抄録
By the electron tunnelling technique, the energy gap 2Δ in superconducting tin films with various thickness d ranging from 3670 Å to 420 Å was measured as a function of temperature T and magnetic field H parallel to the plane of the tin film. Temperature dependence of 2Δ is almost the same for all tin films, and the mean value of 2Δ(0)⁄kTc is 3.57, where 2Δ(0) means the energy gap at 0°K. As for the behaviours in magnetic field, i.e. H dependence of 2Δ and thickness dependence of the critical field determined from 2Δ–H curves, there are marked differences among the films, d>1900 Å, 1900 Å>d>ca. 700Å and d<ca. 700 Å. Those of the films thicker than 1900 Å agree with the local theories by Ginzburg-Landau-Gor’kov-Douglass and Ginzburg-Landau respectively, while those of the films with medium thickness, 1900 Å>d>ca. 700 Å, are consistent with the non-local theories by Casella-Miller or Nambu-Tuan qualitatively. However for the thickness region, d<ca. 700 Å, there is no theory to explain the experimental results in magnetic field, but if type two superconductivity is assumed for these very thin films, a reasonable explanation can be given.
