JPH0461177A - Superconducting tunnel junction - Google Patents
Superconducting tunnel junctionInfo
- Publication number
- JPH0461177A JPH0461177A JP2164526A JP16452690A JPH0461177A JP H0461177 A JPH0461177 A JP H0461177A JP 2164526 A JP2164526 A JP 2164526A JP 16452690 A JP16452690 A JP 16452690A JP H0461177 A JPH0461177 A JP H0461177A
- Authority
- JP
- Japan
- Prior art keywords
- oxide superconductor
- electrode
- junction
- superconducting
- film
- 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.)
- Pending
Links
- 239000002887 superconductor Substances 0.000 claims abstract description 37
- 239000010409 thin film Substances 0.000 claims abstract description 17
- 239000010949 copper Substances 0.000 claims abstract description 10
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims abstract description 9
- 229910052802 copper Inorganic materials 0.000 claims abstract description 9
- 229910052751 metal Inorganic materials 0.000 claims abstract description 9
- 239000002184 metal Substances 0.000 claims abstract description 9
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 7
- 229910052797 bismuth Inorganic materials 0.000 claims abstract description 7
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 claims abstract description 7
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 7
- 239000001301 oxygen Substances 0.000 claims abstract description 7
- 229910052692 Dysprosium Inorganic materials 0.000 claims description 4
- 229910052693 Europium Inorganic materials 0.000 claims description 4
- 229910052688 Gadolinium Inorganic materials 0.000 claims description 4
- 229910052727 yttrium Inorganic materials 0.000 claims description 3
- 229910052689 Holmium Inorganic materials 0.000 claims description 2
- 229910015901 Bi-Sr-Ca-Cu-O Inorganic materials 0.000 claims 1
- 239000000758 substrate Substances 0.000 abstract description 14
- 238000000034 method Methods 0.000 abstract description 10
- 239000013078 crystal Substances 0.000 abstract description 9
- 230000007704 transition Effects 0.000 abstract description 4
- 238000005530 etching Methods 0.000 abstract description 3
- 238000004544 sputter deposition Methods 0.000 abstract description 3
- 238000000992 sputter etching Methods 0.000 abstract description 3
- 238000010549 co-Evaporation Methods 0.000 abstract description 2
- 238000010884 ion-beam technique Methods 0.000 abstract description 2
- 238000001552 radio frequency sputter deposition Methods 0.000 abstract description 2
- 238000000151 deposition Methods 0.000 description 6
- 230000004888 barrier function Effects 0.000 description 4
- 230000008021 deposition Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 239000010408 film Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 230000007547 defect Effects 0.000 description 2
- 238000000605 extraction Methods 0.000 description 2
- 229910052737 gold Inorganic materials 0.000 description 2
- 239000010931 gold Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- 230000005641 tunneling Effects 0.000 description 2
- 229910002480 Cu-O Inorganic materials 0.000 description 1
- 229910052691 Erbium Inorganic materials 0.000 description 1
- 229910002370 SrTiO3 Inorganic materials 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 238000005304 joining Methods 0.000 description 1
- 238000001459 lithography Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 229910000510 noble metal Inorganic materials 0.000 description 1
- 238000000059 patterning Methods 0.000 description 1
- 238000000206 photolithography Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000006479 redox reaction Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 238000007740 vapor deposition Methods 0.000 description 1
Abstract
Description
【発明の詳細な説明】
（産業上の利用分野）
本発明は超伝導トンネル接合、さらに詳細には酸化物超
伝導体素子に用いるトンネル接合に関するものである。DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to superconducting tunnel junctions, and more particularly to tunnel junctions used in oxide superconductor devices.
（従来の技術）
超伝導トンネル接合は量子効果が表れたもので、量子現
象を電子デバイスに応用する上で有力な候補になってい
る。このため高い温度でも動作するトンネル接合が作製
できると、応用が広がると期待されている。このトンネ
ル素子を実現するには、極めて薄い障壁層を超伝導体間
に形成する必要があり、多くの技術課題を解決しなけれ
ばならない。(Prior Art) Superconducting tunnel junctions exhibit quantum effects and are a promising candidate for applying quantum phenomena to electronic devices. Therefore, if tunnel junctions that can operate at high temperatures can be created, it is expected that their applications will expand. To realize this tunnel element, it is necessary to form an extremely thin barrier layer between superconductors, and many technical issues must be solved.
