Computer simulation of large area diamond deposition by
dc arcjet with arc Roots rotating and operating at gas recycling mode
University of
Science and Technology Beijing, Beijing 100083, P.R. China
A computer model have been set up for simulation of the flow and temperature field, and the radial distribution of atomic hydrogen and active carbonaceous species over a large area substrate surface for a new type dc arc plasma torch with rotating arc roots and operating at gas recycling mode[1,2]. The model was based on the structural feature of the particular type of plasma torch, and on the principles of fluid dynamics, plasma physics, and plasma chemistry. Rotating arc was treated as a localized arc column with a radius close to that of the torch orifice. Whilst the non-equilibrium arc plasma was treated as in a stead state of thermodynamically localized equilibrium in the scale of the digitized cell size for numerical calculations. A gas recycling radio of 90% was assumed. In numerical calculation of plasma chemistry, the Thermal-Calc program and a powerful thermodynamic database were employed.
Numerical calculations to the computer
model were performed by using boundary conditions close to the experimental
setup for large area diamond films deposition. The results showed that the flow
and temperature field over substrate surface of F60-100mm were
smooth and uniform. Calculations were also made with plasma of the same
geometry but no arc roots rotation. It was clearly demonstrated that the design
of rotating arc roots was advantageous for high quality uniform deposition of
large area diamond films. Calculations on plasma chemistry showed that, beside
the high concentration of atomic hydrogen, the most abundant carbonaceous
species in the plasma over the substrate surface were C, C2H2,
C2, C2H, and CH, whilst CH3 and CH4
content were negligible, indicating that the C2 radical might be
responsible for diamond deposition.
Growth rate and film quality as well as
their radial uniformity for large area diamond deposition were discussed based
on the spatial distribution of atomic hydrogen and the carbonaceous species in
the plasma over the substrate surface, and were compared with experimental
observations.
The authors wish the present presentation could give a more inside understanding to the principles and performance of the plasma torch with arc roots rotation operating at gas recycling mode, and also wish to provide a computing method for prediction of large area diamond deposition.
Keywords: computer
simulation, dc arc plasma torch, rotating arc roots, gas recycling, large area
diamond deposition
References:
1.
Economical Deposition of
Large Area High Quality Diamond Film by High Power DC Arc Plasma Jet Operating
in Gas Recycling Mode, F.X. Lu, W. Z. Tang, et a.., Diamond and Related Materials, 9 (9 – 10), (2000) 1655
2.
A New Type of DC Arc Plasma
Torch for Low Cost Large Area Diamond Deposition. F.X. Lu, G.F. Zhong et
al., Diamond and related Materials, 7/6,
1998 : 737