Epitaxial strain on nickelate <i>R</i>NiO₃ thin films (<i>R </i>= Nd_1-xSr_x, La_1-xNd_x)

We report x-ray diffraction and resistivity measurements on strained nickelate thin films. Following the discovery of superconductivity in a nickelate[1] in an apparently hole-doped RNiO₂ (“infinite-layer”) film (with R ≈ Nd_0.8Sr_0.2), after CaH₂ reduction, subsequent studies stressed the importance of lattice mismatch[2,3]. We discuss the optimization of RNiO₃ (R = Nd_1-xSr_x, La_1-xNd_x) thin films under varying epitaxial strain, induced by choice of substrate or buffer layer lattice constant, including RAlO₃ (3.72-3.78 Å), SrTiO₃ (3.905 Å), and R₂CuO₄ (3.91-3.96 Å). We study the effects of oxygen pressure during growth and film thickness on the electrical resistivity of these lattice-strained films in an effort towards superconducting RNiO₂ thin films.

[1] D. Li et al., Nature 572, 624 (2019).
[2] K. Lee et al., APL Mater 8, 041107 (2020).
[3] D. Li et al, PRL 125, 027001 (2020).