EPITAXIAL-GROWTH AND TUNNELING PROPERTIES OF YBA2CU3O7-X PRBA2CU3O7-X/YBA2CU3O7-X TRILAYER STRUCTURES/

Using a multitarget high oxygen pressure sputtering system, we have pr oduced in six high quality epitaxial YBa2Cu3O7-x/PrBa2Cu3O7-x/YBa2Cu3O 7-x trilayer structures on SrTiO3 (001) substrates with PrBa2Cu3O7-x b arrier thicknesses ranging from 10 to 30 nm. The structural properties were determined by x-ray diffraction. Rutherford Back Scattering (RES ) 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 tunneli ng behavior with well developed peaks at +/- 45 mV indicating the pres ence of energy gap structures at +/-2 Delta and flat background conduc tances at high bias. Ratios of the conductance at zero bias, G(0), to the normal conductance at 150 mV, G(150), of about 10 % are observed. These characteristics can be related to the very good interfaces and s uperconducting properties observed in our heterostructures.