JPH06234520A - Oxide thin film laminate having multilayered structure and its production - Google Patents

Abstract

PURPOSE:To provide the production method of an oxide thin film laminate having multilayered structure which enables the formation of the high pressure-stable phase of the oxide thin film laminate under a nearly atmospheric pressure that is difficult to perform with the conventional methods through making clear the problems on the formation of the high pressure-stable phase and also to provide the oxide thin film laminate produced by this production method. CONSTITUTION:The oxide thin film laminate having multilayered structure is produced by sequentially laminating oxide thin films having the mutually same or analogous crystal structure and mutually different compositions from each other from the atmospheric pressure-stable phase thin film 2 up to the high pressure-stable phase thin film 3 while cyclically changing the compositions of these thin films. This production method includes a stage for depositing the atmospheric pressure-stable phase thin film 2 by the epitaxial growth using raw materials that can provide both compositions of the atmospheric pressure-stable phase thin film 2 and the high pressure-stable phase thin film 3, and another stage for depositing plural thin films, which have the same or analogous crystal structure mutually same as or analogous to the atmospheric pressure-stable phase thin film 2 and mutually different compositions from each other, up to the high pressure-stable phase thin film 3 by the epitaxial growth while cyclically changing the compositions of the thin films. Thus, this production has the advantage of enabling the synthesis of the high pressure-stable compound under a nearly atmospheric pressure that is difficult to perform by positively using the epitaxial growth for forming the thin films.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-layered oxide thin film and a method for producing the same, and more particularly to a multi-layered oxide thin film in which oxide thin films are laminated in an infinite layer structure and a method for producing the same.

[0002]

2. Description of the Related Art In the synthesis of various materials,
Bridgman furnace, LEC method, C
In the Z method, and in the symptom thickness region, a high pressure vessel such as a cubic anvil, a diamond anvil, and a dividing sphere is used, and synthesis is performed under an appropriate temperature condition. However, these methods have problems that an expensive and large-sized apparatus must be used, a sample synthesis space is small, and a sufficient amount of synthesis cannot be performed. Further, under these extreme conditions, there is a constraint that the conditions cannot be freely changed in-situ (in situ) during sample preparation.
Furthermore, in the ultra-high pressure experiment, the solid pressure using zirconia, magnesia powder, etc. as the pressure medium becomes
Due to the non-uniform distribution of temperature and the like, it is difficult to unify the target phase, and it is difficult to obtain a high-quality sample for use in various physical property measurements.

Further, vapor deposition method, sputtering method, CVD
In the film forming method such as the MOCVD method and the MOCVD method, the atmospheric stable phase is usually formed on an appropriate substrate. Since a film having a high-pressure phase composition takes the form of a thermodynamically stable normal-pressure stable phase at normal pressure, it is usually difficult to obtain a high-pressure stable phase near normal pressure. Only the high-pressure phase of carbon, diamond, is obtained by the CVD method.

For example, an infinite layer structure material ACuO ₂ (A = alkali ion) in a copper oxide superconductor is formed by repeating a two-dimensional surface of CuO ₂ and a surface made of alkali ions. It has the simplest crystal structure among them. This compound has a different ionic radius such as Sr, Ca, or Ba at the position of the alkali ion A,
Or the average ionic radius rA of the A-site ion changed by placing a combination thereof, between the CuO ₂ planes adjacent distance, and CuO ₂ within plane of Cu-
The O bond length can be changed. In normal pressure synthesis, Ca
_An infinite layer structure is obtained only in an extremely narrow composition region centered on the composition of _0.84 Sr _0.16 CuO ₂ . It is difficult to dope a carrier in a sample obtained by such atmospheric synthesis, and a sample showing superconductivity cannot be obtained.

On the other hand, under an ultrahigh pressure of about 60,000 atm, an infinite layer structure can be obtained with a composition wider than that of the sample obtained by atmospheric synthesis. Sr _0.86 Ca _0.14 CuO ₂
It is possible to obtain a compound having a large A site average ionic radius rA, such as SrCuO ₂ or SrCuO ₂ . It is known that some infinite layer materials having a composition region having a large average ionic radius rA of A site ions exhibit superconductivity and the transition temperature thereof reaches 110K. In this way, infinite layer structure materials have a high superconducting transition temperature despite their simple crystal structure, so they are important for elucidating the high-temperature superconducting mechanism and realizing superconductors with higher transition temperatures. Seems to play a role. However, in the ultra-high pressure synthesizer, since the amount of deposit for synthesizing the sample in the high pressure generating part is small, it is not possible to obtain a sample with sufficient deposit to be used for various physical property measurements. Moreover, since solid powder is used as the pressure medium, nonuniformity of pressure and temperature is likely to occur in the sample. Therefore, it is currently difficult to obtain a high quality sample.

