Etching and Post-Treatment Surface Stability of Track-Etched Polycarbonate Membranes by Plasma Processing Using Various Related Oxidizing Plasma Systems

Oxidizing plasmas (O-2, CO2, H2O (g), and formic acid (g)) were used to modify track-etched polycarbonate (PC) membranes and explore the mechanisms and species responsible for etching. Etch rates were measured using scanning electron microscopy; modified surfaces were characterized with X-ray photoelectron spectroscopy and water contact angle. These results were combined with optical emission spectroscopy to provide insight into etch mechanisms. Although oxide functionalities implanted were similar, H2O (g) and formic acid vapor plasmas yielded the lowest contact angles. The CO2, H2O (g), and formic acid (g) plasma-modified surfaces were found to be similarly stable 1 month after treatment. Etch rate correlated directly to the relative gas-phase density of atomic oxygen and hydroxyl radicals.