Preparation and structural analysis of an Ag/NiO strained-layer superlattice

A new superlattice composed of Ag and NiO has been grown epitaxially on MgO(001) substrates by electron beam evaporation in ultrahigh vacuum. The samples were characterized by x-ray diffraction and cross-sectional high resolution transmission electron microscopy. Two component materials have different crystal structures; Ag has face-centered cubic structure and NiO has NaCl-type structure. Lattice mismatch between them is about 2%, and hence the superlattice should be classified as a so-called strained-layer superlattice. As a result of the structural analysis, it is estimated that Ag has face-centered tetragonal structure with the axial ratio c/a of 0.98–0.99 and that NiO has a tetragonally distorted NaCl-type structure with the ratio c/a of 1.04–1.05 in the superlattices, where direction of c-ax is parallel to the growth direction.