On the other hand, many attempts have been made to produce a thin film of a high-pressure phase of an infinite layer structure substance by a thin film technique such as a vapor deposition method and a sputtering method. An infinite layer structure has been realized in a wider composition range than that of a sintered body, and among them, a sample showing a superconducting start temperature of 110 K or higher has been reported. However, all samples show only broad superconducting transition. This is due to the non-uniformity of composition in the sample,
It is considered that this is due to poor crystallinity and insufficient carrier doping. Direct high pressure stable phase single composition film
With the method of depositing on another single crystal substrate such as gO or SrTiO _3, it is difficult to produce a high-quality thin film having a high-pressure phase composition because of large lattice mismatch.

For doping carriers,
A film with a non-stoichiometric composition is produced by forming vacancies and substituting different elements. Due to this carrier doping, it is extremely difficult to realize a film of a high-pressure phase having a non-stoichiometric composition that is more thermodynamically unstable in a high-pressure phase that is originally thermodynamically unstable.

The difficulty in producing the infinite layer structure as described above is due to the difficulty in realizing the high-pressure phase. In order to overcome such difficulties in producing a high-pressure phase,
It has been desired to develop an infinite layer structure material that realizes a superlattice structure by epitaxial growth using a thin film manufacturing technique, stabilizes a high-pressure phase by stress acting between layers, and doping carriers, and a manufacturing method thereof.

[0009]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The present invention has revealed the problems in producing a high-pressure stable phase and has heretofore been difficult. Is to provide.

[0010]

In order to solve the above problems, the multi-layered oxide thin film according to the present invention has the same or similar crystal structure, and oxide thin films having different compositions are periodically prepared. Alternatively, it is characterized in that the normal pressure stable phase and the high pressure stable phase are sequentially laminated.

In the method for producing a multi-layered oxide thin film according to the present invention, the atmospheric pressure stable phase thin film is deposited by epitaxial growth using a raw material capable of realizing the composition of the atmospheric pressure stable phase and the high pressure stable phase. The method is characterized by including a step of depositing a plurality of films having the same or similar crystal structure as the thin film and different compositions, by periodically changing the composition to form a high-pressure stable phase thin film by epitaxial growth.

That is, the present invention uses a thin film forming technique,
The present invention is characterized in that a superlattice structure is realized by epitaxial growth, a high-pressure phase is stabilized by a stress acting between layers, and a carrier-doped multi-layered oxide thin film of an infinite layer structure material and a manufacturing method thereof are obtained.

In the present invention, in order to obtain a high-pressure stable phase, the composition of the high-pressure stable phase to be grown and the composition of the normal-pressure stable phase are 2
It uses raw materials that can realize different types. The form of the raw material is not basically limited in the present invention, and can be changed depending on the film forming method. In the case of the vapor deposition method, it is made into a liquid state by heating, and in the case of the sputtering method, it is a sintered body. All of them are of high purity.

Such a raw material source is installed in the film forming apparatus, and the constituent elements of the target thin film are simultaneously or sequentially blown in the form of atoms or molecules. First, using a suitable substrate, at a substrate temperature at which single crystal growth occurs, a thin film of a stable phase at atmospheric pressure is prepared. Next, by adjusting the deposition rate of each element, the composition of the thin film is continuously changed from the normal pressure stable phase composition to the high pressure stable phase composition. At this time, the unstable phase is sequentially stabilized by sequentially performing epitaxial growth on the normal pressure stable phase. By doing so, a high-pressure stable phase composition can be realized.

In order to further stabilize the high-pressure phase portion, a film having a composition which gradually changes from the high-pressure phase composition toward the normal-pressure stable phase composition is deposited. In this way, a periodic composition change is realized from the normal pressure stable phase to the high pressure stable phase and further to the normal pressure stable phase.

