WO2004026762A1

WO2004026762A1 - Ultra-fine metal oxide particle suspension and ultra-fine metal oxide particle thin film

Info

Publication number: WO2004026762A1
Application number: PCT/JP2003/011821
Authority: WO
Inventors: Yasuhisa Yamashita
Original assignee: Murata Manufacturing Co., Ltd.
Priority date: 2002-09-20
Filing date: 2003-09-17
Publication date: 2004-04-01
Also published as: JP4311134B2; AU2003264459A1; JP2004300013A

Abstract

An ultra-fine metal oxide particle suspension which has been prepared by the hydrolysis reaction of a raw material in a micro-emulsion containing a hydrophobic disperse medium (6), water (4) and a surfactant (2), wherein the raw material comprises a composite metal alkoxide, and the amount of water contained in the micro-emulsion is 0.95 to 3 times that required for the hydrolysis of the composite metal alkoxide; and an ultra-fine metal oxide particle thin film formed by using the ultra-fine metal oxide particle suspension. The suspension has ultra-fine metal oxide particles which are nearly uniform in composition, particle diameter and shape, are crystallized, and are highly dispersed in the medium, and the metal oxide particle thin film has particles having a reduced particle diameter and being densely packed.

Description

Description Ultrafine metal oxide dispersion solution and ultrafine metal oxide thin film

The present invention relates to a metal oxide ultrafine particle dispersion solution in which metal oxide ultrafine particles are dispersed, in particular, a metal oxide ultrafine particle dispersion solution suitable for producing a composite metal oxide ultrafine particle thin film, and a nano-sized metal oxide ultrafine particle. The present invention relates to a metal oxide ultrafine particle thin film comprising fine particles and having excellent dielectric properties. Disclosure of invention

In recent years, with the demand for miniaturization of devices, research and development of increasingly sophisticated devices have been energetically performed.

For example, composite metal oxides such as barium titanate and lead zirconate titanate are widely used in multilayer capacitor actuators and the like because of their excellent dielectric properties and piezoelectric properties.

For further miniaturization and higher performance, thinning of the element is indispensable. For this purpose, it is important to establish a high-quality thin-film manufacturing technology consisting of finer ultrafine particles.

However, on the other hand, ferroelectric materials are said to lose ferroelectricity at a certain critical grain size due to the size effect.

For example, in the case of barium titanate used in multilayer capacitors, it is said that the ferroelectricity disappears at about 50 nm. It cannot be applied to electronic devices as a dielectric.

Therefore, in multilayer capacitors, for example, barium titanate of about 50 nm synthesized by a hydrolysis method, for example, is grown to 100 nm or more by heat treatment to improve the crystallinity. It is manufactured by mixing and pulverizing with an agent and the like, forming a slurry, forming a sheet, stacking these, and further removing the binder and firing.

However, in multilayer capacitors, the thickness of the multilayer capacitor has been reduced to about 1 m, and in this case, in order to obtain sufficient reliability, for example, 10 Therefore, miniaturization to about 100 nm per particle is required.

Furthermore, assuming an element thickness of 0.5 m as a next-generation multilayer capacitor, it is necessary to reduce the particle size to about 50 ηm.

That is, while seeking for finer particles by thinning, the size effect is suppressed to its limit. Is required.

However, as a matter of fact, accurate experimental data at such a nano-level particle size has not been obtained, and ferroelectric properties in the nano-range are hardly clarified.

This is because 1) it was difficult to obtain fine, narrow grain size distribution and highly crystalline ceramic nanoparticles 2) it was difficult to obtain a dense sample while maintaining the fine particle size Attributed to

Also, when the powder sample and the thin film sample are compared even if they have the same particle size, the critical particle size of the thin film sample may be changed as compared with the powder sample due to the influence of stress from the substrate surface and the like.

In fact, although there have been reports of ceramic nanoparticle thin films that exhibit some ferroelectric properties at the nanoparticle level, they show ferroelectricity with an average particle size of 50 nm or less and ferroelectricity by a practical production method. A ceramic nanoparticle thin film having characteristics has not been obtained.

First, as a method of forming a ceramic thin film with excellent orientation, gas phase methods such as molecular beam epitaxy (MBE), chemical vapor synthesis (CVD), and physical vapor deposition (PVD) are used. The law is known.

However, these methods are very costly. When producing two or more types of composite metal oxide ultrafine particles, it is difficult to match the composition due to differences in the vapor pressure, sublimability, and chemical reactivity of each metal. The fact is that it has not been reached.

On the other hand, thin film formation using a liquid phase method represented by a sol-gel method is more advantageous than a gas phase method from the viewpoints of composition controllability and cost, and has been extensively studied.

Here, when a thin film is formed by the sol-gel method, generally, a precursor solution obtained by partially hydrolyzing a metal alkoxide solution as a raw material without adding K or adding a small amount of water is used. After the adjustment, the film is formed by spin coating or dip coating.

However, it is necessary for these gel thin films obtained by the sol-gel method to very slowly progress the hydrolysis reaction to form the target oxide after film formation. Therefore, when hydrolysis is performed rapidly, many cracks are formed due to shrinkage of the film, and a good quality thin film cannot be obtained.

Therefore, it is necessary to perform aging for a long time to obtain a good quality thin film without cracks.

The film formed in this manner is generally amorphous containing an organic compound. To obtain a crystalline film, it is necessary to further bake the film after forming the film.

However, in this case, the amorphous phase of the film may form an intermediate phase during firing, causing problems such as an increase in surface roughness that hindered densification, and the formation of a different phase at the interface with the substrate. And deteriorated the characteristics. In this case, since it is necessary to perform the firing at a relatively high temperature, the firing causes grain growth, and it has been difficult to obtain a dense thin film while maintaining a sufficiently small particle size.

Therefore, these problems can be solved by preparing a composite metal oxide ultrafine particle dispersion in which crystallized ultrafine composite metal oxide particles are highly dispersed in a solvent.

Specifically, a film is formed by using the prepared dispersion solution, for example, by spin coating, dried, and then subjected to a heat treatment at a relatively low temperature, thereby forming a dense thin film while maintaining a sufficiently fine particle size. Can be obtained.

In order to prepare such a composite metal oxide ultrafine particle dispersion solution, it is necessary to synthesize ultrafine composite metal oxide particles having a uniform composition, a uniform particle diameter, and crystallized, and to disperse them in a solvent to a high degree. It is necessary to make it.

However, as the miniaturization progresses, it is said that the control of agglomeration of ceramic fine particles becomes difficult, and that the presence of water causes hard agglomeration (see Chemical Industry, April 1995, Item 45).

