Observation of a threshold behavior in the optical band gap and thermal diffusivity of Ge-Sb-Se glasses

Abstract

The optical band gap (${\mathit{E}}_{0}$) and thermal diffusivity (\ensuremath{\alpha}) of bulk ${\mathrm{Ge}}_{\mathit{x}}$${\mathrm{Sb}}_{5}$${\mathrm{Se}}_{95\mathrm{\ensuremath{-}}\mathit{x}}$ and ${\mathrm{Ge}}_{\mathit{x}}$${\mathrm{Sb}}_{10}$${\mathrm{Se}}_{90\mathrm{\ensuremath{-}}\mathit{x}}$ glasses have been measured using the photoacoustic technique. The behavior of ${\mathit{E}}_{0}$ and \ensuremath{\alpha} as the mean coordination number 〈r〉 is varied shows a maximum at 〈r〉=2.6. The anomalous behavior at 〈r〉=2.6 is explained on the basis of changes in the network topology due to the formation and development of layered structure in these glasses.