IR reflection studies of thin YBa 2Cu 3O 7−δ films parallel and perpendicular to the CuO planes

Abstract

We report the infrared to visible (50 to 30 000 cm −1) reflectively of an in-plane aligned a-axis oriented YBa 2Cu 3O 7−δ thi film in the normal (300 K) and superconducting (10 K) states. The film exhibits a pronounced polarization dependent anisotropy in the reflection: for polarization parallel to the CuO planes, the low-temperature reflectance ( R ab) approaches unity at low energies, consistent with the established metal/superconductor behavior. The c-axis reflectivity, on the other hand, is nearly independent of temperature with R c FIR ≈ 0.75 , qualitatively like that of an insulator. Our results compare well with data published for single crystals: the in-plane physics can be described using an extended Drude model, while the out-of-plane data show the material to be a dielectric with ϵ 1 (0) > 85, with the response described by several distinct Lorentz oscillators. We conclude good quality aligned (and anisotropic) YBa 2Cu 3O 7−δ films can be prepared with dimensions that are consistent with those required for known applications.