title: Room temperature redox reaction by oxide ion migration at carbon/Gd-doped CeO2heterointerface probed by anin situhard x-ray photoemission and soft x-ray absorption spectroscopies.
abstract: In situhard x-ray photoemission spectroscopy (HX-PES) and soft x-ray absorption spectroscopy (SX-XAS) have been employed to investigate a local redox reaction at the carbon/Gd-doped CeO2(GDC) thin film heterointerface under applied dc bias. In HX-PES, Ce3d and O1s core levels show a parallel chemical shift as large as 3.2 eV, corresponding to the redox window where ionic conductivity is predominant. The window width is equal to the energy gap between donor and acceptor levels of the GDC electrolyte. The Ce M-edge SX-XAS spectra also show a considerable increase of Ce3+satellite peak intensity, corresponding to electrochemical reduction by oxide ion migration. In addition to the reversible redox reaction, two distinct phenomena by the electrochemical transport of oxide ions are observed as an irreversible reduction of the entire oxide film by O2evolution from the GDC film to the gas phase, as well as a vigorous precipitation of oxygen gas at the bottom electrode to lift off the GDC film. Thesein situspectroscopic observations describe well the electrochemical polarization behavior of a metal/GDC/metal capacitor-like two-electrode cell at room temperature.
authors.affiliation: Department of Materials Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan; WPI Center for Materials Nanoarchitechtectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Tsuchiya
authors.affiliation: Department of Materials Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan.
authors.forename: Shogo
authors.initials: S
authors.lastname: Miyoshi
authors.affiliation: NIMS Beamline Station at SPring-8, National Institute for Materials Science, Kouto 1-1-1, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Yamashita
authors.affiliation: NIMS Beamline Station at SPring-8, National Institute for Materials Science, Kouto 1-1-1, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Yoshikawa
authors.affiliation: WPI Center for Materials Nanoarchitechtectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.
authors.forename: Kazuya
authors.initials: K
authors.lastname: Terabe
authors.affiliation: NIMS Beamline Station at SPring-8, National Institute for Materials Science, Kouto 1-1-1, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Kobayashi
authors.affiliation: Department of Materials Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan.
authors.forename: Shu
authors.initials: S
authors.lastname: Yamaguchi
keywords: 10.06; 30.07; 30.09; ReRAM; atom transistor; atomic switch; hard x-ray photoemission spectroscopy; ionics; redox reaction