JP2000106036A - Ferroelectric thin film and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a single crystal ferroelectric thin film having a stably controlled composition and fine and good surfacing and crystallizing characteristics. SOLUTION: This thin film contains an Li element and at least one element of Nb and Ta. It is manufactured by the steps of adding a water in an amount, such that the mole ratio of composite metal alkoxide to water is 1:1 to 1:2, to organic solvent of composite metal alkoxide with organic ligands shown in the formula: R1OR2O-(where R1 is an aliphatic hydrocarbon group and R2 is a bivalent aliphatic hydrocarbon group which may have an ether linkage) for partial hydrolysis, of applying a precursor solution obtained in the hydrolysis onto a single crystal substrate, and of giving heat treatment thereto.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a single crystal having a composition controlled precisely, having a smooth surface and high crystallinity, which is epitaxially grown on a single crystal substrate by using heat crystallization of a metal organic compound. The present invention relates to a crystalline ferroelectric thin film and a method for manufacturing the same.

[0002]

2. Description of the Related Art Oxide ferroelectric thin films are characterized by the excellent non-linear optical effect and electro-optical effect of ferroelectrics.
Many applications are expected, such as a second harmonic element, an optical switch, and an optical modulation element. Conventionally, these devices are LiNbO
An optical waveguide structure manufactured by thermal diffusion of Ti or ion exchange of protons using a single crystal wafer of ₃ or LiTaO ₃ has been used. On the other hand, realizing a thin-film optical waveguide structure in which a ferroelectric thin film is heteroepitaxially grown on a single-crystal substrate made of a dissimilar material will increase the efficiency of the second harmonic element and lower the driving of optical switches and optical modulators. It becomes possible to increase the voltage and further to manufacture an optical integrated device.

However, the application of a thin film optical waveguide produced by heteroepitaxial growth of a ferroelectric thin film to a second harmonic element, an optical switch, an optical modulation element, and the like requires low light propagation loss and characteristics similar to those of a single crystal. In order to obtain it, it is indispensable to produce a single crystal ferroelectric thin film. Therefore, LiNbO
₃ , LiTaO ₃ , KNbO _3, etc.
O ₃ , PbTiO ₃ , (Pb _1-x La _x ) (Zr _1-y
Ti _y ) _{1-x / 4} O ₃ (PLZT), Bi ₄ Ti ₃ O ₁₂ and other epitaxial ferroelectric thin films are formed by rf-magnetron sputtering, ion beam sputtering, laser ablation, MOCVD Many are formed on an oxide single crystal substrate by such a vapor growth method.

[0004] However, all the methods are very expensive in equipment and have problems of thin film surface properties, composition control and uniformity, and a practically usable single-crystal ferroelectric thin film has not yet been obtained.

On the other hand, a ferroelectric thin film is obtained by applying a metal organic compound, which has advantages in terms of precise chemical composition control, low temperature of the process, uniformity, low equipment cost, etc., to a substrate and then heating the substrate, A method generally called a sol-gel method is disclosed in Japanese Patent Publication No. 62-27482. In this method, a ferroelectric thin film having a predetermined thickness can be generally obtained by laminating a ferroelectric thin film having a constant thickness of 50 nm to 200 nm. It was only possible to obtain a thin film with a low dielectric constant, so it was not possible to make full use of the physical properties based on the polarization of the ferroelectric, and it was used as an optical waveguide due to too large light scattering by crystal grain boundaries and pinholes. I couldn't do it at all.

[0006] One of the inventors of the present invention is based on K. Nashimoto
o and M.S. J. Cima: Epitaxial
LiNbO ₃ thin films prepare
dby sol-gel process, Mate
r. Lett. , 10 (1991) 348. As shown in the above, in the sol-gel method, a composite metal alkoxide LiNb (OC ₂ H ₅ ) ₆ precursor solution using ethyl alcohol as a solvent is applied onto a sapphire single crystal substrate without any hydrolysis and heated. As a result, they have found that a ferroelectric LiNbO ₃ thin film grows epitaxially on a sapphire single crystal substrate. Specifically, a complex alkoxide LiNb (OC
_As H ₂ O was added to the ₂ H ₅ ) ₆ precursor solution, the baked LiNbO ₃ thin film changed from an oriented film to a polycrystalline film, but no H ₂ O was added and no hydrolysis was performed. When calcined using the precursor, the LiNbO ₃ thin film grows epitaxially at only 400 ° C. When the polycrystalline film and the oriented film were baked at a high temperature, the density of the film was significantly reduced due to the growth of crystal grains and the growth of the pore diameter, but the epitaxial LiNbO ₃
The film has an extremely large sub-grain (a structure with crystal grains, but the orientation of each crystal grain is almost or completely aligned) compared to the polycrystalline film and the oriented film even after the crystal grain growth, and the density is high. Met. The epitaxial film showed a higher refractive index than the polycrystalline film and the oriented film, and the other films became opaque after high-temperature crystal grain growth, but were almost transparent.
However, when studied in detail, the epitaxial LiNbO ₃ ferroelectric thin film baked at a temperature of 400 ° C. has a single crystal shape and a smooth surface, but a TEM (transmission electron microscope).
By observing the cross section of the thin film, it was found that the film contained pores having a diameter of several nm. Therefore, the density was not sufficiently high, and the refractive index was not as high as that of a single crystal. The ferroelectric thin film fired at a temperature of 700 ° C. was a single crystal, had extremely large sub-grains compared to a polycrystalline film and an oriented film, had a high density, and had a refractive index relatively close to that of a single crystal. The film contained some pores, the surface was not optically smooth, and the film was not sufficiently transparent.

A report following the method of the present inventors is described in P. G. FIG. Clem and D. A. Payn
e: Control of heteroepitax
yin sol-gel derived LiNbO
₃ thin layers, Mat. Res. Sym
p. Proc. , 361 (1995) 179. In
It is shown that an epitaxial LiNbO ₃ thin film was obtained by applying an ethyl alcohol solution of a LiNb (OC ₂ H ₅ ) ₆ precursor to a sapphire single crystal substrate and then heating it. However, the half-width of the X-ray diffraction rocking curve, which is a quantitative index of the inclination of the crystal plane of the thin film with respect to the direction parallel to the substrate plane, is 1.2 for a LiNbO ₃ thin film on a sapphire (0001) substrate and 10.5 for sapphire (1120).
The LiNbO ₃ thin film on the substrate is 1.9, which is not as good as that of a single crystal, and has a refractive index of 2.20 to less than that of a single crystal.
There is a problem that only 2.07, which is considerably smaller than 2.29, can be obtained.

