Structural, electrical and mechanical characterization of magnetron-sputtered V-Ge-C thin films

V2GeC MAX-phase thin films were deposited by DC magnetron sputter epitaxy in the temperature range 450-850 deg. C. The MAX-phase nucleates directly on (0 0 0 l)-oriented sapphire-wafer substrates without the need for a seed layer. The films contain, however, a small fraction of binary vanadium carbide (VCx) inclusions. X-ray diffraction analysis furthermore shows that these inclusions partly consist of the ordered superstructure V8C7. The amount of Ge in the films decreases at higher temperatures, which can be attributed to Ge evaporation. At temperatures below 450 deg. C the films consist of polycrystalline Ge and an X-ray amorphous carbide phase attributed to VCx or V2C. No MAX-phase was observed in this temperature region. The electrical and mechanical properties of the films were characterized