Surface segregation in Nb-doped BaTiO₃ films

Emmanuel Arveux (1) , Sandrine Payan (1) , Mario Maglione (1) , Andréas Klein (2)

1 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux
2 Institute of Materials Science

We have used in situ photoemission spectroscopy to investigate Niobium doping in polycristalline BaTiO₃. The valence band maximum position progressively shifts from 2.5 eV for undoped to 2.84 eV for Nb-doped films. Ceramics and single crystal have been investigated for comparison with thin films. Nb-doped BaTiO₃ ceramics and Nb-doped SrTiO₃ single crystal show higher Fermi level position indicating that our doped films are less conducting regarding their bulk parents. This was confirmed by impedance spectroscopy under variable temperature. Large amount of niobium is clearly observable at surface but the amount of dopant is drastically reduced below the near-surface region, as evidenced by depth profile. Therefore, we provide evidence of surface segregation which would explain the contrasted resistivity values reported in literature for such donor-doped films.

Mots clés: BaTiO3; Titanates; Films; PTCR; Segregation; Surfaces; XPS

Domaines: Matériaux

Emmanuel Arveux, Sandrine Payan, Mario Maglione, Andréas Klein. Surface segregation in Nb-doped BaTiO₃ films. Applied Surface Science, 2010, 256 (21), pp.6228-6232. ⟨10.1016/j.apsusc.2010.03.146⟩. ⟨hal-00494479⟩