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

Abstract

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.

Authors:
; ;  [1]; ; ; ; ;  [2]; ; ;  [3];  [4]; ;  [4]
  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)
Publication Date:
OSTI Identifier:
21596848
Resource Type:
Journal Article
Journal Name:
Physical Review. B, Condensed Matter and Materials Physics
Additional Journal Information:
Journal Volume: 84; Journal Issue: 7; Other Information: DOI: 10.1103/PhysRevB.84.075104; (c) 2011 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1098-0121
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ALUMINATES; DECOMPOSITION; DIELECTRIC MATERIALS; ELECTRONIC STRUCTURE; EPITAXY; HARD X RADIATION; KEV RANGE 01-10; LANTHANUM COMPOUNDS; LAYERS; NICKEL COMPOUNDS; OXYGEN COMPOUNDS; PHOTOEMISSION; SOFT X RADIATION; SPECTRA; SUBSTRATES; TANTALUM COMPOUNDS; THICKNESS; THIN FILMS; TRANSMISSION ELECTRON MICROSCOPY; X-RAY PHOTOELECTRON SPECTROSCOPY; ALUMINIUM COMPOUNDS; CHEMICAL REACTIONS; CRYSTAL GROWTH METHODS; DIMENSIONS; ELECTROMAGNETIC RADIATION; ELECTRON MICROSCOPY; ELECTRON SPECTROSCOPY; EMISSION; ENERGY RANGE; FILMS; IONIZING RADIATIONS; KEV RANGE; MATERIALS; MICROSCOPY; PHOTOELECTRON SPECTROSCOPY; RADIATIONS; RARE EARTH COMPOUNDS; REFRACTORY METAL COMPOUNDS; SECONDARY EMISSION; SPECTROSCOPY; TRANSITION ELEMENT COMPOUNDS; X RADIATION

Citation Formats

Gray, A X, Kaiser, A M, Fadley, C S, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, Janotti, A, Son, J, LeBeau, J M, Van de Walle, C G, Stemmer, S, Ueda, S, Yamashita, Y, Kobayashi, K, Sutarto, R, Canadian Light Source, University of Saskatchewan, Saskatoon, Saskatchewan, S7N0X4, Wadati, H, and Sawatzky, G A. Insulating state of ultrathin epitaxial LaNiO{sub 3} thin films detected by hard x-ray photoemission. United States: N. p., 2011. Web. doi:10.1103/PHYSREVB.84.075104.
Gray, A X, Kaiser, A M, Fadley, C S, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, Janotti, A, Son, J, LeBeau, J M, Van de Walle, C G, Stemmer, S, Ueda, S, Yamashita, Y, Kobayashi, K, Sutarto, R, Canadian Light Source, University of Saskatchewan, Saskatoon, Saskatchewan, S7N0X4, Wadati, H, & Sawatzky, G A. Insulating state of ultrathin epitaxial LaNiO{sub 3} thin films detected by hard x-ray photoemission. United States. https://doi.org/10.1103/PHYSREVB.84.075104
Gray, A X, Kaiser, A M, Fadley, C S, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, Janotti, A, Son, J, LeBeau, J M, Van de Walle, C G, Stemmer, S, Ueda, S, Yamashita, Y, Kobayashi, K, Sutarto, R, Canadian Light Source, University of Saskatchewan, Saskatoon, Saskatchewan, S7N0X4, Wadati, H, and Sawatzky, G A. Mon . "Insulating state of ultrathin epitaxial LaNiO{sub 3} thin films detected by hard x-ray photoemission". United States. https://doi.org/10.1103/PHYSREVB.84.075104.
@article{osti_21596848,
title = {Insulating state of ultrathin epitaxial LaNiO{sub 3} thin films detected by hard x-ray photoemission},
author = {Gray, A X and Kaiser, A M and Fadley, C S and Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 and Janotti, A and Son, J and LeBeau, J M and Van de Walle, C G and Stemmer, S and Ueda, S and Yamashita, Y and Kobayashi, K and Sutarto, R and Canadian Light Source, University of Saskatchewan, Saskatoon, Saskatchewan, S7N0X4 and Wadati, H and Sawatzky, G A},
abstractNote = {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.},
doi = {10.1103/PHYSREVB.84.075104},
url = {https://www.osti.gov/biblio/21596848}, journal = {Physical Review. B, Condensed Matter and Materials Physics},
issn = {1098-0121},
number = 7,
volume = 84,
place = {United States},
year = {2011},
month = {8}
}