Influence of cumulenic chains on the vibrational and electronic properties of s p-s p2 amorphous carbon.
We report the production and characterization of a form of amorphous carbon with s p-s p(2) 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 s p-s p(2) 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 s p(2) amorphous matrix thus reducing the activation energy of the material. This is the first example of a pure carbon system where the s p hybridization influences bulk properties.
Dipartimento di Fisica and CIMAINA, Università di Milano, Via Celoria 16, I-20133 Milan, Italy.
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Ravagnan
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Piseri
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Bruzzi
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Miglio
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Bongiorno
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Baserga
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Casari
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Li Bassi
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Lenardi
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Yamaguchi
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Wakabayashi
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Bottani
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Milani