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FABRIZIO MESSINA

Evidence of delocalized excitons in amorphous solids

  • Autori: Messina, F.; Vella, E.; Cannas, M.; Boscaino, R.
  • Anno di pubblicazione: 2010
  • Tipologia: Articolo in rivista (Articolo in rivista)
  • Parole Chiave: Excitons; amorphous materials; vacuum ultraviolet absorption
  • OA Link: http://hdl.handle.net/10447/52704

Abstract

We studied the temperature dependence of the absorption coefficient of amorphous SiO2 in the range from 8 to 17.5 eVobtained by Kramers-Kronig dispersion analysis of reflectivity spectra. We demonstrate the main excitonic resonance at 10.4 eV to feature a close Lorentzian shape redshifting with increasing temperature. This provides a strong evidence of excitons being delocalized notwithstanding the structural disorder intrinsic to amorphous SiO2. Excitons turn out to be coupled to an average phonon mode of 83 meV energy.