That is, when water is present on the powder surface, as shown in FIG. 1, adjacent fine particles are cross-linked by hydrogen bonding via water, and aggregation proceeds. Then, once the water is removed and once aggregated due to crosslinking between the fine particles via oxygen, it becomes very difficult to crush the aggregated ceramic fine particles and re-disperse them at a high level.

Therefore, the key is to synthesize the ultrafine composite metal oxide particles with high crystallinity first, and then to keep the ultrafine particles once synthesized in a dispersed state without agglomeration.

Here, Japanese Patent Application Laid-Open No. 2001-163617 discloses recently reported metals such as a metal colloid method, a microemulsion method (reverse micelle method), a polymer complex method, a metal alcohol hydrolysis method, and a Grignard method. The production methods of the oxide ultrafine particles are listed.

Among these, the WZO (Water in Oil) microemulsion method involves adding water together with a surfactant to a hydrophobic liquid to disperse it as micro water droplets, and introducing the water by a reaction such as hydrolysis in these water droplets. This is a method of reacting raw materials to obtain ultrafine metal oxide particles. .

In the WZO microemulsion method, it is known that the particle size and the surface structure of the metal oxide fine particles are controlled on a nano-scale (see Chem. Phys. Ett. 125, 299, etc.).

However, generally, after the synthesis, fine particles obtained by further adding a precipitant or the like are completely precipitated, and the precipitate is removed by a centrifuge.

The target fine particles are separated and obtained by washing the mixture of the fine particles, which are the sediment, and the surfactant with an organic solvent or the like (see JP-A-9-1255331).

Here, if ultrafine particles synthesized by the microemulsion method can be dispersed in a solution without coagulation, they can be used as a solution for forming a thin film of metal oxide ultrafine particles. Can be.

The water droplets of the emulsion are thermodynamically stable and dispersed. However, as shown in Fig. 2, the individual droplets 1 and 1 repeat binding and dissociation.

Therefore, when the composite metal oxide ultrafine particles are synthesized by the microemulsion method, while the above-described bonding and dissociation are repeated, the synthesized fine particles gradually aggregate and precipitate.

Further, in the ultrafine metal oxide thin film used for a dielectric device, as described above, there is a problem that when the crystal grain size is reduced, the ferroelectric characteristics disappear at a certain critical grain size.

For this reason, there is a need to further reduce the thickness and improve the performance while suppressing the size effect that the ferroelectric properties disappear depending on the size to its limit.

The present invention has been made in view of the above points, and has a metal oxide superfine particle having a uniform composition, a uniform particle size and shape, and highly dispersed crystallized ultrafine metal oxide particles. The main purpose is to provide a fine particle dispersion solution, and to provide a fine metal oxide ultrafine particle thin film having a small particle size by using the obtained composite metal oxide ultrafine particle dispersion solution. It is an object of the present invention to provide a thin film of nano-sized metal oxide ultrafine particles having excellent characteristics. Disclosure of the invention

Therefore, the present inventors have conducted intensive studies to achieve the above object, and as a result, when synthesizing ultrafine metal oxide particles by the microemulsion method, as a raw material that consumes water in the emulsion during the reaction process, for example, A metal alkoxide is used. By reducing the amount of water in the microemulsion solution as much as possible, almost all water is consumed after the reaction, and it is possible to obtain a solution in which the synthesized ultrafine metal oxide particles are highly dispersed in the solvent after the reaction. The invention has been completed.

That is, the metal oxide ultrafine particle dispersion solution of the present invention is a metal oxide ultrafine particle produced by a hydrolysis reaction of a raw material in a microemulsion containing a dispersion medium that is a hydrophobic liquid, water, and a surfactant. A dispersion solution, wherein the raw material is a composite metal alkoxide solution obtained by mixing and complexing a plurality of metal alkoxides in an alcohol; the raw material is a composite metal alkoxide; and the microemulsion is included in the microemulsion. The amount of water used is 0.95 times or more and 3 times or less the amount of water required for hydrolysis of the raw material.

Here, the ultrafine particles refer to, for example, particles having an average particle diameter of 100 nm or less.

According to the present invention, the amount of water contained in the microemulsion is set to 0.95 times or more the guess required for the hydrolysis of the raw material, so that the undecomposed raw material without hydrolysis and the crystallinity are sufficient. It is possible to reduce the ratio of amorphous ultrafine particles that are not minute. Furthermore, since the amount of water contained in the microemulsion is less than three times the amount of water required for hydrolysis of the raw materials, aggregation of the metal oxide ultrafine particles generated after the reaction is suppressed, and highly dispersed transparent metal oxide It becomes an ultrafine particle dispersion solution.

Further, according to the present invention, the metal alkoxide solution serving as the raw material solution is a composite metal alkoxide solution in which a plurality of metal alkoxides are compounded, so that the ultrafine particles generated are very fine, have a uniform composition, and It becomes fine particles of a single phase composite metal oxide crystallized and uniform in diameter and shape.

In still another embodiment of the present invention, at least one of the plurality of metal alkoxides is a barium alkoxide, and the composite metal alkoxide solution contains a polymerization inhibitor that suppresses polymerization of the barium alkoxide.

As the polymerization inhibitor, for example, benzene is preferable.

According to the present invention, since a polymerization inhibitor such as benzene that suppresses the polymerization of barium alkoxide is contained, polymerization of barium alkoxide is suppressed, and a homogeneous composite metal alkoxide of barium alkoxide and another metal alkoxide can be obtained. Can be.

The metal oxide ultrafine particle thin film according to the present invention is manufactured using the metal oxide ultrafine particle dispersion prepared by the method of the present invention.

According to the present invention, a dense metal oxide ultrafine particle thin film having a small particle diameter can be obtained.

The metal oxide ultrafine particle film according to the present invention is檎成average particle diameter 1 5 nm or more 50 nm or less of the metal oxide ultrafine particles in the residual polarization (P r), 2P "mosquito 2 0 ₀ 2 It has the above ferroelectric characteristics, and has a relative dielectric constant of 300 or more at a measurement frequency of 1 kHz.

According to the present invention, since the average particle diameter is 50 nm or less, it is possible to further reduce the thickness.On the other hand, even if the particles are composed of ultrafine particles of 15 to 50 nm, 2Pr is 2〃CZcm2. An excellent thin film having the above ferroelectric properties and a relative dielectric constant of 300 or more at a measurement frequency of 1 kHz can be obtained.

