JP3224905B2 - Composite oxide thin film and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite oxide thin film, and more particularly, to a dielectric, a sensor, an optoelectronic, a magnetic material,
The present invention relates to a composite oxide thin film used for applications such as superconducting materials and a method for producing the same.

[0002]

2. Description of the Related Art Complex oxides such as barium titanate (BaTiO ₃ ) and strontium titanate (SrTiO ₃ ) are made of ferroelectric materials,
Has excellent properties as piezoelectric material, pyroelectric material, etc.
Ultrasonic sensors, capacitors, actuators, pyroelectric infrared sensors, non-volatile memories, and various other devices have been widely used, and applications to fields such as superconducting materials have been attempted.

Conventionally, such a composite oxide thin film is produced by a physical vapor deposition method (PVD method) such as a sputtering method or an ion plating method, and thermal decomposition, oxidation, and reduction of an organic metal gas as a thin film material. ,
Gas phase methods such as chemical vapor deposition (CVD), in which a thin film composition is deposited on a substrate by polymerization or the like to form a thin film, are well known.

[0004] However, the gas phase method has the following problems to be improved. The above physical vapor deposition method (PVD
Method) generally requires the temperature of a substrate such as a substrate to be about 500 ° C. or higher in order to obtain a crystalline film. There is a problem that cracks and peeling are liable to occur in the obtained lead titanate film. In addition, since the evaporation of the deposition material is performed under a low oxygen partial pressure, the resulting composite oxide thin film often has oxygen vacancies, and thus has a problem that characteristics are deteriorated or varied.

Further, for example, barium titanate (Ba)
When a thin film of a composite oxide such as TiO ₃ ) is formed, it is difficult to control the composition of the film to obtain a composite oxide having a target composition because the evaporation rate varies depending on the element. There is a point. There is also a problem that film growth is slow.

In the above chemical vapor deposition method (CVD method), the evaporation temperature of the organic metal is relatively high, and large-scale equipment is required. It is difficult to control, it is not easy to form a film having a target composition, and further, there are problems such as that the raw material is extremely expensive.

[0007] In addition to the above-mentioned gas-phase method, several thin-film forming methods by a liquid-phase method are also known, the main ones being that an organic metal is applied on a substrate, which is baked to form an oxide. Organic metal coating methods such as the sol-gel method for forming thin films, and a method of immersing titanium metal or zirconium metal in a molten salt obtained by melting a barium salt or strontium salt to form a dielectric film (Japanese Patent Publication No. 43-2650), a method of immersing titanium metal in a molten salt (Japanese Patent Publication No. Sho 4)
A method of forming a barium titanate (BaTiO ₃ ) thin film (film) by a chemical conversion treatment in a strongly alkaline aqueous solution of barium (Japanese Patent Application Laid-Open No. 60-116119) is known.

However, these liquid phase methods have the following problems.

First, in the above-mentioned organometallic coating method, in order to make the organic metal applied to the substrate into an oxide film,
In general, it is necessary to bake at a high temperature of about 500 ° C. or more, large shrinkage occurs during the drying and baking steps, cracks and peeling are likely to occur in the film, and evaporating and burning of organic components during the baking step, There are problems such as difficulty in obtaining a film. Further, there is a problem that an unintended reaction between the substrate and the composite oxide thin film may progress in the firing step, and a composite oxide thin film having a target composition may not be obtained.

In the above method using a molten salt, it is usually necessary to melt the inorganic salt at a high temperature of about 700 ° C. or higher. Therefore, it is necessary to use a reaction vessel made of a low-cost and expensive material, which raises a problem that the cost is increased. Further, even if such a reaction vessel is used, it is difficult to completely prevent the reaction, so that contamination is difficult. There is a problem that nation cannot be avoided.

[0011] In the above chemical conversion treatment method,
There are problems that the growth rate of the film is slow and that the control of the film thickness is difficult.

Further, as a method of solving the problems of the conventional method and producing a composite oxide thin film having excellent uniformity and crystallinity, both hydrothermal reaction and electrochemical reaction are actively utilized. A method (hydrothermal electrochemical method) has been proposed (Japanese Patent Application No. 1-177491, Japanese Patent Application No. 18233/1990).
8). According to this method, a thin film of a composite oxide such as barium titanate or strontium titanate can be synthesized at a temperature of 200 ° C. or lower without requiring any special post-treatment.

