Restoration of polarization in ferroelectric thin films studied with the model of trapping of carriers at interfacial states

A model based on trapping and releasing of free carriers in band gap states located at the interfaces between electrodes and the ferroelectric film is used to explain the restoration of polarization which is sometimes observed. Experimental data on two kinds of polarization restoration in metal/ferroelectric/metal thin film structures are reported. The increase of polarization, which may be observed at the early stage of fatigue test, is attributed to the release of carriers which are trapped in interfacial states at the virgin state, before fatigue test. On the other hand, the previously reported “self recovery effect” is attributed to a competition between the strength of a trapped carrier–ferroelectric dipole interaction and the applied voltage which acts on the dipole orientation.