Electrochemical deposition and characterization of diamond-like carbon films doped with surface-capped silica nanoparticles

Diamond-like carbon films doped with surface-capped nanosilica (nano-SiO2/DLC) were prepared on Si substrate via electrochemical deposition of dimethyl sulfoxide (DMSO) as the carbon source and nanosilica as the dopant. Undoped DLC films were also prepared at various deposition durations for comparative studies. It has been found that silica nanoparticles are well embedded in amorphous carbon matrix forming nanosilica-doped DLC composite films, confirmed by transmission electron microscopy (TEM). In particular, Raman and AFM analysis revealed the as-obtained composite films consist of both tetrahedral (sp3) and trigonal (sp2) bonded C species, and silica incorporation results in variation of surface roughness, decrease of sp3-hybridized carbon concentration and enhancement of graphitization. Furthermore, nanosilica surface-capped with organic compound containing hydroxyl group is doped in amorphous carbon film by forming SiO bond, which helps to lower the surface energy and induce hydrophilic to hydrophobic transformation of the carbon films. Tribology tests also showed that composite films have better friction and wear behaviors, compared with pure carbon film.