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DPG

Regensburg 2010 – scientific programme

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O: Fachverband Oberflächenphysik

O 26: Oxides and insulators: Clean surfaces

O 26.5: Talk

Tuesday, March 23, 2010, 11:30–11:45, H40

Polarity healing at the local scale: MgO on Au(111) — •Philipp Myrach1, Niklas Nilius1, Stefania Benedetti2, and Hans-Joachim Freund11Fritz-Haber-Institut der MPG, Faradayweg 4-6, D-14195 Berlin, Germany — 2CNR-INFM S3, Via G. Campi 213/a, I-41125 Modena, Italy

Polar MgO films prepared on Au(111) have been investigated with scanning tunnelling microscopy and spectroscopy. The amount of oxide polarity is derived from the MgO band positions and the local surface potential. Both quantities have been measured as a function of the oxide thickness and are good indicators for the strength of the surface dipole. Whereas bi-layer MgO islands exhibit uncompensated polarity, the dipole gradually decreases in thicker films due to surface roughening. The formation of nano-pyramids and pits is hereby identified as the initial step for polarity healing. Above such structural inhomogeneities, the measured surface potential is drastically reduced with respect to flat MgO(111) patches. This effect is reproduced with simple model structures that enable an estimation of the vertical dipole strength.

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