Melting point lowering of thin metal films (Me = In, Sn, Bi, Pb) in Al/Me/Al film system

The variation of the melting point of thin films (10–40 nm) of In, Sn, Bi and Pb between thick (100 nm) Al films was investigated using elegant differential technique. The layer systems have been prepared by subsequent condensation of the components on amorphous substrates in vacuum. A decrease of the melting point of several degrees has been found for the metals in question between Al films. The differential method enables us to refine the values of the eutectic temperature for Me/Al systems and, in particular, to reveal that the eutectic temperature for the Al/In alloy does not coincide with the melting point of In, as was supposed till now, but is lower by 0.8 °C. The results are discussed on the basis of a thermodynamic approach and evolution of the binary phase diagram of fusibility with decreasing film thickness.