Raman studies of optical phonons in vertical cadmium sulfide nanorod arrays

Electrochemically grown cadmium sulfide (CdS) nanorod arrays were studied with Raman spectroscopy. The resonant Raman spectroscopy unravels the enhanced electron-phonon interaction up to the fifth-order multiphonon process in the vertically aligned CdS nanorods after annealing. Resonant Raman scattering at room temperature reveals a surface phonon mode at 253 cm(-1) in the annealed nanorod. This unprecedented observation is accounted for by the lateral confinement in the nanorod whose average aspect ratio is approximately 5. An intersubband transition near 3000 cm(-1) is also observed. These results point to important optoelectronic applications of this material.