特に高い温度でも超伝導性が得られる酸化物超伝導体で
は、その特異な性質により金属とは異なる作製法の開発
が必要である。従来、酸化物超伝導体を用いたトンネル
接合の作製には、主に３つの方法が試みられている。１
つは、下部電極として酸化物超伝導体を、上部電極とし
て金属系超伝導体を選び接合を形成するもので、この場
合には金属との界面で酸化還元反応が起き、界面に高抵
抗層が形成され再現性よ＜ｈンネル特性を得ることは難
しい。In particular, oxide superconductors, which exhibit superconductivity even at high temperatures, require the development of a manufacturing method different from that of metals due to their unique properties. Conventionally, three main methods have been attempted to fabricate tunnel junctions using oxide superconductors. 1
One is to select an oxide superconductor as the lower electrode and a metallic superconductor as the upper electrode to form a junction. In this case, a redox reaction occurs at the interface with the metal, and a high-resistance layer is formed at the interface. is formed, making it difficult to obtain reproducible channel characteristics.
そこで、酸化しにくいＡｕあるいはＡｇなとの貴金属を
対抗電極として用い、接合を作製することも試みられて
いる。しかし７これらはＳＩＮ型とよばれ高性能の接合
素子への適用には程遠いものである。Therefore, attempts have been made to create a bond using a noble metal such as Au or Ag, which is difficult to oxidize, as a counter electrode. However, these are called SIN type devices and are far from being applicable to high-performance junction elements.
次Ｋ、画電極とも酸化物超伝導体で接合を作製するもの
で、この場合には、現在酸化物超伝導体薄膜の作製温度
が６００℃と高く上部電極の薄膜堆積時に下部電極表面
あるいはトンネル層が劣化すると、コヒーレンス長が短
く電極間の結合が弱いことから、問題となる。そこで、
トンネル層用の安定な材料の開発が進められているが、
まだ見い出されていない。また、トンネル層として金属
を用いる平面型の接合が作製されているがＳＮＳ型でや
はり充分の特性を持つとはいえない。In this case, the current production temperature of the oxide superconductor thin film is as high as 600°C, and during the deposition of the upper electrode thin film, the lower electrode surface or tunnel Deterioration of the layer is problematic because of the short coherence length and weak coupling between the electrodes. Therefore,
Progress is being made in developing stable materials for tunnel layers.
It has not been discovered yet. Further, planar junctions using metal as the tunnel layer have been manufactured, but they are SNS type and cannot be said to have sufficient characteristics.
最後は、多結晶体の結晶粒界に形成されるジョセフソン
接合（文献１：特願平２−３８０４２号）を用いるもの
である。既に高Ｔｅとなる材料を含む酸化物超伝導体多
結晶薄膜で、この粒界ジョセフソン接合を用いてＳＱＬ
、ｌＩＤあるいは光検出素子の作製が試みられている。The last method uses Josephson junctions (Reference 1: Japanese Patent Application No. 2-38042) formed at grain boundaries of a polycrystalline body. In an oxide superconductor polycrystalline thin film containing a material that already has high Te, this grain boundary Josephson junction can be used to perform SQL
Attempts have been made to fabricate , ID, or photodetector elements.
しかしこの接合を５ＱＵＩＩ）等に応用する場合、イ◇
相差が各接合に分散されるため接合数を増や１のは意味
がなく、逆に不利になる。このため多結晶薄膜を使用Ｊ
る場合にはパターン幅を狭くし狭い部分の粒界接合のみ
を使うことが試みられているが、電極部分に残る接合の
ため高感度特性を実現することは難［７い。However, when applying this joining to 5QUII) etc.,
Since the phase difference is dispersed in each junction, it is meaningless to increase the number of junctions by one, and on the contrary, it becomes disadvantageous. For this reason, a polycrystalline thin film is used.
