Resonant Raman scattering from ZnTe microcrystals: Evidence for quantum size effects

The size dependence of the resonant Raman scattering from gas-evaporated ZnTe microcrystals has been investigated. Under the 5145-A{} excitation at 80 K, we found that as the size decreases the relative intensity of the 2LO line decreases, while that of the 1LO line increases. This can be well explained by the change in the resonance condition caused by the blue shift of the exciton ground-state energy. The observed temperature dependence of the intensities also supports the blue shift. A semiquantitative treatment of the intensities allowed us to obtain the size dependence of the exciton energy, which is in good agreement with recent results of a variational calculation.