AVS 45th International Symposium
    Plasma Science and Technology Division Monday Sessions
       Session PS2-MoA

Paper PS2-MoA6
Cavity Ring Down Spectroscopy on an expanding Ar/C@sub 2@H@sub 2@ Plasma

Monday, November 2, 1998, 3:40 pm, Room 318/319/320

Session: Diagnostics I
Presenter: M.G.H. Boogaarts, Eindhoven University of Technology, The Netherlands
Authors: A.H.M. Smets, Eindhoven University of Technology, The Netherlands
K.G.Y. Letourneur, Eindhoven University of Technology, The Netherlands
M.G.H. Boogaarts, Eindhoven University of Technology, The Netherlands
M.C.M. van de Sanden, Eindhoven University of Technology, The Netherlands
D.C. Schram, Eindhoven University of Technology, The Netherlands
Correspondent: email address not available
In this contribution we present the first results obtained from a cavity ring down spectroscopy (CRDS) setup for the detection of low density species in a plasma reactor. In this reactor research is carried out on the use of an expanding plasma beam produced by a cascaded arc for the fast deposition of thin films. In the plasma beam acetylene is dissociated in several radicals which will react at the substrate to form hydrogenated amorphous carbon (a-C:H) films. At the moment the C@sub 2@H radical is considered to be responsible for the diamondlike quality of the a-C:H films. The aim of this project is to measure radical densities (C@sub 2@H, CH and H(n=2)) by using CRDS technique. CRDS is an absolute absorption technique based upon the measurement of the rate of absorption of the light pulse confined in an optical cavity. The absolute density of the n = 2 state of atomic hydrogen has been measured in an Ar/C@sub 2@H@sub 2@ expanding deposition plasma. From the measured H(n=2) densities it can be concluded that the C@sub 2@H radical is produced dominantly in an expanding Ar/C@sub2@H@sub2@ plasma. The results obtained by CRDS measurements on radicals will be used to develop a model for the growth of a-C:H films.