Title :
Influence of La-doping of YBa2Cu3O7 on transport properties of interface-engineered ramp-edge junctions
Author :
Heinsohn, J.-K. ; Dittmann, R. ; Contreras, J. Rodríguez ; Scherbel, J. ; Klushin, A. ; Siegel, M.
Author_Institution :
Inst. fur Schicht- und Ionentech., Forschungszentrum Julich GmbH, Germany
fDate :
3/1/2001 12:00:00 AM
Abstract :
We have investigated the influence of La-doping of the YBa2-x LaxCu3O7 (YBCO) thin film electrodes on dc and ac Josephson properties of ramp-edge junctions with interface-engineered barriers. Non-doped optimized junctions exhibit critical current densities, jc, of 5·104 A/cm2 and normal sheet resistances, RN·A, of 3·10-9 Ohm·cm2 at 77 K. The transport properties of junctions with x=0.03 La-doping are quite similar to those of non-doped junctions. La-doping of x=0.05 and x=0.07 leads to an increase of RN·A and decrease of jc by about one order of magnitude. Devices with jc<10 4 A/cm2, which are operating in the short junction limit exhibit current-voltage characteristics without any excess current and 100% modulation of critical current in external magnetic field. The current voltage characteristics exhibit well defined Shapiro steps. The dependence of current-step height on microwave current can be described in the resistively-shunted junction model. The strong changes in the temperature dependencies of jc and RN·A suggest different electrical transport properties for junctions fabricated with non-doped and La-doped YBCO. The temperature dependence of the critical current and the normal resistance allows us to draw conclusions to the transport properties of our junctions
Keywords :
Josephson effect; barium compounds; critical current density (superconductivity); high-temperature superconductors; lanthanum compounds; superconducting thin films; yttrium compounds; 77 K; Josephson junction; La doping; Shapiro step; Y(BaLa)2Cu3O7; YBCO thin film electrode; critical current density; current-voltage characteristics; electrical transport properties; interface engineered junction; magnetic field; microwave irradiation; normal sheet resistance; ramp edge junction; resistively shunted junction model; temperature dependence; Critical current; Critical current density; Current-voltage characteristics; Electric resistance; Electrodes; Magnetic fields; Magnetic modulators; Temperature dependence; Transistors; Yttrium barium copper oxide;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
