JP2000026121A - Production of thin film of complex lead oxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily produce a thin film of APbO3 (where A is at least one of Ba or Sr) as an electrically conductive material on various substrates over a wide area without requiring high temp. treatment necessary for the conventional paste process or for the formation of a thin film by the thermal decomposition reaction of a mixture of organometallic compds. or requiring facilitates and steps of electrolysis, etc. SOLUTION: A substrate with a perovskite type oxide on the surface, a substrate with Ti or Ti oxide on the surface or a substrate with Pb or Pb oxide on the surface is heated in an aq. alkali soln. contg. A ions (A is at least one of Ba or Sr) and Pb ions to form the objective thin film of APbO3 on the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a nonvolatile memory.
For electronic devices such as capacitors and capacitors, as well as light modulation devices
Conductive thin film used for electrodes or resistors used
APbO as a membrane _Three(A is less of Ba or Sr
And 1) a method for forming a thin film.

[0002]

2. Description of the Related Art BaPbO ₃ , SrPbO _{3 and the} like are metal oxide conductors having a perovskite structure. Among them, BaPbO ₃ has an electric resistance at room temperature of 0.3 to 0.8 mΩ.
In cm, the temperature coefficient of electric resistance is as small as about 0.1% / ° C., showing good conductivity from extremely low temperatures to several hundred degrees Celsius. Furthermore, the reactivity with barium titanate and lead titanate is low,
The problem with conventional oxide electrodes is that the ferroelectric properties deteriorate due to the formation of a reaction phase between the ferroelectric element and the electrode material during firing, or the conductivity of the electrode material itself deteriorates. And has the advantage that it can be used as a base electrode material for a thin film.

Conventionally, thin-film electrodes and heating resistors used for various electronic parts have been formed by a vapor phase method such as an electron beam evaporation method or a sputtering method. On the other hand, an organic metal method (MOD) or a paste method has been used for forming a conductive thick film such as an electrode and a heating resistor. However, the former has problems such as equipment cost, composition control of the thin film, enlargement of the area, and the latter has problems such as film quality and thinning. Among these, Pd, Ag, Pd-Ag, and Pt are preferred in the latter paste method, which is excellent in equipment cost, thin film composition control, large area, and the like.
Pd, Ag, Pd-A by applying a mixture of a noble metal powder such as a binder, a solvent, and a glass frit to a substrate, and baking the mixture.
Noble metal thick films such as g and Pt are produced. However, while these noble metal films are resistant to oxidation, their cost is extremely high. For this reason, Japanese Patent Application Laid-Open No. 61-225711 describes that a conductive oxide such as BaPbO ₃ is formed by a paste method, but the paste method is not suitable for an electronic element requiring a thin film. .

For this reason, a method of forming a thin film of BaPbO ₃ has been studied. Japanese Patent Application Laid-Open No. Hei 7-130232 discloses a method of applying a mixture of an organometallic compound to a substrate, thermally decomposing the mixture, and forming a thin film. Is described. However, since this method requires annealing at about 450 to 600 ° C., the type of a substrate on which a thin film is formed is limited.

[0005] BaPbO_ThreeSuch as lead storage
It is also used as a current collector for a pond.
No. 7436 discloses BaP on Pb or Pb alloy.
bO _ThreeA method for forming a thin film is described. However
However, this method requires anodic oxidation,
And equipment such as power supply and electrolysis process are required.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and requires a high-temperature treatment such as a conventional paste method or the formation of a thin film in which a mixture of organometallic compounds is thermally decomposed. Method for producing an easy and inexpensive APbO ₃ thin film (where A is at least one of Ba and Sr), which does not require a wide variety of usable substrates and does not require equipment or processes such as electrolysis. Is to provide.

[0007]

Means for Solving the Problems The inventors of the present invention have studied the conductive thin film, and found that the conductive thin film can be formed on the substrate by reacting in an alkaline aqueous solution containing raw material ions. The present inventors have found that they can do so, and have reached the present invention.

