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P: Plasmaphysik
P 12: Plasma Wall Interaction, Diagnostic and Low Temperature Discharges (Poster Session)
P 12.20: Poster
Freitag, 6. April 2001, 12:30–15:00, AT2
Mass spectrometric analysis of transient species in low temperature discharges — •Martin Geigl, Valentina Kroutilina, Hans-Erich Wagner, and Jürgen Meichsner — Institut für Physik, Universität Greifswald, Domstr. 10a, D-17489 Greifswald
Appearance Potential Mass Spectrometry (APMS) has recently gained importance for detection of reactive species in plasmas. We set up a new two stage differentially pumped mass spectrometer system. Due to the second pumping stage the background pressure in the ionization chamber is reduced. In addition to APMS we can use Electron Attachment Mass Spectrometry (EAMS) to detect electronegative species in the plasma. The advantage of EAMS is, that the degree of dissociation of the parent molecule during the ionization process is strongly reduced. The EAMS is a powerful tool for investigation of e. g. fluorocarbon plasmas.
We show first results of APMS of CFx−, N− and O−radicals in CF4−, N2− and O2−discharge, respectively. In the case of the O2−plasma the APMS measurements can be calibrated with results from TALIF (see poster by S. Peters et al.) which provide absolute flow rates of O–radicals. In CF4/H2−plasmas the chemical reactions were investigated by EAMS of the stable reaction products and the time behaviour of the reaction system was studied.