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 lambda = 0.6 mum 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 approximately 10(-5) nm, where the reflectivity rise typical of the solid-liquid transition is shown to undergo a progressive decrease.