JP2001302400A - Oxide superlatice - Google Patents
Oxide superlaticeInfo
- Publication number
- JP2001302400A JP2001302400A JP2000077006A JP2000077006A JP2001302400A JP 2001302400 A JP2001302400 A JP 2001302400A JP 2000077006 A JP2000077006 A JP 2000077006A JP 2000077006 A JP2000077006 A JP 2000077006A JP 2001302400 A JP2001302400 A JP 2001302400A
- Authority
- JP
- Japan
- Prior art keywords
- oxide
- superlattice
- thin film
- thin films
- oriented
- 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
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、酸化物超格子に関
し、特に、少なくとも２種類のペロブスカイト型酸化物
薄膜を繰り返し積層して超格子構造とした酸化物超格子
に関する。The present invention relates to an oxide superlattice, and more particularly to an oxide superlattice having a superlattice structure formed by repeatedly laminating at least two kinds of perovskite oxide thin films.
【０００２】[0002]
【従来の技術】従来より、ペロブスカイト型酸化物セラ
ミックスを薄膜化しつつ、その物性を改善することによ
り、酸化物セラミックスの薄膜をデバイスとして利用す
ることが期待されている。このような酸化物薄膜の物性
の１つとして、比誘電率をあげることができる。2. Description of the Related Art Conventionally, it has been expected that a thin film of an oxide ceramic is used as a device by improving the physical properties of the perovskite-type oxide ceramic while reducing the thickness thereof. One of the physical properties of such an oxide thin film is its relative dielectric constant.
【０００３】酸化物薄膜の特性を改善する方法として
は、その単層膜を固溶体化させる方法が試みられている
が、一般に、固溶体化により得られる特性は、同等の組
成のバルク結晶を超えるものではない。比誘電率につい
ても、酸化物薄膜の膜厚を薄くするほど比誘電率の値が
低下してゆき、バルク特性に比べてかなり小さな比誘電
率の値しか得ることができない。例えば、H.Tabata et
al. Appl. Phy. Lett. 65,1970(1994)では、（Ｂａ，Ｓ
ｒ）ＴｉＯ３固溶体薄膜の比誘電率に関して、膜厚の減
少にともなって比誘電率が低下することが報告されてい
る。（図６参照）[0003] As a method of improving the characteristics of an oxide thin film, a method of forming a single-layer film into a solid solution has been attempted. However, in general, the characteristics obtained by the solid solution exceed those of a bulk crystal having an equivalent composition. is not. As for the relative dielectric constant, the value of the relative dielectric constant decreases as the thickness of the oxide thin film decreases, and only a value of the relative dielectric constant which is considerably smaller than the bulk characteristics can be obtained. For example, H. Tabata et
al. Appl. Phy. Lett. 65 , 1970 (1994) states that (Ba, S
r) Regarding the relative dielectric constant of the TiO 3 solid solution thin film, it has been reported that the relative dielectric constant decreases as the film thickness decreases. (See Fig. 6)
【０００４】一方、酸化物薄膜の特性を高機能化するテ
クニックとして、超格子が挙げられる。超格子とは、少
なくとも２種以上の異なる材料からなるエピタキシャル
薄膜又は単結晶薄膜を分子層レベル又は原子層単位で交
互に、あるいは繰り返し積層した薄膜である。このよう
な超格子構造を有する酸化物薄膜（酸化物超格子）によ
れば、固溶体を薄膜化しただけではバルク特性を十分に
再現できないような材料系おいても、優れた特性を発現
することができる。On the other hand, a superlattice is a technique for improving the properties of an oxide thin film. The superlattice is a thin film in which epitaxial thin films or single crystal thin films made of at least two or more different materials are alternately or repeatedly laminated at a molecular layer level or an atomic layer unit. According to the oxide thin film having such a superlattice structure (oxide superlattice), excellent properties can be exhibited even in a material system in which the bulk properties cannot be sufficiently reproduced only by reducing the thickness of the solid solution. Can be.
