Abstract
We have fabricated low leakage tunnel junctions on the chemically etched surfaces of (001) oriented YBa2Cu3O7 thin films. The etching process is successful in removing the poor quality surface layer which develops during post oxygen annealing of the films. To demonstrate this, I will present tunneling data obtained on our Pb/insulator/YBa2Cu3O7 thin film planar tunnel junctions and show that it compares well with tunneling results obtained with thin film tunnel junctions made by other means and with junctions on single crystals.Above the bulk critical temperature of YBa2Cu3O7, Tc, the conductance as a function of voltage, G(V), of these tunnel junctions depends linearly on voltage and has some asymmetry. Below Tc, additional structure associated with the superconductivity appears in G(V). At T<<Tc, there is a reproducible finite zero bias conductance. If these features, which have been observed in junctions fabricated by many methods, reflect the bulk quasiparticle density of states of YBa2Cu3O7 then superconductivity in YBa2Cu3O7 does not appear to be simple BCS like.
Published Version
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