Fingerprints of Topotactic Hydrogen in Nickelate Superconductors

Si, Liang; Worm, Paul; Held, Karsten

doi:10.3390/cryst12050656

Cited by 15 publications

(5 citation statements)

References 89 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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“…The subsequent reduction for NENO is achieved by in situ reduction using an Al capping method described in ( 8 ). The reduction method minimizes hydrogen intercalation effects ( 15 , 16 ). The schematic reaction diagram is shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

Superconducting Nd _{1−
x} Eu _x NiO ₂ thin films using in situ synthesis

Wei

Zhang

et al. 2023

Sci. Adv.

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We report on superconductivity in Nd 1− x Eu x NiO 2 using Eu as a 4f dopant of the parent NdNiO 2 infinite-layer compound. We use an all–in situ molecular beam epitaxy reduction process to achieve the superconducting phase, providing an alternate method to the ex situ CaH 2 reduction process to induce superconductivity in the infinite-layer nickelates. The Nd 1− x Eu x NiO 2 samples exhibit a step-terrace structure on their surfaces, have a T c onset of 21 K at x = 0.25, and have a large upper critical field that may be related to Eu 4f doping.

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“…Some recent work in currently archived and preprint articles implies that issues with structural defectsincluding layer bucklingcould be inhibiting superconductivity. , Another prevailing hypothesis is that hydrogen incorporation as a byproduct of the hydride reduction technique affects the electronic properties and, therefore, the presence or absence of superconductivity. Some computational studies and experimental data imply that hydrogen incorporation may be necessary for superconductivity, while some show that this incorporation leads to decreased conductivity. − SIMS experiments on superconducting nickelates further give contradictory results regarding the significance of hydrogen in these systems. , Neutron diffraction studies have indicated that there is not a significant amount of hydrogen incorporation in bulk LaNiO 2 powder but have not quantified the upper limit of hydrogen present. The presence of strain in thin films could explain the difference in properties between bulk and film samples as well as any differences in the propensity for hydrogen incorporation.…”

Section: Introductionmentioning

confidence: 99%

Amalgams as Hydrogen-Free Reducing Agents for Topotactic Oxide Deintercalation

Whoriskey,

Bassen,

Wilfong

et al. 2024

Chem. Mater.

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Here, we report the development of a hydrogen-free, topotactic oxygen deintercalation technique using alkali metal aluminum gallium amalgams (A x AlGa, where A = Li, Na, K). These amalgams provide a uniquely tunable system where the choice of alkali metal, its concentration, and the Al:Ga composition alter its reductive properties. We demonstrate the utility of this method in topotactically removing oxygen from bulk and thin film specimens of LnNiO 3 (Ln = La, Nd) to form the infinite layer of nickelate LnNiO 2 (Ln = La, Nd). For example, Na 0.25 AlGa affords bulk LaNiO 2 from LaNiO 3 at 300 °C for 120 h, while the same amalgam at 265 °C for 48 h affords the intermediate La 2 Ni 2 O 5 (LaNiO 2.5 ). Other alterations in time and temperature as well as the choice of alkali metal (A) and its concentration (x) in A x AlGa allow further exploration of the topotactic reduction. Compared to standard techniques based on hydrogen gas or hydrides such as LiH, NaH, and CaH 2 , these amalgams offer an elegant tunability of the reduction potential, enabling control over the rate and degree of oxygen removal without the risk of hydrogen intercalation.

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Fingerprints of Topotactic Hydrogen in Nickelate Superconductors

Cited by 15 publications

References 89 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

Superconducting Nd _{1−
x} Eu _x NiO ₂ thin films using in situ synthesis

Amalgams as Hydrogen-Free Reducing Agents for Topotactic Oxide Deintercalation

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Fingerprints of Topotactic Hydrogen in Nickelate Superconductors

Cited by 15 publications

References 89 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

Superconducting Nd 1− x Eu x NiO 2 thin films using in situ synthesis

Amalgams as Hydrogen-Free Reducing Agents for Topotactic Oxide Deintercalation

Contact Info

Product

Resources

About

Superconducting Nd _{1−
x} Eu _x NiO ₂ thin films using in situ synthesis