Superconducting lead cluster films with particle size dependent reduction of T.

To investigate films of metal clusters, a neutral lead cluster beam, generated by inert gas aggregation, is characterized via time-of-flight mass spectroscopy and subsequently used for growing a thin film ( d=100 Å) on a cold sapphire substrate. In an annealing program the temperature dependence of the electrical resistance of the film is determined by the dc 4-probe technique. Directly after deposition a superconducting transition at T=5.6 K is observed which is shifted to higher temperatures with increasing annealing temperature ( T=6.5 K after annealing at room temperature). [ABSTRACT FROM AUTHOR]