THERMAL CONDUCTIVITY OF QUENCHED LEAD FILMS

The thermal conductivity of lead containing a large number of structural lattice defects is measured in the temperature range of about 2 to 20 °K. For the first time it is made possible by means of a special technique to investigate quenched films, which have been evaporated on to a cooled substrate in a high vacuum. The thermal conductivity of these films, which is much smaller than that of the bulk material, increases either by annealing or by increasing condensation temperature and film thickness, respectively. For most of the films the heat conduction is shown to be due only to the electrons. Therefore it can be discussed with respect to the validity of Wiedemann-Franz' Law and to deviations from Matthiessen's Rule in the temperature range of small angle scattering between electrons and phonons. The data of the superconducting state can be fitted to the BRT-expression for electronic conduction limited by defect scattering, if an energy gap of 2 e{open}0=(4.20±0.15)kTc is chosen. The very small values of the phonon conductivity, estimated for the films with the lowest condensation temperatures, could result from the high concentrations of non-zero dimensional lattice defects, which have been observed earlier in such films. © 1969 Springer-Verlag.