JPH04300213A - Amorphous ferroelectric oxide material - Google Patents

Abstract

PURPOSE:To provide an amorphous ferroelectric material capable of being applied to thin film type capacitor elements, ferroelectric memories, electro- optical devices, etc., and also provides a method for producing the thin film. CONSTITUTION:The objective material is characterized by comprising a ternary oxide consisting mainly of a Fe2O3-Bi2O3-Perovskite type compound (ABO3) and by having a composition surrounded by four composition lines of xBi2O3-(1- x)Fe2O3, 0.90Bi2O3-0.10(yFe2O3-(1-y)ABO3, zBi2O3-(1-z)ABO3 and q(0.55Bi2O3-0.45 Fe2O3)-(1-q) (0.10Bi2O3-0.90ABO3) wherein 0.55<=x<=0.90, 0.00<=y<=1.00 0.10<=z<=0.10 and 0.00<=q<=1.00.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amorphous ferroelectric oxide material that can be used to construct thin-film capacitor elements, ferroelectric memories, electro-optical devices, etc., and a method for producing the thin film.

0002

[Prior Art] Conventionally, inorganic ferroelectric materials,
Its ferroelectric properties are developed based on certain rules in crystal symmetry. Therefore, in order to make the ferroelectric property noticeable, increasing the crystallinity of the material makes the ferroelectric property noticeable. In fact, for materials with a perovskite crystal structure, adjusting the firing temperature to increase crystallinity,
Also, many efforts have been made in connection with the above-mentioned matters, such as improving sintered density.

On the other hand, in capacitors, ferroelectric memories, etc. that use ferroelectric materials, if the material is polycrystalline, the presence of grain boundaries may cause a drop in withstand voltage, and leakage current may occur along the grain boundaries. occurs, causing loss in capacitors, and impairing information retention in memory. Furthermore, the presence of grain boundaries makes it difficult to miniaturize various devices, which has become a major problem as various devices that utilize the dielectric properties of materials are becoming smaller. Also,
Even when a dielectric material is used as an electro-optical element, the presence of crystal grain boundaries causes light scattering, which poses a major problem in making the optical device function.

[0004] In order to solve these problems, attempts have been made to construct microdevice capacitors, ferroelectric memories, or electro-optical devices by constructing thin films of ferroelectric materials.

In order to avoid the occurrence of grain boundaries in thin films, attempts have been made to fabricate single-crystal dielectric thin films and amorphous dielectric thin films.

Regarding single-crystal dielectric thin films, for example, according to Nishihara, Haruna, and Suhara: Photonic Integrated Circuits (Ohmsha, 1986), p. 174, PLZT, which is well known as a ferroelectric material, An example of fabricating a crystalline thin film is described. According to the same book, in order to obtain a single-crystal PLZT thin film, epitaxial growth is performed on a sapphire single-crystal substrate by a sputtering film forming method. In addition, the book also describes how ferroelectric LiNbO3 thin films, etc., are grown using liquid phase epitaxial growth (LPE).
There is an example of growth on a 5 O12 (GGG) single crystal substrate.

However, in either method, an expensive single crystal substrate is used as the substrate, various conditions must be strictly controlled for epitaxial growth, and the crystal axis on which the crystal grows is different from that of the single crystal. Actual production of thin films is not easy, as growth of single crystal thin films becomes difficult because of orientation constraints, and if the difference between the lattice constant of the single crystal substrate and the lattice constant of the thin film becomes too large. Furthermore, the epitaxial growth method described above requires a high heat treatment temperature of approximately 600°C or higher to single-crystallize a thin film, so there is a problem that the surface properties of the film are impaired by the heat treatment of the film. This has been a major barrier to the development of microdevices from ferroelectric materials.

Similar to single crystal thin films, amorphous thin films have
Since there are no grain boundaries, it is expected that it will be put to practical use in order to solve the various problems that occur in the aforementioned ferroelectric polycrystalline materials.

