Argon gas breakdown with bare and insulated electrodes in dc-biased RF field

Argon gas breakdown in RF and dc combined electric fields (dc-biased RF field) is investigated experimentally and theoretically for two parallel electrode systems of bare metals and glass-covered metals. To simulate breakdown, electron and ion density equations based on a charged particle balance model are numerically solved taking account of the secondary electron emission according to different electrode surface conditions. The calculated breakdown voltages are in agreement with the data observed with the bare electrode. In the insulated electrode system, RF breakdown is achieved with a time lag after application of RF and dc voltages to the electrode and the RF breakdown voltages at fixed pressures decrease with the time lag while increasing with the dc voltage. The generation of electric field by the charge accumulation on the glass surfaces is considered to affect the RF breakdown. In the case of short-time-lag breakdown for which the charge accumulation is ignored, the RF breakdown voltage increases with the dc voltage and then saturates at higher dc biases in contradiction to the prediction that the RF voltage should increase continuously.