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Graduate Student Seminar - 10/20/2017

"Cold Temperature Plasma-Surface Interaction at Atmospheric Pressure: Polystyrene Etching and Modification"

by Pingshan Luan

Friday, October 20, 2017 -- 12:00 p.m.
Large Conference Room, 1207 Energy Research Facility

Advisor:  Professor Gottlieb Oehrlein

Cold atmospheric pressure plasma jets (APPJs) are able to generate a long but narrow plasma plume which contains chemically reactive species useful for applications such as material processing, water/air purification and microbial inactivation. While impressive source characterization results have been published, less is known about the interaction mechanisms of these sources with surfaces, e.g. of cells, biomolecules, and polymers. To build correlation between gas phase species and material surface responses, a system with well-characterized radio frequency (RF) plasma jet, polystyrene (PS) as model polymer and highly-controlled environments was adopted for understanding the physics of plasma-surface interaction (PSI) at atmospheric pressure. A number of plasma processing parameters, such as treatment distance and angle, feed and environment gas compositions, were investigated by evaluating both polymer thickness and surface chemical composition change after treatment. We compared the effect of different plasma species on polymer surfaces. The etching reaction probability of atomic O and OH radicals were evaluated and found to be ~10-4 and ~10-2 for O and OH, respectively. Additionally, the apparent activation energy (Ea) of etching reactions was measured by varying substrate temperature. We found the Ea of Ar/O2 plasma etching reaction with PS is in the range of 0.10 – 0.13 eV and increases slightly with treatment distance.

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