Claims
- 1. A method for manufacturing a superconducting device having a tunnel junction formed of an extremely thin insulator layer having a thickness sufficient to form a tunnel junction barrier, said insulator layer being sandwiched between a pair of oxide superconducting layers, the method including
- forming a first oxide superconducting layer on a substrate,
- depositing at a temperature not higher than 200.degree. C. on the first superconducting layer an amorphous oxide insulator layer having no pinhole,
- heat-treating the deposited oxide insulator layer so as to improve crystallinity of the deposited oxide insulator layer at a temperature not lower than 300.degree. C. and not higher than 700.degree., and
- forming a second oxide superconducting layer on the oxide insulator layer.
- 2. A method claimed in claim 1 wherein the first and second oxide superconducting layer are formed of a high-Tc copper-oxide oxide superconductor material.
- 3. A method claimed in claim 2 wherein the oxide insulator thin film is formed of a material selected from the group consisting of MgO, SrTiO.sub.3, NdGaO.sub.3, Y.sub.2 O.sub.3, LaAlO.sub.3, LaGaO.sub.3, Al.sub.2 O.sub.3, and ZrO.sub.2.
- 4. A method claimed in claim 3 wherein the oxide insulator thin film is deposited on the first superconducting layer so as to have a thickness of not more than 20 .ANG..
- 5. A method claimed in claim 3 wherein the first and second oxide superconducting layers are independently formed of a material selected from the group consisting of a Y--Ba--Cu--O compound oxide superconductor material, a Bi--Sr--Ca--Cu--O compound oxide superconductor material, and a Tl--Ba--Ca--Cu--O compound oxide superconductor material.
- 6. A method claimed in claim 3 wherein the substrate is formed of a material selected from the group consisting of a MgO single crystal, a SrTiO.sub.3 single crystal, a NdGaO.sub.3 single crystal, a Y.sub.2 O.sub.3 single crystal, a LaAlO.sub.3 single crystal, a LaGaO.sub.3 single crystal, a Al.sub.2 O.sub.3 single crystal, and a ZrO.sub.2 single crystal.
- 7. A method claimed in claim 3 wherein the substrate is formed of a material selected from the group consisting of a MgO (100) substrate, a SrTiO.sub.3 (110) substrate, a SrTiO.sub.3 (100) substrate and a NdGaO.sub.3 (001) substrate.
- 8. A method claimed in claim 2 wherein the oxide insulator layer is formed of MgO.
- 9. A method claimed in claim 8 wherein the MgO thin film is deposited on the first superconducting layer so as to have a thickness of not more than 20 .ANG..
- 10. A method claimed in claim 8 wherein the MgO thin film is heat-treated at a temperature not lower than 300.degree. C. but not higher than 700.degree. C. for a period of time not shorter than 10 minutes but not longer than 2 hours.
- 11. A method claimed in claim 10 wherein the MgO thin film is deposited by a sputtering using a MgO single crystal as a target.
- 12. A method claimed in claim 10 wherein the first and second oxide superconducting layers are independently formed of a material selected from the group consisting of a Y--Ba--Cu--O compound oxide superconductor material, a Bi--Sr--Ca--Cu--O compound oxide superconductor material, and a Tl--Ba--Ca--Cu--O compound oxide superconductor material.
- 13. A method claimed in claim 10 wherein the substrate is formed of a material selected from the group consisting of a MgO single crystal, a SrTiO.sub.3 single crystal, a NdGaO.sub.3 single crystal, a Y.sub.2 O.sub.3 single crystal, a LaAlO.sub.3 single crystal, a LaGaO.sub.3 single crystal, a Al.sub.2 O.sub.3 single crystal, and a ZrO.sub.2 single crystal.
- 14. A method claimed in claim 10 wherein the substrate is formed of a material selected from the group consisting of a MgO (100) substrate, a SrTiO.sub.3 (110) substrate, a SrTiO.sub.3 (100) substrate, a SrTiO.sub.3 (100) substrate and a NdGaO.sub.3 (001) substrate.
- 15. A method for manufacturing a superconducting device having a tunnel junction formed of an extremely thin insulator layer having a thickness sufficient to form a tunnel junction barrier, said insulator layer being sandwiched between a pair of oxide superconducting layers, the method including
- forming a first oxide superconducting layer on a substrate,
- depositing by a sputtering, an amorphous MgO thin film on the first superconducting layer at a substrate temperature of not higher than 200 .degree. C.,
- heat-treating the MgO thin film at a temperature not lower than 300.degree. C. and not higher than 700.degree., and
- forming a second oxide superconducting layer on the oxide insulator layer.
- 16. A method claimed in claim 15 wherein the MgO thin film is deposited by a sputtering using a MgO single crystal as a target, so that the deposited MgO thin film has a thickness of not more than 20 .ANG..