[0008]

On the other hand, as a method for obtaining an oriented ferroelectric thin film whose surface is optically smooth and transparent, the present inventors have proposed a precursor solution which is not subjected to hydrolysis. Invented was an oriented multi-layer ferroelectric thin film composed of films having different heat treatment temperatures (Japanese Patent Laid-Open No. 5-342912).
issue). In addition, the boiling point of the solvent of the organic compound or the precursor corresponding to the organic functional group of the composite metal organic compound as a precursor at normal pressure is very important for smoothing the obtained thin film and suppressing pores. Has a boiling point of at least 8 at normal pressure.
It was found that it was desirable to use methoxyethanol at 0 ° C. or higher and methoxyethoxide as a precursor, and applied for a patent (Japanese Patent Application Laid-Open No. 7-78508).
Further, as shown in JP-A-09-329722, a ferroelectric buffer layer having a thickness of 1 nm to 40 nm is provided, and the thickness of the ferroelectric buffer layer is thicker than that of each buffer layer, and the thickness is 10 nm. It was found that by producing a ferroelectric thin film having a thickness of 1000 nm by solid phase epitaxial growth, a ferroelectric thin film having sufficient surface smoothness and crystallinity and having small light propagation loss for use as an optical waveguide can be obtained. .

However, in the above-described process using a precursor that does not perform hydrolysis at all, a small amount of water mixed in during the synthesis of the precursor or during the growth of the thin film affects the surface properties, denseness, crystallinity, etc. of the obtained thin film. And the quality varies.

An object of the present invention is to solve the above-mentioned problems of the prior art and achieve the following objects. That is, an object of the present invention is to provide a single-crystal ferroelectric thin film whose composition is controlled stably, which is dense and has good surface properties and crystallinity, and a method for producing the same.

[0011]

Means for Solving the Problems The present inventors have studied a ferroelectric thin film using solid phase epitaxial growth from a composite metal alkoxide, and, in the production thereof, the influence of moisture on the composite metal alkoxide on the quality of the thin film. As a result of the study, it was found that the composite metal alkoxide having an organic ligand represented by R ¹ OR ² O— and the composite metal alkoxide having an organic ligand represented by R ¹ O— behave differently. The present invention led to the heading. That is,

<1> It contains a Li element and at least one element of Nb and Ta, and the organic ligand has the formula: R ¹ O
R ² O— (wherein R ¹ represents an aliphatic hydrocarbon group, and R ² represents a divalent aliphatic hydrocarbon group which may have an ether bond). The solution has a molar ratio of the composite metal alkoxide to water of 1: 1.
１ ： 1: 2 obtained by a hydrolysis step of partially hydrolyzing by adding water, a coating step of coating the precursor solution obtained in the hydrolysis step on a single crystal substrate, and a heat treatment step. A ferroelectric thin film characterized in that:

<2> An organic solvent solution of the composite metal alkoxide is composed of an organic metal compound or an inorganic compound containing a Li element and at least one of an organic metal compound or an inorganic compound containing an Nb or Ta element as starting materials.
In an alcohol represented by the formula: R ¹ OR ² OH (wherein R ¹ represents an aliphatic hydrocarbon group, and R ² represents a divalent aliphatic hydrocarbon group which may have an ether bond). The ferroelectric substance according to <1>, which is prepared by a dissolving step of dissolving, a distillation step of heating and distilling the solution obtained in the dissolving step while further replenishing the alcohol, and a refluxing step. Manufacturing method of thin film.

<3> The ferroelectric thin film according to <1>, wherein the hydrolysis time is 1 to 10 hours.

<4> The single crystal substrate is made of Al ₂ O ₃ or LiTa
The ferroelectric thin film according to <1>, wherein the ferroelectric thin film is O ₃ , MgO, or ZnO.

<5> An amorphous heating step in which the applied thin film is thermally decomposed to be amorphous at a temperature range of 100 ° C. to 500 ° C. and a solid phase epitaxial growth at a temperature range of 300 ° C. to 1200 ° C. The ferroelectric thin film according to the item <1>, comprising at least an epitaxial heating step for realizing the following.

<6> Heating rate of heat treatment is 1 to 500 ° C.
/ Sec, the ferroelectric thin film according to <1>.

<7> It contains a Li element and at least one element of Nb and Ta, and the organic ligand has the formula: R ¹ O
R ² O— (wherein R ¹ represents an aliphatic hydrocarbon group, and R ² represents a divalent aliphatic hydrocarbon group which may have an ether bond). The solution has a molar ratio of the composite metal alkoxide to water of 1: 1.
A hydrolysis step of partially hydrolyzing by adding water in an amount of about 1: 2, a coating step of coating the precursor solution obtained in the hydrolysis step on a single crystal substrate, and a heat treatment step. A method for manufacturing a ferroelectric thin film characterized by the following.

<8> An organic solvent solution of a composite metal alkoxide is prepared by using, as a starting material, an organometallic compound or an inorganic compound containing an Li element and at least one of an organometallic compound or an inorganic compound containing an Nb or Ta element by the formula :
R ¹ OR ² OH (wherein R ¹ represents an aliphatic hydrocarbon group,
R ² represents a divalent aliphatic hydrocarbon group which may have an ether bond. The above <7 is characterized by being prepared by a dissolving step of dissolving in alcohol shown in the above), a distillation step of heating and distilling the solution obtained in the dissolving step while further replenishing the alcohol, and a refluxing step. > The method for producing a ferroelectric thin film according to <1>.

<9> At least one of the starting materials is L
<8> The method for producing a ferroelectric thin film according to <8>, wherein the ferroelectric thin film is an alkoxide of i, Nb, or Ta.

<10> At least one of the starting materials is L
The method for producing a ferroelectric thin film according to <8>, wherein the ferroelectric thin film is a halide of i, Nb, or Ta.

<11> The method for producing a ferroelectric thin film according to <8>, wherein at least one of the starting materials is metallic Li.

<12> The method for producing a ferroelectric thin film according to <8>, wherein the alcohol is further supplied in a distillation step in an amount of 0.1 to 100 times the volume of the alcohol used in the dissolving step.

<13> The method for producing a ferroelectric thin film according to <7>, wherein the hydrolysis time is 1 to 10 hours.

