JP3359826B2 - Electronic devices using superconducting oxide thin films - Google Patents
Electronic devices using superconducting oxide thin filmsInfo
- Publication number
- JP3359826B2 JP3359826B2 JP27212196A JP27212196A JP3359826B2 JP 3359826 B2 JP3359826 B2 JP 3359826B2 JP 27212196 A JP27212196 A JP 27212196A JP 27212196 A JP27212196 A JP 27212196A JP 3359826 B2 JP3359826 B2 JP 3359826B2
- Authority
- JP
- Japan
- Prior art keywords
- thin film
- superconducting oxide
- electronic device
- oxide superconductor
- layer
- 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
Landscapes
- Superconductor Devices And Manufacturing Methods Thereof (AREA)
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、高温酸化物超伝導
薄膜を用いた電界効果型の電子デバイスに関する。The present invention relates to a field-effect electronic device using a high-temperature oxide superconducting thin film.
【０００２】[0002]
【従来の技術】金属超伝導体薄膜に外部電界を印加する
ことにより、上記超伝導体薄膜中のキャリア濃度を変調
し、抵抗等の電気的特性を制御する電界効果型電子デバ
イスは従来から知られている。しかし、金属超伝導体
は、そのキャリア濃度が大きく、外部電界は急激に緩和
されてしまうため、超伝導特性の変調度は極めて小さ
い。また、外部電界による変調度を拡大するために、膜
厚の極めて薄い金属超伝導体薄膜を用いる構造が提案さ
れている。しかしながら、変調度が大きくなるほど膜厚
が薄くなると、薄膜が微粒子構造となってしまうため、
外部電界によって変調される電気的特性の変化分は大き
くなるものの、薄膜単体の特性が非超伝導性となってし
まうという問題がある。金属超伝導体に比してキャリア
濃度が小さいことが特徴であるビスマス鉛バリウム（Ｂ
ＰＢ）系の酸化物超伝導体を薄膜材料に用いた場合に
は、電気的特性の変調度が大きな電子デバイスが得られ
る。しかしながら、（ＢＰＢ）系の酸化物超伝導体は、
その超伝導転移臨界温度が１０Ｋ程度であるため、より
高温で動作する高温酸化物超伝導体薄膜を用いた電子デ
バイスの実現が期待されている。高温酸化物超伝導体
は、１９８６年にＩＢＭチュリッヒのベドノルツとミュ
ーラーが、ランタンとストロンチウムと銅を構成要素と
した酸化物が３０〜４０Ｋ程度で超伝導特性を示すこと
を発見して以来、イットリウム系（Ｔｃ〜９０Ｋ）、ビ
スマス系（Ｔｃ〜１１０Ｋ）などの高温酸化物超伝導体
が次々と発見された。これらの高温酸化物超伝導体の薄
膜化は勢力的に研究され、バルク材料とほとんど同程度
の臨界温度を示すエピタキシャル成長膜が得られるに到
っている。しかしながら、基板上に作製される酸化物薄
膜の膜厚が１０ｎｍ以下となると薄膜の超伝導特性が顕
著に劣化することが知られており、これまでの高温酸化
物超伝導体薄膜では、表面保護層や基板との界面にバッ
ファ層が必要であった。上記のような高温酸化物超伝導
体薄膜を用いて電界効果型電子デバイスを構成する場
合、バッファ層や表面保護層が存在すると、外部電界は
超伝導体薄膜の特性を変調すると共に、該バッファ層や
表面保護膜にも影響を及ぼすため、超伝導層のみを有効
に変調することを妨げるという問題があった。2. Description of the Related Art A field effect type electronic device which modulates a carrier concentration in a superconductor thin film by applying an external electric field to the metal superconductor thin film and controls electric characteristics such as resistance has been known. Have been. However, since the metal superconductor has a high carrier concentration and the external electric field is suddenly alleviated, the degree of modulation of the superconductivity is extremely small. In order to increase the degree of modulation by an external electric field, a structure using a metal superconductor thin film having a very small thickness has been proposed. However, as the degree of modulation increases and the film thickness decreases, the thin film has a fine particle structure.
