Dielectric behaviour of nitrogen doped perovskite SrTiO3−δNδ films

Abstract

Technologically important high-permittivity dielectrics are often achieved using cationic engineering of ABO₃-type perovskite para(ferro)electrics. Here, we experimentally and theoretically explore the potential of less conventional anionic engineering in ABO₃ dielectrics. We demonstrate that in an archetypal representative SrTiO₃, nitrogen substitution can occur on two distinct oxygen atomic sites, reduce crystal symmetry, and lead to significant changes in the patterns and frequencies of lattice vibrations. These phonon transformations diminish permittivity, whereas contribution from nitrogen-induced nanoregions can raise it. The effects of nitrogen are found to be especially strong in epitaxial films. We anticipate that the revealed phenomena may be relevant for a broad class of high-permittivity perovskite oxides.