【０００５】超格子はさまざまな材料に適用でき、特に
磁性体で応用例が多いが、最近では誘電体酸化物材料を
超格子化する例もしばしば見られる。例えば、特開平７
−８２０９７号公報に開示された超格子では、２種のペ
ロブスカイト型誘電体材料を積層し、１層当たりの膜厚
を単分子層まで薄層化することで、優れた誘電特性を発
現させている。２種の誘電体材料には、似通った結晶構
造を持つが僅かに格子定数が異なる誘電材料（ＢａＴｉ
Ｏ３、ＳｒＴｉＯ３）が選ばれている。この酸化物超格
子では、わずかな格子不整合が積層界面に強い応力を及
ぼすことを利用して酸化物薄膜に格子歪みを導入してい
る。ＢａＴｉＯ３（チタン酸バリウム）薄膜とＳｒＴｉ
Ｏ３（チタン酸ストロンチウム）薄膜との界面では、Ｂ
ａＴｉＯ ３薄膜の格子が縮み、ＳｒＴｉＯ３薄膜の格子
が伸びることによって格子不整合が緩和されている。こ
れは「歪超格子」と呼ばれ、比誘電率の上昇などが実現
されている。[0005] Superlattices can be applied to various materials, especially
There are many applications in magnetic materials, but recently, dielectric oxide materials
Examples of superlattices are also often seen. For example, JP-A-7
In the superlattice disclosed in US Pat.
Lamination of lobskite type dielectric materials, film thickness per layer
Has excellent dielectric properties by reducing the thickness of
It is revealed. The two dielectric materials have similar crystal structures
Dielectric material (BaTi
O3, SrTiO3) Is selected. This oxide super
In the device, slight lattice mismatch causes strong stress on the lamination interface.
Lattice strain is introduced into the oxide thin film
You. BaTiO3(Barium titanate) thin film and SrTi
O3At the interface with the (strontium titanate) thin film, B
aTiO 3The lattice of the thin film shrinks and SrTiO3Thin film lattice
The lattice mismatch is mitigated by the extension of This
This is called a “strained superlattice,” and realizes an increase in relative permittivity
Have been.
【０００６】[0006]
【発明が解決しようとする課題】こうして２種以上の酸
化物薄膜を超格子構造とすることにより、酸化物薄膜の
固溶体化では実現できないような比誘電率が得られてい
る。しかし、従来の酸化物超格子では、図１に示すよう
に、基板１の上にエピタキシャル成長させられたＢａＴ
ｉＯ３薄膜２とＳｒＴｉＯ３薄膜３はいずれも（００
１）面に配向していてその分極軸の方向（［００１］方
向）は両酸化物薄膜２、３の配向膜と垂直な方向（結晶
成長方向）を向いている。従って（００１）配向の超格
子は強い強誘電性を有することになる。この場合、超格
子膜は残留分極（膜に印加する電界がゼロの時にも分極
が存在する）を有し、高周波領域において比誘電率が低
下するといった誘電緩和の原因となる。例えば Z. Wang
et al. ECS Vol. 99-2, 1054(1999)では（００１）配
向のＳｒＴｉＯ３／ＢａＴｉＯ３超格子が作製されてお
り、比誘電率４２７と高い値を得ているが、一方で残留
分極も２Ｐｒ≒１２μＣ／ｃｍ２と強い強誘電性を示し
ている。このような強誘電性は高周波デバイス応用への
障害となり得る。By thus forming a superlattice structure of two or more kinds of oxide thin films, a relative dielectric constant which cannot be realized by forming a solid solution of the oxide thin films is obtained. However, in the conventional oxide superlattice, as shown in FIG.
Both the iO 3 thin film 2 and the SrTiO 3 thin film 3 are (00
1) The surface is oriented, and the direction of the polarization axis ([001] direction) is perpendicular to the orientation films of both oxide thin films 2 and 3 (crystal growth direction). Therefore, the (001) -oriented superlattice has strong ferroelectricity. In this case, the superlattice film has remanent polarization (polarization exists even when the electric field applied to the film is zero), which causes dielectric relaxation such as a decrease in relative dielectric constant in a high-frequency region. For example, Z. Wang
In et al. ECS Vol. 99-2, 1054 (1999), a (001) -oriented SrTiO 3 / BaTiO 3 superlattice has been fabricated and has a high relative dielectric constant of 427, but has a remanent polarization. Also shows strong ferroelectricity of 2Pr ≒ 12 μC / cm 2 . Such ferroelectricity can be an obstacle to high frequency device applications.
