JP2001262357A - Composition for deposition of rare earth oxide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for deposition an excellent rare earth oxide film even on a nonconducting substrate by a simplified operation without requiring large-scale installations, such as a vacuum pumping system and a heating furnace. SOLUTION: A composition for deposition of rare earth oxide film, composed of an aqueous solution in which a rare earth compound is dissolved and at least one anion selected from nitrate ions and nitrite ions and a reducing agent are contained, is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a composition for forming a rare earth oxide film, a method for forming a rare earth oxide film, and a rare earth oxide film.

[0002]

2. Description of the Related Art Conventionally, as a method for forming an oxide film of a rare earth element such as cerium, terbium, yttrium, europium, etc., dry methods such as a CVD method, an evaporation method and a sputtering method, a spray pyrolysis method, a sol-gel method, Attempts have been made to form a film on a substrate by a wet method such as a phase growth method. Among them, according to the sputtering method, a film can be formed at a lower temperature and a uniform film can be formed as compared with other methods. Therefore, most of rare earth oxide films are currently manufactured by this method. However, in a dry method such as a sputtering method, a CVD method, a vapor deposition method, or the like, when forming a film, the pressure in the film forming chamber is reduced or gas is mixed.
Processing such as heating of the substrate is required, and a large-scale manufacturing apparatus including a vacuum exhaust device, a substrate heating device, a high-frequency power supply, and the like is required. Moreover, in these methods, the film formation rate is low, the composition and the film thickness are difficult to control, the area of the substrate that can be used is limited, and it is difficult to form a uniform film on a substrate having a complicated shape. There are disadvantages.

Further, in the spray pyrolysis method or the sol-gel method, it is necessary to heat the substrate at 300 to 900 ° C. after forming the film on the substrate, so that a heating furnace is required and the usable substrate material is limited.

[0004] In order to make the rare earth oxide film usable in a wide range, large-scale equipment such as a vacuum evacuation device and a heating furnace is not required, and the film can be formed on a substrate having a large area and a complicated shape. It is desired to develop a method of forming a rare earth oxide film which has a high film forming rate, a uniform film thickness and a uniform composition, and which can be easily controlled.

[0005]

SUMMARY OF THE INVENTION The main object of the present invention is to:
An object of the present invention is to provide a method capable of forming a good rare earth oxide film on a non-conductive substrate by a simple operation without requiring a large-scale facility such as an evacuation apparatus and a heating furnace.

[0006]

Means for Solving the Problems As a result of intensive studies in view of the above problems, the present inventor has found that an aqueous solution in which a rare earth compound is dissolved contains at least one selected from nitrate ions and nitrite ions. When an anion and a reducing agent are contained, simply immersing the substrate in this aqueous solution, regardless of the type of the substrate such as a conductive substrate or a non-conductive substrate, a large area shape The inventors have found that a rare earth metal oxide film having a uniform thickness and composition can be formed on a complicated base material, and have completed the present invention.

That is, the present invention provides the following composition for forming a rare earth oxide film, a method for forming a rare earth oxide film, and a rare earth oxide film. 1. A composition for forming a rare earth oxide film, wherein the composition is an aqueous solution in which a rare earth compound is dissolved, the aqueous solution containing at least one anion selected from nitrate ions and nitrite ions and a reducing agent. 2. Item 2. The composition for forming a rare earth oxide film according to Item 1, wherein the rare earth compound is a water-soluble compound containing at least one rare earth element selected from cerium, yttrium, terbium, and europium. 3. Item 3. The composition for forming a rare earth oxide film according to Item 1 or 2, wherein the reducing agent is at least one selected from borane-amine complex, potassium borohydride, sodium hypophosphite, and hydrazine. 4. 4. A method for forming a rare earth oxide film, comprising immersing a substrate in the composition for forming a rare earth oxide film according to any one of the above items 1 to 3. 5. Item 5. A rare earth oxide film formed on a substrate by the method of the above item 4.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The composition for forming a rare earth oxide film of the present invention is an aqueous solution in which a rare earth compound is dissolved, and contains at least one anion selected from nitrate ion and nitrite ion and a reducing agent. Solution.

In the composition of the present invention, a water-soluble compound containing a rare earth element such as cerium, terbium, yttrium and europium can be used as the rare earth compound. Examples of the kind of the water-soluble compound include nitrate, nitrite, sulfate, oxalate, acetate, carbonate, chloride, fluoride, iodide and the like. These rare earth compounds can be used alone or in combination of two or more.

The concentration of the rare earth compound in the composition of the present invention is not particularly limited, but may be 0.0001 mol / l to 0.5 mol / l.
mol / l is preferable, and 0.001 to 0.1 mol
/ L is more preferable. If the rare earth compound concentration is too low, it is difficult to form a rare earth oxide film,
On the other hand, if the concentration is too high, a hydroxide is easily formed, which is not preferable.

Further, the composition of the present invention needs to contain at least one anion selected from nitrate ions and nitrite ions. The presence of these anions in the composition of the present invention makes it possible to form a rare earth oxide film by a method of immersing a substrate in the composition.

