2024/09/19 by Xiaoyue Gao, Gao1, Xiaoyue, Zhuohui Liu +19
Engineering · Materials Science · #Electronic and Structural Properties of Oxides #FOS: Physical sciences #Ferroelectric and Negative Capacitance Devices #Materials Science (cond-mat.mtrl-sci) #Mesoscale and Nanoscale Physics (cond-mat.mes-hall) #Semiconductor materials and devices
paper · pdf · doi:10.48550/arxiv.2409.12434
openalex publication_date 2024/09/19 · openalex created_date 2024/10/25 · openalex updated_date 2026/07/28
Hf0.5Zr0.5O2 (HZO) is a promising candidate for next generation ferroelectric memories and transistors. However, its ferroelectricity origin is still under debate due to the complex of its phase and microstructure in practical samples. In this study, we investigate the atomic structure of substrate-free HZO freestanding film with multislice electron ptychography, for which the ultra-high space resolution (up to ~25 pm) and capability to simultaneously image the cation and oxygen allow us to precisely determine the intrinsic atomic structures of different phases and reveal subtle changes among them. We clarify that the orthorhombic phase is ferroelectric with spontaneous polarization ~34±4 μC/cm2 (corresponding to 56±6 pm in displacement) that is accurately measured through statistical analysis. Significant polarization suppression is observed near the grain boundary, while no distinguishable structural changes are detected near the 180° ferroelectric domain walls. Through the direct oxygen imaging of orthorhombic phase from the [111] zone axis, we quantify a substantial number of oxygen vacancies with a preferential distribution, which influences the polarization direction and strength. These findings provide fundamentals for HZO research, and thus lay a foundation for the design of high-performance ferroelectric devices.