Insulating state of ultrathin epitaxial LaNiO{sub 3} thin films detected by hard x-ray photoemission

Journal Article · Mon Aug 15 00:00:00 EDT 2011 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PHYSREVB.84.075104· OSTI ID:21596848

Gray, A X; Kaiser, A M; Fadley, C S ^[1]; Janotti, A; Son, J; LeBeau, J M; Van de Walle, C G; Stemmer, S ^[2]; Ueda, S; Yamashita, Y; Kobayashi, K ^[3]; Sutarto, R ^[4]; Wadati, H; Sawatzky, G A ^[4]

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1. Department of Physics, University of California, Davis, California 95616 (United States)
2. Materials Department, University of California, Santa Barbara, California 93106-5050 (United States)
3. NIMS Beamline Station at SPring-8, National Institute for Materials Science, Hyogo 679-5148 (Japan)
4. Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, V6T 1Z1 (Canada)

In order to understand the influence of strain and film thickness on the electronic structure of thin films of strongly correlated oxides, we have applied hard x-ray photoemission (HXPS) at 6 keV, soft x-ray photoemission (XPS) at 1.5 keV, and transmission electron microscopy to epitaxial LaNiO{sub 3} films deposited on two substrates: LaAlO{sub 3} (compressive strain) and (LaAlO{sub 3}){sub 0.3}(Sr{sub 2}AlTaO{sub 6}){sub 0.7} (tensile strain). Using inelastic attenuation lengths in LaNiO{sub 3} determined from the HXPS data, we have decomposed valence-band spectra into layer-specific contributions. This decomposition is validated by comparing with the results of first-principles calculations using a hybrid functional. The resultant thin-film LaNiO{sub 3} densities of states exhibit significant differences in spectral weights for the thinnest LaNiO{sub 3} films. A gap opening consistent with a metal-to-insulator transition is observed for the thinnest 2.7 nm LaNiO{sub 3} film on an (LaAlO{sub 3}){sub 0.3}(Sr{sub 2}AlTaO{sub 6}){sub 0.7} substrate, with a similar gap opening also being observed in complementary soft x-ray photoemission at 1.5 keV for a thinner 1.4 nm film on an LaAlO{sub 3} substrate. A metal-to-insulator transition in very thin nm-scale films of LaNiO{sub 3} is thus suggested as a general phenomenon.

• OSTI ID: 21596848
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Journal Name: Physical Review. B, Condensed Matter and Materials Physics Journal Issue: 7 Vol. 84; ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALUMINATES
ALUMINIUM COMPOUNDS
CHEMICAL REACTIONS
CRYSTAL GROWTH METHODS
DECOMPOSITION
DIELECTRIC MATERIALS
DIMENSIONS
ELECTROMAGNETIC RADIATION
ELECTRON MICROSCOPY
ELECTRON SPECTROSCOPY
ELECTRONIC STRUCTURE
EMISSION
ENERGY RANGE
EPITAXY
FILMS
HARD X RADIATION
IONIZING RADIATIONS
KEV RANGE
KEV RANGE 01-10
LANTHANUM COMPOUNDS
LAYERS
MATERIALS
MICROSCOPY
NICKEL COMPOUNDS
OXYGEN COMPOUNDS
PHOTOELECTRON SPECTROSCOPY
PHOTOEMISSION
RADIATIONS
RARE EARTH COMPOUNDS
REFRACTORY METAL COMPOUNDS
SECONDARY EMISSION
SOFT X RADIATION
SPECTRA
SPECTROSCOPY
SUBSTRATES
TANTALUM COMPOUNDS
THICKNESS
THIN FILMS
TRANSITION ELEMENT COMPOUNDS
TRANSMISSION ELECTRON MICROSCOPY
X RADIATION
X-RAY PHOTOELECTRON SPECTROSCOPY