<14> The single crystal substrate is made of Al ₂ O ₃ or LiT
<7> The method for producing a ferroelectric thin film according to <7>, wherein the ferroelectric thin film is aO ₃ , MgO, or ZnO.

<15> An amorphous heating step in which the heat treatment is performed by thermally decomposing the applied thin film into an amorphous state at a temperature range of 100 ° C. to 500 ° C., and a solid phase epitaxial growth at a temperature range of 300 ° C. to 1200 ° C. And a method for producing a ferroelectric thin film according to the item <7>, which comprises at least an epitaxial heating step of realizing the following.

<16> Heating rate of heat treatment is 1 to 500
<7> The method for producing a ferroelectric thin film according to the item <7>, wherein the temperature is ° C / sec.

The ferroelectric thin film of the present invention has a structure of R ¹ OR ² O—
By using a precursor solution obtained by partially hydrolyzing a composite metal alkoxide having an organic ligand represented by the formula (1), resistance to hydrolysis by moisture mixed during the growth of a thin film or the like can be improved. Further, by controlling the amount of water added for partial hydrolysis, the surface properties and crystallinity of the obtained ferroelectric thin film can be improved.

The method for producing a ferroelectric thin film according to the present invention has a composition controllability, film thickness uniformity, and equipment cost as compared with the conventional vapor phase epitaxial growth method and the conventional solid phase epitaxial growth method using the vapor phase grown film. This is a method of producing a ferroelectric thin film that is dense and has good smoothness and crystallinity by utilizing the hydrolysis of the sol-gel method.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION The ferroelectric thin film of the present invention contains a Li element and at least one of Nb and Ta, and has an organic ligand represented by the formula: R ¹ OR ² O— ¹ represents an aliphatic hydrocarbon group, and R ² represents a divalent aliphatic hydrocarbon group which may have an ether bond.) A hydrolysis step of partially hydrolyzing by adding water in such an amount that the molar ratio with water is 1: 1 to 1: 2, and applying the precursor solution obtained in the hydrolysis step onto a single crystal substrate; It is obtained by a coating step and a heat treatment step.

Hereinafter, the ferroelectric thin film of the present invention will be described through a manufacturing method. The method for producing a ferroelectric thin film of the present invention comprises:
It contains a Li element and at least one element of Nb and Ta, and the organic ligand has a formula: R ¹ OR ² O— (wherein R ¹
Represents an aliphatic hydrocarbon group, and R ² represents a divalent aliphatic hydrocarbon group which may have an ether bond. ) In an organic solvent solution of a composite metal alkoxide (hereinafter, referred to as an organic solvent solution of the composite metal alkoxide) in an amount such that the molar ratio of the composite metal alkoxide to water is 1: 1 to 1: 2. In addition, the production method includes a hydrolysis step of partially hydrolyzing, a coating step of coating the precursor solution obtained in the hydrolysis step on a single crystal substrate, and a heat treatment step.

[0032] The composite metal alkoxide, a Li element, and at least one element of Nb and Ta, the organic ligand has the formula: a composite metal alkoxide represented R ¹ OR ² O-in, R ¹ Represents an aliphatic hydrocarbon group, and R ² represents a divalent aliphatic hydrocarbon group which may have an ether bond. As the aliphatic hydrocarbon group, an alkyl group having 1 to 4 carbon atoms is preferable. Examples of the divalent aliphatic hydrocarbon group which may have an ether bond include an alkylene group having 2 to 4 carbon atoms, and a total of 4 to 4 carbon atoms in which an alkylene group having 2 to 4 carbon atoms is bonded by an ether bond. 6 divalent aliphatic hydrocarbon groups are preferred.

As the composite metal alkoxide, Li
Nb (OCH ₂ OCH ₃ ) ₆ , LiTa (OCH ₂ OC
H ₃ ) ₆ , LiNb _0.5 Ta _0.5 (OCH ₂ OCH ₃ )
₆ , LiNb (OC ₂ H ₅ OCH ₃ ) ₆ , LiTa (O
_{C 2 H 5 OCH 3) 6} , and the like. Among them, LiNb (OC ₂ H ₅ OCH ₃ ) ₆ is preferable.

Examples of the organic solvent include alcohols represented by R ¹ OR ² OH. These may be used alone or in combination of two or more.

The alcohol represented by R ¹ OR ² OH preferably has a boiling point at normal pressure of 80 ° C. or higher and facilitates the alcohol exchange reaction of metal alkoxide. For example, CH ₃ OCH ₂ CH ₂ OH (boiling point 12
4.5 ° C.), C ₂ H ₅ OCH ₂ CH ₂ OH (boiling point 135
C) and C ₄ H ₉ OCH ₂ CH ₂ OH (boiling point 171 ° C.) are particularly preferred, but not limited thereto.

The solution of the composite metal alkoxide in an organic solvent is not particularly limited, but may be a commercially available mixture of a desired composite metal alkoxide and an organic solvent at a predetermined concentration, or as shown below. May be prepared.

A preferable method for preparing the organic metal solution of the composite metal alkoxide is that at least one of an organic metal compound or an inorganic compound containing an Li element and an organic metal compound or an inorganic compound containing an Nb or Ta element is used as a starting material. Is represented by the formula: R ¹ OR ² OH (wherein R ¹ represents an aliphatic hydrocarbon group, and R ² represents ² which may have an ether bond)
And a monovalent aliphatic hydrocarbon group. ), A dissolving step of dissolving in alcohol, a distillation step of heating and distilling the solution obtained in the dissolving step while further replenishing the alcohol, and a reflux step.

The starting material may be Li, Nb or T
a, and an organic metal compound such as a metal alkoxide whose organic ligand is represented by R ¹ O—, an inorganic compound such as Li, Nb or Ta halide, and metal Li.

As the metal alkoxide containing Li, Nb or Ta, wherein the organic ligand is represented by R ¹ O—,
iOR ¹ , Nb (OR ¹ ) ₆ and Ta (OR ¹ ) ₆ .

Examples of the Li, Nb or Ta halide include LiCl, NbCl and TaCl.

From the starting materials, at least one of a metal alkoxide containing a Li element, a metal alkoxide containing a Nb element, and a metal alkoxide containing a Ta element is synthesized by the following operations. The organic ligand of these metal alkoxides is R ¹ O— or R ¹ O
R ^2- .

When the starting material contains Li, Nb or Ta, and the organic ligand is a metal alkoxide represented by R ¹ O—, these are converted into an alcohol represented by R ¹ OR ² OH. The alcohol exchange reaction is performed by distillation or reflux, whereby R ¹ O is used as an organic ligand.
The metal alkoxide of R ² O— is synthesized.

