JP3021764B2 - Oxide superconductor thin film - Google Patents
Oxide superconductor thin filmInfo
- Publication number
- JP3021764B2 JP3021764B2 JP3115350A JP11535091A JP3021764B2 JP 3021764 B2 JP3021764 B2 JP 3021764B2 JP 3115350 A JP3115350 A JP 3115350A JP 11535091 A JP11535091 A JP 11535091A JP 3021764 B2 JP3021764 B2 JP 3021764B2
- Authority
- JP
- Japan
- Prior art keywords
- thin film
- oxide superconductor
- atomic layer
- layer
- composition
- 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 - Lifetime
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Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/60—Superconducting electric elements or equipment; Power systems integrating superconducting elements or equipment
Landscapes
- Inorganic Compounds Of Heavy Metals (AREA)
- Crystals, And After-Treatments Of Crystals (AREA)
- Superconductors And Manufacturing Methods Therefor (AREA)
Description
【0001】[0001]
【産業上の利用分野】本発明は、ミリ波・マイクロ波デ
バイス等の導体として好適な酸化物超電導体薄膜に関す
る。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxide superconductor thin film suitable as a conductor for a millimeter-wave / microwave device or the like.
【0002】[0002]
【従来の技術】5年前にTc(臨界温度)が30Kの
(Ba,La)−O,Cu−O等の原子層が層状に配列
したペロブスカイト関連のK2 N2F4 型構造のBa−
La−Cu−O系超電体が発見され、その後ペロブスカ
イト関連の似た構造の、Tcが液体窒素温度(77K)
を超えるYBaCuO系,BiSrCaCuO系,Tl
BaCaCuO系等の酸化物超電導体が次々に発見され
るに到って、酸化物超電導体に関して、超電導機構の解
明とともに、電力応用,強磁場応用,エレクトロニクス
応用等の実用化に向けた研究が大いに進展した。ところ
で、エレクトロニクス分野への応用には、酸化物超電導
体の薄膜化技術が必須であり、これまでに、スパッタリ
ング法,レーザー蒸着法,各種の物理気相蒸着法(PV
D法)や化学蒸着法(CVD法)等の応用研究がなされ
てきた。しかしながら、上記のような従来法により作製
される酸化物超電導体薄膜は表面抵抗が大きく、ミリ波
・マイクロ波デバイス等に応用するには不適当なもので
あった。2. Description of the Related Art Five years ago, perovskite-related K 2 N 2 F 4 type Ba in which atomic layers of (Ba, La) —O, Cu—O, etc. having a Tc (critical temperature) of 30 K are arranged in layers. −
La-Cu-O-based superconductor was discovered, and Tc of similar structure related to perovskite was changed to liquid nitrogen temperature (77K).
YBaCuO-based, BiSrCaCuO-based, Tl
As oxide superconductors such as BaCaCuO are discovered one after another, research on oxide superconductors, including elucidation of the superconducting mechanism and practical application of electric power application, strong magnetic field application, electronics application, etc., has been greatly performed. Evolved. By the way, thinning technology of oxide superconductors is indispensable for application to the electronics field. Up to now, sputtering, laser deposition, various physical vapor deposition (PV)
D) and chemical vapor deposition (CVD). However, the oxide superconductor thin film produced by the conventional method as described above has a large surface resistance, and is unsuitable for application to millimeter-wave / microwave devices and the like.
【0003】[0003]
【課題を解決する為の手段】本発明はかかる状況に鑑
み、表面抵抗の小さい薄膜の作製方法について、鋭意研
究を行った結果、従来のPVD法やCVD法により作製
された酸化物超電導体薄膜の表面抵抗が大きい理由は、
蒸発源に酸化物超電導体の構成元素を全て含む単一のタ
ーゲットを用い、或いは構成元素別ターゲットを同時に
蒸着させる方法により作製する為、組成制御はできるが
構造制御性が悪く、又薄膜の表面に異相が析出したりす
ることによること、即ち、酸化物超電導体を構成する原
子層の積み重ね方によって表面抵抗が著しく相違するこ
とを知見し、更に研究を重ねて本発明を完成するに到っ
たものである。即ち、本発明は、基板上に形成された、
Cuを構成元素として含有する酸化物超電導体薄膜であ
って、前記薄膜の結晶のC軸が基板面の垂線方向に配向
しており、且つ前記薄膜の最上層に伝導性のCu−O原
子層が形成されていることを特徴とするものである。In view of the foregoing, the present invention has made intensive studies on a method of forming a thin film having a small surface resistance. As a result, an oxide superconductor thin film formed by a conventional PVD method or CVD method has been obtained. The reason why the surface resistance of
Since a single target containing all the constituent elements of the oxide superconductor is used as the evaporation source, or the target is prepared by vapor deposition of the constituent elements at the same time, the composition can be controlled but the structure controllability is poor, and the surface of the thin film And that the surface resistance is significantly different depending on how the atomic layers constituting the oxide superconductor are stacked, and further studies have been completed to complete the present invention. It is a thing. That is, the present invention relates to a method of forming on a substrate,
An oxide superconductor thin film containing Cu as a constituent element, wherein a C axis of a crystal of the thin film is oriented in a direction perpendicular to a substrate surface, and a conductive Cu—O atomic layer is formed on an uppermost layer of the thin film. Are formed.
