Metrology of non-thermal capacitively coupled N2–Ar mixture plasma

The effect of argon gas mixing on electron temperature, active species concentration and degree of nitrogen dissociation in a 13.56 MHz radio frequency (RF) sustained low pressure Ar–N2 mixture plasma is investigated by using optical emission spectroscopy (OES). The electron temperature is determined from Ar–I emission line intensities by using the modified Boltzmann plot method. It is observed that it decreases with increase in Ar percentage and filling gas pressure in the mixture whereas it increases with the increase in RF power and gas flow rate. The concentration of active species N2(C3Πu) and N2+(B2Σu+) is monitored in terms of the emission intensities of (0–0) band-head of the second positive system (337.1 nm) and first negative system (391.4 nm) of nitrogen respectively. It is found that the concentration of N2(C3Πu) active species increases with argon mixing up to 60%, while the concentration of N2+(B2Σu+) decreases. The N2 dissociation is found to be enhanced appreciably by argon mixing above 60%. It also increases with RF power and show a peak value at 0.5 mbar whereas dissociation fraction is found to be decreased with increasing flow rate.