Enhanced polarization and endurance properties of ZrO₂-based ferroelectric capacitor using HfO₂ interfacial layer

Abstract Recently discovered ferroelectricity in fluorite-structure ZrO₂ thin film has attracted increasing and intense interest due to its lower crystallization temperature and higher content in nature in comparison to hafnium oxide. Here, the effect of HfO₂ interfacial layer on the ferroelectric properties of ZrO₂ thin films is investigated systematically by designing four types of interfacial structures. It is revealed that the ferroelectric orthorhombic phase, remanent polarization, and endurance can be improved in ZrO₂ thin film by inserting both a top- and bottom-HfO₂ interfacial layer. A maximal ferroelectric remanent polarization (2P _r) of 53.4 μC cm⁻² and an optimal endurance performance of 3 × 10⁷ field cycles under frequency of 100 kHz are achieved in Pt/HfO₂/ZrO₂/HfO₂/Pt capacitors, with ferroelectric stacks being crystallized at 450 °C via post-deposition annealing method. X-ray photoelectron spectroscopy analysis confirms that the HfO₂ bottom-layer plays a very important role in the formation of a higher ratio o-phase, thus enhancing the ferroelectricity. These results suggest that designing appropriate interfaces would help achieve excellent ferroelectric properties in ZrO₂ films.