【0004】本発明の酸化物超電導体薄膜とは、Bi2
Sr2 Ca2 Cu3 OY 組成、又はBi2 Sr2 Ca1
Cu2 OY 組成、又はTl2 Ba2 Ca2 Cu3 OZ 組
成、又はTl2 Ba2 Ca1 Cu2 OZ 組成、又は一般
式LnBa2 Cu3O7-x (式中LnはY及びランタノ
イド金属元素の中の1元素又は複数元素)で示される組
成等のCuを構成元素として含有する酸化物超電導体全
般を指すものである。前記のBi2 Sr2 Ca2 Cu3
OY 〔以下Bi系(2223)と略記〕組成又はBi2
Sr2 Ca1 Cu2 OY 〔以下Bi系(2212)と略
記〕組成の酸化物超電導体は、図1イ,ロにその結晶の
単位格子をそれぞれ示したように、前者はBi−O,B
i−O,Sr−O,Cu−O,Ca,CuO鎖,Ca,
Cu−O,Sr−O,Bi−O,Bi−O,Sr−O,
Cu−O,Ca,CuO鎖,Ca,Cu−O,Sr−O
の各々の原子層が順次積層して単位格子を作るペロブス
カイト構造の複合酸化物で、この酸化物超電導体におけ
る伝導性Cu−O原子層とは図1イで矢印で指したSr
−O原子層とCa原子層とに挟まれたCu−O原子層の
ことである。[0004] The oxide superconductor thin film of the present invention refers to Bi 2
Sr 2 Ca 2 Cu 3 O Y composition or Bi 2 Sr 2 Ca 1
Cu 2 O Y composition, or Tl 2 Ba 2 Ca 2 Cu 3 O Z composition, or Tl 2 Ba 2 Ca 1 Cu 2 O Z composition, or the general formula LnBa 2 Cu 3 O 7-x (where Ln is Y and It refers to all oxide superconductors containing Cu as a constituent element, such as a composition represented by one or more of the lanthanoid metal elements. Bi 2 Sr 2 Ca 2 Cu 3
O Y [hereinafter abbreviated as Bi system (2223)] composition or Bi 2
An oxide superconductor having a composition of Sr 2 Ca 1 Cu 2 O Y [hereinafter abbreviated as Bi-based (2212)] has a unit cell of crystal as shown in FIGS. B
i-O, Sr-O, Cu-O, Ca, CuO chain, Ca,
Cu-O, Sr-O, Bi-O, Bi-O, Sr-O,
Cu-O, Ca, CuO chain, Ca, Cu-O, Sr-O
Is a composite oxide having a perovskite structure in which each atomic layer is sequentially laminated to form a unit lattice. The conductive Cu—O atomic layer in this oxide superconductor is Sr indicated by an arrow in FIG.
It is a Cu-O atomic layer sandwiched between a -O atomic layer and a Ca atomic layer.
【0005】又、後者はBi−O,Bi−O,Sr−
O,Cu−O,Ca,Cu−O,Sr−O,Bi−O,
Bi−O,Sr−O,Cu−O,Ca,Cu−O,Sr
−Oの各々の原子層が順次積層して単位格子を作るペロ
ブスカイト構造の複合酸化物で、伝導性Cu−O原子層
とは矢印で指したやはりSr−O原子層とCa原子層で
挟まれたCu−O原子層である。又、Tl2 Ba2 Ca
2 Cu3 OZ 〔以下Tl系(2223)と略記〕組成、
又はTl2 Ba2 Ca1 Cu2 OZ 〔以下Tl系(22
12)と略記〕組成の酸化物超電導体は、図2イ,ロに
その結晶の単位格子をそれぞれ示したように図1イ,ロ
に示したBi系(2223)組成及びBi系(221
2)組成の酸化物超電導体のBiをTlに、SrをBa
にそれぞれ代えた酸化物超電導体であって、伝導性Cu
−O原子層はBa−O原子層とCa原子層で挟まれた矢
印で指したCu−O原子層である。尚、前記のCuO鎖
とは、Cuサイトの上下に頂点酸素を持たず、Cu原子
とO原子とが交互に正方形CuO4 を形成したもので、
Cu原子が平面型4配位をとっているものである。The latter is Bi-O, Bi-O, Sr-
O, Cu-O, Ca, Cu-O, Sr-O, Bi-O,
Bi-O, Sr-O, Cu-O, Ca, Cu-O, Sr
-O is a composite oxide having a perovskite structure in which each atomic layer is sequentially laminated to form a unit cell. The conductive Cu-O atomic layer is also sandwiched between the Sr-O atomic layer and the Ca atomic layer indicated by arrows. A Cu—O atomic layer. Also, Tl 2 Ba 2 Ca
2 Cu 3 O Z [hereinafter abbreviated as Tl (2223)] composition,
Or Tl 2 Ba 2 Ca 1 Cu 2 O Z [hereinafter referred to as Tl-based (22
12) The oxide superconductor having the composition shown in FIGS. 2A and 2B shows the Bi-based (2223) composition and the Bi-based (2211) shown in FIGS.
2) Bi of the composition oxide superconductor is set to Tl and Sr is set to Ba.
Oxide superconductors, each of which has conductive Cu
The -O atomic layer is a Cu-O atomic layer indicated by an arrow sandwiched between a Ba-O atomic layer and a Ca atomic layer. Incidentally, the above-mentioned CuO chain has no vertex oxygen above and below the Cu site, and a Cu atom and an O atom alternately form a square CuO 4 ,
Cu atoms have a planar four-coordinate configuration.
