1 research outputs found
Extinction spectra and electric field enhancement of silver chiral nano-flower shaped nanoparticle; comparison of discrete dipole approximation results with experimental results
In this work, by using the discrete dipole approximation (DDA), we have proposed a model
for the growth of chiral nano-flower shaped sculptured nanoparticle in different sizes and
different symmetries (e.g., 3-, 4- and 5-fold symmetries) and calculated the extinction
spectra for these nanostructures identifying their plasmon peaks. Our results show that
the extinction spectrum obtained experimentally for a chiral nano-flower sculptured thin
film can be the result of the overlap of extinction spectra from an assembly of chiral
nanoflowers forming the deposited thin film. Furthermore, we have investigated carefully
the distribution of electric nearfields and have deduced the physical nature and direction
of oscillations related to different plasmon peaks in the extinction spectra. Results show
the existence of dipolar and quadrupolar oscillations in all structures while for the
4-fold symmetry chiral nano-flower, we have also observed octopolar oscillations. The
calculated results are compared with the experimental results reported by us in [H.
Savaloni, F. Haydari-Nasab, M. Malmir, Appl. Surf. Sci. 257, 9044 (2011)]. In
addition, using the homogenization theory we have shown that the optical response of
metallic structures is affected by a limited thickness of thin film and further increase
of the film thickness has no effect on the optical spectra