Origin of the acoustic phonon frequency shifts in semiconducting nanoparticles

The surface and size effects on the acoustic phonon properties of semiconducting nanoparticles, such as ZnO, are studied using the s-d model and a Green's function technique. We have shown that the electron-phonon and anharmonic phonon-phonon interactions play an important role in ZnO nanoparticles and must be taken into account in order to explain the experimental data. Due to surface and size effects on the electron-phonon constants, the acoustic phonon frequency and their damping increase with decreasing of particle size.