Intrinsic Nature of the Excess Electron Distribution at the TiO2 (110) Surface

The deposition of Na on the TiO2(110) surface injects
charge into Ti atoms originating a new electronic state in
the band gap, similar to the well-known Defect State due
to oxygen vacancies. In order to spatially localize the injected
charge, we have performed RESPED (Resonant Photoelectron
Diffraction) measurements of the valence band. The RESPED
from the stoichiometric, albeit Na-doped, surface is identical to
that obtained from the reduced surface. This evidence points to
a general property of TiO2(110), that is the redistribution of the
excess of charge is independent of the injection mechanism.
P. Kruger, et al.

The gap state that appears upon reduction of TiO2 plays a key role in many of titania’s interesting properties but its origin and spatial localization have remained unclear. In the present work, the TiO2(110) surface is reduced in a chemically controlled way by sodium adsorption. By means of resonant photoelectron diffraction, excess electrons are shown to be distributed mainly on subsurface Ti sites strikingly similar to the defective TiO2
(110) surface, while any significant contribution from interstitial Ti ions is discarded.
In agreement with first principles calculations, these findings demonstrate that the distribution of the band gap charge is an intrinsic property of TiO2(110), independent of the way excess electrons areproduced.

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Intrinsic Nature of the Excess Electron Distribution at the TiO2 (110) Surface, P. Kruger, J. Jupille, S. Bourgeois, B. Domenichini, A. Verdini, L. Floreano, and A. Morgante PRL 108, 126803 (2012)
Ultima modifica il Lunedì, 25 Febbraio 2013 13:52