Deposition and characterization of ultra thin diamond like carbon films

Amorphous hydrogenated and/or nitrogenated carbon films, a-C:H/a-C:N, in overall thickness up to 2 nm are materials of choice as a mechanical and corrosion protection layer of the magnetic media in modern hard disk drive disks. In order to obtain high density and void-free films the sputtering technology has been replaced by different plasma and ion beam deposition techniques. Hydrocarbon gas precursors, like C2H2 or CH4 with H2 and N2 as reactive gases are commonly used in ion and plasma beam sources. Optimum incident energy of carbon ions, C, is up to 100 eV while the typical ion current densities during the film formation are in the mA/cm range. Other carbon deposition techniques, like filtered cathodic arc, still suffer from co-deposition of fine nano-sized carbon clusters (nano dust) and their improvements are moving toward arc excitation in the kHz and MHz frequency range. Non-destructive film analysis like μ-Raman optical spectroscopy, spectroscopic ellipsometry, FTIR and optical surface analysis are mainly used in the carbon film characterization. Due to extreme low film thicknesses the surface enhanced Raman spectroscopy (SERS) with predeposited layer of Au can reduce the signal collection time and minimize photon-induced damage during the spectra acquisition.