TIME-RESOLVED OPTICAL-EMISSION SPECTROSCOPY OF AN INDUCTIVELY-COUPLEDPLASMA IN ARGON AND OXYGEN

We present the space-time resolved excitation data for a single coil i nductively coupled plasma (ICP) reactor operating in collision dominat ed regime in argon and oxygen at 13.56 MHz. Robot assisted scanning wa s used in order to obtain Abel inverted radial profiles of emission an d subsequently of the net excitation rate as well as the number densit y of excited states. The net excitation rate in argon has modulation c lose to the walls due to the azimuthal field time dependence and a lar ge bulk value independent of the time presumably due to low energy ele ctron-metastable atom collisions. The time resolved profile in oxygen shows a much more pronounced modulation due to the azimuthal field and a much lower degree of excitation for the center of the tube. At low pressures a structure is observed in the temporal dependence of the ne t excitation rate that is consistent with two different mechanisms of electron acceleration with phase shift of pi/4: (I) by azimuthal field and (II) due to the drift motion in crossed electric and magnetic fie lds that leads to a motion in the azimuthal or radial direction and co nsequently to energy gain.