That is, according to the present invention, a substrate having a perovskite-type oxide on its surface is treated with A ions (A is Ba or Sr).
Heat treatment in an alkaline aqueous solution containing at least one of Pb ions and Pb ions to form an AP on a perovskite oxide.
The present invention relates to a method for producing a composite lead oxide thin film, which comprises forming a bO ₃ thin film.

Further, the present invention provides a heat treatment of a substrate having Ti or Ti oxide on a surface thereof in an alkaline aqueous solution containing A ion (A is at least one of Ba and Sr) and Pb ion. The present invention relates to a method for producing a composite lead oxide thin film, comprising forming an APbO ₃ thin film on a Ti oxide.

Further, the present invention provides a substrate having a Pb or Pb oxide on a surface thereof in an alkaline aqueous solution containing A ions (A is at least one of Ba and Sr) and Pb ions, and heat-treating the Pb or Pb oxide. APbO on Pb oxide
_{The present} invention relates to a method for producing a composite lead oxide thin film, characterized by forming _three thin films.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A substrate having a perovskite-type oxide on the surface of the present invention is treated with A ion (A is Ba or S).
r) and a heat treatment in an alkaline aqueous solution containing Pb ions to form an APbO ₃ thin film on the perovskite-type oxide layer. explain.

A group having a perovskite oxide on its surface
Perovskite oxide can be formed as a plate substrate
It is not particularly limited as long as it is an inorganic substance, a metal, an organic substance
Anything is fine. The substrate is a perovskite oxide
It may be itself. In addition, perovskite-type oxidation of the surface
Although the kind of the object is not particularly limited, for example, Ba
TiO_Three, PbTiO_Three, PZT (zirconate titanate)
Lead), PLZT, Pb (Ni_1/3Nb_2/3) O_Three, Pb
(Ni_1/3Nb_2/3) O_Three, Pb (Mg_1/3Nb_2/3) O _Three,
Pb (Zn_1/3Nb_2/3) O_Three, Ba (Zr, Ti) O_ThreeAnd
Each site of the constituent elements is represented by Ba, Ca, Sr, La, Bi,
And Zn, Ni, Mg, Co, W, Nb, Sb, Ta, F
e, substituted products substituted with W, etc., and complexes thereof.
You.

The method for forming these perovskite oxides on a substrate is not limited here, but includes, for example, a sputtering method, a sol-gel method, and a hydrothermal method. The perovskite-type oxide ceramics substrate obtained by the sintering method can be used as it is as a substrate for forming a conductive thin film. If a perovskite oxide is formed by a hydrothermal method, the formation of the APbO ₃ film (A is at least one of Ba and Sr) of the present invention can be performed in an aqueous solution. These perovskite oxide thin films need not be taken out of the reaction system and may be slightly formed as intermediates.

The substrate having the perovskite oxide on its surface is treated with B corresponding to A of the target APbO ₃ film.
a. Put in an alkaline aqueous solution containing at least one of Sr ions and Pb ion and heat. The Ba and Sr compounds to be added to these solutions may be metals, inorganic salts, organometallic compounds, etc., as long as they become Ba and Sr ions in the solution. The Pb compound may be any compound in which Pb ions exist in an aqueous alkaline solution, such as lead hydroxide. The concentrations of Ba, Sr, and Pb in the solution were each 0.1.
The concentration may be 025 mol / l or more, and may be a saturated concentration. If the concentration is low, the reaction will be slow.

In order to prepare an aqueous alkaline solution, a hydroxide of the above-mentioned A ion or NaOH, KOH or the like may be used separately. The stronger the alkali, the easier it will crystallize,
PH12 or more is preferable.

The reaction temperature is from 80 to 400 ° C., preferably from 100 to 200 ° C. If it is too low, the reaction slows down,
If it is too high, it will be high pressure and not practical. An autoclave is used depending on the reaction temperature.

