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Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
Published on: June 7, 2018
Evidence of delocalized excitons in amorphous solids
Fabrizio Messina1, Eleonora Vella, Marco Cannas
1Dipartimento di Scienze Fisiche ed Astronomiche, Università degli Studi di Palermo, Via Archirafi 36, I-90123 Palermo, Italy.
Abstract:
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.
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