Epitaxial Growth and Characteristics of the YBCO/STO/YBCO Tunneling Junctions

We report the growth on MgO (100) of the insulating SrTiOs (STO) thin film and the YBa2CusO~_,(YBCO)/STO heteroepitaxial multilayer structure using the insitu pulsed laser ablation technique. By simply placing a shadow mask between the target material and the substrate, the particulate problem peculiar to the excimer laser deposition technique was effectively eliminated. Epitaxial YBCO thin films on STO//MgO and STO/YBCO//MgO with Tc as high as 91 K and 84 K were obtained by this “eclipse method”. We deduce the energy gap of YBCO from the tunneling characteristics (dl/dV-V) f o our YBCO/STO/YBCO junctions as &b = 19-21 meV and A, = 4-5 meV. These results are consistent with the existing reports.