JP4704077B2 - Precursor solution, method for producing oxide thin film, and ferroelectric optical element - Google Patents

Description

  The present invention relates to a precursor solution for forming an oxide thin film, a method for producing an oxide thin film using the precursor solution, and a ferroelectric optical element.

Ferroelectric thin film, one of oxide thin films, has many functions such as spontaneous polarization, high dielectric constant, electro-optic effect, piezoelectric effect, and pyroelectric effect, so it is expected to be applied to a wide range of devices. Has been. Among these extensive developments, with the progress of thin film formation technology in recent years, development of nonvolatile ferroelectric memories that operate at high density and at high speed has been progressing in combination with semiconductor elements. Non-volatile memories using ferroelectric thin films are not only used for replacing conventional non-volatile memories but also for SRAMs and DRAMs because of their high-speed writing / reading, low-voltage operation, and high writing / reading resistance. Research and development is actively conducted as a memory that can be replaced. In addition, for example, an infrared linear array sensor using the pyroelectric property, an ultrasonic sensor using the piezoelectric property, a waveguide type optical modulator using the electro-optic effect, Utilizing its high dielectric properties, it is used in various fields such as DRAM.
However, ferroelectrics are required to have a large remanent polarization and a small coercive electric field, and research and development of relaxor-type ferroelectric materials having a large dielectric constant and the like among the ferroelectric materials has become active. Since these have a large piezoelectric effect, research and development for use as an ultrasonic vibrator or actuator element and as a material for a large-capacitance capacitor because of a very large dielectric constant and a small temperature change are in progress. Also, with the spread of optical communication technology, in order to cope with an increase in the amount of transmission information, an optical switch that switches an optical signal is required, and it is transparent and has high optical transparency. Research is being conducted to use it as an optical switch that can be switched at high speed.

On the other hand, the ferroelectric thin film can be produced by physical methods such as vacuum deposition, sputtering, and laser ablation, and by using organic metal compounds as starting materials and thermally decomposing them to produce oxide ferroelectrics. A chemical method using a solution such as a sol-gel method, an MOD method, or an MOCVD method is used.
The MOCVD method is promising for high integration of ferroelectric elements because it has excellent coverage to a stepped portion and can be formed at a low temperature, and recently research and development have been actively conducted. In the sol-gel method and the MOD method, since a raw material solution capable of homogeneous mixing at the atomic level can be used, composition control is easy, and a large-area film can be formed at normal pressure without the need for a special vacuum apparatus. Therefore, it is possible to reduce the manufacturing cost. These solution methods have an advantage that a crystallization treatment is required after coating, and a multi-component oxide can be uniformly coated over a wide area with a desired composition. However, depending on the solvent, there are problems such as generation of cracks and white turbidity in the film after spin coating or baking.

Patent Document 1 includes a step of forming a ferroelectric film by crystallizing a ferroelectric raw material liquid containing a first raw material liquid and a second raw material liquid, and the first raw material liquid And the second raw material liquid are of different types, and the first raw material liquid is a raw material liquid for producing a ferroelectric having a Bi-based layered perovskite structure, and the second raw material liquid As the liquid, a raw material liquid for producing an ABO ₃ oxide whose A site is Pb is disclosed. These raw material liquids are mixed with metal alkoxide in 2-methoxyethanol. However, the 2-methoxyethanol solvent alone has a problem that crack resistance is particularly poor when a film thickness of 100 nm or more per layer is formed.
Patent Document 2 discloses a dielectric layer patterning method in which a dielectric layer formed by a solution coating firing method is calcined at a temperature at which it does not crystallize, then patterned, and then fired to form a dielectric layer. As an organic film forming aid, 1,3-propanediol and the like are mentioned. However, it has not been studied to use it in an appropriate range as a solvent to be added in combination with the main solvent. Patent Document 3 discloses a composition for forming a ferroelectric thin film that includes a PZT sol-gel solution and a Bi ₂ SiO ₅ sol-gel solution and, in addition, a reflux product between C1-C10 alkoxy alcohols. However, these are insufficient to prevent the ferroelectric film from cracking during production and to obtain an oxide thin film having high light transmittance.

