Evidence of delocalized excitons in amorphous solids
- Authors: Messina, F; Vella, E; Cannas, M; Boscaino, R
- Publication year: 2010
- Type: Articolo in rivista (Articolo in rivista)
- Key words: 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.