However, in the above method, there is a problem that the thickness of the composite oxide thin film such as barium titanate and strontium titanate cannot be grown to about 0.3 μm or more. And this (ie,
Insufficient growth of film thickness to some extent)
However, this is a factor that hinders the progress of basic research on the physical and chemical properties of composite oxide thin films by hydrothermal electrochemical methods.

Therefore, in order to apply the hydrothermal electrochemical method, which is a method for synthesizing a composite oxide thin film having excellent uniformity and crystallinity, to the production of thin films for various devices, the thickness is grown to several μm. It is necessary to be able to control the film thickness accurately.

The present invention solves the above-mentioned conventional problems and provides a composite oxide thin film having excellent uniformity and crystallinity, and a method for producing the composite oxide thin film, wherein the controllable film thickness is provided. It is an object of the present invention to provide a method for producing a composite oxide thin film having a wide range and high control accuracy.

[0016]

Means for Solving the Problems To achieve the above object, the present inventors conducted various experimental studies and improved the electrolytic processing method in the hydrothermal electrochemical method to control the film thickness range that can be controlled. And that the control accuracy thereof was greatly improved.

That is, according to the method for producing a composite oxide thin film of the present invention, an electrode containing a metal constituting the composite oxide and an arbitrary electrode are separated from each other by an alkaline solution having a pH of 13 or more containing another element constituting the composite oxide. The alkaline aqueous solution is immersed in an aqueous solution (treatment solution), and the alkaline aqueous solution is heated to a temperature from 80 ° C.
74.2 ° C.) (hydrothermal treatment), and in this hydrothermal treatment step, the temperature of the alkaline aqueous solution ranges from 100 ° C. or less to a prescribed temperature within the above range. In the meantime, a process (electrolytic process) of applying a current between the electrodes is performed.

Further, the present invention is characterized in that the thickness of the composite oxide thin film is controlled by using the amount of electricity supplied to the electrolytic system in the electrolytic treatment step as an index.

Further, the metal constituting the composite oxide is titanium (Ti), and the other elements constituting the composite oxide are barium (Ba) and strontium (Sr).
And the composite oxide is a perovskite-type composite oxide represented by the general formula ATiO ₃ (A = Ba, Sr).

Further, the composite oxide thin film of the present invention can be obtained by the general formula AT prepared by the above-described method for producing a composite oxide thin film.
It is a perovskite-type composite oxide thin film represented by iO ₃ (A = Ba, Sr).

[0021]

In the method for producing a composite oxide thin film of the present invention, the temperature is raised while the working electrode and the counter electrode are immersed in the solution containing the reaction components. By starting energization with the counter electrode, the reaction components in the solution and the working electrode continuously react, and it becomes possible to grow a composite oxide thin film on the working electrode. Further, by controlling the amount of electricity between the electrodes (the amount of electricity supplied to the electrolytic system), it is possible to accurately control the film thickness.

[0022]

EXAMPLE First, a metal plate of titanium (Ti) and platinum (Pt) having a size of 20 mm × 50 mm × 0.5 mm was prepared, and the surface of the Ti plate was polished to a mirror surface. Further, these metal plates were sufficiently washed with mixed nitric acid of acetone and chromium to obtain a titanium electrode (anode) and a platinum electrode (cathode). Then, using these electrodes and the thin film synthesizing apparatus shown in FIG. 1, the method for producing a composite oxide thin film according to the present invention was carried out as follows.

[0023]1. Production of strontium titanate thin film
(Example 1) First, as a processing solution, a strontium concentration of 0.5 mol
/ L, pH 14.0 strontium hydroxide (Sr (O
H)_Two1.) Prepare 500 ml of aqueous solution, which is shown in FIG.
It was placed in a Teflon beaker 1 of a thin film synthesis apparatus. It
The beaker 1 containing the processing solution 2 from the autoclave 3
Installed inside. Furthermore, an external electrode of the autoclave 3
4 into the internal beaker 1 and seal the autoclave 3
Power so that power can be supplied even when
A pair of titanium wire 5 and platinum wire 6
The electrode 7 and the platinum electrode 8 are connected, and the inside of the Teflon beaker 1 is
These electrodes are immersed in treatment solution 2 and autoclaved.
3 was sealed. In this state, it is 1.5
Temperature rises at a rate of ° C / min, after which a predetermined time elapses
And then cooled in the furnace. Also,
At the same time as the temperature rise process (50 °
A predetermined time at the above-mentioned synthesis temperature elapses from
Up to the titanium electrode 7 as the anode and the platinum electrode 8 as the cathode
Apply + 12V DC voltage between these electrodes
Electrolytic treatment was performed, and SrTiO of sample numbers # 1 to # 8 in Table 1
_ThreeA thin film was synthesized.

