Discrete Periodic Melting Point Observations for Nanostructure Ensembles

We report a study of the thermodynamic properties of indium clusters on a $\mathrm{SiN}{}_x$ surface during the early stages of thin film growth using a sensitive nanocalorimetry technique. The measurements reveal the presence of abnormal discontinuities in the heat of melting below $100°\mathrm{C}$. These discontinuities, for which temperature separation corresponds to a spatial periodicity equal to the thickness of an indium monolayer, are found to be related to the atomic “magic numbers,” i.e., the number of atoms necessary to form a complete shell of atoms at particle surface.