High-Tc Ramp-Type Josephson Junctions with PrBa2Cu3-xGaxO7-δ barrier
Superconducting three terminal devices  of sufficient current and voltage gain and integrability are not yet available, so Josephson junctions are still the basic active elements in superconducting electronics. In recent years a lot of effort has been put into the development of reproducible high-Tc Josephson junctions — with mixed success. Even though Josephson behaviour can easily be demonstrated in very simple configurations, the fabrication of reproducible junctions is still quite a problem and is not yet sufficient for medium or large scale levels of integration. Apart from a lack of the understanding of the basic mechanisms of high-Tc superconductivity, also the charge transport properties in high-Tc Josephson junctions are not yet fully understood. This, together with the extremely short coherence length of the order of the chemical binding length and the difficulties in preparing these materials, resulted in junction realisations that were quite often intrinsically complicated and not well understood in their physical behaviour but showed reasonably good current-voltage characteristics, e.g. the different types of grain boundary junctions . In contrast, junctions with simple artificial barriers like normal conductor barriers made of Ag between YBa2Cu3O7-δ show a quite reproducible behaviour if the interface between YBa2Cu3O7-δ and the barrier is reasonably clean . Due to the SNS characteristics and the low normal resistance of these junctions they are only useful for a very limited number of applications.
KeywordsCritical Current Density Josephson Junction Decay Length Barrier Thickness Transmission Line Model
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