Nickel-based superconductors provide a long-awaited experimental platform to explore possible cuprate-like superconductivity. Despite similar crystal structure and d electron filling, however, superconductivity in nickelates has thus far only been stabilized in thin-film geometry, raising questions about the polar interface between substrate and thin film. Here we conduct a detailed experimental and theoretical study of the prototypical interface between Nd_1−xSr_xNiO₂ and SrTiO₃. Atomic-resolution electron energy loss spectroscopy in the scanning transmission electron microscope reveals the formation of a single intermediate Nd(Ti,Ni)O₃ layer. Density functional theory calculations with a Hubbard U term show how the observed structure alleviates the polar discontinuity. We explore the effects of oxygen occupancy, hole doping and cation structure to disentangle the contributions of each for reducing interface charge density. Resolving the non-trivial interface structure will be instructive for future synthesis of nickelate films on other substrates and in vertical heterostructures.

镍基超导体提供了一个期待已久的实验平台来探索可能的类铜酸盐超导性。然而，尽管具有相似的晶体结构和d电子填充，镍酸盐中的超导性迄今为止仅在薄膜几何结构中得到稳定，这引发了关于基板和薄膜之间极性界面的问题。_{在这里，我们对 Nd 1− x} Sr _x NiO ₂和 SrTiO ₃之间的原型界面进行了详细的实验和理论研究。_{扫描透射电子显微镜中的原子分辨率电子能量损失光谱揭示了单一中间体 Nd(Ti,Ni)O 3}的形成层。使用 Hubbard U项的密度泛函理论计算表明观察到的结构如何减轻极性不连续性。我们探索了氧占有率、空穴掺杂和阳离子结构的影响，以理清每一种对降低界面电荷密度的贡献。解决非平凡的界面结构将对未来在其他基板和垂直异质结构中合成镍酸盐薄膜具有指导意义。