The role of the spatial distribution of local polarization perturbations in the posistor effect onset

The electrical resistance of polycrystalline ferroelectric semiconductors i s defined by the potential barriers due to the existence of local charged s urface states at crystallite boundaries. The barrier screening depends on t he state of the ferroelectric system and is maximal during spontaneous-pola rization switching. It is shown in this paper that the local perturbation o f the ferroelectric system, resulting from the repolarization and appearing as a domain wall between the regions with different polarization direction s, has a zigzag configuration. The electric field in the vicinity of the zi gzag domain wall is stabilized and coincides with the coercive field, which provides low potential barriers in the ferroelectric phase compared with t he paraelectric phase. The repolarization processes become inefficient in t he potential barrier screening at the transition from the ferroelectric to the paraelectric phase. As a result, a sharp increase in the electrical res istance is observed at the ferroelectric-paraelectric phase transition, cal led the posistor effect. (C) 2000 MAIK "Nauka/Interperiodica".