JPH0590654A - Superconducting device - Google Patents
Superconducting deviceInfo
- Publication number
- JPH0590654A JPH0590654A JP3247722A JP24772291A JPH0590654A JP H0590654 A JPH0590654 A JP H0590654A JP 3247722 A JP3247722 A JP 3247722A JP 24772291 A JP24772291 A JP 24772291A JP H0590654 A JPH0590654 A JP H0590654A
- Authority
- JP
- Japan
- Prior art keywords
- film
- oxide
- josephson
- superconducting
- oxide superconductor
- 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.)
- Granted
Links
Landscapes
- Superconductor Devices And Manufacturing Methods Thereof (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、酸化物超電導体を用い
た超電導素子に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting element using an oxide superconductor.
【０００２】[0002]
【従来の技術】現在まで、超高密度電子素子や超高速電
子素子の開発は、シリコンおよび化合物半導体を中心と
して進められてきた。ところで、従来の半導体素子の高
密度化や高速化は、高度の微細加工技術、均質で完全性
の高い結晶作製技術およびシミュレーションを利用した
素子設計技術により成し遂げられてきた。2. Description of the Related Art Up to now, development of ultra-high-density electronic devices and ultra-high-speed electronic devices has been promoted mainly in silicon and compound semiconductors. By the way, the densification and speedup of conventional semiconductor elements have been achieved by advanced fine processing technology, homogeneous and highly complete crystal production technology, and element design technology using simulation.
【０００３】半導体素子の高密度化や高速化等をさらに
図る上で、今後ますます重要になる問題として、駆動・
動作発熱が挙げられる。つまり、半導体素子自体の結晶
の完全性や微細加工技術とは別に、半導体素子の駆動・
動作発熱が高密度化や高速化に限界を与える大きな要因
になると考えられるからである。In order to further increase the density and speed of semiconductor devices, driving and
Operating heat is included. In other words, in addition to the crystal perfection of the semiconductor element itself and the fine processing technology,
This is because operating heat is considered to be a major factor that limits the increase in density and speed.
【０００４】ここで、ジョセフソン接合素子に代表され
る超電導素子は、駆動・動作発熱の点で、半導体素子等
の電子素子に比べて優れるという利点を有している。し
かし、超電導素子はこれまでのところ、本格的な実用化
の目途は十分立っているとはいえない。その理由として
は、従来のジョセフソン素子が液体ヘリウム温度まで冷
却しないと動作しないこと、動作電圧が約 1mVと低いた
めに1V以上で動作する半導体素子との整合性が悪いこと
等が挙げられる。Here, the superconducting element represented by the Josephson junction element has an advantage that it is superior to electronic elements such as semiconductor elements in terms of driving and operating heat generation. However, it cannot be said that the prospect of practical application of the superconducting device has been sufficiently established so far. The reason for this is that the conventional Josephson device does not operate unless it is cooled to the liquid helium temperature, and the operating voltage is as low as about 1 mV, so the compatibility with semiconductor devices operating above 1 V is poor.
【０００５】これに対して、近年、酸化物超電導体に代
表される高温超電導体の発見に伴って、液体窒素温度で
動作するジョセフソン素子の研究開発が活発に行われて
いる。しかしながら、液体窒素温度でジョセフソン特性
が確認された素子は、酸化物超電導体薄膜内に存在する
粒界を利用した粒界ジョセフソン素子に限られている。
粒界ジョセフソン素子は、ＳＱＵＩＤ（超電導磁束量子
干渉計）やマイクロ波ミキサ等の一部の用途としての利
用は期待されているものの、制御性の悪い粒界を利用す
るため、本格的な超電導エレクトロニクスへの応用は危
ぶまれている。また、粒界ジョセフソン素子は、素子の
出力となる実用上重要な臨界電流Ｉc と常伝導抵抗Ｒn
との積（Ｉc ・Ｒn 積）が数10μV 程度と小さいという
難点も有していた。On the other hand, in recent years, with the discovery of high-temperature superconductors represented by oxide superconductors, research and development of Josephson devices operating at liquid nitrogen temperature have been actively conducted. However, the device whose Josephson characteristic is confirmed at the liquid nitrogen temperature is limited to the grain boundary Josephson device utilizing the grain boundary existing in the oxide superconductor thin film.
The grain boundary Josephson element is expected to be used for some applications such as SQUID (superconducting flux quantum interferometer) and microwave mixer, but since it uses grain boundaries with poor controllability Application to electronics is at stake. Further, the grain boundary Josephson element has a critical current I c which is an output of the element and which is practically important, and a normal resistance R n.
It also had a drawback that the product (I c · R n product) with was as small as several tens of μV.