[0024]

[Table 1]

FIG. 2 shows the relationship between the hydrothermal temperature profile and the electrolytic treatment area in the manufacturing method of this embodiment.

Table 2 shows the thickness of each sample in Table 1.

[0027]

[Table 2]

The film thickness shown in Table 2 was obtained by calculation according to the following equation (1). T = δW / {Sρ (W _M1 / W _M2 )} (1) where T: film thickness δW: weight increase of titanium electrode S: surface area of titanium electrode ρ: density of formed film W _M1 : molecular weight of (Sr + 30) W _M2 : molecular weight of SrTiO ₃ .

The value obtained by the above equation (1) coincides with the average value of the measured values of the film thickness at many observation points of the film cross section by the scanning electron microscope. Therefore, equation (1)
It is possible to estimate the average film thickness of the generated film with high accuracy from the film thickness obtained by the above.

FIG. 3 shows the relationship between the holding time and the thickness of the SrTiO ₃ thin film. FIG. 3 shows a comparative example.
The change in the thickness of the composite oxide thin film in the conventional method in which the electrolytic treatment is performed only at the synthesis temperature of 150 ° C. is also shown (sample numbers # 16 to # 20 in Tables 1 and 2).

As shown in FIG. 3, in the case of the conventional method (comparative example), in the initial stage, the film thickness increases as the holding time increases, but when the holding time becomes about 60 minutes or more, the film thickness increases. The film thickness cannot be increased to about 0.3 μm or more.

On the other hand, in the case of the manufacturing method of the present invention (embodiment), the film thickness can be increased to 1.96 μm in a short time of 240 min (4 hours), and the holding time can be reduced. The film thickness can be linearly increased in proportion.

As is clear from this comparison, as in the above embodiment, by starting the electrolysis treatment earlier than the start time of the holding time (ie, a temperature lower than the holding temperature), the controllable film thickness range is obtained. Can be greatly increased to 2 μm or more, and a composite oxide thin film having such a large film thickness can be formed in a short time. Further, since the change in the film thickness is linear in proportion to the holding time, the film thickness can be easily controlled.

FIG. 4 shows an example in which the crystallinity of SrTiO ₃ thin films having various thicknesses synthesized according to this embodiment was confirmed by X-ray diffraction using a CuKα X-ray source. As shown in FIG. 4, the diffraction peaks other than SrTiO ₃ are only those of the metal Ti as the substrate, and no background showing the mixture of the amorphous phase is observed. It is clear that a SrTiO ₃ single-phase film was synthesized also in the film having

FIG. 5 shows an example in which a change in the composition of the SrTiO ₃ thin film having a thickness of about 2 μm in the thickness direction was examined using an Auger electron spectrometer. From FIG. 5, SrTi
Despite increasing the thickness of the O ₃ thin film to 2 μm,
The constituent elements of the rTiO ₃ thin film, ie, Sr, Ti, O
Is very uniform.

It should be noted that the method for producing a composite oxide thin film of the present invention requires that some of the elements constituting the desired composite oxide be supplied from a metal used as an electrode, and that other elements be supplied from a treatment solution. Because of the essential characteristics, there was a concern that the composition gradient of these elements inside the film became remarkable as the film thickness increased, but from the results of the composition analysis in the film thickness direction using the Auger electron spectrometer, It can be seen that the method for producing a composite oxide thin film of the present invention does not cause such a problem that the composition gradient of the constituent elements becomes significant.

In the above embodiment, the case where Sr (OH) ₂ was used as the Sr source to be contained in the processing solution was described. However, the substance that can be used as the Sr source is not limited to this. , Other substances such as Sr
There is no problem using (NO ₃ ) ₂ or the like.

As the substance for making the treatment solution alkaline (pH of 13.0 or more) within the range of the present invention, a commonly used base such as sodium hydroxide (Na) is used.
OH) and potassium hydroxide (KOH) can be used.
It can be easily adjusted to an alkalinity of H13.0 or more.

In the above embodiment, the case where a titanium metal electrode is used as the anode has been described. However, the anode does not need to be pure titanium metal, and titanium and another metal, for example,
It is also possible to use alloys with zirconium and aluminum.

Incidentally, such alloying of metal and titanium can also be used as a technique for doping those metals (elements) into the resulting film.

