Superconducting Pb-Pb tunneling near T-c

We have measured electron tunneling from Pb films into (111) oriented Pb films at temperatures from 1.2 to 7.2 degrees K. Above 6 degrees K, structure in dV/dI at voltages greater than 2 Delta is observed which is not the same as that found at low temperature. One new feature, a resistance maximum just outside 2 Delta, is shown by a numerical calculation to arise from the occupation of excited states above the gap. The other, a resistance peak at 3.5 mV, is shown by further calculation to be associated primarily with the phonon-emission structure described by strong-coupling theory. We find that the effect of the previously predicted recombination process, also located at 3-4 mV, is too broad to be clearly identified.