JP3073142B2 - Stacked Josephson device - Google Patents
Stacked Josephson deviceInfo
- Publication number
- JP3073142B2 JP3073142B2 JP07052042A JP5204295A JP3073142B2 JP 3073142 B2 JP3073142 B2 JP 3073142B2 JP 07052042 A JP07052042 A JP 07052042A JP 5204295 A JP5204295 A JP 5204295A JP 3073142 B2 JP3073142 B2 JP 3073142B2
- Authority
- JP
- Japan
- Prior art keywords
- superconducting
- barrier layer
- layer
- superconducting layer
- josephson
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 230000004888 barrier function Effects 0.000 claims description 58
- 239000013078 crystal Substances 0.000 claims description 20
- 229910052791 calcium Inorganic materials 0.000 claims description 4
- 229910052802 copper Inorganic materials 0.000 claims description 4
- 229910052742 iron Inorganic materials 0.000 claims description 4
- 229910052747 lanthanoid Inorganic materials 0.000 claims description 4
- 150000002602 lanthanoids Chemical class 0.000 claims description 4
- 229910052702 rhenium Inorganic materials 0.000 claims description 4
- 229910052712 strontium Inorganic materials 0.000 claims description 4
- 229910052719 titanium Inorganic materials 0.000 claims description 4
- 229910052721 tungsten Inorganic materials 0.000 claims description 4
- 229910052720 vanadium Inorganic materials 0.000 claims description 4
- 239000000463 material Substances 0.000 description 58
- 239000000758 substrate Substances 0.000 description 18
- 238000012360 testing method Methods 0.000 description 9
- 238000002441 X-ray diffraction Methods 0.000 description 8
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 8
- 239000001301 oxygen Substances 0.000 description 8
- 229910052760 oxygen Inorganic materials 0.000 description 8
- 239000010409 thin film Substances 0.000 description 8
- 238000010168 coupling process Methods 0.000 description 6
- 238000005859 coupling reaction Methods 0.000 description 6
- 238000000034 method Methods 0.000 description 5
- 238000000206 photolithography Methods 0.000 description 5
- 239000012298 atmosphere Substances 0.000 description 4
- 239000007788 liquid Substances 0.000 description 4
- 238000001755 magnetron sputter deposition Methods 0.000 description 4
- 238000000059 patterning Methods 0.000 description 4
- 229910002367 SrTiO Inorganic materials 0.000 description 3
- 230000008878 coupling Effects 0.000 description 3
- 230000001747 exhibiting effect Effects 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 239000002887 superconductor Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 239000000470 constituent Substances 0.000 description 2
- RKTYLMNFRDHKIL-UHFFFAOYSA-N copper;5,10,15,20-tetraphenylporphyrin-22,24-diide Chemical compound [Cu+2].C1=CC(C(=C2C=CC([N-]2)=C(C=2C=CC=CC=2)C=2C=CC(N=2)=C(C=2C=CC=CC=2)C2=CC=C3[N-]2)C=2C=CC=CC=2)=NC1=C3C1=CC=CC=C1 RKTYLMNFRDHKIL-UHFFFAOYSA-N 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000010408 film Substances 0.000 description 2
- 239000001307 helium Substances 0.000 description 2
- 229910052734 helium Inorganic materials 0.000 description 2
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 2
- 238000000608 laser ablation Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- 241000238366 Cephalopoda Species 0.000 description 1
- 239000012300 argon atmosphere Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000006378 damage Effects 0.000 description 1
- 238000003795 desorption Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000004453 electron probe microanalysis Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 238000009931 pascalization Methods 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000000634 powder X-ray diffraction Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 230000035882 stress Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000008646 thermal stress Effects 0.000 description 1
Landscapes
- Inorganic Compounds Of Heavy Metals (AREA)
- Superconductor Devices And Manufacturing Methods Thereof (AREA)
- Containers, Films, And Cooling For Superconductive Devices (AREA)
- Compounds Of Iron (AREA)
- Physical Vapour Deposition (AREA)
Description
【０００１】[0001]
【産業上の利用分野】本発明は各種電磁波センサー、コ
ンピュータや集積回路に使用されるスイッチング素子や
論理回路、各種センサー、ＳＱＵＩＤ等あるいはそれを
利用した医療機器等で用いられる素子やシステムに利用
可能な積層型ジョセフソン素子に関する。The present invention can be applied to various electromagnetic wave sensors, switching elements and logic circuits used in computers and integrated circuits, various sensors, SQUIDs and the like and elements and systems used in medical equipment and the like using the same. The present invention relates to a multilayer Josephson device.
【０００２】[0002]
【従来の技術】液体窒素の沸点よりも高い温度で超電導
性を示す材料としては、ＹＢａ2Ｃｕ3Ｏ7-xで代表され
るＹ系材料、Ｂｉ2Ｓｒ2Ｃａ2Ｃｕ3Ｏyで代表されるＢ
ｉ系材料や臨界温度が１１０Ｋよりも高いＴ１系、Ｈｇ
系材料等が知られており、これらの材料のジョセフソン
素子への応用が検討されている。例えば、積層型ジョセ
フソン素子につぃては、M.Lee,et al.,Phys.Rev.,B39,8
01(1989)やC.Rossel,et al.,Physica C,185-189,2551(1
991)等多くの研究報告がなされている。 2. Description of the Related Art As a material exhibiting superconductivity at a temperature higher than the boiling point of liquid nitrogen, a Y-based material represented by YBa 2 Cu 3 O 7-x and a Bi 2 Sr 2 Ca 2 Cu 3 O y represented. B
i-type material and T1 type with critical temperature higher than 110K, Hg
System materials and the like are known, and application of these materials to Josephson devices is being studied. For example, for a multilayer Josephson device, see M. Lee, et al., Phys. Rev., B39 , 8
01 (1989) and C. Rossel, et al., Physica C, 185-189 , 2551 (1
991) and many other research reports.
【０００３】又、積層型ジョセフソン素子以外にも、ポ
イントコンタクト型や弱結合型のジョセフソン素子も知
られており、特に、弱結合型のジョセフソン素子の検討
が盛んに行われている。この弱結合型ジョセフソン素子
は、基板上に超電導薄膜を形成し、弱結合部を形成する
だけの簡単なプロセスで作製できるが、弱結合部分での
結晶粒の大きさや形によって素子特性が大きく変化して
しまうという問題がある。この問題を解決する為に、２
枚の単結晶の結晶方位を変化させて接合し、その接合部
分を利用したジョセフソン素子も試作されている（例え
ば、R.Gross,etal.,Appl.Phys.Lett.,57,727(1990)参
照）。[0003] In addition to the stacked type Josephson element, a point contact type and a weak coupling type Josephson element are also known. In particular, a weak coupling type Josephson element has been actively studied. This weak-coupling type Josephson device can be manufactured by a simple process of forming a superconducting thin film on a substrate and forming a weak-coupling portion.However, device characteristics are large due to the size and shape of crystal grains at the weak-coupling portion. There is a problem that it changes. To solve this problem,
A single Josephson element is joined by changing the crystal orientation, and a Josephson element using the joint is also being trial manufactured (see, for example, R. Gross, et al., Appl. Phys. Lett., 57, 727 (1990)). ).
