Radio-frequency-driven near atmospheric pressure microplasma in a hollow slot electrode configuration

Abstract

We report hollow electrode geometries that support near atmospheric (89 kPa) microdischarges in Ar and Ar–air mixtures when excited at 13.56 MHz with rf voltages of 50–230 V. The slot dimensions are 200 μm wide by 400–600 μm deep and 3–35 cm in length. Optical emission along the slot length is uniform in intensity at applied rf power levels up to 10 W/cm of slot length under the experimental conditions described herein. When metal electrodes are employed, we can draw 0.18 A/cm of self-bias dc current into the rf-driven plasma. Measurements of the electrode self-bias dc voltage level indicate operation in both negative as well as positive self-bias discharge modes. The latter mode, to our knowledge, has not been reported previously in rf microdischarges at near atmospheric pressures.