Dresden 2011 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 14: Clean surfaces: Metals, semiconductors, oxides and insulators I
O 14.1: Vortrag
Montag, 14. März 2011, 15:00–15:15, WIL B122
Change of the surface electronic structure of Au(111) by a monolayer MgO(001) film — •Yi Pan1, Stefania Benedetti2, Niklas Nilius1, and Hans-Joachim Freund1 — 1Fritz-Haber-Institut der MPG, Faradayweg 4-6, 14195 Berlin, Germany — 2CNR, Istituto Nanoscienze, Centro S3, Via G. Campi 213/a, 41100 Modena, Italy
Monolayer films of MgO(001) have been prepared on an Au(111) surface and explored with scanning tunneling microscopy and spectroscopy. The symmetry mismatch between the hexagonal substrate and the squared over-layer results in the formation of a (6x1) super-lattice, as revealed from the distinct stripe pattern observed in the STM. The presence of the oxide film modifies the potential situation at the interface, which induces a substantial up-shift of the Shockley-type surface band on Au(111). The resulting MgO/Au interface band is also characterized by a pseudo-gap at around 0.5 eV that opens at the position of the new Brillouin zone of the enlarged (6x1) cell. In addition, the oxide layer gives rise to a drastic decrease of the Au(111) work function, as deduced from the energy position of field-emission resonance on the bare and MgO-covered surface. The work function drop is explained by an interfacial charge transfer from the oxide film into the electro-negative gold surface.