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

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. The discovery of superconductivity in the infinite-layer nickelates reignites an interest in the nickelates as cuprate analogues. Here, the authors investigate the role of epitaxial strain in the synthesis of the n=3 layered nickelate, Nd4Ni3O8.

Automated summary

This study investigates the influence of epitaxial strain on the synthesis and reduction process of Nd4Ni3O10 films, revealing different structures and transport properties on different substrates. The results provide a pathway for the synthesis of Ndn+1NinO2n+2 thin films and set limits on the ability to strain engineer these compounds via epitaxy.