JP 2004-319995 A JP 2003-323981 A JP 2004-363083 A

Therefore, the present invention has been made in view of the above problems, and its object is to provide a precursor solution capable of obtaining an optically transparent thin film without precipitation of metal alkoxide or the like during production. It is.
Another object of the present invention is to provide a method for producing an oxide thin film which is less prone to cracks and cloudiness during the heat treatment during the production of the oxide thin film. Furthermore, it is to provide a ferroelectric optical element using these precursor solutions.

The features of the present invention, which is a means for solving the above problems, are listed below.
The present invention relates to a relaxor-type perovskite oxide represented by PbBO ₃ (where B represents a +2 metal and B ″ represents a +5 metal), and includes a sol-gel method, MOD An additive solvent having a boiling point of 200 ° C. or more is added to a main solvent of 2-ethoxyethanol to a precursor solution used in a solution method such as a method, in particular, 1,3-propanediol.
Moreover, this invention is a manufacturing method which manufactures an oxide thin film by apply | coating with the application | coating methods, such as spin coating, using this precursor solution, and heat-processing. Furthermore, it is a ferroelectric optical element such as an optical deflection element that can be manufactured using this precursor solution.

By the means for solving the above, in the precursor solution of the present invention, the evaporation of the solvent is small, and the fluctuation of the production conditions during the production can be reduced. Furthermore, it is possible to prevent white turbidity at the time of coating and to prevent cracks during heat treatment to form an oxide thin film.
Further, in the method for producing an oxide thin film of the present invention, it is possible to prevent white turbidity at the time of coating, and to prevent cracking of the oxide thin film during heat treatment for thin film formation by appropriately evaporating at the time of coating. it can.
In addition, the ferroelectric optical element of the present invention uses a relaxor-type ferroelectric thin film having a high dielectric constant and a large piezoelectric constant, so that it can be applied to an optical deflecting element having a high light transmittance and a high refractive index. A dielectric optical element can be provided.

  The best mode for carrying out the present invention will be described below. Note that it is easy for a person skilled in the art to make other embodiments by changing or correcting the present invention within the scope of the claims, and these changes and modifications are included in the scope of the claims.

The precursor solution of the present invention contains Pb (B ′ _1/3 , B ″ _2/3 ) O ₃ type relaxor type perovskite oxide (where B ′ is a +2 valent metal, B ″ is a +5 valent metal). Used to manufacture.
Relaxor-type perovskite oxide is a ferroelectric substance, and is expressed as ABO ₃ as a general formula. A relaxor-type ferroelectric substance has a high dielectric constant, a low dielectric loss, and a very large piezoelectric constant. As the relaxor-type ferroelectrics, many of A are Pb-based, and Sr _1-1.5x Bi _x O ₃ , Sr _1-x Ca _x O ₃ , KTa _1-x Nb _x O ₃ , K There are Sr and K systems such as _1-x Li _x TaO ₃ . In particular, in the Pb system, it is sufficient that two types of ions having a charge of +4 on average enter the site containing B ′ and B ″ in the crystal, and the ions of +2 and +5 are 1: 2. There are a type that enters in a ratio and a type in which +3 and +5 or +2 and +6 valent ions enter at a ratio of 1: 1, specifically, Pb (Mg _1/3 , Nb _2/3 ) O ₃ (PMN), Pb (Zn _1/3 , Nb _2/3 ) O ₃ (PZN), Pb (Sc _1/2 , Nb _1/2 ) O ₃ (PSN), Pb (Sc _1/2 , Ta _{1 / 2} ) O ₃ (PST), Pb (Zr, Ti) O ₃ (PZT), (Pb, La) (Zr, Ti) O ₃ (PLZT), etc., among which +2 and +5 The Pb (B ′ _1/3 , B ″ _2/3 ) O ₃ type into which valence ions enter has a large dielectric constant and piezoelectric constant.
These ferroelectric are often relaxor properties it appears by forming a PbTiO ₃ and mixed crystals, used as the ferroelectric material be to PbTiO ₃ and mixed crystals.