[0041] 2. Production of barium titanate thin film (Example
2) Barium concentration 0.5 mol / l, pH 1
A barium hydroxide (Ba (OH) ₂ ) aqueous solution of 4.0 was prepared, and a barium titanate (BaTiO ₃ ) thin film was synthesized using the same titanium electrode and platinum electrode as in Example 1 (Table 1, below). No. 2 sample numbers # 9 to # 12). The thin-film synthesizing apparatus used in this embodiment is the same as the thin-film synthesizing apparatus of the first embodiment shown in FIG.
Conditions (electrolysis treatment start temperature: 50 ° C., synthesis temperature 15)
0 ° C., electrolysis voltage 12 V).

FIG. 6 shows the relationship between the film thickness of the BaTiO ₃ thin film (sample numbers # 9 to # 12) and the 150 ° C. holding time according to this example.

FIG. 6 also shows, as a conventional method (comparative example), a change in the thickness of the composite oxide thin film in the conventional method in which the electrolytic treatment is performed only at a synthesis temperature of 150 ° C. 1, 2 sample numbers # 21 to # 25).

As shown in FIG. 6, in the case of the conventional method (comparative example), in the initial stage, the film thickness increases as the holding time increases, but when the holding time becomes about 60 minutes or more, the film thickness increases. The film thickness cannot be increased to about 0.3 μm or more. This is the same as in the case of the SrTiO ₃ thin film according to the conventional method (comparative example) of Example 1 above.

On the other hand, in the case of the manufacturing method according to the embodiment of the present invention, it is possible to linearly increase the thickness of the BaTiO ₃ thin film in proportion to the holding time. In addition,
The growth rate of the BaTiO ₃ thin film was SrTiO _{3 of} Example 1.
It is about 84% of that of the thin film.
Could be formed in time.

FIG. 7 shows the C of these BaTiO ₃ thin films.
FIG. 3 shows an X-ray diffraction pattern by a uKα X-ray source. According to FIG.
Diffraction peaks other than TiO ₃ were only those of metal Ti as a substrate, which indicates that a single phase film of BaTiO ₃ was synthesized.

[0047] 3. Barium strontium titanate thin film
As prepared (Example 3) treatment solution, barium hydroxide - strontium hydroxide _{((Ba X Sr 1-X} ) (OH) 2) a mixed solution was prepared, the total concentration of barium and strontium 0.5 mol / l,
At pH 14.2, its composition X is 0.250, 0.50
0 and 0.750 treatment solutions were prepared. A barium strontium titanate ((Ba, Sr) TiO ₃ ) solid solution thin film was synthesized using these treatment solutions and the same titanium electrode and platinum electrode as in Example 1 (sample numbers in Tables 1 and 2). # 13 to # 15).

When a composite oxide thin film was synthesized under the same film forming conditions as in Example 1 (electrolysis treatment start temperature: 50 ° C., synthesis temperature 150 ° C., electrolysis voltage 12 V) with a holding time of 240 min, SrTiO of Examples 1 and 2 above
_{Like the 3} thin film and the BaTiO ₃ thin film, a (Ba, Sr) TiO ₃ thin film having a film thickness of 1 μm or more could be formed.

FIG. 8 shows these (Ba, Sr) TiO
₃ shows an X-ray diffraction pattern of a _three- film CuKα X-ray source. FIG. 8 shows SrTiO ₃ and BaTi of Examples 1 and 2 in order to clarify the composition dependency of the diffraction pattern.
Data for the O ₃ end component thin film is also shown. From FIG. 8, it can be seen that each solid solution thin film shows a diffraction pattern of a single-phase cubic perovskite structure.

In the case of a solid solution, (Ba _X Sr _{1 -X} ) (O
Since it is practically important to clarify the composition X of the H) ₂ solution and the composition _{Y of the} (Ba _Y Sr _1-Y ) TiO ₃ thin film,
For SrTiO ₃ and BaTiO ₃ end components and solid solution thin films, the lattice constants were determined by the least square method, assuming that these thin films were cubic. Table 2 shows the lattice constants thus obtained.

FIG. 9 shows the relationship between the solution composition X and the thin film composition Y obtained by applying the Vegard rule to the solid solution system from the lattice constants in Table 2. FIG. 9 shows that it is possible to synthesize a solid solution film having a total composition from the SrTiO ₃ end component to the BaTiO ₃ end component.

