Properties of epitaxial films of YBa/sub 2/Cu/sub 3/O/sub 7-//sub delta/

We present measurements of the properties of epitaxial thin films of superconducting YBa/sub 2/Cu/sub 3/O/sub 7-//sub delta/, with T/sub c/ about 90 K, transition widths of approx.2.5 K, and critical currents in excess of 10/sup 5/A/cm/sup 2/ at 77 K. The temperature dependence of the upper critical field exceeds 4T/K for fields parallel to the film (i.e., Hperpendicular to the c axis) and the anisotropy of the upper critical field ranged between two and three. Our tunneling gaps (..delta..approx.15--21 meV) are similar to previous results on ceramic and single-crystal samples of YBa/sub 2/Cu/sub 3/O/sub 7-//sub delta/. 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.