Resonant raman scattering of hydrogenated amorphous carbon - evidence for pi-bonded carbon clusters

Resonant Raman spectroscopy has been used to study amorphous hydrogenated carbon films. For films containing both sp2 and sp3 bonded carbon a well-defined high-frequency shift of the main Raman peak is observed with increasing exciting photon energy. This shift is interpreted in terms of scattering from pi-bonde carbon clusters which is resonantly enhanced for incident photon energies approaching the pi-pi resonance. (IAF)