The spontaneous ferroelectric polarization that occurs in ferroelectric materials such as the perovskite structure PZT or fluorite structure hafnium oxide can be used to store information. The memory effect is used in three different device concepts, FTJ, FeCAP, and FeFET. Moreover, the rich switching dynamics such as gradual analogue switching, accumulative switching or digital switching can be used in different applications. The gradual analogue switching is interesting for the application in synaptic weighting elements especially when using FTJ or FeFET devices. Moreover, the accumulative switching properties in small scaled FeFETs is a very interesting feature for the realization of the integration part of LIF-neurons. Finally, deterministic and digital switching is used to realize pure digital single-level or even multi-level memory or content-addressable-memory cells (CAM). These can be further utilized in neuromorphic systems, for example, as routing tables in address-event-representation (AER) based spiking neural networks,[85]where point-to-point connections between different cells are emulated by sending spikes as identifying addresses via a digital bus system.
