Nature and role of the film–substrate interface in infinite-layer nickelate thin films

Determine the structural and electronic nature of the film–substrate interface in infinite-layer nickelate thin films and establish how this interface couples to and influences the properties of the thin films, including superconductivity.

Background

Superconductivity in infinite-layer nickelates has thus far been realized only in thin films, while bulk compounds with the same nominal compositions do not exhibit superconductivity. In complex oxide heterostructures, interfaces frequently control key physical properties, motivating the question of whether specific interfacial structures or reconstructions are essential for stabilizing superconductivity in these films.

Previous STEM studies predominantly reported a B-site intermixed (n-type) interface in SrTiO3-based infinite-layer nickelate films and argued for a decoupling between an interfacial two-dimensional electron gas and superconductivity. More recent synthesis reports and the present work demonstrate that chemically sharp interfaces can also be achieved, opening the broader question of what interfacial structures exist across substrates and growth methods, and how these interfaces couple to and affect thin-film properties such as superconductivity.