Ferroelectric Hf0.5Zr0.5O2 thin films deposited epitaxially on (110)-oriented SrTiO3

Abstract

Hf0.5Zr0.5O2 (HZO) thin films have been deposited on (110)-oriented SrTiO3 (STO) substrates buffered with epitaxial La0.7Sr0.3MnO3 (LSMO) by pulsed laser deposition. The HZO/LSMO/STO heterostructures show smooth surface and clear interface. It is observed that ferroelectric orthorhombic HZO is enhanced, as non-polar tetragonal HZO is suppressed with the increasing LSMO thickness or decreasing HZO thickness. Completely orthorhombic HZO films are achieved with desired LSMO and HZO thickness. These HZO films are (111)-oriented with in-plane [2¯11] and [01¯1] directions along LSMO [11¯0] and [001], respectively, and exhibit ferroelectric properties at room temperature with an optimized remanent polarization around 26 μC/cm2 without the need of a wake-up process, a long retention up to 104 s and a fatigue endurance up to 109 cycles. Epitaxial HfO2-based films with robust ferroelectric properties deposited on (110)-oriented STO substrates provide additional opportunities to understand the profound effects of orientation, strain, and interface microstructures on the metastable polar phases and ferroelectric properties of HfO2 thin films.