【０００４】[0004]
【発明が解決しようとしている課題】しかしながら、弱
結合型ジョセフソン素子では、２枚の単結晶を接合する
為に、ある結晶面に対して特定の角度（例えば、１〜２
０。程度）に研磨して、それを接合しなければならな
い。この基板としては、通常ＭｇＯやＳｒＴｉＯ3等が
使用されるが、これらの材料を接合するためには、精密
な研磨が必要であるばかりでなく、１，０００℃以上の
高温と場合によっては高圧熱処理が必要である。又、弱
結合部は接合面部分にしか形成できない為に、素子の集
積化や大面積化が困難であるという問題もある。更に、
低温と室温との間での熱サイクルによって、接合面から
基板が剥離し易いという問題点もある。However, in the weakly-coupled Josephson element, a specific angle (for example, 1 to 2) with respect to a certain crystal plane is required to join two single crystals.
0 . ) And must be joined. As this substrate, MgO, SrTiO 3 or the like is usually used. In order to join these materials, not only precise polishing is required, but also a high temperature of 1,000 ° C. or more and a high pressure in some cases. Heat treatment is required. In addition, since the weak coupling portion can be formed only at the bonding surface, there is a problem that it is difficult to integrate elements and increase the area. Furthermore,
There is also a problem that the substrate is easily peeled from the bonding surface due to a thermal cycle between a low temperature and a room temperature.
【０００５】一方、積層型ジョセフソン素子では、臨界
温度が高い酸化物超電導体薄膜を形成する為に、通常、
６００〜１，０００℃の温度が必要である。その為に、
基板と超電導薄膜、超電導薄膜とバリア層等との界面に
おける原子拡散、熱応力等により、素子特性、再現性、
信頼性等に問題があった。又、超電導層とバリア層の材
料の組み合わせにも問題があり、例えば、Ｙ系材料では
バリア層にＭｇＯやＹ2Ｏ3等が使用されることが多い。
これらのバリア層の格子定数の１つをＡとし、Ｙ系材料
の格子定数の１つをＢとすると、超電導層とバリア層の
格子整合性は、下記の式（１）で評価することが出来
る。 Ｑ＝｛ａＡ（１＋ｎ2）1/2｝／｛ｂＢ（１＋ｍ2）1/2｝・・・・・（１） （ａ、ｂは１又は２を表し、ｎ、ｍは０以上の任意の整
数を表す）Ｑの値が１．００に近い程、格子整合性はよ
いことになるが、Ｙ系材料の場合、ＭｇＯではＱ＝０．
９６〜０．９８、Ｙ2Ｏ3ではＱ＝０．９６〜０．９８で
ある。これまでの多くの研究において、積層型ジョセフ
ソン素子が良好な動作を示さないのは、前記のようなＭ
ｇＯ等でのＱ値では格子の整合性が不十分であり、より
整合性のよい材料の組合せが必要なことを示している。On the other hand, in a stacked Josephson device, an oxide superconductor thin film having a high critical temperature is usually formed.
Temperatures between 600 and 1,000 ° C are required. For that,
Due to atomic diffusion, thermal stress, etc. at the interface between the substrate and the superconducting thin film, between the superconducting thin film and the barrier layer, etc.
There was a problem in reliability etc. There is also a problem with the combination of the materials of the superconducting layer and the barrier layer. For example, in the case of Y-based materials, MgO or Y 2 O 3 is often used for the barrier layer.
Assuming that one of the lattice constants of these barrier layers is A and one of the lattice constants of the Y-based material is B, the lattice matching between the superconducting layer and the barrier layer can be evaluated by the following equation (1). I can do it. Q = {aA (1 + n 2 ) 1/2 } / {bB (1 + m 2 ) 1/2 } (1) (a and b represent 1 or 2, n and m are arbitrary numbers of 0 or more) The closer the value of Q is to 1.00, the better the lattice matching is, but in the case of a Y-based material, Mg = 0.
96 to 0.98, and Q = from 0.96 to 0.98 in the Y 2 O 3. In many studies to date, stacked Josephson devices do not perform well because of the M
The Q value of gO or the like is insufficient in lattice matching, indicating that a combination of materials having better matching is required.
【０００６】一般に、格子整合性の悪い材料を組み合わ
せると、超電導層とバリア層の結晶性は悪くなる。この
為に、得られたジョセフソン素子の特性も悪くなってし
まう。例えば、基板上に第一の超電導層、バリア層、第
二の超電導層を順次形成すると、第一の超電導層とバリ
ア層の整合性が悪いとバリア層の結晶格子が乱れ、バリ
ア層の結晶性、特に界面付近の結晶性が悪くなる。この
バリア層の上に第二の超電導層を形成すると第二の超電
導層の結晶性も悪くなる。この為に、ジョセフソン素子
の超電導層は、バルクに比較して超電導特性が悪くな
る。さらには第一と第二の超電導層に同じ超電導材料を
用いても、第一と第二の層では異なる超電導特性（例え
ば、臨界温度）を示すことも多い。積層型ジョセフソン
素子では、超電導層とバリア層の界面が重要であるか
ら、格子の不整合による界面の乱れは重大な問題であ
る。In general, when a material having poor lattice matching is combined, the crystallinity of the superconducting layer and the barrier layer deteriorates. For this reason, the characteristics of the obtained Josephson device deteriorate. For example, when a first superconducting layer, a barrier layer, and a second superconducting layer are sequentially formed on a substrate, if the matching between the first superconducting layer and the barrier layer is poor, the crystal lattice of the barrier layer is disturbed, and the crystal of the barrier layer is disturbed. , Especially the crystallinity near the interface is deteriorated. When the second superconducting layer is formed on this barrier layer, the crystallinity of the second superconducting layer also deteriorates. For this reason, the superconducting layer of the Josephson device has poor superconducting characteristics as compared with the bulk. Furthermore, even if the same superconducting material is used for the first and second superconducting layers, the first and second layers often exhibit different superconducting properties (for example, critical temperatures). In the stacked Josephson device, the interface between the superconducting layer and the barrier layer is important, so that the disorder of the interface due to lattice mismatch is a serious problem.
