JPH01203295A - Method for synthesizing diamond by vapor phase method - Google Patents

Abstract

PURPOSE:To easily deposit homogeneous and thick-film diamond having excellent wear resistance, etc., by releasing raw materials contg. carbon toward a base material for depositing the diamond and burning the raw materials in a manner as to form an incomplete combustion region. CONSTITUTION:The base material 5 for depositing the diamond and a base material supporting base 6 are disposed to the central part of an annular burner 1 disposed with burner ejection ports 4 to a circular shape. A tungsten filament 7 which is an auxiliary heating element is then fixed to the position of about 7mm above the ejection ports 4 and about 3mm below the plane of the base material 5. The gaseous raw material mixture contg. H2, carbon such as propane is introduced from a gas introducing port 2 of the burner 1 into the burner and is released from the ejection ports 4 into the atmosphere to form combustion flames and to form the incomplete combustion region. While the base material is maintained at about 2,100 deg.C by electrically heating the filament 7, the supporting base 6 is rotated at about 6rpm and the base material is pulled up at about 15mum speed per hour to make the synthesis operation, by which the diamond of about 82mum thickness is continuously deposited in the vapor phase manner on the base material 5.

Description

[Detailed description of the invention] <Industrial application field> The present invention has excellent properties such as wear resistance, corrosion resistance, high thermal conductivity, and wide-area optical transparency, and can be used as an abrasive material, an abrasive material, and a cemented carbide tool. The present invention relates to a method for vapor phase synthesis of film-like, flaky-like, plate-like, and rod-like diamonds that are useful as materials, members for optical materials, and the like.

<Prior Art> Conventional methods for synthesizing diamond include a synthesis method using an iron or nickel catalyst under ultra-high pressure and high temperature conditions, and a direct conversion method of graphite using an explosive method.

In recent years, as a low-pressure CVD method, a mixed gas of hydrogen and a hydrocarbon or an organic compound containing nitrogen, oxygen, etc. is heated through a hot filament.
Methods have been developed for synthesizing diamond in an excited state using microwave plasma, high-frequency plasma, DC discharge plasma, DC arc discharge, and the like.

The film, flake, plate, or rod-shaped diamonds according to the present invention are produced by laser cutting from large diamond crystals grown over a long period of time under very special conditions using ultra-high pressure. .

Regarding film-like materials, research is currently being carried out using low-pressure CVD methods.

<Problems to be solved by the invention> The ultra-high pressure method described above requires special equipment, and the production of membrane-, flake-, plate-, and rod-shaped diamonds requires first synthesizing large diamonds, and then They are manufactured by cutting diamonds with a laser, and cannot necessarily be said to meet the practical demands of easy, low-cost, and quick manufacturing. Further, in the conventional CVD method, a special device is required to excite the raw material gas so that diamond can be synthesized. Furthermore, no matter which excitation source is used, it is difficult to increase the area of diamond precipitation, and it has been impossible to produce thick plate-shaped or rod-shaped diamonds. The present inventors have conducted research to develop a gas-phase synthesis method that can produce film-like, plate-like, and rod-like diamonds with a large area using simple means compared to conventional methods. The present invention was completed after confirming that the object could be achieved by burning a compound from the periphery of the substrate for diamond precipitation so that the combustion flame directed toward the center to form an incomplete combustion region.

<One Means for Solving the Problem> The present inventors have conducted various studies regarding the low-pressure CVD method, particularly regarding excitation means, and have found that thermal filament is a thermal plasma, microwave is a microwave plasma 1, and direct current arc discharge is a thermal plasma. It was concluded that the plasma state of all forms of diamond synthesis, including arc discharge plasma, plays a major role in diamond synthesis, and since the combustion flame caused by combustion is also in a plasma state, using this combustion flame is easier than using conventional methods. As a result of intensive research, we have developed the present invention, thinking that by directing the combustion flame toward the base material for diamond precipitation and generating it from the surrounding area, we can make the H of the generated diamond equal and homogeneous. completed.

That is, the present invention emits a carbon-containing raw material compound for diamond precipitation toward the center from the periphery of the annular shape, burns it so as to have an incomplete combustion region, and burns the non-oxidized material in or near the incomplete combustion region. The present invention relates to a vapor phase diamond synthesis method characterized in that diamond is continuously deposited on the substrate by placing a substrate for diamond precipitation in a neutral atmosphere and maintaining the temperature of the substrate at the diamond precipitation temperature.

Note that the diamond synthesized by the method of the present invention contains diamond-like carbon.

First, the raw material gas for diamond synthesis will be explained.

Various compounds shown below can be used as carbon sources.

a) Hydrogen-containing compound Eternal hydrocarbons: methane, ethane, propane, butane, etc.

