Anomalous polarization-switching phenomena and noteworthy pyroelectricity in ferroelectric Hf_0.5Zr_0.5O₂ polycrystalline films

Hafnia-based oxide thin films exhibit unconventional robust ferroelectricity at the nanoscale, paving the way for advancements in next-generation nanoelectronics. However, the stability and dynamics of ferroelectric polarization in hafnia-based oxides films, particularly at the nanoscale, warrant further exploration. In this study, we delve into the factors influencing the formation of the ferroelectric phase. Our findings illuminate that the confinement effect of the capped layer enhances the stabilization of the metastable orthorhombic phase, thereby bolstering its ferroelectricity and endurance. Furthermore, we identify an unprecedented polarization-switching behavior in HfO₂-based ferroelectric films, characterized by a decrease in the remanent polarization and an increase in the coercive field as the temperature drops. This peculiar phenomenon can be ascribed to the reduction in the long-range interaction of polarization dipoles upon cooling, as evidenced by the dielectric spectrum. The diminished long-range interaction results in the emergence of nanodomains and a re-entrant relaxer behavior, offering novel insights into the origin of ferroelectricity and the stability of ferroelectric polarization in hafnia-based thin films. Given the commendable compatibility of Hf_0.5Zr_0.5O₂ films with Si substrates and a pyroelectric coefficient of −62.1 μC/m²·K, they emerge as a prime candidate for sensor device applications.