Discharge Operation Mode In Radio Frequency Atmospheric Pressure Glow Discharges

Low temperature plasma has wide application scopes in industries including surfacemodification, thin film deposition, environment purification and other fields, recently.Atmospheric pressure glow discharges are considered to be suitable for on-line employment inindustries because the vacuum system is not required, which meets the characteristics of low costand high efficiency, as required in the modern industry. Comparing with the dielectric barrierdischarge, the radio-frequency atmospheric pressure glow discharge generates the plasma withlow breakdown voltage and high plasma density, also high gas temperature and powerconsumption. The discharge evolves from stable and uniform discharge in mode to unstabledischarge in mode with increasing the discharge intensity. Such much attention is paid on theinvestigation of discharge characteristics manipulation and discharge mechanism.The dependence of discharge operation mode on excitation frequency was studied hereexperimentally. The current-voltage characteristics and optical emission intensity at706nm in mode of radio-frequency (RF) atmospheric pressure glow discharges (APGD) of helium atexcitation frequencies of6.78,13.56, and20.34MHz were studied to explain the discharge modetransition and plasma reactivity on excitation frequency. Furtherly, the discharge parameter rangeof stable and uniform mode was characterized in the excitation frequency rang2.5to25MHz,from which the mechanism of mode transition was discussed. It is suggested that the stableoperation regime of mode can be expanded by applying higher excitation frequencies.The effects of excitation frequency on discharge characteristics were studied by a one- dimensional self-consistent fluid numerical model. The spatial profiles of electron, ion, metastable,electric field and mean electron energy are presented. The dependence of current voltagecharacteristics, electron density and sheath thickness on excitation frequency was also provided toillustrate the underpin physics and mechanism of excitation frequency on radio frequencyatmospheric pressure glow discharges.