- 17. A method claimed in claim 16 wherein the MgO thin film is heat-treated in an oxygen atmosphere at a temperature not lower than 300.degree. C. but not higher than 700.degree. C. for a period of time not shorter than 10 minutes but not longer than 2 hours.
- 18. A method claimed in claim 17 wherein the first and second oxide superconducting layers are formed of a high-Tc copper-oxide oxide superconductor material and wherein the substrate is formed of a material selected from the group consisting of a MgO single crystal, a SrTiO.sub.3 single crystal, a NdGaO.sub.3 single crystal, a Y.sub.2 O.sub.3 single crystal, a LaAlO.sub.3 single crystal, a LaGaO.sub.3 single crystal, a Al.sub.2 O.sub.3 single crystal, and a ZrO.sub.2 single crystal.
- 19. A method claimed in claim 17 wherein the first and second superconducting oxide layers are independently formed of a material selected from the group consisting of a Y--Ba--Cu--O compound oxide superconductor material, a Bi--Sr--Ca--Cu--O compound oxide superconductor material, and a Tl--Ba--Ca--Cu--O compound oxide superconductor material, and wherein the substrate is formed of a material selected from the group consisting of a MgO (100) substrate, a SrTiO.sub.3 (110) substrate, a SrTiO.sub.3 (100) substrate and a NdGaO.sub.3 (001) substrate.
- 20. A method for manufacturing a tunnel junction Josephson device with a tunnel junction formed of an ultrathin insulator layer having a thickness sufficient to form a tunnel junction barrier, said insulator layer being sandwiched between a pair of superconducting layers, the method including:
- forming a first oxide superconducting layer on a substrate;
- depositing on the first superconducting layer a pinholefree amorphous MgO oxide insulator layer at a temperature not higher than 200.degree. C.;
- heat-treating the deposited oxide insulator layer to improve crystallinity of the deposited oxide insulator layer at a temperature not lower than 300.degree. C. and not higher than 700.degree.; and
- forming a second oxide superconducting layer on the oxide insulator layer.
- 21. A method for manufacturing a superconducting device having a tunnel junction formed of an extremely thin insulator layer having a thickness sufficient to form a tunnel junction barrier, the insulator layer being sandwiched between a pair of oxide superconducting layers, the method including:
- forming a first superconducting layer of oxide superconductor on a substrate,
- depositing on the first superconducting layer a pinholefree amorphous oxide insulator layer, the oxide insulator layer being deposited at a substrate temperature of not higher than 200.degree. C.,
- heat-treating the depositing oxide insulator layer for at least ten minutes at a temperature between 300.degree. and 700.degree. C. so as to improve crystallinity of the deposited oxide insulator layer without causing the deposited oxide insulator layer to become polycrystallized, and
- forming a second oxide superconducting layer on the oxide insulator layer, the oxide insulator layer being formed of a material which matches the first and second superconducting layers in crystal lattice so that a clear boundary is formed between the oxide insulator layer and each of the superconducting layers.
Priority Claims (1)
Number |
Date |
Country |
Kind |
3-018222 |
Jan 1991 |
JPX |
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Parent Case Info
This application is a continuation of application Ser. No. 08/284,278, filed Aug. 2, 1994; which is a continuation of application Ser. No. 08/145,302, filed Nov. 3, 1993; which is a continuation of application Ser. No. 07/819,291, filed Jan. 10, 1992, all abandoned.
US Referenced Citations (1)
Number |
Name |
Date |
Kind |
5061687 |
Takada et al. |
Oct 1991 |
|
Foreign Referenced Citations (4)
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Country |
0371481 |
Nov 1989 |
EPX |
0341148A2 |
Nov 1989 |
EPX |
0459906 |
May 1991 |
EPX |
3-285373 |
Dec 1991 |
JPX |
Non-Patent Literature Citations (4)
Entry |
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S. Tanaka et al, IEEE Transactions On Magnetics, vol. 27, No. 2, Mar. 1991, pp. 1607-1611, New York, US. |
Hirata et al, "Tunneling measurements on superconductor/insulator/superconductor junctions using single-crystal YBa.sub.2 Cu.sub.3 0.sub.7 x thin films" Appl. Phys. lett. 56(7) Feb. 1990 pp. 683-685. |
Furuyama et al, "In-situ growth of YBa.sub.2 Cu.sub.3 0.sub.7-x thin films by reactive co-evaporation technique," 2nd Workshop on High-Temperature Superconducting Electron Devices, Jun. 1989 (Japan) pp. 105-108. |
Continuations (3)
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Number |
Date |
Country |
Parent |
284278 |
Aug 1994 |
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Parent |
145302 |
Nov 1993 |
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Parent |
819291 |
Jan 1992 |
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