GROWTH AND TUNNELING SPECTROSCOPY OF YBACUO PRBACUO/HOBACUO TRILAYERS/

We have measured SIS quasiparticle tunneling in YBaCuO/PrBaCuO/YBaCuO trilayers. The heterostructures were realized on SrTiO3 substrates, by sequential deposition of high quality (001) oriented epitaxial films, using a high pressure de sputtering in pure oxygen plasma. The YBaCuO films show a zero resistance and a diamagnetic transition temperature at 91 K, while the PrBaCuO barrier exhibits a semiconducting behavior . Conductance characteristics vs. voltage, at low biases, show well de veloped peaks indicative of gap structures at +/-45 mV, a flat backgro und conductance for voltage greater than 50 mV and a ratio smaller tha n 0.1 between zero bias and normal state conductance.