Further, a substrate having Ti or Ti oxide on its surface or a substrate having Pb or Pb oxide on its surface is prepared by using an alkaline aqueous solution containing A ions (A is at least one of Ba and Sr) and Pb ions. A method for forming an APbO ₃ thin film on Ti or a Ti oxide or Pb or a Pb oxide by heat treatment in an atmosphere will be described.

The substrate in this case is not particularly limited, as long as it is stable in the reaction solution, as long as the above-mentioned Ti or Ti oxide, or Pb or Pb oxide is formed on the surface of the substrate. Good. The substrate itself is made of Ti or T
It may be an i-oxide or Pb or a Pb oxide. When used as a piezoelectric element, Ti, Ni, or an alloy thereof is preferable as the substrate in terms of alkali resistance, heat resistance, Young's modulus, and the like.

When a substrate having Ti or Ti oxide on its surface is treated in an aqueous alkaline solution under the same reaction conditions as described above, first, ATiO ₃ (A is Ba or Sr
Is formed, and a perovskite oxide of PbTiO ₃ or a mixture thereof is formed, and an APbO ₃ thin film (A is at least one of Ba and Sr) is formed on the basis thereof.

When a substrate having Pb or Pb oxide on its surface is treated in an alkaline aqueous solution under the same reaction conditions as described above, first, APbO ₃ (A is Ba or Sr
Is formed, and thereafter, each ion is supplied, and the APbO ₃ film (A is at least one of Ba and Sr) grows.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to embodiments.

Example 1 A Ti substrate was placed in an inner container of an autoclave and reacted at 80 ° C. for 4 hours in a 0.2 mol / l aqueous solution of barium hydroxide. As a result, a 0.1 μm thick BaTiO ₃ thin film was obtained on the Ti substrate aqueous solution. FIG. 1 shows an X-ray diffraction pattern of the obtained BaTiO ₃ thin film. Then this BaTi
O ₃ Ti substrate barium hydroxide 0.07 which thin film was formed
In a mixed aqueous solution of 8 mol / l, lead hydroxide 0.078 mol / l and potassium hydroxide 2.0 mol / l, 140
The reaction was performed at 20 ° C. for 20 hours. As a result, a BaPbO ₃ thin film was obtained on the BaTiO ₃ thin film. SEM of BaPbO ₃ thin film
A photograph is shown in FIG. 2 and an X-ray diffraction pattern of the BaPbO ₃ thin film is shown in FIG.

Example 2 A Ti substrate was placed in an inner container of an autoclave, and lead hydroxide was
0.1mol / l, zirconium hydroxide 0.053mo
1 / l, titanium hydroxide 0.001mol / l and hydroxyl
160 ° C. in a mixed aqueous solution of 1.5 mol / l potassium iodide
For 24 hours. As a result, on the Ti substrate surface
5.0 μm thick Pb (Zr, Ti) O _ThreeGet a thin film
Was. Then, the Pb (Zr, Ti) O_ThreeFormed a thin film
Strontium hydroxide 0.056mol / Ti substrate
l, lead hydroxide 0.056mol / l and potassium hydroxide
In a mixed aqueous solution of 1.5 mol / l at 150 ° C for 15 hours
Reaction. As a result, Pb (Zr, Ti) O_ThreeThin film
SrPbO on top_ThreeA thin film was obtained. Obtained SrPbO_ThreeThin film
The X-ray diffraction pattern of the sample is shown in FIG.

Example 3 A Ti substrate was placed in an inner container of an autoclave, and barium hydroxide (0.078 mol / l) and lead hydroxide (0.078 mol) were used.
The reaction was carried out at 140 ° C. for 20 hours in a mixed aqueous solution of l / l and 2.0 mol / l of potassium hydroxide. As a result, T
A BaPbO ₃ thin film having a thickness of 2.0 μm was obtained on the surface of the i-substrate. When this thin film was subjected to X-ray diffraction analysis, a diffraction pattern similar to that of FIG. 3 was obtained. As a result, BaP is deposited on the Ti substrate.
It was confirmed that a crystalline thin film of bO ₃ was formed. When the resistance of the obtained BaPbO ₃ thin film was measured by a four-terminal method, it showed a low value of 8 × 10 ⁻³ Ω · cm.

