Structure and mechanical properties of nanocrystalline diamond films

Phase-pure nanocrystalline diamond thin films grown in hydrogen-poor carbon argon plasmas have been characterized by scanning electron microscopy and microhardness measurements. In the initial growth stage, round half-spheres are observed, which expand into a continuous smooth thin film with increasing growth time. This is explained by considering frequent diamond-on-diamond nucleation on the growing crystallites, which leads to an isotropic expansion of the initial seeds on the substrates in the form of half-spheres and later to the formation of a smooth surface. In addition, microhardness measurements revealed that 5 pm thin films are superhard and fully elastic.