QUANTUM CONFINEMENT EFFECTS ON THE OPTICAL PHONONS OF CDTE QUANTUM DOTS

We present Raman-scattering results for CdTe nanocrystals in doped gla sses which clearly show the confinement effects on the phonon spectra as a function of the quantum-dot size. We observed optical phonon mode s, surface phonons and some of their overtone combinations. We show th at the surface-phonon scattering intensity increases as the quantum-do t size decreases. Our results also show a decrease in the electron-pho non coupling as the nanocrystal size is decreased. These confinement e ffects are observed by changing the laser excitation energy, and thus by tuning to resonance with the optical transitions for quantum dots o f different sizes within their broad size distribution in semiconducto r-doped glasses. (C) 1998 Academic Press Limited.