Solid state reduction of nickelate thin films

Wei, Wenzheng; Shin, Kidae; Hong, Hawoong; Shin, Yeongjae; Thind, Arashdeep Singh; Yang, Yingjie; Klie, Robert F.; Walker, Frederick J.; Ahn, Charles

doi:10.1103/physrevmaterials.7.013802

Cited by 17 publications

(21 citation statements)

References 45 publications

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“…As a result, decomposition has been observed in reduced infinite-layer thin films 37,[71][72][73] ; the precise identification of the decomposition products is, however, difficult in thin films in part due to the small film volume. An additional challenge associated with metal hydride reductions is the possibility of hydrogen incorporation in the lattice, an effect which has been proposed as a reason for the absence of superconductivity in some films 70,74,75 promising alternative to metal hydride reductions 76 . Thus to minimize the formation of decomposition products and potential hydrogen intercalation during metal hydride reductions, careful optimization of reduction duration and temperature is essential.…”

Section: Mbe Synthesis Of Ruddlesden-popper Nickelatesmentioning

confidence: 99%

Limits to the strain engineering of layered square-planar nickelate thin films

et al. 2023

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The layered square-planar nickelates, Ndn+1NinO2n+2, are an appealing system to tune the electronic properties of square-planar nickelates via dimensionality; indeed, superconductivity was recently observed in Nd6Ni5O12 thin films. Here, we investigate the role of epitaxial strain in the competing requirements for the synthesis of the n = 3 Ruddlesden-Popper compound, Nd4Ni3O10, and subsequent reduction to the square-planar phase, Nd4Ni3O8. We synthesize our highest quality Nd4Ni3O10 films under compressive strain on LaAlO3 (001), while Nd4Ni3O10 on NdGaO3 (110) exhibits tensile strain-induced rock salt faults but retains bulk-like transport properties. A high density of extended defects forms in Nd4Ni3O10 on SrTiO3 (001). Films reduced on LaAlO3 become insulating and form compressive strain-induced c-axis canting defects, while Nd4Ni3O8 films on NdGaO3 are metallic. This work provides a pathway to the synthesis of Ndn+1NinO2n+2 thin films and sets limits on the ability to strain engineer these compounds via epitaxy.

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Section: Mbe Synthesis Of Ruddlesden-popper Nickelatesmentioning

confidence: 99%

Limits to the strain engineering of layered square-planar nickelate thin films

et al. 2023

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“…Such a possible tetragonal symmetry is also confirmed by the observation along 45° projection as shown in Figure i,j. The apical oxygen removal indicatively reduces the o-o-p parameter, as is the case for infinite-layer nickelates, where the complete removal of apical oxygen results in an o-o-p parameter of ≈3.30 Å. ,− The observed o-o-p parameter of 3.63 Å in Sm 9 Ni 9 O 22 is thus associated with these oxygen deficiencies.…”

Section: Resultsmentioning

confidence: 91%

“…The chemical dynamics behind the selective stabilization of these phases is still not understood. Possibly, this A 9 B 9 O 22 phase, that we report here, might have been present along the samples that reported the A 3 B 3 O 7 , , or it might have been misinterpreted as that.…”

Section: Discussionmentioning

confidence: 86%

Valence-Ordered Thin-Film Nickelate with Tri-component Nickel Coordination Prepared by Topochemical Reduction

Raji,

Dong,

Porée

et al. 2024

ACS Nano

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The metal-hydride-based "topochemical reduction" process has produced several thermodynamically unstable phases across various transition metal oxide series with unusual crystal structures and nontrivial ground states. Here, by such an oxygen (de-)intercalation method we synthesis a samarium nickelate with ordered nickel valences associated with tricomponent coordination configurations. This structure, with a formula of Sm 9 Ni 9 O 22 as revealed by four-dimensional scanning transmission electron microscopy (4D-STEM), emerges from the intricate planes of {303} pc ordered apical oxygen vacancies. X-ray spectroscopy measurements and ab initio calculations show the coexistence of square planar, pyramidal, and octahedral Ni sites with mono-, bi-, and tri-valences. It leads to an intense orbital polarization, charge-ordering, and a ground state with a strong electron localization marked by the disappearance of ligand−hole configuration at low temperature. This nickelate compound provides another example of previously inaccessible materials enabled by topotactic transformations and presents an interesting platform where mixed Ni valence can give rise to exotic phenomena.

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“…The Al film is highly reducing to the underlying nickelate material, driving the valence from the stoichiometric perovskite or RP phase to the reduced phases. In the case of RP films with the initial stoichiometry of Nd 6 Ni 5 O 16 , the reduced films did not exhibit superconductivity in the Nd 6 Ni 5 O 12 phase [122], contrary to the reports for MBE-grown films synthesized via CaH 2 reduction [118]. Interestingly, infinite-layer Nd 1−x Eu x NiO 2 films synthesized in this manner were superconducting and exhibit T c values of 21 K for x = 0.25 [121], higher than any previous reports for MBE or PLD-grown films.…”

Section: Nickelates: Isoelectronic Analogue To the Cupratesmentioning

confidence: 91%

“…Recent studies have particularly focused on reduction of nickelate films without CaH 2 using metallic aluminum capping layers [121,122]. In these works, the authors grew epitaxial nickelate films followed by Al capping layers without air exposure.…”

Section: Nickelates: Isoelectronic Analogue To the Cupratesmentioning

confidence: 99%

Advances in complex oxide quantum materials through new approaches to molecular beam epitaxy

Rimal,

Comes

2024

J. Phys. D: Appl. Phys.

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Molecular beam epitaxy (MBE), a workhorse of the semiconductor industry, has progressed rapidly in the last few decades in the development of novel materials. Recent developments in condensed matter and materials physics have seen the rise of many novel quantum materials that require ultra-clean and high-quality samples for fundamental studies and applications. Novel oxide-based quantum materials synthesized using MBE have advanced the development of the field and materials. In this review, we discuss the recent progress in new MBE techniques that have enabled synthesis of complex oxides that exhibit "quantum" phenomena, including superconductivity and topological electronic states. We show how these techniques have produced breakthroughs in the synthesis of 4d and 5d oxide films and heterostructures that are of particular interest as quantum materials. These new techniques in MBE offer a bright future for the synthesis of ultra-high quality oxide quantum materials.

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Solid state reduction of nickelate thin films

Cited by 17 publications

References 45 publications

Limits to the strain engineering of layered square-planar nickelate thin films

Limits to the strain engineering of layered square-planar nickelate thin films

Valence-Ordered Thin-Film Nickelate with Tri-component Nickel Coordination Prepared by Topochemical Reduction

Advances in complex oxide quantum materials through new approaches to molecular beam epitaxy

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