Thermo-Oxidative Stability of SiOx-doped Diamondlike Carbon Studied via Environmental XPS and AFM

A broad array of carbon-based thin films, such as diamond, diamond-like carbon (DLC), and others, have been developed over the last several years [1]. These materials exhibit high strength and stiffness, low friction and wear, tolerance to withstand harsh physical and chemical conditions, and can form smooth, continuous, conformal coatings. This has resulted in their use in a wide range of applications. However, the strong environmental dependence of the tribological properties of DLC coatings limits their widespread use. For example, hydrogenated amorphous carbon (a-C:H) rapidly degrades above 150°C due to evolution of hydrogen followed by conversion of C from sp 3 to sp 2 -hybridization [2, 3]. Thus, several variants of DLC have been developed. Among these, silicon oxide-doped DLC (SiOxDLC) is of interest as it exhibits very good tribological properties across a range of environments [4]. SiOx-DLCs are fully amorphous coatings supposedly consisting of two interpenetrating, interbonded networks, one being a hydrogenated amorphous carbon network and the other a silica glass (SiOx) network [5]. SiOx-DLC are thus attractive candidates as advanced solid lubricants, including as candidates for next-generation hard-disk storage devices, which require superior thermal stability [6].