In addition, it is preferable that the metal oxide ultrafine particles constituting the metal oxide ultrafine particle thin film of the present invention are a perovskite-type oxide containing titanium and barium. As described above, even a composite oxide such as a bevelskite-type oxide containing titanium and barium has an average particle diameter of 50 nm or less. To obtain an excellent thin film with ferroelectric properties of 2 Pr of 2 Ccm2 or more and a relative dielectric constant of 300 or more at a measurement frequency of 1 kHz, even if it is composed of ultrafine particles of 1550 nm. Can be.

As described above, according to the present invention, since the amount of water contained in the microemulsion is limited, It is possible to easily obtain a metal oxide ultrafine particle dispersion in which the composition is uniform, the particle diameter and the shape are uniform, and the crystallized ultrafine metal oxide particles are highly dispersed.

Further, using the obtained dispersion solution of ultrafine metal oxide particles, it is possible to produce a fine metal oxide ultrafine particle thin film having a small particle diameter, particularly a metal oxide ultrafine particle thin film.

In addition, since the composite metal alkoxide is used as a raw material, it is possible to obtain a composite metal oxide ultrafine particle dispersion solution in which the composite metal oxide ultrafine particles are highly dispersed and a thin composite metal oxide ultrafine particle thin film having a small particle diameter. it can.

In addition, according to the metal oxide ultrafine particle thin film of the present invention, the average particle size is 50 nm or less, so that when used for a device, it is possible to reduce the size and thickness of the device and to reduce the size effect. It is possible to obtain excellent dielectric properties by suppressing the above. BRIEF DESCRIPTION OF THE FIGURES

Figure 1 is a schematic diagram of the mode of aggregation of ceramic fine particles via water.

FIG. 2 is a schematic diagram of a dispersion association mode of emulsion water droplets in a dispersion medium.

FIG. 3 is a schematic diagram of the ultrafine particle dispersion mode after microemulsion and hydrolysis. FIG. 4 is a cross-sectional view showing a manufacturing process of a laminated condenser using the metal oxide ultrafine particle thin film of the present invention.

FIG. 5 is a sectional view of a thin film element using the present invention.

FIG. 6 is a particle size distribution diagram showing the particle size distribution of Example B of the present invention.

FIG. 7 is a SEM photograph of the example of the present invention.

FIG. 8 is a cross-sectional view of the measurement sample.

FIG. 9 is a diagram showing the hysteresis characteristics of the example of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in more detail.

The microemulsion according to the present invention is a W / O microemulsion comprising a dispersion medium, which is a hydrophobic liquid, water, and a surfactant.

Examples of the dispersion medium that is a hydrophobic liquid include petroleum hydrocarbons such as kerosene, nonpolar hydrocarbons such as cyclohexane, hexane, cyclopentane, benzene, and octane, and ethers such as getyl ether and isopropyl ether. Can be

Surfactants include ionic surfactants such as AOT (sodium bis (2-ethylhexyl) sulfosucciate) and SDS: CH3 (CH2) 110S03Na, and ΝΡ-η (π = 1 to 10): ( ρ-C9H19)-C6H4-Ο-(C H2C H20) nC H2C H20 H or polyoxyethyle n e (n) lauiylether: Any of nonionic surfactants such as C12H25 (0CH2CH2) nOH can be used, but in the case of anionic surfactant, an extra component is added to the membrane component. Nonionic surfactants are preferred because they remain.

The raw material of the present invention is a composite metal alkoxide.

This composite metal alkoxide is usually obtained by mixing a plurality of single metal alkoxides in an alcohol to form a composite. It can also be obtained by mixing and mixing a plurality of composite metal alkoxides—single metal alkoxide and composite metal alkoxide in alcohol. '

Examples of the single metal alkoxide include, but are not limited to, barium methoxide, barium methoxide, barium propoxide, barium butoxide, titanium methoxide, titanoxide, and titanium propoxide.

This alcohol includes ethanol, propanol, butanol, isopropyl alcohol and the like.

The composite metal alkoxide is not particularly limited. Magnesium methoxide, magnesium titanium ethoxide and the like. Composite metal alkoxides

The amount of water in the microemulsion of the present invention is preferably 0.95 times or more and 3 times or less the amount of water required for hydrolyzing the metal alkoxide as a raw material.

The amount of water required for hydrolysis is defined by a chemical reaction formula, for example, a hydrolysis reaction of barium isopropoxide Ba (isop) 2 and titanium isopropoxide T i (isop) 4 Then, it becomes as follows.

B a (isop) 2 + T i (isop) 4 + 3H20 → Ba T i 03 + 6 isopropano I Therefore, in this case, 3mo for each 1 mo I of barium isopropoxide and titanium isopropoxide I water is required for hydrolysis.

In this case, the amount of water contained in the microemulsion must be 0.95 times or more and 3 times or less of the amount of water required for hydrolysis, that is, 2.85moI or more and 9moI or less. .

When the amount of water is less than 1 time, water is completely consumed after the reaction, so that a very clear dispersion solution can be obtained.In addition, the solution remains without hydrolysis after the reaction or is amorphous and crystalline. Some of the fine particles that are not sufficient are included. However, since these phases may enter between the super-dispersed particles that form a film during film formation and increase the film density or act as a sintering aid, the amount of water is adjusted to 1 times or less and undecomposed. Or it may be better to adjust to include the amorphous part.

However, since the proportion of the crystalline phase decreases as the undecomposed or non-crystalline phase increases, it is preferable to contain water at least 0.95 times.

Further, when the amount of water is 1.05 times or more and 1.2 times or less, it is more preferable to obtain a composite metal oxide ultrafine particle dispersion solution which is clear, has high dispersion and high crystallinity.

By minimizing the amount of residual water after the reaction, it also has the effect of preventing the composition of the synthesized composite metal oxide from shifting.

For example, in barium titanate, the B a Z Ti ratio in a substance is an important factor in the properties, but it is known that in water, a part of lime is eluted.

In general, when the synthesis is carried out by the hydrolysis method, the synthesis is carried out using raw materials that have been adjusted in excess of vacuum.

On the other hand, when there is almost no water remaining after the reaction as in the present invention, barium ions do not dissolve into water, so that it is possible to obtain uniform ultrafine particles of interest with the adjusted raw material composition. it can.

Therefore, the amount of water contained in the microemulsion is reduced to 0.95 times or more and 3 times or less, preferably 1.05 times or more and 1.2 times or less of the amount of water required for hydrolysis. —Also has the advantage that compositional deviations due to the remaining easily soluble components in the water can be almost eliminated.

In the microemulsion, it is preferable to add one or more alcohols as another surfactant, so-called cosurfactant.

