JPH038797A - Method for synthesizing diamond in vapor phase under pressure - Google Patents

Abstract

PURPOSE:To grow a high-quality diamond at ordinary pressure in vapor phase by heating a substance having diamond type structure in a vapor atmosphere of an organic compound mainly containing a hydrocarbon. CONSTITUTION:A diamond or substance (e.g. silicon or silicon carbide) having diamond type structure which becomes a ground of diamond crystal is used as a substrate. The inside of a vessel is packed with a ordinary pressure or pressure vapor of organic compound mainly containing hydrocarbon. The above- mentioned substrate in the vessel is heated to grow the diamond crystal in vapor phase on the surface.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a method for synthesizing diamond by vapor phase growth of an organic compound in pressurized vapor.

"Conventional Technology" Conventional methods for synthesizing diamonds have been researched in various countries for a long time, and the following methods have already been discovered.

A method of synthesizing graphite from graphite under high temperature and pressure.

A method that uses a carbon ion beam using plasma.

C. A chemical transport method that creates crystals on a substrate using activated hydrocarbons produced by heating graphite in hydrogen gas.

Two, i%! A gas phase synthesis method in which a mixed gas of hydrocarbon and hydrogen gas is activated with a filament under pressure and radiated onto a substrate to crystallize it.

``Four problems to be solved by the invention'' Among the conventional methods, method A can be synthesized in the shortest time, and industrial production has actually been carried out using this method. There is. Other methods have the advantage of being able to produce crystals with fewer lattice defects, although they are time consuming. Therefore, by using any of these methods, it is possible to synthesize diamonds that suit the purpose. However, if we consider these methods from the viewpoint of productivity, methods (a) and (i) require a huge capital investment and produce high-quality crystals, while methods (c) have difficulties in supplying raw materials. In addition, method 2 also requires equipment for reducing the pressure, and furthermore, the reduced pressure reduces the gas concentration, resulting in poor efficiency.

Based on the above technical methods and problems, the present inventor has investigated a method for vapor phase synthesis of diamond, which is an industrially important resource, under pressurized conditions including normal pressure, and hereby discloses the method. It is.

"Means for Solving the Problems" First, in carrying out the present invention, an apparatus shown in FIG. 1 is manufactured. This device is equipped with the basic structure necessary for the synthesis method of the present invention, and the following four items are the main elements.

(1) A fine 1x exhaust port is provided at the top of the container to maintain the internal gas phase at normal pressure or pressurized state. In addition, a feed port for raw materials is provided as necessary.

(2) Use a heater with enough output to keep the two substrates in a red-hot state, and supply only the amount necessary for thermal decomposition of the raw organic compound and crystallization of carbon. In addition, if the organic compound as a raw material is not heated separately, it also serves as heating.

(3) Substrate: This serves as a base for diamond crystals, and diamond is suitably used, but materials such as silicon and silicon carbide having a diamond-shaped structure may also be used.

(4) Raw material: An organic compound mainly composed of hydrocarbons, which is heated to fill the container with steam at normal pressure or pressurized state.

Pressurized gas phase synthesis of diamond is performed using an apparatus having the above four items as a basic structure, with the addition of an internal container to prevent convection of activated gas and a pressurizer to increase the pressure inside the container.

"Operation" When using an apparatus based on the above-described structure, diamond is synthesized by the following operation.

First, when the heater (2) starts heating, the heat is transferred to the air inside the container, and the heated air is exhausted to the outside from the exhaust port due to thermal expansion. Exhausting air alone is not enough, but when the raw material is heated and turned into steam, the air is pushed out and further exhausted, filling the container with the vapor of the raw organic compound. At this time, if the exhaust port of the container is made small enough, the pressure inside the container will be maintained at above normal pressure by the vapor pressure and the gas generated during the reaction, and the atmosphere will not enter the container again. The pressure can also be increased by using a pressurizer, using the vapor pressure of the organic compound as a raw material by heating. There is no need to use a vacuum device or the like, and the efficiency can be expected to improve due to the increased gas density due to pressurization. In addition, by using an internal container, wasteful mixing of activated gas and steam due to convection is suppressed, and by heating near the surface of the raw material using residual heat from the heater, convection of the raw material itself is prevented and steam pressure is efficiently increased. I can do it.

The vapor of the raw organic compound is gradually consumed by the thermal decomposition reaction, but the consumed amount is continuously supplied from the surface of the raw material, while the gas produced during the reaction is heated to the h of the container.
It is discharged from the exhaust port that is connected to the atmosphere. The organic compound that has turned into vapor comes into contact with a sufficiently heated base substrate, and is decomposed by heat on the surface to generate activated gas.
Vapor phase growth of diamond crystals is carried out. In order to prevent the formation of graphite, it is necessary to provide the heat necessary for the reaction only through heat transfer from the base substrate, and in addition, this base substrate contains a material with a diamond structure to promote carbon crystallization. Use.

The most suitable material for the base substrate is diamond, but silicon with a diamond-shaped structure can also be used, and it is also possible to use not only a single substance but also a compound such as silicon carbide, but the base substrate is red-hot. Therefore, it is necessary that the substance has a melting point higher than that.

"Example" Using the apparatus shown in FIG. 1, the container (1) has a 0.
100mm in diameter and 135m in height with a 6mm diameter exhaust port.
mJ! An iron cylindrical container with a diameter of 0.2 mm, (2) a 6.5 mm x 75 mm x 1.4 mm x 32 W alumina ceramic heater as a heater, (3) a base substrate with a mirror finish on the surface, and a 6.6 with a slightly rough surface.
Silicon chips, mmX6mmX0.2mm, (4)
As a result of a 50-hour trial using an iron cylindrical container with an outer diameter of 9 mm, a height of 57 mm, and a thickness of 1 mm as an inner container for ethanol with a concentration of 80% (10) as a raw material for We have succeeded in obtaining a thin film of diamond with a thickness of approximately 100 um.

This diamond has a strong spectroscopic effect, and when exposed to light, it emits a bluish reflected light, and when deposited on a slightly rough substrate, the reflected light can be seen by changing the incident and reflection angles. It was observed that the color changed to green, blue, purple, red, orange, and yellow.

"Effects of the Invention" The effect that high-quality diamond containing almost no internal impurities or lattice defects can be synthesized by the pressurized vapor phase synthesis method of diamond of the present invention, and the use of the diamond synthesis method of the present invention This makes it possible to synthesize at normal pressure, eliminating the need for high-pressure generators, vacuum generators, etc., and solid pressure-resistant containers, which are essential to conventional methods, and eliminates unnecessary costs associated with this. The effect is that diamond can be synthesized more economically by reducing the amount of carbon used, and gas phase synthesis under pressure increases the gas concentration, making it more efficient than synthesis under reduced pressure. has the expected effect.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of the synthesis apparatus. l, container, 2. Heater, 3. Substrate, 4. Raw materials, 5. Power supply, 6. Insulated plug, 7. Pressurizer 8, exhaust port, 9. Set screw, 10. inner container.

Claims (1)

[Claims] 1. Synthesis of diamond by heating a substance with a diamond-shaped structure in normal pressure or pressurized steam of an organic compound mainly composed of hydrocarbons, and growing diamond crystals on its surface in a vapor phase. how to. 2. An apparatus having a basic structure for synthesizing diamond using the synthesis method according to claim 1.