Influence of different physical factors on microstructure and properties of magnetron sputtered amorphous carbon films


I. M. Frantsevich Institute for Problems of Materials Science of the NAS of Ukraine, Krzhizhanovsky str., 3, Kyiv, 03142, Ukraine
Thin Solid Films: Elsevier, 2001, Т.1/2, #397


Structure evolution of amorphous carbon (a-C) films deposited by dc magnetron sputtering of graphite in argon was investigated as a function of substrate temperature Ts (20–800°C) and dc substrate bias voltage Ub (floating — −175 V). Film structure was studied by transmission electron microscopy, selected area electron diffraction, reflective high energy electron diffraction and Raman spectroscopy. Film resistivity in two directions — parallel and perpendicular to the substrate — was also measured. The results obtained allow for the assumption that the film structure is based on coexistence of D- and G-phases formed of sp2 bonded carbon atoms. G-phase consists of small graphite-like ordered areas embedded in continuous uniform amorphous D-phase. The evolution of a-C film structure in 20−450°C interval occurs by temperature induced graphite-like ordering of small areas within D-phase (G-phase nucleation). In the 500–800°C range the change of C-film growth mechanism takes place. Instead of nucleation of the G-phase within the D-phase the initial nuclei of graphite phase appears on the substrate. The changes of a-C film microstructure under the ion bombardment in the range of −20≤Ub≤−150 V are accompanied by decreasing of G-phase clusters size and simultaneous certain disordering in their internal structure. At Ub>−150 V the cluster structure tends to be more ordered towards it graphitization. The effect of graphite-like clusters ‘texturing’ revealed in a-C films under the ion bombardment is discussed.