【0006】又、一般式LnBa2 Cu3 O7-x (式中
LnはY及びランタノイド金属元素の中の1元素又は複
数元素)で示される組成の酸化物超電導体の結晶の単位
格子は図3に示したように、例えばCu−O,Ba−
O,CuO鎖,Ba−O,Cu−O,Y,Cu−O,B
a−O,CuO鎖,Ba−O,Cu−O,Yの各々の原
子層を順次積み上げて形成したものであって、この酸化
物超電導体の伝導性Cu−O原子層は、Ba−O原子層
とY原子層とに挟まれた矢印で指したCu−O原子面で
ある。尚、上記のCuO鎖とは、CuとO原子とが交互
に直線状に配列したもので、Cuが直線型2配位をとっ
ている。これはCuを含むが、超電導状態にならない層
である。又前記一般式中のLnはY及びランタノイド金
属元素の中の1種又は複数種の元素で、ランタノイド金
属元素とは、La,Ce,Pr,Nd,Er,Ho等で
ある。本発明の酸化物超電導体薄膜は、酸化物超電導体
を構成する原子層の伝導性のCu−O原子層を薄膜の最
上層に配置するもので、かかる積層構造の酸化物超電導
体薄膜は、例えば分子線エピタキシー(MBE)装置を
用い、構成元素を所定の順序で1原子層ずつ蒸着させて
作製することができる。The unit cell of a crystal of an oxide superconductor having a composition represented by a general formula LnBa 2 Cu 3 O 7-x (where Ln is one or more of Y and a lanthanoid metal element) is shown in FIG. As shown in FIG. 3, for example, Cu—O, Ba—
O, CuO chain, Ba-O, Cu-O, Y, Cu-O, B
a-O, CuO chains, Ba-O, Cu-O, Y are formed by sequentially stacking atomic layers. The conductive Cu-O atomic layer of this oxide superconductor is formed of Ba-O It is a Cu-O atomic plane pointed by an arrow between an atomic layer and a Y atomic layer. The above-mentioned CuO chain is one in which Cu and O atoms are alternately arranged in a linear manner, and Cu has a linear two-coordination. This is a layer containing Cu but not in a superconducting state. Ln in the above general formula is one or more of Y and the lanthanoid metal element, and the lanthanoid metal element is La, Ce, Pr, Nd, Er, Ho or the like. The oxide superconductor thin film of the present invention is one in which a conductive Cu-O atomic layer of an atomic layer constituting the oxide superconductor is arranged on the uppermost layer of the thin film. For example, it can be manufactured by using a molecular beam epitaxy (MBE) apparatus to deposit constituent elements one by one atomic layer in a predetermined order.
【0007】以下に、本発明の酸化物超電導体薄膜の製
造方法の具体例を図を参照して説明する。図4は本発明
の薄膜を製造する為の分子線エピタキシー(MBE)装
置の要部説明図である。このMBE装置は、チャンバー
1内に、蒸発源を入れる複数のセルa,b,c,dと前
記蒸発源から発生するガスを堆積させる為の基板2とを
対向配置させて構成したものである。前記セルa〜dに
は、蒸発源を加熱する為のヒーター3と基板2への蒸着
量を制御する為のシャッターイ,ロ,ハ,ニと蒸発速度
をモニターする水晶振動式膜厚計4がそれぞれ設けられ
ている。前記膜厚計4の計測結果はヒーター3及びシャ
ッターイ〜ニにフィードバックされて、基板2上に蒸着
する原子層の種類及び厚さが自動的に制御される。又酸
化物超電導体薄膜を形成する基板2にもヒーター13が付
いていて、基板温度をコントロールして酸化物超電導体
薄膜の結晶構造が調整される。チャンバー1内は、排気
用ポンプ5により圧力調節バルブ6を通して所定圧力に
排気される。セルa〜d近傍は蒸発源の酸化防止の為、
5×10-7Torrの高真空に保持され、他方、基板2
近傍には、基板2上に形成される蒸着膜への酸素取込み
が促進されるように、酸素原子を遊離し得るO3 やN2
O等の活性ガスをボンベ7からマスフローメーター8を
通しノズル9より吹付ける。基板2とセルa〜d間には
双方の真空度の差を保持する為差動排気板10が配置され
ている。A specific example of the method for producing an oxide superconductor thin film of the present invention will be described below with reference to the drawings. FIG. 4 is an explanatory view of a main part of a molecular beam epitaxy (MBE) apparatus for producing a thin film of the present invention. This MBE apparatus has a structure in which a plurality of cells a, b, c, and d for accommodating an evaporation source and a substrate 2 for depositing a gas generated from the evaporation source are arranged to face each other in a chamber 1. . The cells a to d are provided with a heater 3 for heating the evaporation source, shutters B, C, D for controlling the amount of vapor deposition on the substrate 2 and a quartz vibrating film thickness meter 4 for monitoring the evaporation rate. Are provided respectively. The measurement result of the film thickness meter 4 is fed back to the heater 3 and the shutters I to D to automatically control the type and thickness of the atomic layer deposited on the substrate 2. The substrate 2 on which the oxide superconductor thin film is to be formed is also provided with a heater 13 for controlling the substrate temperature to adjust the crystal structure of the oxide superconductor thin film. The inside of the chamber 1 is evacuated to a predetermined pressure through a pressure control valve 6 by an exhaust pump 5. In the vicinity of the cells a to d, in order to prevent oxidation of the evaporation source,
The substrate is kept in a high vacuum of 5 × 10 −7 Torr, while the substrate 2
In the vicinity, O 3 or N 2 which can release oxygen atoms is provided so that oxygen incorporation into the deposited film formed on the substrate 2 is promoted.