Unsaturated hydrocarbons: ethylene, propylene, butylene, acetylene, arylene, etc.

Aromatic hydrocarbons: benzene, toluene, xylene, cyclohexane, etc.

CHO compound: alcohols such as methanol, ethanol, propatool, butanol, and ether group-containing compounds such as dimethyl ether and diethyl ether.

Those containing ketone groups; acetone, methyl ethyl ketone,
Diethyl ketone, 2,4-bentanedione, acetophenone, l'-butylonaphthone.

Ester series: methyl acetate, ethyl acetate, isoamyl acetate.

Those containing ketene groups: dimethylketene, phenylketene.

Containing acetyl groups: acetic acid, acetic anhydride, acetophenone, biacetyl.

Those containing aldehyde groups: formaldehyde, acetaldehyde, propionaldehyde.

Diketene, diazomethane containing a methylene group.

Those containing a methyl group: t-butyl peroxide, methyl hydroperoxide, peracetic acid.

b) Nitrogen-containing compounds primary amines: methylamine, ethylamine, dimethylamine, trimethylamine, isopropylamine.

Those containing nitrile groups: niacetonitrile, benzonitrile, acrylonitrile, pivalonitrile.

Those containing amide groups: hexane amide, acetamide.

Nitro group compounds: nitroethane, nitromethane, nitrosobenzene, nitropropane.

C) Oxygen-containing compounds - carbon oxide, carbon dioxide gas.

The above-mentioned compounds can be used alone or in combination of two or more.

These carbon source compounds are mixed with hydrogen and, if necessary, oxygen, and then burned in an oxygen-containing or non-oxygen-containing atmosphere.

Furthermore, it is also possible to use solid carbon, graphite, etc. as a carbon source through reactions such as vaporization, combustion, and hydrogenation in a combustion flame of a mixed gas of the compound, hydrogen, and oxygen.

In the present invention, the raw material gas for diamond synthesis is combusted so that an incomplete combustion region exists to form a combustion flame, and Nagai's non-oxidizing diamond is precipitated in the incomplete combustion region or near the flame. In the excited region,
It is necessary to always have a diamond precipitation growth surface.

Further, a specific example of adding oxygen to the raw material gas for diamond synthesis to generate an incomplete combustion region excited to a diamond precipitation state in an oxygen-free atmosphere or an oxygen-containing atmosphere is as follows: For example, the former case can be exemplified by combustion in an atmosphere such as argon, and the latter case can be exemplified by combustion in open air.

The method of the present invention is characterized in that the combustion flame is generated from the periphery of the base material toward the base material.

FIG. 1 shows an example of an apparatus for carrying out the method of the present invention, and FIG. 2 is a cross section taken along the line A-A in FIG.

In the drawings, reference numeral 1 denotes an annular burner, which has a raw material supply pipe 2 for diamond precipitation combustion, an annular burner main body 3, and a burner outlet 4, and the supply pipe 2 and the burner outlet are connected.

Further, 5 is a base material, and a base material support 6 has a cooling means such as water cooling.
installed on. 7 is a tungsten wire filament.

8 shown in FIG. 2 is a combustion flame. A raw material is supplied from a raw material supply pipe 2 for precipitation combustion, and a combustion flame is generated from a burner jet port. The combustion flame has an incomplete combustion region 9 which should be called an inner flame,
It is composed of an outer flame 10.

The tungsten wire filament exemplified in No. 7 is an auxiliary excitation means when the combustion flame alone is insufficient to excite the diamond-forming state.

FIG. 3 is a sectional view of another example of an apparatus for carrying out the method of the present invention, in which the base material 5 of the apparatus of FIG. Base material rod 1 arranged to be movable up and down and rotatable around an axial center
5 and the tungsten wire filament 7 to the base rod 1.
A tungsten wire filament 17.27 is placed between the wires 5 and 5. Note that the tungsten wire filament is not limited to the one shown in the drawings, and may be provided on a part or the entire surface of the base rod as appropriate.

As the base material for diamond precipitation shown at 5.15 in the figure, those normally used in low pressure CVD methods can be used.

That is, diamond plates, granules, Si wafers, SiC
In addition to the granular sintered body plate, a material made of W, WC, Mo, cemented carbide, etc. can be used by fixing it to a base material support.

The areas where diamonds precipitate are the oxygen-deficient areas in the combustion flame. In the oxygen-excessive region, even if diamond is formed under high heat, the excess oxygen turns into co, co, and disappears. That is, the diamond precipitation region is oxygen deficient and relatively low temperature. In this region, it is necessary to excite the raw material gas to conditions that produce hydrocarbon radicals and carbon radicals (active species). In the method of the present invention, the temperature of the flame is preferably 300-3000'C and the temperature of the substrate for diamond precipitation is preferably 300-1400'C.