【０００７】界面が重要な積層型ジョセフソン素子で
は、超電導層の表面の安定性も重要である。表面が不安
定な超電導体を用いた場合には、どの様に素子を形成し
たとしても安定な界面を形成することは難しい。従来の
酸化物超電導体の中では、Ｙ系材料は表面が不安定であ
ることが知られている。即ち、この様な材料では、超電
導層とバリア層を異なる装置で形成する場合には、作製
途中の素子を一度大気中に出す必要が生じる。その結
果、大気中の水蒸気や炭酸ガスによって超電導層の表面
が変質し、界面は不安定となって素子特性や再現性が悪
くなってしまう。又、超電導層とバリア層を同じ装置で
形成する場合でも、酸素濃度や基板温度等の夫々の成膜
条件が異なる為に、超電導層表面から結晶中の酸素の脱
離等が生じて表面が変質してしまい、素子特性が悪くな
る。[0007] In the stacked Josephson device in which the interface is important, the stability of the surface of the superconducting layer is also important. When a superconductor with an unstable surface is used,
It is difficult to be that form a stable interface. It is known that among conventional oxide superconductors, the surface of a Y-based material is unstable. That is, in the case of using such a material, when the superconducting layer and the barrier layer are formed by different devices, it is necessary to once bring out the device in the process of being manufactured to the atmosphere. As a result, the surface of the superconducting layer is altered by water vapor or carbon dioxide gas in the atmosphere, the interface becomes unstable, and the element characteristics and reproducibility deteriorate. Further, even when the superconducting layer and the barrier layer are formed by the same apparatus, since the respective film forming conditions such as the oxygen concentration and the substrate temperature are different, desorption of oxygen in the crystal from the superconducting layer surface occurs and the surface is formed. It is deteriorated, and the device characteristics are deteriorated.
【０００８】又、Ｂｉ系材料は、Ｙ系材料より安定であ
るといわれているが、水蒸気中で耐久試験を行うと、分
解してしまうことが、本発明者らにより既に報告されて
いる（第４９回応用物理学会秋季大会、６ｐ−館Ａ−１
２、予稿集１２２頁参照）。又、Ｔｌ系やＨｇ系材料
は、いずれも有害金属を含んでおり、地球環境問題を考
えた時には、これらの材料は使用すべきものではない。The Bi-based material is said to be more stable than the Y-based material, but it has already been reported by the present inventors that it decomposes when subjected to a durability test in water vapor ( 49th Autumn Meeting of the Japan Society of Applied Physics, 6p-kan A-1
2, Proceedings, p. 122). Further, both Tl-based and Hg-based materials contain harmful metals, and when considering global environmental problems, these materials should not be used.
【０００９】更に、Ｂｉ系、Ｔｌ系やＨｇ系材料では、
異なる臨界温度を有する複数の超電導相が共存すること
が知られている。例えば、Ｂｉ系では、８０及び１０５
Ｋ、Ｔ１系では９０、１１０及び１２５Ｋの臨界温度を
示す結晶相が知られている。この為、ジョセフソン素子
を作製した場合には、これらの結晶相が共存する為に素
子特性が安定しないという問題がある。この様に、従来
のジョセフソン素子では、超電導層とバリア層の界面に
関連する諸問題がある為に、良好な特性を示す積層型ジ
ョセフソン素子が再現性よく得られないという問題があ
った。従って本発明の目的は、上記従来技術の問題点を
解決し、良好な積層型ジョセフソン素子特性を有する積
層型ジョセフソン素子を再現性よく提供することにあ
る。Further, for Bi-based, Tl-based and Hg-based materials,
It is known that a plurality of superconducting phases having different critical temperatures coexist. For example, in the Bi system, 80 and 105
Crystal phases exhibiting critical temperatures of 90, 110 and 125 K in the K and T1 systems are known. Therefore, when a Josephson device is manufactured, there is a problem that device characteristics are not stable because these crystal phases coexist. As described above, in the conventional Josephson device, there is a problem related to the interface between the superconducting layer and the barrier layer, and therefore, there is a problem that a laminated Josephson device exhibiting good characteristics cannot be obtained with good reproducibility. . SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art and to provide a stacked Josephson device having good stacked Josephson device characteristics with good reproducibility.
【００１０】[0010]
【課題を解決する為の手段】上記目的は以下の本発明に
よって達成される。即ち、本発明は、第一及び第二の超
電導層でバリア層を挟んだ構造を有する積層型ジョセフ
ソン素子において、第一及び第二の超電導層が、一般式
Ｌｎ1-xＣａxＳｒ2Ｃｕ3-yＭyＯ6+z（ＬｎはＹ若しくは
ランタノイド元素であり、ＭはＴｉ、Ｖ、Ｆｅ、Ｃｏ、
Ｇｅ、Ｍｏ、Ｗ及びＲｅの元素群から選ばれた１種類以
上の元素であり、０≦ｘ≦０．６、０．０５≦ｙ≦１、
０≦ｚ≦３）で表されるペロブスカイト型構造の複合酸
化物であり、前記バリア層がＬｎ、Ｓｒ、Ｃａ、Ｃｕ及
びＭの元素群から選ばれた少なくとも２種類の元素を含
む酸化物であり、第一又は第二の超電導層とバリア層の
界面において、第一又は第二の超電導層の表面結晶層の
格子間隔をＢとし、バリア層の格子定数の１つをＡとす
るとき、ＡとＢが関係式 ０．９９≦｛ａＡ（１＋ｎ 2 ） 1/2 ｝／｛ｂＢ（１＋
ｍ 2 ） 1/2 ｝≦１．０２ （ａ、ｂは１又は２であり、ｎ、ｍは０以上の任意の整
数である）を満たすｎ及びｍを選ぶことが可能な ことを
特徴とする積層型ジョセフソン素子である。The above objects are achieved by the present invention described below. That is, the present invention provides a multilayer Josephson device having a structure in which a barrier layer is sandwiched between first and second superconducting layers, wherein the first and second superconducting layers have the general formula Ln 1-x Ca x Sr 2 Cu 3-y M y O 6 + z (Ln is Y or a lanthanoid element, M is Ti, V, Fe, Co,
At least one element selected from the group consisting of Ge, Mo, W and Re, where 0 ≦ x ≦ 0.6, 0.05 ≦ y ≦ 1,
0 ≦ z ≦ 3), wherein the barrier layer is an oxide containing at least two elements selected from the group consisting of Ln, Sr, Ca, Cu and M. Ah is, the first or second superconducting layer and the barrier layer
At the interface, the surface crystal layer of the first or second superconducting layer
Let the lattice spacing be B and one of the lattice constants of the barrier layer be A
A and B satisfy the relational expression 0.99 ≦ {aA (1 + n 2 ) 1/2 } / {bB (1+
m 2 ) 1/2 } ≦ 1.02 (a and b are 1 or 2; n and m are arbitrary integers of 0 or more.
(A number) that can select n and m .
【００１１】[0011]
【作用】本発明では、上記した従来技術の問題を超電導
層とバリア層に使用する材料を特定範囲の組成を有する
材料にすることによって解決する。即ち、超電導層に表
面が安定であり且つ単一の結晶相の超電導材料を用い、
又、バリア層に、超電導層と結晶格子の整合性がよい材
料を用いることにより本発明の目的が達成される。According to the present invention, the above-mentioned problems of the prior art are solved by changing the materials used for the superconducting layer and the barrier layer to materials having a specific range of composition. That is, the surface of the superconducting layer is stable and uses a superconducting material of a single crystal phase,
Further, the object of the present invention can be achieved by using a material having good matching between the superconducting layer and the crystal lattice for the barrier layer.