Literature, Japanese Journal
l Applied Physics, Vol. 2
4 (1985), Supplement 24-
2, pp404-406. and Applied Physics Vol. 54 No. 6 (
1985) pp. 568-575, attempts have been made to make PbTiO3 into an amorphous thin film by sputtering. However, sputtering thin films produced while adjusting the substrate temperature during film formation at various temperatures from 200° C. to liquid nitrogen temperature have an amorphous structure but do not exhibit ferroelectricity. Furthermore, it has been reported that fine crystals of Pb and PbO also precipitate in the same thin film. Another problem is that the thin film does not function as a dielectric film because it becomes conductive due to the precipitation of Pb.

Furthermore, in the same report, in order to turn this conductive thin film into a ferroelectric material, the thin film was heat-treated at a temperature of 600°C or higher to produce PbTiO3 having a perovskite crystal structure.
Obtaining a thin film. However, the thin film obtained by this method is polycrystalline, and it is thought that the above-mentioned problems will be encountered when attempting to miniaturize various devices using ferroelectric materials.

[0011] In this way, PbTiO3, PbZrO
For typical perovskite dielectric materials such as 3, BaTiO3, amorphous ferroelectrics have not been obtained so far.

[0012] Literature for such problems: Materials of the Institute of Electrical Engineers of Japan Magnetics Study Group, (1989) MHA89-1
17. In this case, perovskite materials contain Fe2 O3 and Bi2 in the composition range surrounded by the dotted line in Figure 1.
By adding O3, amorphous ferroelectricity has been found in a part of this composition range. However, the saturation charge density of amorphous ferroelectric materials found in this composition range is approximately 150 nC/cm2.
When applying the same material to various devices, for example, in ferroelectric memory, the amount of accumulated charge is small, so it is difficult to obtain a sufficient signal output voltage, or when forming a capacitor, electrostatic There were problems such as not being able to obtain a large capacity.

[0013]

[Problems to be Solved by the Invention] The present invention has an amorphous structure, and therefore has no grain boundaries or pores found in sintered bodies, and is capable of producing capacitors with low loss and high strength with high information retention. It is an object of the present invention to provide a ferroelectric oxide material that can be applied to dielectric memories or electro-optic devices with no light scattering and high transparency, and a method for manufacturing the same.

[0014]

[Means for Solving the Problems] The present invention provides Fe2O3
-Bismuth oxide (Bi2O3)-It is composed of a ternary oxide mainly composed of a specific range of perovskite compounds (ABO3), and is formed into a film using an amorphous film forming method such as vacuum evaporation or sputtering. The above-mentioned problem was solved by employing a method of using this as is and not performing heat treatment for crystallization as in the conventional method.

That is, the present invention consists of a ternary oxide mainly composed of Fe2O3-bismuth oxide (Bi2O3)-perovskite compound (ABO3),
In the composition diagram of these three components, xBi2 O3 −(
1-x) Fe2 O3 and 0.90Bi2 O3
-0.10(yFe2O3 -(1-y)ABO3
) as well as zBi2O3-(1-z)ABO3
and q(0.55Bi2O3 -0.45F
e2 O3 )-(1-q)(0.10Bi2 O3
-0.90ABO3) 0.55<x<0.90 and 0.00<y<1.00
and 0.10<z<0.90 and 0.00<q<1.0
Amorphous ferroelectric oxide material characterized by having a composition surrounded by four composition lines defined in the range 0 (herein, ABO3 is a ferroelectric material, an antiferroelectric material, or It is a paraelectric material).

Furthermore, the present invention provides a method for obtaining a ferroelectric material by forming an amorphous thin film of the above composition on a substrate using a film forming means while maintaining the substrate temperature at 300° C. or lower. The present invention provides a method for producing a characteristic thin film-like amorphous ferroelectric oxide material.

