Application of optical emission spectroscopy for the determination of optimal CVD diamond growth parameters in abnormal glow discharge plasma

• Ar addition into the H2/CH4 mixture leads to increase of gas temperature in plasma.
• The bulk of atomic hydrogen is generated in the center of plasma column.
• The increase of discharge current increases the growth rate of diamond films.
• The optimal working pressure in AC abnormal glow discharge CVD reactor is 50–70 Torr.
• Maximum diamond growth rate is attained in argon-free H2/CH4 gas mixture.

Optical emission spectroscopy (OES) has been used to investigate the generation of active species in H2/CH4 and H2/Ar/CH4 AC abnormal glow discharge plasmas during chemical vapor deposition of polycrystalline diamond. The vertical, spatially resolved measurements illustrate that the concentration of atomic hydrogen decreases rapidly with distance from the center of the plasma column. The addition of argon to the gas mixture leads to a drop in the electronic temperature and an increase in gas temperature but causes decreased atomic hydrogen concentration and diamond film growth rate due to the reduction in molecular hydrogen concentration. The emissions were monitored as functions of such process parameters as discharge current, gas flow rate, operating pressure and argon content. Obtained relations identified by OES were found to be in good agreement with experimental diamond growth measurements.