Polarity compensation in ultra-thin films of complex oxides: The case of a perovskite nickelate

• Published in: Scientific reports Vol. 4; no. 1; p. 6819
• Main Authors: Middey, S., Rivero, P., Meyers, D., Kareev, M., Liu, X., Cao, Y., Freeland, J. W., Barraza-Lopez, S., Chakhalian, J.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 29.10.2014; Nature Publishing Group
• Subjects: 639/766/119/544; 639/766/119/995; Electron diffraction; electronic properties and materials; Energy; Humanities and Social Sciences; interfaces and thin films; MATERIALS SCIENCE; multidisciplinary; Oxides; Polarity; Potential energy; Science; Spectroscopy; surfaces; surfaces, interfaces and thin films; Thin films; X-ray diffraction; X-ray spectroscopy; X-rays
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/srep06819

We address the fundamental issue of growth of perovskite ultra-thin films under the condition of a strong polar mismatch at the heterointerface exemplified by the growth of a correlated metal LaNiO 3 on the band insulator SrTiO 3 along the pseudo cubic [111] direction. While in general the metallic LaNiO 3 film can effectively screen this polarity mismatch, we establish that in the ultra-thin limit, films are insulating in nature and require additional chemical and structural reconstruction to compensate for such mismatch. A combination of in-situ reflection high-energy electron diffraction recorded during the growth, X-ray diffraction and synchrotron based resonant X-ray spectroscopy reveal the formation of a chemical phase La 2 Ni 2 O 5 (Ni 2+ ) for a few unit-cell thick films. First-principles layer-resolved calculations of the potential energy across the nominal LaNiO 3 /SrTiO 3 interface confirm that the oxygen vacancies can efficiently reduce the electric field at the interface.