https://doi.org/10.1007/s100530170092
Size and concentration effects in the optical properties of alloyed (Aux Ag1-x)n and core-shell (Nix Ag1-x)n embedded clusters
1
Laboratoire de Spectrométrie Ionique et Moléculaire, CNRS
and Université Lyon I, bâtiment Kastler, 43 boulevard du 11
novembre 1918, 69622 Villeurbanne Cedex, France
2
Département de Physique des Matériaux, CNRS and Université Lyon I,
bâtiment Brillouin, 43 boulevard du 11 novembre 1918, 69622
Villeurbanne Cedex, France
3
Institut de Recherche sur la
Catalyse, CNRS, 2 avenue Albert Einstein, 69626 Villeurbanne
Cedex, France
Corresponding author: a mgaudry@lasim.univ-lyon1.fr
Received:
21
November
2000
Published online: 15 September 2001
Optical properties of mixed clusters (AuxAg
and (NixAg,
produced by laser vaporization and embedded in an alumina matrix,
are reported. The size effects are investigated for different
concentrations (x=0.25, 0.5 and 0.75) in the diameter range 2-4
nm. For alloyed clusters (AuxAg of a given size
an almost linear evolution of the surface plasmon frequency
with the concentration is observed (between those of
pure gold and pure silver clusters). Moreover the blue-shift and
the damping of the resonance with decreasing size is all the more
important as the gold concentration in the particles increases.
Such results are in agreement with theoretical calculations
carried out in the frame of the time-dependent
local-density-approximation (TDLDA) including an inner skin of
ineffective screening and the porosity of the matrix. The
optical response of (NixAg clusters exhibits a
surface plasmon resonance in the same spectral range as the one
observed for pure silver clusters, but considerably damped and
broadened. For a given mean cluster size 3.0 nm, a blue-shift of
the resonance is observed when increasing the nickel concentration
(between x=0.25 and x=0.75). The results are in good
qualitative agreement with classical predictions in the dipolar
approximation, assuming a core-shell geometry.
PACS: 36.40.Vz – Optical properties of clusters / 36.40.-c – Atomic and molecular clusters / 36.40.Gk – Plasma and collective effects in clusters / 73.50.Mx – High-frequency effects; plasma effects
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2001
