Geometry dependence of the phonon modes in CdSe nanorods.

We investigated the geometry dependence of the first-order Raman scattering band of CdSe nanorods experimentally. The band has an asymmetric shape and its position and exact line shape depend on the nanorod diameter and aspect ratio. The band consists of contributions from the longitudinal optical phonon and surface optical phonon modes. While the position of the longitudinal optical phonon related band is purely diameter dependent, the position of the surface optical phonon band depends on the nanorod's aspect ratio. This can be explained by the influence of phonon confinement and a model for surface optical phonons in nanorods.