Low-wave-number Raman scattering from ${\mathrm{CdS}}_x{\mathrm{Se}}_{1-x}$ quantum dots embedded in a glass matrix

The Raman scattering on acoustical phonons from ${\mathrm{CdS}}_x{\mathrm{Se}}_{1-x}$ quantum dots in a glass matrix were investigated for in- and off-resonance conditions. By a comparison with a model calculation, the off-resonance scattering showed that the homogeneous broadening mainly contributes to the spectral width of the acoustical vibrational modes. The contribution of inhomogeneous broadening is 30% of the symmetric mode linewidth. For photodarkened samples measured under resonance conditions we showed by comparing the experimental results with the calculations that the ground levels for resonant particle excitation are the trap states filled with the carriers by a photodarkening process. The determined trap energies are in the range of 1–1.5 eV.