How the electronic structure of correlated oxides evolves with electron and hole doping is a fundamental question of importance for applications. We have studied structural and electronic properties of high-quality MBE-grown doped NiO thin films using a variety of experimental and theoretical methods. We find that both K- and In-doped films at concentrations below 10% exhibit good X-ray diffraction spectra. However, extended X-ray absorption fine structure (XAFS) spectra indicate broadening of the K-O bond length distribution, and an increased bond length, much larger than obtained using theoretical methods. Ab-initio molecular dynamics suggests the XAFS feature is due to K-Ov-K defect structures in the thin film. Spectroscopic ellipsometry shows a smooth but asymmetric evolution of a decreasing optical gap for hole (K) and electron (In) doping, consistent with the behavior of a charge transfer insulator. Analysis shows that the decrease of the optical gap is due to the emergence of an absorption peak below (in energy) the optical gap of un-doped NiO. Calculations using Dynamical Mean Free Theory are in good agreement with the measurements and show the emergence of occupied states just above the valence band edge, and with an asymmetry between hole and electron doping.
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Presenters
Olle Heinonen
Materials Science Division, Argonne National Lab
Argonne National Laboratory
Materials Science Division, Argonne National Laboratory
Argonne Natl Lab
Authors
Friederike Wrobel
Argonne Natl Lab
Max Planck Institute for Solid State Research
Materials Science Division, Argonne National Laboratory, Lemont, IL, 60439, USA
Changhee Sohn
Department of Physics, Ulsan National Institute of Science and Technology
UNIST
Oak Ridge National Lab
Hyowon Park
Physics, University of Illinois-Chicago
Argonne Natl Lab
Univ of Illinois - Chicago
Hyeondeok Shin
Argonne Natl Lab
Computational Science Division, Argonne National Laboratory
Ho Nyung Lee
Oak Ridge National Lab
Materials Science and Technology Division, Oak Ridge National Lab
Oak Ridge National Laboratory
Materials Science and Technology Division, Oak Ridge National Laboratory
George E Sterbinsky
Argonne Natl Lab
Haw-Wen Hsiao
University of Illinois, Urbana-Champaign
materials science and engineering, university of illinois at urbana champaign
Jian-Min Zuo
University of Illinois, Urbana-Champaign
University of Illinois at Urbana-Champaign
materials science and engineering, university of illinois at urbana champaign
Panchapakesan Ganesh
Center for Nanophase Materials and Sciences, Oak Ridge National Laboratory
Oak Ridge National Laboratory
Center for Nanophase Materials Sciences, Oak Ridge National Laboratory
Oak Ridge National Lab
Jaron Krogel
Oak Ridge National Laboratory
Anouar Benali
Computational Science Division, Argonne National Laboratory
Argonne Natl Lab
Paul Kent
Oak Ridge Natl Lab
Oak Ridge National Laboratory
Center for Nanophase Materials and Sciences, Oak Ridge National Laboratory
Oak Ridge National Lab
Olle Heinonen
Materials Science Division, Argonne National Lab
Argonne National Laboratory
Materials Science Division, Argonne National Laboratory
Argonne Natl Lab
Anand Bhattacharya
Materials Science Division, Argonne National Laboratory
