Epitaxial growth and tunneling properties of YBa2Cu3O7-x/PrBa2Cu3O7-x/YBa2Cu3O7-x trilayer structures

Using a multitarget high oxygen pressure sputtering system, we have produced in situ high quality epitaxial YBalCu307 . .1 PrBa2Cu307_. NBa2Cu307 .• trilayer structures on SrTi03 (00 I) substrates with PrBa2Cu307 .• barrier thicknesses ranging from 10 to 30 nm. The structural properties were determined by x-ray diffraction. Rutherford Back Scattering (RBS) and Transmission Electron Microscopy (TEM) analysis, which showed an epitaxial growth of the trilayers with sharp and clean interfaces. I-V and dl/dV vs V measurements showed a clear SIS quasiparticle tunneling behavior with well developed peaks at ± 45 m V indicating the presence of energy gap structures at ±2~ and flat background conductances at high bias. Ratios of the conductance at zero bias, G(O), to the normal conductance at 150 m V, G( 150), of about 10 % are observed. These characteristics can be related to the very good interfaces and superconducting properties observed in our heterostructures.