Characterization of Thin-Film Superconductors by Infrared Reflection!.

Infrared reflectivity spectroscopy is shown to be a powerful tool to characterize the new high-Tc oxide superconductors since it gives information about the superconducting gap, phonons, plasmon and possibly low-energy electronic excitations such as excitons, information relevant to understand the mechanism of superconductivity. Problems encountered in the study of ceramic samples and related to the bidimensionality of the properties, previously shown on a single crystal of lanthanum nickel oxide, mostly vanish in the studies of oriented film samples.