According to the method for producing an amorphous ferroelectric thin film of the present invention, various dielectric materials of berovskite type (Pb
Ferroelectric materials such as TiO3, BaTiO3, PbZ
An amorphous ferroelectric material can be obtained by adding excessive amounts of Bi2 O3 and Fe2 O3 to an antiferroelectric material (such as rO3). This material can be produced by commonly used thin film forming processes such as vacuum evaporation and sputtering. During film formation, the substrate temperature was adjusted to the crystallization temperature of the amorphous composite oxide (500 to 600
(°C) or below, an amorphous oxide thin film having ferroelectricity can be produced by forming the film in an oxygen atmosphere at a substrate temperature of, for example, about 25°C.

Conventionally, the development of amorphous ferroelectricity in this system has been reported in the literature: Materials of the Magnetics Study Group of the Institute of Electrical Engineers of Japan, (1989) MHA89-117. It has been reported in The compositional region searched in this document is the region surrounded by a dotted line in FIG. As is clear from the figure, this region is BiFeO3 -ABO
3 This is a region where the Fe2O3 concentration is excessive compared to the perovskite solid solution line.

In the present invention, the dielectric properties of thin film materials prepared in the composition region below the BiFeO3 -ABO3 perovskite solid solution line were evaluated.
Similar to the conventional composition, the material has an amorphous structure, but exhibits more pronounced ferroelectricity.Reference: Materials of the Institute of Electrical Engineers of Japan Magnetics Study Group, (1989) MHA89-117
．． We have discovered that we can provide a more practical dielectric material than the amorphous ferroelectric materials reported in .

The composition range of the high-performance amorphous ferroelectric material discovered in the present invention is α, β in FIG.
, γ, and δ. Here, the straight line α
β is a straight line represented by xBi2O3 - (1-x)Fe2O3, and straight line βγ is 0.90Bi2O3
-0.10(yFe2O3 -(1-y)ABO3
), and the straight line γδ is zBi2 O3−
(1-z) ABO3 is a straight line, and the straight line δα
is q(0.55Bi2 O3 -0.45Fe2 O3
)-(1-q)(0.10Bi2O3-0.90
ABO3), and each composition line has 0.55<x<0.90 and 0.00<y<1.0.
0 and 0.10<z<0.90 and 0.00<q<1.
This is a composition line defined in the range 00.

In the figure, ABO3 represents various perovskite dielectric materials (PbTiO3, BaTiO3
ferroelectric materials such as PbZrO3, and antiferroelectric materials such as PbZrO3. In Figure 1 and the triangular composition diagram below,
The notches on the three sides represent 1 scale of 0.1 (mol ratio).

The amorphous ferroelectric oxide material according to the present invention can be made into a ferroelectric material by a simple method without epitaxial growth using a single crystal substrate or the like during film formation or heat treatment for thin film crystallization after film formation. Obtained as a thin film exhibiting characteristics.

[0023] To this end, it is possible to significantly reduce the time and effort required to produce a ferroelectric thin film, and also to produce a film with very good surface properties and no grain boundaries, so high-density ferroelectric memory using ferroelectric materials , and is expected to be used in microdevices such as ultrafine capacitors.

In addition, the material of the present invention has a higher saturation charge density than conventional amorphous ferroelectric materials, and can realize higher performance and smaller size of various dielectric devices. It becomes possible to put various dielectric devices into practical use using dielectric materials.

[0025]

[Example] (First example) A high frequency magnetron sputtering device was used to prepare a thin film, and a
Place a stainless steel Petri dish with a size of 6 mm and a depth of 4 mm, and place Bi2 O3, Fe2 O3, PbTiO in it.
A target filled with a mixed powder of PbO and PbO was used as a target. Note that PbO was added in an amount of 5 mol % in excess of PbTiO3 during sputtering to compensate for loss due to lead evaporation. Bi2O3, Fe2O3, PbTiO
Prior to filling each powder of 3 and PbO into a stainless steel Petri dish, the powder of each oxide material was wet-mixed using ethanol as a solvent for 30 minutes in a paint shaker. Thereafter, the mixture was further desorbed and dried, then filled into a stainless steel petri dish and used as a sputtering target.

