Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

1 Publication

Evolution of sp2 networks with substrate temperature in amorphous carbon films: Experiment and theory

Gago, R.; Vinnichenko, M.; Jäger, H. U.; Belov, A. Y.; Jiménez, I.; Huang, N.; Sun, H.; Maitz, M. F.


The evolution of sp2 hybrids in amorphous carbon (a-C) films deposited at different substrate temperatures was studied experimentally and theoretically. The bonding structure of a-C films prepared by filtered cathodic vacuum arc was assessed by the combination of visible Raman spectroscopy, x-ray absorption, and spectroscopic ellipsometry, while a-C structures were generated by molecular-dynamics deposition simulations with the Brenner interatomic potential to determine theoretical sp2 site distributions. The experimental results show a transition from tetrahedral a-C (ta-C) to sp2 -rich structures at ~500 K. The sp2 hybrids are mainly arranged in chains or pairs whereas graphitic structures are only promoted for sp2 fractions above 80%. The theoretical analysis confirms the preferred pairing of isolated sp2 sites in ta-C, the coalescence of sp2 clusters for medium sp2 fractions, and the pronounced formation of rings for sp2 fractions >80%. However, the dominance of sixfold rings is not reproduced theoretically, probably related to the functional form of the interatomic potential used.

Keywords: amorphous carbon; bonding structure; sp2 clustering; molecular dynamics

  • Physical Review B 72(2005)1, 014120-1-014120-9


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