Spontaneous phase fluctuations of nanoparticles of lead in a silicon oxide matrix

We present room temperature high-resolution electron microscopy (HREM) data and optical-reflectivity results at ? = 0.6 ?m in the temperature range 300-600 K on Pb particles, having dimensions from 15 down to 3 nm and embedded in a matrix of amorphous SiO. HREM gives a clear indication of three different size-dependent regimes for the particles, which are interpreted in terms of spontaneous phase fluctuations occurring for diameters in the range ~ 10-5 nm, where the reflectivity rise typical of the solid-liquid transition is shown to undergo a progressive decrease