title: Reversible Changes in Resistance of Perovskite Nickelate NdNiO3Thin Films Induced by Fluorine Substitution.
abstract: Perovskite nickel oxides are of fundamental as well as technological interest because they show large resistance modulation associated with phase transition as a function of the temperature and chemical composition. Here, the effects of fluorine doping in perovskite nickelate NdNiO3epitaxial thin films are investigated through a low-temperature reaction with polyvinylidene fluoride as the fluorine source. The fluorine content in the fluorinated NdNiO3-xFxfilms is controlled with precision by varying the reaction time. The fully fluorinated film (x ≈ 1) is highly insulating and has a bandgap of 2.1 eV, in contrast to NdNiO3, which exhibits metallic transport properties. Hard X-ray photoelectron and soft X-ray absorption spectroscopies reveal the suppression of the density of states at the Fermi level as well as the reduction of nickel ions (valence state changes from +3 to +2) after fluorination, suggesting that the strong Coulombic repulsion in the Ni 3d orbitals associated with the fluorine substitution drives the metal-to-insulator transition. In addition, the resistivity of the fluorinated films recovers to the original value for NdNiO3after annealing in an oxygen atmosphere. By application of the reversible fluorination process to transition-metal oxides, the search for resistance-switching materials could be accelerated.
authors.affiliation: Department of Chemistry, University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Tomoya
authors.initials: T
authors.lastname: Onozuka
authors.affiliation: Department of Chemistry, University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Akira
authors.identifier: http://orcid.org/0000-0003-0484-6356
authors.initials: A
authors.lastname: Chikamatsu
authors.affiliation: Department of Chemistry, University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Katayama
authors.affiliation: Department of Chemistry, University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.|Kanagawa Academy of Science and Technology (KAST) , 3-2-1 Sakado, Takatsu, Kawasaki, Kanagawa 213-0012, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Hirose
authors.affiliation: Tandem Accelerator Complex, University of Tsukuba , 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8577, Japan.
authors.forename: Isao
authors.initials: I
authors.lastname: Harayama
authors.affiliation: Tandem Accelerator Complex, University of Tsukuba , 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8577, Japan.
authors.forename: Daiichiro
authors.initials: D
authors.lastname: Sekiba
authors.affiliation: Japan Synchrotron Radiation Research Institute (JASRI)/SPring-8 , 1-1-1 Kouto, Mikazuki-cho, Hyogo 679-5198, Japan.
authors.forename: Eiji
authors.initials: E
authors.lastname: Ikenaga
authors.affiliation: Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK) , 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Minohara
authors.affiliation: Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK) , 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kumigashira
authors.affiliation: Department of Chemistry, University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.|Kanagawa Academy of Science and Technology (KAST) , 3-2-1 Sakado, Takatsu, Kawasaki, Kanagawa 213-0012, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Hasegawa
keywords: electronic structures; oxyfluorides; pulsed-laser depositions; resistance modulations; topotactic reactions