FIG. 3 is a schematic diagram showing the microemulsion solution and the vicinity of a part of the droplets in an enlarged manner, and also showing the state after the hydrolysis reaction with the addition of the composite metal alkoxide.

In the figure, 2 is a surfactant, 3 is a cosurfactant, 4 is water, 5 is a reaction product,

6 is a dispersion medium such as cyclohexane.

In the same figure, E indicates the complex alkoxide, F indicates the hydrolysis, and G indicates after the hydrolysis reaction. By adding one or more types of alcohol as a corrosive factor, water droplets can be more stably present during microemulsion adjustment.

Further, when the water in the emulsion is consumed after the reaction to produce a composite metal oxide, the composite metal oxide enters between the interface of the composite oxide and the surfactant, and the surfactant remains around the composite oxide ultrafine particles. It can be considered that the synthesized composite ultrafine particles can be stably dispersed in the same manner as in the case of water because they can exist in the form of surrounding water. It is considered that the cosurfactant has an effect of entering the hydrophilic portion of the surfactant, lowering the interfacial energy with water, and reducing the steric hindrance of the long carbon chain of the hydrophilic portion of the surfactant.

The carbon number of an appropriate alcohol depends on the length of the carbon chain of the hydrophilic part of the surfactant, but is preferably about 4 to 10.

If it is 4 or less, the hydrophilicity is too high, so it is considered that it is dissolved in water and does not exist only at the water-surfactant interface.

On the other hand, if it is larger than 10, the hydrophobicity becomes too large, and the steric hindrance becomes large.

It is preferable that a metal alkoxide is used as a raw material, and that each metal alkoxide is mixed and complexed before hydrolysis.

Barium alkoxide is known to be easily polymerized in alcohol. Here, J. Am. Ceram. Soc, 77 [2] paragraphs 603-605 and Jpn. J. Appl. Phys. Vol36,

Paragraphs 5939-5942 state that crystals of BaTi (OCH (CH3) 2) -C6H6 can be obtained by aging an iso-propanol solution of barium and titanium in benzene. ing.

In this, benzene hardly dissolves the metal alkoxide, helps stabilize and precipitate Ba T i (OCH (CH3) 2) -C6H6 crystals, and has the effect of suppressing the polymerization of barium alkoxide. Is suggested.

Therefore, it is considered that by adding benzene within a range in which crystals do not precipitate, polymerization of barium alkoxide is suppressed, and a uniform barium titanium double alkoxide is easily obtained.

For this reason, it is necessary to adjust the barium-containing composite alkoxide raw material solution by partially adding benzene, which has a function of suppressing the polymerization of barium alkoxide, to an alcohol solvent and use the same. Is preferred to obtain

In addition, as long as it has the same kind of effect, it can be used without being limited to benzene. The metal oxide ultrafine particle thin film of the present invention is manufactured using the metal oxide ultrafine particle dispersion prepared by the method of the present invention.

Since ultra-fine particles of the metal oxide ultra-fine particle dispersion solution have high crystallinity, relatively low temperature, for example,

Heat treatment can be performed at 600 ° C. or less.

The metal oxide ultrafine particle thin film of the present invention is composed of metal oxide ultrafine particles having an average particle size of 15 nm or more and 50 nm or less and has ferroelectric properties.

As the ferroelectric properties, it is preferable that 2 Pr has a ferroelectric property of 2 jU C / cm 2 or more in remanent polarization (P r), and the relative dielectric constant at a measurement frequency of 1 kHz (room temperature). Is 3 It is preferably at least oo.

A metal oxide ultrafine particle thin film composed of ultrafine particles of 15 to 50; Um as in the present invention, wherein 2 Pr is 2 jW CZ cm 2 or more in remanent polarization (P r). If it has ferroelectric characteristics and has a relative permittivity of 300 or more, it functions sufficiently as a ferroelectric device such as a thin film capacitor or a multilayer capacitor.

Therefore, by using a metal oxide ultrafine particle thin film composed of ultrafine particles of 15 to 50 nm as in the present invention, it is possible to further reduce the thickness and size.

In addition, when the metal oxide ultrafine particle thin film of the present invention is used as a thin film capacitor, it is composed of fine particles of 15 to 50 nm, so that the number of particles per layer can be increased and reliability is improved. In addition to being able to greatly improve, it is possible to further reduce the thickness and size.

The metal oxide ultrafine particle thin film of the present invention is obtained by synthesizing ultrafine and crystallized metal oxide ultrafine particles, for example, ceramic nanoparticles composed of a perovskite-type oxide containing titanate. Keeping it in a highly dispersed state as it is, forming a film on the substrate, then growing the grains to 15 nm or more and 50 nm or less by adding energy such as heat treatment, and further promoting densification and crystallization Manufactured.

Examples of such a film forming method include a solution in which ultrafine metal oxide particles having a uniform particle size distribution are kept in a highly dispersed state as they are, for example, from the microemulsion (ME) method. Using a metal oxide ultrafine particle dispersion solution as a raw material solution, a thin film is prepared by a method of forming a film directly by spin coating, etc., and this is further heat-treated using an RTA (Rapid Thermal Annealing) furnace or the like. Can be manufactured.

In addition, the metal oxide ultrafine particle thin film of the present invention has an average particle diameter of, for example, 30 nm or less, for example, a ceramic oxide nanoparticle made of a perovskite-type oxide containing titanate. A ceramic nanoparticle produced by a series of processes of synthesizing, maintaining the synthesized ceramic nanoparticles in a medium in a highly dispersed state, and forming a film of the highly dispersed ceramic nanoparticles on a substrate. The thin film is manufactured by further grain growth of 15 nm to 50 nm by adding energy such as heat treatment.

As described above, ceramic fine particles, that is, ceramic nanoparticles, are highly agglomerated, and once agglomerated, it is extremely difficult to redisperse them separately.-After synthesizing ceramic nanoparticles, It must be kept in a highly dispersed state in the medium.

For this purpose, it is necessary to produce the desired nanoparticles by reacting the raw materials in a fine reaction space partitioned into nano-sizes in a medium, and to keep them in a state in which they are not aggregated. The microemulsion method is a preferred method. wo Microemulsion, as described above, is composed of a hydrophobic liquid dispersion medium, water, and a surfactant, and a water droplet having a diameter of several nm to several 10 nm is thermally dispersed in a hydrophobic solvent. Can be dispersed stably.

For example, in the case of barium titanate used in a multilayer capacitor, a Ba, Ti composite alkoxide raw material solution is dropped into the crystallized titanate, which is very fine and has a uniform particle size corresponding to the water droplet diameter. Barium nanoparticles can be synthesized.

