Substrate-engineered ferroelectric phase stabilization and polarization switching dynamics in La doped HfO2

Abstract

HfO2-based ferroelectric films are promising candidates for emerging non-volatile memory technologies. As a metastable ferroelectric phase, multiple methods, like doping, defect control, are employed to stabilize the polar Orthorhombic phase within HfO2-based films and regulate the switching performances of their corresponding devices. However, the strain state of bottom electrodes, induced by varying substrates, also plays a crucial role in determining the structural stability and polarization characteristics of ferroelectric layers. Therefore, a systematic evaluation of substrate-related effects on both electrode buffers and ferroelectric layers is essential. This study investigates the substrate-engineered stabilization of the ferroelectric phase and polarization switching dynamics in La-doped HfO2 thin films grown on epitaxial La0.67Sr0.33MnO3 bottom electrodes. And it reveals that the enhanced tensile strain in a La0.67Sr0.33MnO3 buffer facilitates stabilization of the ferroelectric phase in HfO2-based films. However, progressively increasing tensile strain degrades the conductivity of La0.67Sr0.33MnO3 electrodes and exacerbates interfacial defects, ultimately deteriorating the response speed and read/write performance of ferroelectric devices. This research provides a novel perspective on the analysis of ferroelectric performances via bottom electrode strain engineering, contributing fundamental insights for device assessment and practical guidelines for optimized design of ferroelectric devices.