Size quantization of acoustic phonons in CuCl nanocrystals

It is shown that the mixed character of spheroidal vibrational modes of semiconductor quantum dots of spherical shape may lead to the appearance of a line in the low-frequency Raman spectra of nanocrystals whose spec-tral position is independent of the average radius of nanocrystals in the sample over a wide range of sizes. This effect is associated with the rapid saturation of the dispersion dependence for transversal acoustic phonons in the bulk semiconductor. The maximum radius of quantum dots at which the line indicated above is observed in the spectrum has been estimated.