Examples of a solution method that is a method for producing an oxide thin film using a precursor solution include a sol-gel method and a MOD method. In either case, a predetermined precursor solution is applied to form a thin film, which is heat-treated to evaporate the solvent and form an oxide thin film having a perovskite structure. The sol-gel method uses an alcohol solution of a plurality of metal alkoxides so as to have a desired composition, and adds a suitable amount of water to this to hydrolyze or polycondensate a M-O-M bond sol. The precursor solution is formed by standing at an appropriate temperature for a period of time. In the MOD method, a metal salt such as a carboxylic acid having an MO bond is dissolved in an organic solvent to form a precursor solution. This precursor solution can be applied in a uniform thickness by spin coating, dip coating, spray coating or the like in order to apply the precursor solution to the entire surface of the substrate. After application, heat treatment is performed. The heat treatment is preferably performed in two stages of calcination and main firing. Calcination is performed at 350 ° C. to 500 ° C. to evaporate the solvent, H ₂ O, and the like. The temperature at the time of calcination is preferably 350 ° C. or higher, in which most of the organic solvent component in the dried gelled film is decomposed and reduced. However, cracks are likely to occur when the temperature exceeds 500 ° C. Next, in the main firing, a perovskite ferroelectric phase can be sufficiently formed at about 600 ° C. to 800 ° C. In the case of a ferroelectric including lead oxide and titanium oxide as constituent elements, the firing temperature is 800 ° C. or less because the characteristics of the ferroelectric film are likely to deteriorate due to volatilization of the lead component at a high temperature.

  Moreover, the precursor solution used for the manufacturing method of an oxide thin film uses the solvent whose boiling point of the solvent added is 200 degreeC or more to 2-methoxyethanol of a main solvent. Conventionally, PMN-PT and PMN-PZ-PT precursor solutions of a solvent using butanol as a solvent to be added to 2-methoxyethanol as a main solvent have a reaction product or metal salt of a metal alkoxide during spin coating. Precipitation is likely to occur, and therefore the precursor solution becomes cloudy, making it difficult to obtain a transparent thin film necessary for an optical switch. In addition, extremely large volume shrinkage occurs in the process from the solution state immediately after applying the precursor solution on the substrate to the oxide solid state after firing, so that cracks and peeling occur in the film during drying and firing. . For example, in the PLZT precursor, the occurrence of cracks can be prevented by using 2,4-pentanedione which is a chelating agent. However, even if 2,4-pentanedione is contained in the PMN-PT and PMN-PZ-PT precursor solutions, the generation of cracks cannot be suppressed.

