Hydrophilicity Difference of TiO2 Thin Films Induced by Different Plasmas

Anatase nanocrystal TiO2 thin films with superhydrophilicity were fabricated by reactive magnetron sputtering metal Ti target followed by thermal annealing in air. The thin films were irradiated with radio frequency (RF) oxygen or nitregon plasmas with various parameters. Oxygen or nitrogen plasmas irradiation for suitable time with suitable RF power can induce hydrophilicity comparable to photohydrophilicity. The best hydrophilicity was induced by irradiation of the thin films with nitrogen plasma first and followed by oxygen plasma. The irradiated thin films were kept under different light environment to study the light stability. It was found that thin films irradiated with oxygen plasma show highly stable superhydrophilicity whenever kept in dark or under visible light, but for nitrogen plasma-irradiated thin films, the superhydrophilicity deteriorates when kept in dark.