The content of at least one anion selected from nitrate ion and nitrite ion is not particularly limited, but is usually 0.0001 mol as anion concentration.
It is preferably in the range of about 1 / l to 1 mol / l, and more preferably in the range of about 0.001 mol / l to 0.1 mol / l.

In the composition of the present invention, in order for at least one anion selected from nitrate ion and nitrite ion to be present in the aqueous solution, a compound serving as a nitrate ion source and a compound serving as a nitrite ion source are usually used. At least one compound selected from the above may be dissolved in water as a solvent.

As a compound serving as a nitrate ion source, nitric acid, water-soluble nitrate and the like can be used. Specific examples of the nitrate include ammonium nitrate, sodium nitrate, potassium nitrate, lithium nitrate, urea nitrate and the like.

As a compound serving as a nitrite ion source, a water-soluble nitrite can be used, and specific examples thereof include potassium nitrite and sodium nitrite.

The compound serving as a nitrate ion source and the compound serving as a nitrite ion source can be used alone or in combination of two or more.

When a rare earth element nitrate or a rare earth element nitrite is used as the rare earth compound, the nitrate or nitrite itself serves as a nitrate ion source or a nitrite ion source. And a compound serving as a nitrite ion source may not be blended. In this case, an unnecessary component does not exist in the bath, and a highly pure rare earth oxide film can be formed.

When a rare earth element nitrate or a rare earth element nitrite is used, the concentration of the rare earth compound and the concentration of at least one anion selected from nitrate ion and nitrite ion should be within the above-mentioned preferred ranges. As such, other rare earth compounds or compounds serving as anion sources may be further added.

Although the reducing agent used in the present invention is not particularly limited, dimethylamine borane (DMAB), which is widely used as a reducing agent for electroless plating, in consideration of the stability of the aqueous solution and the like. And borane-amine complexes such as trimethylamine borane (TMAB); borohydride compounds such as sodium borohydride and potassium borohydride; sodium hypophosphite; and hydrazine. The reducing agents can be used alone or in combination of two or more. By blending the reducing agent, it is possible to form a rare earth oxide film only by immersing the base material in the composition of the present invention without applying electricity.

The content of the reducing agent is not particularly limited. When the amount of the reducing agent is too small, the stability of the aqueous solution is improved, but the deposition rate of the oxide film is slowed down. When the amount is too large, in addition to the difficulty in dissolving, when heated, the stability of the bath is lowered and precipitation is liable to occur. For this reason, the content of the reducing agent is 0.1.
It is preferably in the range of about 001 mol / l to 0.5 mol / l, and 0.005 mol / l to 0.1 mol.
More preferably, it is within the range of about 1 / l.

According to the composition of the present invention comprising an aqueous solution containing each of the above components, a desired rare earth oxide film can be formed only by immersing various substrates in the composition. The liquid temperature at this time is preferably about 40 to 90 ° C, more preferably about 60 to 70 ° C. Also, the pH of the solution
Is not particularly limited, but if the pH is too low, the bath stability is improved, but the film forming rate is greatly reduced, while if the pH is too high, the film forming rate is improved,
The stability of the bath decreases, and precipitates are easily formed in the bath,
It becomes difficult to obtain an oxide film. From these points, the pH of the composition of the present invention is preferably set to about 4 to 7.

When the substrate is immersed in the composition of the present invention, the composition may be either unstirred or stirred, and a known stirring method can be applied as appropriate. Since the thickness of the oxide film to be formed increases with the immersion time, an oxide film having a desired thickness can be formed by appropriately setting the immersion time.

After forming an oxide film by such a method, if necessary, ordinary post-treatment such as washing with water and drying may be performed.

In the present invention, the type of the substrate for forming the rare earth oxide film is not particularly limited, and may be either a conductive material or a non-conductive material, and may be immersed in the composition of the present invention. Any material can be used as long as the material does not change in quality. Specific examples thereof include metal materials such as copper, iron, and aluminum, conductive glasses such as NESA glass and ITO glass, non-conductive glass materials such as ordinary soda lime glass, non-alkali glass (Corning 1737 glass), and ceramics. Materials, plastics materials and the like.

In the case where glass, ceramics, plastics, or the like is used as the base material, or in the case where a metal material that hardly causes a reaction for forming a rare earth oxide film is used, the electroless plating film is required before immersion in the composition of the present invention. May be performed to provide a catalytic metal such as palladium, silver, iron, cobalt, nickel, or platinum used for forming the catalyst. As a specific method of applying the catalyst, any of the known methods similar to the method of applying the catalyst when forming the electroless plating film can be applied. Generally, a method of applying palladium is widely performed, for example, a sensitizing-activation method,
A catalyst may be applied to the substrate surface by a catalyst-accelerator method, an alkaline catalyst method, or the like.

[0026]

According to the composition for forming a rare earth oxide film of the present invention, a rare earth oxide film can be formed by a simple operation of immersing a substrate in the composition. It is possible to form a rare-earth oxide film using a simple apparatus such as an electroless plating apparatus widely used industrially, without requiring a large-scale apparatus such as the above. Further, according to the composition of the present invention, a rare-earth oxide film can be easily formed on any of a conductive substrate and a non-conductive substrate, and even on a substrate having a large area or a substrate having a complicated shape. An oxide film having a uniform thickness and composition can be formed, and its control is easy.

