YBa2Cu3O7−δ-Ag-Al/Al2O3/Pb tunnel junctions based on the superconducting proximity effect

Abstract

YBa2Cu3O7−δ-Ag-Al/Al2O3/Pb superconducting tunnel junctions with high subgap resistance were fabricated using the proximity effect induced superconductivity in the Ag-Al layer by the YBa2Cu3O7−δ film. At low temperature an energy gap of 9–10 meV is found to be induced in the aluminum layer. Above 20 K the induced gap disappears mainly due to the decreased normal metal coherence length. At higher voltages (V≤120 meV) the dynamic conductance dI/dV∝V, characteristic for the normal tunneling density of states of the oxide superconductor.