An active gas such as O is blown from a nozzle 9 through a mass flow meter 8 from a cylinder 7. A differential pumping plate 10 is arranged between the substrate 2 and the cells a to d in order to maintain a difference between the two degrees of vacuum.
【0008】次に、前記MBE装置を用いて、図1イに
示した結晶構造の酸化物超電導体薄膜を基板上に形成す
る方法について説明する。図4に示した装置のセル、
a,b,c,dに蒸発源として、例えばBi2 O3 ,S
r,Ca,Cuをそれぞれ充填し、前記セル、a〜dの
各々のシャッター(イ)〜(ニ)を、例えばハ,ニ,
ハ,ニ,ロ,イ,イ,ロ,ニ,ハ,ニ,ハ,ニ,ロ,
イ,イ,ロ,ニの順序で1個づつ所定時間開いて、基板
上に単位格子を構成するCa,CuO鎖,Ca,Cu−
O,Sr−O,Bi−O,Bi−O,Sr−O,Cu−
O,Ca,CuO鎖,Ca,Cu−O,Sr−O,Bi
−O,Bi−O,Sr−O,Cu−Oの原子層を順次積
み上げて単位格子を形成し、この操作を複数回繰り返し
て最上層にCu−O層が形成されたBi系(2223)
組成の酸化物超電導体薄膜を製造する。上記において、
最上層に形成するCu−O原子層は、単位格子中に現れ
るSr−O原子層とCa原子層に挟まれた伝導性Cu−
O原子層である。又酸化物超電導体薄膜は、前記単位格
子の整数倍を積み上げて製造すると薄膜全体の電荷が中
性化されるので特性上好ましく、その場合基板上に形成
される第一層は、必然的にSr−O又はCa原子層のい
ずれかの層であることが要求される。Next, a method for forming an oxide superconductor thin film having a crystal structure shown in FIG. 1A on a substrate by using the MBE apparatus will be described. A cell of the device shown in FIG. 4,
a, b, c, and d as evaporation sources, for example, Bi 2 O 3 , S
r, Ca, and Cu, respectively, and shutters (a) to (d) of the cells, a to d, for example, c, d,
Ha, ni, ro, i, i, ro, ni, ha, ni, ha, ni, ro,
Open one by one in the order of b, b, c, and c to form a unit cell on the substrate.
O, Sr-O, Bi-O, Bi-O, Sr-O, Cu-
O, Ca, CuO chain, Ca, Cu-O, Sr-O, Bi
-A, Bi-O (2223) in which atomic layers of -O, Bi-O, Sr-O, and Cu-O are sequentially stacked to form a unit cell, and this operation is repeated a plurality of times to form a Cu-O layer on the uppermost layer.
An oxide superconductor thin film having a composition is manufactured. In the above,
The Cu—O atomic layer formed on the uppermost layer is a conductive Cu—O layer sandwiched between the Sr—O atomic layer and the Ca atomic layer that appear in the unit cell.
It is an O atomic layer. When the oxide superconductor thin film is manufactured by stacking an integral multiple of the unit cell, the charge of the entire thin film is neutralized, so that it is preferable in terms of characteristics. It is required to be a layer of either Sr-O or Ca atomic layer.
【0009】又図1ロに示した結晶構造のBi系(22
12)組成の酸化物超電導体薄膜は、シャッター(イ)
〜(ニ)をハ,ニ,ロ,イ,イ,ロ,ニ,ハ,ニ,ロ,
イ,イ、ロ、ニの順序で1個づつ所定時間開いて、基板
上に単位格子を構成するCa,Cu−O,Sr−O,B
i−O,Bi−O,Sr−O,Cu−O,Ca,Cu−
O,Sr−O,Bi−O,Bi−O,Sr−O,Cu−
Oの各々の原子層を順次積み上げて単位格子を形成し、
この操作を複数回繰り返して最上層にCu−O原子層を
形成して製造される。上記において、最上層に形成する
Cu−O原子層は、単位格子中に現れるSr−O原子層
とCa原子層に挟まれた伝導性Cu−O原子層であり、
基板上に第一層としてSr−O原子層又はCa原子層の
いずれかを形成し、以下単位格子の整数倍を積み上げる
と最上層に伝導性Cu−O原子層が形成され、しかも薄
膜全体の電荷が中性化される。Further, the Bi system (22) having the crystal structure shown in FIG.
12) The oxide superconductor thin film of the composition
To (d), ha, d, b, i, i, b, d, c, d, b,
Open one by one for a predetermined time in the order of a, b, b and c to form Ca, Cu-O, Sr-O, B
i-O, Bi-O, Sr-O, Cu-O, Ca, Cu-
O, Sr-O, Bi-O, Bi-O, Sr-O, Cu-
Each atomic layer of O is sequentially stacked to form a unit cell;
This operation is repeated a plurality of times to form a Cu—O atomic layer on the uppermost layer, thereby manufacturing the semiconductor device. In the above, the Cu-O atomic layer formed on the uppermost layer is a conductive Cu-O atomic layer sandwiched between the Sr-O atomic layer and the Ca atomic layer appearing in the unit cell,
Forming either a Sr-O atomic layer or a Ca atomic layer as a first layer on a substrate, and stacking an integral multiple of the unit cell below, forms a conductive Cu-O atomic layer on the uppermost layer, and furthermore, the entire thin film The charge is neutralized.
