Characterization of RF-Driven Slot Microplasmas using Optical Emission Spectroscopy

Summary form only given. We present measurements of optical emission spectra in the UV/VUV and visible regions from hollow-slot microplasmas operating at 13.56 and 60 MHz at atmospheric pressure. Spectra are presented for discharges that use helium gas flowing between the electrodes into open air, as well as helium with small admixtures of impurities (nitrogen and hydrogen). We observe that the microplasmas sustained at the higher frequency of 60 MHz operate with greater stability and can be sustained at relatively lower power as compared to the lower 13.56 MHz plasmas. Optical emission spectra from both atomic and molecular species are used to characterize various plasma properties including gas temperature, vibrational temperature, and relative rates of slow electron-metastable interactions. Optical emission spectra in the UV/VUV region indicate the role of secondary electrons emitted from electrode surfaces are markedly different for the two different excitation frequencies