Current transport in high-Tcpolycrystalline films of Y-Ba-Cu-O

Abstract

Electrical measurements were performed on polycrystalline superconducting films of Y-Ba-Cu-O to explore tunneling effects in the film. The films were deposited on SrTi${\mathrm{O}}_3$ (110) substrates via pulsed excimer laser evaporation of bulk superconducting material. Data are reported for two films having $T_c$ (zero-resistance temperature) of 79 and 63 K and transition widths (90% to 10%) of 5 and 15 K, respectively. Temperature-dependent $I-V$ measurements performed over a broad range of $\frac{T}{T_c}$ values (0.05 to 0.99) reveal that in both films the critical current is proportional to ${(1-\frac{T}{T_c})}^{\frac{3}{2}}$ near $T_c$, while at temperatures lower than about $0.8T_c$ it is approximately proportional to ${(1-\frac{T}{T_c})}^2$.