【００１２】[0012]
【好ましい実施態様】本発明の、積層型ジョセフソン素
子は、第一及び第二の超電導層でバリア層を挟んだ構造
を有する積層型ジョセフソン素子であって、第一及び第
二の超電導層が、一般式、Ｌｎ1-xＣａxＳｒ2Ｃｕ3-yＭ
yＯ6+z（ＬｎはＹ若しくはランタノイド元素であり、Ｍ
はＴｉ、Ｖ、Ｆｅ、Ｃｏ、Ｇｅ、Ｍｏ、Ｗ及びＲｅの元
素群から選ばれた１種類以上の元素であり、０≦ｘ≦
０．６、０．０５≦ｙ≦１、０≦ｚ≦３）で表されるペ
ロブスカイト型構造の複合酸化物からなり、バリア層が
Ｌｎ、Ｓｒ、Ｃａ、Ｃｕ及びＭの元素群から選ばれた少
なくとも２種類の元素を含む酸化物であることを特徴と
する。The laminated Josephson element of the present invention is a laminated Josephson element having a structure in which a barrier layer is sandwiched between first and second superconducting layers, wherein the first and second superconducting layers Has the general formula: Ln 1-x Ca x Sr 2 Cu 3-y M
y O 6 + z (Ln is Y or a lanthanoid element, M
Is one or more elements selected from the group consisting of Ti, V, Fe, Co, Ge, Mo, W and Re, and 0 ≦ x ≦
0.6, 0.05 ≦ y ≦ 1, 0 ≦ z ≦ 3), composed of a complex oxide having a perovskite structure, wherein the barrier layer is selected from the element group of Ln, Sr, Ca, Cu and M. And an oxide containing at least two types of elements.
【００１３】本発明で超電導層に使用する材料として
は、例えば、Ｌｎ＝Ｙであるときの代表的なものとして
は下記表１のものが挙げられる。尚、各構成元素の比率
は、酸化物又は炭酸塩等の原料から焼結体を作製し、こ
の焼結体をＥＰＭＡにより組成分析した時の平均値であ
る。酸素量に関しては±２０％程度の、その他の元素に
ついては±５％程度の測定誤差を夫々含んでいる。As a material used for the superconducting layer in the present invention, for example, when Ln = Y, typical ones shown in the following Table 1 can be mentioned. The ratio of each constituent element is an average value when a sintered body is prepared from a raw material such as an oxide or a carbonate and the composition of the sintered body is analyzed by EPMA. The oxygen content contains a measurement error of about ± 20%, and the other elements contain a measurement error of about ± 5%.
【００１４】[0014]
【表１】 [Table 1]
【００１５】又、一般式（１）中のＭをＭ＝Ｆｅとした
ＹＳｒ2Ｃｕ2.65Ｆｅ0.35Ｏ7材料のの電気抵抗の温度依
存性、磁化率の温度依存性及びＸ線回折図形を図２〜図
４に示した。これらの結果から、この材料は臨界温度
（Ｔｃ）が５１Ｋ、格子定数がａ＝ｂ＝３．８１Å、ｃ
＝１１．４Åの正方晶であることがわかる。更に図４の
Ｘ線回折図形には正方晶以外の結晶相に対応するピーク
が観察されないことから単相であることが確認された。The temperature dependence of the electrical resistance, the temperature dependence of the magnetic susceptibility, and the X-ray diffraction pattern of a YSr 2 Cu 2.65 Fe 0.35 O 7 material where M in the general formula (1) is M = Fe are shown. 2 to 4. From these results, this material has a critical temperature (Tc) of 51 K, a lattice constant of a = b = 3.81 °, c
It can be seen that this is a tetragonal crystal of = 11.4 °. Further, since no peak corresponding to a crystal phase other than tetragonal was observed in the X-ray diffraction pattern of FIG. 4, it was confirmed that the phase was a single phase.
【００１６】本発明で用いる超電導材料の表面の安定性
を調べる為に、以下の様な耐久性試験を行った。焼結体
試料を粉末にし、これを４０℃の飽和水蒸気中に入れ、
１週間放置し、その前後における結晶構造の変化をＸ線
回折測定によって調べた。この結果、本発明で使用する
材料、例えば、ＹＳｒ2Ｃｕ2.65Ｆｅ0.35Ｏ7は、図５に
示した様に、１週間放置後も変化が認められなかった。
本発明で使用する他のＹ系材料についても耐久試験を行
ったが、いずれも変化は認められなかった。In order to examine the surface stability of the superconducting material used in the present invention, the following durability test was performed. A sintered body sample is made into a powder, and this is put into saturated steam at 40 ° C.
It was left for one week, and the change in the crystal structure before and after that was examined by X-ray diffraction measurement. As a result, no change was observed in the material used in the present invention, for example, YSr 2 Cu 2.65 Fe 0.35 O 7 even after one week of standing as shown in FIG.
Durability tests were also performed on other Y-based materials used in the present invention, and no change was observed in any of them.
【００１７】これに対し、従来の代表的なＹ系材料であ
るＹＢａ2Ｃｕ3Ｏ7-Xでは、耐久試験開始後数時間で試
料表面に白色物質が析出し始め、３日後にはほぼ完全に
分解してしまった。試験開始前及び試験開始１週間後の
耐久性試験の結果を図６に示したが、結晶構造が変化し
ていることが分かる。尚、この材料では、３日間経過後
のＸ線回折図形は、いずれも図６とほぼ同じＸ線回折図
形を示し、３日経過後は回折図形にはほとんど変化が認
められなかった。On the other hand, in the case of YBa 2 Cu 3 O 7-X , which is a conventional representative Y-based material, a white substance starts to precipitate on the sample surface within several hours after the end of the endurance test, and almost completely after three days. Has been disassembled. The results of the durability test before the start of the test and one week after the start of the test are shown in FIG. 6, and it can be seen that the crystal structure has changed. In this material, the X-ray diffraction patterns after three days had almost the same X-ray diffraction patterns as shown in FIG. 6, and after three days had hardly changed.
【００１８】次に、本発明で用いるバリア層形成材料
は、上記した超電導層に含まれる元素、即ち、Ｙ、ラン
タノイド元素、Ｃａ、Ｓｒ、Ｃｕ、Ｔｉ、Ｖ、Ｆｅ、Ｃ
ｏ、Ｇｅ、Ｍｏ、Ｗ及びＲｅの中から選ばれた少なくと
も２種類を構成元素とする酸化物である。バリア層形成
に使用する２種類の元素の酸化物の代表例を表２に示し
た。Next, the barrier layer forming material used in the present invention is composed of the elements contained in the above-described superconducting layer, ie, Y, lanthanoid elements, Ca, Sr, Cu, Ti, V, Fe, C
An oxide containing at least two members selected from among o, Ge, Mo, W, and Re as constituent elements. Table 2 shows typical examples of the oxides of the two elements used for forming the barrier layer.
