Skip to main content
Article thumbnail
Location of Repository

Novel applications of the Josephson Effect: Ferroelectric Characterisation and Capacitively Shunted Grain Boundary Junctions

By Philip Francis McBrien


This thesis describes applications of the ac Josephson effect. Firstly, results are presented from bicrystal grain boundary YBa2Cu3O7-d junctions shunted with a YBa2Cu3O7-d/SrTiO3/Au multilayer external capacitor, to make a junction with a hysteretic current voltage characteristic operating at high temperatures. A hysteretic junction with a McCumber parameter of 1.01 at 72.3K, with a critical current of 451mA and a resistance of 0.56W was achieved for a junction shunted with a 150mm2 external capacitor with a 50nm SrTiO3 dielectric. The measured capacitance was less than that expected from a calculation of the parallel plate shunt capacitance. The explanation was thermal noise suppression of the hysteresis and the junction saw the shunt capacitor as a distributed impedance rather than a lumped circuit element. It was found during these investigations that the influence of the SrTiO3 substrate on the intrinsic junction capacitance was poorly understood. The permittivity of SrTiO3 is 24000 at 4.2K. A series of YBa2Cu3O7-d Josephson junctions of lengths from 2mm to 20mm was patterned on a SrTiO3 bicrystal and the Fiske resonance dispersion relation was measured. The dispersion relation consisted of two branches, one at low frequencies with a high resonator capacitance per unit length and a high frequency branch with a low resonator capacitance per unit length. This was due to the frequency dependence of the permittivity of bulk SrTiO3, which drops above the soft optic phonon frequency. From the dispersion relation, the permittivity of bulk SrTiO3 was 750 and the soft optic phonon frequency was 145GHz. The ac Josephson effect was exploited to measure the permittivity of thin films of SrTiO3 at microwave frequencies using Josephson junctions coupled to external resonators. The permittivity of 50nm, 100nm and 200nm SrTiO3 films was frequency independent between 100GHz and 900GHz and to decrease with film thickness. The permittivity of the 50nm film was 35 and that of the 200nm film was 187 at 4.2K. The permittivity of the 200nm film was tunable with a dc voltage bias between 245 and 112 at 30K and 116GHz. The grain boundary capacitance was used to probe grain boundary current transport. The capacitance per unit area scaled inversely with resistance area product and increased linearly with critical current density, for undoped and Ca doped YBa2Cu3O7-d grain boundaries on 24° bicrystals. This behaviour could not be explained by tunneling models of grain boundary current transport, and requires current flow over a fraction of the area of the grain boundary.EPSR

Topics: Grain Boundaries, YBCO, Josephson Junctions, Devices
Publisher: Department of Materials Science and Metallurgy
Year: 2000
OAI identifier:
Provided by: Apollo

Suggested articles


  1. (1992). 1/f noise in YBa2Cu3O7-d grain boundary junctions,"
  2. (1999). Effect of oxygen content on YBCO Josephson junction structures," doi
  3. (1990). Electrical properties of grain boundaries in polycrystalline semiconductors," doi
  4. (1996). Electromagnetic and microstructural characterization of YBa2Cu3O7 step edge junctions on (001) LaAlO3 substrates," doi
  5. (1993). Extrinsic or intrinsic conduction in cuprates: Anisotropy, weak and strong links," doi
  6. (2000). Increasing grain boundary critical currents in high-Tc superconductors at 77K," submitted to Nature
  7. (1997). Influence of SrTiO3 bicrystal microstructural defects on YBa2Cu3O7 grain boundary Josephson junctions," doi
  8. (1996). LSCO bicrystal grain boundary Josephson junctions," doi
  9. (1999). On the characteristic voltage of highly oxygenated YBCO grain boundary junctions," doi
  10. (1994). Onedimensional parallel Josephson-junction arrays as a tool for diagnostics," doi
  11. (1992). Pair weakening and channels at cuprate interfaces," doi
  12. (1990). Scaling behaviour of YBa2Cu3O7-d thin film weak links," doi
  13. (2000). Spatial variation of the current in grain boundary Josephson junctions," doi
  14. (1998). Superconducting NCCO bicrystal grain boundary junctions," doi
  15. (1995). Supercurrent density correlation function of YBa2Cu3O7-d grain boundaryReferences Josephson junctions," doi
  16. (1978). Thin film BSCCO Josephson junctions and direct current superconducting quantum interference devices on (001) SrTiO3 bicrystals," doi
  17. (1999). Transport and noise properties of high-Tc bicrystal junctions," doi
  18. (1995). Transport characteristics of calcium doped YBa2Cu3O7-d thin films," doi
  19. (1991). Transport processes and noise in YBa2Cu3O7-d grain boundary junctions," doi
  20. (1997). Transport properties and lower critical field of BSCCO Josephson junctions,"

To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.