In this case, attempts have been made to narrow the pattern width and use only the grain boundary bond in the narrow part, but it is difficult to achieve high sensitivity characteristics because the bond remains in the electrode area [7].
（発明が解決しようとする課題）
本発明は、市販の簡便な冷凍器で充分到達しうるＩＯＫ
の温度でも、電流−電圧特性に履歴を持つトンネル型の
特性を持つ酸化物超伝導体からなる接合を実現すること
を目的とする。(Problem to be solved by the invention)
The purpose of this research is to realize a junction made of an oxide superconductor with tunnel-type characteristics that exhibits a history of current-voltage characteristics even at temperatures of .
く課題を解決するための手段）
このような目的を達成するために本発明による超伝導Ｉ
・ンネル接合は、酸素八面体の中心に位置する金属が銅
である酸化物超伝導体をＦ部電極とし、酸素八面体の中
心に位置する金属がビスマスである酸化物超伝導体１１
３ａ１−ｙＭｙＢｉ ０３ （Ｍ：Ｋ、Ｒｂ）（Ｏ，２
＜ｙ＜Ｏ，６）の薄膜を［一部電極とする構造を持つこ
とを特徴とする。Means for Solving the Problems) In order to achieve such objects, the superconducting I according to the present invention
- In the tunnel junction, the F part electrode is an oxide superconductor in which the metal located in the center of the oxygen octahedron is copper, and the oxide superconductor 11 in which the metal located in the center of the oxygen octahedron is bismuth.
3a1-yMyBi 03 (M:K,Rb)(O,2
It is characterized by having a structure in which a thin film of <y<O, 6) is partially used as an electrode.
酸化物の超伝導体でコヒーレンズ長が長くしかも低基板
温度でも作製できるビスマス系酸化物超伝導体Ｂ ａｌ
−ｙＭｙＢ ｉ ０３ （Ｍ ： Ｋ、 Ｒｂ ）に注
目し、それを上部電極に用いている。上記ｙはＯ，２＜
ｙ＜０．６であるが、これは下記の実施例より明らかな
ようＫ、この範囲を逸脱すると超伝導を示さないからで
ある。Bismuth-based oxide superconductor B al has a long coherence lens length and can be produced at low substrate temperatures.
-yMyB i 03 (M: K, Rb) is focused on and used for the upper electrode. The above y is O, 2<
y<0.6, and this is because, as is clear from the examples below, superconductivity does not occur when K is outside this range.
一方基本結晶構造が上部電極と同じペロブスカイト型で
しかも低キヤリア濃度である銅系酸化物超伝導体、たと
えばＢａ２ＬｎＣｕ３Ｏ７−δ系（Ｌｈ ：Ｙ、Ｌａ、
Ｅｒ、Ｅｕ、Ｇｄ、Ｄｙ。On the other hand, copper-based oxide superconductors whose basic crystal structure is the same perovskite type as the upper electrode and have a low carrier concentration, such as Ba2LnCu3O7-δ system (Lh: Y, La,
Er, Eu, Gd, Dy.
Ｈｏ）、（Ｌ ａ １−ｘ Ｑ ｘ ） ２ Ｃｕ Ｏ
４系（Ｑ：Ｂａ、Ｓｒ）（０，０５＜Ｘ＜Ｏ，１５）あ
るいはＲｉ−Ｓｒ−Ｃａ、−Ｃ１１−０系などを、高い
作製温度が要求されることから１部電極として選択し、
接合を形成したものである。Ho), (L a 1-x Q x ) 2 Cu O
4 system (Q: Ba, Sr) (0,05 < ,
A joint is formed.
第１図は本発明を説明する構成図である。FIG. 1 is a configuration diagram illustrating the present invention.
