Multilayer structure with zirconium-oxide tunnel barriers and applications of same

• US 20090057652A1
• Filed: 05/23/2008
• Published: 03/05/2009
• Est. Priority Date: 05/23/2007
• Status: Active Grant

• Current Assignee: Northwestern University
• Original Assignee: Northwestern University
• Inventors: SHAFRANIUK, Serhii, NEVIRKOVETS, Ivan, CHERNYASHEVSKYY, Oleksandr, KETTERSON, John
• Granted Patent: US 7,977,668 B2
• Time in Patent Office: Days
• US Class Current: 257/35
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: G06N 10/00 Quantum computing, i.e. information processing based on quantum-mechanical phenomena
• CPC Class Codes: H10N 60/0912 of Josephson-effect devices
• CPC Class Codes: H10N 60/12 Josephson-effect devices
• CPC Class Codes: Y10T 29/49014 Superconductor

Abstract

A multilayer structure with zirconium-oxide tunnel barriers. In one embodiment, the multilayer structure includes a first niobium (Nb) layer, a second niobium (Nb) layer, and a plurality of zirconium-oxide tunnel barriers sandwiched between the first niobium (Nb) layer and the second niobium (Nb) layer, wherein the plurality of zirconium-oxide tunnel barriers is formed with N layers of zirconium-oxide, N being an integer greater than 1, and M layers of zirconium, M being an integer no less than N, such that between any two neighboring layers of zirconium-oxide, a layer of zirconium is sandwiched therebetween.

Claims

1. A multilayer structure with zirconium-oxide tunnel barriers, comprising:

(a) a first niobium (Nb) layer;

(b) a second niobium (Nb) layer; and

(c) a plurality of zirconium-oxide tunnel barriers sandwiched between the first niobium (Nb) layer and the second niobium (Nb) layer.

2. The multilayer structure of claim 1, wherein the plurality of zirconium-oxide tunnel barriers is formed with N layers of zirconium-oxide, N being an integer greater than 1, and M layers of zirconium, M being an integer no less than N, such that between any two neighboring layers of zirconium-oxide, a layer of zirconium is sandwiched therebetween.

3. The multilayer structure of claim 2, wherein each layer of zirconium-oxide is formed by oxidizing a layer of zirconium that is deposited on another layer of zirconium or one of the first niobium (Nb) layer and the second niobium (Nb) layer, and wherein the oxidation of a layer of zirconium is performed at a range of rate about 150 to 1500 Pa s.

4. The multilayer structure of claim 1, wherein each of the first niobium (Nb) layer and the second niobium (Nb) layer has a thickness, D, in the range of about 50 to 200 nm.

5. The multilayer structure of claim 4, wherein each of N layers of zirconium-oxide and M layers of zirconium has a thickness, d, which satisfies the relationship D/d≧

10.

6. The multilayer structure of claim 5, wherein d is from 1 mono-atomic layer to 0.5 nm.

7. The multilayer structure of claim 1, further comprising a substrate, and wherein the first niobium (Nb) layer is deposited on the substrate.

8. A multilayer structure with zirconium-oxide tunnel barriers, comprising:

(a) a first layer of metallic material;

(b) a second layer of metallic material; and

(c) a plurality of zirconium-oxide tunnel barriers sandwiched between the first layer of metallic material and the second layer of metallic material.

9. The multilayer structure of claim 8, wherein the plurality of zirconium-oxide tunnel barriers is formed with N layers of zirconium-oxide, N being an integer greater than 1, and M layers of zirconium, M being an integer no less than N, such that between any two neighboring layers of zirconium-oxide, a layer of zirconium is sandwiched therebetween.

10. The multilayer structure of claim 9, wherein each layer of zirconium-oxide is formed on a layer of zirconium or one of the first layer of metallic material and the second layer of metallic material.

11. The multilayer structure of claim 8, wherein each of the first layer of metallic material and the second layer of metallic material has a thickness, D, in the range of about 50 to 200 nm.

