Unconventional Stability of Subloop Behavior for Neuromorphic Computing in a Ferroelectric HfO₂

Recent discovery of ferroelectricity in HfO₂ film has attracted not only as a conventional non-volatile memory application but as a neuromorphic analogue device. Multiple intermediate state in ferroelectric switching is one of good candidate for neuromorphic application. Though ferroelectric HfO₂ have CMOS compatibility and ferroelectricity in thin film thickness, due to its large coercive field which can induce uncertainty in multi-level switching process, multilevel switching process research is needed.
In this study, we present the stability of multi-level polarization states in terms of large activation energy and small critical domain volume. We measured switching dynamics and temperature dependence hysteresis of HfO₂ thin films. The characteristic switching time and temperature dependence of hysteresis showed that ferroelectric HfO₂ has large activation energy while the critical ferroelectric domain volume is small compared to the conventional perovskite materials. PFM results showed large domain wall activation energy due to stable small critical volume. Due to small critical size of ferroelectric domain in HfO₂, the enhanced accuracy for the access of multiple states can be used for the analogue ferroelectric HfO₂ memory for the neuromorphic memory application.