Study of the size effect on the optical mode frequencies of ZnO nanoparticles with nearly uniform size

It was found in ZnO nanoparticles of nearly uniform size that the Raman frequencies of both the polar A1(LO) and nonpolar E2(H) modes do not shift with particle sizes. This observation is in perfect agreement with previous theoretical prediction. The observed result is consistent with the prediction that the size insensitivity of optic vibration frequency in polar nanosemiconductors originates from the Fröhlich interaction, which exists only in polar nanosemiconductors.