Melting in metallic Sn nanoparticles studied by surface Brillouin scattering and synchrotron-x-ray diffraction

Brillouin scattering of light off surface acoustic phonons has been used to study the size-dependent melting transition of tin nanocrystals embedded i n a silica film on a Si(100) substrate. A jump in the spectral shift of the surface phonon peaks was detected across the melting temperature and the n ature of the transition was assessed by the vanishing of Bragg peaks. A sim ple effective medium treatment of the elastic constants of the film contain ing solid/liquid inclusions together with a numerical computation of the su rface phonon spectrum explains the observed behavior. A strong central peak was also systematically observed just before melting. [S0163-1829(99)51024 -2].