１は基板で、酸化物超伝導体の単結晶薄膜を実現するた
め適当な基板（たとえばＭｇＯあるいはＳｒＴｉＯ３）
を選択する必要がある。２は接合の下部電極で銅系の酸
化物超伝導体薄膜よりなり、３は接合の上部電極でビス
マス系の酸化物超伝導体薄膜よりなるもので、両者とも
基板１上で昨結晶となる条件で作製される。４は接合界
面のＩ・ンネル層である。このような構成は、酸化物超
伝導体薄膜２（たとえば、Ｂａ２ＬｎＣｕ３Ｏ７−δ系
（Ｌｎ ：Ｙ、Ｌａ、Ｅｒ、Ｅｕ、Ｇｄ、 Ｄｙ。1 is a substrate, which is a suitable substrate (for example, MgO or SrTiO3) to realize a single crystal thin film of an oxide superconductor.
need to be selected. 2 is the lower electrode of the junction, which is made of a copper-based oxide superconductor thin film, and 3 is the upper junction electrode, which is made of a bismuth-based oxide superconductor thin film, both of which are crystallized on the substrate 1. Produced under certain conditions. 4 is an I-channel layer at the junction interface. Such a configuration is suitable for the oxide superconductor thin film 2 (for example, Ba2LnCu3O7-δ system (Ln: Y, La, Er, Eu, Gd, Dy).
Ｈｏ）の場合）を６００℃程度の高温度の基板上に堆積
しパターンを形成した後、酸化物超伝導体３を３Ｏ０℃
程度の低温度の基板上に堆積しパターン化することで形
成される。ところで、酸化物超伝導体２は、電極３を形
成する３Ｏ０〜４００℃の温度に対しては安定であるた
め、この工程でｒ部電極の超伝導性は劣化せず超伝導接
合を作製することができる０雨音の基本結晶構造はべ０
ブスカイト＄１を造と同じであるが、格子定数の不整合
性が大きいため、トンネル層４の界面で多くの欠陥が生
成されることになるにれらの酸化物超伝導体は低キヤリ
ア濃度により、この接合界面の欠陥は電気伝導に対し障
壁層を形成することになる。After depositing the oxide superconductor 3 on a substrate at a high temperature of about 600°C to form a pattern, the oxide superconductor 3 is heated to 300°C.
It is formed by depositing it on a substrate at a relatively low temperature and patterning it. By the way, since the oxide superconductor 2 is stable at the temperature of 3O0 to 400°C at which the electrode 3 is formed, the superconductivity of the r-section electrode does not deteriorate in this step and a superconducting junction is fabricated. The basic crystal structure of 0 rain sounds is 0
These oxide superconductors have a low carrier concentration, which is the same as that of buskite $1, but many defects are generated at the interface of the tunnel layer 4 due to the large mismatch of lattice constants. Therefore, defects at this bonding interface form a barrier layer against electrical conduction.
さらにキャリアの種類も銅系酸化物超伝導体は正孔であ
るのに対し、ビスマス系酸化物超伝導体では電子系と異
なるために空乏層の障壁が形成される。ただし半導体に
比べるとキャリア濃度が高いため、これらの障壁は超伝
導トンネル層として働くに適当なポテンシャル高さおよ
び幅となる。Furthermore, the type of carrier in the copper-based oxide superconductor is a hole, whereas in the bismuth-based oxide superconductor, the type of carrier is different from that in the electron system, so a barrier of a depletion layer is formed. However, since the carrier concentration is higher than in semiconductors, these barriers have an appropriate potential height and width to act as a superconducting tunnel layer.
（作用）
本発明によれば、簡便な作製法で超伝導回路中における
単一トンネル接合が形成できるため、景子干渉効果を用
いる５ＱＵＩＤなどのジョセフソン接合に適用すること
が可能である。また一方多数の接合からなる集積化も可
能である。(Function) According to the present invention, since a single tunnel junction in a superconducting circuit can be formed by a simple manufacturing method, it is possible to apply the present invention to a Josephson junction such as a 5QUID using the Keiko interference effect. On the other hand, integration consisting of a large number of junctions is also possible.
（実施例） 以上に実施例によ−って本発明の詳細な説明する。(Example) The present invention will be described in detail using Examples above.
