SPECIFIC-HEAT AND SCALING OF HE-4 CONFINED IN A PLANAR GEOMETRY

We report measurements of the specific heat of thick helium films to t est scaling predictions near the superfluid transition, T-lambda. Thes e films, bounded by two silicon wafers, range in thickness from 0.107 to 0.692 mu m. The specific heat of the films is suppressed relative t o that of bulk helium, and the difference of the data from bulk helium scales well with the exponent of the correlation length. We propose a n empirical scaling function which fits the data well for T > T-lambda , and yields the surface specific heat. We also compare the data with various theoretical calculations and experiments. We find that the cal culations underestimate the effect of confinement.