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By introducing methane
as a sheath gas and reducing the pressure to 150
Torr in an RF induction thermal plasma CVD method,
a large volume of the thermal plasma was stabilized
and elongated into the reactor chamber where a molybdenum
substrate was placed. This made it possible to deposit
diamond films uniformly on the molybdenum substrates
as large as 100 mm in diameter at a high deposition
rate of 20-30 μm/h. This deposition
area is the largest one among those of the diamond
films ever deposited by the RF induction thermal
plasma CVD method.
When the films were
deposited on mirror-finished molybdenum substrates
by the RF thermal plasma CVD method, self-standing
diamond films of 30 mm diameter and about 30 μm
thick were obtained. The self-standing diamond-
film surface originally on the substrate side was
as smooth as the mirror-finished substrate surface.
The self-standing diamond films were brazed in a
vacuum on steel substrates so that the smooth surfaces
of the films might be the top surfaces of the brazed
materials. The adhesive strength of the brazed diamond
film the steel substrate was rather high, and the
as-brazed diamond film with a smooth surface had
a low friction coefficient of 0.1 against steel
without oil lubrication in an ambient atmosphere.
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