Interface properties of YBa_2Cu_3O_(7-x)/I/metal junctions with native and artificial tunnelling barriers

摘要

Tunnelling spectroscopy was used to study interface properties of Yba_2Cu_3O_(7-x)(YB CO)/artificial barrierormal-metal and YBCOative barrierormal-metal tunnel junctions. As artificial tunnelling barriers, YBCO +2percent Co and CeO_2 thin films were used. The native tunnel barrier of YBCO was prepared by a surface treatment to create a YBCO layer with oxygen deficiency. Tunnelling characteristics of the junctions were obtained as a rule, but the corresponding differential characteristics indicate suppression of the palr potential in YBCO near the barrier. Peculiarities like a linear dependence of the differential conductance versus voltage, smeared gap-like structures, and increase of the differential conductance close to zero bias voltage for these junctions were observed. These phenomena are discussed within the model of complex structure creation in the tunnel junction as a result of YBCO degradation near the contact with the metal, as well as pronouncedly inelastic processes in the degraded YBCO.