Josephson device, method of forming josephson device and superconductor circuit

A Josephson device comprising:

• a substrate;
• a first superconducting electrode layer formed on the substrate and having a first sloping surface portion on one end surface thereof;
• an insulator layer formed on the first superconducting electron layer and having a second sloping surface portion on one end surface thereof, so that the first and second sloping surface portions form a continuous sloping surface;
• a barrier layer deposited on the sloping surface;
• and
• a second superconducting electrode layer covering the barrier layer,
• wherein said first and second superconducting electrode layers are made of an oxide superconductor material having (RE)1(AE)2Cu3Oy as a main component, where an element RE is at least one element selected from a group consisting of Y, La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu, and an element AE is at least one element selected from a group consisting of Ba, Sr and Ca;
• and
• said barrier layer is made of a material that includes the element RE, the element AE, Cu and oxygen, where in cations within the material forming the barrier layer, a Cu content is in a range of 35 At. % to 55 At. % and an RE content is in a range of 12 At. % to 30 At. %, and the barrier layer has a composition different from compositions of the first and second superconducting electrode layers.

A Josephson device comprising:

• a substrate having a surface;
• a first superconducting electrode layer formed on the surface of the substrate;
• an insulator formed on the first superconducting electrode layer and having a penetration hole penetrating the insulator layer in a direction taken along a thickness of the insulator layer;
• a barrier layer deposited on the first superconducting electrode layer and within the penetration hole;
• and
• a second superconducting electrode layer filling the penetration hole and covering the barrier layer and the insulator layer,
• wherein said first and second superconducting electrode layers are made of an oxide superconductor material having (RE)1(AE)2Cu3Oy as a main component, where an element RE is at least one element selected from a group consisting of Y, La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu, and an element AE is at least one element selected from a group consisting of Ba, Sr and Ca;
• and
• said barrier layer is made of a material that includes the element RE, the element AE, Cu and oxygen, where in cations within the material forming the barrier layer, a Cu content is in a range of 35 At. % to 55 At. % and an RE content is in a range of 12 At. % to 30 At. %, and the barrier layer has a composition different from compositions of the first and second superconducting electrode layers.

A method of forming a Josephson device comprising the steps of:

• (a) forming on a substrate a first superconducting electrode layer made of an oxide superconductor material;
• (b) forming an insulator layer covering the first superconducting electrode layer;
• (c) removing a portion of the insulator layer to expose the first superconducting electrode layer;
• (d) depositing a barrier layer made of an oxide material on an exposed surface of the first superconducting electrode layer;
• and
• (e) forming a second superconducting electrode layer made of an oxide superconductor material to cover the barrier layer,
• wherein the oxide material forming the barrier layer includes an element RE, an element AE, Cu and oxygen, where the element RE is at least one element selected from a group consisting of Y, La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu, and the element AE is at least one element selected from a group consisting of Ba, Sr and Ca.

A superconductor circuit using magnetic flux quantum as signal carrier, comprising:

• at least one Josephson device comprising a first superconducting electrode layer, a barrier layer and a second superconducting electrode layer that are successively stacked,
• wherein said first and second superconducting electrode layers are made of an oxide superconductor material having (RE)1(AE)2Cu3Oy as a main component, where an element RE is at least one element selected from a group consisting of Y, La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu, and an element AE is at least one element selected from a group consisting of Ba, Sr and Ca;
• and
• said barrier layer is made of a material that includes the element RE, the element AE, Cu and oxygen, where in cations within the material forming the barrier layer, a Cu content is in a range of 35 At. % to 55 At. % and an RE content is in a range of 12 At. % to 30 At. %, and the barrier layer has a composition different from compositions of the first and second superconducting electrode layers.