Transition from E to H mode in inductively coupled oxygen plasma: Hysteresis and the behaviour of oxygen atom density

Jozef Stefan Institute - Jamova 39, 1000 Ljubljana, Slovenia, EU

^a miran.mozetic@ijs.si

Received: 26 May 2011
Accepted: 13 July 2011

Abstract

Transitions from E to H mode in electrodeless discharges created in pure oxygen at pressures from 10 Pa to 160 Pa are studied. An RF coil is placed at the centre of a long quartz tube and connected to an RF generator via a matching network. The generator operates at a frequency of 13.56 MHz and adjustable power up to 1200 W. The voltage and current on the coil are measured with a commercial voltage probe and a current probe connected to an oscilloscope, while the density of neutral O-atoms is measured with a catalytic probe. The results show the appearance of current and voltage hysteresis at moderately low pressure, the hysteresis being more pronounced at higher pressure. The O-atom density does not depend much on the mode at low pressure. As the pressure increases, a rapid increase of the O-atom density is observed at the transition between the E and the H mode. The hysteresis in the O-atom density is observed as well.