Reproducible tunneling data on chemically etched single crystals of YBa2Cu3O7.

We have fabricated tunnel junctions between chemically etched single crystals of YBa{sub 2}Cu{sub 3}O{sub 7} and evaporated metal counterelectrodes which exhibit reproducible characteristics. Above the bulk critical temperature of YBa{sub 2}Cu{sub 3}O{sub 7}, {ital T}{sub {ital c}}, the conductance, {ital G}({ital V}), has a linear dependence with voltage and has some asymmetry. Below {ital T}{sub {ital c}}, additional structure associated with the superconductivity appears in {ital G}({ital V}). At {ital T}{much lt}{ital T}{sub {ital c}} there is a reproducible, finite, zero-bias conductance which suggests that there are states at the Fermi energy superconducting YBa{sub 2}Cu{sub 3}O{sub 7}. Junctions with Pb, Sn, Bi, Sb, PbBI, and Au counterelectrodes all show qualitatively similar behavior.