【０００７】本発明は、上記の従来例の問題点に鑑みて
なされたものであり、その目的とするところは、少なく
とも２種類以上の酸化物薄膜を繰り返し積層することに
よって構成された酸化物超格子において、高い比誘電率
を実現し、かつ強誘電性を出来る限り抑制させることに
ある。The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object the purpose of the present invention is to provide an oxide superconductor formed by repeatedly laminating at least two or more oxide thin films. It is an object of the present invention to realize a high relative dielectric constant and suppress ferroelectricity as much as possible in a lattice.
【０００８】[0008]
【発明の開示】本発明にかかる酸化物超格子は、基板上
に、化学式ＡＢＯ３（ただし、ＡはＣａ、Ｓｒ、Ｂａ、
Ｐｂ、Ｌａからなる群より選択された少なくとも１種の
元素；ＢはＴｉ、Ｚｒ、Ｎｂ、Ｔａからなる群より選択
された少なくとも１種の元素）で表される少なくとも２
種類のペロブスカイト型酸化物薄膜が積層された酸化物
超格子において、前記酸化物薄膜が、それぞれの分極軸
と異なる方位に配向したものである。例えば、前記ペロ
ブスカイト型酸化物薄膜としてＢａＴｉＯ３薄膜とＳｒ
ＴｉＯ３薄膜を選択し、両薄膜を基板の表面に交互に積
み重ねることによって酸化物超格子が構成される。ま
た、これらの酸化物薄膜は、上記各群の元素の複合酸化
物からなる薄膜であってもよい。DISCLOSURE OF THE INVENTION The oxide superlattice according to the present invention is prepared by forming on a substrate the chemical formula ABO 3 (where A is Ca, Sr, Ba,
At least one element selected from the group consisting of Pb and La; B is at least one element selected from the group consisting of Ti, Zr, Nb, and Ta)
In an oxide superlattice in which various kinds of perovskite oxide thin films are stacked, the oxide thin films are oriented in directions different from the respective polarization axes. For example, as the perovskite oxide thin film, a BaTiO 3 thin film and Sr
An oxide superlattice is formed by selecting a TiO 3 thin film and alternately stacking both thin films on the surface of the substrate. Further, these oxide thin films may be thin films made of composite oxides of the above-mentioned elements.
【０００９】また、ペロブスカイト型酸化物薄膜は、一
般に［００１］方向が分極軸方向となっているから、配
向面が（００１）面から傾いていればよいが、特にいず
れの酸化物薄膜も（１１１）面配向、または（１１０）
面配向となるようにすれば、目的とする面方位のエピタ
キシャル薄膜又は単結晶薄膜を容易に製作することがで
きる。The perovskite-type oxide thin film generally has a [001] direction as the polarization axis direction. Therefore, the orientation plane may be inclined from the (001) plane. (111) plane orientation, or (110)
By making the plane orientation, an epitaxial thin film or a single crystal thin film having a desired plane orientation can be easily manufactured.
【００１０】なお、本明細書において、面方位や配向方
向を言うときは、等価な方向を含むものとする。例え
ば、（００１）面と言うときは、（０１０）面や（１０
０）面、（００−１）面、（０−１０）面、（−１０
０）面も含み、［１１０］方向と言うときは、［１０
１］方向や［０１１］方向、［−１−１０］方向、［１
−１０］方向、［−１１０］方向なども含むものとす
る。[0010] In this specification, the terms "plane orientation" and "orientation direction" include equivalent directions. For example, when referring to the (001) plane, the (010) plane or (10)
0) plane, (00-1) plane, (0-10) plane, (-10) plane
0) plane, and when referring to the [110] direction,
1] direction, [011] direction, [-1-10] direction, [1
It also includes a [-10] direction, a [-110] direction, and the like.
【００１１】このような酸化物超格子によれば、大きな
値の比誘電率と低い残留分極の両方を満足する特性が得
られることがわかった。すなわち、従来の酸化物超格子
にあっては、分極軸の方向が各酸化物薄膜の成長方向
（基板法線方向）を向いていたが、この分極軸を各酸化
物薄膜の成長方向から傾けることにより残留分極を抑制
できることが分かった。According to such an oxide superlattice, it has been found that characteristics satisfying both a large relative permittivity and a low remanent polarization can be obtained. That is, in the conventional oxide superlattice, the direction of the polarization axis is oriented in the growth direction (normal direction of the substrate) of each oxide thin film, but this polarization axis is inclined from the growth direction of each oxide thin film. Thus, it was found that remanent polarization could be suppressed.
