YBa₂Cu₃O_x/PrBa₂Cu₃O_x/YBa₂Cu₃O_x Josephson ramp junctions

A detailed study of the fabrication process, current voltage (I‐V) characteristics, and Josephson and normal‐state properties of the YBa2Cu3Ox(YBCO)/PrBa2Cu3Ox(PBCO)/YBCO ramp junctions is presented. The I‐V characteristics can be well described by the resistively shunted junction model. It was found that the critical current Ic and the normal‐state conductance 1/Rn scale linearly with the junction area, whereas Ic, the excess current Iex, and IcRn products decrease with increasing barrier thickness. These junctions with cross‐sectional area A have a good controllability, low capacitance, and high values of IcRn and RnA products. The coherence length ξn of the PBCO barrier is estimated to be between 5 and 8 nm. As unambiguous evidence of the Josephson behavior, the microwave response as a function of the microwave power as well as the modulations of critical current Ic(H) with applied magnetic field are shown. A modulation depth of more than 95% has been observed. Small proximity effect parameters and junction capacitance (C/A∼10−7 F/cm2) show an advantage of these junctions for many applications.