Although the amount of change in the electrical characteristics modulated by the external electric field increases, there is a problem that the characteristics of the thin film itself become non-superconductive. Bismuth lead barium (B), which is characterized by a lower carrier concentration than metal superconductors
When a PB) -based oxide superconductor is used for a thin film material, an electronic device having a large degree of modulation of electrical characteristics can be obtained. However, (BPB) -based oxide superconductors are:
Since the superconducting transition critical temperature is about 10K, realization of an electronic device using a high-temperature oxide superconductor thin film operating at a higher temperature is expected. Since 1986, Bednorz and Mueller of the IBM Zurich have discovered that high-temperature oxide superconductors have been found to be yttrium since they discovered that oxides composed of lanthanum, strontium, and copper exhibited superconductivity at about 30-40K. High-temperature oxide superconductors such as those based on (Tc to 90K) and bismuth (Tc to 110K) have been discovered one after another. The thinning of these high-temperature oxide superconductors has been energetically studied, and an epitaxially grown film having a critical temperature almost equal to that of a bulk material has been obtained. However, it is known that when the thickness of an oxide thin film formed on a substrate is 10 nm or less, the superconductivity of the thin film is significantly deteriorated. A buffer layer was required at the interface between the layer and the substrate. When a field-effect electronic device is constructed using a high-temperature oxide superconductor thin film as described above, if a buffer layer or a surface protective layer is present, an external electric field modulates the characteristics of the superconductor thin film and the buffer layer. There is also a problem in that modulation of only the superconducting layer is effectively prevented because it also affects the layer and the surface protective film.
【０００３】[0003]
【発明が解決しようとする課題】本発明の目的は、上記
従来技術における問題点を解消し、表面保護層や基板と
の界面にバッファ層が存在しない高温酸化物超伝導体薄
膜を用いた、電界効果型の電子デバイスを提供すること
にある。SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in the prior art and to use a high-temperature oxide superconductor thin film having no buffer layer at the interface with a surface protective layer or a substrate. An object of the present invention is to provide a field-effect electronic device.
【０００４】[0004]
【課題を解決するための手段】上記本発明の目的を達成
するために、本発明は特許請求の範囲に記載のような構
成とするものである。すなわち、本発明は請求項１に記
載のように、高温酸化物超伝導体薄膜と導電性薄膜とが
誘電体層を挾んでコンデンサ構造を形成し、上記超伝導
酸化物薄膜と導電性薄膜との間に電圧を印加して、上記
超伝導酸化物薄膜中のキャリア濃度を変化させることに
より、上記超伝導酸化物薄膜の電気的特性を有効に変調
させる電界効果型の電子デバイスであって、上記超伝導
酸化物薄膜は、ＬａＳｒＡｌＯ4基板上に形成されたＬ
ａ2-xＳｒxＣｕＯ4+d（式中、ｘは０〜２以下、ｄは−
１〜＋１の範囲を表わす。）よりなる組成の極薄い薄膜
からなり、かつ、該薄膜の界面にはバッファ層が存在し
ない高温酸化物超伝導体薄膜を用いた電子デバイスとす
るものである。また、本発明は請求項２に記載のよう
に、請求項１において、Ｌａ2-xＳｒxＣｕＯ4+dよりな
る組成の極薄い薄膜の膜厚は、０.６６ｎｍ以上、５.３
ｎｍ以下の範囲の超伝導酸化物薄膜を用いた電子デバイ
スとするものである。このように、上記請求項１または
請求項２に記載の超伝導酸化物薄膜を用いた電子デバイ
スとすることにより、超伝導酸化物薄膜の電気的特性の
変調度が大きい電界効果型３端子素子を実現できる効果
がある。本発明者らは、ＬａＳｒＡｌＯ4基板上にＬａ
2-xＳｒxＣｕＯ4+d（式中、ｘは０〜２以下、ｄは−１
〜＋１の範囲を表わす。）高温酸化物超伝導体薄膜を作
製した場合に、膜厚が０.６６ｎｍ（例えば、高温酸化
物超伝導体の分子径）以上、５.３ｎｍ（例えば、高温
酸化物超伝導体の分子径の８倍）以下の範囲であっても
バッファ層や表面保護層を設ける必要がなく、上記Ｌａ
2-xＳｒxＣｕＯ4+d高温酸化物超伝導体薄膜が超伝導特
性を示すことを見出した。したがって、本発明の高温酸
化物超伝導体薄膜に外部電界を印加することにより、上
記超伝導体薄膜の特性を変調する電界効果型の電子デバ
イスにおいて、ＬａＳｒＡｌＯ4基板上に作製した膜厚
が０.６６〜５.３ｎｍの範囲のＬａ2-xＳｒxＣｕＯ4+d
高温酸化物超伝導体薄膜を用いることを最も主要な特徴
とするものであり、従来技術と異なるところは、基板材
料と超伝導層の材料選択によって、バッファ層や表面保
護層を設ける必要のない高温酸化物超伝導体薄膜を用い
ること、および高温酸化物超伝導体薄膜の厚さが極めて
薄い点にある。本発明のＬａＳｒＡｌＯ4基板上に形成
するＬａ2-xＳｒxＣｕＯ4+d高温酸化物超伝導体薄膜の