The sputtering gas is a mixed gas of Ar:O2 = 7:3, and the purity of each of the Ar and O2 gases is 99.
995% or more was used. A (111) oriented Si wafer was used as the substrate. The Si wafer used was an n-type one with a resistivity of approximately 1 (Ωcm). Si
The film thickness is 200±20 on the wafer by oxidation treatment in advance.
A layer of SiO2 is provided. The purpose of providing this layer is mainly to ensure electrical insulation during dielectric evaluation.

Prior to film formation, the substrate temperature was raised to 200° C., and water mainly adsorbed on the substrate surface was removed. Furthermore, pre-sputtering was performed for about 30 minutes before film formation to clean the target surface and stabilize the film quality and thin film composition during sputtering film formation.

[0028] Before introducing the sputtering gas, the degree of vacuum is 2×
It was confirmed that the temperature had reached 10-7 Torr or less. During sputter film formation, the total gas pressure was kept constant at 25 mTorr. During sputtering, the copper anode that fixes the substrate is cooled with water, and the substrate temperature during film formation is kept at 20-25℃.
maintained. The high frequency input power was 110 W, and sputtering film formation was performed for 30 to 60 minutes. The thickness of the thin films obtained in this way varied because the sputtering rate varied depending on the composition of the target, but each thin film had a thickness of about 500 to 1000 nm.

By the above thin film forming process, B
A sputtered thin film was prepared using three elements: i2O3, Fe2O3, and PbTiO3. In Figure 2, No. The compositions indicated by numbers 1 to 22 were prepared, and the film structure and magnetic properties and dielectric properties were measured for each film.

When the obtained thin film was examined for correspondence between the target composition and the thin film composition by induced plasma emission spectroscopy, it was found that the two compositions corresponded with each other with an error of approximately 3%. Therefore, in the following description, the composition of the target will be used as the composition of the thin film.

The magnetic properties were evaluated using a vibrating sample magnetometer (VSM), and the dielectric properties were evaluated using a Soyer-Tower circuit commonly used in the evaluation of the same characteristics. Using this circuit, the electric field dependence of electric flux density (D) was evaluated and the value of spontaneous polarization (Ps) was determined. In the dielectric evaluation, the electrode configuration as shown in FIG. 3 was used, and the electrode for applying an electric field to the sputtered thin film 1 was brought out from the oxide thin film 2 side, thereby equivalently creating two capacitors C1, The configuration is such that C2 are connected in series, and when the electrode is brought out from the Si3 side, A
Prevents Schottky characteristics that occur at the interface between u and Si,
Accurate dielectric property evaluation was performed. Note that an Au electrode 4 having a thickness of about 100 nm and a diameter of 4 mm was formed on the surface of the thin film by sputtering.

[0032] The sputtered thin film produced by the above thin film forming method is in the as-produced state (As-depos
The magnetic properties, structure, and dielectric properties of the "IT state" were evaluated.

The magnetic properties were evaluated using VSM under a maximum applied magnetic field of 15 kOe, and the results were as follows: No. 2 shown in FIG.
In all compositions from No. 1 to No. 22, the thin films did not exhibit ferromagnetism and exhibited paramagnetism.

Next, the results of evaluating the structure of the thin film will be described. First, in FIG. 2, composition No. 2,N
o. 5, No. 6, No. The XRD diffraction results of the thin film No. 7 after sputter deposition are shown in FIG. A Cu target was used as the XRD radiation source, and a monochromator was further attached. In the XRD results shown in FIG. 4, a diffraction line corresponding to the (111) plane of Si used as a substrate is also seen superimposed on the diffraction result of the thin film.

As is clear from the figure, PbTiO3
No. In No. 7, it can be seen that the thin film undergoes crystallization even in the state in which it is formed by the sputtering method. However, the composition in which Bi2 O3 is excessive (No.
2, No. 5, No. In 6), no X-ray diffraction lines due to crystallization of the thin film were observed, indicating that the thin film was in an amorphous state.