【0010】図2イ,ロに示したTl2 Ba2 Ca2 C
u3 OZ 組成又はTl2 Ba2 Ca1 Cu2 OZ 組成の
酸化物超電導体の結晶の単位格子は、前述したように、
図1イ,ロに示したBi系(2223)組成又はBi系
(2212)組成のBi及びSrをそれぞれTl及びB
aに代えたものであり、各々の原子層の積み上げ方法
は、Bi系酸化物超電導体の場合と同じ方法によりなさ
れる。この酸化物超電導体薄膜の場合は、基板面上の第
1層には、Ba−O又はCa原子層を配置し、この上に
単位格子を整数倍積み上げると最上層に伝導性のCu−
O原子層が位置する。図3に示した一般式LnBa2 C
u3 O7-x (式中LnはY及びランタノイド金属元素の
中の1元素又は複数元素)で示される組成の酸化物超電
導体は、Ba−O,CuO鎖,Ba−O,Cu−O,
Y,Cu−O,Ba−O,CuO鎖,Ba−O,Cu−
O,Y,Cu−O,の各々の原子層を順次積み上げて形
成するものであって、この酸化物超電導体薄膜の場合
は、基板面上の第一層に、Ba−O又はY原子層を配置
し、この上に単位格子を整数倍積み上げると最上層にC
u−O原子層が位置し、且つ酸化物超電導体薄膜全体の
電荷が中性化される。The Tl 2 Ba 2 Ca 2 C shown in FIGS.
The unit cell of the crystal of the oxide superconductor having the u 3 O Z composition or the Tl 2 Ba 2 Ca 1 Cu 2 O Z composition is, as described above,
Bi and Sr of the Bi-based (2223) composition or Bi-based (2212) composition shown in FIGS.
The method of stacking each atomic layer is the same as that of the Bi-based oxide superconductor. In the case of this oxide superconductor thin film, a Ba—O or Ca atomic layer is arranged on the first layer on the substrate surface, and a unit cell is stacked thereon by an integral multiple to form a conductive Cu— layer on the uppermost layer.
The O atomic layer is located. The general formula LnBa 2 C shown in FIG.
An oxide superconductor having a composition represented by u 3 O 7-x (where Ln is one or more of Y and a lanthanoid metal element) is made of Ba—O, CuO chain, Ba—O, Cu—O ,
Y, Cu-O, Ba-O, CuO chain, Ba-O, Cu-
O, Y, and Cu—O are formed by sequentially stacking atomic layers. In the case of this oxide superconductor thin film, a Ba—O or Y atomic layer is formed on the first layer on the substrate surface. Is placed on top of this, and a unit cell is piled up on the whole by an integral number.
The u-O atomic layer is located, and the charge of the entire oxide superconductor thin film is neutralized.
【0011】[0011]
【作用】本発明の酸化物超電導体薄膜は、Cuを構成元
素とする酸化物超電導体を基板上にC軸配向させて形成
し、最上層に超電導状態に寄与する伝導性Cu−O原子
層を位置させたものなので、表面抵抗が小さい。The oxide superconductor thin film of the present invention is formed by forming an oxide superconductor containing Cu as a constituent element on a substrate with a C-axis orientation, and forming a conductive Cu—O atomic layer contributing to the superconducting state on the uppermost layer. Surface resistance is low.
【0012】[0012]
【実施例】以下に本発明を実施例により詳細に説明す
る。 実施例1 図4に示したMBE装置により、Bi系(2223)組
成の酸化物超電導体薄膜をLaAlO3 単結晶基板の
(100)面上に3000Åの厚さに形成した。蒸発源
として、セルa,b,c,dにBi2 O3 ,Sr,C
a,Cuをそれぞれ充填し、各々をヒーターにより82
0℃,800℃,850℃,1100℃に加熱した。蒸
発速度は、各々の蒸発量を水晶振動式膜厚計により計測
し、計測結果をそれぞれのシャッター(イ)〜(ニ)に
連動して蒸発源毎に1〜5Å/secの範囲の所定の速
度になるように自動制御した。シャッター(イ)〜
(ニ)は、前述の通り、ハ,ニ,ハ,ニ,ロ,イ,イ,
ロ,ニ,ハ,ニ,ハ,ニ,ロ,イ,イ,ロ,ニの順序で
1個づつ開いてCa,CuO鎖,Ca,Cu−O,Sr
−O,Bi−O,Bi−O,Sr−O,Cu−O,C
a,CuO鎖,Ca,Cu−O,Sr−O,Bi−O,
Bi−O,Sr−O,Cu−Oの各々の原子層を1層づ
つ上記順序で繰返し積み上げて最上層にCu−O層を形
成して、Bi系(2223)組成の酸化物超電導体薄膜
を製造した。 実施例2 実施例1において、シャッター(イ)〜(ニ)を、ハ,
ニ,ロ,イ,イ,ロ,ニ,ハ,ニ,ロ,イ,イ,ロ,ニ
の順序で1個づつ所定時間開いてCa,Cu−O,Sr
−O,Bi−O,Bi−O,Sr−O,Cu−O,C
a,Cu−O,Sr−O,Bi−O,Bi−O,Sr−
O,Cu−Oの各々の原子層を上記順序で1層づつ繰返
し積み上げて最上層にCu−O原子層を形成した他は、
実施例1と同じ方法によりBi系(2212)組成の酸
化物超電導体薄膜を製造した。The present invention will be described below in detail with reference to examples. Example 1 A Bi-based (2223) composition oxide superconductor thin film was formed to a thickness of 3000 ° on a (100) plane of a LaAlO 3 single crystal substrate by the MBE apparatus shown in FIG. As the evaporation source, cells a, b, c, Bi 2 O 3 to d, Sr, C
a and Cu, respectively, and each was filled with 82
Heated to 0 ° C, 800 ° C, 850 ° C, 1100 ° C. The evaporation rate is measured by a quartz vibrating film thickness meter for each evaporation amount, and the measurement results are linked to the respective shutters (a) to (d) in a predetermined range of 1 to 5 ° / sec for each evaporation source. Automatically controlled to reach speed. Shutter (A) ~
(D) is, as described above, ha, ni, ha, ni, ro, i, i, i,
B, d, c, d, d, d, d, d, d, d are opened one by one in the order of Ca, CuO chain, Ca, Cu-O, Sr.