When the starting material is a metal halide of Li, Nb or Ta, these may be replaced with R ¹ OH or R ¹ OH.
^By mixing with an alcohol represented by ¹ OR ² OH and stirring while passing ammonia, the metal alkoxide of R ¹ O— or R ¹ OR ² O— is synthesized as an organic ligand.

When the starting material is metal Li,
By refluxing in an alcohol represented by R ¹ OH or R ¹ OR ² OH, the metal alkoxide of R ¹ O— or R ¹ OR ² O— is synthesized as an organic ligand.

From the metal alkoxide containing the Li element and at least one of the metal alkoxide containing the Nb element and the metal alkoxide containing the Ta element obtained as described above, the composite metal Alkoxides are synthesized. The synthesis of the metal alkoxide may be performed simultaneously with the following operation.

The organic ligand of the metal alkoxide is R ¹
In the case of O—, R ¹ OR ² O— of the organic ligand R ¹ O—
Alcohol exchange to, for the purpose of compounding the metal alkoxide, the metal alkoxide in a predetermined composition,
The dissolving step of dissolving in the alcohol represented by the formula: R ¹ OR ² OH, the distillation step of heating and distilling the solution obtained in the dissolving step while further replenishing the alcohol, and the refluxing step allow the composite metal alkoxide to be formed. Synthesized.

The organic ligand of the metal alkoxide is R¹
OR^TwoIn the case of O-, the aim is to compound the metal alkoxide.
As a target, the metal alkoxide in a predetermined composition,
Formula: R ¹OR^TwoSoluble in alcohol represented by OH
A dissolving step, and adding the alcohol to the solution obtained in the dissolving step.
Distillation step of heating distillation while further replenishing
Depending on the process, the composite metal alkoxide is synthesized.

In the distillation step, the capacity for further replenishing the alcohol is preferably 0.1 to 100 times, more preferably 2 to 100 times, more preferably 2 to 10 times the volume of the alcohol used in the dissolving step. . 0.
If the volume is less than 1 volume, the alcohol exchange of the organic ligand R ¹ O— of the metal alkoxide to R ¹ OR ² O— tends to be insufficient. It is presumed that alcohol exchange of the ligand and complexation of the metal alkoxide cannot be expected.

The above-mentioned distillation step is preferably carried out at a temperature not lower than the boiling point of the alcohol as the solvent.

In the distillation step, the distillation time is from 1 to
24 hours is preferable, and 2 to 10 hours is more preferable. 1
If the time is less than the time, the alcohol exchange of the organic ligand R ¹ O— of the metal alkoxide to the R ¹ OR ² O— tends to be insufficient. If the time exceeds 24 hours, the organic ligand of the metal alkoxide further increases. It is presumed that alcohol exchange and compounding of metal alkoxide cannot be expected.

The refluxing step is preferably performed at a temperature equal to or higher than the boiling point of the solvent alcohol.

In the reflux step, the reflux time is as follows:
Preferably 1 to 24 hours, more preferably 10 to 22 hours. If the time is less than 1 hour, complexing of the metal alkoxide tends to be insufficient. If the time exceeds 24 hours, it is presumed that further complexing of the metal alkoxide cannot be expected.

The concentration of the composite metal alkoxide in the organic solvent is preferably 0.01 to 3 (mol / l), more preferably 0.05 to 1.5 (mol / l).

In the solution of the composite metal alkoxide in the organic solvent, the molar ratio of the composite metal alkoxide to water is 1: 1 to 1: 1.
By adding water in an amount of 1: 2 to cause hydrolysis,
A precursor solution in which the composite metal alkoxide is partially hydrolyzed can be obtained.

The amount of water to be added to the solution of the composite metal alkoxide in the organic solvent is such that the molar ratio of the composite metal alkoxide to water is from 1: 1 to 1: 2 and from 1: 1.3 to 1: 2.
An amount of 1: 1.7 is more preferred. When the amount is less than 1: 1, the crystallinity of the obtained thin film decreases with the decrease in the amount of water added, and many pores are observed on the surface. As the amount of added water increases, the crystallinity of the obtained thin film decreases, and many pores and cracks occur on the surface.

The hydrolysis of the organic solvent solution of the composite metal alkoxide is preferably performed at 0 to 120 ° C. for 1 to 10 hours, more preferably at 60 to 90 ° C. for 3 to 6 hours.

When water is added to the organic solvent solution of the composite metal alkoxide and allowed to react, the hydrolysis is carried out at 0 to 50 ° C., preferably 0 to 10 ° C. so that the hydrolysis does not proceed rapidly locally.
Then, it is preferable to add water dropwise, and then gradually heat the solution to cause sufficient hydrolysis.

As a method for adding water to the organic metal solution of the composite metal alkoxide, it is preferable to add a solution obtained by mixing a predetermined amount of water with the organic solvent to the organic metal solution of the composite metal alkoxide, May be added directly to the solution.

The above precursor solution is applied on a single crystal substrate,
By performing the heat treatment, the ferroelectric thin film is grown by solid phase epitaxy.

As the single crystal substrate, α-Al
_TwoO_Three, LiTaO_Three, MgO, MgAl _TwoO_Four, Zn
An oxide single crystal substrate such as O may be used. Single crystal substrate
Must be solvent cleaned, etched, rinsed, and dried.
Preferably

As a method of applying the precursor solution,
Examples include a spin coating method, a dipping method, a spray method, a screen printing method, and an ink jet method. The coating is preferably performed in a dry nitrogen or argon atmosphere from the viewpoint of the quality of the obtained thin film, but coating in the air is also possible.

The heat treatment realizes an amorphous heating step in which the applied thin film is thermally decomposed into an amorphous state at a temperature range of 100 ° C. to 500 ° C. and a solid phase epitaxial growth at a temperature range of 300 ° C. to 1200 ° C. And at least an epitaxial heating step.

As a specific example of the heat treatment, the heat treatment may be performed in an atmosphere containing oxygen, preferably in oxygen, more preferably in oxygen dried for at least a certain time, at a temperature of 1 to 500, preferably 10 to 100 ° C./sec. Heating at a heating rate,
The applied thin film is thermally decomposed into an amorphous state in a temperature range of 00 ° C. to 500 ° C., preferably 200 ° C. to 400 ° C. where crystallization does not occur, and subsequently 1 to 500, preferably 1 to 500 ° C.
Heating at a heating rate of 0 to 100 ° C./sec to 300 ° C.
It is suitable to carry out at a temperature in the range of from 1200 to 1200, preferably from 600 to 800 ° C.

