High-temperature Josephson junction and method
AssigneeVarian Associates, Inc.
InventorsIvan Bozovic, James N. Eckstein, Martin E. Klausmeier-Brown, Gary F. Virshup
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Abstract
A hysteretic high-T.sub.c trilayer Josephson junction, and a method of forming the same are disclosed. The junction includes lower and upper high T.sub.c superconducting cuprate films separated by a barrier layer, where the thin films each include a molecular junction layer adjacent the barrier layer which is characterized by a high-T.sub.c cuprate stoichiometry and crystal structure, and a flat two-dimensional surface, as evidenced by its electron diffraction pattern using reflected high-energy electron diffraction. The junction and barrier layers in the junction are formed by atomic layer-by-layer deposition.
Claims18
A hysteretic high-T.sub.c trilayer Josephson junction device comprising
- a substrate,
- first and second high-T.sub.c superconducting cuprate films formed on the substrate,
- a molecular insulating barrier layer between the two films, and
- current and voltage electrodes between said first and second high-T.sub.c layers,
- said junction being characterized by
- (i) a critical current of greater than 10 .mu.A;
- and
- (ii) significant I-V hysteresis.
In a high-T.sub.c trilayer Josephson junction having first and second high-T.sub.c cuprate thin films separated by a molecular insulating barrier layer, an improvement effective to achieve I-V hysteresis characteristics in the junction comprising
- a junction molecular layer in each of said first and second films adjacent said barrier layer, which junction layer is characterized by a high-T.sub.c cuprate lattice stoichiometry and crystal structure, and a flat two-dimensional surface, as evidenced by its electron diffraction pattern using reflected high-energy electron diffraction,
- said barrier layer being characterized by a flat two-dimensional surface, as evidenced by the electron diffraction pattern using reflected high-energy electron diffraction.
A method of preparing a hysteretic high-T.sub.c trilayer Josephson junction comprising
- forming on a substrate a first high-T.sub.c cuprate thin film, where said forming includes depositing by atomic layer-by-layer deposition, a final junction molecular layer which is characterized by a high-T.sub.c cuprate stoichiometry and crystal structure, absence of second-phase defects, and a flat two-dimensional surface, as evidenced by its electron diffraction pattern using reflected high-energy electron diffraction,
- depositing over said junction layer by atomic layer-by-layer deposition, a barrier layer characterized by a flat two-dimensional surface, as evidenced by the electron diffraction pattern using reflected high-energy electron diffraction,
- depositing over said barrier layer, a second high-T.sub.c film having a junction molecular layer which is characterized by a high-T.sub.c cuprate stoichiometry and crystal deposition, and
- forming current and voltage electrodes between said first and second high-T.sub.c electrodes.
In a method of forming a high-T.sub.c trilayer Josephson junction having first and second high-T.sub.c cuprate thin layers separated by a molecular insulating barrier layer, an improvement effective to achieve I-V hysteresis characteristics in the junction comprising
- depositing by atomic layer-by-layer deposition, a junction molecular layer in said first film which is characterized by a high-T.sub.c cuprate lattice stoichiometry and crystal structure, and a flat two-dimensional surface, as evidenced by its electron diffraction pattern using reflected high-energy electron diffraction,
- depositing said barrier layer by atomic layer-by-layer deposition to achieve a molecular layer characterized by a flat two-dimensional surface, as evidenced by the electron diffraction pattern using reflected high-energy electron diffraction, and
- depositing said junction molecular layer in said second high-T.sub.c film by atomic layer-by-layer molecular deposition to achieve a layer which is characterized by a high-T.sub.c cuprate lattice stoichiometry and crystal structure.
In a method of forming a high-T.sub.c trilayer Josephson junction having first and second high-T.sub.c cuprate thin layers separated by a molecular insulative barrier layer, an improvement effective to achieve a desired critical current or normal state resistance in the junction comprising
- depositing by atomic layer-by-layer deposition, a junction molecular layer in said first film formed of Bi.sub.2 Sr.sub.2 Ca.sub.n-1 Cu.sub.n O.sub.2n+4 type metal oxides, where n is between 2-5, and a flat two-dimensional surface, as evidenced by its electron diffraction pattern using reflected high-energy electron diffraction,
- depositing by atomic layer-by-layer deposition, the barrier layer formed of a Bi.sub.2 Sr.sub.2 (Ca,Sr,Dy,Bi).sub.n-1 Cu.sub.n O.sub.2n+4 type metal oxide, where n is greater than 2-20, and Sr, Dy, and/or Bi are substituted as barrier dopants in Ca sites in the barrier layer in an amount effective to produce a desired critical current or normal state resistance in the completed junction, and
- depositing by atomic layer-by-layer deposition, a junction molecular layer in said first film formed of Bi.sub.2 Sr.sub.2 Ca.sub.n-1 Cu.sub.n O.sub.2n+4 type metal oxides, where n is greater than 1, and a flat two-dimensional surface, as evidenced by its electron diffraction pattern using reflected high-energy electron diffraction.
Dependencies are inferred from the claim text.