【００１２】よって、極めて薄い薄膜からなるキャパシ
タ等の製作が可能となり、特にＩＣ等の素子表面に直接
実装するための薄膜キャパシタとして用いることも可能
となる。Accordingly, it is possible to manufacture a capacitor or the like made of an extremely thin thin film, and in particular, it is possible to use the capacitor as a thin film capacitor directly mounted on an element surface such as an IC.
【００１３】また、酸化物薄膜を形成するための基板
は、酸化物単結晶の基板が好ましく、より具体的には、
ＳｒＴｉＯ３、ＢａＴｉＯ３、ＬｉＮｂＯ３、ＬｉＴａ
Ｏ３、ＭｇＯ、ＬａＡｌＯ３、Ａｌ２Ｏ３、ＳｉＯ２、
（ＬａＡｌＯ３）（Ｓｒ２ＡｌＴａＯ６）のいずれか１
つによって形成されていることが望ましい。これらの単
結晶基板を用いることにより、ペロブスカイト型酸化物
薄膜を整合性よく成長させることができる。特に、Ｌｉ
ＴａＯ３などを基板として用いれば、弾性表面波素子に
酸化物超格子を組み込むことも可能になる。The substrate for forming the oxide thin film is preferably an oxide single crystal substrate. More specifically,
SrTiO 3 , BaTiO 3 , LiNbO 3 , LiTa
O 3 , MgO, LaAlO 3 , Al 2 O 3 , SiO 2 ,
Any one of (LaAlO 3 ) (Sr 2 AlTaO 6 )
It is desirable that they are formed by one. By using these single crystal substrates, a perovskite oxide thin film can be grown with good consistency. In particular, Li
If TaO 3 or the like is used as the substrate, it becomes possible to incorporate an oxide superlattice into the surface acoustic wave device.
【００１４】もっとも、基板としてはＳｉ単結晶基板な
ども用いることができ、Ｓｉ単結晶基板などを用いれ
ば、トランジスタやＩＣに酸化物超格子からなる特性の
良好なＭＩＭキャパシタを組み込むことも可能になる。
さらに、酸化物薄膜は、酸化物単結晶基板やＳｉ単結晶
基板の表面に直接に形成する必要はなく、一般的な基板
の表面に金属薄膜を形成した上に形成してもよい。However, a Si single crystal substrate or the like can also be used as the substrate. If a Si single crystal substrate or the like is used, it is possible to incorporate a MIM capacitor having excellent characteristics composed of an oxide superlattice into a transistor or an IC. Become.
Further, the oxide thin film does not need to be formed directly on the surface of an oxide single crystal substrate or a Si single crystal substrate, but may be formed after forming a metal thin film on the surface of a general substrate.
【００１５】[0015]
【発明の実施の形態】以下、本発明の実施形態として、
面方位（１１１）のＳｒＴｉＯ３単結晶基板に（１１
１）面配向のＢａＴｉＯ３薄膜と（１１１）面配向のＳ
ｒＴｉＯ３薄膜とを交互に積層して酸化物超格子を作製
する場合について説明する。DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described.
(11) A (111) SrTiO 3 single crystal substrate
1) Plane-oriented BaTiO 3 thin film and (111) -plane oriented S
A case in which an oxide superlattice is manufactured by alternately stacking rTiO 3 thin films will be described.
【００１６】まず、面方位（１１１）のＳｒＴｉＯ３単
結晶基板を用意した。この単結晶基板を真空槽内に入
れ、ターゲットにＢａＴｉＯ３の焼結体とＳｒＴｉＯ３
の焼結体を用い、真空中で６００℃以上の高温に保持し
て酸化雰囲気中においてレーザーアブレーション法で成
膜を行った。すなわち、ターゲットにレーザー光を照射
して基板結晶面上に原子層単位で酸化物薄膜をエピタキ
シャル成長させると共にＢａＴｉＯ３のターゲットとＳ
ｒＴｉＯ３のターゲットとを交互に切り替えることによ
り、基板の上に（１１１）面配向したＢａＴｉＯ３薄膜
と（１１１）面配向したＳｒＴｉＯ３薄膜とを交互にエ
ピタキシャル成長させ、全体の膜厚（合計膜厚）が１０
０ｎｍの酸化物超格子を得た。First, an SrTiO 3 single crystal substrate having a plane orientation (111) was prepared. This single crystal substrate was placed in a vacuum chamber, and a sintered body of BaTiO 3 and SrTiO 3 were used as targets.
