Experimental studies of high pressure RF discharges

Summary form only given, as follows. Experimental studies on RF discharges at 13.56 MHz have been performed at very high gas pressures between 1 Torr to atmospheric pressure. Plasma parameters, comparable to low pressure discharges, are estimated in He discharges by optical emission spectroscopy and Langmuir probe measurements. The estimated electron density of 1-10/spl times/1011 cm-3 and electron temperature of 1-2 eV is consistent with a 1-D model of plasma impedance and particle balance. The plasma conditions change substantially as oxygen is introduced into the discharge. A decrease in electron density is observed, which is attributed to the electronegativity of oxygen. In addition, formation of oxygen atoms and metastable oxygen molecules is observed by optical emission spectroscopy. A further increase in the oxygen flow results in the extinction of the discharge or arcing. A detailed analysis of the experimental results will be presented.