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Abstract: The grain-size effect on the preferred orientation has been revealed in TiC/α-C:H nanocomposite films grown by magnetron sputtering, in which the grain size of TiC can be adjusted through changing C content in films. The finding is that the preferred orientation of films is significantly affected by the grain size, and the crystallographic orientation changes from face-centered cubic (fcc) TiC(111) to (200) as the grain size of nanocrystallite TiC decreases from ∼22.3 to ∼4.7nm. This size-dependent preferred orientation is explained via thermodynamic calculations, from which the size-dependent Gibbs free energies are found to be a key factor that controls the texture development in thin films if the grain size in films is sufficient small. [Copyright &y& Elsevier]

Abstract: We have deposited germanium carbide (Ge1−x C x ) films on Si(100) substrate via radio-frequency (RF) reactive magnetron sputtering in a CH4/Ar mixture discharge, and explored the effects of carbon content (x) on the chemical bonding and hardness for the obtained films. We find that x significantly influences the chemical bonding, which leads to a pronounced change in the hardness of the film. To reveal the relationship between the chemical bonding and hardness, first-principles calculations have been carried out. It is shown that as x increases from 0 to 0.33, the fraction of sp3 C–Ge bonds in the film increases at the expense of Ge–Ge bonds, which promotes formation of a strong covalently bonded network, and thus enhances the hardness of the film. However, as x further increases from 0.33 to 0.59, the fraction of sp3 C–Ge bonds in the film gradually reduces, while that of sp3 C–H and graphite-like sp2 C–C bonds increases, which damages the compact network structure, resulting in a sharp decrease in the hardness. This investigation suggests that the medium x (0.17