By performing the heat treatment, a ferroelectric thin film is grown by solid phase epitaxial growth from the substrate surface. The thickness at this time is preferably from 50 nm to 200 nm. After each solid phase epitaxial growth, 0.01-10
Cooling is performed at a cooling rate of 0, preferably 1 to 10 ° C./sec.

By the above method, a single crystal substrate made of a different material is dense, has a refractive index similar to that of a single crystal, and has a smooth surface. For example, LiNbO ₃ , LiTaO ₃ , Li (N
_{b 1- x Ta x) O 3} ( ferroelectric thin film of 0 ≦ x ≦ 1) The present invention of an epitaxial or single orientation, such as can be produced.

A particularly effective structure for the combination of the ferroelectric thin film and the single crystal substrate is, for example, LiNbO.
₃ (0001) // Al ₂ O ₃ (0001), LiNb
O ₃ (1120) // Al ₂ O ₃ (1120), LiN
bO ₃ (0001) // LiTaO ₃ (0001), L
iNbO ₃ (0001) // MgO (111), LiN
bO ₃ (0001) // MgAl ₂ O ₄ (111),
LiNbO ₃ (0001) // ZnO (001), Li
NbO ₃ (0001) // Al doped ZnO (00
1), LiTaO ₃ (0001) // Al ₂ O ₃ (00
01), LiTaO ₃ (1120) // Al ₂ O ₃ (1
120), LiTaO ₃ (0001) // MgO (11
1), LiTaO ₃ (0001) // MgAl ₂ O
₄ (111), LiTaO ₃ (0001) // ZnO
(001), LiTaO ₃ (0001) // Al-doped ZnO (001), and the like, but are not limited thereto.

[0067]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples.

Example 1 Equimolar amounts of LiOC ₂ H ₅ and Nb (OC ₂ H ₅ ) ₆ were dissolved in 2-methoxyethanol CH ₃ OC ₂ H ₄ OH which had been dehydrated with molecular sieves. Distillation was performed for 2 hours while supplying twice the amount of 2-methoxyethanol, and the mixture was refluxed for 22 hours to obtain a composite metal alkoxide LiNb (OC ₂ H ₅ O).
A 1.2 M solution of CH ₃ ) ₆ was obtained.

The resulting solution was allowed to cool to room temperature, and then cooled in an ice bath for 1 hour. While stirring, an amount of water in which the molar ratio of the composite metal alkoxide to water was 1: 1 was added to the above solution. A water / 2-methoxyethanol solution mixed with the same amount of 2-methoxyethanol was added dropwise over 30 minutes, followed by stirring in an ice bath at room temperature for 30 minutes each. This solution was refluxed at 90 ° C. for 3 hours to obtain a precursor solution.

The obtained precursor solution was washed with a solvent, etched, rinsed, and dried with a sapphire single crystal substrate (α
-Al ₂ O ₃ (0001)). All of the above operations were performed in a nitrogen atmosphere.

The substrate on which the obtained precursor solution was spin-coated was heated at a rate of 20 ° C./s in an oxygen atmosphere and heated at 300 ° C. for 2 hours.
Hold at 20 ° C / s for 30 minutes at 700 ° C.
After holding for about 1 minute, the film was naturally cooled to obtain a thin film of Example 1 having a thickness of about 80 nm.

According to the X-ray diffraction analysis, the obtained thin film of Example 1 did not show any misorientation plane, and the LiNbO ₃ (00
The strength of the 06) plane was 32 kcps. Also, SEM
As a result of observation, the surface had a smooth and dense surface without cracks, and the refractive index was 2.21, a large value comparable to that of a single crystal.

Comparative Example 1 In the same manner as in Example 1, equimolar amounts of LiOC ₂ H ₅ and Nb (OC ₂ H ₅ ) ₆ were dehydrated with molecular sieves to form 2-methoxyethanol CH ₃ O.
The mixed metal alkoxide LiN was dissolved in C ₂ H ₄ OH and distilled for 2 hours while supplying 2-methoxyethanol twice as much as the charge, followed by refluxing for 22 hours.
A 1.2 M solution of b (OC ₂ H ₅ OCH ₃ ) ₆ was obtained.

After the resulting solution was allowed to cool to room temperature, it was cooled in an ice bath for 1 hour, and while stirring, water was added in an amount such that the molar ratio of the composite metal alkoxide to water was 1: 0.5. Water / 2-mixed with the same amount of 2-methoxyethanol as solution
A methoxyethanol solution was added dropwise over 30 minutes, followed by stirring in an ice bath at room temperature for 30 minutes each. This solution was refluxed at 90 ° C. for 3 hours to obtain a precursor solution.

The obtained precursor solution was washed with a solvent, etched, rinsed, and dried with a sapphire single crystal substrate (α
-Al ₂ O ₃ (0001)). All of the above operations were performed in a nitrogen atmosphere.

The substrate on which the obtained precursor solution was spin-coated was heated at a rate of 20 ° C./s in an oxygen atmosphere and heated at 300 ° C. for 2 hours.
Hold at 20 ° C / s for 30 minutes at 700 ° C.
After holding for about 1 minute, the film was naturally cooled to obtain a thin film of Comparative Example 1 having a thickness of about 80 nm.

X-ray diffraction analysis of the obtained thin film of Comparative Example 1 was performed under the same conditions as in Example 1. As a result, misalignment peaks such as (0112), (1014) and (1120) planes of LiNbO ₃ were obtained. And the intensity of the diffraction peak on the (0006) plane was 25 kcps, which was smaller than that of the thin film of Example 1. In addition, SEM observation revealed small grains on the surface and scattered pores, and it was found that the thin film had much lower surface smoothness than the thin film of Example 1.

Comparative Example 2 Equimolar amounts of LiOC ₂ H ₅ and Nb (OC ₂ H ₅ ) ₆ were dissolved in ethanol C ₂ H ₅ OH dehydrated with molecular sieves, and twice the amount of ethanol was charged. Distill for 2 hours while feeding, then continue for 22 hours
By refluxing for hours, the composite metal alkoxide Li
A 1.2 M solution of Nb (OC ₂ H ₅ ) ₆ was obtained.