Using a sintered body of the above, a film was formed by a laser ablation method in an oxidizing atmosphere while maintaining the temperature at 600 ° C. or higher in a vacuum. That is, the target is irradiated with laser light to epitaxially grow an oxide thin film on the crystal plane of the substrate in atomic layer units, and a target of BaTiO 3 and S
By alternately switching the target of rTiO 3 , a BaTiO 3 thin film with a (111) plane orientation and a SrTiO 3 thin film with a (111) plane orientation are alternately epitaxially grown on a substrate, and the overall film thickness (total film thickness) ) Is 10
An oxide superlattice of 0 nm was obtained.
【００１７】この後、ＸＲＤ（Ｘ線回折）およびＲＨＥ
ＥＤ（反射高速電子線回折）を用いて両酸化物薄膜を検
査した結果、ＢａＴｉＯ３薄膜もＳｒＴｉＯ３薄膜も基
板の表面と同じように（１１１）面内に面内配向した３
軸配向膜となっていることを確認することができた。従
って、このようにして作製された酸化物超格子では、図
２に示すように、基板１１の上にエピタキシャル成長さ
せられたＢａＴｉＯ３薄膜１２の分極軸方向［００１］
は、両酸化物薄膜１２、１３の配向方向［１１１］から
傾いている。Thereafter, XRD (X-ray diffraction) and RHE
As a result of inspecting both oxide thin films using ED (reflection high-energy electron diffraction), both the BaTiO 3 thin film and the SrTiO 3 thin film were in-plane oriented in the (111) plane in the same manner as the substrate surface.
It could be confirmed that the film was an axis alignment film. Accordingly, in the oxide superlattice thus manufactured, as shown in FIG. 2, the polarization axis direction [001] of the BaTiO 3 thin film 12 epitaxially grown on the substrate 11 is obtained.
Are inclined from the orientation direction [111] of both oxide thin films 12 and 13.
【００１８】さらに、酸化物超格子の合計膜厚を１００
ｎｍに保ったままで、ＢａＴｉＯ３薄膜とＳｒＴｉＯ３
のそれぞれ１層あたりの膜厚（以下、層厚という）を２
６ｎｍ、１０ｎｍ、４ｎｍ、２ｎｍ、０.４ｎｍと順次
変化させて酸化物超格子のサンプルを作製し、それぞれ
の誘電特性を調べた。この結果を図４に示す。図４の横
軸は両酸化物薄膜の層厚を示し、縦軸は酸化物超格子の
比誘電率を表している。図４によれば、両酸化物薄膜の
層厚が薄くなるほど比誘電率が増加し、０.４ｎｍの層
厚を有するサンプルでは比誘電率が約６００という非常
に高い値を示した。また、このときのサンプル中で最も
層厚が厚い、層厚２６ｎｍのサンプルにおいても比誘電
率は約２８０という値を示した。Further, the total thickness of the oxide superlattice is set to 100
nm while keeping the BaTiO 3 thin film and SrTiO 3
Of each layer (hereinafter, referred to as layer thickness) is 2
Oxide superlattice samples were prepared by sequentially changing them to 6 nm, 10 nm, 4 nm, 2 nm, and 0.4 nm, and their dielectric properties were examined. The result is shown in FIG. The horizontal axis in FIG. 4 indicates the layer thickness of both oxide thin films, and the vertical axis indicates the relative permittivity of the oxide superlattice. According to FIG. 4, the relative dielectric constant increases as the thickness of both oxide thin films is reduced, and the sample having a layer thickness of 0.4 nm has a very high relative dielectric constant of about 600. In addition, the relative dielectric constant of the sample having the thickest layer of 26 nm in the sample at this time also showed a value of about 280.
