Template Engineering of Metal-to-Insulator Transitions in Epitaxial Bilayer Nickelate Thin Films

Abstract

Understanding metal-to-insulator phase transitions in solids has been a keystone not only for discovering novel physical phenomena in condensed matter physics but also for achieving scientific breakthroughs in materials science. In this work, we demonstrate that the transport properties (i.e., resistivity and transition temperature) in the metal-to-insulator transitions of perovskite nickelates are tunable via the epitaxial heterojunctions of LaNiO 3 and NdNiO 3 thin films. A mismatch in the oxygen coordination environment and interfacial octahedral coupling at the oxide heterointerface allows us to realize an exotic phase that is unattainable in the parent compound. With oxygen vacancy formation for strain accommodation, the topmost LaNiO 3 layer in LaNiO 3 /NdNiO 3 bilayer thin films is structurally engineered and it electrically undergoes a metal-to-insulator transition that does not appear in metallic LaNiO 3 . Modification of the NdNiO 3 template layer thickness provides an additional knob for tailoring the tilting angles of corner-connected NiO 6 octahedra and the linked transport characteristics further. Our approaches can be harnessed to tune physical properties in complex oxides and to realize exotic physical phenomena through oxide thin-film heterostructuring.

Strain-Induced Uphill Hydrogen Distribution in Perovskite Oxide Films

“…Additionally, the in situ metal-alkaline hydrogenation method has been extended to perovskite oxides for the first time, presenting similar results to electrochemical gating. In accordance with previous investigations, strain engineering has become a powerful tool in tuning the electric and spintronic properties of TMOs, involving magnetism, Dzyaloshinskii–Moriya interaction, metal-to-insulator transition, and topological spin textures in manganites and nickelates. The control of hydrogen distribution via epitaxial strain, combined with close component-structure–property dependence, provides further insights into designing oxide electronic devices and high-efficiency protonic fuel cells.…”

PERSPECTIVE: Emergent phases in rare earth nickelate heterostructures

“…2(d)-(e)) [77]. LaNiO 3 layers also follow the octahedral rotational pattern of NdNiO 3 in NdNiO 3 /LaNiO 3 superlattices [85]. The interfacial length scale is found to be different in the case of NdNiO 3 /SmNiO 3 SLs, signifying the importance of bulk energetics in artificial quantum materials [86].…”

Perspective—Emergent Phases in Rare Earth Nickelate Heterostructure

“…83 LNO layers also follow the octahedral rotational pattern of NdNiO 3 in NdNiO 3 /LaNiO 3 superlattices. 85 The interfacial length scale is found to be different in the case of NdNiO 3 /SmNiO 3 SLs, signifying the importance of bulk energetics in artificial quantum materials. 86 Emergent Phases of RENiO 3 due to interfacial charge transfer.-The phenomena due to charge transfer across the interface between two different semiconducting layers remain at the forefront of condensed matter physics.…”