The influence of dielectric films on the superconductivity of thin Sn and Tl films

The change in transition temperature for thin Sn and Tl films has been measured after deposition of dielectric substances. The change in transition temperature is inversely proportional to the thickness of the superconducting film and relatively independent of the thickness of the dielectric film. When SnS or Tl₂Se is deposited on Sn films, the transition temperature is depressed. When TICl or Tl₂Se is deposited on Tl films, the transition temperature is increased. When S is deposited on Tl films, there is no initial change inT _c ; however,T _c is appreciably increased after annealing. A possible explanation for this effect is the reduction of the free electron concentration in the metal through the formation of the contact potential between the dielectric and the metal.