SUPERCONDUCTIVE AND NORMAL STATE TRANSPORT-PROPERTIES OF YBA2CU3O7 FILMS ON SAPPHIRE IN HIGH MAGNETIC-FIELDS

Thin films of YBa2Cu3O7 were deposited on (1120) Al2O3 by laser ablation. X-ray diffraction analysis revealed that the films grow c-axis oriented. The FWHM of the rocking curves were determined to 2.1-degrees for films prepared at substrate temperatures of T(S) greater-than-or-equal-to 830-degrees-C, exhibiting typical inductively measured T(c) -values around 87 K (transition width around 1 K). By means of ESCA depth profiles the diffusion of the Al of the substrate into the superconducting film was analysed. The resistivity rho(T) is almost-equal-to 500-mu-OMEGA-cm at 300 K and exhibits the typical linear temperature dependence with rho(300K)/rho(100K) almost-equal-to 2. In magnetic fields B up to 12 T with the field direction perpendicular to the film surface rho(T) as well as the critical current density j(c)(T) were monitored. The resistive transition shows only little broadening at B = 12 T and T(c,zero) is shifted to 75 K, whereas for j(c) (T) a strong reduction in magnetic fields is observed.