| Radio-frequency atmospheric pressure glow discharge (RF APGD) cold plasmas have widespread applications in different fields, including plasma-aided etching, deposition, material surface cleaning and ashing, sterilization and biological warfare agents due to the removal of the vacuum system. At the present time, it is a challenging task to obtain Ar/O2, or Ar/N2 RF APGD in the a mode using the plasma generators with bare metallic electrodes. In this paper, a homogeneous and stable Ar/O2 and Ar/N2 glow discharge in a mode is generated at atmospheric-pressure in a parallel bare metal plate reactor with a radio frequency (13.56 MHz) power supply by introducing a dielectric strip in the inlet of the gas flow. The discharge characteristics with oxygen-argon and nitrogen-argon mixtures are investigated by the electrical measurements and optical diagnostics.In the study of Ar/O2 RF APGD, two different breakdown mechanisms were found to be responsible for argon plasma ignition at various electrode gaps. Stable and uniform RF APGD plasma in a mode was observed after argon breakdown. Oxygen can be added into argon by adjusting matching network and the allowable oxygen-to-argon ratio reached 0.9 vol%. With increasing oxygen-to-argon ratio, the Ar/O2 discharge plasma became unstable. Depending on the input power, normal and abnormal glow regimes were observed in a mode. The discharge started as a normal glow and then became an abnormal glow as the input power was increased. It was found that the power density of the plasma operated in an abnormal glow increased with the increase of oxygen content. And the voltage-current characteristic, representing the whole discharge process from the ignition with pure argon to a stable and uniform plasma in the y mode is analyzed. Meanwhile, the a and y mode andα-γcoexisting mode were observed in the whole process. The curves of voltage and current versus input power were recorded in rms values in the glow discharge region at 0.0%,0.3% and 0.6 vol%. With increasing input power, both RF current and voltage increased. The electron density and electron temperature were estimated on the basis of the electrical experiment data using the equivalent circuit model and the reduced energy balance equation. The results showed that the electron density of the Ar/O2 discharge in the abnormal glow regime was approximately 1011 cm-3 and increased with input power, however it decreased while increasing the fraction of oxygen, as oxygen is an electronegative gas and the attachment processes are loss channels of electrons. The electron temperature of Ar/02 was approximately 1.4 eV and changed slightly as input power increased. Furthermore, the gas temperature has been determined by the fitting of experimental and simulated spectra of OH band with LIFBASE software and using the Boltzmann plot method, which is in good coincidence. With increasing input power, the gas temperature of Ar/02 increased at oxygen-to-argon ratios of 0.0,0.3 and 0.6 vol%. When mensurating the oxygen atom generated in Ar/02 plasma by optical actinometry, it was found that an optimal value of oxygen density (0.35 vol%) existed in the production of oxygen radicals. Moreover, the carbon black on the slide glass was completely removed by an oxidation in 3.5 min. Base on the results, it is expected that the Ar/O2 plasma can be effectively utilized to material treatment due to enough chemically active species.In the study of Ar/N2 RF APGD, a stable and uniform plasma in a mode was also obtained and the allowable nitrogen-to-argon ratio reaches more than 1.0 vol%. The color of the discharge plasma changed from white to purple when the nitrogen was added into the argon plasma. In addition, Emission spectrum of the N2 (C3Πu→B3Πg) was observed by measuring the spectrum of 300-900 nm in mixture gas. And the vibrational temperature of N2 was calculated by the measurements of the sequences of vibrational bands of N2 second positive system. The vibrational temperature was approximately 181 IK at nitrogen-to-argon ratio of 0.8 vol% and an input power of 150W. We analyzed qualitatively the optical emission spectrum of the N2 (C3Πu→B3Πg). It was found that the peaks at 337,380 and 405nm increased with the increase of input power.
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