JPH01290594A - High-speed synthesizing method for diamond utilizing co, co2 as carbon source - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a process for the rapid synthesis of granular or film diamond using co, one or a mixture of co, as carbon source.

Prior Art Conventionally, the following method has been known as a method for synthesizing diamond in a thermodynamically metastable region using electric discharge.

l) Ion beam method 5 Ion blating method in which carbon ions or hydrocarbon ions are created using electric discharge, accelerated by a potential gradient, and made to collide with the substrate surface to deposit diamond.

2) An activated vapor deposition method in which a mixed gas of hydrocarbon and hydrogen is activated by low-temperature plasma generated by glow discharge, and applied to the substrate surface to deposit diamond.

However, all of these methods have the following drawbacks.

That is, method 1) has the advantage of being able to deposit diamonds on the substrate surface at room temperature, but because accelerated ions are used, the deposited diamond may have many defects (
It is difficult to obtain products with good crystallinity, and since the ion beam density cannot be increased, the deposition rate is slow.

Although method 2) allows diamond microcrystals to be obtained on the substrate, since it uses low-temperature plasma due to glow discharge, plasma cannot be generated unless the gas pressure is low, usually 0.3 atmospheres or less. ion.

The concentration of active species such as radicals is low, at a maximum of about 10%, so the growth rate of diamond is slow (maximum several μ/hr).
There are drawbacks.

As a method for improving the drawbacks of these conventional methods, the present applicant has previously developed a method for high-speed synthesis using thermal plasma of 1700'K or higher. (Unexamined Japanese Patent Publication No. 62-15819
(No. 5 Publication) In this method, an organic compound was used as a carbon source, but the present invention was achieved by further study on the carbon source.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a method for synthesizing diamond using inexpensively available co and cot as carbon sources in the method using thermal plasma.

Structure of the Invention As a result of intensive research to achieve the above-mentioned object, the inventors of the present invention used hydrogen or a mixed gas of hydrogen and an inert gas as the plasma generating gas, and generated a thermal plasma of 1700°K or more by electric discharge. , 20 CO or CO in thermal plasma
It has been found that diamond can be easily precipitated at high speed by introducing 1 or a mixed gas thereof. Based on this knowledge, we have completed the present invention.

The gist of the present invention is to introduce one type or a mixture of Co and Cot as a carbon source into a thermal plasma of 1700" K or more generated by electric discharge in hydrogen or a mixed gas of hydrogen and an inert gas, and to produce diamonds on a substrate. This is a high-speed diamond synthesis method characterized by the precipitation of diamond.The power source used for the discharge is direct current and high frequency.

Either low frequency alternating current or microwave may be used, or they may be combined.

The plasma generating gas must contain hydrogen, which, together with the plasma temperature of 1700°K or higher, allows diamond to be synthesized at high speed. The carbon sources Co and Cot may be supplied from a plasma generation gas supply port, or may be supplied from a separately provided supply port. The plasma generating gas pressure is 10-4
It can be used in a wide range of pressures up to 5 x 10'' atmospheres. However, at low pressures the rate of diamond precipitation is slow, and at high pressures the pressure vessel is difficult to handle.

When a substrate is provided in the plasma or in the tail flame area, a diamond film can be formed on the substrate. The temperature of the board is 400~
A suitable temperature is 1700°C.

If the temperature is lower than 400'C, hydrogen may be mixed into the precipitated diamond, or defects may be introduced.
If the temperature is increased to 00°C, graphite is likely to be mixed in.

This temperature can be controlled by changing the position of the substrate, or by placing the substrate holder or substrate in an inert gas.

This can be done by cooling with a refrigerant such as hydrogen gas or water.

As the substrate, metals such as molybdenum, tungsten, and tantalum, semiconductors such as alumina, and single crystal diamond are used.

1 shows a schematic diagram of an example of a device implementing the method of the invention; FIG.

Figure 1 shows a device using high-frequency discharge, and Figure 2 shows a device using DC discharge.
2 is a high frequency oscillator, 3 is a substrate, 4 is a substrate holder, 5 is a plasma generation chamber, 6 is an exhaust device, 7 is a gas supply device, 8
．． 8', 8' regulating valves, 9 a work coil, 1o a DC plasma torch, and 11 a DC power source, the operation of which will be shown in the Examples.

Example 1 Using the apparatus shown in FIG. 1, the gas supply device 7 and the regulating valve 8.8
Gas is supplied to the plasma generation chamber 5 via ', 8'. That is, the regulating valve 8 is 0013171m1n and the argon 24! /win mixed gas from 8' to argon 101
/win, 8' to argon 21 j1! /s
After supplying a mixed gas of in and hydrogen 151,/sin and maintaining the pressure inside the plasma generation chamber 5 at 1 atm, the high frequency oscillator 2 is activated, and the vacuum tube plate input 60 is set to 1 o at -.
Discharge was performed for a minute. A 2 olφ molybdenum substrate was used as the substrate 3, and the surface temperature was maintained at 900'C by water cooling.

As a result, a diamond film with a thickness of 45 μm was obtained on the substrate 3.

Example 2゜Using the device shown in Fig. 2, the regulating valve 8.8' is connected to the gas supply device.
That is, a mixed gas of argon 301/sin and hydrogen 10L/+win is introduced from 8', and CO3j!
/win was supplied to the plasma generation chamber 5, and the pressure inside the plasma generation chamber 5 was maintained at 1 atm.Then, the DC power supply 11 was activated, and a discharge of - was performed for 10 minutes at an output of 20. The same substrate as in Example 1 was used, and the surface temperature was maintained at 1000°C.

As a result, a diamond film with a thickness of 55 μm was obtained on the substrate.

Effects of the Invention According to the method of the present invention, excellent effects can be obtained by synthesizing diamond particles and a diamond film with good crystallinity at a speed several hundred times faster than that of the conventional CVD method using inexpensive CO or CO as a carbon source. can be played.

[Brief explanation of the drawing]

The drawings show an example of an apparatus for implementing the present invention, and FIG. 1 is a schematic diagram of a synthesis apparatus when using high frequency discharge, and FIG. 2 is a schematic diagram of a synthesis apparatus when using direct current discharge. l: High frequency plasma torch, 2: High frequency oscillator, 3: Substrate, 4: Substrate holder, 5: Plasma generation chamber, 6: Exhaust device 1. ,．． 7: Gas supply device, 8.8', 8':t! U
Valve regulator, 9: Work coil, 10: DC plasma torch, 11
:DC power supply.

Claims (1)

[Claims] We introduce one type or a mixture of CO and CO_2 as a carbon source into a thermal plasma of 1700°K or more generated by electric discharge in hydrogen or a mixed gas of hydrogen and an inert gas to deposit diamond on a substrate. Characteristic high-speed synthesis method of diamond.