Darmstadt 2008 – scientific programme
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P: Fachverband Plasmaphysik
P I: Poster: Staubige Plasmen, Dichte Plasmen
P I.19: Poster
Tuesday, March 11, 2008, 08:30–10:30, Poster C3
Study of powder formation in pulsed and continuous rf processing plasmas using TDLAS — •Hoang Tung Do and Rainer Hippler — Institut für Physik, Universität Greifswald, Felix-Hausdorff-Str. 6, 17489 Greifswald, Germany
The time dependence of argon metastable density was investigated in pulsed and continuous processing rf plasmas with Ar/C2H2 and Ar/CH4 gas mixtures by means of tunable diode laser spectroscopy. The density of argon metastable state is sensitive for the dust formation and the change of dust density and size as well as reactive gas density and composition. The metastable density therefore can be used as the indicator for the time evolution of dust generations and the dust formation onset which is inaccessible with laser scattering method. The significant difference between pulsed and continuous plasmas is the "off phase" in pulsed mode where negative ions can escape while dust particles can not and be recharged later on in the "on phase". The role of negative ions in the growth dynamics of dust particles in processing plasmas is clarified by comparing the time dependence of metastable density in pulsed and continuous plasmas.