【０００６】このようなことから、粒界ジョセフソン素
子に代るジョセフソン素子として、積層型のジョセフソ
ン素子の開発が期待されており、その研究も進められて
いる。例えば、ＳＮＳ接合型のジョセフソン素子におい
ては、PrBa2 Cu3 O7-δ、 (Pr1-x Yx ）Ba2 Cu3 O
7-δ、La1-x Bax Cu3 O7-δ、Bi2 Sr1 Cu1 O5-δ等の
銅の 2価イオンを含む電気伝導性酸化物を、常伝導体層
として用いることが検討されている。しかしながら、こ
のような電気伝導性酸化物を常伝導体層として用いると
共に、超電導体層として酸化物超電導体のみを用いたＳ
ＮＳ接合型のジョセフソン素子では、粒界ジョセフソン
素子と同様に、Ｉc ・Ｒn 積が数10μV 程度と極めて小
さく、実用化の妨げとなっていた。また、これまでに報
告された素子のなかには、 1mVを超えるＩc ・Ｒn 積を
示すものもあるが、それらは電流−電圧特性およびその
磁場依存性が明確なジョセフソン特性をしていない。From the above, it is expected that a laminated type Josephson element will be developed as a Josephson element to replace the grain boundary Josephson element, and research on it is underway. For example, in an SNS junction type Josephson element, PrBa 2 Cu 3 O 7-δ , (Pr 1-x Y x ) Ba 2 Cu 3 O
Use an electrically conductive oxide containing divalent copper ions such as 7-δ , La 1-x Ba x Cu 3 O 7-δ , Bi 2 Sr 1 Cu 1 O 5-δ as the normal conductor layer. Is being considered. However, such an electrically conductive oxide is used as the normal conductor layer, and the oxide superconductor alone is used as the superconductor layer.
Similar to the grain boundary Josephson element, the NS junction type Josephson element has a very small I c · R n product of about several tens of μV, which hinders its practical use. Further, some of the devices reported so far show an I c · R n product exceeding 1 mV, but they do not have the Josephson property in which the current-voltage characteristic and the magnetic field dependence thereof are clear.
【０００７】一方、対極に従来の金属超電導体を用い
た、例えば Y-Ba-Cu-O/Au(Ag)/Nb(Pb)等の構成を有する
ジョセフソン素子によれば、明確なジョセフソン特性が
確認されているものの、このような素子は液体ヘリウム
温度でしか動作せず、酸化物超電導体による利点が活か
されないという問題を有していた。このように、液体窒
素温度で動作が可能で、実用上十分なＩc ・Ｒn 積を有
する、酸化物超電導体のみを用いたジョセフソン素子
は、未だ得られていないのが現状である。On the other hand, according to the Josephson device having a conventional metal superconductor for the counter electrode, such as Y-Ba-Cu-O / Au (Ag) / Nb (Pb), a clear Josephson element is used. Although the characteristics have been confirmed, such an element has a problem that it operates only at the liquid helium temperature, and the advantage of the oxide superconductor cannot be utilized. As described above, the Josephson device using only the oxide superconductor, which can operate at the liquid nitrogen temperature and has a practically sufficient I c · R n product, has not yet been obtained.
【０００８】[0008]
【発明が解決しようとする課題】上述したように、超電
導素子は発熱が少ない点で、従来の半導体素子の高密度
化や高速化の限界を超え得るものとして注目されている
ものの、従来の金属系超電導体を用いたジョセフソン素
子は、液体ヘリウムあるいはその近傍という極低温まで
冷却しなければ動作しないことから、実用化が妨げられ
てきた。As described above, since the superconducting element generates less heat, it has attracted attention as a material that can exceed the limit of high density and high speed of the conventional semiconductor element, but the conventional metal is not used. Since the Josephson device using the superconductor of the system does not operate unless it is cooled to the cryogenic temperature of liquid helium or its vicinity, its practical application has been hindered.
【０００９】一方、酸化物超電導体を用いたジョセフソ
ン素子は、液体窒素温度での動作は可能であるものの、
例えば粒界ジョセフソン素子は、制御性が悪くかつＩc
・Ｒn 積が小さく、また積層型ジョセフソン素子もＩc
・Ｒn 積が小さいという問題を有していた。On the other hand, the Josephson element using the oxide superconductor can operate at liquid nitrogen temperature,
For example, the grain boundary Josephson element has poor controllability and I c
-The R n product is small, and the laminated Josephson device has an I c
There was a problem that the R n product was small.
【００１０】本発明は、このような課題に対処するため
になされたもので、液体窒素温度での動作が可能である
と共に、実用上十分なＩc ・Ｒn積を示し、かつ制御性
に優れた、酸化物超電導体を用いた超電導素子を提供す
ることを目的とするものである。The present invention has been made in order to solve such a problem, and it is possible to operate at the liquid nitrogen temperature, to exhibit a practically sufficient I c · R n product and to have controllability. An object is to provide an excellent superconducting element using an oxide superconductor.
