EFFECTS OF RESONANCE ON LOW-FREQUENCY RAMAN-SCATTERING FROM SEMICONDUCTOR NANOCRYSTALS

An investigation of Raman scattering in CdSe nanocrystals embedded in oxide glass matrix under resonant excitation has been accomplished. Fi rst we observe the dependence of both the longitudinal optical phonon and the low frequency scattering energies with the excitation waveleng th which is explained in terms of size selective excitation. A peculia r attention is given to the behaviour of low-frequency spectra and sel ection rules due to resonance effects are reported. Most of the first harmonics of the different predicted vibration modes have been observe d and a qualitative attempt has been made to link the observed modes w ith the excited electronic levels.