THE FORMATION OF 2-LAYERED YBA2CU3O7-DELTA SUPERCONDUCTING FILMS AND THEIR MICROWAVE SURFACE-RESISTANCE

The structure and crystallographic orientation of YBa2Cu3O7-delta films on BaxSr1-xTiO3/MgO heteroepitaxial layers were investigated by the conventional methods of electron diffraction, electron microscopy and by specific methods of Raman scattering of light and backscattering of middle-energy ions. A film of over 350 nm thick may consist of an inner highly-oriented layer and an outer disoriented one. Measurements of the microwave surface resistance R(s) at 60 GHz and 4.2 K have confirmed a complicated character of the film structure. ft has been shown that the microwave response of two-layer films in a static magnetic field is determined by the losses in the outer disoriented or granular layer and that the dependence R(s)(H-) appears in the field H- starting from approximately 10 Oe. In highly-oriented films no dependence of R(s) on the magnetic field H- was observed in the range from 0 to 100 Oe.