【００１９】[0019]
【表２】 [Table 2]
【００２０】例えば、Ｓｒ2Ｆｅ2Ｏ5の結晶構造は、格
子定数ａ＝３．８６Åの立方晶である。従って、超電導
層に前記したＹＳｒ2Ｃｕ2.65Ｆｅ0.35Ｏ7材料を使用し
た場合には、前述の式（１）より、Ｑ＝１．０１（ａ1
＝ｂ1＝１、ｎ＝ｍ＝１）となり、従来バリア層に使用
されていたＭｇＯのＱ＝０．９６〜０．９８よりもＱの
値は１に近くなる。この為に、超電導層とバリア層の界
面において格子の不整合から発生する応力は、ＭｇＯよ
りも、Ｓｒ2Ｆｅ2Ｏ5の方が小さくなると考えられる。
従って、本発明においては、Ｑの値が０．９９〜１．０
２の範囲となる超電導材料とバリア層形成材料とを組み
合わせることによって良好な安定性及び特性を有する積
層型ジョセフソン素子が得られる。尚、本発明におい
て、格子定数は粉末Ｘ線回折図形より決定した。For example, the crystal structure of Sr 2 Fe 2 O 5 is a cubic crystal having a lattice constant a = 3.86 °. Accordingly, when the above-mentioned YSr 2 Cu 2.65 Fe 0.35 O 7 material is used for the superconducting layer, Q = 1.01 (a 1
= B 1 = 1, n = m = 1), and the value of Q is closer to 1 than that of Mg = 0.96 to 0.98 used in the conventional barrier layer. For this reason, it is considered that the stress generated due to lattice mismatch at the interface between the superconducting layer and the barrier layer is smaller in Sr 2 Fe 2 O 5 than in MgO.
Therefore, in the present invention, the value of Q is 0.99 to 1.0.
By combining a superconducting material having a range of 2 and a barrier layer forming material, a laminated Josephson device having good stability and characteristics can be obtained. In the present invention, the lattice constant was determined from a powder X-ray diffraction pattern.
【００２１】又、本発明においては、超導電層及び／又
はバリア層形成材料を加圧処理してもよい。処理条件は
特に制限されないが、各材料は酸化物であるから、雰囲
気によっては材料中の酸素量が変化し、電気的特性が変
化することもある。酸素が不足し易い場合には、酸化雰
囲気中で、例えば、オートクレーブやＨＩＰ等の高圧処
理装置を用いて材料中の酸素量を調整することが出来
る。この高圧処理は、積層型ジョセフソン素子を形成す
る中間段階で行っても、素子形成後に行ってもよい。In the present invention, the material for forming the superconductive layer and / or the barrier layer may be subjected to a pressure treatment. Although the processing conditions are not particularly limited, since each material is an oxide, the amount of oxygen in the material may change depending on the atmosphere, and the electrical characteristics may change. When oxygen is insufficient, the amount of oxygen in the material can be adjusted in an oxidizing atmosphere using a high-pressure processing device such as an autoclave or HIP. This high-pressure treatment may be performed at an intermediate stage of forming the stacked Josephson device or after the device is formed.
【００２２】[0022]
【実施例】次に実施例を挙げて本発明を更に具体的に説
明する。 実施例１ 第一及び第二の超電導層の材料としてＹＳｒ2Ｃｕ2.65
Ｆｅ0.35Ｏ7を用い、バリア層の材料としてＳｒ2Ｆｅ2
Ｏ5を用いた。図１に本実施例の積層型ジョセフソン素
子の概略図を示す。図中、１はＳｒＴｉＯ3基板、２は
第一の超電導層、３はバリア層、４は第二の超電導層で
ある。先ず、マグネトロンスパッタ法で、第一の超電導
層２を厚み４００ｎｍ、バリア層３を厚み２．５ｎｍ、
第二の超電導層４を厚み３００ｎｍの厚さに順に形成し
た。この様に作製した第一の超電導層２／バリア層３／
第二の超電導層４の積層薄膜に対して、通常のフォトリ
ソグラフィー技術を用いて加工を行い、図１に示す様な
本発明の積層型ジョセフソン素子を作製した。Next, the present invention will be described more specifically with reference to examples. Example 1 YSr 2 Cu 2.65 as a material for the first and second superconducting layers
Fe 0.35 O 7 is used, and Sr 2 Fe 2
The O 5 was used. FIG. 1 is a schematic view of the stacked Josephson device of this embodiment. In the figure, 1 is a SrTiO 3 substrate, 2 is a first superconducting layer, 3 is a barrier layer, and 4 is a second superconducting layer. First, the thickness of the first superconducting layer 2 is 400 nm and the thickness of the barrier layer 3 is 2.5 nm by magnetron sputtering.
The second superconducting layer 4 was sequentially formed to a thickness of 300 nm. The first superconducting layer 2 / barrier layer 3 /
The laminated thin film of the second superconducting layer 4 was processed using ordinary photolithography technology to produce a laminated Josephson device of the present invention as shown in FIG.
【００２３】この様にして作製した素子の各超電導層の
電気抵抗の温度依存性を、通常の直流４端子法により測
定した。尚、第一の超導電層は図１のジョセフソン素子
が形成されていない部分で、第二の超導電層はジョセフ
ソン素子を形成する前のパターニングを行う前に測定し
た。いずれの超導電層も図２と同じような電気抵抗の温
度依存性を示し、臨界温度は第一の超導電層が５１Ｋ、
第二の超導電層が５０Ｋであった。The temperature dependence of the electric resistance of each superconducting layer of the device thus manufactured was measured by the usual direct current four-terminal method. The first superconductive layer was a portion where the Josephson element of FIG. 1 was not formed, and the second superconductive layer was measured before patterning before forming the Josephson element. Each of the superconducting layers exhibits the same temperature dependence of electric resistance as in FIG. 2, and the critical temperature is 51K for the first superconducting layer,
The second superconductive layer was 50K.
【００２４】このような本発明の素子は、４０Ｋで図７
に示す様な電流−電圧特性を示し、積層型ジョセフソン
素子として良好に動作した。一方、ＳｒＴｉＯ3基板を
用いてＹＢａ2Ｃｕ3Ｏ7-Xを第一及び第二の超電導層と
し、ＭｇＯをバリア層とした場合には、第一の超電導層
の臨界温度は８９Ｋであったが、第二の超電導層の臨界
温度は５３Ｋに低下した。この素子の電流−電圧特性
は、図８の様であった。この結果、第一及び第二の各超
電導層とバリア層との積層構造が不完全であることを示
している。Such a device according to the present invention has a structure shown in FIG.
