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Influence of cumulenic chains on the vibrational and electronic properties of sp/sp2 amorphous carbon

L. Ravagnan·P. Piseri·M. Bruzzi·S. Miglio·G. Bongiorno·A. Baserga·C. S. Casari·A. Li Bassi·C. Lenardi·Y. Yamaguchi·T. Wakabayashi·C. E. Bottani·P. Milani
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Abstract

We report the production and characterization of a form of amorphous carbon films with sp/sp2 hybridization (atomic fraction of sp hybridized species > 20%) where the predominant sp bonding appears to be (=C=C=)n cumulene. Vibrational and electronic properties have been studied by in situ Raman spectroscopy and electrical conductivity measurements. Cumulenic chains are substantially stable for temperatures lower than 250 K and they influence the electrical transport properties of the sp/sp2 carbon through a self-doping mechanism by pinning the Fermi level closer to one of the mobility gap edges. Upon heating above 250 K the cumulenic species decay to form graphitic nanodomains embedded in the sp2 amorphous matrix thus reducing the activation energy of the material. This is the first example of a pure carbon system where the sp hybridization influences bulk properties.

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L. Ravagnan, P. Piseri, M. Bruzzi, S. Miglio, G. Bongiorno, A. Baserga, C. S. Casari, A. Li Bassi, C. Lenardi, Y. Yamaguchi, T. Wakabayashi, C. E. Bottani, P. Milani. 2007-03-27. Influence of cumulenic chains on the vibrational and electronic properties of sp/sp2 amorphous carbon. https://doi.org/10.1103/physrevlett.98.216103

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