title: Clustering of impurity atoms in Co-doped anatase TiO(2) thin films probed with soft x-ray fluorescence.
abstract: The electronic structure of Co-doped anatase TiO(2) epitaxial thin films grown at different partial oxygen pressures is investigated using soft x-ray emission spectroscopy. The resonantly excited Co L(2,3) x-ray emission spectra of ferromagnetic Ti(0.96)Co(0.04)O(2) samples for the oxygen-deficient regime show that the ratio of integral intensities for Co L(2) and L(3) emission lines significantly decreases with respect to nonmagnetic samples in the oxygen-rich regime. This is due to L(2)L(3)M(4,5) Coster-Kronig transitions and suggests that ferromagnetic Ti(0.96)Co(0.04)O(2) samples have n-type charge carriers and Co-Co bonds between substitutional and interstitial Co atoms are present while Co-O bonds are dominant in nonmagnetic Ti(0.96)Co(0.04)O(2) samples in the oxygen-rich regime. Electronic structure calculations show that the presence of free charge carriers and Co segregation play a crucial role in strong ferromagnetism at room temperature in Co-doped TiO(2).
authors.affiliation: Department of Physics and Engineering Physics, University of Saskatchewan, 116 Science Place, Saskatoon, SK, S7N 5E2, Canada.
authors.forename: G S
authors.initials: GS
authors.lastname: Chang
authors.forename: E Z
authors.initials: EZ
authors.lastname: Kurmaev
authors.forename: D W
authors.initials: DW
authors.lastname: Boukhvalov
authors.forename: L D
authors.initials: LD
authors.lastname: Finkelstein
authors.forename: D H
authors.initials: DH
authors.lastname: Kim
authors.forename: T-W
authors.initials: TW
authors.lastname: Noh
authors.forename: A
authors.initials: A
authors.lastname: Moewes
authors.forename: T A
authors.initials: TA
authors.lastname: Callcott