Negative differential resistivity and positive temperature coefficient of resistivity effect in the diffusion-limited current of ferroelectric thin-film capacitors

We present a model for the leakage current in ferroelectric thin-film capacitors which explains two of the observed phenomena that have escaped satisfactory explanation, i.e. the occurrence of either a plateau or negative differential resistivity at low voltages, and the observation of a positive temperature coefficient of resistivity (PTCR) effect in certain samples in the high-voltage regime. The leakage current is modelled by considering a diffusion-limited current process, which in the high-voltage regime recovers the diffusion-limited Schottky relationship of Simmons already shown to be applicable in these systems.