Carrier compensation mechanism in heavily Nb-doped anatase Ti 1-xNbxO2+δ epitaxial thin films

H. Nogawa, A. Chikamatsu, Y. Hirose, S. Nakao, H. Kumigashira, M. Oshima, T. Hasegawa

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17 Citations (Scopus)


We investigated the electronic structures of anatase Ti 1-xNbxO2+δ (TNO) thin films as a function of Nb concentration x using photoemission spectroscopy (PES) measurements to elucidate the origin of the abrupt decrease in carrier activation in heavily Nb-doped regime. The existing intensity ratio of Nb5+ evaluated from Nb 3d core-level PES spectra maintained a constant value of ∼0.8 at x = 0.06-0.3, implying that electron carriers generated by Nb doping are compensated by p-type defects. Ti 2p-3d and O1s-2p resonant PES measurements of x = 0.06-0.3 films revealed that the in-gap states positioned ∼1 eV below the Fermi level (EF) have a mixed character of Ti 3d and O 2p orbitals, whereas the states at EF mainly have a Ti 3d nature. We proposed a carrier compensation mechanism that interstitial oxygen atoms strongly combined with surrounding Nb atoms kill conduction electrons in heavily Nb-doped anatase TiO2.

Original languageEnglish
Article number365404
JournalJournal of Physics D: Applied Physics
Issue number36
Publication statusPublished - 2011 Sept 14
Externally publishedYes

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Acoustics and Ultrasonics
  • Surfaces, Coatings and Films


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