[0052] 4. Hydrothermal temperature profile and electrolytic treatment area
Examples Regarding Regions In each of the above embodiments, the case where the hydrothermal temperature profile and the electrolytic treatment region shown in FIG. 2 are adopted has been described. However, the present invention relates to another hydrothermal condition that meets the conditions defined in claim 1. The present invention can also be implemented by employing a temperature profile and an electrolytic treatment region.

Here, examples of such a processing method are shown in FIGS. 10, 11 and 12, and the SrTiO ₃ thin films synthesized by those processing methods are sample numbers # 26 and # 27 in Tables 1 and 2. , # 28.

FIG. 10 shows an electrolysis treatment start temperature: 75 ° C., a synthesis temperature: 200 ° C. (holding time: 1.5 hours (90 min))
2 shows the relationship between the hydrothermal temperature profile and the electrolytic treatment region. The thickness of the SrTiO ₃ thin film synthesized by this processing method was 1.29 μm.

FIG. 11 shows an electrolysis treatment start temperature: 75
2 shows the relationship between the hydrothermal temperature profile and the electrolytic treatment region when the temperature is 300 ° C. and the synthesis temperature is 300 ° C. (holding time is 0 hour). The thickness of the SrTiO ₃ thin film synthesized by this processing method was 1.44 μm.

Since the SrTiO ₃ thin film having the above film thickness is formed even under the conditions shown in FIGS. 10 and 11, it is not necessary to set the holding time in order to achieve the purpose of growing the film. You can see that.

FIG. 12 shows an electrolytic treatment start temperature: 10
The relationship between the hydrothermal temperature profile and the electrolytic treatment region when the temperature is 0 ° C. and the synthesis temperature is 350 ° C. (holding time is 0 hour) is shown. The thickness of the SrTiO ₃ thin film synthesized by this processing method was 1.63 μm.

From this example, it can be seen that the electrolytic treatment may be continued until during the temperature decreasing process. Also, the synthesis temperature can be raised to just before the critical temperature of water (374.2 ° C.).

[0059] 5. Example of Precise Film Thickness Control Furthermore, in the method for producing a composite oxide thin film of the present invention, the thickness of the resulting film can be controlled with extremely high precision by the following method. That is, the relationship between the thickness of the generated film and the total amount of electricity supplied to the electrolytic system can be approximated by a simple functional relationship.

As an example, sample numbers # 1 to # in Tables 1 and 2
FIG. 13 shows the relationship between the film thickness and the quantity of electricity for the No. 8 SrTiO ₃ thin film. The relationship between the film thickness and the electrolysis time (holding time at 150 ° C.) is already shown in FIG.

As shown in FIG. 13, the film thickness changes linearly with respect to the quantity of electricity, similarly to the relationship between the film thickness and the electrolysis time. When the correlation coefficient between the film thickness and these variables is calculated, The value is 0.995 for the electrolysis time, but 0.999 is obtained for the quantity of electricity. Therefore, by using the amount of electrolytic electricity as an index, the thickness of the formed film can be controlled with extremely high accuracy of a correlation coefficient of 0.999.

The present invention is not limited to the above embodiment, but includes the types of metals constituting the composite oxide, the types of other elements constituting the composite oxide, and the p of the processing solution.
Regarding H, hydrothermal treatment temperature and treatment time, electrolysis treatment temperature and treatment time, various applications and modifications can be made within the scope of the present invention.

[0063]

As described above, in the method for producing a composite oxide thin film of the present invention, an electrode containing a metal constituting a composite oxide and an arbitrary electrode are formed by mixing an electrode containing another element constituting the composite oxide. The treatment solution is immersed in a treatment solution to be heated and heated to a predetermined temperature (hydrothermal treatment), and a process of applying electricity between the electrodes during the heating process (electrolysis treatment) is performed. Composite oxide thin film with excellent properties and crystallinity
It can be synthesized reliably at a low temperature of ℃ or lower,
The thickness of the composite oxide thin film can be controlled in a range sufficient for industrial use (a range of 0.1 to 2.0 μm).

In the electrolytic treatment, the total amount of electricity supplied to the electrolytic system is used as an index to control the film thickness with extremely high accuracy.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a thin film synthesizing apparatus using both hydrothermal treatment and electrolytic treatment used in an embodiment of the present invention.

FIG. 2 Electrolysis treatment start temperature: 50 ° C., synthesis temperature: 150
It is a figure which shows the relationship between the hydrothermal temperature profile in the case of ° C, and an electrolysis process area | region.

