| Budget Amount *help |
¥1,800,000 (Direct Cost: ¥1,800,000)
Fiscal Year 1991: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1990: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Research Abstract |
Two kinds of experiments have been performed to reveal the fundamental process of diamond formation from the vapor phase and also to know the physical meaning of growing temperature such as 800-900C.
For the first experiment, carbon atoms prepared by removing carbon clusters are used as the source gas for diamond deposition in a hydrogen ambient of 10 Torr. In this system, diamond particles are found by high resolution TEM. If carbon vapor containing carbon clusters is used as the source gas, amorphous carbon films grow even at the elevated substrate temperature of about 850C.
For the second experiment, the hot-filament CVD method is used with the mixture gas of methane and hydrogen at the lower gas pressure of 0.01-1 Torr. The growth rate of diamond is remarkably reduced as the ambient gas pressure is lowered to about 0.01Torr. Below this pressure, diamond growth cannot be found by TEM observation.
Assuming the gas temperature of 2000C around the hotfilament, the concentration of active species such as hydrog en molecules, H, C, CH etc. is calculated. The mean free path of H and C at the gas temperature of about 2000C is also calculated. From these results, it is found that atomic carbon and atomic hydrogen arrive to the substrate surface without collision to the other species.
Considering these two experiments, it is shown that diamond can be grown preparing atomic carbon and hydrogen. The heating of growing surfaces is not required for the crystallization of diamond but for the dissociation of hydrogen from the surface. The remained important task is to perform the CVD process using the reaction of hydrogen extraction by atomic hydrogen. This will realize the low temperature process of diamond formation from the vapor phase.
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