TY - JOUR
T1 - Carrier compensation mechanism in heavily Nb-doped anatase Ti 1-xNbxO2+δ epitaxial thin films
AU - Nogawa, H.
AU - Chikamatsu, A.
AU - Hirose, Y.
AU - Nakao, S.
AU - Kumigashira, H.
AU - Oshima, M.
AU - Hasegawa, T.
N1 - Copyright:
Copyright 2011 Elsevier B.V., All rights reserved.
PY - 2011/9/14
Y1 - 2011/9/14
N2 - 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.
AB - 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.
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U2 - 10.1088/0022-3727/44/36/365404
DO - 10.1088/0022-3727/44/36/365404
M3 - Article
AN - SCOPUS:80052313695
SN - 0022-3727
VL - 44
JO - Journal Physics D: Applied Physics
JF - Journal Physics D: Applied Physics
IS - 36
M1 - 365404
ER -