Interface effects in melting of Pb clusters on the Cu(111) surface

The growth and melting transition of Pb clusters on the Cu(111) surface have been studied with low energy electron microscopy. Kinetic growth and equilibrium cluster shapes are distinguished and a systematic variation of the melting temperature among individual clusters in an ensemble has been observed. A simple thermodynamic model is proposed which accounts for this unusual melting behaviour through known finite size and new interface effects. The role of the interface roughness, e.g. atomic steps, in modifying the interface tension between adsorbate and substrate is suggested by these results.