Evidence of delocalized excitons in amorphous solids.
We studied the temperature dependence of the absorption coefficient of amorphous SiO2 in the range from 8 to 17.5 eV obtained 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.
Messina
Fabrizio
F
Dipartimento di Scienze Fisiche ed Astronomiche, Università degli Studi di Palermo, Via Archirafi 36, I-90123 Palermo, Italy.
Vella
Eleonora
E
Cannas
Marco
M
Boscaino
Roberto
R