By utilizing such continuous lattice deformation by epitaxial growth, it is possible to stabilize the high-pressure phase which is difficult to synthesize and bring it to normal pressure. Further, carrier doping can also be realized by introducing defects or elements having different valences by adjusting the composition during film formation. As described above, the present invention realizes a superlattice structure by epitaxial growth using a thin film manufacturing technique, stabilizes a high-pressure phase by utilizing lattice deformation due to stress acting between layers, and obtains a carrier-doped thin film. The present invention provides a membrane structure capable of achieving the above and a manufacturing method thereof.

FIG. 1 shows the structure of the present multi-layered thin film.
1 is a thin film production substrate, 2 is a normal pressure stable phase thin film, 3 is a high pressure stable phase thin film, FIG. 2 is a description of repeating units in the thin film in FIG. 1, 1 is a normal pressure stable phase thin film, and 2 is a normal pressure stable phase thin film. A phase thin film having a crystal structure similar to that of the pressure stable phase thin film 1 and having a composition slightly close to the high pressure stable phase, 3 having a crystal structure similar to that of the thin film 2, and having a composition closer to that of the high pressure stable phase, n-1 is a phase thin film having a crystal structure similar to that of the high pressure stable phase and having a composition slightly deviated from the high pressure stable phase to the normal pressure stable phase side, and n is a high pressure stable phase thin film.

Films 1 to 2, 3 ... n-1, n, n-1 ... 3, of normal pressure stable phase composition are formed on a substrate by various thin film forming methods.
The high-pressure phase is stabilized by depositing films having different compositions in the order of 2 and 1 and performing epitaxial growth. At the stage of forming a thin film of each composition of 1,2,3 ... n-1, n, n-1, ... The carrier doping can be performed by causing the composition shift of the above.

Since the present invention uses a thin film forming technique, any composition distribution can be realized. Thus, the multi-layered oxide thin film and the method for producing the same are characterized in that superlattices having a wide variety of compositions can be obtained under various conditions.

In the present invention, it is difficult to synthesize a thin film by making positive use of epitaxial growth observed between substances having a similar crystal structure, crystal symmetry, and a lattice constant of a close value in the production of a thin film. However, the high-pressure stable compound can be synthesized at near normal pressure.

As an example of the above-mentioned multi-layer structure thin film, for example, the general formula (A _1-x B _x ) _1-y CuO ₂ (A and B are Mg, Sr, Ca and Ba respectively) Alkaline earth element or a mixture thereof, A, B = kMg + lSr + mCa + nBa, provided that k + l + m + n = 1,0 ≦ k ≦ 1,0 ≦ l ≦ 1,0
There can be mentioned a thin film having a multilayer structure in which ≦ m ≦ 1,0 ≦ n ≦ 1) is laminated from a normal pressure stable phase to a high pressure stable phase.

In the case of producing such an oxide multi-layer structure thin film, the composition of the deposited film is sequentially changed from 0 atmospheric pressure stable phase thin film to at least high pressure stable phase thin film in the range of 0 ≦ x ≦ 1, 0 ≦ y ≦ 1. A superlattice structure is produced by epitaxial growth while periodically changing.

