Aspects of the synthesis of thin film superconducting infinite-layer nickelates

Abstract

The recent observation of superconductivity in Nd0.8Sr0.2NiO2 calls for further investigation and optimization of the synthesis of this metastable infinite-layer nickelate structure. Here, we present our current understanding of important aspects of the growth of the parent perovskite compound via pulsed laser deposition on SrTiO3 (001) substrates, and the subsequent topotactic reduction.We find that to achieve single-crystalline, single-phase superconducting Nd0.8Sr0.2NiO2, it is essential that the precursor perovskite Nd0.8Sr0.2NiO3 thin film is stabilized with high crystallinity and no impurity phases; in particular, a Ruddlesden-Popper-type secondary phase is often observed.We have further investigated the evolution of the soft-chemistry topotactic reduction conditions to realize full transformation to the infinite-layer structure with no film decomposition or formation of other phases. We find that capping the nickelate film with a subsequent SrTiO3 layer provides an epitaxial template to the top region of the nickelate film, much like the substrate. Thus, for currently optimized growth conditions, we can stabilize superconducting single-phase Nd0.8Sr0.2NiO2 (001) epitaxial thin films up to ~ 10 nm. ________________________ a kyuho@stanford.edu b denverli@stanford.edu

Nickelate superconductors—a renaissance of the one-band Hubbard model

“…Most noteworthy Sr 0.2 Nd 0.8 NiO 2 which was found to be superconducting in experiment 11 is close to optimal doping n d x 2 Ày 2 ¼ 0:85 or Sr 0.16 Nd 0.84 NiO 2 . Our results call for a more thorough investigation of superconductivity in nickelates around this doping, which is quite challenging experimentally [12][13][14] .…”

Multiorbital Processes Rule the Nd1−xSrxNiO2Lechermann1 2020Phys. Rev. X10310880View full textAdd to dashboardCite

“…The discovery of superconductivity in Sr-doped thin films of infinite-layer (IL) NdNiO 2 with a T c in the 10-K range marks a further milestone in the investigation of transition-metal oxides [1]. Recent experimental works provide details on the thin-film growth on a SrTiO 3 substrate and, moreover, yield a phase diagram with doping [2][3][4]. There, the superconducting region is placed in the range 0.125 ≲ x ≲ 0.25 within the Nd 1−x Sr x NiO 2 system.…”

Probing surfaces and interfaces in complex oxide films via in situ X-ray photoelectron spectroscopy

“…This provides a good example of the importance of considering chemical differences between the film surface and bulk when interpreting results of other physical property measurements. Recently, an infinite-layer (Nd,Sr)NiO 2 nickelate heterostructure has demonstrated superconductivity for the first time [56,57,58,59]. Future studies of superconducting nickelates using X-ray spectroscopy will hopefully provide further insights into the very exciting initial results.…”