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Abstract

We have performed tunnelmeasurements on evaporated tin-films with various amounts of copper added. The tunneljunctions were evaporated and cooled down to helium temperatures in situ in a metal-cryostat. Tin-copper-films, which are condensed at low temperatures, are amorphous. They have critical temperatures from 7 °K to 3,5 °K depending on the content of copper. Tunnelmeasurements indicate that the high transition temperature belongs to a superconductor with strong coupling, whereas the lower critical temperature is characteristic of a weak coupling superconductor. Structures in tunnelcharacteristics and transition-curves indicate that a film can have several energy-gaps and that regions with strong and weak coupling can exist in the films. — Describing the metal-cryostat we point out that one can reach temperatures below 1 °K with small pumping rates by diminishing the Hell film flux.