—O, Bi—O, Bi—O, Sr—O, Cu—O, C
a, CuO chain, Ca, Cu-O, Sr-O, Bi-O,
Each atomic layer of Bi-O, Sr-O, and Cu-O is repeatedly stacked one by one in the above order to form a Cu-O layer on the uppermost layer, and a Bi-based (2223) composition oxide superconductor thin film Was manufactured. Example 2 In Example 1, shutters (a) to (d) were replaced by
D, b, b, b, b, b, b, b, b, b, b, c are opened one by one in the order of Ca, Cu-O, Sr.
—O, Bi—O, Bi—O, Sr—O, Cu—O, C
a, Cu-O, Sr-O, Bi-O, Bi-O, Sr-
Except that each atomic layer of O and Cu-O was repeatedly stacked one by one in the above order to form a Cu-O atomic layer on the uppermost layer,
An oxide superconductor thin film having a Bi-based (2212) composition was manufactured in the same manner as in Example 1.
【0013】実施例3 セルa,b,c,dに蒸発源として、それぞれTl2 O
3 ,Ba,Ca,Cuを充填し、ヒーターによりそれぞ
れを720℃,740℃,850℃,1100℃に加熱
し、前記セルの各々のシャッター(イ)〜(ニ)をハ,
ニ,ハ,ニ,ロ、イ,イ,ロ,ニ,ハ,ニ,ハ,ニ,
ロ,イ,イ,ロ,ニの順序で1個づつ所定時間開いてC
a,CuO鎖,Ca,Cu−O,Ba−O,Tl−O,
Tl−O,Ba−O,Cu−O,Ca,CuO鎖,C
a,Cu−O,Sr−O,Tl−O,Tl−O,Ba−
O,Cu−Oの各々の原子層を上記順序で1層づつ繰返
し積み上げて最上層にCu−O原子層を形成した他は、
実施例1と同じ方法によりTl系(2223)組成の酸
化物超電導体薄膜を製造した。 実施例4 実施例3において、シャッター(イ)〜(ニ)を、ハ,
ニ,ロ,イ,イ,ロ,ニ,ハ,ニ,ロ,イ,イ,ロ,ニ
の順序で1個づつ所定時間開いてCa,Cu−O,Ba
−O,Tl−O,Tl−O,Ba−O,Cu−O,C
a,Cu−O,Ba−O,Bi−O,Bi−O,Ba−
O,Cu−Oの各々の原子層を上記順序で1層づつ繰返
し積み上げて最上層にCu−O層を形成した他は、実施
例3と同じ方法によりTl系(2212)組成の酸化物
超電導体薄膜を製造した。 実施例5 セルa,bにそれぞれBa,Cuを充填し、各々の温度
を740℃,1100℃に加熱した。又Yは蒸発温度が
高いので、セルcの代わりにカーボン製るつぼを配置
し、この中にYを充填し電子銃で1450℃に加熱し
た。上記のカーボン製るつぼのシャッターには、ハのシ
ャッターを用いた。かくして、それぞれのシャッター
(イ)〜(ハ)を、ハ,ロ,イ,ロ,イ,ロ,ハ,ロ,
イ,ロ,イ,ロの順序で1個づつ所定時間開いて、Y,
Cu−O,Ba−O,CuO鎖,Ba−O,Cu−O,
Y,Cu−O,Ba−O,CuO鎖,Ba−O,Cu−
Oの各々の原子層を上記順序で1層づつ積み上げて最上
層にCu−O原子層を形成したYBaCuO系酸化物超
電導体薄膜を製造した。Embodiment 3 Tl 2 O was used as an evaporation source in cells a, b, c and d.
3 , Ba, Ca, and Cu were charged, and each was heated to 720 ° C., 740 ° C., 850 ° C., and 1100 ° C. by a heater, and shutters (a) to (d) of each of the cells were c and c.
Ni, ha, ni, ro, i, i, ro, ni, ha, ni, ha, ni,
Open one by one for a given time in the order of b, i, i, b, d
a, CuO chain, Ca, Cu-O, Ba-O, Tl-O,
Tl-O, Ba-O, Cu-O, Ca, CuO chain, C
a, Cu-O, Sr-O, Tl-O, Tl-O, Ba-
Except that each atomic layer of O and Cu-O was repeatedly stacked one by one in the above order to form a Cu-O atomic layer on the uppermost layer,
An oxide superconductor thin film having a Tl (2223) composition was produced in the same manner as in Example 1. Example 4 In Example 3, shutters (a) to (d) were replaced by
D, b, b, b, d, b, c, d, b, d are opened one by one in the order of Ca, Cu-O, Ba.
