Instabilities in cc-rf oxygen plasma

Instabilities are investigated in low density oxygen cc-rf plasmas driven at 13.56 MHz. They are analyzed by means of three different diagnostics. Firstly, they are measured as electron density fluctuations by means of 160GHz microwave interferometry [1]. Secondly, the instabilities are recorded by spatio-temporal resolved Langmuir probe measurement as fluctuation of floating potential and ion saturation current. Thirdly, it is used a ICCD camera to investigate the optical emission intensity fluctuations. Thereby, two different time scales are considered. It concerns the time resolved intensity measurement during the instability (TROES) averaged over rf cycles, and the rf phase resolved (PROES) measurements at different phase position within the instability cycle.