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Donor Characteristics of Transition-Metal-Doped Oxides: Cr-Doped MgO versus Mo-Doped CaO

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http://pubman.mpdl.mpg.de/cone/persons/resource/persons22134

Stavale,  Fernando
Chemical Physics, Fritz Haber Institute, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons22108

Shao,  Xiang
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;

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

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

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Citation

Stavale, F., Shao, X., Nilius, N., Freund, H.-J., Prada, S., Giordano, L., et al. (2012). Donor Characteristics of Transition-Metal-Doped Oxides: Cr-Doped MgO versus Mo-Doped CaO. Journal of the American Chemical Society, 134(28), 11380-11383. doi:10.1021/ja304497n.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0010-224D-D
Abstract
The ability of Mo (Cr) impurities in a CaO (MgO) matrix to act as charge donors to adsorbed gold has been investigated by means of scanning tunneling microscopy and density functional theory. Whereas CaO Mo features a robust donor characteristic, as deduced from a charge-transfer-driven crossover in the Au particles’ geometry in the presence of dopants, MgOCr is electrically inactive. The superior performance of the CaOMo system is explained by the ability of the Mo ions to evolve from a +2 oxidation state in ideal CaO to a +5 state by transferring up to three electrons to the Au adislands. Cr ions in MgO, on the other hand, are stable only in the +2 and +3 charge states and can provide a single electron at best. Since this electron is likely to be captured by cationic vacancies or morphological defects in the real oxide, no charge transfer to Au particles takes place in this case. On the basis of our findings, we have developed general rules on how to optimize the electron donor characteristics of doped oxide materials.