Less resistance path in inhomogeneous insulating thin films

Altogether, the measurements lead us to consider the grain boundaries as the seat of the electronic localized states which are responsible for the dc charge transfer and for the polarizability of FeF3 thin films. The density of these states increases in the intergranular zones with the degree of crystallization of the samples but, at the same time, the barriers separating two consecutive sites become increasingly uniform. For high temperatures, the electrical charge transfer corresponds to a Poole effect whereas for low temperatures a hopping process is observed.