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Title: Electronic Structure and Band Alignment of LaMnO 3/SrTiO 3 Polar/Nonpolar Heterojunctions

The behavior of polar LaMnO 3 (LMO) thin films deposited epitaxially on nonpolar SrTiO 3(001) (STO) is dictated by both the LMO/STO band alignment and the chemistry of the Mn cation. Using in situ X–ray photoelectron spectroscopy, the valence band offset (VBO) of LMO/STO heterojunctions is directly measured as a function of thickness, and found that the VBO is 2.5 eV for thicker (≥3 u.c.) films. No evidence of a built–in electric field in LMO films of any thickness is found. Measurements of the Mn valence by Mn L–edge X–ray absorption spectroscopy and by spatially resolved electron energy loss spectra in scanning transmission electron microscopy images reveal that Mn 2+ is present at the LMO surface, but not at the LMO/STO interface. These results are corroborated by density functional theory simulations that confirm a VBO of ≈2.5 eV for both ideal and intermixed interfaces. As a result, a model is proposed for the behavior of polar/nonpolar LMO/STO heterojunctions in which the polar catastrophe is alleviated by the formation of oxygen vacancies at the LMO surface.
Authors:
ORCiD logo [1] ; ORCiD logo [1] ; ORCiD logo [1] ; ORCiD logo [1] ; ORCiD logo [2] ; ORCiD logo [3] ; ORCiD logo [4] ; ORCiD logo [5] ; ORCiD logo [1]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  2. Argonne National Lab. (ANL), Argonne, IL (United States)
  3. Auburn Univ., Auburn, AL (United States)
  4. Univ. of California, Berkeley, CA (United States)
  5. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Publication Date:
Grant/Contract Number:
AC02-06CH11357; 10122; DE‐SC‐0012375; DE‐AC02‐06CH11357
Type:
Accepted Manuscript
Journal Name:
Advanced Materials Interfaces
Additional Journal Information:
Journal Volume: 6; Journal Issue: 1; Journal ID: ISSN 2196-7350
Publisher:
Wiley-VCH
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division; National Science Foundation (NSF); USDOE
Country of Publication:
United States
Language:
English
Subject:
LaMnO3; built-in electric field; oxygen vacancies; polar/non-polar heterojunctions
OSTI Identifier:
1494141
Alternate Identifier(s):
OSTI ID: 1482745

Kaspar, Tiffany C., Sushko, Peter V., Spurgeon, Steven R., Bowden, Mark E., Keavney, David J., Comes, Ryan B., Saremi, Sahar, Martin, Lane, and Chambers, Scott A.. Electronic Structure and Band Alignment of LaMnO3/SrTiO3 Polar/Nonpolar Heterojunctions. United States: N. p., Web. doi:10.1002/admi.201801428.
Kaspar, Tiffany C., Sushko, Peter V., Spurgeon, Steven R., Bowden, Mark E., Keavney, David J., Comes, Ryan B., Saremi, Sahar, Martin, Lane, & Chambers, Scott A.. Electronic Structure and Band Alignment of LaMnO3/SrTiO3 Polar/Nonpolar Heterojunctions. United States. doi:10.1002/admi.201801428.
Kaspar, Tiffany C., Sushko, Peter V., Spurgeon, Steven R., Bowden, Mark E., Keavney, David J., Comes, Ryan B., Saremi, Sahar, Martin, Lane, and Chambers, Scott A.. 2018. "Electronic Structure and Band Alignment of LaMnO3/SrTiO3 Polar/Nonpolar Heterojunctions". United States. doi:10.1002/admi.201801428.
@article{osti_1494141,
title = {Electronic Structure and Band Alignment of LaMnO3/SrTiO3 Polar/Nonpolar Heterojunctions},
author = {Kaspar, Tiffany C. and Sushko, Peter V. and Spurgeon, Steven R. and Bowden, Mark E. and Keavney, David J. and Comes, Ryan B. and Saremi, Sahar and Martin, Lane and Chambers, Scott A.},
abstractNote = {The behavior of polar LaMnO3 (LMO) thin films deposited epitaxially on nonpolar SrTiO3(001) (STO) is dictated by both the LMO/STO band alignment and the chemistry of the Mn cation. Using in situ X–ray photoelectron spectroscopy, the valence band offset (VBO) of LMO/STO heterojunctions is directly measured as a function of thickness, and found that the VBO is 2.5 eV for thicker (≥3 u.c.) films. No evidence of a built–in electric field in LMO films of any thickness is found. Measurements of the Mn valence by Mn L–edge X–ray absorption spectroscopy and by spatially resolved electron energy loss spectra in scanning transmission electron microscopy images reveal that Mn2+ is present at the LMO surface, but not at the LMO/STO interface. These results are corroborated by density functional theory simulations that confirm a VBO of ≈2.5 eV for both ideal and intermixed interfaces. As a result, a model is proposed for the behavior of polar/nonpolar LMO/STO heterojunctions in which the polar catastrophe is alleviated by the formation of oxygen vacancies at the LMO surface.},
doi = {10.1002/admi.201801428},
journal = {Advanced Materials Interfaces},
number = 1,
volume = 6,
place = {United States},
year = {2018},
month = {11}
}

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