Dresden 2014 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
O: Fachverband Oberflächenphysik
O 58: Oxide and Insulator Surfaces II
O 58.1: Vortrag
Mittwoch, 2. April 2014, 16:00–16:15, PHY C 213
Oxygen activation on Mo-doped CaO films — Yi Cui1, •Niklas Nilius1,2, and Hans-Joachim Freund1 — 1Fritz-Haber-Institut, Faradayweg 4-6, D-14195 Berlin, Germany — 2Carl von Ossietzky Universität, Institut für Physik, D-26111 Oldenburg, Germany
Already trace amounts of aliovalent dopants can be sufficient to change the physical and chemical properties of oxide materials. Using low temperature STM, we have shown that Mo ions in a crystalline CaO film of 8 eV band gap act as charge donors and may provide up to three extra electrons to suitable adsorbates. The relevant species for charge exchange are Mo2+ ions sitting in Ca substitutional sites in near surface layers of the oxide.(1) Their charge state is probed and manipulated with the STM tip. The results were found to be in agreement with DFT calculations of the Mo 4d states split in the crystal field of the CaO lattice. Charge transfer from the Mo donors is identified both into metallic (Au) and molecular adsorbates (O2) bound to the surface.(2) In the latter case, formation of superoxo-species is revealed, characterized by a large affinity for dissociation. Additional means to modify electronic and optical properties of oxides via doping are envisioned.
1. Cui, Nilius, Freund, Prada, Giordano, Pacchioni, Phys. Rev. B 88 (2013) 205421.
2. Cui, Nilius, Shao, Baldowski, Sauer, Freund, Angew. Chem. Int. Ed. 52 (2013) 11385.