Properties of Very Thin Aluminum Films

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Abstract
Thin films of aluminum have been produced in the thickness range of 1000–30 Å in small area samples with photoetched edges. The superconducting transition temperature Tc, the critical magnetic field Hc, and the room‐temperature conductivity have been measured as a function of thickness d. The results indicate that films as thin as 30 Å act essentially as uniform layers in which the crystal size is approximately equal to the film thickness. The transition temperature was found to vary linearly with d−1. Hc (T) was measured from Tc to 0.4°K. For thickness from 1000 to 200 Å, Hc∼d−3/2, as expected from the Ginzburg‐Landau theory. For d Hc is paramagnetically limited to about 49 kOe = 19.6Tc, slightly above the Clogston limit.