AVS 47th International Symposium
    Plasma Science and Technology Tuesday Sessions
       Session PS2-TuA

Paper PS2-TuA9
C@sub x@H@sub y@ Radical Measurements using Cavity Ring Down Spectroscopy in a Remote Ar/C@sub 2@H@sub 2@ Plasma

Tuesday, October 3, 2000, 4:40 pm, Room 311

Session: Plasma Diagnostics I
Presenter: M.C.M. van de Sanden, Eindhoven University of Technology, The Netherlands
Authors: M.C.M. van de Sanden, Eindhoven University of Technology, The Netherlands
K.Y. Letourneur, Eindhoven University of Technology, The Netherlands
M.G.H. Boogaarts, Eindhoven University of Technology, The Netherlands
D.C. Schram, Eindhoven University of Technology, The Netherlands
Correspondent: Click to Email
The ground state densities of C@sub x@H@sub y@ (x = 1,2, y = 0, 1) radicals in a remote Ar-C@sub 2@H@sub 2@ plasma used for high rate deposition of hard hydrogenated amorphous carbon films (a-C:H, rates up to 500 Å/s) have been investigated in detail by cavity ring down absorption spectroscopy (CRDS). Both C@sub 2@ and CH could be spectroscopically identified and measured as function of C@sub 2@H@sub 2@ gas flow admixture. From previous studies we deduced that the main dissociation products of C@sub 2@H@sub 2@ dissociation in our remote plasma is C@sub 2@H and H. In an attempt to measure the ground state density of C@sub 2@H we looked for a spectroscopic signature in the 260-280 nm region where Laser Induced Fluorescence measurements of ground state C@sub 2@H have been reported. No clear spectroscopic fingerprint of C@sub 2@H@sub 2@ could be measured although a clear broadband absorption is observed. The absence of a fingerprint of the C@sub 2@H radical could be due to the limited spectral resolution (0.7 cm@sup -1@) of the laser system used. Another plausible reason could be the hostile plasma environment (including formation of clusters) which influences the formation process of C@sub 2@H to such an extend (in terms of excitation of rovibrational and electronic states) that broadband absorption results. However, the broadband absorption measured as function of the C@sub 2@H@sub 2@ gas flow admixture shows trends we expect from the C@sub 2@H radical. In an attempt to resolve the problems faced we have designed an experiment in which we measure the C@sub 2@H radical using simultaneously threshold ionization mass spectrometry and cavity ring down spectroscopy. First results of these experiments will be presented.