The influence of in-plane 0-45 deg grain boundary on microwave surface resistance of c-axis YBa_2Cu_3O_y films on MgO substrate

摘要

The effect of in-plane 0-45 deg grain boundaries on surface resistance (R_s) of c-axis YBa_2Cu_3O_y (YBCO) films on MgO substrates is discussed. Samples that have various densities of 45 deg rotated grains were prepared using a self-template technique. The R_s values at 22 GHz were measured by the dielectric resonator method using a cryocooler. The R_s systematically changed corresponding to the amount of 0-45 deg grain boundaries. Conspicuous feature of the films including 0-45 deg grain boundaries is a large residual surface resistance. The R_s of almost perfectly in-plane aligned YBCO film scaled to 10 GHz were 0.12 m#OMEGA# at 20 K and 0.67 m#OMEGA# at 77 K on the assumption of tan #delta# = 0, respectively.