Furthermore, in FIG. 5, the perovskite BiFeO3 in FIG. 2 and the perovskite PbTi
Composition No. parallel to the O3 solid solution line. 8, No. 12,
No. The XRD diffraction results of 16 thin films formed by sputtering are shown. As is clear from FIG. 5, there are no clear diffraction lines in the XRD results other than the diffraction line corresponding to the (111) plane of Si, indicating that all thin films with these compositions have an amorphous structure. is understood. Furthermore, in order to observe the microstructure of the amorphous structure, the N
o. High-resolution TEM observation was performed on films with compositions of 11 to 10. In the TEM observation, etching was performed from the surface side of the thin film and the substrate side, and the structure near the midpoint in the thickness direction of the thin film was observed. According to this, 0.3
Even at nm resolution, no lattice image could be recognized.

Selected area electron diffraction was performed on the same thin film sample in a region having a diameter of about 200 nm. The diffraction rings showed a very wide halo pattern, indicating that the thin film was highly amorphous. From these results, it was found that in the regions surrounded by α, β, γ, and δ in FIGS. 1 and 2, the thin film had an amorphous structure in the state in which the thin film was produced (as-deposited state).

Next, the dielectric characteristics will be explained. first,
The dependence of the electric flux density on the electric field in the state where thin films of various compositions were prepared on the straight line A in FIG. 2 is shown (FIG. 6). FIG. 7 shows the electric field dependence of the electric flux density on the straight line B in FIG. 2 when thin films of various compositions were prepared. According to FIGS. 6 and 7, a typical hysteresis loop observed in ferroelectric materials is observed in the electric field dependence of electric flux density. This indicates that the composition region exhibiting ferroelectricity in the amorphous state has expanded not only above the solid solution line in Figures 1 and 2, where the existence of amorphous ferroelectricity has been reported, but also in the region below the solid solution line. I realized that it was.

Here, the straight line A is rFe2 O3
-(1-r)(0.33Bi2O3 -0.67Pb
TiO3 ), Bi2 O3 and PbTiO3
This corresponds to changing the concentration of Fe2O3 while keeping the composition ratio constant. The thin film with r=0.25 is No. 2 in FIG. 13, and in this respect BiFeO
3 and PbTiO3 perovskites are present in equal amounts.

The saturation charge density (Ps) representing the strength of ferroelectricity on this A line is calculated from the hysteresis loop of dielectric characteristics shown in FIG. The dependence was extrapolated to the E=0 axis, and the electric flux density at the point where it intersects with the coaxial axis was defined as the saturation charge density. FIG. 8 shows the r dependence of the saturation charge density thus obtained. As is clear from this figure, r is 0.25 or less, that is,
In FIGS. 1 and 2, a rapid increase in the saturation charge density was observed in the regions surrounded by α, β, γ, and δ.

Straight line B is 0.80((1-t)Bi2O
3-tFe2O3)-0.2PbTiO3, while keeping the composition of PbTiO3 constant.
This corresponds to changing the composition ratio of 2 O3 and Fe2 O3. The saturation charge density was determined on this line by the method described above, and FIG. 9 shows the t dependence of the charge density. As is clear from this figure, a rapid increase in the saturation charge density was observed when t was 0.50 or less, that is, in the regions surrounded by α, β, γ, and δ in FIGS. 1 and 2.

As is clear from the results shown in FIGS. 6, 7, 8, and 9, a composition region exhibiting ferroelectricity in an amorphous state spreads below the solid solution line in FIGS. 1 and 2. Furthermore, it was found that this composition region exhibits stronger ferroelectricity than above the solid solution line, making it a very useful thin film material for applications.

Note that No. 2 in FIG. 7, that is, PbTiO3
In the thin film, a crystalline phase considered to be a pyrochlore phase was precipitated immediately after the film was formed, and the film did not exhibit ferroelectricity, and its dielectric properties were paraelectric-like. Also, No. 1 film, that is, Bi
2 O3 thin film and No. Although the thin film of No. 22 had an amorphous structure, it was paraelectric.

Furthermore, Table 1 shows α, β, γ shown in FIG.
, δ, the correspondence between the thin film composition and the saturation charge density Ps is shown. For thin films that exhibit ferroelectricity,
It has a saturation charge density of approximately 155 (nC/cm2) or more, and this charge density is at most 1300 (nC/cm2).
It turns out that it has reached a certain level. From this result, it is considered that the present amorphous ferroelectric material has sufficient practical characteristics as a ferroelectric material.