In order to form this Pb (B ′ _1/3 , B ″ _2/3 ) O ₃ type oxide, the main solvent 2-methoxyethanol is heated to 200 ° C. or higher, which is higher than the boiling point 140 ° C. of 2,4-pentanedione. First, this precursor solution is prepared by combining lead acetate trihydrate, magnesium ethoxide or magnesium acetate, niobium ethoxide, i-propoxy titanium and a solvent. contains.
The main solvent includes a hydrocarbon solvent, an alcohol solvent, an ester solvent, and an ether solvent. In particular, the organic solvent is preferably an alcohol ether solvent among ether solvents, such as 2-methoxyethanol, 2-ethoxyethanol, 1-ethoxy-2-propanol, and the like. The boiling point of the main solvent is preferably 100 ° C. or higher, and 2-methoxyethanol is particularly preferable. As a result, evaporation of the main solvent can be prevented and fluctuations in the production conditions of the precursor solution can be prevented.
In addition, a solvent having a boiling point of 200 ° C. or higher is added to this main solvent. When the boiling point exceeds 200 ° C., the amount of evaporation is small, and fluctuations in the production conditions of the precursor solution can be prevented. However, it is preferably at least below 300 ° C. If it exceeds 300 ° C., the viscosity of the solvent becomes high and it is not suitable for producing a thin film. In addition, the heat treatment temperature at the time of production is increased, the time is increased, and the productivity is lowered. Examples thereof include glycols such as 1,3-propanediol, 1,4-butanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, and 2,2,4-trimethyl-pentanediol. It is done. Among these, 1,3-propanediol is particularly preferable.
Further, as a solvent, the ratio of the main solvent and the added solvent is in the range of 1/99 to 60/40 in 2-methoxyethanol / 1,3-propanediol. Preferably, it is in the range of 1/99 to 50/50. When 1,3-propanediol exceeds 60/40, it is difficult to evaporate during coating. For example, in spin coating, the film thicknesses at the center and the periphery of the substrate are greatly different. If it is less than 1/99, clouding and generation of cracks cannot be prevented.

According to the method for producing an oxide thin film of the present invention, a Pb (Mg _1/3 , Nb _2/3 ) O ₃ —PbTiO ₃ oxide thin film is produced, and a ferroelectric optical element including the oxide thin film is obtained. it can.
FIG. 1 is a flowchart showing one embodiment of a method for producing an oxide thin film of the present invention.
First, lead acetate hydrate, magnesium ethoxide, niobium ethoxide, and titanium-i propoxide are used as starting materials.
First, lead acetate hydrate is dehydrated under reduced pressure at 120 ° C. for 3 hours (step S1). 2-methoxyethanol is added, and after refluxing and distillation treatment at 125 ° C. for 3 hours under a nitrogen atmosphere, a lead precursor is obtained (step S2).
To this, a certain amount of magnesium ethoxide, niobium ethoxide, titanium-i propoxide and 2-methoxyethanol are added and mixed, followed by refluxing and distillation treatment at 125 ° C. for 3 hours (step S3). At this time, lead is added in an amount 10 to 20% higher than the stoichiometric composition in consideration of the amount evaporated by heat treatment or the like.
After adjusting the concentration of this precursor by distillation, 1,3-propanediol was added and refluxed for 3 hours to obtain a PMN-PT sol-gel precursor solution (step S4). At this time, a solvent having a composition of 2-methoxyethanol / 1,3-propanediol = 75/25 was added to 0.6 mol / L of PMN-0.33PT.
This precursor solution was coated at a rotation speed of 3000 rpm in a spin coating apparatus provided with a substrate (step S5), calcined at 150 to 300 ° C. (step S6), and this was repeated a plurality of times (step S7). .
Next, a main firing was performed at 600 to 800 ° C. to produce a PMN-PT oxide thin film with a thickness of about 100 to 120 nm (step S8).
The method for producing the Pb (Ni _1/3 , Nb _2/3 ) O ₃ —PbZrO ₃ —PbTiO ₃ (PNN—PZ—PT) oxide thin film is the same as described above. The raw materials are lead acetate, nickel acetate, niobium ethoxide, titanium-i propoxide, zirconium propoxide and 2-methoxyethanol. A PNN-PZ-PT oxide thin film having a thickness of about 100 to 120 nm was produced by a sol-gel method.

