapor phase synthesis reaction.