Meyer-Neldel rule and Poole-Frenkel effect in chalcogenide glasses

A theoretical model for dc conductivity under high electric field in chalcogenide glasses is developed. This model, of correlated barrier hopping is used to treat both low field conductivity, which obeys Meyer-Neldel rule (MNR), and high field Poole-Frenkel (PF) effect. Both are incorporated in one model because the origin of electronic emission is the same: a deep well in which a polaron is trapped. We show that the characteristic temperatures associated with MNR and PF should be the same, as has been predicted using a rigorous adiabatic polaron hopping model, and previously demonstrated experimentally for fullerene films. We also predict that the extrapolated conductivity prefactors will be the same in the two cases. Experimental evidence from the literature suggests, but does not demonstrate conclusively, that the two predictions are satisfied for chalcogenide glasses. Finally, we interpret the result in terms of the multi-excitation entropy model for MNR. (C) 2013 AIP Publishing LLC.