Energy Gap Measurements by Tunneling Between Superconducting Films. I. Temperature Dependence

The electron tunneling technique was used to measure the energy gap 2Δ(t) as a function of temperature in aluminum and tin films. The temperature dependence of the normalized gap Δ(t)Δ(0) for each film agreed rather well with the BCS theory, although a small consistent deviation was found in which the measured values of the gap were slightly larger than predicted by theory. In the case of aluminum, considerable random scatter in the absolute values of 2Δ(0) for the various films was found.