Spectroscopic study on rotational and vibrational temperature of N2 and N2+ in dual-frequency capacitively coupled plasma

By using optical emission spectroscopy, the vibrational and rotational temperatures of N2 and N2+ in capacitively coupled plasma (CCP) discharges driven by dual-frequency 41MHz and 2MHz are investigated. The vibrational and rotational temperatures are measured based on the N2+ first negative system and N2 second positive system overlapped molecular emission optical spectrum, using the method of comparing the measured and calculated spectra with a least-square procedure. The influence of the rotational and vibrational temperatures with input power of the high frequency (HF) and low frequency (LF) as well as the gas pressure is discussed. It is found that the vibrational or rotational temperatures of N2 and N2+ are decoupled in dual-frequency CCP discharge. The influence of the LF power on N2+ rotational and vibrational temperature is much more than that of N2, while the influence of HF power is just opposite to the case of LF power. The reason for this is thought to be the variation of electron temperature...