Carrier compensation by excess oxygen atoms in anatase Ti 0.94Nb0.06O2+δ epitaxial thin films

Hiroyuki Nogawa, Taro Hitosugi, Akira Chikamatsu, Shoichiro Nakao, Yasushi Hirose, Toshihiro Shimada, Hiroshi Kumigashira, Masaharu Oshima, Tetsuya Hasegawa

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9 Citations (Scopus)


We report the effect of post-deposition annealing on the electrical transport properties of anatase Ti0.94Nb0.06O2 (TNO) epitaxial thin films. Annealing TNO films in pure oxygen drastically suppressed the carrier density (ne). A high ne of the order of 1021 cm-3 was recovered by successive annealing in pure hydrogen. Core-level X-ray photoemission spectroscopy revealed that Ti and Nb respectively exist as tetravalent and pentavalent ions in fully oxidized samples. The concentration of Nb5+ relative to that of Nb 4+ tends to increase with O2 annealing, suggesting that carriers released by Nb donors are compensated by electron-killing impurity states created by O2 annealing. Based on these findings, we propose that excess oxygen atoms incorporated by O2 annealing occupy interstitial sites and behave as deep acceptor states, which compensate electron carriers generated by Nb doping. Resonant valence-band photoemission spectroscopy directly confirmed the formation of deep acceptor states associated with oxygen annealing.

Original languageEnglish
Pages (from-to)411021-411024
Number of pages4
JournalJapanese Journal of Applied Physics
Issue number4 PART 1
Publication statusPublished - 2010 Apr


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