The current-voltage characteristics as shown in FIG. 1 were exhibited, and the device operated well as a stacked Josephson device. On the other hand, when the YBa 2 Cu 3 O 7-X was used as the first and second superconducting layers and the MgO was used as the barrier layer using the SrTiO 3 substrate, the critical temperature of the first superconducting layer was 89K. However, the critical temperature of the second superconducting layer dropped to 53K. The current-voltage characteristics of this device were as shown in FIG. This indicates that the laminated structure of the first and second superconducting layers and the barrier layer is incomplete.
【００２５】実施例２ 第一及び第二の超電導層の材料としてＥｒ0.9Ｃａ0.1Ｓ
ｒ2Ｃｕ2.85Ｍｏ0.15Ｏ7を用い、バリア層の材料として
ＳｒＭｏＯ4を用いた。マグネトロンスパッタ法でＭｇ
Ｏ基板上に、第一の超電導層２を厚み３００ｎｍ、バリ
ア層３を厚み２．４ｎｍ、第二の超電導層４を厚み２０
０ｎｍに順に形成した。この様に形成した積層薄膜に対
して、通常のフォトリソグラフィー技術を用いて加工を
行い、図１に示す様な本発明の積層型ジョセフソン素子
を作製した。第一及び第二の超電導層の臨界温度は６９
Ｋと同じであり、この様にして作製した素子も、図７と
同じ様な図形の電流−電圧特性を示し、積層型ジョセフ
ソン素子として良好に動作した。Example 2 Er 0.9 Ca 0.1 S was used as a material for the first and second superconducting layers.
r 2 Cu 2.85 Mo 0.15 O 7 was used, and SrMoO 4 was used as a material for the barrier layer. Mg by magnetron sputtering
On the O substrate, the first superconducting layer 2 has a thickness of 300 nm, the barrier layer 3 has a thickness of 2.4 nm, and the second superconducting layer 4 has a thickness of 20 nm.
The layers were sequentially formed at 0 nm. The laminated thin film thus formed was processed by using ordinary photolithography technology to produce a laminated Josephson device of the present invention as shown in FIG. The critical temperature of the first and second superconducting layers is 69
K was the same as that of K, and the element fabricated in this manner also showed current-voltage characteristics of the same figure as in FIG. 7 and operated well as a stacked Josephson element.
【００２６】実施例３ 図９に本発明の積層型ジョセフソン素子の断面構成図を
示した。１はＭｇＯ基板、２は第一の超電導層、３はバ
リア層、４は第二の超電導層である。第一の超電導層を
レーザーアブレーション法により成膜し、これを図１の
様にパターニングし、その後、バリア層と第二超電導層
を形成した。第一及び第二の超電導層は、夫々４５０及
び３００ｎｍの厚さであり、バリア層は１．５ｎｍの厚
さである。素子を形成する為のパターニングは、通常の
フォトリソグラフィーで行った。本実施例では、第一及
び第二の超電導層には夫々、Ｙ0.9Ｃａ0.1Ｓｒ2Ｃｕ
2.85Ｍｏ0.15Ｏ7及びＥｒ0.9Ｃａ0.1Ｓｒ2Ｃｕ2.85Ｍｏ
0.15Ｏ7を用いた。バリア層にはＰｒ1.6Ｓｒ0.4ＣｕＯ
4-Xを用いた。Embodiment 3 FIG. 9 shows a cross-sectional view of a stacked Josephson device of the present invention. 1 is an MgO substrate, 2 is a first superconducting layer, 3 is a barrier layer, and 4 is a second superconducting layer. A first superconducting layer was formed by a laser ablation method, and was patterned as shown in FIG. 1, and thereafter, a barrier layer and a second superconducting layer were formed. The first and second superconducting layers are 450 and 300 nm thick, respectively, and the barrier layer is 1.5 nm thick. Patterning for forming the element was performed by ordinary photolithography. In this embodiment, the first and second superconducting layers respectively, Y 0.9 Ca 0.1 Sr 2 Cu
2.85 Mo 0.15 O 7 and Er 0.9 Ca 0.1 Sr 2 Cu 2.85 Mo
0.15 O 7 was used. The barrier layer is Pr 1.6 Sr 0.4 CuO
4-X was used.
【００２７】この材料の組み合わせでは、第一の超電導
層とバリア層にに対するＱ値は１．００７と、第二の超
導電層とバリア層に対するＱ値は１．００６となる。
又、第一及び第二の超電導層の臨界温度は、夫々６５Ｋ
及び６９Ｋであった。本実施例で使用した第一の超伝導
層の臨界温度が表１に示したバルク焼結体よりも３Ｋ低
いのは、基板ＭｇＯとの格子整合性が悪い為であると推
測される。これに対して、第二の超電導層の臨界温度は
バルク焼結体と同じであり、これはバリア層との格子整
合性がよい為であると考えられる。上記で得られた本実
施例の積層型ジョセフソン素子を液体ヘリウムで冷却し
て電流−電圧特性を測定したところ、図７と同じパター
ンを示し、良好に動作することが確認された。With this combination of materials, the Q value for the first superconducting layer and the barrier layer is 1.007, and the Q value for the second superconducting layer and the barrier layer is 1.006.
The critical temperature of the first and second superconducting layers is 65K, respectively.
And 69K. It is presumed that the critical temperature of the first superconducting layer used in this example is lower by 3K than that of the bulk sintered body shown in Table 1 due to poor lattice matching with the substrate MgO. On the other hand, the critical temperature of the second superconducting layer is the same as that of the bulk sintered body, which is considered to be due to good lattice matching with the barrier layer. The multilayer Josephson device of the present example obtained above was cooled with liquid helium, and the current-voltage characteristics were measured. As a result, it showed the same pattern as in FIG. 7 and it was confirmed that the device operated well.
