Exciton related resonant Raman scattering from CdSe quantum dots in an amorphous GeS2thin film matrix

CdSe quantum dots have been produced in an amorphous GeS 2 thin film matrix by alternating thermal evaporation in vacuum and deposition of several CdSe and GeS 2 layers, with the thickness of the latter being, typically, 20 times larger than that of the former. Raman scattering spectra of these films have been measured over the temperature range 20–293 K using four Ar + laser lines for the excitation and studied with emphasis on the position and intensity of the longitudinal optical phonons of CdSe. A shift of these phonons to lower frequencies is seen which increases with decreasing CdSe layer thickness. On the other hand, resonant Raman effects have been observed as the phonon intensity depends strongly on the nominal CdSe layer thickness, excitation energy and temperature. These results imply formation of high quality CdSe quantum dots in the amorphous GeS 2 thin film matrix and are interpreted in terms of resonant absorption in exciton electronic states of these quantum dots .