After the resulting solution was allowed to cool to room temperature, it was cooled in an ice bath for 1 hour, and while stirring, water was added to the above solution in such an amount that the molar ratio of the composite metal alkoxide to water was 1: 1. 30 water / ethanol solutions mixed with the same amount of ethanol
Dropwise over 3 minutes and then in an ice bath at room temperature for 3 minutes each.
Stirred for 0 minutes. This solution was refluxed at 90 ° C. for 3 hours to obtain a precursor solution.

The obtained precursor solution was washed with a solvent, etched, rinsed, and dried with a sapphire single crystal substrate (α
-Al ₂ O ₃ (0001)). All of the above operations were performed in a nitrogen atmosphere.

The substrate on which the obtained precursor solution was spin-coated was heated at a rate of 20 ° C./s in an oxygen atmosphere and heated at 300 ° C. for 2 hours.
Hold at 20 ° C / s for 30 minutes at 700 ° C.
After holding for 2 minutes, the film was naturally cooled to obtain a thin film of Comparative Example 2 having a thickness of about 80 nm.

X-ray diffraction analysis of the obtained thin film of Comparative Example 2 was performed under the same conditions as in Example 1. As a result, misalignment peaks such as (0112) plane, (1014) plane, and (1120) plane of LiNbO ₃ were obtained. And it was almost in a polycrystalline state. In addition, SEM observation revealed that small grains were present on the surface, and many pores were observed between the grains, indicating that the thin film had much lower surface smoothness than the thin film of Example 1.

Example 2 As in Example 1, equimolar amounts
LiOC_TwoH_FiveAnd Nb (OC_TwoH)₆The molecular
2-methoxyethanol CH dehydrated by sieves_ThreeOC
_TwoH_FourDissolve in OH and add 2-methoxy
Distill for 2 hours while supplying ethanol, then continue for 22 hours
By refluxing, the composite metal alkoxide LiNb
(OC_TwoH _FiveOCH_Three)₆A 1.2 M solution of was obtained.

The resulting solution was allowed to cool to room temperature, and then cooled in an ice bath for 1 hour. While stirring, water was added to the above solution in such an amount that the molar ratio of the composite metal alkoxide to water was 1: 2. A water / 2-methoxyethanol solution mixed with the same amount of 2-methoxyethanol was added dropwise over 30 minutes, followed by stirring in an ice bath at room temperature for 30 minutes each. This solution was refluxed at 90 ° C. for 3 hours to obtain a precursor solution.

The obtained precursor solution was washed with a solvent, etched, rinsed, and dried with a sapphire single crystal substrate (α
-Al ₂ O ₃ (0001)). All of the above operations were performed in a nitrogen atmosphere.

The substrate on which the obtained precursor solution was spin-coated was heated at a rate of 20 ° C./s in an oxygen atmosphere and heated at 300 ° C. for 2 hours.
Hold at 20 ° C / s for 30 minutes at 700 ° C.
After holding for about 1 minute, the film was allowed to cool naturally to obtain a thin film of Example 2 having a thickness of about 80 nm.

The thin film of Example 2 obtained by X-ray diffraction analysis showed almost no misorientation peak, and
The strength of the 0006 face of No. ₃ was 30 kcps. Also,
When SEM observation was performed, it had a smooth and dense surface without cracks, and the refractive index was 2.24, which was a large value similar to that of a single crystal.

Comparative Example 3 In the same manner as in Example 2, equimolar amounts of LiOC ₂ H ₅ and Nb (OC ₂ H ₅ ) ₆ were dehydrated with molecular sieves to form 2-methoxyethanol CH ₃ O.
The mixed metal alkoxide LiN was dissolved in C ₂ H ₄ OH and distilled for 2 hours while supplying 2-methoxyethanol twice as much as the charge, followed by refluxing for 22 hours.
A 1.2 M solution of b (OC ₂ H ₅ OCH ₃ ) ₆ was obtained.

After the resulting solution was allowed to cool to room temperature, it was cooled in an ice bath for 1 hour, and while stirring, water was added in an amount such that the molar ratio of the composite metal alkoxide to water was 1: 2.5. Water / 2-mixed with the same amount of 2-methoxyethanol as solution
A methoxyethanol solution was added dropwise over 30 minutes, followed by stirring in an ice bath at room temperature for 30 minutes each. This solution was refluxed at 90 ° C. for 3 hours to obtain a precursor solution.

The obtained precursor solution was washed with a solvent, etched, rinsed, and dried with a sapphire single crystal substrate (α
-Al ₂ O ₃ (0001)). All of the above operations were performed in a nitrogen atmosphere. The substrate spin-coated with the precursor solution was placed at 20 ° C. in an oxygen atmosphere.
/ S, hold at 300 ° C for 2 minutes,
After heating at s and holding at 700 ° C. for 30 minutes, the film was naturally cooled to obtain a thin film of Comparative Example 3 having a film thickness of about 80 nm.

When the X-ray diffraction analysis of the obtained thin film of Comparative Example 3 was performed under the same conditions as in Example 2, the misalignment peaks of LiNbO _{3 such as} the (0112) plane, (1014) plane and (1120) plane were obtained. And the intensity of the diffraction peak on the (0006) plane was 25 kcps, which was smaller than that of the thin film of Example 2. Also, in SEM observation, small grains are seen on the surface, pores and cracks have been generated,
It was found that the thin film had a significantly lower surface smoothness than the thin film of Example 2.

Example 3 LiOC ₂ H ₅ and Nb (OC
The ₂ H _{5) 6} and _{Ta (OC 2 H 5) 6} 1: 0.5: 0.
It was dissolved in molecular sieves-dehydrated 2-methoxyethanol CH ₃ OC ₂ H ₄ OH to give a molar ratio of 5 and distilled for 2 hours while supplying 2-methoxyethanol twice as much as the charge. By refluxing for 22 hours, the composite metal alkoxide LiNb _0.5 Ta _0.5
A 1.2 M solution of (OC ₂ H ₅ OCH ₃ ) ₆ was obtained.

After the resulting solution was allowed to cool to room temperature, it was cooled in an ice bath for one hour, and while stirring, water was added in an amount such that the molar ratio of the composite metal alkoxide to water was 1: 1.5. Water / 2-mixed with the same amount of 2-methoxyethanol as solution
A methoxyethanol solution was added dropwise over 30 minutes, followed by stirring in an ice bath at room temperature for 30 minutes each. This solution was refluxed at 90 ° C. for 3 hours to obtain a precursor solution.