In addition, by adjusting the amount of water in the microemulsion composition to 0.95 times or more and 3 times or less the amount of water required for hydrolysis as described above, the synthesized barium titanate nanoparticles can be prevented from aggregating. A stable dispersed state can be obtained as it is.

Here, the synthesized nanoparticles need to be subsequently grown to a particle size of 50 nm or less by heat treatment, so the synthesized nanoparticles are preferably as small as possible and the average particle size is small. It is preferably at least 30 nm or less, more preferably 10 nm or less.

The nanoparticle dispersion solution prepared in this manner is applied to a substrate by using, for example, a spin coating method, a dip coating method, a screen printing method, and the like. In order to enhance the properties, a heat treatment step and a heat treatment step are performed to produce a dense barium titanate nanoparticle thin film.

Adjustment of the average particle size after film formation can be performed using an electric furnace, an infrared furnace, an RTA furnace, or the like.

In particular, in the infrared furnace RTA furnace, high-speed temperature rise is possible, and high-speed temperature rise and short-time heat treatment are preferable because grain growth can be suppressed even at the same temperature.

Ultrafine metal oxide particles synthesized by the microemulsion method are deposited in a highly dispersed state, so even if they are nanoparticles, they are formed into dense thin films. The formation of an intermediate layer does not hinder densification and does not greatly increase the surface roughness.

Further, there is no possibility that a different phase is formed at the interface with the substrate to deteriorate the electric characteristics.

Furthermore, since the finest and crystallized nanoparticles are grown as small as possible by heat treatment or the like, densification and crystallization are progressing even if the average particle size is as small as 50 nm or less. Excellent dielectric properties and reliability can be expected.

Also, unlike the powder sample, the metal oxide ultrafine particle thin film obtained in this way may be a nanoparticle having an average particle size smaller than the generally known critical size due to the influence of stress from the substrate. May exhibit ferroelectricity.

Actually, it was confirmed that the metal oxide ultrafine particle thin film obtained by the production method of the present invention exhibited ferroelectricity even when the average particle diameter was 50 nm or less, and also had excellent dielectric properties. In addition, since the metal oxide ultrafine particle thin film formed in this manner is formed in a series of steps from synthesis to dispersion and film formation, it does not involve multiple steps, and the apparatus and the manufacturing process are not complicated. It also has points.

Next, an example in which the metal oxide ultrafine particle thin film of the present invention is applied to an electronic device will be described.

The metal oxide ultrafine particle thin film of the present invention can be used for various electronic devices. For example, FIG. 4 shows an example of a configuration when applied to a multilayer capacitor.

A ceramic layer 8 is formed on a substrate 7 such as the alumina substrate shown in FIG. 1A, as shown in FIG. 2B, and a first-layer conductor electrode 9a is formed thereon. Then, a ceramic layer 8 is formed thereon, a second-layer conductor electrode 9b is further formed, a ceramic layer 8 is further formed, and a third-layer conductor electrode 9a is formed thereon. You.

By repeating such a process, a plurality of conductor electrodes 9a and 9b and a plurality of ceramic layers 8 are alternately laminated on the surface of the substrate 7, and a plurality of conductor electrodes 9a and 9b are formed. A ceramic-metal laminate 10 including a plurality of ceramic layers 8 is formed.

Here, each ceramic layer 8 is formed by the method for producing a metal oxide ultrafine particle thin film of the present invention, and each of the conductor electrodes 9 a and 9 b is formed by any one of a CVD method, a vapor deposition method, and a sputtering method. The thickness of each ceramic layer 8 and each conductor electrode 9a, 9b is, for example, 1; Um or less.

The conductor electrodes 9a and 9b serving as internal electrodes are patterned by using a mask, and the odd-numbered conductor electrodes 9a and the even-numbered conductor electrodes 9b are alternately opposite. Side end.

Thereafter, when the substrate 7 is selectively removed by etching or the like, only the ceramic-metal laminate 10 as shown in FIG.

Next, when external electrodes 11a and 11b are formed at both ends by dipping and sputtering, the odd-numbered conductor electrodes 9a conduct with one external electrode 11a, and the even-numbered conductive electrodes 9a. The body electrode 9b is electrically connected to the other external electrode 11b, and an ultra-small multilayer ceramic capacitor 12 as shown in FIG.

FIG. 5 shows an example of a configuration in which the metal oxide ultrafine particle thin film of the present invention is applied to a dielectric thin film element.

First, a substrate 13 constituting a lower layer of a dielectric thin film element and a platinum film 14 as a lower electrode formed thereon were prepared as follows.

On the single-crystal silicon plate 15, as a buffer layer, the surface of the silicon plate 15 is forcibly oxidized to prevent silicon from diffusing into the platinum film 14 serving as the lower electrode. Was formed. On top of that, an aluminum oxide film 17 was formed by 1000 Å sputtering to improve the adhesion between the silicon plate 15 and the platinum film 14.

A platinum film 14 as a lower electrode was formed by sputtering 300 Å on a substrate 13 composed of the silicon plate 15, the silicon oxide film 16, and the aluminum oxide film 17 thus formed. .

Next, on this platinum film 14, a dielectric thin film 18 composed of ultrafine metal oxide particles having an average particle size of 15 to 50 nm of the present invention was formed.

On this, a platinum electrode 19 was provided as an upper electrode by sputtering. Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

(Example 1)

In the following examples, a method for preparing an ultrafine particle dispersion solution of barium titanate, which is used when preparing the metal oxide ultrafine particle thin film of the present invention, and a barium titanate ultrafine particle thin film produced by the dispersion solution are described. This will be described specifically for an example.

First, as a preparation of the raw material alkoxide solution, 4 g of palladium isopropoxide was mixed and dissolved in a mixed solvent of 160 ml of isopropyl alcohol and 40 ml of benzene in a glove box in an Ar atmosphere. After a barium alkoxide solution, an equimolar titanium isopropyloxide solution was added dropwise thereto and mixed overnight to obtain a pale yellow transparent raw material solution of a barium-titanium composite alkoxide.

When producing a composite metal alkoxide, it is preferable to use an alcohol corresponding to the type of the metal alkoxide.

Next, the WZO microemulsion solution contains cyclohexane as a dispersion medium and NP-10 as a surfactant: (p-C9H19) -C6H4-O- (CH2CH2O) 10CH2CH20H Water: 1-octanol: NP-10: cyclohexane = 0.2: 9: 7.5: 150 while publishing with Ar gas using 1-octanol as a cosurfactant The mixture was mixed at a ratio of 1 to obtain a W / O microemulsion solution.

