Emission spectroscopy diagnostics of a d.c. plasma jet diamond reactor

We performed emission spectroscopy on a d.c. plasma jet (Ar, H2, CH4) chemical vapor deposition reactor. We used a spectrometer with a large spectral range (150–800 nm), a spectral resolution of 0.07 nm and a spatial resolution better than 1 mm. We were able to derive information concerning the gaseous species existing in the plasma (CH, C2, H, Ar, C) as well as their evolution with torch parameters. Studies of the CH (B2∑ → X2Π) rotational band and the C2 (A3Πg → X3 Πu) rovibrational bands allowed temperature measurements using both spectra simulation and the Boltzmann method. We thus obtained rotational temperature maps of the jet and information on the vibrational temperature. These data will be useful for modelling the plasma jet. Emission spectroscopy also provides information concerning the electron densities in the plasma. Indeed, significantly Stark broadened H Balmer lines were observed.