Domain-Matching Epitaxy of Ferroelectric Hf_0.5Zr_0.5O₂(111) on La_2/3Sr_1/3MnO₃(001)

Abstract

Epitaxial ferroelectric HfO 2 films are the most suitable to investigate intrinsic properties of the material and for prototyping emerging devices. Ferroelectric Hf 0.5 Zr 0.5 O 2 (111) films have been epitaxially stabilized on La 2/3 Sr 1/3 MnO 3 (001) electrodes. This epitaxy, considering the symmetry dissimilarity and the huge lattice mismatch, is not compatible with conventional mechanisms of epitaxy. To gain insight into the epitaxy mechanism, scanning transmission electron microscopy characterization of the interface was performed, revealing arrays of dislocations with short periodicities. These observed periodicities agree with the expected for domain matching epitaxy, indicating that this unconventional mechanism could be the prevailing factor in the stabilization of ferroelectric Hf 0.5 Zr 0.5 O 2 with (111) orientation in the epitaxial Hf 0.5 Zr 0.5 O 2 (111)/La 2/3 Sr 1/3 MnO 3 (001) heterostructure.

Epitaxial Ferroelectric La-Doped Hf0.5Zr0.5O2 Thin Films

“…This signals very low amount of monoclinic phase in epitaxial La:HZO films, smaller than the observed in equivalent epitaxial undoped HZO films. 15,17,21 Similar reduction of monoclinic phase was observed in polycrystalline La-doped HZO films. 5,7 In summary, XRD confirms that the orthorhombic phase present in the La-doped HZO films has grown epitaxially, but exhibits crystal variants and coexists with a minority monoclinic phase.…”

“…Pole figures (Supporting information S2) confirm epitaxy, with four in-plane crystal variants and same epitaxial relationship as the films without La. 10,15,17,21 Very low intensity peaks barely distinguished at 2=34° in Figure 1a, are likely m-HZO{200} reflections. XRD 2- frames (Supporting information S3) show intense o-HZO(111) spots, while the monoclinic reflections are not detected.…”

An Overview of Ferroelectric Hafnia and Epitaxial Growth

“…Reproduced with permission. [ 60 ] Copyright 2020, American Chemical Society.…”

Critical effect of the bottom electrode on the ferroelectricity of epitaxial Hf0.5Zr0.5O2thin films

“…In contrast, epitaxy of hafnia on perovskite-type oxide electrodes has only been reported on Nb-doped SrTiO 3 (Nb:STO) 10 and La 0.67 Sr 0.33 MnO 3 (LSMO). 2,[11][12][13][14][15][16][17] Epitaxy on other popular perovskite electrodes, such as SrRuO 3 (SRO) or LaNiO 3 (LNO), has not been achieved as far as we know. This is in stark contrast to conventional ferroelectric perovskites, which can be grown epitaxially on a large number of metal and oxide electrodes.…”