The barium-titanium composite alkoxide is added to the prepared microemulsion solution so that the amount of water in the microemulsion becomes 0.95 times, 1.2 times, and 3 times the amount of water required for hydrolysis of the barium-titanium composite alkoxide. The solutions were each fractionated using a micropip, and introduced into each microemulsion solution using a tube pump.

As it was 1, stirring and mixing were performed in a glove box in an Ar atmosphere to obtain a dispersion solution of barium titanate ultrafine particles.

The resulting dispersion of ultrafine particles of barium titanate is light-brown and transparent, and is hydrolyzed. It was confirmed that the generated barium titanate ultrafine particles were highly dispersed.

Further, a part of the dispersion solution was collected, precipitated by adding acetone, centrifuged, and then the crystal phase of the sample washed with an organic solvent was re-identified by powder X-ray diffraction. It was confirmed that it was a single phase of crystallized Z-palladium titanate.

Observation of the particle shape with a high-resolution SEM revealed that the particles were very fine, about 8 nm, and had a uniform particle size distribution.

Next, using the obtained dispersion solution of ultrafine fine particles of barium titanate, an attempt was made to produce a thin film of ultrafine fine particles of barium titanate by spin coating.

According to the powder X-ray diffraction results and the SEM observation results, the ultrafine particle dispersion solution is highly dispersed in crystallized ultrafine particles of about 8 nm. It was found to have applicability.

In addition, the ultrafine particle dispersion solution can freely adjust the concentration of the ultrafine particles in the liquid by adding an organic dispersion medium occupying a volume ratio of about 90% by partially evaporating with an evaporator or the like, or conversely. Can be adjusted.

After spin coating was performed using a barium titanate ultrafine particle dispersion solution having a concentration of 0.07 mol I1, heat treatment was performed at 450 ° C. in air to obtain a barium titanate ultrafine particle thin film.

The SEM photograph of the surface of the barium titanate ultrafine particle thin film confirmed that ultrafine particles of parium titanate of about 1 Onm were formed at a high density.

Furthermore, it was confirmed that a similar high-density thin film with grain growth of about 20 nm could be obtained by heat treatment at 600 ° C.

(Example 2)

While bubbling with Ar gas, water: 1-octanol: NP-4: cyclohexane = 0.2: 9: 7.5: 150 was mixed to obtain a WZO microemulsion solution. .

Next, a palladium-titanium composite alkoxide solution prepared in the same manner as in Example 1 was added to these two microemulsion solutions so that the water amount of the microemulsion was three times the water amount required for hydrolysis of the alkoxide raw material. Of the microemulsion solution and introduced into each microemulsion solution using a tube pump.

The mixture was stirred and mixed for 1 day in a glove box under an Ar atmosphere to obtain a dispersion solution of barium titanate ultrafine particles.

(Comparative Example 1)

In the same manner as in Example 1, a barium-titanium composite alkoxide solution and Adjustment of the solution was performed.

Using the prepared microemulsion solution, use a micropipet with a barium-titanium composite alkoxide solution such that the amount of water in the microemulsion is five times the amount of water required for hydrolysis of the barium-titanium composite alkoxide. The fractions were collected and introduced into each of the mic mouth emulsion solutions using a tube pump.

The mixture was stirred and mixed for 1 day in a glove box in an Ar atmosphere to obtain a dispersion of ultrafine particles of barium titanate.

(Comparative Example 2)

While bubbling with Ar gas, the mixture was mixed at a ratio of water: 1-octanol: NP-10: cyclohexane = 5: 9: 7.5: 150 to obtain a WZO microemulsion solution.

Using the prepared microemulsion solution, a barium-titanium composite alkoxide solution was added to each of the prepared microemulsion solutions using a micropipet so that the amount of water in the microemulsion was 50 times the amount of water required for the hydrolysis of the barium-titanium composite alkoxide. It was separated and introduced into each microemulsion solution using a tube pump.

(Comparative Example 3)

A barium-titanium composite alkoxide solution is added to the prepared microemulsion solution using a micropipet so that the amount of water in the microemulsion becomes 0.75 times the amount of water required for hydrolysis of the barium-titanium composite alkoxide. , And introduced into each microemulsion solution using a tube pump.

(Comparative Example 4)

The barium acetate powder was dissolved in water to prepare a 0.1 mo I / I barium acetate aqueous solution. The adjusted barium acetate aqueous solution: 1-octanol: NP-10: cyclohexane = 5: 9: 7.5: 150 was mixed to obtain a W / O microemulsion solution.

To this, an equivalent amount of titanium isopropoxide was added dropwise using a micropipette.

The mixture was stirred and mixed in a glove box in an Ar atmosphere to obtain a titanic acid / lithium ultrafine particle dispersion solution.

(Comparative Example 5) While performing bubbling with Ar gas, water / NP-4: cyclohexane = 5: 7.5: 150 were mixed respectively to obtain a W / O microemulsion solution.

Next, a barium-titanium composite alkoxide solution prepared in the same manner as in Example 1 was added to the microemulsion solution so that the amount of water in the microemulsion was 50 times the amount of water required for hydrolysis of the alkoxide raw material. The solution was collected by a pipette and introduced into each microemulsion solution using a tube pump.

As it was 1, stirring and mixing were performed in a glove box in an Ar atmosphere to obtain a dispersion of ultrafine particles of barium titanate.

Table 1 shows the dispersion state and crystal phase of the obtained barium titanate ultrafine particle dispersion solution.

In Table 1, the evaluation of the dispersion state is a visual evaluation, where ◎ indicates a completely transparent state, 〇 indicates a transparent state, indicates a cloudy state, and X indicates a state where precipitation has occurred. and that _c first, by using the raw material solution was combined alkoxide of the produced by adjusting the W / O micro Emar Ji below 3 times 0.9 5 times more water necessary for hydrolysis of the raw material solution Gyotsu Examples of the dispersion solution of ultrafine particles of barium titanate are shown in Examples 1 and 2.

In this way, by making the amount of water 0.95 times or more and 3 times or less the amount of water required for alkoxide hydrolysis, the aggregation of the composite metal oxide ultrafine particles generated after the reaction is suppressed, and the highly dispersed transparent A complex metal oxide ultrafine particle dispersion solution can be obtained.

The generated ultrafine particles are very fine, have a uniform composition, and have a uniform particle size and shape and are crystallized single-phase ultrafine particles of a composite metal oxide. On the other hand, when the amount of water is larger than that, as shown in Comparative Example 1, the generated ultrafine particles aggregate and precipitate.