The precursor solution or oxide thin film production method of the present invention is suitable for relaxer-type perovskite oxide Pb (Mg _1/3 , Nb _2/3 ) O ₃ -PbTiO ₃ (PMN-PT). The relaxivity of a ferroelectric material is manifested by the presence of a mixed crystal with PbTiO ₃ (PT), and in particular, the dielectric constant is an MPB composition which is a boundary region between a tetragonal system and a rhombohedral system. Therefore, the electro-optic constant such as the optical refractive index can be increased. In order to form this oxide thin film, the precursor solution contains Mg and Nb in the form of a metal salt or a metal alkoxide. By using this precursor solution for coating, a relaxer-type perovskite oxide can be produced.
Further, the relaxer-type perovskite oxide may be Pb (Ni _1/3 , Nb _2/3 ) O ₃ —PbZrO ₃ —PbTiO ₃ (PNN—PZ—PT). PbTiO ₃ is further mixed with PbZrO ₃ and further mixed with Pb (Ni _1/3 , Nb _2/3 ) O ₃ . The dielectric constant is very large in the MPB composition, which is the boundary region between the tetragonal system and the trigonal system, and therefore the electro-optic constant such as the photorefractive index can be increased. In order to form this oxide thin film, the precursor solution contains Ni and Nb in the form of a metal salt or a metal alkoxide. By using this precursor solution for coating, a relaxer-type perovskite oxide can be produced.

Also, an optical deflection element, which is an example of a ferroelectric optical element, will be described.
FIG. 2 is a schematic diagram showing the configuration of the optical deflection element.
First, a PLZT (9/65/35) sol-gel precursor is applied on an Nb1% -doped SrTiO ₃ substrate 11 having a (100) plane as a main surface, and then on a hot plate, for example, at 180 ° C. for 5 minutes. Next, after baking at 400 ° C. for 5 minutes, the PLZT cladding layer 12 having a thickness of, for example, 3 μm is formed by baking at 700 ° C. in an oxygen atmosphere. In this case, as a sol-gel raw material solution for PLZT, lead acetate, lanthanum isopropoxide, titanium isopropoxide, zirconium propoxide, which is an organic compound of constituent metal elements, is added as a solvent 1,3-propanediol Was refluxed with 2-methoxyethanol as a solvent. Next, the PMN-PT sol-gel precursor solution is applied in the same manner to form the PMN-PT core layer 13 having a thickness of, for example, 4 μm.
Next, the PLZT sol-gel precursor is applied again by the same method to form the PLZT clad layer 14 having a thickness of, for example, 3 μm.
In this case, the refractive index n of the PLZT cladding layers 12 and 14 is n = 2.36 with respect to the wavelength of 1.55 μm, and the refractive index n of the PMN-PT core layer 13 is with respect to the wavelength of 1.55 μm. Since n = 2.43, the slab type optical waveguide 15 is formed.
Next, an optical waveguide device provided with the deflection electrode 16 is obtained by forming the deflection electrode 16 on the upper PLZT cladding layer 14 by depositing an ITO film in a triangular mask. Therefore, in the embodiment of the present invention, it is possible to realize an optical waveguide element with a small waveform transmission round and a large electro-optic effect, thereby enabling a high-speed optical polarization element or a high-speed optical switch module to be realized. It can be downsized.

The above is the description according to the embodiment of the present invention. As the invention, for example, the following features can be extracted, and are listed here.
(Supplementary note 1) The precursor solution of the present invention is Pb (B ′ _1/3 , B ″ _2/3 ) O ₃ type relaxor type perovskite oxide (where B ′ is a divalent metal, B ″ is 5 In the precursor solution for producing an oxide thin film containing a valent metal, the main solvent 2-methoxyethanol contains a solvent having a boiling point of 200 ° C. or higher.
(Additional remark 2) The precursor solution of this invention is the additional remark 1, The said 200 degreeC or more solvent is 1, 3- propanediol, It is characterized by the above-mentioned.
(Supplementary Note 3) The precursor solution of the present invention is characterized in that, in Supplementary Note 2, the content ratio of 2-methoxyethanol / 1,3-propanediol is 1/99 to 60/40.
(Appendix 4) The precursor solution of the present invention is the appendix 1, 2 or 3, wherein the relaxor-type perovskite oxide is Pb (Mg _1/3 , Nb _2/3 ) O ₃ —PbZrO ₃ —PbTiO _3. The precursor solution contains a metal salt of Mg and Nb and / or a metal alkoxide.
(Supplementary Note 5) The precursor solution of the present invention is the supplementary note 1, 2 or 3, wherein the relaxor type perovskite oxide is Pb (Ni _1/3 , Nb _2/3 ) O ₃ —PbZrO ₃ —PbTiO _3. The precursor solution contains a metal salt of Ni and Nb and / or a metal alkoxide.

