Electron-anion separation in electronegative rf microdischarges

Several types of double-layer structures have been reported previously in the literature and the stratification of negatively charged species in electronegative discharges is a well known phenomena. Here we report on the evolution of a different type of double layer structure found in electronegative microplasmas. In these microdischarges, the electron ensemble oscillates between the electrodes forming sheaths that are larger than half the discharge gap. As the electrons oscillate, they move across and beyond a central electronegative core formed by anions. As a result of their different motion, electrons and anions are completely separated and regions of positive space charge form between the oscillating electron ensemble and the central electronegative discharge.