New approach to study melting processes in metal nanoparticles: capacitance measurements

The size reduction of the nanosystems with respect to macroscopic samples (or also in the micrometric size range) necessarily implies a concomitant and substantial increase of the surface to volume ratio. The surface atoms often play a role in determining or affecting basic properties of the samples investigated. As a consequence, the quest for new techniques specialized to the study of the electrical, optical or thermodynamic behavior of the surfaces or interfaces is becoming progressively more important. By means of capacitance measurements on metallic (specifically Ga) nanoparticles, through the relationship between derivative of the dielectric constant with respect to the temperature and the contribution to entropy due to the applied electric field, we show that initial disorder starts to take place ≈65 K before full melting. The premelting region is characterized by two regimes, which will be briefly illustrated.