Method of manufacturing an oxide thin film (Note 6) The present _{invention, Pb (B '1/3, B} "2/3) O 3 type relaxor type perovskite oxide (wherein, B' is bivalent metal, B In the method for producing an oxide thin film containing ″ represents a pentavalent metal.), A precursor solution containing a solvent having a boiling point of 200 ° C. or higher is applied to 2-methoxyethanol as a main solvent on a substrate. An oxide thin film is manufactured by heat treatment.
(Additional remark 7) The manufacturing method of the oxide thin film of this invention is the additional remark 6, The said 200 degreeC or more solvent is 1, 3- propanediol, It is characterized by the above-mentioned.
(Additional remark 8) The manufacturing method of the oxide thin film of this invention WHEREIN: The content ratio with 2-methoxyethanol / 1,3-propanediol in Additional remark 7 is 1 / 99-60 / 40, It is characterized by the above-mentioned. .
(Supplementary note 9) The method for producing an oxide thin film of the present invention is the same as that in Supplementary note 8, using a precursor solution containing a metal salt of Mg and Nb and / or a metal alkoxide, Pb (Mg _1/3 , Nb _{2 / 3} ) It is characterized by producing an O ₃ —PbZrO ₃ —PbTiO ₃ oxide thin film.
(Additional remark 10) The manufacturing method of the oxide thin film of this invention is Pb (Ni1 _{/ 3} , Nb2 _/ ) in the additional remark 8 using the precursor solution containing the metal salt and / or metal alkoxide of Ni and Nb. ₃ ) It is characterized by producing an O ₃ —PbZrO ₃ —PbTiO ₃ oxide thin film.
(Additional remark 11) The manufacturing method of the oxide thin film of this invention is characterized by performing heat processing in two steps in Additional remark 9 or 10.

(Supplementary Note 12) The ferroelectric optical element of the present invention is a Pb (B ′ _1/3 , B ″ _2/3 ) O ₃ relaxor perovskite oxide (where B ′ is a divalent metal) on a substrate. , B ″ represents a pentavalent metal.) In a ferroelectric optical element provided with an oxide thin film, a precursor of a main solvent 2-methoxyethanol containing a solvent having a boiling point of 200 ° C. or higher on a substrate. An oxide thin film obtained by applying a body solution and heat-treating is provided.
(Additional remark 13) The ferroelectric optical element of this invention is the additional remark 12 characterized by the said 200 degreeC or more solvent being 1, 3- propanediol.
(Additional remark 14) The ferroelectric optical element of this invention is characterized by the content ratio with 2-methoxyethanol / 1,3-propanediol being 1 / 99-60 / 40 in additional remark 13.
(Additional remark 15) The ferroelectric optical element of this invention is characterized by being comprised by the morphotropic phase boundary (MPB) composition in Additional remark 11.

It is a flowchart figure which shows one Embodiment of the manufacturing method of the oxide thin film of this invention. It is the schematic which shows the structure of an optical deflection | deviation element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical deflection elements 12, 14 Clad layer 13 Core layer 15 Optical waveguide 16 Deflection electrode

Claims (11)

