S. Behle et al., IMAGING OF ATOMIC OXYGEN IN A MICROWAVE EXCITED OXYGEN PLASMA WITH 2-DIMENSIONAL OPTICAL-EMISSION SPECTROSCOPY, Surface & coatings technology, 97(1-3), 1997, pp. 734-741
The density distribution of atomic oxygen was investigated in a pure o
xygen microwave discharge. Plasma is excited by use of a circular wave
guide with slot antenna. Two-dimensional maps of the O((3)p P-3) to O(
3s S-3(0)) emission line intensity have been obtained using planar opt
ical emission spectroscopy imaging (FOES). The dependence on operating
parameters of the plasma source has been studied. With increasing pre
ssure the atomic oxygen homogeneity degrades. At pressures below 20 Pa
the oxygen density is nearly homogeneous due to the greater diffusion
length. Absolute ground state concentration of atomic oxygen has been
measured at a downstream position by two-photon laser-induced fluores
cence (LIF). Values in the range of 10(13)-10(14) cm(-3) are obtained.
Comparing FOES to LIF results the POPS signals must be corrected for
line-of-sight path integration. If this is taken into account then LIF
and FOES measurements show a good correlation between atomic ground s
tate and excited oxygen for pressures up to 50 Pa. (C) 1997 Elsevier S
cience S.A.