As an example of the above-mentioned multi-layered thin film, the general formula (AxByCz) CuO ₂ (where A and B are Mg, Sr, Ca and Ba are alkaline earth elements, or a mixture thereof is used). A, B = kMg + lSr + mCa + nBa, where k + l + m + n = 1,0 ≦ k ≦ 1,0 ≦ l ≦ 1,0
≦ m ≦ 1, 0 ≦ n ≦ 1, and C is La, Ce, Pr,
Nd, Pm, Eu, Gd, Tb, Dy, Ho, Er, T
A rare earth element of m, Yb or Lu, or an element of Sc or Y, or a mixture thereof, and C = n ₁
La + n ₂ Ce + n ₃ Pr + n ₄ Nd + n ₅ Pm + n ₆ Sm
+ N ₇ Eu + n ₈ Gd + n ₉ Tb + n ₁₀ Dy + n ₁₁ Ho +
n ₁₂ Er + n ₁₃ Tm + n ₁₄ Yb + n ₁₅ Lu + n ₁₆ Sc +
n ₁₇ Y, provided that n ₁ + n ₂ + n ₃ + n ₄ + n ₅ + n ₆ + n ₇ +
n ₈ + n ₉ + n ₁₀ + n ₁₁ + n ₁₂ + n ₁₃ + n ₁₄ + n ₁₅ + n ₁₆
+ N ₁₇ = 1,0 ≦ n ₁ ≦ 1,0 ≦ n ₂ ≦ 1,0 ≦ n ₃ ≦
1,0 ≤ n ₄ ≤ 1, 0 ≤ n ₅ ≤ 1, 0 ≤ n ₆ ≤ 1, 0 ≤ n ₇
≤1,0 ≤n ₈ ≤1,0 ≤n ₉ ≤1,0 ≤n ₁₀ ≤1,0≤
n ₁₁ ≤1,0 ≤n ₁₂ ≤1,0 ≤n ₁₃ ≤1,0 ≤n ₁₄ ≤
1,0 ≦ n ₁₅ ≦ 1,0 ≦ n ₁₆ ≦ 1,0 ≦ n ₁₇ ≦ 1, further x + y + z = 1,0 ≦ x ≦ 1,0 ≦ y ≦ 1,0 ≦ z ≦
An example of the thin film is a multilayer structure in which 1) is laminated from a stable phase at normal pressure to a stable phase at high pressure.

In the case of producing such an oxide multi-layered thin film, the composition of the film to be deposited is 0≤x≤1,0≤y≤1,0≤ from the normal pressure stable phase thin film to at least the high pressure stable thin film.
A superlattice structure is produced by epitaxial growth while sequentially and periodically changing within z ≦ 1.

[0025]

Example 1 Three types of raw materials, SrO, CaO, and CuO, were placed in a Knudsen cell as vapor deposition sources, and Ca:
It was deposited on a single crystal substrate for epitaxial growth heated to an appropriate temperature so that the ratio of Sr: Cu = (1-x): x: 1 was obtained. Introduce oxygen gas from the outside near the substrate,
By applying a high-frequency electric field with the rf coil, oxygen plasma was generated to accelerate the oxidation reaction on the substrate. As the substrate, a SrTiO ₃ single crystal substrate having a value close to the lattice constant of Ca _0.86 Sr _0.14 CuO ₂ was used.

In depositing the film, first, a film of Ca _0.86 Sr _0.14 CuO ₂ having a composition of x = 0.14 is deposited on the substrate in an amount of about 100 Å, and then a film having a composition of x = 0.16 is formed into a thick film. 30 Å Furthermore, if x = 0.18, then 30
Å, then x = 0.20 and so on were sequentially deposited to grow a film up to a high temperature stable phase composition of x = 0.86. Next, from above, a film having a stable composition at atmospheric pressure was deposited while gradually changing the value of x to a smaller value. The position of the diffraction line seen in the X-ray diffraction pattern of this film is a broad peak spreading from the peak position corresponding to the normal pressure stable phase to the peak position corresponding to the high pressure stable phase,
Furthermore, the fact that peaks are seen at the positions corresponding to the interplanar spacings corresponding to the period of the superlattice also yields films with successively varying lattice constants, indicating that a high-pressure stable phase exists in them. is there. When a film having a high-pressure stable phase composition is deposited during film formation, the molar ratio is (Ca, Sr): Cu = 0.98:
In the film made to be 1, as shown in FIG.
A film showing a superconducting transition was obtained at 110K. When Ba was used instead of Sr, the superconducting transition temperature of the obtained film was 90K.

[0027]