【００２８】実施例４ 第一及び第二の超導電層形成材料としてＹＳｒ2Ｃｕ2.7
Ｔｉ0.3Ｏ7を、バリア層形成材料としてＬａ0.75Ｙ0.95
Ｓｒ1.3Ｃｕ2Ｏ6を用いた。第一の超導電性を形成する
基板は、ＬａＡｌＯ3である。以上の材料の組み合わせ
により、図９に示すような構成の積層型ジョセフソン素
子を、レーザーアブレーション法によって形成した。パ
ターニングは、通常のフォトリソグラフィーにより行っ
た。この様にして作製した素子において、基板と第一の
超導電層、第一の超導電層とバリア層及びバリア層と第
二の超導電層における格子整合性を示すＱ値は、夫々
０．９９５、０．９９８及び０．９９９であった。又、
第一及び第二の超電導層の臨界温度は、いずれも３４Ｋ
であり、薄膜形成と素子化による臨界温度の低下は見ら
れなかった。この素子の電流−電圧特性は、図７と同じ
様にトンネル型ジョセフソン接合特性を示し、室温と液
体ヘリウク温度（４．２Ｋ）の間で、３００Ｋ／ｍｉｎ
の割合で、室温→４．２Ｋ→室温の順で連続１００回降
温、昇温のサイクルを繰り返しても基板からの素子の剥
離や超電導層とバリア層との剥離等は発生しなかった。Example 4 YSr 2 Cu 2.7 as the first and second superconductive layer forming materials
Ti 0.3 O 7 was used as a barrier layer forming material with La 0.75 Y 0.95
Sr 1.3 Cu 2 O 6 was used. Substrate to form the first super-conductivity is LaAlO 3. With the combination of the above materials, a laminated Josephson device having a configuration as shown in FIG. 9 was formed by a laser ablation method. The patterning was performed by ordinary photolithography. In the device manufactured in this way, the Q values indicating the lattice matching between the substrate and the first superconductive layer, between the first superconductive layer and the barrier layer, and between the barrier layer and the second superconductive layer are each 0. 995, 0.998 and 0.999. or,
The critical temperature of each of the first and second superconducting layers is 34 K
No decrease in critical temperature due to thin film formation and device fabrication was observed. The current-voltage characteristic of this element shows a tunnel-type Josephson junction characteristic as in FIG. 7, and is 300 K / min between room temperature and liquid Heliuk temperature (4.2 K).
Even when the cycle of cooling and heating was repeated 100 times in the order of room temperature → 4.2 K → room temperature, peeling of the element from the substrate and peeling between the superconducting layer and the barrier layer did not occur.
【００２９】実施例５ ＨｏＳｒ2Ｃｕ2.9Ｗ0.1Ｏ7.1を第一及び第二の超電導層
形成材料として、バリア層形成材料としてＳｒＷＯ4を
用いた。ＭｇＯ単結晶上にＰｒ1.0Ｈｏ0.6Ｓｒ0.4Ｃｕ
Ｏ4-xの薄膜をマグネトロンスパッタ法で形成し、次い
でオートクレーブ中で６００℃、酸素中で１時間、１０
０気圧で加熱加圧処理してこれを基板に用いた。次に、
上記の材料を用い基板上に、各超電導層及びバリア層を
マグネトロンスパッタ法で形成した。これをＨＩＰ装置
により、８００℃、２時間、酸素を２０％含むアルゴン
雰囲気で２０００気圧の加圧処理を行った。その後、通
常のフォトリソグラフィー法でパターニングして図１に
示す積層型ジョセフソン素子を作製した。Example 5 HoSr 2 Cu 2.9 W 0.1 O 7.1 was used as the material for forming the first and second superconducting layers, and SrWO 4 was used as the material for forming the barrier layer. On MgO single crystal Pr 1.0 Ho 0.6 Sr 0.4 Cu
A thin film of O 4-x is formed by magnetron sputtering, and then placed in an autoclave at 600 ° C. for 1 hour in oxygen for 10 hours.
This was heated and pressurized at 0 atm and used as a substrate. next,
Each superconducting layer and barrier layer were formed on the substrate by the magnetron sputtering method using the above materials. This was subjected to a pressure treatment of 2,000 atm at 800 ° C. for 2 hours in an argon atmosphere containing 20% oxygen by a HIP apparatus. Thereafter, patterning was performed by a normal photolithography method to produce a stacked Josephson device shown in FIG.
【００３０】第一及び第二の超電導層の臨界温度は、Ｈ
ＩＰ装置での加熱加圧処理前では４２Ｋであったが、処
理後は６５Ｋとなった。又、ＨＩＰ処理後の格子整合性
を示すＱ値は、基板と第一超電導層、第一超電導層とバ
リア層、バリア層と第二超電導層の各界面に対して、夫
々１．００８、１．００１、０．９９９であった。ＨＩ
Ｐ処理前の膜厚は、第一超電導層は４００ｎｍ、バリア
層は２ｎｍ、第二超電導層は４００ｎｍであったが、Ｈ
ＩＰ処理後は、夫々、３８０ｎｍ、１．１ｎｍ及び３７
０ｎｍであった。この積層型ジョセフソン素子も、液体
ヘリウムで冷却すると図７の様な電流−電圧特性を示し
て、安定に動作した。又、室温と低温の間の温度変化に
も強く、５００Ｋ／ｍｉｎ程度の温度変化に対しても素
子の破壊や特性劣化は認められなかった。The critical temperature of the first and second superconducting layers is H
It was 42K before the heating and pressurizing treatment in the IP device, but it was 65K after the treatment. Further, the Q value indicating the lattice matching after the HIP processing is 1.008, 1.008 for the interface between the substrate and the first superconducting layer, the interface between the first superconducting layer and the barrier layer, and the interface between the barrier layer and the second superconducting layer, respectively. 0.001 and 0.999. HI
The film thickness before the P treatment was 400 nm for the first superconducting layer, 2 nm for the barrier layer, and 400 nm for the second superconducting layer.
After the IP treatment, 380 nm, 1.1 nm and 37 nm, respectively.
It was 0 nm. This multilayer Josephson element also exhibited stable current-voltage characteristics as shown in FIG. 7 when cooled with liquid helium, and operated stably. Further, it is resistant to a temperature change between room temperature and low temperature, and no destruction of the element and no deterioration of characteristics are observed even at a temperature change of about 500 K / min.
【００３１】[0031]
【発明の効果】以上の如く本発明によれば、表面の安定
した超電導材料と、この超電導材料に対して格子整合性
のよいバリア層形成材料を用いることにより、電気特性
に優れ、温度変化にも強い積層型ジョセフソン素子を得
ることが可能となった。As described above, according to the present invention, by using a superconducting material having a stable surface and a barrier layer forming material having good lattice matching with the superconducting material, the electric characteristics are excellent and the temperature change is prevented. It has become possible to obtain a laminated Josephson device which is also strong.
【図１】本発明の積層型ジョセフソン素子の一例を示す
概略断面構成図である。FIG. 1 is a schematic sectional view showing an example of a stacked Josephson device of the present invention.
【図２】本発明で使用する超電導材料の一例であるＹＳ
ｒ2Ｃｕ2.65Ｆｅ0.35Ｏ6+zの電気抵抗率の温度依存性を
示す図である。FIG. 2 shows YS which is an example of a superconducting material used in the present invention.
It is a diagram showing temperature dependence of electrical resistivity of the r 2 Cu 2.65 Fe 0.35 O 6 + z.
【図３】超電導材料の一例であるＹＳｒ2Ｃｕ2.65Ｆｅ
0.35Ｏ6+zの磁化率の温度依存性を示す図である。FIG. 3 shows an example of a superconducting material, YSr 2 Cu 2.65 Fe
It is a figure which shows the temperature dependence of the magnetic susceptibility of 0.35 O6 + z .
