Reactivity zones around an atmospheric pressure plasma jet

• Published in: Applied surface science 2015-11, Vol.354, p.420-428
• Main Author: Birer, Oezguer
• Format: Article
• Language: English
• Subjects: Atmospheric pressure; Atmospheric pressure plasma jet; Barometric pressure; Etching; Helium plasma; Molecular ions; Photons; Reactivity zones; Spatial distribution; Surface treatment; X-ray photoelectron spectroscopy
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2015.04.100

•Polyethylene surfaces were treated with atmospheric pressure cold plasma jet.•The effect of plasma extends beyond the physical jet diameter.•Moieties of –NO, –COO, –CO and –NO3 as expanding ring patterns were detected.•Active species in the plasma are identified for specific surface moieties. The reactivity zones around an atmospheric pressure plasma jet are revealed by XPS mapping of chemical moieties on a polyethylene surface treated with a 3-mm plasma jet. The area directly hit by the helium plasma jet initially oxidizes and later etches away as the plasma treatment continues. The oxidation initially starts at the center and expands outwards as a ring pattern with different spatial potency. At the end of 10min plasma jet treatment, distinct ring patterns for –NO, –COO, –CO and –NO3 species can be detected with respectively increasing diameters. The plasma jet can cause chemical changes at locations several millimeters away from the center. The spatial distribution of oxidized species suggests presence of chemical reactivity zones. Introduction of nitrogen into the helium plasma jet, not only increases the type of nitrogen moieties, but enriches the reactivity zones by generating nitrogen molecular ions within the plasma jet. The complex competing reaction mechanisms among the radicals, ions, metastable atoms and UV photons lead to unusual etching patterns on the surfaces.