The obtained precursor solution was washed with a solvent, etched, rinsed, and dried with a sapphire single crystal substrate (α
-Al ₂ O ₃ (0001)). All of the above operations were performed in a nitrogen atmosphere.

The substrate on which the obtained precursor solution was spin-coated was heated at 100 ° C./s in an oxygen atmosphere, kept at 300 ° C. for 2 minutes, and further heated at 20 ° C./s to 750 ° C. for 3 minutes.
After holding for 0 minutes, the film was allowed to cool naturally to obtain a thin film of Example 3 having a thickness of about 80 nm.

According to X-ray diffraction analysis, the obtained thin film of Example 3 showed almost no misorientation peak,
The strength of the (0006) plane of _0.5 Ta _0.5 O ₃ is 30 kcp.
s. In addition, SEM observation revealed that the surface had no cracks, had a smooth and dense surface, and had a refractive index of 2.
The value was as large as 20 as a single crystal.

(Example 4) LiOC ₂ H ₅ was obtained by stirring granular metal Li in ethanol. Nb (OC ₂ H) _{6 in an} equimolar amount to the obtained LiOC ₂ H ₅
Was mixed with 2-methoxyethanol CH ₃ OC ₂ H ₄ OH dehydrated with molecular sieves and stirred.
Distillation was carried out for 6 hours while supplying 2-methoxyethanol six times as much as the charge, followed by refluxing for 24 hours to obtain a composite metal alkoxide LiNb (OC ₂ H ₅ OCH).
₃ ) A 1.2 M solution of ₆ was obtained.

After the resulting solution was allowed to cool to room temperature, it was cooled in an ice bath for one hour, and while stirring, water was added in such an amount that the molar ratio of the composite metal alkoxide to water became 1: 1.5. Water-2-mixed with the same amount of 2-methoxyethanol as the solution
A methoxyethanol solution was added dropwise over 30 minutes, followed by stirring in an ice bath at room temperature for 30 minutes each. This solution was refluxed at 90 ° C. for 3 hours to obtain a precursor solution.

The obtained precursor solution was washed with a solvent, etched, rinsed, and dried with a sapphire single crystal substrate (α
-Al ₂ O ₃ (0001)). All of the above operations were performed in a nitrogen atmosphere.

The substrate on which the obtained precursor solution was spin-coated was heated at a rate of 20 ° C./s in an oxygen atmosphere and heated at 300 ° C. for 2 hours.
Hold at 20 ° C / s for 30 minutes at 700 ° C.
After holding for about 1 minute, the film was allowed to cool naturally to obtain a thin film of Example 4 having a thickness of about 80 nm.

According to the X-ray diffraction analysis, the obtained thin film of Example 4 showed almost no misorientation peak,
The strength of the (0006) plane of No. ₃ was 30 kcps. Further, SEM observation revealed that the surface had a smooth and dense surface without cracks, and that the refractive index was 2.20, a value as large as that of a single crystal.

Example 5 NbCl ₅ and ethanol C ₂
H ₅ OH was stirred in benzene while passing ammonia, and the white precipitate of ammonium chloride NH ₄ Cl was filtered, the solvent was removed by distillation under reduced pressure, and Nb (OC
It was obtained ₂ H _{5) 5.} 2-ethoxyethanol C ₂ H ₅ OC ₂ H ₄ O obtained by dehydrating LiOC ₂ H ₅ in an equimolar amount with the obtained Nb (OC ₂ H ₅ ) ₅ by molecular sieves
H, and distilled while supplying 2-ethoxyethanol twice as much as the charge, followed by refluxing for 22 hours to obtain a composite metal alkoxide LiNb (OC ₂ H ₅ O
To give a 1.2M solution of C ₂ H _{5) 6.}

The resulting solution was allowed to cool to room temperature, and then cooled in an ice bath for 1 hour. Then, while stirring, water was added in an amount such that the molar ratio of the composite metal alkoxide to water was 1: 1.5. Water / 2-mixed with the same amount of 2-methoxyethanol as solution
A methoxyethanol solution was added dropwise over 30 minutes, followed by stirring in an ice bath at room temperature for 30 minutes each. This solution was refluxed at 90 ° C. for 3 hours to obtain a precursor solution.

The obtained precursor solution was washed with a solvent, etched, rinsed, and dried with a sapphire single crystal substrate (α
-Al ₂ O ₃ (0001)). All of the above operations were performed in a nitrogen atmosphere.

The substrate on which the obtained precursor solution was spin-coated was heated at 10 ° C./s in an oxygen atmosphere, and heated at 350 ° C. for 1 hour.
The temperature is further increased at 20 ° C./s for 90 minutes at 650 ° C.
After holding for about 1 minute, the mixture was allowed to cool naturally to obtain a thin film of Example 5 having a thickness of about 80 nm.

The thin film of Example 5 obtained by X-ray diffraction analysis showed almost no misorientation peak, and
The strength of the (0006) plane of No. ₃ was 30 kcps. In addition, SEM observation revealed that it had a smooth and dense surface without cracks, and had a refractive index of 2.19, a value as large as that of a single crystal.

Example 6 LiCl and ethanol C ₂ H
Stir ₅ OH while passing ammonia in benzene,
After filtering the white precipitate of ammonium chloride NH ₄ Cl,
The solvent was removed by distillation under reduced pressure to obtain LiOC ₂ H ₅ . Similarly, from TaCl ₅ to Ta (OC ₂ H ₅ ) ₅
I got The obtained LiOC ₂ H ₅ and Ta (OC
₂ H _{5) 5} equimolar amounts each, 2-ethoxyethanol and dried over molecular sieves _{C 2 H 5 OC 2 H 4} O
H, and the mixture was distilled while supplying 2-ethoxyethanol twice as much as the charged one, and then refluxed for 22 hours to obtain a composite metal alkoxide LiTa (OC ₂ H ₅ O
To give a 1.2M solution of C ₂ H _{5) 6.}

The resulting solution was allowed to cool to room temperature, and then cooled in an ice bath for 1 hour. Then, while stirring, water was added in such an amount that the molar ratio of the composite metal alkoxide to water was 1: 1.5. Water / 2-mixed with 2-ethoxyethanol in the same amount as the solution
The ethoxyethanol solution was added dropwise over 30 minutes, followed by stirring in an ice bath at room temperature for 30 minutes each. This solution was refluxed at 90 ° C. for 3 hours to obtain a precursor solution.

The obtained precursor solution was washed with a solvent, etched, rinsed, and dried with a sapphire single crystal substrate (α
-Al ₂ O ₃ (0001)). All of the above operations were performed in a nitrogen atmosphere.