When the amount of water further increases by 50 times, sedimentation due to aggregation occurs. .

Also, it was found that when the water content was 0.75 times, the hydrolysis was not sufficiently performed, so that an amorphous phase was generated in the ultrafine particles.

In Comparative Examples 2 and 5, in addition to the barium titanate phase, a barium carbonate phase was confirmed by powder X-ray diffraction, and when the solubility of the constituent elements of the composite metal oxide in water was high, some were found. Since it remains in water, composition deviation and reduction in composition uniformity occur.

Further, when the complex alkoxide conversion of the raw material was not performed, as shown in Comparative Example 4, an amorphous phase was obtained after the reaction, and was not crystallized.

In addition, as a result of powder X-ray diffraction, the sample subjected to heat treatment after centrifugation and washing was confirmed to be composed of a BaTi03 phase and a BaTi204 phase, and was found to be in excess of titanium.

That is, in this case, it is considered that titanium was excessive due to the removal of barium remaining in the water at the time of washing, and not only a crystal phase could not be obtained, but also a problem in terms of composition deviation and uniformity. It becomes.

Next, examples of the metal oxide ultrafine particle thin film of the present invention will be described.

(Examples A to C) In the following examples, the ultrafine particle thin film of barium titanate produced by using the dispersion solution of barium titanate synthesized by the microemulsion described above will be specifically described.

First, as a preparation of the raw material alkoxide solution, 4 g of barium isopropoxide was mixed and dissolved in a mixed solvent of isopropyl alcohol (160 ml) and benzene (40 ml) in a glove box in an Ar atmosphere, and dissolved in a barium alkoxide solution. After that, an equimolar titanium isopropoxide solution was added dropwise thereto and mixed overnight, to obtain a pale yellow transparent raw material solution of a composite powder of a barium-titanium composite alkoxide.

Next, the W / O microemulsion solution was prepared using cyclohexane as the dispersion medium and N P-10 as a surfactant: (p-C9H19) -C6H4-0- (CH2CH20) While bubbling with Ar gas using octanol, water: octanol: NP-10: mix mouth hexane = 0.2: 9: 7.5: 150 and mixed with WZO microemulsion solution. did.

The barium-titanium composite alkoxide solution was introduced into the microemulsion solution so that the amount of water in the microemulsion was adjusted to 1.5 times the amount of water required for hydrolysis of the lium-titanium composite alkoxide. The mixture was stirred and mixed in a glove box in an Ar atmosphere to obtain a dispersion solution of ultrafine particles of barium titanate. It was confirmed by TEM observation that the titanium titanate in the dispersion solution was crystallized fine nanoparticles of about 8 nm.

Next, using the obtained dispersion solution of ultrafine particles of barium titanate, spin-coating is applied several times onto a Si / Si02 / AI203 / Pt substrate described below and heat-treated at 450 ° C in air. After that, heat treatment was performed at 600 ° C to 900 ° C in an RTA furnace, and Examples A to C having average particle diameters of 15.2 nm, 19.6 nm, and 48.9 nm, respectively. A barium titanate ultrafine particle thin film was obtained.

That is, Example A is a barium titanate ultrafine particle thin film having an average particle size of 15.2 nm subjected to heat treatment at 600 ° C., and Example B is an average particle size Example C is a barium titanate ultrafine particle thin film having an average particle size of 48.9 nm, which was heat-treated at 900 ° C.

The average particle size of the obtained ultrafine particle of barium titanate was determined from a digitizer measurement of 100 particles from a SEM photograph of the surface of the thin film, and obtained from the average.

FIG. 6 is a particle size distribution diagram showing the particle size distribution of Example B.

This particle size distribution is obtained by measuring the particle size of arbitrary 100 particles from an SEM photograph and calculating the standard deviation (σ) from the distribution.

As can be seen from FIG. 6, the standard deviation (b) at 800 ° C. and the average particle size of the heat treatment temperature at 19.6 nm is as narrow as 1.21.

It was also found that the standard deviation (σ) of Examples I and C was as narrow as 1. 24-1.3.33.

In addition, SEM observation and SPM observation confirmed that a dense nanoparticle thin film with small surface roughness was obtained.

FIG. 7 shows an S-photograph of Example II.

Further, XRD measurement confirmed that the thin film was a crystalline titanic acid / cream single phase. For the evaluation of electrical characteristics, an upper electrode was fabricated by Pt sputtering on the surface of the obtained barium titanate nanoparticles, and the relative permittivity and dielectric loss at room temperature and a measurement frequency of 1 kHz were measured with an LCR meter. The ferroelectricity was evaluated by hysteresis measurement.

In addition, the withstand voltage was evaluated by using the sample used for dielectric loss measurement, applying a current from the electrode and applying 200 kV / cm to the sample. If not, it was marked as 〇.

Figure 8 shows the configuration of the sample used for the evaluation of the electrical characteristics.

On the substrate, Si 02 is laminated on Si as an insulating layer, and AI 203 is laminated as a buffer layer. Further, the above-mentioned SiZSi02 / AI203 / Pt substrate 20 on which Pt21 was laminated as a lower electrode was used.

On this S i / S i 02 / AI 203 Pt substrate 20, spin-coating film formation and heat treatment were used to form a lithium titanate ultrafine particle thin film 22, and a 0.5 φ Pt 23 was used as the upper electrode. Was formed by sputtering to prepare a sample.

(Comparative Example A)

A dispersion of ultrafine particles of barium titanate was obtained in the same manner as in Example A.

Next, the obtained barium titanate ultrafine particle dispersion solution was spin-coated on a Si ZSi 02ZA I 203 / Pt substrate several times, and heat-treated at 300 ° C in air. Thereafter, heat treatment was performed in an RTA furnace at 500 ° C. to obtain an ultrafine particle of parium titanate ultrafine particles of Comparative Example A having an average particle size of 12.6 nm.

The obtained barium titanate ultrafine particle thin film was confirmed to be a dense nanoparticle thin film having a small surface roughness according to the observations of 3 31 \ 1 and 31 \ 1.

Also, XRD measurement confirmed that the thin film was a single phase of barium titanate. (Comparative Examples B and C) After obtaining a raw material solution of a barium-titanium composite alkoxide in the same manner as in Example A, directly on a SiZSi02 / AI203 / Pt substrate by spin coating in a dry atmosphere. And dried at 120 ° C. for 15 minutes.

After repeating this spin coating and drying several times, heat treatment was performed at 500 ° C and 700 ° C in an RTA furnace, and Comparative Example B having average particle diameters of 33.2 门 0! And 45.6 nm, respectively. And C were obtained.

