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.

Anisotropic Strain‐Mediated Symmetry Engineering and Enhancement of Ferroelectricity in Hf0.5Zr0.5O2/La0.67Sr0.33MnO3 Heterostructures

“…The ϕ angle differences between the 2 spots within each set, defined as α, are several degrees only. These pole figure patterns are similar to the previously reported ones in HZO/LSMO/STO(110) [34,35] but distinct from those measured from the HZO/LSMO(001) films, [25] in which the 12 HZO {-111} diffraction spots are separated by a constant ϕ≈30°. In addition, the pole figure also shows 4 sharp and bright spots at χ≈60°, which can be assigned to the {011} C diffraction spots of the (110) C -oriented substrates or LSMO films (See detailed discussion in Figure S8, Supporting Information).…”

“…Recent publications indeed suggested that the FE polarization of HZO films grown on STO(110) substrates can be enhanced compared to the films grown on STO(001) substrates. [5,34,35] However, the detailed correlation between structural symmetry, FE domain configuration, and ferroelectricity in HZO films under the anisotropic strain remains elusive.…”

Synergetic contributions of chemical doping and epitaxial stress to polarization in ferroelectric HfO2 films

“…This has permitted to study intrinsic endurance [17], switching dynamics [18] and tunneling current contributions [19] in films of high crystalline quality, eventually allowing to better control their properties [20]. In addition, it has been recently shown that the ferroelectric phase can be grown epitaxially on (110) and (111)-oriented SrTiO 3 substrates [21][22][23]36].…”

Ferroelectric Hf0.5Zr0.5O2 films on SrTiO3(111)

“…17 Very recently, the epitaxial growth of orthorhombic Hf 0.5 Zr 0.5 O 2 (HZO) on (110)-oriented LSMO electrodes has also been reported. 18,19 Hf 0.5 Zr 0.5 O 2 (HZO) films or other HfO 2 doped compounds grown on LSMO(001) or LSMO(110) are (111) oriented, while the ferroelectric dipoles are oriented along the [001] direction.…”