Diagnosis of Methane Plasma Generated in an Atmospheric Pressure DBD Micro-Jet by Optical Emission Spectroscopy

Diagnosis of methane plasma, generated in an atmospheric pressure dielectric barrier discharge (DBD) micro-plasma jet with a quartz tube as dielectric material by a 25kHz sinusoidal ac power source, is conducted by optical emission spectroscopy (OES). The reactive radicals in methane plasma such as CH, C₂, and H_α are detected in-situ by OES. The possible dissociation mechanism of methane in diluted Ar plasma is deduced from spectra. In addition, the density of CH radical, which is considered as one of the precursors in diamond-like (DLC) film formation, affected by the parameters of input voltage and the feed gas flow rate, is emphasized. With the Boltzmann plots, four Ar atomic spectral lines (located at 675.28nm, 687.13nm, 738.40nm and 794.82nm, respectively) are chosen to calculate the electron temperature, and the dependence of electron temperature on discharge
parameters is also investigated.