Optical properties of mixed clusters : comparative study of Ni/Ag and Pt/Ag clusters

E. Cottancin (1) , M. Gaudry , M. Pellarin (1) , J. Lermé (1) , J.R. Huntzinger , J.L. Vialle (1) , M. Broyer (1) , J.L. Rousset , M. Treilleux , P. Mélinon

1 LASIM - Laboratoire de Spectrométrie Ionique et Moléculaire

The optical properties of mixed (Ni_0.5Ag_0.5)_n and Pt/Ag clusters are investigated in the size range 2-5 nm. Low Energy Ion Spectroscopy (LEIS) experiments show that the cluster surface is entirely covered by silver atoms for the two systems. The optical spectra of Ni/Ag clusters exhibit a large Surface Plasmon Resonance (SPR), damped and widened when the cluster size decreases, in agreement with a classical model assuming a core-shell geometry and including the reduction of the conduction electron mean-free path in the silver shell. For Pt/Ag clusters, no SPR emerges in the size range 2-5 nm, although it is predicted within a classical model, a pronounced SPR appearing only for clusters larger than 10 nm in diameter.

E. Cottancin, M. Gaudry, M. Pellarin, J. Lermé, J.R. Huntzinger, et al.. Optical properties of mixed clusters : comparative study of Ni/Ag and Pt/Ag clusters. The European Physical Journal D : Atomic, molecular, optical and plasma physics, 2003, 24, pp.111-114. ⟨10.1140/epjd/e2003-00156-y⟩. ⟨hal-00142448⟩