-O, Tl-O, Tl-O, Ba-O, Cu-O, C
a, Cu-O, Ba-O, Bi-O, Bi-O, Ba-
Oxide superconductivity of Tl (2212) composition was formed in the same manner as in Example 3 except that each atomic layer of O and Cu-O was repeatedly stacked one by one in the above order to form a Cu-O layer on the uppermost layer. A body thin film was manufactured. Example 5 Cells a and b were filled with Ba and Cu, respectively, and the respective temperatures were heated to 740 ° C. and 1100 ° C. Further, since Y has a high evaporation temperature, a carbon crucible was placed in place of cell c, Y was filled therein, and heated to 1450 ° C. with an electron gun. As the shutter of the above-mentioned carbon crucible, a shutter of Ha was used. Thus, each shutter (a) to (c) is called ha, ro, i, ro, i, ro, ha, ro,
Open one by one in the order of i, b, i, b
Cu-O, Ba-O, CuO chain, Ba-O, Cu-O,
Y, Cu-O, Ba-O, CuO chain, Ba-O, Cu-
Each atomic layer of O was stacked one by one in the above order to produce a YBaCuO-based oxide superconductor thin film having a Cu—O atomic layer formed on the uppermost layer.
【0014】比較例1 実施例1において、シャッター(イ)〜(ニ)を、ニ,
ハ,ニ,ハ,ニ,ロ,イ,イ,ロ,ニ,ハ,ニ,ハ,
ニ,ロ,イ,イ,ロの順序で1個づつ所定時間開く操作
を所要回数繰り返して最上層にSr−O原子層を形成し
た他は、実施例1と同じ方法によりBi系(2223)
組成の酸化物超電導体薄膜を製造した。 比較例2 実施例2において、シャッター(イ)〜(ニ)を、ニ,
ハ,ニ,ロ,イ,イ,ロ,ニ,ハ,ニ,ロ,イ,イ,ロ
の順序で1個づつ所定時間開く操作を所要回数繰り返し
て最上層にSr−O原子層を形成した他は、実施例2と
同じ方法によりBi系(2212)組成の酸化物超電導
体薄膜を製造した。 比較例3 実施例3において、シャッター(イ)〜(ニ)を、ニ,
ハ,ニ,ハ,ニ,ロ,イ,イ,ロ,ニ,ハ,ニ,ハ,
ニ,ロ,イ,イ,ロの順序で1個づつ所定時間開く操作
を所要回数繰り返して最上層にBa−O原子層を形成し
た他は、実施例3と同じ方法によりTl系(2223)
組成の酸化物超電導体薄膜を製造した。Comparative Example 1 In Example 1, the shutters (a) to (d) were replaced with
Ha, ni, ha, ni, ro, i, i, ro, ni, ha, ni, ha,
The Bi system (2223) is formed in the same manner as in the first embodiment except that the operation of opening one by one for a predetermined time in the order of d, b, a, b, and b is repeated a required number of times to form an Sr-O atomic layer on the uppermost layer.
An oxide superconductor thin film having the composition was manufactured. Comparative Example 2 In Example 2, shutters (a) to (d) were replaced with
The operation of opening each one for a predetermined time in the order of c, d, b, b, d, b, d, c, d, b, d, a, b is repeated a required number of times to form an Sr-O atomic layer on the uppermost layer. Other than that, a Bi-based (2212) composition oxide superconductor thin film was manufactured in the same manner as in Example 2. Comparative Example 3 In Example 3, the shutters (a) to (d) were replaced with (d) and (d).
Ha, ni, ha, ni, ro, i, i, ro, ni, ha, ni, ha,
The Tl system (2223) is formed in the same manner as in the third embodiment except that the operation of opening one by one in the order of d, b, b, b, and b is repeated a required number of times to form a Ba-O atomic layer on the uppermost layer.
An oxide superconductor thin film having the composition was manufactured.
【0015】比較例4 実施例4において、シャッター(イ)〜(ニ)を、ニ,
ハ,ニ,ロ,イ,イ,ロ,ニ,ハ,ニ,ロ,イ,イ,ロ
の順序で1個づつ所定時間開く操作を所要回数繰り返し
て最上層にBa−O原子層を形成した他は、実施例4と
同じ方法によりTl系(2212)組成の酸化物超電導
体薄膜を製造した。 比較例5 実施例5において、シャッター(イ)〜(ニ)を、ロ,
ハ,ロ,イ,ロ,イ,ロ,ハ,ロ,イ,ロ,イの順序で
1個づつ所定時間開く操作を所要回数繰り返して最上層
にBa−O原子層を形成した他は、実施例5と同じ方法
によりYBaCuO系酸化物超電導体薄膜を製造した。
このようにして得られた各々の酸化物超電導体薄膜に
ついて、Tcを4端子法により測定した。又液体窒素中
(77K)にて、10GHzのマイクロ波を照射した状
態で表面抵抗(Rs )を測定した。結果は表1に示し
た。尚、各々の薄膜について、X線回折法により結晶配
向性を調べたところ、いずれもC軸配向していた。Comparative Example 4 In Example 4, shutters (a) to (d) were replaced with
The operation of opening one by one in the order of c, d, b, d, i, b, d, c, d, b, b, b, b is repeated a required number of times to form a Ba-O atomic layer on the uppermost layer. Except that, a Tl-based (2212) composition oxide superconductor thin film was manufactured in the same manner as in Example 4. Comparative Example 5 In Example 5, the shutters (a) to (d) were replaced by
Except that the operation of opening one by one for a predetermined number of times in the order of c, b, b, b, b, b, b, b, b, b, b, b, b, b, b, b In the same manner as in Example 5, a YBaCuO-based oxide superconductor thin film was manufactured.