【００１９】また、図５に示すものは、ＢａＴｉＯ３薄
膜とＳｒＴｉＯ３薄膜とを交互にエピタキシャル成長さ
せた本発明の酸化物超格子における、印加電圧と分極と
の関係を示すものである。ＢａＴｉＯ３の単層膜は、残
留分極がＰｒ＝２０μＣ／ｃｍ２程度を示すのに対し、
図５からも分かるように、本発明の酸化物超格子によれ
ば、残留分極Ｐｒを１μＣ／ｃｍ２以下に抑えることが
できる。又、図５から分かるように分極のヒステリシス
も非常に小さくなっている。FIG. 5 shows the relationship between applied voltage and polarization in the oxide superlattice of the present invention in which BaTiO 3 thin films and SrTiO 3 thin films are alternately epitaxially grown. The monolayer film of BaTiO 3 has a remanent polarization of about Pr = 20 μC / cm 2 ,
As can be seen from FIG. 5, according to the oxide superlattice of the present invention, the remanent polarization Pr can be suppressed to 1 μC / cm 2 or less. Also, as can be seen from FIG. 5, the hysteresis of polarization is very small.
【００２０】従来の酸化物超格子では、結晶成長方向を
分極軸方向と一致させ、結晶格子のテトラゴナリティー
（＝ｃ軸長／ａ軸長）を増長させることで高い分極能を
得るという着想が多く見受けられた。しかし、このよう
にして作製された酸化物超格子の多くは強誘電性を持つ
ため、分極軸方向へ配向した酸化物超格子は、高い比誘
電率のみならず高い残留分極を有することになる。In the conventional oxide superlattice, the idea is to obtain a high polarization ability by making the crystal growth direction coincide with the direction of the polarization axis and increasing the tetragonality (= c-axis length / a-axis length) of the crystal lattice. Was seen a lot. However, since many of the oxide superlattices manufactured in this way have ferroelectricity, the oxide superlattice oriented in the polarization axis direction has not only a high relative dielectric constant but also a high remanent polarization. .
【００２１】しかし、強誘電体の残留分極は強い方位依
存性を持ち、分極軸方向では高く、分極軸と異なる方向
では低くなる傾向にある。そこで、本発明の酸化物超格
子では、分極軸方向を各酸化物薄膜の配向方向（結晶成
長方向）から傾けることにより、上記のように残留分極
は小さくなるが、比誘電率の大きな酸化物超格子を得る
ことができた。しかも、残留分極が小さくなることで、
高周波デバイスへの応用を考えた場合キャパシタ材料と
してもより好ましいものが得られた。However, the remanent polarization of the ferroelectric has a strong azimuth dependence, and tends to be high in the direction of the polarization axis and low in the direction different from the polarization axis. Therefore, in the oxide superlattice of the present invention, the remanent polarization is reduced as described above by inclining the polarization axis direction from the orientation direction (crystal growth direction) of each oxide thin film. A superlattice was obtained. Moreover, by reducing the remanent polarization,
In consideration of application to a high-frequency device, a more preferable capacitor material was obtained.
【００２２】図７は、各酸化物薄膜の層厚が２６ｎｍ、
１０ｎｍ、４ｎｍ、２ｎｍ、１.２ｎｍ、０.４ｎｍの酸
化物超格子について、各比誘電率の周波数依存性を測定
したものである。すなわち、図７の横軸は交流印加電圧
の周波数を示し、縦軸は交流印加電圧に対する酸化物超
格子の比誘電率を表している。図７から分かるように、
本発明による酸化物超格子では、少なくとも１０４〜１
０６Ｈｚの周波数帯域で安定した比誘電率の値を示し
た。さらに、本発明の酸化物超格子では、マイクロ波領
域においても、安定した容量の周波数特性の実現が大い
に期待できる。FIG. 7 shows that the thickness of each oxide thin film is 26 nm,
The frequency dependence of the relative dielectric constant of each of the oxide superlattices of 10 nm, 4 nm, 2 nm, 1.2 nm, and 0.4 nm was measured. That is, the horizontal axis in FIG. 7 indicates the frequency of the AC applied voltage, and the vertical axis indicates the relative permittivity of the oxide superlattice with respect to the AC applied voltage. As can be seen from FIG.
In the oxide superlattice according to the invention, at least 10 4 -1
0 indicated a value of a stable dielectric constant at 6 Hz of frequency bands. Furthermore, in the oxide superlattice of the present invention, realization of stable frequency characteristics of capacitance can be greatly expected even in a microwave region.
