Both confined acoustic and optic phonons were detected in tin nanoparticles
embedded in a SiOx thin film, using inelastic light scattering, for differ
ent values of the particle size. The eigenfrequencies of the acoustic modes
are in agreement with theoretical calculations for the free vibrations of
an elastic sphere. By increasing the temperature, clear effects of particle
melting on the optical and acoustic modes were observed, together with the
detection of a coupling with a strong central peak. The observation of mel
ting, and surface melting, through direct investigation of the nanoparticle
acoustic vibrational eigenmodes represents a novel and relevant feature of
this work.