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The nature of the metal-insulator transition in thin films and superlattices of LaNiO3 only a few unit cells in thickness remains elusive despite tremendous effort. Quantum confinement and epitaxial strain have been evoked as the mechanisms, although other factors such as growth-induced disorder, cation non-stoichiometry, oxygen vacancies, and substrate–film interface quality may also affect the observable properties of ultrathin films. Here we report results obtained for near-ideal LaNiO3 films with different thicknesses and terminations grown by atomic layer-by-layer laser molecular beam epitaxy on LaAlO3 substrates. We find that the room-temperature metallic behavior persists until the film thickness is reduced to an unprecedentedly small 1.5 unit cells (NiO2 termination). Electronic structure measurements using X-ray absorption spectroscopy and first-principles calculation suggest that oxygen vacancies existing in the films also contribute to the metal-insulator transition.
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Citation / Publisher Attribution
Nature Communications, v. 9, art. 2206
Scholar Commons Citation
Golalikhani, M.; Lei, Q.; Chandrasena, R. U.; Kasaei, L.; Park, H.; Bai, J.; Orgiani, P.; Ciston, J.; Sterbinsky, G. E.; and Arena, Dario, "Nature of the Metal-Insulator Transition in Few-Unit-Cell-Thick LaNiO3 Films" (2018). Physics Faculty Publications. 35.