The substrate on which the obtained precursor solution was spin-coated was heated at a rate of 20 ° C./s in an oxygen atmosphere and heated at 300 ° C. for 2 hours.
Hold at 20 ° C / s for 30 minutes at 700 ° C.
After holding for about 1 minute, the film was allowed to cool naturally to obtain a thin film of Example 6 having a thickness of about 80 nm.

According to the X-ray diffraction analysis, the obtained thin film of Example 6 showed almost no misorientation peak, and the LiTaO
The strength of the (0006) plane of No. ₃ was 30 kcps. In addition, SEM observation revealed that it had a smooth and dense surface without cracks, and had a refractive index of 2.18, which is a large value comparable to that of a single crystal.

[0112]

As described above, the present invention can provide a single-crystal ferroelectric thin film whose composition is controlled stably, which is dense and has good surface properties and crystallinity, and a method for producing the same.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02B 6/12 G02B 6/12 M G02F 1/03 501 N (72) Inventor Keiichi Nashimoto Nakaicho, Ashigarakami-gun, Kanagawa Sakai 430 Green Tech Naka Fuji Xerox Co., Ltd. F-term (reference) 2H047 QA03 RA08 2H079 AA02 AA12 AA13 AA14 CA05 CA24 DA03 HA12 HA16 4G077 AA03 BC32 BC37 CB08 ED06 5G303 AA10 AB20 BA03 CA01 CB16 CB21 CB33 DA02

Claims (16)

[Claims] 1. An organic ligand comprising a Li element and at least one of Nb and Ta, wherein the organic ligand has the formula: R ¹ OR ²
O- (wherein R ¹ represents an aliphatic hydrocarbon group, and R ² represents a divalent aliphatic hydrocarbon group which may have an ether bond) in an organic solvent solution of a composite metal alkoxide represented by the formula: The molar ratio of the composite metal alkoxide to water is 1: 1 to 1
A hydrolysis step of partially hydrolyzing by adding water in an amount of 1: 2, a coating step of coating the precursor solution obtained in the hydrolysis step on a single crystal substrate, and a heat treatment step. A ferroelectric thin film characterized by the following. 2. An organic solvent solution of a composite metal alkoxide comprising, as starting materials, an organometallic compound or an inorganic compound containing a Li element and at least one of an organometallic compound or an inorganic compound containing an Nb or Ta element, :
R ¹ OR ² OH (wherein R ¹ represents an aliphatic hydrocarbon group,
R ² represents a divalent aliphatic hydrocarbon group which may have an ether bond. 2. The method according to claim 1, wherein the solution is prepared by a dissolving step of dissolving in alcohol shown in the above step, a distillation step of heating and distilling the solution obtained in the dissolving step while further replenishing the alcohol, and a refluxing step. 3. The ferroelectric thin film according to 1. 3. The ferroelectric thin film according to claim 1, wherein the hydrolysis time is 1 to 10 hours. 4. The single crystal substrate is made of Al ₂ O ₃ or LiTa.
O _3, MgO, or a ferroelectric thin film according to claim 1 which is ZnO. 5. An amorphous heating step in which the heat treatment is performed by thermally decomposing the applied thin film to be amorphous at a temperature range of 100 ° C. to 500 ° C., and at a temperature range of 300 ° C. to 1200 ° C.
2. The ferroelectric thin film according to claim 1, comprising at least an epitaxial heating step for realizing solid phase epitaxial growth. 6. The heating rate of the heat treatment is 1 to 500 ° C./s.
3. The ferroelectric thin film according to claim 1, wherein the ferroelectric thin film is ec. 7. An organic ligand comprising a Li element and at least one element of Nb and Ta, wherein the organic ligand has the formula: R ¹ OR ²
O- (wherein R ¹ represents an aliphatic hydrocarbon group, and R ² represents a divalent aliphatic hydrocarbon group which may have an ether bond) in an organic solvent solution of a composite metal alkoxide represented by the formula: The molar ratio of the composite metal alkoxide to water is 1: 1 to 1
A hydrolysis step of partially hydrolyzing by adding water in an amount of 1: 2, a coating step of coating the precursor solution obtained in the hydrolysis step on a single crystal substrate, and a heat treatment step. A method for producing a ferroelectric thin film, which is characterized in that: 8. The composite metal alkoxide organic solvent solution,
As a starting material, an organometallic compound or an inorganic compound containing a Li element and at least one of an organometallic compound or an inorganic compound containing an Nb or Ta element are represented by the formula: R ¹
OR ² OH (wherein R ¹ represents an aliphatic hydrocarbon group, R ²
Represents a divalent aliphatic hydrocarbon group which may have an ether bond. 8. The method according to claim 7, wherein the solution is prepared by a dissolving step of dissolving in alcohol shown in the above), a distillation step of heating and distilling the solution obtained in the dissolving step while further supplementing the alcohol, and a refluxing step. 3. The method for producing a ferroelectric thin film according to item 1. 9. At least one of the starting materials is Li, N
The method for producing a ferroelectric thin film according to claim 8, wherein the ferroelectric thin film is an alkoxide of b or Ta. 10. The method according to claim 1, wherein at least one of the starting materials is Li,
The method for producing a ferroelectric thin film according to claim 8, wherein the ferroelectric thin film is a halide of Nb or Ta. 11. The method according to claim 1, wherein at least one of the starting materials is a metal L
The method for producing a ferroelectric thin film according to claim 8, wherein i is i. 12. The method for producing a ferroelectric thin film according to claim 8, wherein in the distillation step, 0.1 to 100 times the volume of the alcohol used in the dissolving step is further supplied. 13. The method according to claim 7, wherein the hydrolysis time is 1 to 10 hours. 14. The single crystal substrate is made of Al ₂ O ₃ or LiTaO.
_The method for producing a ferroelectric thin film according to claim 7, wherein the ferroelectric thin film is made of ₃ , MgO, or ZnO. 15. A heat treatment comprising: an amorphous heating step in which the applied thin film is thermally decomposed into amorphous at a temperature range of 100 ° C. to 500 ° C .; and a solid phase epitaxial growth at a temperature range of 300 ° C. to 1200 ° C. The method for producing a ferroelectric thin film according to claim 7, comprising at least an epitaxial heating step to be realized. 16. The heating rate of the heat treatment is 1 to 500 ° C. /
The method for producing a ferroelectric thin film according to claim 7, wherein the time is set to sec.