Precursor solution containing Pb (B ′ _1/3 , B ″ _2/3 ) O ₃ type relaxor type perovskite oxide (where B ′ represents a divalent metal and B ″ represents a pentavalent metal). In the method of manufacturing an oxide thin film using
On the SrTiO ₃ substrate having the (100) plane as the main surface ,
Applying a first precursor solution containing (Pb, La) (Zr, Ti) O ₃ (PLZT) and firing to form a first cladding layer;
Next, the second precursor solution containing the relaxer-type perovskite oxide containing Mg or Ni and a metal salt and / or metal alkoxide of Nb is applied to the first cladding layer and repeated calcination a plurality of times. Then, the core layer is formed by main firing,
Next, the first precursor solution is applied onto the core layer and baked to form a second cladding layer. A method of manufacturing an oxide thin film, comprising: The method for producing an oxide thin film according to claim 1,
The second precursor solution has a content ratio of 2-methoxyethanol / 1,3-propanediol as a solvent of 1/99 to 60/40, and
The calcining temperature is 150 ° C to 300 ° C , and the main baking temperature is 600 ° C to 800 ° C. In the method of manufacturing the oxide thin film according to claim 1 or 2,
The method for producing an oxide thin film, wherein the first precursor solution includes an organic compound of a constituent metal element in 2-methoxyethanol / 1,3-propanediol as a solvent. In the method of manufacturing the oxide thin film according to any one of claims 1 to 3,
The relaxer-type perovskite oxide is
A method for producing an oxide thin film characterized by comprising Pb (Mg _1/3 , Nb _2/3 ) O ₃ —PbTiO ₃ and having a morphotropic phase boundary (MPB) composition. In the method of manufacturing the oxide thin film according to any one of claims 1 to 3,
The relaxer-type perovskite oxide is
A method for producing an oxide thin film characterized by comprising Pb (Ni _1/3 , Nb _2/3 ) O ₃ —PbZnO ₃ —PbTiO ₃ and having a morphotropic phase boundary (MPB) composition. Precursor solution containing Pb (B ′ _1/3 , B ″ _2/3 ) O ₃ type relaxor type perovskite oxide (where B ′ represents a divalent metal and B ″ represents a pentavalent metal). In the oxide thin film manufactured using
A SrTiO ₃ substrate having a (100) plane as a main surface;
A first clad layer formed by applying and firing a first precursor solution containing (Pb, La) (Zr, Ti) O ₃ (PLZT) on the substrate;
Formed by applying a second precursor solution containing the relaxer-type perovskite oxide containing Mg or Ni and a metal salt and / or metal alkoxide of Nb to the first cladding layer, calcining, and main firing. Core layer,
An oxide thin film comprising: a second clad layer formed by applying the first precursor solution onto a core layer and firing the same . The oxide thin film according to claim 6,
The second precursor solution has a content ratio of 2-methoxyethanol / 1,3-propanediol as a main solvent of 1/99 to 60/40, and
The calcining temperature is 150 ° C to 300 ° C , and the main firing temperature is 600 ° C to 800 ° C. In the oxide thin film according to claim 6 or 7,
The first precursor solution contains an organic compound of a constituent metal element in 2-methoxyethanol / 1,3-propanediol as a solvent. The oxide thin film according to any one of claims 6 to 8,
The relaxer-type perovskite oxide is
An oxide thin film comprising Pb (Mg _1/3 , Nb _2/3 ) O ₃ —PbTiO ₃ and having a morphotropic phase boundary (MPB) composition. The oxide thin film according to any one of claims 6 to 8,
The relaxer-type perovskite oxide is
An oxide thin film comprising Pb (Ni _1/3 , Nb _2/3 ) O ₃ —PbZnO ₃ —PbTiO ₃ and having a morphotropic phase boundary (MPB) composition. The substrate contains Pb (B ′ _1/3 , B ″ _2/3 ) O ₃ type relaxor type perovskite oxide (where B ′ represents a divalent metal and B ″ represents a pentavalent metal). In a ferroelectric optical element comprising an oxide thin film,
The ferroelectric optical element includes the oxide thin film according to any one of claims 6 to 10. A ferroelectric optical element, comprising:

Images