Surface phonons in GaAs cylinders

Raman scattering from arrays of GaAs quantum cylinders with radii down to 30 nm has been observed. The spectra show an enhanced TO phonon intensity due to a change in the first-order selection rules. In addition, the smallest cylinders exhibit an extra spectral feature between the TO and LO phonons. The behaviour of this additional peak as a function of the scattering geometry, the cylinder size and the variation of the medium surrounding the cylinders is consistent with a theoretical model of the surface phonons of a cylinder.