C-Ti nanocomposite thin films:: Structure, mechanical and electrical properties

Carbon-titanium nanocomposite thin films were deposited by DC magnetron sputtering on oxidized silicon substrates in argon. The films were prepared at different deposition temperatures between 25 and 800 degrees C. Transmission electron microscopy was used to determine the structure of the films. All the C-Ti nanocomposites consisted of columnar TiC structure with average column width similar to 10 and 20 nm and a thin carbon matrix. The thickness of the carbon matrix between adjacent TiC columns was similar to 2-5 nm. Mechanical properties (hardness, reduced modulus) of C-Ti films showed a distinct variation depending on the deposition temperature. Films deposited at 200 degrees C had the highest hardness similar to 18 GPa and the highest reduced modulus similar to 205 GPa. Temperature dependence of the film resistance was measured between 80 and 330 K. C-Ti nanocomposites have a non-metallic conduction mechanism characterized by a negative temperature coefficient of resistivity (TCR). The most negative TCR was observed for films showing high hardness and reduced modulus of elasticity. (C) 2007 Elsevier Ltd. All rights reserved.