Optical properties of metallic nanoshell composites: effects of temperature and particle-clustering

1 Department of Physics, National Taiwan University, Taipei 10617, Taiwan, R. O. C. 2 Instrument Technology Research Center, National Applied Research Laboratory, Hsinchu, Taiwan 300, R. O. C. 3 Research Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan, R.O.C. 4 Institute of Optoelectronic Sciences, National Taiwan Ocean University, Keelung, Taiwan, R. O. C Abstract The optical properties of a metallic nanoshell composite are studied theoretically using different effective medium theories with particular focus on the effects of variation in temperature and particle-clustering on these properties. One unique result from our modeling is the persistent manifestation of the single-particle resonances of the individual nanoshells which cannot be found in a composite of solid particles. In addition, we observe the red-shifts in the composite plasmon modes, as well as damping in the dielectric function spectrum as temperature increases. Furthermore, much greater redshift will occur when these nanoshells coalesce to form fractal clusters in the composite – with value in this shift increases with decrease in the fractal dimension or increase in the cluster size. We further calculate the transmission at normal incidence through such composite thin films as a demonstration on how these effects can be experimentally observed. PACS: 78.66Sq, 61.43.Hv, 78.20.Ci, 78.20.Nv