Electrical behavior of nickel/carbon nanocomposite thin films

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The relationship between the microstructure and the electrical behavior of nickel/carbon nanocomposite (nc-Ni/C) thin films is reported. A particular attention was accorded to the role of the chemical composition and the nature of the amorphous carbon matrix on the electrical behavior of the material. The nc-Ni/C thin films were synthesized using two different cold plasma processes both allowing to finely control the chemical composition, structure and morphology of the films. The first process combines magnetron sputtering of a nickel target and the deposition of hydrogenated carbon by plasma enhanced chemical vapor deposition using methane as a precursor. The second process consists in the co-sputtering of a nickel and a graphite target in pure argon plasma. For the two deposition processes, a similar increase in the electrical conductivity with the Ni content was observed and attributed to the percolation of the Ni nanograins through the carbon matrix. The percolation threshold was evaluated around 41 at.% of Ni for the two deposition processes. For lower Ni concentrations, the microstructural study indicated that the electrical conductivity is governed by the nature of the amorphous carbon phase which is found to be dependent on the deposition process as revealed by μ-Raman spectroscopy.