【００１１】[0011]
【課題を解決するための手段】本発明の超電導素子、酸
化物超電導体／常伝導体／酸化物超電導体によって構成
したジョセフソン接合を有する超電導素子において、前
記常伝導体が有するスピン磁気モーメントは、 1/2未満
であることを特徴としている。In the superconducting element of the present invention, which has a Josephson junction composed of oxide superconductor / normal conductor / oxide superconductor, the spin magnetic moment of the normal conductor is , Less than 1/2.
【００１２】本発明の超電導素子においては、各種の酸
化物超電導体を使用することが可能であり、下記の各式
で実質的に組成が表されるもの等が例示される。In the superconducting element of the present invention, various oxide superconductors can be used, and examples thereof include those whose composition is substantially represented by the following formulas.
【００１３】La2-a AEa Cu O4 （式中、AEはBa、SrおよびCaから選ばれた少なくとも 1
種の元素を、 aは0.05≦a≦ 0.2を満足する数を示す） RE Ba2 Cu3 O 7-δ （式中、REは Yを含む希土類元素から選ばれた少なくと
も 1種の元素を示し、δは酸素欠損を表す。以下同じ） Bi2-b Pbb (Sr,Ca)3-c REc Cu2 O 8+x （式中、 xは酸素の微小な変動を表し、 bおよび cは 0
≦b ≦ 1、 0≦c ≦0.3を満足する数を示す。以下同
じ） Bi2-b Pbb (Sr,Ca)4-d REd Cu3 O 10+x （式中、 dは 0≦d ≦0.4 を満足する数を示す） Tl2 Ba2 Ca1 Cu2 O 8+x Tl1 Ba2 Ca1 Cu2 O 7+x Tl2 Ba2 Ca2 Cu3 O 10+x Tl1 Ba2 Ca2 Cu3 O 9+x また、本発明に用いられる常伝導体は、超電導素子動作
時の常伝導層としてのスピン磁気モーメントが 1/2未満
となるものである。すなわち、本発明においては、 s=1
/2の磁気スピンをもつ銅イオンを含まない、低温で導電
性を示す遷移金属酸化物や、圧力または応力の印加によ
り s=1/2の磁気スピンの量を減少せしめたペロブスカイ
ト型導電性酸化物等の、弱磁性あるいは非磁性を示す常
伝導体が用いられる。La 2-a AE a Cu O 4 (wherein AE is at least 1 selected from Ba, Sr and Ca)
RE a Ba 2 Cu 3 O 7-δ (where RE is at least one element selected from rare earth elements including Y). , Δ represents oxygen deficiency. The same applies hereinafter) Bi 2-b Pb b (Sr, Ca) 3-c RE c Cu 2 O 8 + x (where x represents a minute fluctuation of oxygen, and b and c is 0
Indicates a number that satisfies ≤b ≤1 and 0 ≤c ≤0.3. The same shall apply hereinafter) Bi 2-b Pb b (Sr, Ca) 4-d RE d Cu 3 O 10 + x (where d is a number satisfying 0 ≦ d ≦ 0.4) Tl 2 Ba 2 Ca 1 Cu 2 O 8 + x Tl 1 Ba 2 Ca 1 Cu 2 O 7 + x Tl 2 Ba 2 Ca 2 Cu 3 O 10 + x Tl 1 Ba 2 Ca 2 Cu 3 O 9 + x The normal conductivity used in the present invention The body has a spin magnetic moment of less than 1/2 as a normal conducting layer during operation of a superconducting device. That is, in the present invention, s = 1
A transition metal oxide that does not contain copper ions with a magnetic spin of 1/2 and shows conductivity at low temperature, or a perovskite-type conductive oxide that reduces the amount of magnetic spin of s = 1/2 by applying pressure or stress. A normal conductor that exhibits weak magnetism or nonmagnetism, such as an object, is used.
【００１４】本発明の超電導素子においては、上記した
条件を満足する常伝導体を用いれば本発明の効果が得ら
れるものの、優れたジョセフソン素子を得るためには、
さらに以下の条件を満足する導電性酸化物を常伝導体と
して用いることが好ましい。第１の条件は、酸素雰囲気
下での合成が可能であることである。La系、 Y系、Bi
系、Tl系等の多くの酸化物超電導体は p型の導体であ
り、酸化雰囲気下で合成される。これらの酸化物超電導
体と積層される酸化物は、やはり酸素雰囲気下で合成可
能な p型の導体であることが好ましい。 p型の酸化物超
電導体と n型の酸化物とを積層すると、界面での酸化還
元反応によって、酸化物超電導体は正孔を奪われ、界面
での超電導特性が著しく劣化してしまう。In the superconducting device of the present invention, if a normal conductor satisfying the above conditions is used, the effect of the present invention can be obtained, but in order to obtain an excellent Josephson device,
Furthermore, it is preferable to use a conductive oxide satisfying the following conditions as the normal conductor. The first condition is that the synthesis can be performed in an oxygen atmosphere. La series, Y series, Bi
Many oxide superconductors such as those based on Tl and Tl are p-type conductors and are synthesized in an oxidizing atmosphere. The oxide laminated with these oxide superconductors is preferably a p-type conductor which can be synthesized also in an oxygen atmosphere. When the p-type oxide superconductor and the n-type oxide are laminated, the oxide superconductor loses holes due to the redox reaction at the interface, and the superconducting property at the interface is significantly deteriorated.