That is, Comparative Example B was an ultrafine fine particle of barium titanate having an average particle diameter of 33.2 nm that had been subjected to heat treatment at 500 ° C, and Comparative Example C had an average particle diameter of 450 that had been heat treated at 700 ° C. . 6 nm ultra-fine particle of barium titanate.

As a result of SEM observation and SPM observation of the obtained ultrafine particle of barium titanate, the surface roughness was larger than that of the thin film surface prepared in Example A, and many gaps were observed between the particles. It was also confirmed that the compactness was small.

According to the XRD measurement, the thin film that had been heat-treated at 500 ° C. had only a halo peak and was not crystallized.

In addition, although the thin film subjected to the heat treatment at 00 ° C. was confirmed to have a peak due to titanium titanate, a halo peak was also observed, indicating that an amorphous phase was included.

(Comparative Example D)

For the preparation of the raw material alkoxide solution, 4 g of barium isopropoxide was mixed and dissolved in 200 ml of 2-methoxyethanol in a glove box under an Ar atmosphere. After making a lucoxide solution, an equimolar titanium ispropoxide solution was added dropwise and mixed overnight to obtain a barium-titanium composite alkoxide raw material solution.

The resulting solution was aged for 3 days while stirring in the presence of steam to produce a partially hydrolyzed raw material solution.

Using this raw material solution, spin-coating is applied several times on SiZSi02 / AI203 / Pt substrate, heat-treated at 450 ° C in air, and then filtered. Heat treatment was performed at 00 ° C. to obtain a barium titanate ultrafine particle thin film having an average particle size of 48.9 nm.

Table 2 shows the surface state, dielectric properties, and crystal phase of the obtained ultrafine particle of barium titanate. Table 3 shows the relative permittivity, dielectric loss, and residual polarization P r X of each sample at room temperature. 2 is shown. Table 2

Table 3

First, film formation was performed using a transparent raw material solution in which barium titanate ultrafine particles synthesized by the microemulsion (ME) method were maintained in a highly dispersed state, and then the particles were grown by heat treatment to reduce the average particle diameter to 15%. Ultrafine particulate titanium titanate thin films tuned to ~ 50 nm are shown in Examples A-C.

As described above, the film is formed from the metal oxide ultrafine particle dispersion maintained in a highly dispersed state. Therefore, even if it is a nanoparticle, it becomes a homogeneous and dense thin film, and since it has already been well crystallized, the surface roughness will increase greatly due to the reaction even after heat treatment, and cracks will be formed. Is not significantly reduced, but rather, heat treatment is performed to grow fine nanoparticles, so that densification and crystallization are further promoted.

In addition, electrical characteristics have been sufficiently obtained.

Therefore, in the barium titanate ultrafine particle thin film composed of particles grown upright to an average particle diameter of 15 nm or more, as can be seen from the hysteresis curve of Example B in FIG. 9, 2 Pr> 2.0〃. CZ cm2 shows ferroelectricity and a dielectric constant of 300 or more is obtained.

In addition, a thin film device using such a thin film as a device has a good dielectric property with a dielectric loss of less than 4%.

Also, the withstand voltage is preferably 200 kV cm or more, which is preferable.

On the other hand, in Comparative Example A having an average particle diameter of 15 nm or less, ferroelectric properties were not obtained at 2 Pr <2.0〃CZ cm2, and the relative dielectric constant was 300 or less. No ferroelectric characteristics were obtained.

Next, as shown in Comparative Examples B and C, when a film was formed by a general sol-gel method, there was a problem in crystallinity, and in Comparative Example C where heat treatment was performed at 500 ° C. It is an amorphous phase.

Also, it was not possible to measure electricity.

Even in Comparative Example B, which was heat-treated at 700 ° C., the crystallinity was poor, and although some still contained an amorphous phase, the crystallized barium titanate was formed. The cracks were observed in some places and the film quality was greatly reduced.

Also, because of a crack or a large leakage current, a dielectric hysteresis curve cannot be obtained, or because the amorphous phase reacts with the substrate to form a low dielectric constant intermediate phase, The rate also decreased to less than 300.

As a result, it was found that the dielectric loss was large and the withstand voltage was not sufficiently obtained.

Furthermore, in the case of Comparative Example D, in which a film was formed using a raw material solution that had been partially hydrolyzed in advance by the sol-gel method, the reaction volume after film formation was reduced, or slight improvement in surface roughness was observed. Both become barium titanate single phase after heat treatment at 700 ° C, but the dispersion and crystallinity of nanoparticles generated by partial hydrolysis are still not enough, as shown in Examples A to C. The dielectric loss is large and the relative dielectric constant is as small as 300 or less, probably because the surface roughness is larger than that of the thin film and the low dielectric constant phase is included as in Comparative Examples B and C. became. Industrial applicability

As described above, the metal oxide ultrafine particle dispersion according to the present invention, and the metal oxide ultrafine particles The element thin film is useful as a thin film part of an electronic device such as a multilayer capacitor actuator, and is particularly suitable for use in a thin film part of an electronic device that requires both miniaturization and ferroelectric characteristics.

Claims

The scope of the claims

1-A metal oxide ultrafine particle dispersion prepared by hydrolyzing a raw material in a microemulsion containing a dispersion medium which is a hydrophobic body, water and a surfactant, wherein the raw material is a plurality of fine particles. It consists of a complex metal alkoxide solution in which metal alkoxide is mixed in alcohol to form a complex, and the amount of water contained in the microemulsion is 0.95 times or more and 3 times or less of the amount of water required for hydrolysis of the raw material. A metal oxide ultrafine particle dispersion solution, characterized in that:

2. The metal oxide according to claim 1, wherein at least one of the plurality of metal alkoxides is a barium alkoxide, and the composite metal alkoxide solution contains a polymerization inhibitor that suppresses polymerization of the barium alkoxide. Ultrafine particle dispersion solution.

3. A metal oxide ultrafine particle thin film obtained by using the metal oxide ultrafine particle dispersion solution according to claim 1 or 2.

4. Consisting of ultrafine metal oxide particles with an average particle size of 15 nm or more and 50 nm or less, having a remanent polarization (P r) of 2 Pr or more with a ferroelectric property of 2 C cm2 or more. A metal oxide ultrafine particle thin film having a relative dielectric constant at 1 kHz of 300 or more.

5. The ultrafine metal oxide thin film according to claim 4, wherein the ultrafine metal oxide particles are perovskite-type oxides containing titanium and barium.