膜厚は、０.６６ｎｍ以下では、該酸化物超伝導体の分
子径よりも小さくなるのでＬａ2-xＳｒxＣｕＯ4+d組成
の酸化物超伝導体が形成できなくなり、また膜厚が５.
３ｎｍを超えると、該酸化物超伝導体薄膜の電気的特性
の変調度合が実用上有効な値を示さなくなるので好まし
くない。Means for Solving the Problems In order to achieve the object of the present invention, the present invention is configured as described in the claims. That is, according to the present invention, a high-temperature oxide superconductor thin film and a conductive thin film form a capacitor structure with a dielectric layer interposed therebetween, and the superconducting oxide thin film and the conductive thin film are combined with each other. A voltage is applied between the superconducting oxide thin film to change the carrier concentration, thereby effectively modulating the electrical characteristics of the superconducting oxide thin film field effect type electronic device, The superconducting oxide thin film is formed on a LaSrAlO 4 substrate.
a 2-x Sr x CuO 4 + d (where x is 0 to 2 or less, and d is −
Represents the range of 1 to +1. ) Is an electronic device using a high-temperature oxide superconductor thin film composed of an extremely thin thin film having no buffer layer at the interface of the thin film. Further, according to the present invention as described in claim 2, in claim 1, the extremely thin film having a composition of La 2−x Sr x CuO 4 + d has a thickness of 0.66 nm or more and 5.3 or less.
An electronic device using a superconducting oxide thin film in a range of nm or less. As described above, the electronic device using the superconducting oxide thin film according to claim 1 or 2 provides a field-effect type three-terminal element having a large degree of modulation of the electrical characteristics of the superconducting oxide thin film. There is an effect that can be realized. The present inventors have proposed that LaSrAlO 4 substrate
2-x Sr x CuO 4 + d (where x is 0 to 2 or less and d is −1
Represents a range from to +1. ) When a high-temperature oxide superconductor thin film is prepared, the film thickness is 0.66 nm (for example, the molecular diameter of the high-temperature oxide superconductor) or more and 5.3 nm (for example, the molecular diameter of the high-temperature oxide superconductor). It is not necessary to provide a buffer layer or a surface protective layer even in the range of 8 times or less, and the above La
It has been found that a 2-x Sr x CuO 4 + d high temperature oxide superconductor thin film exhibits superconducting properties. Therefore, in a field-effect electronic device that modulates the characteristics of the superconductor thin film by applying an external electric field to the high-temperature oxide superconductor thin film of the present invention, the film thickness formed on the LaSrAlO 4 substrate is zero. La 2-x Sr x CuO 4 + d in the range of .66-5.3 nm
The main feature of using a high-temperature oxide superconductor thin film is that, unlike the conventional technology, there is no need to provide a buffer layer or surface protection layer by selecting the material of the substrate and the superconducting layer. The point is that a high-temperature oxide superconductor thin film is used, and the thickness of the high-temperature oxide superconductor thin film is extremely thin. La 2-x Sr x CuO 4 + d high temperature oxide superconductor film thickness of the thin film to be formed LaSrAlO 4 on the substrate of the present invention, the following in 0.66 nm, less than the molecular diameter of the oxide superconductor Therefore, an oxide superconductor having a composition of La 2-x Sr x CuO 4 + d cannot be formed, and the film thickness is 5.