[0045]

[Table 1] (Second Example) A thin film was produced by the film forming method explained in Example 1, except that the substrate was replaced with a glass substrate. The glass substrate is Corning's No. 7059 was used. No. shown in FIG. 9 and no. A thin film having a composition of 11 was prepared. The thickness of the thin film formed by sputtering was approximately 1 μm. The produced thin film had an amber color.

Each of the thin films was coated with an antireflection coating in the near-infrared region, and the light transmittance was measured. FIG. 10 shows the dependence of transmittance on light wavelength. As can be seen from this result, the amorphous ferroelectric thin film has a light transmittance of 90% or more in the near-infrared region, and it can be seen that the thin film can be applied to electro-optical elements. (Third Example) A thin film was fabricated using the same film forming method as in the first example, using antiferroelectric PbZrO3 instead of ferroelectric PbTiO3 as the perovskite dielectric material. The composition of the produced thin film is shown in the triangular composition diagram in Figure 11 by No.
．． 1 and No. 23~No. It is represented as a dot with numbers up to 34 added. Thin film as formed (As-d
dielectric property and structural analysis using X-rays were performed on the thin film (eposit thin film).

The results are summarized in FIG. 11. In the figure, black circles indicate the composition of a thin film that exhibits amorphous ferroelectricity, and hatched circles indicate the composition of a thin film that exhibits paraelectricity while having an amorphous structure. From this result, it was found that amorphous ferroelectricity was expressed in the region surrounded by α, β, γ, and δ in the triangular composition diagram. Also, No. 1 outside this area. 33, No.
Amorphous ferroelectricity was also confirmed for the film of No. 34.

Straight line C is 0.60((1-t)Bi2O
3-tFe2O3)-0.40PbZrO3, while keeping the composition of PbTiO3 constant.
This corresponds to changing the composition ratio of i2 O3 and Fe2 O3. The saturated charge density was determined on this line by the method explained in the first embodiment, and the t of the same charge density is shown in FIG.
showed dependence. As is clear from this figure, t is 0.5
A rapid increase in the saturation charge density was observed below 0, that is, in the regions surrounded by α, β, γ, and δ in FIGS. 1 and 2.

As is clear from the results shown in FIGS. 11 and 12, a composition region exhibiting ferroelectricity in an amorphous state spreads below the solid solution line in FIG. The material showed stronger ferroelectricity than above the solid solution line, and was found to be a very useful thin film material for applications.

Furthermore, the results revealed that PbZrO3 material, which exhibits antiferroelectricity when used alone, exhibits remarkable ferroelectricity when Fe2O3 or Bi2O3 is added in excess. Further, Table 2 shows a list of saturation charge densities for each composition shown in FIG. As is clear from the table, even though the thin film has an amorphous structure, the maximum saturation electric field density is 1062 (nC/cm).
2) was also reached. From this result, it can be said that the present amorphous ferroelectric material has sufficient practical characteristics as a ferroelectric material.

[0051]

(Table 2) (Fourth Example) A thin film was fabricated using ferroelectric BaTiO3 as a perovskite dielectric material using the same film forming method as in the first example. The composition of the produced thin film is shown in the triangular composition diagram of FIG. 1 and No. 35~No. 4
It is represented as a dot with numbers up to 6 added. In the figure, black circles indicate the composition of a thin film that exhibits amorphous ferroelectricity, and hatched circles indicate the composition of a thin film that exhibits paraelectricity while having an amorphous structure.

From this result, in the triangular composition diagram, α,
It has been found that amorphous ferroelectricity is expressed in the composition region surrounded by β, γ, and δ. Also, No. 1 outside this area. 45, No. Amorphous ferroelectricity was also confirmed for film No. 46.