FIG. 3 Electrolysis treatment start temperature: 50 ° C., synthesis temperature: 150
FIG. 2 is a diagram showing the relationship between the SrTiO ₃ thin film and the holding time at 150 ° C. in the case where the temperature is 12 ° C. and the electrolysis voltage: DC 12 V (however, in the conventional method, the film in the case where the electrolytic treatment of DC 12 V is performed only at the synthesis temperature of 150 ° C. Thickness change).

FIG. 4 is an X-ray diffraction diagram of SrTiO ₃ thin films having various thicknesses.

FIG. 5 SrTiO ₃ analyzed by Auger electron spectroscopy
It is a figure which shows the relative concentration of each element of Sr, Ti, and O in a thin film.

FIG. 6: Starting temperature of electrolytic treatment: 50 ° C., synthesis temperature: 150
FIG. 2 is a diagram showing the relationship between the BaTiO ₃ thin film and the holding time at 150 ° C. in the case of 12 ° C., electrolysis voltage: DC 12 V (however, in the conventional method, the film in the case of performing the electrolytic treatment of DC 12 V only at the synthesis temperature of 150 ° C.) Thickness change).

FIG. 7 is an X-ray diffraction diagram of BaTiO ₃ thin films having various thicknesses.

FIG. 8 shows X of a SrTiO ₃ thin film, a BaTiO ₃ thin film, and a (Ba, Sr) TiO ₃ solid solution thin film having various compositions.
FIG.

FIG. 9 shows the composition X of (Ba _X Sr _1-X ) (OH) ₂ solution and (Ba _Y
FIG. ₃ is a view showing the relationship of the composition Y of a (Sr _{1 -Y} ) TiO ₃ solid solution thin film.

FIG. 10: Electrolysis treatment start temperature: 75 ° C., synthesis temperature: 20
It is a figure which shows the relationship between the hydrothermal temperature profile in the case of 0 degreeC, and an electrolysis process area | region.

FIG. 11: Electrolysis treatment start temperature: 75 ° C., synthesis temperature: 30
It is a figure which shows the relationship between the hydrothermal temperature profile in the case of 0 degreeC (holding time: 0 hour), and an electrolysis processing area.

FIG. 12: Electrolysis treatment start temperature: 100 ° C., synthesis temperature: 3
It is a figure which shows the relationship between a hydrothermal temperature profile in the case of 50 degreeC (holding time: 0 hour), and an electrolysis process area | region.

FIG. 13: Electrolysis treatment start temperature: 50 ° C., synthesis temperature: 15
FIG. 3 is a diagram showing the relationship between the thickness of a SrTiO ₃ thin film and the amount of electrolysis when 0 ° C. and electrolysis voltage: DC 12 V.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Teflon beaker 2 Processing solution (alkaline aqueous solution) 3 Autoclave 4 Power supply 5 Titanium wire 6 Platinum wire 7 Titanium electrode 8 Platinum electrode

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Masahiro Yoshimura 1-6-12 Teraonaka, Ayase City, Kanagawa Prefecture (56) References JP-A-3-138393 (JP, A) JP-A 5-112895 (JP, A) JP-A-6-290988 (JP, A) JP-A-6-306678 (JP, A) JP-A-3-13599 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) ) C25D 11/00-11/38 C25D 9/04-9/08

Claims (4)

(57) [Claims] 1. An electrode containing a metal constituting a composite oxide and an arbitrary electrode are immersed in an alkaline aqueous solution (treatment solution) having a pH of 13 or more containing another element constituting the composite oxide. A treatment (hydrothermal treatment) for raising the temperature of the aqueous solution to a predetermined temperature in the range of 80 ° C. to the critical temperature of water (374.2 ° C.), and a temperature at which the temperature of the alkaline aqueous solution is 100 ° C. or less in this hydrothermal treatment step A process (electrolysis process) of applying a current between the electrodes until the temperature reaches a predetermined temperature within the above range. 2. The production of a composite oxide thin film according to claim 1, wherein the thickness of the composite oxide thin film is controlled by using an amount of electricity supplied to an electrolytic system as an index in the electrolytic treatment step. Method. 3. The metal constituting the composite oxide is titanium (Ti), and the other element constituting the composite oxide is at least one of barium (Ba) and strontium (Sr); and , The composite oxide having the general formula ATi
_{3. The} method for producing a composite oxide thin film according to claim 1, wherein the composite oxide is a perovskite-type composite oxide represented by O ₃ (A = Ba, Sr). 4. A perovskite-type composite oxide thin film produced by the method for producing a composite oxide thin film according to claim 3.