For each of the oxide superconductor thin films thus obtained, Tc was measured by a four-terminal method. Further, the surface resistance (Rs) was measured in a state where microwaves of 10 GHz were irradiated in liquid nitrogen (77 K). The results are shown in Table 1. In addition, when the crystal orientation of each thin film was examined by an X-ray diffraction method, all of the thin films were C-axis oriented.
【0016】[0016]
【表1】 [Table 1]
【0017】表1より明らかなように、本発明例品(No
1〜5)はTcが高く、又表面抵抗が小さく、ミリ波・
マイクロ波デバイス用として優れた特性のものであっ
た。これは酸化物超電導体薄膜の最上層に伝導性のCu
−O原子層が形成されている為である。これに対し、比
較例品(No6〜10)は、特に表面抵抗が大きい値のもの
となったが、これは酸化物超電導体薄膜の最上層に電気
を通し難いSr−O原子層又はBa−O原子層が形成さ
れている為である。As is clear from Table 1, the sample of the present invention (No.
1-5) have high Tc, low surface resistance, and
It had excellent characteristics for microwave devices. This is because the conductive Cu
This is because the -O atomic layer is formed. On the other hand, the comparative example (Nos. 6 to 10) had a particularly large surface resistance, but this was due to the Sr—O atomic layer or Ba— This is because an O atomic layer is formed.
【0018】[0018]
【効果】以上述べたように、本発明の酸化物超電導体薄
膜は、最上層に伝導性のCu−O原子層が形成されてい
るので表面抵抗が小さく、依ってミリ波・マイクロ波デ
バイス等の薄膜導体として用いて、顕著な効果を奏す
る。As described above, the oxide superconductor thin film of the present invention has a low surface resistance since the conductive Cu—O atomic layer is formed on the uppermost layer, and therefore has a low resistance in millimeter-wave / microwave devices. It has a remarkable effect when used as a thin film conductor.
【図面の簡単な説明】[Brief description of the drawings]
【図1】BiSrCaCuO系酸化物超電導体の結晶の
単位格子の説明図である。FIG. 1 is an explanatory diagram of a unit cell of a crystal of a BiSrCaCuO-based oxide superconductor.
【図2】TlBaCaCuO系酸化物超電導体の結晶の
単位格子の説明図である。FIG. 2 is an explanatory diagram of a unit cell of a crystal of a TlBaCaCuO-based oxide superconductor.
【図3】YBaCuO系酸化物超電導体の結晶の単位格
子の説明図である。FIG. 3 is an explanatory diagram of a unit cell of a crystal of a YBaCuO-based oxide superconductor.
【図4】本発明の酸化物超電導体薄膜を製造するのに用
いる分子線エピタキシー装置の要部説明図である。FIG. 4 is an explanatory view of a main part of a molecular beam epitaxy apparatus used for producing the oxide superconductor thin film of the present invention.
1 チャンバー 2 基板 3,13 ヒーター 4 水晶振動式膜厚計 a〜d セル (イ)〜(ニ) シャッター DESCRIPTION OF SYMBOLS 1 Chamber 2 Substrate 3, 13 Heater 4 Quartz-vibration-type film thickness meter a-d cell (a)-(d) Shutter
フロントページの続き (56)参考文献 特開 平1−130420(JP,A) 特開 平1−246371(JP,A) 特開 平1−268865(JP,A) 特開 平2−5581(JP,A) 特開 平2−239104(JP,A) 特開 平3−12323(JP,A) 特開 平2−306508(JP,A) 特開 平4−329878(JP,A) 国際公開90/13517(WO,A1) (58)調査した分野(Int.Cl.7,DB名) C30B 1/00 - 35/00 C01G 1/00 H01B 12/06 H01P 11/00 Continuation of front page (56) References JP-A-1-130420 (JP, A) JP-A-1-246371 (JP, A) JP-A-1-268865 (JP, A) JP-A-2-5581 (JP) JP-A-2-239104 (JP, A) JP-A-3-12323 (JP, A) JP-A-2-306508 (JP, A) JP-A-4-329878 (JP, A) International publication 90 / 13517 (WO, A1) (58) Fields investigated (Int. Cl. 7 , DB name) C30B 1/00-35/00 C01G 1/00 H01B 12/06 H01P 11/00
Claims (1)
して含有する酸化物超電導体薄膜であって、前記薄膜の
結晶のC軸が基板面の垂線方向に配向しており、且つ前
記薄膜の最上層に伝導性のCu−O原子層が形成されて
いることを特徴とする酸化物超電導体薄膜。1. An oxide superconductor thin film formed on a substrate and containing Cu as a constituent element, wherein a C axis of a crystal of the thin film is oriented in a direction perpendicular to a substrate surface, and the thin film A conductive Cu—O atomic layer is formed on the uppermost layer of the oxide superconductor thin film.
Priority Applications (1)
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JP3115350A JP3021764B2 (en) | 1991-04-18 | 1991-04-18 | Oxide superconductor thin film |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
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JP3115350A JP3021764B2 (en) | 1991-04-18 | 1991-04-18 | Oxide superconductor thin film |
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Publication Number | Publication Date |
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JP3021764B2 true JP3021764B2 (en) | 2000-03-15 |
Family
ID=14660350
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