Film growth and wetting of curved surfaces

We report experiments on the low-temperature adsorption of 4He films on the surface of graphite fibers. We contrast the adsorption on two kinds of fibers, one with a positive radius of curvature, and one for which part of the surface has a negative curvature. The curvature has a dramatic effect on the limiting thickness of the film. For the fiber with positive curvature, the limiting film thickness is less than 200 A, while for the fiber with negative curvature it can reach over 10 000 A. The data agree very well with the universal form of the Dzyaloshinskii, Lifshitz, and Pitaevskii [Adv. Phys. 10, 165 (1961)] theory as worked out by Cheng and Cole [Phys. Rev. B. 38, 987 (1988)]. This agreement, though, may perhaps be fortuitous as the convoluted surface of the fiber gives rise to an adsorption process that is more complex than what this theory describes