Plasma chemistry of an expanding Ar/C2H2 plasma used for fast deposition of a-C : H

Mass spectrometric measurements in combination with Langmuir probe measurem ents reveal that the plasma chemistry of an expanding Ar/C2H2 is dominated by argon-ion-induced dissociation of the precursor gas. Under high are curr ent conditions complete depletion of acetylene is observed, indicating an e fficient consumption of the injected acetylene. A clear correlation between the ion fluence emanating from the are determined from modeling the mass s pectrometry results and Langmuir probe measurements is observed. First meas urements by means of cavity ring down and optical emission spectroscopy of the products of the dissociation of acetylene indicate that the dominant di ssociation channel is C2H and H. (C) 1999 Elsevier Science S.A. All rights reserved.