なお、下部電極材１１として実施例１ではＢａ２ＹＣ＋
１３Ｏ７−δを、実施例２では（Ｌ、、 ａ ｉ”’−
Ｘｓ ｒｘ） ２Ｃ１，、Ｉ ０４ （ｘ−０、０”７
５ ）を述べるが、これらのかわりＫ、
１３ａ２Ｙｃｕ３Ｏ７−δでＹのかわりＧ、：、Ｉ、ａ
、Ｅｒ、Ｅｕ、Ｇｄ、Ｄｙ、Ｈｏの元素を用いても、ま
たは（Ｌａ、１．−ｘＳ ｒｘ） ２（’：ｕ０４ （
ｘＯ，０７５）系でＳｒのかわりにＢａを用い°ζも、
あるいはＲ１−Ｓｒ−Ｃａ−Ｃｕ−Ｏ系を用いても、以
下の実施例は成り立つ、従って、ここでは代表例を述べ
るもので、これによって請求範囲が限定されるものでは
ない。In addition, in Example 1, Ba2YC+ was used as the lower electrode material 11.
13O7-δ, in Example 2 (L,, a i”'-
Xs rx) 2C1,, I 04 (x-0, 0”7
5), but instead of these, K, 13a2Ycu3O7-δ, and instead of Y, G:, I, a
, Er, Eu, Gd, Dy, Ho or (La, 1.-xS rx) 2(':u04 (
By using Ba instead of Sr in the xO,075) system,
Alternatively, even if the R1-Sr-Ca-Cu-O system is used, the following examples are valid. Therefore, representative examples are described here, and the scope of the claims is not limited thereby.
（実施例１）
基板１と１７でＭｇＯ単結晶の０面を用い、基板１上に
酸化物超伝導体Ｂ ａ ２ＹＣｕ ３Ｏ７−δを、ＲＦ
スパッタ法により約１００ｎｒｎの膜厚で堆積する。堆
積後、リソグラフ技術を使用し電極パターン２を形成す
る。電極２の形状は幅２０μｍとし、た。その後、その
上に酸素イオンビーム照射共蒸着装置（文献２：特願昭
６：３−４２２１１号）あるいはスパッタ装置により（
Ｂａｏ、７ＫＯ，３）ＢｉＯ３薄膜の作製を行う、単結
晶薄膜が成長できるようＫ、基板温度は３Ｏ０〜４００
℃としな。(Example 1) Substrates 1 and 17 are MgO single crystal 0 planes, oxide superconductor B a 2YCu 3O7-δ is placed on substrate 1, and RF
The film is deposited to a thickness of about 100 nrn by sputtering. After the deposition, an electrode pattern 2 is formed using lithographic techniques. The shape of the electrode 2 was 20 μm in width. After that, an oxygen ion beam irradiation co-evaporation device (Reference 2: Japanese Patent Application No. 6:3-42211) or a sputtering device is used to deposit (
Bao, 7KO, 3) Preparation of BiO3 thin film, substrate temperature is 3O0~400K to grow single crystal thin film.
℃ and so.
その後、接合部を形成するようＫ、フォトリソグラフ技
術を使用しレジストパターンを作製し、イオンミリング
エツチング技術を用いて３の上部電極のパターン化する
。上下電極の重ね合わせの距離は２０μｍであり、接合
面積は２０Ｘ２０μｍ２となる。イオンミリングの際、
上部電極のエツチング速度が、下部電極に比べ５倍程度
と著しく高く、接合作製を容易にすることができた。Thereafter, a resist pattern is prepared using photolithography technology to form a bonding portion, and an upper electrode 3 is patterned using ion milling etching technology. The overlapping distance of the upper and lower electrodes is 20 μm, and the bonding area is 20×20 μm 2 . During ion milling,
The etching rate of the upper electrode was significantly higher, about 5 times that of the lower electrode, making it possible to easily fabricate the bond.
この上下電極パターン上に取り出し電極として金蒸着膜
を堆積することによりトンネル接合素子が作製できる。A tunnel junction element can be manufactured by depositing a gold vapor deposition film as an extraction electrode on this upper and lower electrode pattern.
