Superhydrophilic cubic boron nitride films

High-quality, fluorinated cubic boron nitride (cBN) films are prepared by plasma-enhanced chemical vapor deposition, and followed by plasma treatment using hydrogen or oxygen gas with or without low-energy (<40 eV) ion irradiation. Wettability of the plasma-treated films is enhanced only moderately in both hydrogen and oxygen gases without ion irradiation, while it is enhanced markedly when using ion irradiation in hydrogen gas such that the contact angle of polar and apolar liquids is reduced down to almost zero degree. Low-energy hydrogen ions play a decisive role in removing surface-bonded fluorine atoms and forming polar bonds, thus accounting for a great increase in the polar component of the apparent surface free energy.