Surface segregation in Nb-doped BaTiO3 films |
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Authors: | Emmanuel Arveux Sandrine Payan Andreas Klein |
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Institution: | a ICMCB-CNRS, University of Bordeaux, 87 Avenue, Dr. A. Schweitzer, Pessac 33608, France1 b Darmstadt University of Technology, Institute of Materials Science, Petersenstraße 23, D-64287 Darmstadt, Germany1 |
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Abstract: | 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. |
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Keywords: | BaTiO3 and titanates Films PTCR Segregation Surfaces XPS |
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