Properties of epitaxial films of YBa2Cu3O7-

We present measurements of the properties of epitaxial thin films of superconducting YBa2Cu3O7-, with Tc about 90 K, transition widths of 2.5 K, and critical currents in excess of 105A/cm2 at 77 K. The temperature dependence of the upper critical field exceeds 4 T/K for fields parallel to the film (i.e., H to the c axis) and the anisotropy of the upper critical field ranged between two and three. Our tunneling gaps (15-21 meV) are similar to previous results on ceramic and single-crystal samples of YBa2Cu3O7-. Infrared measurements of the gap energy suggest a larger value than previous measurements on polycrystalline material. The temperature dependence of the Hall coefficient is similar to that for the bulk. © 1987 The American Physical Society.