【図４】超電導材料の一例であるＹＳｒ2Ｃｕ2.65Ｆｅ
0.35Ｏ6+zのＸ線回折図形である。FIG. 4 shows YSr 2 Cu 2.65 Fe which is an example of a superconducting material.
It is an X-ray diffraction pattern of 0.35 O 6 + z .
【図５】本発明の材料ＹＳｒ2Ｃｕ2.65Ｆｅ0.35Ｏ6+zの
耐久性試験前後のＸ線回折図形である。FIG. 5 is an X-ray diffraction pattern before and after a durability test of a material YSr 2 Cu 2.65 Fe 0.35 O 6 + z of the present invention.
【図６】比較材料ＹＢａ2Ｃｕ3Ｏ7-xの耐久性試験前後
のＸ線回折図形である。FIG. 6 is an X-ray diffraction pattern of a comparative material YBa 2 Cu 3 O 7-x before and after a durability test.
【図７】本発明の積層型ジョセフソン素子の電流−電圧
特性のパターンを示す。FIG. 7 shows a current-voltage characteristic pattern of the stacked Josephson device of the present invention.
【図８】比較積層型ジョセフソン素子の電流−電圧特性
のパターンを示す。FIG. 8 shows a current-voltage characteristic pattern of a comparative stacked Josephson device.
【図９】本発明の他の積層型ジョセフソン素子の一例を
示す概略断面構成図である。FIG. 9 is a schematic cross-sectional configuration diagram showing an example of another laminated Josephson device of the present invention.
１：基板 ２：第一の超電導層 ３：バリア層 ４：第二の超電導層 1: substrate 2: first superconducting layer 3: barrier layer 4: second superconducting layer
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.7 識別記号 ＦＩ Ｃ０１Ｇ 39/00 Ｃ０１Ｇ 39/00 41/00 41/00 Ａ 49/00 ＺＡＡ 49/00 ＺＡＡＡ Ｃ２３Ｃ 14/08 ＺＡＡ Ｃ２３Ｃ 14/08 ＺＡＡＬ 14/34 ＺＡＡ 14/34 ＺＡＡＱ Ｈ０１Ｌ 39/02 ＺＡＡ Ｈ０１Ｌ 39/02 ＺＡＡＤ 39/12 ＺＡＡ 39/12 ＺＡＡＣ (56)参考文献 特開 昭63−283086（ＪＰ，Ａ) 特開 昭63−276284（ＪＰ，Ａ) 特開 平５−78102（ＪＰ，Ａ) 特開 平３−68180（ＪＰ，Ａ) (58)調査した分野(Int.Cl.7，ＤＢ名) H01L 39/22 ZAA C01G 1/00 C01G 3/00 ZAA C01G 23/00 ZAA C01G 31/00 C01G 39/00 C01G 41/00 C01G 49/00 ZAA C23C 14/08 ZAA C23C 14/34 ZAA H01L 39/02 ZAA H01L 39/12 ZAA H01L 39/24 ZAA H01L 39/00 ZAA ──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. 7 Identification code FI C01G 39/00 C01G 39/00 41/00 41/00 A 49/00 ZAA 49/00 ZAAA C23C 14/08 ZAA C23C 14/08 ZAAL 14/34 ZAA 14/34 ZAAQ H01L 39/02 ZAA H01L 39/02 ZAAD 39/12 ZAA 39/12 ZAAC (56) References JP-A-63-283086 (JP, A) JP-A-63-276284 ( JP, A) JP-A-5-78102 (JP, A) JP-A-3-68180 (JP, A) (58) Fields investigated (Int. Cl. 7 , DB name) H01L 39/22 ZAA C01G 1 / 00 C01G 3/00 ZAA C01G 23/00 ZAA C01G 31/00 C01G 39/00 C01G 41/00 C01G 49/00 ZAA C23C 14/08 ZAA C23C 14/34 ZAA H01L 39/02 ZAA H01L 39/12 ZAA H01L 39 / 24 ZAA H01L 39/00 ZAA
Claims (1)
んだ構造を有する積層型ジョセフソン素子において、第
一及び第二の超電導層が、一般式Ｌｎ1-xＣａxＳｒ2Ｃ
ｕ3-yＭyＯ6+z（ＬｎはＹ若しくはランタノイド元素で
あり、ＭはＴｉ、Ｖ、Ｆｅ、Ｃｏ、Ｇｅ、Ｍｏ、Ｗ及び
Ｒｅの元素群から選ばれた１種類以上の元素であり、０
≦ｘ≦０．６、０．０５≦ｙ≦１、０≦ｚ≦３）で表さ
れるペロブスカイト型構造の複合酸化物であり、前記バ
リア層がＬｎ、Ｓｒ、Ｃａ、Ｃｕ及びＭの元素群から選
ばれた少なくとも２種類の元素を含む酸化物であり、第
一又は第二の超電導層とバリア層の界面において、第一
又は第二の超電導層の表面結晶層の格子間隔をＢとし、
バリア層の格子定数の１つをＡとするとき、ＡとＢが関
係式 ０．９９≦｛ａＡ（１＋ｎ 2 ） 1/2 ｝／｛ｂＢ（１＋
ｍ 2 ） 1/2 ｝≦１．０２ （ａ、ｂは１又は２であり、ｎ、ｍは０以上の任意の整
数である）を満たすｎ及びｍを選ぶことが可能な ことを
特徴とする積層型ジョセフソン素子。1. A stacked Josephson device having a structure in which a barrier layer is sandwiched between first and second superconducting layers, wherein the first and second superconducting layers have a general formula of Ln 1-x Ca x Sr 2 C
u 3-y M y O 6 + z (Ln is Y or a lanthanoid element, M is Ti, V, Fe, Co, Ge, Mo, at least one element selected from the element group of W and Re Yes, 0
≦ x ≦ 0.6, 0.05 ≦ y ≦ 1, 0 ≦ z ≦ 3), wherein the barrier layer is an element of Ln, Sr, Ca, Cu and M Ri oxide der containing at least two elements selected from the group, the
At the interface between the first or second superconducting layer and the barrier layer, the first
Or, let B be the lattice spacing of the surface crystal layer of the second superconducting layer,
When one of the lattice constants of the barrier layer is A, A and B are related.
The equation 0.99 ≦ {aA (1 + n 2 ) 1/2 } / {bB (1+
m 2 ) 1/2 } ≦ 1.02 (a and b are 1 or 2; n and m are arbitrary integers of 0 or more.
(A number) that can select n and m .
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|---|---|---|---|
| JP07052042A JP3073142B2 (en) | 1994-02-18 | 1995-02-17 | Stacked Josephson device |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4339094 | 1994-02-18 | ||
| JP6-43390 | 1994-02-18 | ||
| JP07052042A JP3073142B2 (en) | 1994-02-18 | 1995-02-17 | Stacked Josephson device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH07283448A JPH07283448A (en) | 1995-10-27 |
| JP3073142B2 true JP3073142B2 (en) | 2000-08-07 |
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