この素子について、抵抗の温度依存性を測定した結果を
第２図に示す。FIG. 2 shows the results of measuring the temperature dependence of resistance for this element.
８０Ｋにおける抵抗の大きな変化はＦ部電極のＢａ２Ｙ
Ｃｕ３Ｏ７−δの超伝導転移によるもので、１０Ｋにお
ける抵抗の急激な低下は上部電極の（Ｂａｏ、７に０．
３）ＢｉＯ３の超伝導転移によるものである。２０に以
下で完全に抵抗は消えておらず、低温はどわずかに増加
している。４．２Ｋにおける電流−電圧（Ｉ−、Ｖ）特
性を４端子法で測定した結果を第３図に示す。異なる超
伝導エネルギーギャップ幅をもつ超伝導体から構成され
るトンネル型接合が形成されていることがわかる。The large change in resistance at 80K is due to Ba2Y of the F section electrode.
This is due to the superconducting transition of Cu3O7-δ, and the rapid decrease in resistance at 10K is due to the upper electrode (Bao, 7 to 0.
3) This is due to the superconducting transition of BiO3. Below 20°C, the resistance does not completely disappear, and the low temperature increases slightly. Figure 3 shows the results of measuring the current-voltage (I-, V) characteristics at 4.2K using the four-terminal method. It can be seen that a tunnel-type junction is formed consisting of superconductors with different superconducting energy gap widths.
この場合には超伝導トンネル電流を観測することはでき
なかった。これは銅系酸化物超伝導体のコヒーレンス長
さがＣ軸方向で短いことによる。In this case, no superconducting tunneling current could be observed. This is because the coherence length of the copper-based oxide superconductor is short in the C-axis direction.
なお（Ｂａａ、７ＫＯ７３）ＢｉＯ３の超伝導エネルギ
ーギャップ２Δは６ｍｅＶであることから、Ｂａ２ＹＣ
ｕ３Ｏ７−δのＣ軸方向の超伝導エネルギーギャップ２
ΔはＩ−Ｖ特性の電圧ギャップより約２ ｍ ｅ Ｖで
あることがわかる。(Baa, 7KO73) Since the superconducting energy gap 2Δ of BiO3 is 6 meV, Ba2YC
Superconducting energy gap 2 in the C-axis direction of u3O7-δ
It can be seen that Δ is about 2 m e V from the voltage gap of the IV characteristic.
なお（Ｂａｔ−ｙＫｙ）ＢｉＯ３が超伝導性を示す０．
２＜ｙ＜Ｏ，６の範囲で、超伝導トンネル接合の特性を
観測することができた。Note that (Bat-yKy)BiO3 exhibits superconductivity.
The characteristics of superconducting tunnel junctions could be observed in the range of 2<y<O, 6.
なお、（Ｂａｘ−ｙＫｙ）ＢｉＯ３において、Ｋのかわ
りにＲｂを用いても同様の結果が得られた。Note that similar results were obtained when Rb was used instead of K in (Bax-yKy)BiO3.