[0053] The dotted line D is 0.60 ((1-t)Bi2O
3-tFe2O3)-0.40BaTiO3, while keeping the composition of PbTiO3 constant,
This corresponds to changing the composition ratio of i2 O3 and Fe2 O3. The saturated charge density was determined on this line by the method described in Example 1, and the dependence of the charge density on t is shown in FIG. As is clear from this figure, t is 0.50
Below, a rapid increase in the saturation charge density was observed in the regions surrounded by α, β, γ, and δ in FIGS. 1 and 2.

As is clear from the results shown in FIGS. 13 and 14, a composition region exhibiting ferroelectricity in an amorphous state spreads below the solid solution line in FIG. The material showed stronger ferroelectricity than above the solid solution line, and was found to be a very useful thin film material for applications. Furthermore, Table 3 shows a list of saturation charge densities for each composition shown in FIG.

As is clear from the same table, the saturation electric field density reaches a maximum of 792 (n) even though the thin film has an amorphous structure.
C/cm2). From this result, it can be said that the present amorphous ferroelectric material has sufficient practical characteristics as a ferroelectric material.

[0056]

[Table 3] (Effects of the invention) As mentioned above, Fe2 O3 -Bi2
By thinning an O3 -ABO3 (ABO3 is a perovskite dielectric) thin film using RF sputtering or other methods at a low substrate temperature, for example at a substrate temperature of about 25°C, a highly translucent ferroelectric film with an amorphous structure can be created. Thin films can be obtained that can be applied to sensors, memories, and electro-optical devices that apply ferroelectricity.

[Brief explanation of drawings]

FIG. 1 is a compositional diagram for explaining the present invention.

FIG. 2 is a compositional diagram for explaining one embodiment of the present invention;
Also, explanatory diagrams of dielectric properties and thin film structure.

FIG. 3 is a structural diagram of a thin film for explaining the dielectric property evaluation method of the present invention.

FIG. 4 is an X-ray diffraction pattern for explaining one embodiment of the present invention.

FIG. 5 is an X-ray diffraction pattern for explaining the same example.

FIG. 6 is a diagram showing the electric field dependence of dielectric properties to explain the same example.

FIG. 7 is a diagram showing the electric field dependence of dielectric properties to explain the same example.

FIG. 8 is a diagram showing composition dependence of saturation charge density for explaining the same example.

FIG. 9 is a diagram showing composition dependence of saturation charge density for explaining the same example.

FIG. 10 is a diagram showing wavelength-dependent characteristics of light transmittance for explaining the same example.

FIG. 11 is a composition diagram for explaining another example of the present invention, and an explanatory diagram of dielectric properties and thin film structure.

FIG. 12 is a diagram showing composition dependence of saturation charge density for explaining the same example.

FIG. 13 is a compositional diagram for explaining another example of the present invention, and an explanatory diagram of dielectric properties and thin film structure.

FIG. 14 is a diagram showing composition dependence of saturation charge density for explaining the same example.

Claims (3)

[Claims] [Claim 1] Fe2 O3 - bismuth oxide (Bi2
It consists of a ternary oxide whose main component is a perovskite compound (ABO3), and in the composition diagram of these three components, xBi2O3 -(1-x)Fe2O3
and 0.90Bi2O3 -0.10(yF
e2O3-(1-y)ABO3) and zB
i2 O3 −(1-z)ABO3 and q(0
．． 55Bi2O3-0.45Fe2O3)-(
1-q) (0.10Bi2 O3 -0.90ABO3
) in each composition line represented by 0.55<x<0
．． 90 and 0.00<y<1.00 and 0.10<z<
An amorphous ferroelectric oxide material having a composition surrounded by four composition lines defined in the range of 0.90 and 0.00<q<1.00. Here, A.B.O.
3 is a ferroelectric material, an antiferroelectric material, or a paraelectric material. 2. The amorphous ferroelectric oxide material according to claim 1, wherein the composition is formed in the form of a thin film. 3. A ferroelectric material is obtained by producing the composition as an amorphous thin film on a substrate using a film forming means while maintaining the substrate temperature at 300° C. or less. Section 2
A method for producing the amorphous ferroelectric oxide material described above.