【００２３】なお、上記実施形態では、基板の上にＢａ
ＴｉＯ３薄膜とＳｒＴｉＯ３薄膜の（１１１）面配向膜
について述べたが、図３に示すように、ＢａＴｉＯ３薄
膜１２とＳｒＴｉＯ３薄膜１３のような２種の酸化物薄
膜を基板１１の上に（１１０）面配向させたものでもよ
い。また、３種以上の酸化物薄膜を繰り返しエピタキシ
ャル成長させたものであってもよい。In the above embodiment, Ba is placed on the substrate.
The (111) plane oriented film of the TiO 3 thin film and the SrTiO 3 thin film has been described. As shown in FIG. 3, two kinds of oxide thin films such as a BaTiO 3 thin film 12 and a SrTiO 3 thin film 13 are formed on the substrate 11. The (110) plane may be used. Further, three or more oxide thin films may be repeatedly epitaxially grown.
【００２４】[0024]
【発明の効果】本発明によれば、誘電特性の良好な酸化
物超格子を製作することができる。すなわち、酸化物超
格子の比誘電率を高くすることができ、また、広い周波
数領域にわたって比誘電率の安定した酸化物超格子を得
ることができる。According to the present invention, an oxide superlattice having good dielectric properties can be manufactured. That is, the relative permittivity of the oxide superlattice can be increased, and an oxide superlattice having a stable relative permittivity over a wide frequency range can be obtained.
【図１】従来の酸化物超格子の構造を示す概略断面図で
ある。FIG. 1 is a schematic sectional view showing the structure of a conventional oxide superlattice.
【図２】本発明の一実施形態による酸化物超格子の構造
を示す概略断面図である。FIG. 2 is a schematic sectional view showing the structure of an oxide superlattice according to one embodiment of the present invention.
【図３】本発明の別な実施形態による酸化物超格子の構
造を示す概略断面図である。FIG. 3 is a schematic sectional view showing a structure of an oxide superlattice according to another embodiment of the present invention.
【図４】本発明にかかる酸化物超格子の比誘電率と、各
酸化物薄膜の層厚との関係を示す測定データである。FIG. 4 is measurement data showing the relationship between the relative permittivity of the oxide superlattice according to the present invention and the thickness of each oxide thin film.
【図５】本発明にかかる酸化物超格子の分極と印加電圧
との関係を示す測定データである。FIG. 5 is measurement data showing the relationship between the polarization of the oxide superlattice according to the present invention and the applied voltage.
【図６】ＳｒＢａＴｉＯ３固溶体薄膜の比誘電率と膜厚
との関係を示す測定データである。FIG. 6 is measurement data showing the relationship between the relative dielectric constant and the film thickness of a SrBaTiO 3 solid solution thin film.
【図７】本発明にかかる酸化物超格子の交流印加電圧に
対する比誘電率と、印加電圧の周波数との関係を示す測
定データである。FIG. 7 is measurement data showing the relationship between the relative dielectric constant of an oxide superlattice according to the present invention with respect to an AC applied voltage and the frequency of the applied voltage.
１１ 基板 １２ ＢａＴｉＯ３薄膜 １３ ＳｒＴｉＯ３薄膜DESCRIPTION OF SYMBOLS 11 Substrate 12 BaTiO 3 thin film 13 SrTiO 3 thin film
Claims (6)
はＣａ、Ｓｒ、Ｂａ、Ｐｂ、Ｌａからなる群より選択さ
れた少なくとも１種の元素；ＢはＴｉ、Ｚｒ、Ｎｂ、Ｔ
ａからなる群より選択された少なくとも１種の元素）で
表される少なくとも２種類のペロブスカイト型酸化物薄
膜が積層された酸化物超格子において、 前記酸化物薄膜が、それぞれの分極軸と異なる方位に配
向していることを特徴とする酸化物超格子。1. The method according to claim 1, wherein the chemical formula ABO 3 (where A
Is at least one element selected from the group consisting of Ca, Sr, Ba, Pb, and La; B is Ti, Zr, Nb, T
a) at least two kinds of perovskite-type oxide thin films represented by at least one element selected from the group consisting of: a. An oxide superlattice, characterized in that the oxide superlattice is oriented.