また、ｙの範囲が上記以外では起伏導性を示さない
（実施例２）
基板１としてＳｒＴｉ０３単結晶の（１１，０）面を用
い、２の酸化物超伝導体薄膜材料として（Ｌａ１−ｘ５
ｙ−ｘ） ２ｃｕｏ４（Ｘ、＝０．０７５）を選択し、
ＲＦスパッタ法により基板１上に約１、ＯＯｎｍの膜厚
で堆積する。なおＸの範囲は、（Ｌ ａ １−ｘ Ｓ
ｒ ｘ ） ２ Ｃｕ ０４が超伝導を示す領域で決ま
り、０．０５＜Ｘ＜０．１５となる。２の電極を形成す
るための堆積後、リソグラフ技術を使用しパターンを形
成しておく、電極の形状は幅２０μｍとした。その後、
実施例１と同様の方法によりトンネル接合素子作製を行
う、この素子について、４，２Ｋにおける電流−電圧特
性を４端子法で測定した結果を第４図に示す、異なる超
伝導エネルギー・ギャップ幅をもつ超伝導体から構成さ
れるトンネル型ジョセフソン接合が形成さしていること
がわかる。また、Ｉ−Ｖ特性の電圧ギヤ’ｙブより（Ｂ
ａｏ、７ＫＯ，３） Ｂ ｊ、 ０３の超伝導エネルギ
ーギャップΔが３ ｍ ｅ Ｖと、（Ｌａｘ−ｘＳｒｘ
）２ＣｕＯ４ （１０３）方向の超伝導エネルギーギャ
ップ２Δが６ｎ“ｉｅＶとなることがわかる。In addition, undulation conductivity is not exhibited when the range of y is other than the above (Example 2) The (11,0) plane of SrTi03 single crystal is used as the substrate 1, and (La1-x5
y−x) 2cuo4(X,=0.075),
A film thickness of about 1.0 nm is deposited on the substrate 1 by RF sputtering. Note that the range of X is (L a 1-x S
r x ) 2 It is determined by the region where Cu 04 exhibits superconductivity, and 0.05<X<0.15. After the deposition for forming the second electrode, a pattern was formed using lithography technology, and the shape of the electrode was 20 μm in width. after that,
A tunnel junction device was fabricated using the same method as in Example 1. The current-voltage characteristics of this device were measured using the four-terminal method at 4 and 2 K. The results are shown in Figure 4. It can be seen that a tunnel-type Josephson junction composed of superconductors is formed. Also, from the voltage gear 'yb of the I-V characteristic (B
ao, 7KO, 3) B j, the superconducting energy gap Δ of 03 is 3 m e V, and (Lax-xSrx
)2CuO4 It can be seen that the superconducting energy gap 2Δ in the (103) direction is 6n"ieV.
第５図に超伝導電流の温度依存性を示す、これより、２
２にの温度まで超伝導電流が流れトンネル接合になって
いることがわかる。Figure 5 shows the temperature dependence of superconducting current. From this, 2
It can be seen that superconducting current flows up to a temperature of 2, forming a tunnel junction.
（発明の効果）
以上説明したようＫ、本発明により超伝導転移温度の高
い酸化物超伝導体のトンネル接合を作製することができ
る。この接合は、２０に以下の温度において超伝導トン
ネル特性を示す。従って、小型冷凍器が既に実現してい
るＩＯＫの温度において動作することができ、操作性お
よび経済性において利点がある。また、４．２にの温度
で動作させる場合にも、超伝導のエネルギーギャップ幅
が大きく、準粒子数が減少するため、センサーとして用
いる場合、′！ａ′Ｂ′が低下し高感度化が図れる利点
がある。また、上部電極として使用しまた酸化物超伝導
体は等方的でしかも超伝導のコヒーレント長が長いとい
う特性をもつため、高Ｔｃではあるが異方性が大きい銅
系酸化物超伝導体の取り出し電極のバッファとしてもこ
の接合は有用になる。(Effects of the Invention) As explained above, according to the present invention, a tunnel junction of an oxide superconductor having a high superconducting transition temperature can be fabricated. This junction exhibits superconducting tunneling properties at temperatures below 20°C. Therefore, it is possible to operate at the IOK temperature that has already been achieved in small refrigerators, which is advantageous in terms of operability and economy. Also, even when operating at a temperature of 4.2, the energy gap width of superconductivity is large and the number of quasiparticles is reduced, so when used as a sensor, '! This has the advantage that a'B' is lowered and higher sensitivity can be achieved. In addition, since oxide superconductors are used as upper electrodes and have the characteristics of being isotropic and having a long superconducting coherence length, copper-based oxide superconductors with high Tc but large anisotropy can be used. This junction is also useful as a buffer for the extraction electrode.
