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O: Fachverband Oberflächenphysik

O 81: Oxide and Insulator Surfaces: Adsorption II

O 81.1: Talk

Wednesday, March 22, 2017, 16:00–16:15, WIL C107

Adsorption Sites of Individual Metal Atoms on MgO Thin Films Determined by Means of STM — •Edgar Fernandes, Fabio Donati, François Patthey, and Harald Brune — Institute of Physics (IPHYS), Ecole Polytechnique Fédérale de Lausanne (EPFL), Station 3, CH-1015 Lausanne, Switzerland

Single Atoms on ultrathin insulating layers grown on metal surfaces have shown magnetic bistability up to 40 K [F. Donati & al., Science 352, 318 (2016)] and catalytic activity [B. Qiao & al., Nat. Chem. 3, 634 (2011)]. These spectacular properties are determined by the adsorption site that influences the charge state, crystal field, diffusion barrier, and magnetic ground state.

Here, we present a novel experimental method to determine the adsorption site of adatoms on thin MgO(100) layers on Ag(100) with the scanning tunnelling microscope. We determine the lattice constant and orientation of the atomic lattice from atomic resolution images recorded on pristine MgO and identify the sub-lattice imaged as protrusions by means of doping with Ca atoms that substitute and thereby mark the Mg atoms. Ho atoms adsorb on O and bridge sites, with their respective abundance depending on MgO thickness. Co and Fe atoms are on O sites while Au atoms are on bridge sites in contrast to former work [M. Sterrer & al., Phys. Rev. Lett. 98, 206103 (2007)].