FABRICATION AND TUNNELING MEASUREMEN YBa,Cu,O,/CaF,/Nb THIN FILM TUNNEL JUNCTI

The heteroepitaxial growth of YBa&u,Ox(YBCO)/CaF, has been studied and this structure has been applied to tunnel junctions. The CaF, thin films were epitaxially grown with (1 11) orientation on YBCO(110) films. The tunneling measurements of YBCO( 1 lO)/CaFJNb junctions exhibited that the differential conductance curves have pronounced gap-like structures with sharp peaks at the energy gap edge. The temperature dependence of the energ gap was well fitted to the scaled BCS curve. The 2A/kTc of about 8 was derived from the energy gap of 1SmeV and To of 45K obtained by the fitting. This 2mTc value was consistent with the infrared reflectivity data reported for the direction parallel to the cu-0 planes.