Induced Hydrophilicity and Oxidation of β‑Iron Disilicide Films by Varying Ar Plasma Etching Durations

Induced hydrophilicity and oxidation of β-iron disilicide thin films using 300 W microwave Ar plasma for 5-15 min were investigated experimentally and statistically. Plasma diagnostics revealed cold plasma characteristics with a stable electron temperature (0.287-0.283 eV) and a gradually accumulated electron density over time. X-ray photoelectron spectroscopy analysis revealed reduced adventitious carbon and an increased presence of hydrophilic oxide and hydroxyl groups forming on vacant bonds accumulated over time on the activated surface after sputter ion bombardment. The film morphology demonstrated a roughness of 4.10 nm after 15 min of etching from the original roughness of 2.52 nm due to the shape evolution of nanoscale spikes and valleys on the surface after ion impact. Owing to these tandem surface morphology changes and chemical modifications, the contact angle decreased from 96.13° (hydrophobic) to 69.08° (hydrophilic) after 15 min, while maintaining the mechanical properties intact. This active surface with a contact angle under 70° has implications for further fabrication of polymer interlayers and other metallic coatings onto the top of the surface as a possible use case in the vehicular and electronic industries.