We report the production and characterization of a form of amorphous carbon with sp-sp2 hybridization (atomic fraction of sp hybridized species >or=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 in high vacuum conditions 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.
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. - In: PHYSICAL REVIEW LETTERS. - ISSN 0031-9007. - 98:21(2007), pp. 216103.216103-1-216103.216103-4.
Influence of cumulenic chains on the vibrational and electronic properties of sp-sp2 amorphous carbon
L. RavagnanPrimo
;P. PiseriSecondo
;G. Bongiorno;C. Lenardi;P. MilaniUltimo
2007
Abstract
We report the production and characterization of a form of amorphous carbon with sp-sp2 hybridization (atomic fraction of sp hybridized species >or=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 in high vacuum conditions 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.Pubblicazioni consigliate
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