Example 2 A disk-shaped sintered body having two compositions of (Sr _0.84 Nd _0.16 ) Cu _1.2 O ₂ and (Ca _0.84 Sr _0.16 ) Cu _1.2 O ₂ was prepared and used as a sputtering target. Targets of these two types of compositions were discharged at the same time, and the single crystal substrate for epitaxial growth heated to an appropriate temperature was moved alternately near the two targets to deposit a thin film. Substrate is Ca _0.86 Sr _0.14 CuO
A SrTiO ₃ single crystal substrate having a value close to the lattice constant of ₂ was used. The composition and thickness of the film were adjusted by the residence time near the target. A rotating substrate holder was used for the actual movement of the substrate. With such a method, the thickness is 40
Å, was obtained 50Å of a _{(Sr 0.84 Nd 0.16) Cu 1.} 2 O 2 and _{(Ca 0.84 Sr 0.16) Cu 1.2} O 2 of the film of the total thickness 3000Å film is deposited alternately composition. The positions of the diffraction lines seen in the X-ray diffraction pattern of the film are at the positions corresponding to the stable phase at normal pressure and the stable phase at high pressure, and a peak is found at the position corresponding to the interplanar spacing corresponding to the period of the superlattice. This means that the high-pressure stable phase is stabilized by being sandwiched between the normal-pressure stable phase films. As a result of measuring the temperature dependence of the magnetic susceptibility, it was confirmed that the multilayer film sample thus obtained exhibits a superconducting transition at Tc = 60K. S
Mg or Ba is used instead of r, and Nd is replaced by
La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, T
When a rare earth element such as b, Dy, Ho, Er, Tm, Yb, and Lu or Sc, Y was used, a film having a superconducting transition temperature of 70K at maximum could be obtained.

[0028]

EFFECTS OF THE INVENTION According to the present invention, there is an advantage that a high-pressure stable compound, which has hitherto been difficult to synthesize near atmospheric pressure, can be produced by positively utilizing epitaxial growth in thin film production. is there.

[Brief description of drawings]

FIG. 1 shows the structure of the thin film.

FIG. 2 shows a repeating unit in the thin film in FIG.

FIG. 3 (Ca, Sr) _0.98 obtained according to Example 1.
3 shows a superconducting transition in resistance measurement of a CuO ₂ film.

[Explanation of symbols]

 1 Substrate for thin film production 2 Normal pressure stable phase 3 High pressure stable phase

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location H01B 12/06 ZAA 7244-5G 13/00 565 D 7244-5G H01L 39/24 ZAA B 9276-4M (72) Inventor Minoru Suzuki 1-6, Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (6)

