Hydrophilic DLC Surface Induced by Nanostructures Formed by RF O2 Plasma Etching With Metal Micromasks

Long pillar- and tip-shaped nanostructures were formed on diamond-like carbon (DLC) surfaces by RF O₂ plasma etching after deposition of a small amount of metal as a micromask by the dc magnetron sputtering method. Ni, Pt, Fe, Au, and Cu were examined as metal micromasks for deposition on the DLC surface. During the initial etching stage, nanostructures appeared on all of the DLC surfaces with each of the metal micromasks. The initial nanostructures were induced by anisotropic etching with the micromasks of aggregated metal. As the etching duration was increased, the nanostructures grown with Ni and Fe micromasks appeared to be lengthened, while the nanostructures induced by Pt, Au, and Cu completely disappeared. O2 plasma etching for 5 min after deposition of a 0.15-nm thick Ni layer resulted in complete coverage of the DLC surface with fine nanostructures around 30 nm in diameter, 60 nm in height, and an areal number density of 1500 μm^-2. The resultant surface had hydrophilic characteristics with a small water contact angle of 13°.