The interfacial atomic structure of a metallic ${\mathrm{LaNiO}}_3/{\mathrm{LaAlO}}_3$ superlattice grown on a ${\mathrm{LaSrAlO}}_4$ substrate was investigated using a combination of atomically resolved electron energy loss spectroscopy (EELS) at the Al $K$, Al $L_{2,3}$, Sr $L_{2,3}$, Ni $L_{2,3}$, La $M_{4,5}$, and O $K$ edges as well as hybridization mapping of selected features of the O $K$-edge fine structure. We observe an additional ${\mathrm{La}}_{1-x}{\mathrm{Sr}}_x{\mathrm{Al}}_{1-y}{\mathrm{Ni}}_y{\mathrm{O}}_3$ layer at the substrate-superlattice interface, possibly linked to diffusion of Al and Sr into the growing film or a surface reconstruction due to Sr segregation. The roughness of the ${\mathrm{LaNiO}}_3/{\mathrm{LaAlO}}_3$ interfaces is found to be on average around one pseudocubic unit cell. The O $K$-edge EELS spectra revealed reduced spectral weight of the prepeak derived from Ni-O hybridized states in the ${\mathrm{LaNiO}}_3$ layers. We rule out oxygen nonstoichiometry of the ${\mathrm{LaNiO}}_3$ layers and discuss changes in the Ni-O hybridization due to heterostructuring as possible origin.

• Received 2 July 2014
• Revised 4 November 2014

DOI:https://doi.org/10.1103/PhysRevB.90.195140