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 in 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 nature of the transition was assessed by the vanishing of Bragg peaks. A simple effective medium treatment of the elastic constants of the film containing solid/liquid inclusions together with a numerical computation of the surface phonon spectrum explains the observed behavior. A strong central peak was also systematically observed just before melting. [S0163-1829(99)51024-2].