STABILIZATION OF FERROELECTRICITY IN EPITAXIAL HAFNIA-BASED THIN FILMS

Abstract

Ferroelectric hafnia-based thin films are garnering significant attention for their CMOS compatibility, despite the ferroelectric phase in bulk HfO2-based materials not being energetically favorable. To stabilize the metastable ferroelectric phase of Hf0.5Zr0.5O2 (HZO), we engineered the interface between the HZO layer and a LSMO bottom electrode with different terminations. Our findings indicate that the ferroelectric phase is more stable in HZO/MnO2-terminated LSMO than in HZO/LaSrO-terminated LSMO, due to hole-doping from the MnO2-LSMO to the HZO layer. Furthermore, adjusting the Sr/La ratio in the La1-xSrxMnO3 buffer layer modulates this charge transfer, significantly influencing the ferroelectric stability by affecting oxygen site coordination in HZO. We also introduced a novel HZO/HLO superlattice structure that not only stabilizes the ferroelectric rhombohedral phase in HfO2-based systems but also achieves a record polarization value in these films, underscoring a practical approach to enhance ferroelectricity in hafnia films.