If it exceeds 3 nm, the degree of modulation of the electrical characteristics of the oxide superconductor thin film does not show a practically effective value, which is not preferable.
【０００５】[0005]
【発明の実施の形態】図１は、本発明の実施の形態の一
例を示す模式図であって、符号１は高温酸化物超伝導体
層、２は誘電体層、３は基板、４は金属電極層を示す。
５、６は高温酸化物超伝導体層１に取り付けた電極を示
す。高温酸化物超伝導体層１にはバッファ層や表面保護
膜を持たない、厚さが５.３ｎｍ未満のＬａ2-xＳｒxＣ
ｕＯ4+d（００１）薄膜が、基板３にはＬａＳｒＡｌＯ4
よりなる基板、また、誘電体層２にはＬａＳｒＡｌＯ4
／ＳｒＴｉＯ3またはＬａＳｒＡｌＯ4／ＢａＴｉＯ3の
誘電体積層膜などが用いられる。図に示す電子デバイス
では、高温酸化物超伝導体層１、誘電体層２、金属電極
層４の３層が重なってコンデンサを形成している電界効
果型の電子デバイスである。金属電極層４と高温酸化物
超伝導体層１との間に、外部電圧源７を印加すると、高
温酸化物超伝導体層１には外部電界が発生するため、キ
ャリア数が変調される。これにより、高温酸化物超伝導
体層１の超伝導転移温度などの特性は大きく変化する。
したがって、このような電子デバイスでは、外部電圧源
７によって、高温酸化物超伝導体層１に取り付けた電極
５、６間の抵抗を大きく変化させることができる効果が
ある。DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view showing an example of an embodiment of the present invention, wherein reference numeral 1 denotes a high-temperature oxide superconductor layer, 2 denotes a dielectric layer, 3 denotes a substrate, and 4 denotes a substrate. 3 shows a metal electrode layer.
Reference numerals 5 and 6 denote electrodes attached to the high-temperature oxide superconductor layer 1. The high temperature oxide superconductor layer 1 no buffer layer and a surface protective film, the thickness is less than 5.3nm La 2-x Sr x C
A uO 4 + d (001) thin film is formed on the substrate 3 by LaSrAlO 4
The substrate made of LaSrAlO 4
For example, a dielectric laminated film of / SrTiO 3 or LaSrAlO 4 / BaTiO 3 is used. The electronic device shown in the figure is a field-effect electronic device in which a high-temperature oxide superconductor layer 1, a dielectric layer 2, and a metal electrode layer 4 are stacked to form a capacitor. When an external voltage source 7 is applied between the metal electrode layer 4 and the high-temperature oxide superconductor layer 1, an external electric field is generated in the high-temperature oxide superconductor layer 1, so that the number of carriers is modulated. As a result, characteristics such as the superconducting transition temperature of the high-temperature oxide superconductor layer 1 change significantly.
Therefore, in such an electronic device, there is an effect that the resistance between the electrodes 5 and 6 attached to the high-temperature oxide superconductor layer 1 can be largely changed by the external voltage source 7.
【０００６】[0006]
【発明の効果】本発明の超伝導酸化物薄膜を用いた電子
デバイスは、高温酸化物超伝導体薄膜を用いて、変調度
が大きい電界効果型３端子素子を実現できる効果があ
る。The electronic device using the superconducting oxide thin film of the present invention has an effect of realizing a field-effect type three-terminal device having a large degree of modulation using the high-temperature oxide superconductor thin film.