【００１５】第２の条件は、常伝導体のキャリア濃度が
超電導体のそれを大きく超えないことである。近接効果
の理論によれば、キャリア濃度が小さい超電導体とキャ
リア濃度の大きい常伝導体とを接触させると、その界面
近傍で超電導ギャップが著しく縮小することが知られて
いる。酸化物超電導体のキャリア濃度は1022cm-3程度で
あることが知られており、常伝導体のキャリア濃度はそ
の濃度を大きく超えないようにすることが好ましい。The second condition is that the carrier concentration of the normal conductor does not greatly exceed that of the superconductor. According to the theory of proximity effect, it is known that when a superconductor having a low carrier concentration and a normal conductor having a high carrier concentration are brought into contact with each other, the superconducting gap is significantly reduced in the vicinity of the interface. It is known that the carrier concentration of the oxide superconductor is about 10 22 cm −3 , and it is preferable that the carrier concentration of the normal conductor does not greatly exceed the concentration.
【００１６】上述したような条件を満足する常伝導体、
すなわちスピン磁気モーメントが1/2未満で、酸化雰囲
気下で合成可能な導電性酸化物としては、例えばNi3+や
Co3+を含む導電性酸化物が挙げられる。このようなNi3+
やCo3+を含む導電性酸化物としては、ペロブスカイト構
造を有する、La1-x AEx NiO3 、La1-x AEx CoO3 （AE
はSr、CaおよびBaから選ばれた少なくとも 1種の元素
を、 xは 0≦ x≦ 0.3を満足する数を示す）や、層状α
-NaFeO2 型構造を有する、 A1-x CuO2 、 A1- x Ni
O2 、 A1-x CoO2 (AはLi、Naおよび Kから選ばれた少
なくとも 1種の元素を、 xは 0≦ x≦ 0.3を満足する数
を示す）等が例示される。A normal conductor satisfying the above-mentioned conditions,
That is, as the conductive oxide having a spin magnetic moment of less than 1/2 and synthesizable in an oxidizing atmosphere, for example, Ni 3+ or
A conductive oxide containing Co 3+ can be used. Ni 3+ like this
Conductive oxides containing Co 3+ include La 1-x AE x NiO 3 , La 1-x AE x CoO 3 (AE having a perovskite structure.
Is at least one element selected from Sr, Ca and Ba, and x is a number satisfying 0 ≦ x ≦ 0.3), or a layered α
-Having a NaFeO 2 type structure, A 1-x CuO 2 , A 1- x Ni
O 2 , A 1-x CoO 2 (A represents at least one element selected from Li, Na and K, and x represents a number satisfying 0 ≦ x ≦ 0.3) and the like are exemplified.
【００１７】また、これまでに常伝導体層として用いら
れてきたペロブスカイト型銅系酸化物、例えばPrBa2 Cu
3 O7-δ、 (Pr1-x Yx ）Ba2 Cu3 O7-δ、La1-x Bax
Cu3 O7-δ、Bi2 Sr1 Cu1 O5-δ等は、酸素雰囲気下で
合成可能であるが、通常の状態では銅の 2価イオンに起
因する s=1/2のスピンを有している。これらにおいて
は、適正な圧力あるいは応力を加え、銅−酸素間の波動
関数の重なりを増大させることにより、局在スピンを持
つ銅の 2価イオンを減少させることができ、常伝導体層
としてのスピン磁気モーメントを 1/2未満とすることが
できる。すなわち、ペロブスカイト型銅系酸化物は、適
正な圧力あるいは応力を加えた状態とすることによっ
て、本発明の常伝導体として用いることが可能となる。Further, perovskite type copper oxides which have been used as a normal conductor layer so far, for example PrBa 2 Cu.
3 O 7-δ , (Pr 1-x Y x ) Ba 2 Cu 3 O 7-δ , La 1-x Ba x
Cu 3 O 7-δ , Bi 2 Sr 1 Cu 1 O 5-δ, etc. can be synthesized in an oxygen atmosphere, but under normal conditions, spins of s = 1/2 due to divalent copper ions are generated. Have In these, by applying appropriate pressure or stress and increasing the overlap of the wave functions between copper and oxygen, it is possible to reduce the divalent ions of copper having localized spins, and The spin magnetic moment can be less than 1/2. That is, the perovskite-type copper-based oxide can be used as the normal conductor of the present invention by applying appropriate pressure or stress.
