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 LaNiO3 on the band insulator SrTiO3 along the pseudo cubic  direction. While in general the metallic LaNiO3 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 La2Ni2O5 (Ni2+) for a few unit-cell thick films. First-principles layer-resolved calculations of the potential energy across the nominal LaNiO3/SrTiO3 interface confirm that the oxygen vacancies can efficiently reduce the electric field at the interface.
All Science Journal Classification (ASJC) codes