Control over the wettability of amorphous carbon films in a large range from hydrophilicity to super-hydrophobicity

Control of wettability is of significance in industry as well as our daily live. Amorphous carbon (a-C) films with nanostructured surface were deposited on silicon and glass substrates at different substrate temperatures through a magnetron sputtering technique. The microstructures of the a-C films were studied by SEM and XPS, which indicate that the surface of the a-C films deposited at room temperature are smooth due to their much dense sp(3)-bonded carbon, while they turn to be more porous graphite-like structure with elevated deposition temperature. The water contact angle (CA) measurements show that these pure carbon films exhibit different wettability, ranging from hydrophilicity with CA less than 40 degrees to super-hydrophobicity with CA of 152 degrees, which reveal that the surface wettability of a-C films can be controlled well by using nanostructures with various geometrical and carbon state features. The graphite-like carbon film deposited at 400 degrees C without any modification exhibits super-hydrophobic properties, due to the combining microstructures of spheres with nanostructures of protuberances and interstitials. It may have great significance on the study of wettability and relevant applications. (c) 2006 Elsevier B.V. All rights reserved.