[Claims] 1. A multi-layer comprising oxide thin films having the same or similar crystal structure and different compositions, which are sequentially laminated from the normal pressure stable phase to the high pressure stable phase by periodically changing the composition. Structural oxide thin film. 2. The composition of a plurality of laminated films is represented by the general formula (A _1-x B _x ) _1-y CuO ₂ (where A and B are Mg, Sr, Ca and Ba, respectively). An element or a mixture thereof, A, B = kMg + lSr + mCa + nBa, provided that k + l + m + n = 1,0 ≦ k ≦ 1,0 ≦ l ≦ 1,0
2. The multi-layered oxide thin film according to claim 1, wherein ≦ m ≦ 1,0 ≦ n ≦ 1). 3. The composition of a plurality of laminated films is represented by the general formula (AxByCz) CuO ₂ (where A and B are each an alkaline earth element of Mg, Sr, Ca or Ba, or a mixture thereof). And A, B = kMg + 1lsr + mCa + nBa, where k + l + m + n = 1,0 ≦ k ≦ 1,0 ≦ l ≦ 1,0
≦ m ≦ 1, 0 ≦ n ≦ 1, and C is La, Ce, Pr,
Nd, Pm, Eu, Gd, Tb, Dy, Ho, Er, T
A rare earth element of m, Yb or Lu, or an element of Sc or Y, or a mixture thereof, and C = n ₁
La + n ₂ Ce + n ₃ Pr + n ₄ Nd + n ₅ Pm + n ₆ Sm
+ N ₇ Eu + n ₈ Gd + n ₉ Tb + n ₁₀ Dy + n ₁₁ Ho +
n ₁₂ Er + n ₁₃ Tm + n ₁₄ Yb + n ₁₅ Lu + n ₁₆ Sc +
n ₁₇ Y, provided that n ₁ + n ₂ + n ₃ + n ₄ + n ₅ + n ₆ + n ₇ +
n ₈ + n ₉ + n ₁₀ + n ₁₁ + n ₁₂ + n ₁₃ + n ₁₄ + n ₁₅ + n ₁₆
+ N ₁₇ = 1,0 ≦ n ₁ ≦ 1,0 ≦ n ₂ ≦ 1,0 ≦ n ₃ ≦
1,0 ≤ n ₄ ≤ 1, 0 ≤ n ₅ ≤ 1, 0 ≤ n ₆ ≤ 1, 0 ≤ n ₇
≤1,0 ≤n ₈ ≤1,0 ≤n ₉ ≤1,0 ≤n ₁₀ ≤1,0≤
n ₁₁ ≤1,0 ≤n ₁₂ ≤1,0 ≤n ₁₃ ≤1,0 ≤n ₁₄ ≤
1,0 ≦ n ₁₅ ≦ 1,0 ≦ n ₁₆ ≦ 1,0 ≦ n ₁₇ ≦ 1, further x + y + z = 1,0 ≦ x ≦ 1,0 ≦ y ≦ 1,0 ≦ z ≦
The multi-layered oxide thin film according to claim 1, which is 1). 4. A step of depositing a normal pressure stable phase thin film by epitaxial growth using a raw material capable of realizing a composition of a normal pressure stable phase and a high pressure stable phase, having the same or similar crystal structure as the normal pressure stable phase thin film, A method for producing a multi-layered oxide thin film, comprising a step of depositing a plurality of high-pressure stable phase thin films by epitaxial growth while periodically changing the composition of different compositions. 5. The composition of the thin film to be epitaxially grown is represented by the general formula (A _1-x B _x ) _1-y CuO ₂ (wherein A and B are alkaline earth elements of Mg, Sr, Ca and Ba, respectively, Alternatively, they are a mixture thereof, and A and B = kMg + 1lsr + mCa + nBa, provided that k + l + m + n = 1,0 ≦ k ≦ 1,0 ≦ l ≦ 1,0
≦ m ≦ 1,0 ≦ n ≦ 1), and the composition of the deposited film is 0
The method for producing a multi-layered oxide thin film according to claim 4, wherein a superlattice structure is formed by epitaxial growth while sequentially and periodically changing between ≤x≤1, 0≤y≤1. 6. The composition of a plurality of laminated films is represented by the general formula (AxByCz) CuO ₂ (where A and B are each an alkaline earth element of Mg, Sr, Ca or Ba, or a mixture thereof). And A, B = kMg + 1lsr + mCa + nBa, where k + l + m + n = 1,0 ≦ k ≦ 1,0 ≦ l ≦ 1,0
≦ m ≦ 1, 0 ≦ n ≦ 1, and C is La, Ce, Pr,
Nd, Pm, Eu, Gd, Tb, Dy, Ho, Er, T
A rare earth element of m, Yb or Lu, or an element of Sc or Y, or a mixture thereof, and C = n ₁
La + n ₂ Ce + n ₃ Pr + n ₄ Nd + n ₅ Pm + n ₆ Sm
+ N ₇ Eu + n ₈ Gd + n ₉ Tb + n ₁₀ Dy + n ₁₁ Ho +
n ₁₂ Er + n ₁₃ Tm + n ₁₄ Yb + n ₁₅ Lu + n ₁₆ Sc +
n ₁₇ Y, provided that n ₁ + n ₂ + n ₃ + n ₄ + n ₅ + n ₆ + n ₇ +
n ₈ + n ₉ + n ₁₀ + n ₁₁ + n ₁₂ + n ₁₃ + n ₁₄ + n ₁₅ + n ₁₆
+ N ₁₇ = 1,0 ≦ n ₁ ≦ 1,0 ≦ n ₂ ≦ 1,0 ≦ n ₃ ≦
1,0 ≤ n ₄ ≤ 1, 0 ≤ n ₅ ≤ 1, 0 ≤ n ₆ ≤ 1, 0 ≤ n ₇
≤1,0 ≤n ₈ ≤1,0 ≤n ₉ ≤1,0 ≤n ₁₀ ≤1,0≤
n ₁₁ ≤1,0 ≤n ₁₂ ≤1,0 ≤n ₁₃ ≤1,0 ≤n ₁₄ ≤
1,0 ≤ n ₁₅ ≤ 1, 0 ≤ n ₁₆ ≤ 1, 0 ≤ n ₁₇ ≤ 1, further x + y + z = 1,0 ≤ x ≤ 1,0 ≤ y ≤ 1, 0 ≤ z ≤
1), and the composition of the deposited film is 0 ≦ x ≦ 1, 0 ≦ y ≦
1. A method for producing a multi-layered oxide thin film, which comprises epitaxially growing while sequentially and periodically changing between 1,0 ≦ z ≦ 1 to form a superlattice structure.