Fluctuation Contributions to the Heat Capacity of Amorphous Superconducting Films

The heat capacities of superconducting amorphous films have been measured near the transition temperature. The films, of bismuth-antimony alloy, had an area of 0.5 ${\mathrm{cm}}^2$ and thickness ranging from 150 to 1350 Å. An ac temperature calorimetric technique was employed. Fluctuation contributions to the heat capacity were observed. Resistivity measurements of the same films displayed the same fluctuation effects reported by other authors. The temperature dependence of the fluctuation heat capacity was consistent with a behavior of ${\mathrm{}\left(\mathrm{reduced}\mathrm{temperature}\right)\mathrm{}}^{-1\mathrm{}}$ and had the same width as the resistive transition. No singular behavior near $T_c$ was observed. The temperature dependence close to $T_c$ predicted by Masker, Marcelja, and Parks was not seen. The rounding of the transition can be understood by a Hartree-like theory first proposed by Gunther and Gruenberg.