Electron Tunneling into Disordered Thin Films

Disordered and recrystallized thin films of Sn, Pb, Bi, and Bi1-xSbx both normal and superconducting are investigated by electron tunneling. The films are prepared by evaporation onto a cooled substrate. We studied especially the effect of lattice disorder on the superconducting parameters and on the phonon spectrum which is calculated from the superconducting-electron density of states. The most significant property of the disordered films is an increase of the low-energy-phonon density of states. Anomalies of the tunneling resistance are more or less observed in all junctions. The influence of those anomalies on the evaluation of the superconducting parameters is considered.