【００１８】[0018]
【作用】積層型ジョセフソン素子の常伝導体層として
は、これまで銅の 2価イオンを含む酸化物が用いられて
きた。銅の 2価イオンは s=1/2のスピン磁気モーメント
をもっており、スピン磁気モーメントが超電導特性を劣
化させることが知られている。従来の積層型ジョセフソ
ン素子のＩc ・Ｒn 積が小さかった理由としては、銅の
2価イオンを含む常伝導体層内で、超電導ギャップが著
しく減少してしまうためと考えられる。また、粒界ジョ
セフソン素子では、どのような物質が常伝導体として働
いているのか明確にはされていないが、界面での格子の
周期性の乱れ、組成ずれ等により、スピンをもった銅の
2価イオンが存在する可能性が強く、このためＩc ・Ｒ
n 積が小さくなってしまうと考えられる。[Function] An oxide containing divalent copper ions has been used for the normal conductor layer of the laminated Josephson device. The divalent copper ion has a spin magnetic moment of s = 1/2, and it is known that the spin magnetic moment deteriorates the superconducting property. The reason why the I c · R n product of the conventional stacked Josephson element is small is that copper
It is considered that the superconducting gap is significantly reduced in the normal conductor layer containing divalent ions. In the grain boundary Josephson element, it is not clear what kind of substance works as a normal conductor. of
It is highly possible that divalent ions are present, which is why I c · R
It is thought that the n product will become small.
【００１９】これらに対して、本発明の酸化物超電導体
を用いた超電導素子では、酸化物超電導体／常伝導体／
酸化物超電導体接合構造における常伝導体層を、スピン
磁気モーメントが 1/2未満の導電性酸化物によって構成
している。このように、弱磁性あるいは非磁性の常伝導
体層を用いることによって、常伝導体層内での超電導ギ
ャップの減少を抑制することが可能となる。よって、実
用上十分なＩc ・Ｒn 積を積層型構造で得ることが可能
となる。On the other hand, in the superconducting element using the oxide superconductor of the present invention, the oxide superconductor / normal conductor /
The normal conductor layer in the oxide superconductor junction structure is made of a conductive oxide having a spin magnetic moment of less than 1/2. As described above, by using the weak magnetic or nonmagnetic normal conductor layer, it is possible to suppress the reduction of the superconducting gap in the normal conductor layer. Therefore, it is possible to obtain a practically sufficient I c · R n product in the laminated structure.
【００２０】[0020]
【実施例】以下、本発明の実施例について説明する。EXAMPLES Examples of the present invention will be described below.
【００２１】実施例１ この実施例の超電導素子の製造工程を図１にしたがって
説明する。まず、 SrTiO3 基板１上に、下部酸化物超電
導体膜として YBa2 Cu3 O 7-δ膜２（膜厚 300nm）、 L
aNiO3 膜３（膜厚100nm)、および上部酸化物超電導体膜
として YBa2 Cu3 O 7-δ膜４（膜厚300nm)を、スパッタ
法により順に成膜し、 3層積層膜構造を作製した（図１
−ａ）。成膜時の基板温度は 680℃とし、またスパッタ
ガスとしては50%O2 /Ar の混合ガスを用いた。成膜後、
直ちに基板加熱を止めると共に、成膜室内に 1気圧純酸
素を導入し、常温まで冷却した。Example 1 The manufacturing process of the superconducting element of this example will be described with reference to FIG. First, on the SrTiO 3 substrate 1, as a lower oxide superconductor film, YBa 2 Cu 3 O 7-δ film 2 (thickness 300 nm), L
An aNiO 3 film 3 (thickness 100 nm) and an YBa 2 Cu 3 O 7-δ film 4 (thickness 300 nm) as an upper oxide superconductor film are sequentially formed by a sputtering method to form a three-layer laminated film structure. (Fig. 1
-A). The substrate temperature during film formation was 680 ° C., and a mixed gas of 50% O 2 / Ar was used as the sputtering gas. After film formation,
Immediately after stopping the heating of the substrate, 1 atmosphere of pure oxygen was introduced into the film formation chamber and cooled to room temperature.
【００２２】得られた Y-Ba-Cu-O系酸化物超電導体膜
２、４は、ａ軸が基板に垂直なａ軸配向膜であり、 LaN
iO3 は立方晶であった。また、 Y-Ba-Cu-O系酸化物超電
導体膜２、４の臨界温度は 91.5Kで、電気抵抗の転移幅
は0.5Kであった。The obtained Y-Ba-Cu-O-based oxide superconductor films 2 and 4 are a-axis oriented films in which the a-axis is perpendicular to the substrate, and LaN
iO 3 was cubic. The critical temperature of the Y-Ba-Cu-O-based oxide superconductor films 2 and 4 was 91.5K, and the transition width of electrical resistance was 0.5K.