ＳｒＴｉＯ３薄膜であることを特徴とする、請求項１に
記載の酸化物超格子。2. The oxide superlattice according to claim 1, wherein the oxide thin film is a BaTiO 3 thin film and a SrTiO 3 thin film.
面配向していることを特徴とする、請求項１又は２に記
載の酸化物超格子。3. The method according to claim 1, wherein each of the oxide thin films is (111).
The oxide superlattice according to claim 1, wherein the oxide superlattice is plane-oriented.
面配向していることを特徴とする、請求項１又は２に記
載の酸化物超格子。4. The oxide thin film according to claim 1, wherein
The oxide superlattice according to claim 1, wherein the oxide superlattice is plane-oriented.
とを特徴とする、請求項１に記載の酸化物超格子。5. The oxide superlattice according to claim 1, wherein the substrate is an oxide single crystal substrate.
Ｏ３、ＢａＴｉＯ３、ＬｉＮｂＯ３、ＬｉＴａＯ３、Ｍ
ｇＯ、ＬａＡｌＯ３、Ａｌ２Ｏ３、ＳｉＯ２、（ＬａＡ
ｌＯ３）（Ｓｒ２ＡｌＴａＯ６）のいずれか１つによっ
て形成されていることを特徴とする、請求項５に記載の
酸化物超格子。6. The oxide single crystal substrate is made of SrTi
O 3 , BaTiO 3 , LiNbO 3 , LiTaO 3 , M
gO, LaAlO 3 , Al 2 O 3 , SiO 2 , (LaA
6. The oxide superlattice according to claim 5, wherein the oxide superlattice is formed of any one of lO 3 ) (Sr 2 AlTaO 6 ). 7.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2000077006A JP2001302400A (en) | 2000-02-18 | 2000-03-17 | Oxide superlatice |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2000-41617 | 2000-02-18 | ||
| JP2000041617 | 2000-02-18 | ||
| JP2000077006A JP2001302400A (en) | 2000-02-18 | 2000-03-17 | Oxide superlatice |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JP2001302400A true JP2001302400A (en) | 2001-10-31 |
Family
ID=26585685
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
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| Country | Link |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2010064942A (en) * | 2008-09-12 | 2010-03-25 | Kyushu Univ | Method for producing perovskite oxide thin film, and perovskite oxide thin film |
| US7872402B2 (en) | 2007-10-02 | 2011-01-18 | Fujifilm Corporation | Perovskite-oxide laminates, and piezoelectric devices, and liquid discharge devices containing the same |
| JP2016029708A (en) * | 2014-07-23 | 2016-03-03 | Tdk株式会社 | Thin-film dielectric and thin-film capacitor element |
| JP2016204189A (en) * | 2015-04-20 | 2016-12-08 | 株式会社村田製作所 | Dielectric thin film |
| JP2017130634A (en) * | 2016-01-22 | 2017-07-27 | 富士通株式会社 | Thin film laminate, manufacturing method thereof, and water decomposition system |
| CN107171653A (en) * | 2017-04-13 | 2017-09-15 | 天津理工大学 | A kind of SAW device with high electromechanical coupling factor and high center frequency |
-
2000
- 2000-03-17 JP JP2000077006A patent/JP2001302400A/en active Pending
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7872402B2 (en) | 2007-10-02 | 2011-01-18 | Fujifilm Corporation | Perovskite-oxide laminates, and piezoelectric devices, and liquid discharge devices containing the same |
| JP2010064942A (en) * | 2008-09-12 | 2010-03-25 | Kyushu Univ | Method for producing perovskite oxide thin film, and perovskite oxide thin film |
| JP2016029708A (en) * | 2014-07-23 | 2016-03-03 | Tdk株式会社 | Thin-film dielectric and thin-film capacitor element |
| JP2016204189A (en) * | 2015-04-20 | 2016-12-08 | 株式会社村田製作所 | Dielectric thin film |
| JP2017130634A (en) * | 2016-01-22 | 2017-07-27 | 富士通株式会社 | Thin film laminate, manufacturing method thereof, and water decomposition system |
| CN107171653A (en) * | 2017-04-13 | 2017-09-15 | 天津理工大学 | A kind of SAW device with high electromechanical coupling factor and high center frequency |
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