Effects of Surface Termination and Layer Thickness on Electronic Structures of LaNiO <sub/>3</sub> Thin Films

摘要： We investigate the e?ects of surface termination and layer thickness on the electronic structures of LaNiO3 thin ?lms on SrTiO3 substrate using ?rst-principles density-functional theory calculations. The NiO2-terminated ?lm with one unit cell thickness shows a pseudogap at the Fermi level owing to the negative charge transfer energy, whereas the 1.5-unit-cell-thick LaO-terminated ?lm exhibits an insulating gap of 1.0 eV as a result of the large exchange splitting. The metallic state is quickly restored for thicker ?lms with either NiO2 or LaO termination, resembling that in bulk nickelate. Our results indicate the strong dependence of the electronic properties on layer thickness and provide insightful information into the metal–insulator transition in LaNiO3 thin ?lms.