SYSTEMATIC MEASUREMENT OF CRITICAL-CURRENT DENSITY FOR NARROW YBA2CU3OY LINES

Critical current densities (J(c)'s) of submicron YBa2Cu3Oy (YBCO) lines were studied. Increase in J(c) with reduction of line width (to) was observed reproducibly, when temperature rise of the substrate is suppressed during plasma etching of YBCO. Intermittent etching and liquid-nitrogen cooling were very effective in obtaining sufficient cooling. Temperature dependence of current-voltage characteristics was interpreted in terms of thermally activated vortex motion. This result indicated the existence of a potential barrier to vortex motion. In particular, the surface barrier played an important role in determining J(c) in the submicron lines. Furthermore, the dependence of J(c) on w was strongly dependent on the current concentration to the edges due to Meissner effect.