【００２３】次に、上記 3層膜をリソグラフィプロセス
を用いて加工することによって、接合の面積が10μm ×
10μm のジョセフソン素子を作製した。まず、上部 Y-B
a-Cu-O系酸化物超電導体膜４上に厚さ 1.2μm のAu膜５
を形成した後、Au膜５、上部 Y-Ba-Cu-O系酸化物超電導
体膜４および LaNiO3 膜３をアルゴンイオンミリングに
よって、10μm 幅にエッチングした。引き続き、ネガレ
ジストを 1μm の厚さに塗布した。このレジストは、接
合上部のみを開口させるよう加工した後、層間絶縁膜６
として利用した（図−ｂ）。次に、厚さ 1.2μmのAu膜
７を上部 Y-Ba-Cu-O系酸化物超電導体膜４へのコンタク
トリードとして形成し（図−ｃ）、最後にイオンミリン
グによって電圧、電流リードを分離した（図−ｄ）。Next, the above-mentioned three-layer film is processed by a lithographic process so that the junction area is 10 μm ×
A 10 μm Josephson device was prepared. First, the upper YB
1.2 μm thick Au film 5 on a-Cu-O oxide superconductor film 4
After forming, the Au film 5, the upper Y-Ba-Cu-O-based oxide superconductor film 4 and the LaNiO 3 film 3 were etched to a width of 10 μm by argon ion milling. Subsequently, a negative resist was applied to a thickness of 1 μm. This resist is processed so that only the upper portion of the junction is opened, and then the interlayer insulating film 6 is formed.
It was used as (Fig.-b). Next, a 1.2 μm thick Au film 7 is formed as a contact lead to the upper Y-Ba-Cu-O-based oxide superconductor film 4 (Fig. C), and finally, voltage and current leads are formed by ion milling. Separated (Figure-d).
【００２４】得られたジョセフソン素子の電流−電圧特
性を図２に示す。この特性は、弱結合特性（ RSJモデ
ル）によく一致し、この素子が確かにジョセフソン素子
であることを強く支持している。また、Ｉc ・Ｒn積は
約 1.5mVと、実用上十分な値を示した。さらに、磁場を
印加することにより、臨界電流の変化を測定したとこ
ろ、図３に示すように、フラウンホーファー型の依存性
を示し、接合内を流れる電流に偏りのない良好なジョセ
フソン素子であることが確認された。The current-voltage characteristics of the obtained Josephson device are shown in FIG. This characteristic is in good agreement with the weak coupling characteristic (RSJ model), and strongly supports that this element is a Josephson element. Further, the I c · R n product was about 1.5 mV, which was a practically sufficient value. Furthermore, when a change in the critical current was measured by applying a magnetic field, as shown in FIG. 3, it was a good Josephson device which showed a Fraunhofer-type dependence and showed no bias in the current flowing in the junction. It was confirmed.
【００２５】実施例２ Y-Ba-Cu-O系酸化物超電導体膜（膜厚400nm)／Pr-Ba-Cu-
O系導電性酸化物膜（膜厚50nm）／ Y-Ba-Cu-O系酸化物
超電導体膜（膜厚400nm)の 3層積層膜構造を、実施例１
と同様な方法によって形成した。ただし、Pr-Ba-Cu-O系
導電性酸化物膜の成膜は、成膜する際の基板温度、Ar/O
2 混合比、基板とターゲットとの距離を変化させ、種々
の条件下で行った。基板温度は600℃〜 750℃の範囲
で、Ar/O2 混合比は O2 量を 30%〜 70%の範囲で、基板
とターゲットとの距離は15cm〜30cmの範囲で変化させ
た。Example 2 Y-Ba-Cu-O-based oxide superconductor film (film thickness 400 nm) / Pr-Ba-Cu-
A three-layer laminated film structure of an O-based conductive oxide film (film thickness 50 nm) / Y-Ba-Cu-O-based oxide superconductor film (film thickness 400 nm) was formed in Example 1
It was formed by a method similar to. However, the film formation of the Pr-Ba-Cu-O-based conductive oxide film depends on the substrate temperature during the film formation, Ar / O
2 The mixing ratio and the distance between the substrate and the target were changed and the measurement was performed under various conditions. The substrate temperature in the range of 600 ° C.-750 ° C., Ar / O 2 mixing ratio in the range of O 2 amounts of 30% to 70%, the distance between the substrate and the target was varied in the range of 15Cm～30cm.
