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Controlling the charge state of single Mo dopants in a CaO film

MPS-Authors
http://pubman.mpdl.mpg.de/cone/persons/resource/persons32659

Cui,  Yi
Chemical Physics, Fritz Haber Institute, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons21916

Nilius,  Niklas
Chemical Physics, Fritz Haber Institute, Max Planck Society;
Carl von Ossietzky Universität Oldenburg, Institut für Physik;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons21524

Freund,  Hans-Joachim
Chemical Physics, Fritz Haber Institute, Max Planck Society;

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Fulltext (public)

PhysRevB.88.205421.pdf
(Publisher version), 3MB

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Citation

Cui, Y., Nilius, N., Freund, H.-J., Prada, S., Giordano, L., & Pacchioni, G. (2013). Controlling the charge state of single Mo dopants in a CaO film. Physical Review B, 88(20): 205421. doi:10.1103/PhysRevB.88.205421.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0014-B3AF-8
Abstract
Recent experiments have demonstrated that tiny amounts of Mo impurities give rise to drastic changes in the adsorption characteristic of a wide-gap CaO(001) film. In this scanning tunneling microscopy (STM) and density functional theory paper, we elucidate the underlying mechanism by analyzing the energy levels of the Mo dopants as a function of their oxidation state and depth below the surface. We show that Mo2+ ions in CaO subsurface layers can be reversibly charged and discharged by inducing local band-bending effects with the STM tip. A similar charge switching is not possible for Mo species in a higher oxidation state, as their highest-occupied molecular orbitals are located well below the onset of the CaO conduction band. The easiness of charge switching in Mo2+ ions explains the remarkable chemical properties of doped CaO films, as it renders the material a strong electron donor to adsorbates bound to the oxide surface.