If the excitation is insufficient in this state, a heating element using single current heating, high frequency induction heating, a heating method using laser light, infrared heating, heating using arc discharge, etc. are used as an auxiliary heating source.

Specifically, the heating region temperature may be maintained at 800°C or higher, preferably 1000°C or higher, and the substrate temperature may be maintained at 300°C or higher and 1400°C or lower.

The pressure at which the flame is formed can be selected from 0.001 atm to 1000 atm, preferably from 0.01 atm to 50 atm. In particular, synthesis at normal pressure (1 atm) can be carried out in the open to the atmosphere, and is of great practical value.

Note that if the base material support is made rotatable, if the diamond is not deposited uniformly on the base material, it can be easily made uniform by rotating it. Furthermore, by making the base material support vertically movable, it is easy to always adjust the base material to the optimal diamond deposition position of the combustion flame. Thus, for example, the substrate can also be moved in the vertical direction depending on the formation of diamonds.

Furthermore, the auxiliary heating element is not necessarily placed above the base material, but can also be placed below the base material.

Furthermore, compared to other vapor phase CVD methods, the hydraulic method can easily keep the diamond precipitation region stable for a long period of time. In addition, the diamond growth rate is 1 to 2 gm/hr or more, and the degree of contamination of the grown diamond from the container etc. is lower than in diamond synthesis methods using microwave excitation, high frequency excitation, DC plasma excitation, etc.

<Function> The carbon-containing raw material compound is decomposed and dissociated by reaction with oxygen in a combustion flame, and the radicalized active species are converted into C, C2, etc.
, CIl, CH, , CI'13, etc. are presumed to form a diamond phase and precipitate.

Furthermore, hydrogen atoms and oxygen atoms are also formed and are thought to be involved in the diamond precipitation reaction.

<Effects of the invention> It is extremely easy to produce diamonds that are homogeneous and have a large thickness.
In addition, it can be manufactured using the CVD method without using complicated equipment.
It has great practical value.

<Example) Example 1 A 7111 m square Si wafer substrate made of SuS is placed 10 mm above the nozzle from the center of the annular burner shown in Fig. 1, which has 10 pieces arranged in a circle on the same nozzle hole with a diameter of 4 mm. It is installed on a rotating support stand and used as an auxiliary heating element with a diameter of 0. :I
A filament of a tungsten wire of 113φ was fixed at a position 7 mm above the nozzle and 3II11 below the wafer surface. 822500 G (:/
min, propane 37.5 CG/min (propane/hydrogen ratio 2
．． A mixed gas of 5Voβ%) is sent through a nozzle to generate a combustion flame in the atmosphere, and then a tungsten wire is heated with electricity 21
The temperature was maintained at 00°C.

Rotate the substrate holder at 6 rpm and j5 g per hour.
It was pulled up to the top at a speed of m.

Synthesis was carried out in this state for 8 hours.

As a result, a highly crystalline layer with a thickness of about 82 gm was obtained on the Si wafer. Crystal grains of several gm could be observed under the surface using an optical microscope. Also, Raman spectroscopy spectrum 13
A sharp peak due to diamond at 33 cm-' and 155
A very broad peak due to i-carbon was observed near 0 cm-'.

Example 2 Using exactly the same equipment as in Example 1, 112250
Continuous synthesis was carried out for 10 hours using the same conditions except for introducing 0 cc/min of ethanol and 50 cc/min of ethanol (ethanol/hydrogen ratio 2 voj!$).

As a result, Example 1 with good crystallinity with a thickness of approximately 141 JLm
A thick film with a similar surface morphology was confirmed by microscopic observation.

A similar spectrum was also obtained by Raman spectroscopy.

[Brief explanation of the drawing]

Fig. 1 is an example of an apparatus for carrying out the present invention, Fig. 2 is a sectional view taken along the line A-A in Fig. 1, and Fig. 3 is a sectional view of another example of the apparatus for carrying out the invention. It is. In the figure, l is an annular burner, 2 is a raw material supply pipe for diamond precipitation combustion, 3 is an annular burner main body, 4 is a burner outlet, 5.15 is a base material, 6 is a base material support, 7.17
．． 27 is a tungsten wire filament, 8 is a combustion flame, 9
is internal inflammation, and 1o is external inflammation. Figure 1 Figure 2 Figure 3

Claims (1)

[Scope of Claims] A raw material compound for diamond precipitation containing carbon is combusted so as to be emitted from the periphery of the annular shape toward the center so as to have an incomplete combustion region, and in or near the incomplete combustion region. A vapor phase method diamond characterized in that diamond is continuously deposited on the base material by installing a base material for diamond precipitation in a non-oxidizing atmosphere and maintaining the base material temperature at the diamond precipitation temperature. synthesis method.