【００２６】上記各種の条件下で作製した 3層積層膜に
おいて、Pr-Ba-Cu-O系導電性酸化物膜に加わった歪の大
きさとジョセフソン特性との相関を調べた。ここで、Pr
-Ba-Cu-O膜は、 Y-Ba-Cu-O膜上にエピタキシャル成長す
るが、Pr-Ba-Cu-O系導電性酸化物の格子定数が数％大き
いため、Pr-Ba-Cu-O膜には応力が加わった状態になって
おり、応力による歪によってその特性は著しく変化す
る。応力のかかり方およびそれによる格子定数の変化
は、 Y-Ba-Cu-O膜／Pr-Ba-Cu-O膜の界面の状況、特に点
欠陥、ディスロケーション、ボイド等の欠陥によって大
きく左右されると考えられる。これらは積層膜形成条件
に依存する。The correlation between the magnitude of strain applied to the Pr-Ba-Cu-O-based conductive oxide film and the Josephson characteristic in the three-layer laminated film produced under the above various conditions was examined. Where Pr
The -Ba-Cu-O film grows epitaxially on the Y-Ba-Cu-O film, but since the lattice constant of the Pr-Ba-Cu-O-based conductive oxide is a few percent larger, the Pr-Ba-Cu-O- The O film is in a stressed state, and its characteristics change significantly due to strain due to stress. How the stress is applied and the resulting change in the lattice constant are greatly influenced by the condition of the interface between the Y-Ba-Cu-O film / Pr-Ba-Cu-O film, especially the defects such as point defects, dislocations and voids. It is thought to be. These depend on the laminated film forming conditions.
【００２７】上記した各種の条件下で作製した 3層積層
膜をそれぞれ用いて、実施例１と同様なプロセスを用い
て、ジョセフソン素子を15個の作製し、それらの特性の
評価を行った。Using each of the three-layer laminated films produced under the various conditions described above, 15 Josephson devices were produced by the same process as in Example 1, and their characteristics were evaluated. ..
【００２８】上下の Y-Ba-Cu-O膜が明らかにショートし
ていると思われる（磁束フロータイプの電流−電圧特性
を示す） 3個の素子を除き、全て弱結合型（ RSJ型）の
電流−電圧特性を示し、その臨界電流はフラウンホーフ
ァー型の磁場依存性を示したが、その値自体は様々であ
った。そこで、Pr-Ba-Cu-O膜の歪み量として、格子定数
の変化を知らべた。図４に、Pr-Ba-Cu-O膜の歪み量と接
合の臨界電流との関係を示す。It seems that the upper and lower Y-Ba-Cu-O films are apparently short-circuited (showing the current-voltage characteristics of the magnetic flux flow type) except for the three elements, which are all weakly coupled (RSJ type). Of the Fraunhofer type magnetic field dependence of the critical current, but the value itself was various. Therefore, the change of the lattice constant was known as the strain amount of the Pr-Ba-Cu-O film. FIG. 4 shows the relationship between the amount of strain in the Pr-Ba-Cu-O film and the critical current of the junction.
【００２９】図４から明らかなように、接合の臨界電流
はPr-Ba-Cu-O膜の歪み量と明らかな相関があり、Pr-Ba-
Cu-O膜に応力を加えることにより、 Y-Ba-Cu-O系酸化物
超電導体膜／Pr-Ba-Cu-O系導電性酸化物膜／ Y-Ba-Cu-O
系酸化物超電導体膜の 3層積層膜構造を有するジョセフ
ソン素子の特性を大きく改善できることが分かる。As is clear from FIG. 4, the critical current of the junction has a clear correlation with the strain amount of the Pr-Ba-Cu-O film, and the Pr-Ba-
By applying stress to the Cu-O film, Y-Ba-Cu-O-based oxide superconductor film / Pr-Ba-Cu-O-based conductive oxide film / Y-Ba-Cu-O
It can be seen that the characteristics of the Josephson device having a three-layer laminated film structure of oxide-based oxide superconductor film can be greatly improved.
【００３０】[0030]
【発明の効果】以上説明したように本発明によれば、酸
化物超電導体／常伝導体／酸化物超電導体による積層型
ジョセフソン素子において、常伝導体としてスピン 1/2
の銅イオンを含まない、あるいは減少せしめた導電性酸
化物を用いているため、実用上重要なＩc ・Ｒn 積が大
きく、かつ制御性に優れた超電導素子を再現性よく提供
することが可能となる。As described above, according to the present invention, in a laminated Josephson device composed of oxide superconductor / normal conductor / oxide superconductor, spin 1/2 is used as a normal conductor.
Since a conductive oxide containing no or reduced copper ion is used, it is possible to provide a superconducting element having a large practically important I c · R n product and excellent controllability with good reproducibility. It will be possible.
【図１】本発明の一実施例における超電導素子の製造工
程を示す断面図である。FIG. 1 is a cross-sectional view showing a manufacturing process of a superconducting element according to an embodiment of the present invention.
【図２】本発明の一実施例によるジョセフソン素子の電
流−電圧特性を示す図である。FIG. 2 is a diagram showing a current-voltage characteristic of a Josephson device according to an embodiment of the present invention.
【図３】本発明の一実施例によるジョセフソン素子の臨
界電流の磁場依存性を示す図である。FIG. 3 is a diagram showing a magnetic field dependence of a critical current of a Josephson device according to an example of the present invention.