Example 4 A lead substrate was placed in an inner container of an autoclave, and barium hydroxide 0.039 mol / l and lead hydroxide 0.039 mol were used.
The reaction was carried out at 160 ° C. for 12 hours in a mixed aqueous solution of 1.5 mol / l of potassium hydroxide and 1.5 mol / l of potassium hydroxide to obtain a 1.0 μm thick BaPbO ₃ thin film. BaP obtained
FIG. 5 shows the X-ray diffraction pattern of the bO ₃ thin film. When the resistance of the obtained BaPbO ₃ thin film was measured by a four-terminal method, it showed a low value of 4 × 10 ⁻³ Ω · cm.

Example 5 Pb (OC ₃ H ₇ ) ₂ was dissolved in zeolite-dehydrated 2-methoxyethanol to obtain a 0.6 mol / l solution.
This solution was spin-coated on a Ti substrate at 2000 rpm. All of the above operations were performed in a nitrogen atmosphere. Spin-coated substrates have two coating layers
It was thermally decomposed at 50 ° C. to form a lead oxide thin film.

Next, the substrate was placed in an inner container of an autoclave, and the solution was placed in an alkali having the same composition as in Example 4.
The reaction was carried out under the same conditions as described above, and a 1.0 μm thick BaPbO ₃
A thin film was obtained. The obtained BaPbO ₃ thin film showed the same X-ray diffraction pattern as in FIG.

[0028]

According to the present invention, when a substrate having a perovskite oxide on its surface is subjected to heat treatment in an alkaline aqueous solution containing A ions (A is at least one of Ba and Sr) and Pb ions, the surface is electrolyzed. This eliminates the need for facilities and steps such as the above, and makes it possible to manufacture a conductive APbO ₃ thin film (here, A is at least one of Ba and Sr) at low cost and easily.

Further, even when a substrate having Ti or Ti oxide or Pb or Pb oxide on the surface is reacted under the same conditions as described above, a conductive APbO ₃ thin film can be easily formed.

[Brief description of the drawings]

FIG. 1 is an X-ray diffraction diagram of a BaTiO ₃ thin film obtained in Example 1.

FIG. 2 is a SEM photograph instead of a drawing showing the surface state of the BaPbO ₃ thin film obtained in Example 1.

FIG. 3 is an X-ray diffraction diagram of the BaPbO ₃ thin film obtained in Example 1.

4 is an X-ray diffraction diagram of the SrPbO ₃ thin film obtained in Example 2. FIG.

5 is an X-ray diffraction diagram of the BaPbO ₃ thin film obtained in Example 4. FIG.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5G303 AA10 AB20 BA03 CA01 CB03 CB25 CB32 DA01 5G323 BA05 BB01

Claims (3)

[Claims] A substrate having a perovskite oxide on its surface is subjected to a heat treatment in an alkaline aqueous solution containing A ions (A is at least one of Ba or Sr) and Pb ions to form a substrate on the perovskite oxide layer. A method for producing a composite lead oxide thin film, comprising forming an APbO ₃ thin film. 2. A substrate having Ti or Ti oxide on its surface is subjected to heat treatment in an alkaline aqueous solution containing A ions (A is at least one of Ba or Sr) and Pb ions, and the substrate is treated with Ti or Ti oxide. A method for producing a composite lead oxide thin film, comprising: forming an APbO ₃ thin film on the substrate. 3. A substrate having Pb or Pb oxide on its surface is subjected to heat treatment in an alkaline aqueous solution containing A ions (A is at least one of Ba or Sr) and Pb ions. A method for producing a composite lead oxide thin film, comprising: forming an APbO ₃ thin film on the substrate.