Dresden 2011 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 7: Surface Dynamics I

O 7.1: Vortrag

Montag, 14. März 2011, 11:15–11:30, WIL C107

Observation of the Surface Segregation of Cu in Pd by Time-Dependend Positron-Annihilation-Induced Auger Electron Spectroscopy — •Christoph Hugenschmidt, Jakob Mayer, and Klaus Schreckenbach — FRM II und Lehrstuhl E21 Physik Department, Technische Universität München, 85747 Garching

Density functional theory calculations predict the surface segregation of Cu in the second atomic layer Pd which was not unambiguously confirmed experimentally so far. We report measurements on Pd surfaces covered with three and six monolayers of Cu using the element selective positron annihilation induced Auger electron spectroscopy (PAES) which is sensitive to the topmost atomic layer. Moreover, time resolved PAES, which was applied for the first time, enables the investigation of the dynamics of surface atoms and hence the observation of the segregation process. The time constant for segregation was experimentally determined to 1.38(0.21)h, and the final segregated configuration was found to be consistent with calculations. Within this work, we demonstrate that time dependent PAES is a novel element selective technique applicable for numerous systems for the investigation of e.g. heterogeneous catalysis, corrosion or surface alloying.