12. The multilayer structure of claim 11, wherein each of N layers of zirconium-oxide and M layers of zirconium has a thickness, d, which satisfies the relationship D/d≧

10.

13. The multilayer structure of claim 12, wherein d is from 1 mono-atomic layer to 0.5 nm.

14. The multilayer structure of claim 8, further comprising a substrate, and wherein the first layer of metallic material is deposited on the substrate.

15. The multilayer structure of claim 14, wherein each of the first layer of metallic material and the second layer of metallic material is selected from the group of metals consisting of niobium, niobium plus nitrogen, niobium plus tin, vanadium plus silicon, niobium plus nitrogen and carbon, niobium plus germanium, and niobium plus germanium and silicon.

16. A method for making a multilayer structure with zirconium-oxide tunnel barriers, comprising the steps of:

(a) providing a first niobium (Nb) layer;

(b) providing a second niobium (Nb) layer; and

(c) forming a plurality of zirconium-oxide tunnel barriers sandwiched between the first niobium (Nb) layer and the second niobium (Nb) layer.

17. The method of claim 16, wherein the plurality of zirconium-oxide tunnel barriers is formed with N layers of zirconium-oxide, N being an integer greater than 1, and M layers of zirconium, M being an integer no less than N, such that between any two neighboring layers of zirconium-oxide, a layer of zirconium is sandwiched therebetween.

18. The method of claim 17, wherein each layer of zirconium-oxide is formed by oxidizing a layer of zirconium that is deposited on another layer of zirconium or one of the first niobium (Nb) layer and the second niobium (Nb) layer, and wherein the oxidation of a layer of zirconium is performed at a range of rate about 150 to 1500 Pa s.

19. The method of claim 16, further comprising the step of providing a substrate, wherein the first niobium (Nb) layer is deposited on the substrate.

20. A two-qubit gate, comprising:

a double barrier Josephson junction structure having

(a) a first superconductor layer;

(b) a second superconductor layer;

(c) a first insulating barrier sandwiched between the first superconductor layer 402 and the second superconductor layer;

(d) a third superconductor layer that is spatially positioned closer to the second superconductor layer than to the first superconductor layer; and

(e) a second insulating barrier sandwiched between the second superconductor layer and the third superconductor layer;

a first terminal formed on the first superconductor layer;

a second terminal formed on the second superconductor layer; and

a third terminal formed on the third superconductor layer,

wherein when an external potential is applied to the double barrier Josephson junction structure, a first super current flows between the first terminal and the second terminal through the first insulating barrier with a first phase difference φ

₁, and a second super current flows between the second terminal and the third terminal through the second insulating barrier with a second phase difference φ

₂, respectively.

21. The two-qubit gate of claim 20, wherein each of the first superconductor layer, the second superconductor layer and the third superconductor layer comprises a layer of zirconium, and each of the first insulating barrier and the second insulating barrier comprises a layer of zirconium-oxide, respectively.

22. The two-qubit gate of claim 20, wherein each of the first superconductor layer, the second superconductor layer and the third superconductor layer comprises a layer of metallic material that is selected from the group of metals consisting of niobium, niobium plus nitrogen, niobium plus tin, vanadium plus silicon, niobium plus nitrogen and carbon, niobium plus germanium, and niobium plus germanium and silicon, and each of the first insulating barrier and the second insulating barrier comprises a layer of the zirconium-oxide, respectively.

23. The two-qubit gate of claim 20, wherein each of the first superconductor layer, the second superconductor layer and the third superconductor layer comprises a layer of metallic material that is selected from the group of metals consisting of niobium, niobium plus nitrogen, niobium plus tin, vanadium plus silicon, niobium plus nitrogen and carbon, niobium plus germanium, and niobium plus germanium and silicon, and each of the first insulating barrier and the second insulating barrier comprises a layer of the oxidized metallic material, respectively.