An indirect method for measuring the electron density of radio frequency atmospheric pressure plasma jets(RF-APPJ) based on the discharge voltage and current waveforms is presented.An equivalent circuit of the plasma discharge is assumed by taking into account the electrode capacitance,serial resistance and inductance of the bulk plasma,as well as the sheath impedance.Based on the circuit model,the electron density can be obtained according to Ohm's law.By using this method,the effects of the electrode shape and discharge gap on the electron density are discussed.
Based on the one-dimensional fluid model, the characteristics of homogeneous dischargeswith hydrogen diluted silane and argon at atmospheric pressure are numerically investigated.The primary processes of excitation and ionization and sixteen reactions of radicals withradicals in silane/hydrogen/argon discharges are considered. The effects of hydrogen dilution onthe densities of species (e, H, SiH_3^+, SiH_3^-, SiH_3,) are analyzed. The simulation results show thatthe highest densities of e, SiH_3^+, H, SiH_3^-, SiH_3 correspond to the optimal dilution concentration ofH_2. The deposition rate of μc-Si:H film depends on the SiH_3 concentration, and atomic hydrogenin the plasma is found to play an important role in the crystallization fraction of the depositedfilms. This model explains the effects of H_2 dilution on the deposition rate and crystallized fractionof μc-Si:H film growth.
The characteristics of homogeneous discharges in mixed gases of hydrogen diluted silane and argon at atmospheric pressure are investigated numerically based on a one-dimensional fluid model.This model takes into account the primary processes excitation and ionization,sixteen reactions of radicals with radicals in silane/hydrogen/argon discharges and therefore,can adequately represent the discharge plasma.We analyze the effects of very high frequency(VHF) on the densities of species(e,H,SiH3,SiH+3 and SiH2) in such discharges using the model.The simulation results show that the densities of SiH3,SiH+3,H,and SiH2 increase with VHF when the VHF ranges from 30 MHz to 150 MHz.It is found that the deposition rate of μc-Si:H film depends on the concentration of SiH3,SiH+3,SiH2,and H in the plasma.The effects of VHF on the deposition rate and the amount of crystallized fraction for μc-Si:H film growth is also discussed in this paper.
An atmospheric pressure nonequilibrium argon/oxygen plasma jet assisted by thepreionization of syringe needle electrode discharge is reported. With the syringe needle plasmaas its pre-ionization source, the hybrid barrier-jet was shown to generate uniform discharge witha lower breakdown voltage and a relatively low gas temperature varying from 390 K to 440 K,even when the vol.% oxygen in argon was up to 6%. Utilizing the actinometry method, theconcentration of atomic oxygen was estimated to be about in an orders of magnitude of 10^(17) cm^(-3).The argon/oxygen plasma jet was then employed to clean out heat transfer oil, with a maximumcleaning rate of 0.1 mm/s achieved.
