New technology for high rate synthesis of PC-diamond coatings in air with photon plasmatron

Abstract

In this paper the development of a new plasma-CVD method for synthesis of PC-diamond coatings in air is presented. The method does not require any vacuum or reaction chamber and is based on plasma-CVD processes taking place in a photon-initiated stationary plasma in the open-air atmosphere maintained in the electromagnetic optical field of a high-power cw-CO2 laser radiation. To use this plasma as an activation source for the CVD process with different gas precursors, a special photon plasmatron operating in air has been designed and constructed. The high temperature in the photon-initiated plasma (15000–20000 K) as well as the high pressure (≥1 atm) of the precursor gases, are prerequisites for a high-rate synthesis of PC-diamond coatings. For this purpose, different gases like Ar, CO2, CH4, H2, N2 and their mixtures have been used. The properties of the deposited coatings in dependence on the experimental conditions have been investigated with SEM, EDX, AUGER and RAMAN techniques. With this new technology uniform and continuous PC-diamond films on molybdenum, Si and cemented carbides have been locally deposited onto an area of approximately 2 cm2 with a deposition rate of up to 2 μm/min for the present. With optimisation of the process, a further significant increase in deposition rate can be expected.