Nanotribological properties of silicon doped diamond-like carbon films for hard disk drives

Diamond-like carbon (DLC) films which contain a mixture of sp2 and sp3 hybridizations are widely used as a protective layer against wear and corrosion in hard disk drives (HDDs) due to their outstanding mechanical and tribological properties such as high hardness, low friction coefficient and excellent chemical durability [1]. The typical thickness of DLC film in HDD is approximately 1-2nm. For such an ultra-thin film, DLC shows a high internal stress and low adhesion with the substrate, thereby resulting in the failure of protection to the magnetic layer. In addition, the DLC film has an inferior thermal stability and can be oxidized or graphitized for a high temperature used in heat assisted magnetic recording [2]. The incorporation of Silicon (Si) into DLC films, which reduces the stress, improves adhesion to metal substrates, and increases the thermal stability, can be potentially used as a protective layer in the future HDD. As reported in the literature, the structures and tribological properties are greatly affected by the content of Si doped DLC film. However, some of the experimental results show opposite direction, e.g., Hardness and elastic modulus have been reported to either increase or decrease or even remain constant [3-4]. Thus, the nanomechan-ical and nanotribological properties of Si doped DLC film is not well understood and requires further investigation. The objective of this study is to investigate the nanomechanical and nanotribo-logical properties, especially wear resistance of ultra-thin Si doped DLC films for different Si contents in atomic scale. In addition, the effect of density along with the Sp
³
/Sp
²
ratio on the wear resistance of Si doped DLC films is also studied.