Improved polarization and endurance in ferroelectric Hf 0.5 Zr 0.5 O 2 films on SrTiO 3 (110).

The metastable orthorhombic phase of Hf _0.5 Zr _0.5 O ₂ (HZO) can be stabilized in thin films on La _0.67 Sr _0.33 MnO ₃ (LSMO) buffered (001)-oriented SrTiO ₃ (STO) by intriguing epitaxy that results in (111)-HZO oriented growth and robust ferroelectric properties. Here, we show that the orthorhombic phase can also be epitaxially stabilized on LSMO/STO(110), presenting the same out-of-plane (111) orientation but a different distribution of the in-plane crystalline domains. The remanent polarization of HZO films with a thickness of less than 7 nm on LSMO/STO(110) is 33 μC cm ^-3 , which corresponds to a 50% improvement over equivalent films on LSMO/STO(001). Furthermore, HZO on LSMO/STO(110) presents higher endurance, switchable polarization is still observed up to 4 × 10 ¹⁰ cycles, and retention of more than 10 years. These results demonstrate that tuning the epitaxial growth of ferroelectric HfO ₂ , here using STO(110) substrates, allows the improvement of functional properties of relevance for memory applications.