第１図は本発明を説明する構成図、
第２図はＢ ａ ２ＹＣｕ ３Ｏ７−ｓ（Ｂａｏ、７に
０．３）Ｂｉ０３接合素子の抵抗の温度依存性、
第３図は４端子法で測定した
Ｂ ａ ２ＹＣｕ ３Ｏ７−δ
（Ｂａｏ、７ＫＯ，３）Ｂ ｉｏ：ｉ接合素子の４．２
Ｋにおける電流−電圧特性、
第４図は４端子法で測定した４、２Ｋにおける（Ｌａｘ
−ｘＳｒｘ） ２ｃｕｏ４−
（Ｂａｏ、７に０．３）Ｂｉ０３接合素子の電流−電圧
特性、
第５図は（Ｌａｔ−ｘＳｒｘ、） ２ｃｕ０４（Ｂａａ
、７に０．３）Ｂ ｉ０３接合素子の超伝導１＝。
ンネル電流の温度依存性を示す図である。
１・・・基板、２・・・銅系酸化物超伝導体単結晶薄膜
よりなる下部電極、３・・・ビスマス系の酸化物超伝導
体単結晶薄膜よりなる上部電極、４・・・接合界面のト
ンネル層。Figure 1 is a configuration diagram explaining the present invention, Figure 2 is the temperature dependence of the resistance of a B a 2YCu 3O7-s (Bao, 7 to 0.3) Bi03 junction element, and Figure 3 is measured using the four-terminal method. 4.2 of B a 2YCu 3O7-δ (Bao, 7KO, 3)B io:i junction element
Figure 4 shows the current-voltage characteristics at 4 and 2 K (Lax
-xSrx) 2cuo4- (Bao, 7 to 0.3) Current-voltage characteristics of Bi03 junction element, Figure 5 shows (Lat-xSrx,) 2cu04(Baa
, 7 to 0.3) Superconductivity 1= of B i03 junction elements. FIG. 3 is a diagram showing the temperature dependence of channel current. DESCRIPTION OF SYMBOLS 1...Substrate, 2...Lower electrode made of a copper-based oxide superconductor single crystal thin film, 3...Upper electrode made of a bismuth-based oxide superconductor single crystal thin film, 4...Junction Tunnel layer at the interface.
Claims (2)
物超伝導体を下部電極とし、酸素八面体の中心に位置す
る金属がビスマスである酸化物超伝導体Ｂａ＿１−ｙＭ
ｙＢｉＯ＿３（Ｍ：Ｋ、Ｒｂ）（０．２＜ｙ＜０．６）
の薄膜を上部電極とする構造を持つことを特徴とする超
伝導トンネル接合。(1) Oxide superconductor Ba_1-yM in which the metal located at the center of the oxygen octahedron is copper is used as the lower electrode, and the metal located at the center of the oxygen octahedron is bismuth
yBiO_3 (M:K, Rb) (0.2<y<0.6)
A superconducting tunnel junction characterized by having a structure in which a thin film of is used as the upper electrode.
（Ｌｎ：Ｙ、Ｌａ、Ｅｒ、Ｅｕ、Ｇｄ、Ｄｙ、Ｈｏ）あ
るいは（Ｌａ＿１＿−＿ｘＱ＿ｘ）＿２ＣｕＯ＿４系（
Ｑ：Ｂａ、Ｓｒ）（０．０５＜Ｘ＜０．１５）あるいは
Ｂｉ−Ｓｒ−Ｃａ−Ｃｕ−Ｏ系であることを特徴とする
特許請求の範囲第１項記載の超伝導トンネル接合。(2) The lower electrode is Ba2LnCu_3O_7_-_δ system (Ln: Y, La, Er, Eu, Gd, Dy, Ho) or (La_1_-_xQ_x)_2CuO_4 system (
The superconducting tunnel junction according to claim 1, characterized in that Q: Ba, Sr) (0.05<X<0.15) or Bi-Sr-Ca-Cu-O system.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2164526A JPH0461177A (en) | 1990-06-22 | 1990-06-22 | Superconducting tunnel junction |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2164526A JPH0461177A (en) | 1990-06-22 | 1990-06-22 | Superconducting tunnel junction |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0461177A true JPH0461177A (en) | 1992-02-27 |
Family
ID=15794845
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2164526A Pending JPH0461177A (en) | 1990-06-22 | 1990-06-22 | Superconducting tunnel junction |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0461177A (en) |
-
1990
- 1990-06-22 JP JP2164526A patent/JPH0461177A/en active Pending
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