Involvement of Unsaturated Switching in the Endurance Cycling of Si‐doped HfO2 Ferroelectric Thin Films

In the past decade, extensive studies on HfO2‐based ferroelectric thin films have been carried out in order to realize their application in high‐density, low‐power, and high‐speed nonvolatile memories. However, understanding the field cycling endurance, which is extremely important for device performance, is still a serious issue. In this work, the frequency and field dependent subcycling behavior is carefully examined. The differences in split‐up effects induced at different subcycling conditions are analyzed by comparing the evolution of polarization‐electric field and transient current hysteresis loops monitored by two subsequent triangular voltage waveforms with different amplitudes. Using the first‐order reversal curves, the evolution of the switching and backswitching field distribution before and after numerous subcycles is characterized. An intuitive model based on the migration of oxygen vacancies from switchable regions to non‐switchable regions and subsequent movement toward top/bottom electrode interface driven by the transient depolarization field is proposed to explain the generation and enhancement of local bias fields. The effect of external field loading history on the evolution of switching/backswitching field distribution for Si:HfO2 ferroelectric thin films can be identified by FORC measurements. The obtained switching density distributions for pristine, woken‐up, and subcycling samples correspond well to the P–E/I–E curves and further reveal the switching behavior of domains within the film.