Wettability of nanocrystalline diamond films

The wettability of nanocrystalline CVD diamond films grown in a microwave plasma using Ar/CH4/H2 mixtures with tin melt (250–850 °C) and water was studied by the sessile-drop method. The films showed the highest contact angles θ of 168 ± 3° for tin among all carbon materials. The surface hydrogenation and oxidation allow tailoring of the θ value for water from 106 ± 3° (comparable to polymers) to 5° in a much wider range compared to microcrystalline diamond films. Doping with nitrogen by adding N2 in plasma strongly affects the wetting presumably due to an increase of sp2-carbon fraction in the films and formation of C–N radicals.