AFM Nano-Plough Planar YBCO Micro-Bridges: Critical Currents and Magnetic Field Effects

The critical current (I _C) of YBa₂Cu₃O_7−x (YBCO) AFM plough micro-constrictions is measured as a function of temperature, width and the magnetic flux density (B), which was applied perpendicular to the YBCO ab-plane and surface of the bridges. C-axis oriented thin films of YBa₂Cu₃O_7−x were deposited on MgO substrates using an inverted cylindrical magnetron (ICM) sputtering technique. The films were then patterned into 8–10 micron size strips, using standard photolithography and dry etching processes. Micro-bridges with widths between 1.9 μm to 4.1 μm were fabricated by using atomic force microscope (AFM) nanolithography techniques. Critical current versus temperature data shows a straight-line behavior, which is typical of constriction type Josephson junctions. The I _C versus B characteristics exhibited a modulation, and a suppression of the critical current of up to 84%. It was also found that the critical current increases with increasing constriction width.