Modest RF
power of less than 1 kW at 13.56 MHz has been applied
to two electrodes through a standard RF matching
network. Helium as the main carrier gas, argon as the
additional carrier gas, and oxygen as the reactive gas
are introduced into the plasma generation chamber
through mass flow controller. Gas temperatures are
obtained from rotational temperatures of OH molecules
by analysing ultraviolet (UV) molecular emission spectra w10,11x. Since intensities of oxygen radicals may
also be measured with optical emission spectroscopy
w2,3,8x, two different views for optical emission spectroscopy are provided as shown in Fig. 1b.