【図１】本発明の実施の形態で例示した電界効果型の電
子デバイスの構成を示す模式図。FIG. 1 is a schematic view illustrating a configuration of a field-effect electronic device exemplified in an embodiment of the present invention.
１…高温酸化物超伝導体層 ２…誘電体層 ３…基板 ４…金属電極層 ５…高温酸化物超伝導体層に取り付けた電極 ６…高温酸化物超伝導体層に取り付けた電極 ７…外部電圧源 DESCRIPTION OF SYMBOLS 1 ... High temperature oxide superconductor layer 2 ... Dielectric layer 3 ... Substrate 4 ... Metal electrode layer 5 ... Electrode attached to high temperature oxide superconductor layer 6 ... Electrode attached to high temperature oxide superconductor layer 7 ... External voltage source
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 平５−218515（ＪＰ，Ａ) 特開 平５−254992（ＪＰ，Ａ) 特開 平６−268265（ＪＰ，Ａ) 特開 平２−194661（ＪＰ，Ａ) (58)調査した分野(Int.Cl.7，ＤＢ名) H01L 39/00 - 39/22 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-218515 (JP, A) JP-A-5-254992 (JP, A) JP-A-6-268265 (JP, A) JP-A-2- 194661 (JP, A) (58) Field surveyed (Int. Cl. 7 , DB name) H01L 39/00-39/22
Claims (2)
誘電体層を挾んでコンデンサ構造を形成し、上記超伝導
酸化物薄膜と導電性薄膜との間に電圧を印加して、上記
超伝導酸化物薄膜中のキャリア濃度を変化させることに
より、上記超伝導酸化物薄膜の電気的特性を有効に変調
させる電界効果型の電子デバイスであって、 上記超伝導酸化物薄膜は、ＬａＳｒＡｌＯ4基板上に形
成された Ｌａ2-xＳｒxＣｕＯ4+d（式中、ｘは０〜２以下、ｄは
−１〜＋１の範囲を表わす。）よりなる組成の極薄い薄
膜からなり、かつ、該薄膜の界面にバッファ層が存在し
ない高温酸化物超伝導体薄膜であることを特徴とする超
伝導酸化物薄膜を用いた電子デバイス。1. A capacitor structure comprising a high-temperature oxide superconductor thin film and a conductive thin film sandwiching a dielectric layer, and applying a voltage between the superconducting oxide thin film and the conductive thin film, An electric field effect type electronic device that effectively modulates the electrical characteristics of the superconducting oxide thin film by changing a carrier concentration in the superconducting oxide thin film, wherein the superconducting oxide thin film is LaSrAlO (wherein, x is 0-2 below, d represents. a range of -1~ + 1) 4 La formed on the substrate 2-x Sr x CuO 4 + d made from very thin film having a composition consisting of, An electronic device using a superconducting oxide thin film, which is a high-temperature oxide superconductor thin film having no buffer layer at the interface of the thin film.
4+dよりなる組成の極薄い薄膜の膜厚は、０.６６ｎｍ以
上、５.３ｎｍ以下の範囲であることを特徴とする超伝
導酸化物薄膜を用いた電子デバイス。2. The method according to claim 1, wherein La 2-x Sr x CuO is used.
An electronic device using a superconducting oxide thin film, wherein an extremely thin film having a composition of 4 + d has a thickness of 0.66 nm or more and 5.3 nm or less.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP27212196A JP3359826B2 (en) | 1996-10-15 | 1996-10-15 | Electronic devices using superconducting oxide thin films |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP27212196A JP3359826B2 (en) | 1996-10-15 | 1996-10-15 | Electronic devices using superconducting oxide thin films |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH10117022A JPH10117022A (en) | 1998-05-06 |
| JP3359826B2 true JP3359826B2 (en) | 2002-12-24 |
Family
ID=17509389
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP27212196A Expired - Fee Related JP3359826B2 (en) | 1996-10-15 | 1996-10-15 | Electronic devices using superconducting oxide thin films |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3359826B2 (en) |
-
1996
- 1996-10-15 JP JP27212196A patent/JP3359826B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH10117022A (en) | 1998-05-06 |
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