Super-lattice effects in ordered core-shell nanorod arrays detected by Raman spectroscopy

We studied the optical phonon excitations (LO) of ordered arrays of dot/ rod core-shell CdSe/ CdS nanorods by Raman spectroscopy. Upon deposition on planar substrates the nanorods formed super-lattice structures via side-by side assembly into tracks over some microns of length. COMSOL Multiphysics software has been used to calculate the magnitude of the electric field generated by the interaction of an incident electromagnetic wave with an array of CdSe/CdS nanorods. In particular two configurations were considered: i) localized charges in the nanorods; ii) no localized charges in the nanorods. To this purpose a 2D model has been implemented and simulations have been performed for both polarizations of the incident electromagnetic field. Multiphysical characteristics of COMSOL have been exploited as the simulation relied on a two-steps process. First, localized charges have been set-up near the CdSe cores to mimic the promotions of electrons and an electrostatic simulation was launched. Second, the calculated electric displacement field was used to modify materials conductivity and thus the interaction with the impinging electromagnetic wave.