【図４】Y-Ba-Cu-O膜／Pr-Ba-Cu-O膜／ Y-Ba-Cu-O膜の
3層積層膜構造を有するジョセフソン素子の臨界電流とP
r-Ba-Cu-O膜の格子定数との相関を示す図である。[Fig. 4] Y-Ba-Cu-O film / Pr-Ba-Cu-O film / Y-Ba-Cu-O film
Critical current and P of Josephson device with 3-layer structure
It is a figure which shows the correlation with the lattice constant of a r-Ba-Cu-O film.
１…… SrTiO3 基板 ２……下部 YBa2 Cu3 O 7-δ膜 ３…… LaNiO3 膜 ４……上部 YBa2 Cu3 O 7-δ膜1 …… SrTiO 3 substrate 2 …… Lower YBa 2 Cu 3 O 7-δ film 3 …… LaNiO 3 film 4 …… Upper YBa 2 Cu 3 O 7-δ film
───────────────────────────────────────────────────── フロントページの続き (72)発明者 砂井 正之 神奈川県川崎市幸区小向東芝町１番地 株 式会社東芝総合研究所内 (72)発明者 吉田 二朗 神奈川県川崎市幸区小向東芝町１番地 株 式会社東芝総合研究所内 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masayuki Sunai, No. 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa, Toshiba Research Institute Co., Ltd. (72) Jiro Yoshida Komukai, Kouki-ku, Kawasaki-shi, Kanagawa Toshiba Town No. 1 Incorporated company Toshiba Research Institute
Claims (1)
導体によって構成したジョセフソン接合を有する超電導
素子において、 前記常伝導体が有するスピン磁気モーメントは、 1/2未
満であることを特徴とする超電導素子。1. In a superconducting device having a Josephson junction composed of oxide superconductor / normal conductor / oxide superconductor, the spin magnetic moment of the normal conductor is less than 1/2. And a superconducting element.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3247722A JP2856577B2 (en) | 1991-09-26 | 1991-09-26 | Superconducting element |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3247722A JP2856577B2 (en) | 1991-09-26 | 1991-09-26 | Superconducting element |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0590654A true JPH0590654A (en) | 1993-04-09 |
| JP2856577B2 JP2856577B2 (en) | 1999-02-10 |
Family
ID=17167705
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3247722A Expired - Fee Related JP2856577B2 (en) | 1991-09-26 | 1991-09-26 | Superconducting element |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2856577B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6769699B2 (en) | 2000-09-01 | 2004-08-03 | Nok Corporation | Cover gasket for hard disk device |
-
1991
- 1991-09-26 JP JP3247722A patent/JP2856577B2/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6769699B2 (en) | 2000-09-01 | 2004-08-03 | Nok Corporation | Cover gasket for hard disk device |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2856577B2 (en) | 1999-02-10 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US5627139A (en) | High-temperature superconducting josephson devices having a barrier layer of a doped, cubic crystalline, conductive oxide material | |
| US5380704A (en) | Superconducting field effect transistor with increased channel length | |
| Takano et al. | A cross-whiskers junction as a novel fabrication process for intrinsic Josephson junctions | |
| JPH0834320B2 (en) | Superconducting element | |
| JP2856577B2 (en) | Superconducting element | |
| EP0482198B1 (en) | Superconducting tunnel junction element comprising a magnetic oxide material and its use | |
| JPH11346010A (en) | Photodetector | |
| Müller | The first five years of high-Tc superconductivity | |
| JPS63299281A (en) | Superconducting device | |
| CA2099224C (en) | A single-phase superconductive metal oxide and method of manufacturing the same | |
| JPH02391A (en) | Superconductive field-effect transistor | |
| JP2585269B2 (en) | Superconducting transistor | |
| JP2679610B2 (en) | Superconducting element manufacturing method | |
| JP3076503B2 (en) | Superconducting element and method of manufacturing the same | |
| JP2867956B2 (en) | Superconducting transistor | |
| JP2786827B2 (en) | Superconducting element | |
| JP3328698B2 (en) | Intrinsic Josephson-type superconducting tunnel junction device | |
| JP2955407B2 (en) | Superconducting element | |
| JP2829173B2 (en) | Superconducting element | |
| Schwarz | High temperature superconductors: Theory, developments, perspectives | |
| JPH07101759B2 (en) | Superconducting element | |
| JP2768276B2 (en) | Oxide superconducting junction element | |
| JP2868286B2 (en) | Superconducting element and circuit element having the same | |
| JPH05335640A (en) | Superconductive element | |
| EP0571633A1 (en) | Superconductive element |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 19981027 |
|
| S111 | Request for change of ownership or part of ownership |
Free format text: JAPANESE INTERMEDIATE CODE: R313115 |
|
| R350 | Written notification of registration of transfer |
Free format text: JAPANESE INTERMEDIATE CODE: R350 |
|
| LAPS | Cancellation because of no payment of annual fees |