Regensburg 2010 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 26: Poster Session

MM 26.35: Poster

Tuesday, March 23, 2010, 14:45–16:30, Poster C

Near Surface Lattice Relaxation in Transition Metal Nanoparticles — •Björn Bieniek, Darius Pohl, Ludwig Schultz, and Bernd Rellinghaus — IFW Dresden, Helmholtzstraße 20, D-01069 Dresden, Germany

The near-surface lattice relaxation of transition metal alloy nanoparticles is investigated. Recent results show that CuAu and FePt particles show a pronounced lattice expansion of about 10% at their surface. Here, MD simulations indicate that the segregation of the heavier elements (Au, Pt) leads to the experimentally observed lattice expansion. However, surface-sensitive XAS and PES have revealed the presence of oxygen in the surface layers of FePt particles which could in turn contribute to and/or cause the expansion of the lattice. To investigate the influence of oxygen on the near-surface lattice expansion, FeNi particles are investigated. FeNi is much more susceptible to oxidation than CuAu and FePt. In contrast to the latter, abberation-corrected high resolution TEM on FeNi particles reveals that metallic particle cores are surrounded by crystalline oxide shells. Almost no lattice relaxation is observed in the metallic core, and the interface between the metal and the oxide is atomically sharp. Both, defects due to the lattice mismatch at the interface and a significant lattice relaxation are only observed in the oxide shell. MD Simulations and HRTEM contrast simulations of FeNi nanoparticles are presented to confirm the experimental results.