The formed rare earth oxide film can be widely used for various uses such as a magnetic material, a ferroelectric material, a battery material, and a catalyst.

[0028]

EXAMPLES The present invention will be further described below with reference to Examples and Comparative Examples. Examples 1 to 6 and Comparative Examples 1 to 4 A composition for forming a cerium oxide film composed of an aqueous solution containing each component shown in Tables 1 and 2 below was prepared. The amount of each component in these compositions is shown in mol / l.

[0029]

[Table 1]

[0030]

[Table 2]

An alkali-free glass (Corning 1737) was used as a substrate, and immersion degreasing (Aesculin A-220)
(Trademark: Degreasing agent, manufactured by Okuno Pharmaceutical Co., Ltd.) After immersing in a 50 g / l aqueous solution at 50 ° C. for 5 minutes, sensitizing (Sensitizer 100 ml / l, manufactured by Okuno Pharmaceutical Co., Ltd.)
The catalyst was applied to the substrate surface by immersion in an aqueous solution for 1 minute at room temperature and activation (immersion in an activator manufactured by Okuno Pharmaceutical Co., Ltd. at 100 ml / l for 1 minute at room temperature). Next, the cerium oxide film was deposited by immersing the substrate in each composition for 30 minutes at the bath temperature shown in Tables 1 and 2.

The type of the obtained oxide film was examined by the X-ray diffraction method, and the result is shown in Table 3 below. When the compositions of Comparative Examples 1 to 4 were used, a film could not be formed.

[0033]

[Table 3]

From the above results, it can be seen that a cerium oxide film can be obtained by immersing the substrate in the compositions of Examples 1 to 6. Examples 7 to 12 and Comparative Examples 5 to 8 Yttrium oxide film-forming compositions comprising aqueous solutions containing the components shown in Tables 4 and 5 below were prepared. The amount of each component in these compositions is shown in mol / l.

[0035]

[Table 4]

[0036]

[Table 5]

Other than using these compositions, Examples 1 to
6 and alkali-free glass (Corning 173)
7) An yttrium oxide film was formed thereon.

The results of examination of the type of the obtained film by X-ray diffraction are shown in Table 6 below. When the compositions of Comparative Examples 5 to 8 were used, a film could not be formed.

[0039]

[Table 6]

From the above results, it can be seen that a cerium oxide film can be obtained by immersing the substrate in the compositions of Examples 7 to 12. Examples 13 to 18 and Comparative Examples 9 to 13 A composition for forming a terbium oxide film composed of an aqueous solution containing each component shown in Tables 7 and 8 below was prepared. The amount of each component in these compositions is shown in mol / l.

[0041]

[Table 7]

[0042]

[Table 8]

Other than using these compositions, Examples 1 to
6, alkali-free glass (Corning 173)
7) A terbium oxide film was formed thereon.

The type of the obtained film was examined by X-ray diffraction, and the results are shown in Table 9 below. When the compositions of Comparative Examples 9 to 13 were used, a film could not be formed.

[0045]

[Table 9]

From the above results, it can be seen that a terbium oxide film can be obtained by immersing the substrate in the compositions of Examples 13 to 18. Examples 19 to 24 and Comparative Examples 14 to 17 Europium oxide film-forming compositions comprising aqueous solutions containing the components shown in Tables 10 and 11 below were prepared. The amount of each component in these compositions is mol / l
Indicated by

[0047]

[Table 10]

[0048]

[Table 11]

Except for using these compositions,
6, alkali-free glass (Corning 173)
7) A europium oxide film was formed thereon.

The results of examination of the type of the obtained film by X-ray diffraction are shown in Table 12 below. When the compositions of Comparative Examples 14 to 17 were used, a film could not be formed.

[0051]

[Table 12]

From the above results, it can be seen that a europium oxide film can be obtained by immersing the substrate in the compositions of Examples 19 to 24.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Junichi Katayama 47-13 F-term (reference) 4G076 AA02 AB04 AB07 AB08 BA11 CA10 4K022 AA03 AA04 AA13 BA15 BA28 BA33 CA06 CA07 CA19 CA20 CA21 DA01 DB02 DB03 DB04 DB05

Claims (5)

[Claims] An aqueous solution in which a rare earth compound is dissolved,
A composition for forming a rare earth oxide film, which is an aqueous solution containing at least one anion selected from nitrate ions and nitrite ions and a reducing agent. 2. The method according to claim 1, wherein the rare earth compound is cerium, yttrium,
The composition for forming a rare earth oxide film according to claim 1, which is a water-soluble compound containing at least one rare earth element selected from terbium and europium. 3. The composition for forming a rare earth oxide film according to claim 1, wherein the reducing agent is at least one selected from a borane-amine complex, a borohydride compound, sodium hypophosphite and hydrazine. . 4. A method for forming a rare earth oxide film, comprising immersing a base material in the composition for forming a rare earth oxide film according to claim 1. 5. A rare earth oxide film formed on a substrate by the method of claim 4.