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Morphology, structure and growth pathways of carbon:transition metal nanocomposite thin films prepared by Ion beam co-sputtering
Krause, M.; Abrasonis, G.; Berndt, M.; Mücklich, A.; Munnik, F.; Kolitsch, A.; Möller, W.;
Nanocomposites (NC) represent a new class of composite materials, wherein at least one component has a size of =< 100 nm in one dimension. [1] They are expected to show improved properties compared to classical materials and conventional composites due to their higher number of interfaces and their smaller particle size. In this work ion beam co-sputtering (IBS) of carbon and the 3d metals V, Co, Ni, and Cu was used to prepare NC thin films. Stable and homogenous NC with good adhesion on silicon were obtained for all the metals in a composition range of 15 at.% to 40 at.% metal, although the stability of the corresponding metal carbides gets smaller from vanadium to copper.
The NC morphology and structure was investigated by transmission electron microscopy, x-ray diffraction, x-ray absorption and Raman spectroscopy. In general, the NC consisted of nanoparticles embedded in a carbon matrix. Depending on the growth parameters, i.e. the chemical nature of the metal and the deposition temperature, the NC morphology could be varied from spherical grains via ellipsoidal nanocrystals to vertical standing columns extending over the whole thickness of the thin films. The phase properties of the nanoparticles resembled those of the bulk phases. While VC was formed in the temperature range of RT-500°C and no carbide phase at all was obtained for copper, cobalt and nickel exhibited either carbidic or metallic nanoparticles. Independently of the metal type the surrounding carbon phase exhibits an enhanced 6-fold aromatic ring formation compared to pure carbon reference films grown at identical conditions. The enhancement is particularly strong for low growth temperatures. While the carbon phase in general consists of a superposition of nanocrystalline graphite and amorphous carbon, the degree of graphitization could be controlled by the incorporated metal and the growth temperature. The results indicate that phase stability, nucleation rate and surface diffusivity determine the growth pathway of carbon:transition metal NC thin films grown by IBS. [2]-[5]

[1] P. M. Ajayan, L.S. Schadler, P.V. Braun, Nanocomposite Science and Technology, Wiley-VCH, 2003
[2] G. Abrasonis, M. Krause, A. Mücklich, K. Sedlackova, G. Radnoczi, U. Kreissig, A. Kolitsch, W. Möller, Carbon, 45, 2995-3006 (2007)
[3] M. Krause, G. Abrasonis, A. Kolitsch, A. Mücklich, U. Kreissig, W. Möller, Phys. Stat. Sol. (B), 244, 4236-4239 (2007)
[4] G. Abrasonis, A. Scheinost, S. Zhou, R. Torres, R. Gago, I. Jimenez, K. Kuepper, K. Potzger, M. Krause, A. Kolitsch, W. Möller, S. Bartkowski, M. Neumann, R. Gareev, J. Phys. Chem. C, 112, 12628-12637 (2008)
[5] G. Abrasonis, M. Berndt, M. Krause, K. Kuepper, F. Munnik, A. Kolitsch, W. Möller, J. Phys. Chem. C, in press, 2008

Keywords: Composites, Ion beam sputtering, growth, structure
  • Invited lecture (Conferences)
    SIWAN 2008 - 4th Szeged International Workshop on Advances in Nanoscience, 09.-10.10.2008, Szeged, Hungary

Publ.-Id: 11866 - Permalink