An analysis of the nanotribological behaviour of Ti-containing hard carbon film

Abstract

Diamondlike carbon (DLC) coatings are well known for their self-lubricating properties. Metal-containing DLC films exhibit reduced internal stress, improved adhesion and reduced sensitivity to humidity. Furthermore, Ti-containing DLC coatings are compatible with biological environments. In view of this, the primary aim of the present work was to evaluate and analyse the friction force behaviour of Ti-containing hard carbon films. This work is primarily intended for application to microelectromechanical systems. In order to achieve the above mentioned objective, a hard carbon layer containing 6 at.-%Ti was deposited using an unbalanced magnetron sputter system on a silicon substrate. The deposition rate of the film was monitored by a quartz microbalance. Using a stylus profilometer, the thickness of the film was found to be 1·67 μm. The hardness and the elastic modulus of the film were determined using a nanoindenter. The hardness and the elastic modulus were determined to be 1·7 GPa and 17·7 GPa, respectively. The pull-off force, topography and friction force surface of the film were characterised with the use of an atomic force microscope. The pull-off force and the friction force were found to be 165·9 nN and 1·7 nN, respectively. The surface roughness Ra was found to be 2·65 nm. The friction coefficient was evaluated as a ratio of the friction force and the summation of the pull-off force and the normal force. Using the topography, and lateral force image, the topography induced friction force surface and the adhesion induced friction force surface were evaluated. The influences of applied loads and scan speeds on friction coefficient and various friction force surfaces are described in detail.