Nanomechanical and Nanotribological Properties of Carbon, Chromium, and Titanium Carbide Ultrathin Films

Abstract

The nanomechanical and nanotribological properties of 10-nm-thick amorphous carbon (a-C) films and 100-nm-thick polycrystalline chromium (Cr) and titanium carbide (TiC) films were investigated using a surface force microscope (SFM). The films were deposited on Si(100) substrates by radio frequency (RF) sputtering and pulsed laser deposition (PLD) techniques. The experiments were performed with diamond tips of nominal radius of curvature equal to 20 nm, 100 nm, and 20 μm, and contact forces in the range of 3–400 μN. Nanoindentation experiments performed with the 20-nm-radius pyramidal diamond tip revealed that, for a 20 μN maximum contact force, the deformation of the a-C films was purely elastic, whereas that of the Cr film and Si(100) substrate was predominantly plastic. Although the RF sputtered a-C films and the PLD films of TiC exhibited similar nanohardness (∼40 GPa), the a-C films showed a superior nanowear resistance. Despite the identical hardness-to-elastic modulus ratio values of the RF sputtered polycrystalline Cr films and the single-crystal Si(100) substrate, the Cr films demonstrated a greater nanowear resistance. The wear behavior of the films is interpreted in terms of the relative specific energy dissipated during the nanowear process. Results from nanowear tests show that, in addition to the nanohardness and hardness-to-elastic modulus ratio, the microstructure, type of atomic bonding, and deposition process affecting the composition and residual stress in the films influence the nanowear resistance of the films.