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Microstructure evolution as a function of the substrate temperature and metal content of C:Ni nanocomposite films grown by hyperthermal ion deposition is investigated. The films were grown by pulsed filtered cathodic vacuum arc on thermally oxidized Si substrates held at temperatures in the range from room temperature (RT) to 500 °C and with the metal content ranging from 7 to 40 at. %. The elemental depth profiles and composition were determined by elastic recoil detection analysis. The film morphology and phase structure were studied by means of cross-sectional transmission electron microscopy and selected area electron diffraction. For RT deposition a transition from repeated nucleation dominated toward self-organized growth of alternating carbon and crystalline nickel carbide layers is observed at a Ni threshold content of ∼40 at. %. The surface diffusion increases concomitantly with the growth temperature resulting in the formation of elongated/columnar structures and a complete separation of the film constituents into the coexisting carbon and fcc Ni phases. At the highest growth temperature (500 °C) Ni shows a tendency to segregate at the surface of the growing film and to form a continuous layer for integrated Ni contents of ≥30 at. %. A corresponding structure zone model diagram is presented, and the results are discussed on the basis of the ion induced atomic displacement, temperature activated adatom diffusion, and the metallic island coalescence processes whose complex interplay results in the observed variety of the microstructures.

Interdependence between stress, preferred orientation, and surface morphology of nanocrystalline TiN thin films deposited by dual ion beam sputteringThe influence of transition metal (TM ¼ V,Co,Cu) type on the bulk diffusion induced structural changes in carbon:TM nanocomposite films is investigated. The TMs have been incorporated into the carbon matrix via ion beam co-sputtering, and subsequently the films have been vacuum annealed in the temperature range of 300 -700 C. The structure of both the dispersed metal rich and the carbon matrix phases has been determined by a combination of elastic recoil detection analysis, x-ray diffraction, transmission electron microscopy, and Raman spectroscopy. The as-grown films consist of carbidic (V and Co) and metallic (Cu) nanoparticles dispersed in the carbon matrix. Thermal annealing induces surface segregation of Co and Cu starting at ! 500 C, preceded by the carbide-metal transformation of Co-carbide nanoparticles at $ 300 C. No considerable morphological changes occur in C:V films. In contrast to the surface diffusion dominated regime where all the metals enhance the six-fold ring clustering of C, in the bulk diffusion controlled regime only Co acts as a catalyst for the carbon graphitization. These results are consistent with the metal-induced crystallization mechanism in the C:Co films. The results are discussed on the basis of the metal-carbide phase stability, carbon solubility in metals or their carbides, and interface species.

Carbon-nickel (C-Ni