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

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 T-s (20-800 degreesC) and dc substrate bias voltage U-b (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 sp(2) 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 degreesC interval occurs by temperature induced graphite-like ordering of small areas within D-phase (G-phase nucleation). In the 500-800 degreesC 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 less than or equal toU(b)less than or equal to -150 V are accompanied by decreasing of G-phase clusters size and simultaneous certain disordering in their internal structure. At U-p > - 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. (C) 2001 Elsevier Science B.V. All rights reserved.