Berlin 2012 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 14: Adsorption on semiconductors, oxides and insulators II

O 14.5: Vortrag

Montag, 26. März 2012, 17:00–17:15, MA 041

Tuning the growth geometry of metal ad-particles by doping the oxide support — •Niklas Nilius, Xiang Shao, and Hans-Joachim Freund — Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany

Doping is a versatile yet little examined approach to tailor the physical and chemical properties of oxide thin films. By means of scanning tunnelling microscopy, we demonstrate that small amounts of Mo embedded in a CaO matrix change the growth behaviour of gold. While 3D deposits are formed on the pristine oxide, strictly 2D growth prevails on the doped films. The crossover in particle shape is driven by charge transfer processes from the Mo d-states into the Au islands. The negatively charged gold exhibits a larger adhesion and therefore tends to wet the oxide surface. The Mo d-states that are responsible for the electron exchange are identified inside the CaO band gap via tunnelling spectroscopy. The impact of the Mo dopants on the Au growth is suppressed by Li co-doping, which provides traps for the Mo electrons in the CaO film.