Dielectric and Functional Element

Abstract

This dielectric includes an oxide containing hafnium and cerium. The molar ratio of the cerium content to the sum of the hafnium content and cerium content is 0.031-0.052. The molar ratio of the oxygen content to the sum of the hafnium content and cerium content is greater than 0 and less than or equal to 1.50.

Description

Technical Field

[0001] The present disclosure relates to dielectrics and functional elements.

Background Art

[0002] Conventionally, in hafnium oxide having a fluorite structure, it is known that the crystal phase changes by adding other metal elements, and the dielectric properties change from a normal dielectric to a ferroelectric. For example, Non-Patent Document 1 describes that hafnium oxide to which elements such as Si, Al, Zr, and Y are added exhibits ferroelectricity.

[0003] Non-Patent Document 2 describes that a film of a solid solution represented by (Hf 1-x Ce x )O2 exhibits ferroelectricity. In this film, x ranges from 0.15 to 0.20.

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present disclosure is to provide a novel dielectric suitable for use in functional elements such as capacitors.

Means for Solving the Problems

[0006] The present disclosure includes an oxide containing hafnium and cerium, The molar ratio of the content of cerium to the sum of the contents of hafnium and cerium is 0.031 or more and 0.052 or less, and the molar ratio of the content of oxygen to the sum is greater than 0 and 1.50 or less, to provide a dielectric.

Advantages of the Invention

[0007] According to the present disclosure, a novel dielectric suitable for use in functional elements such as capacitors can be provided.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0009] (Findings underlying the present disclosure) In (Hf 1-x Ce x )O2 described in Non-Patent Document 2, the addition concentration x of Ce is 0.15 to 0.20. Ce in CeO2 depends on the surrounding oxygen concentration, and Ce 4+ and Ce 3+The valence number easily changes between them. When manufacturing a capacitor using a dielectric containing HfO₂ added with Ce, for example, at the interface between the dielectric and the electrode, the valence number of Ce is likely to change depending on the oxygen concentration in the electrode. When the valence number of Ce fluctuates, the electronic state around the Ce cation changes, so the characteristics of the dielectric may fluctuate. When the characteristics of the dielectric fluctuate, the characteristics of the capacitor composed of the dielectric also fluctuate. From the above, suppressing the fluctuation of the valence number of the Ce cation in the dielectric is desirable from the viewpoint of suppressing the fluctuation of the characteristics of functional elements such as capacitors and obtaining a chemically stable dielectric.

[0010] In view of such circumstances, the inventors of the present invention have intensively studied to improve the chemical stability of a dielectric used in a functional element using a dielectric containing an oxide containing hafnium and cerium. As a result, the inventors have newly found that the chemical stability of the dielectric can be improved by adjusting the contents of hafnium, cerium, and oxygen to a predetermined relationship. Based on this new finding, the dielectric of the present disclosure has been devised.

[0011] (Embodiment) Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. However, the present disclosure is not limited to the following embodiments.

[0012] FIG. 1 is a cross-sectional view showing an example of a functional element 1a of the present disclosure. As shown in FIG. 1, the functional element 1a includes a dielectric 10. The dielectric 10 includes an oxide containing hafnium and cerium. The molar ratio of the content of cerium to the sum of the content of hafnium and the content of cerium is 0.031 or more and 0.052 or less, and the molar ratio of the content of oxygen to the sum is greater than 0 and 1.50 or less. According to such a configuration, the chemical stability of the dielectric 10 can be improved. The dielectric 10 may contain Zr contained in a precursor raw material of Hf or the like.

[0013] In the dielectric 10 according to this embodiment, the elemental concentration of Ce contained in the dielectric 10 is reduced. Specifically, the molar ratio of the content of Ce to the sum of the content of hafnium and the content of cerium satisfies 0.031 or more and 0.052 or less. For this reason, in the dielectric 10, the region where the valence of Ce is likely to fluctuate can be made small. That is, a chemically stable dielectric 10 can be obtained.

[0014] In addition, in the dielectric 10 according to this embodiment, the molar ratio of the content of oxygen to the sum of the content of hafnium and the content of cerium satisfies more than 0 and 1.50 or less. That is, the concentration of oxygen contained in the dielectric 10 is kept low. For this reason, in the dielectric 10, it becomes possible to reduce the elemental concentration of Ce. As a result, in the dielectric 10, the region where the valence of Ce is likely to fluctuate can be made small. That is, a chemically stable dielectric 10 can be obtained.

[0015] The molar ratio of the content of Ce to the sum of the content of hafnium and the content of cerium in the dielectric 10 may satisfy 0.031 or more and 0.050 or less, and may satisfy 0.031 or more and 0.048 or less. The molar ratio may satisfy 0.035 or more and 0.052 or less, may satisfy 0.040 or more and 0.052 or less, may satisfy 0.045 or more and 0.052 or less, and may satisfy 0.048 or more and 0.052 or less.

[0016] The molar ratio of the content of oxygen to the sum of the content of hafnium and the content of cerium in the dielectric 10 may satisfy 1.44 or more and 1.50 or less. In this case, the region where the valence of Ce is likely to fluctuate can be made smaller. As a result, a chemically more stable dielectric 10 can be obtained. The molar ratio may satisfy 1.44 or more and 1.47 or less.

[0017] The dielectric 10 has a composition formula Hf 1-x Ce x O yIt may have a composition represented by this. In this compositional formula, 0.031 ≦ x ≦ 0.052 and 0 < y ≦ 1.50 are satisfied. According to such a configuration, the chemical stability of the dielectric 10 can be improved.

[0018] The dielectric 10 may satisfy 0.031 ≦ x ≦ 0.050, and may satisfy 0.031 ≦ x ≦ 0.048. The dielectric 10 may satisfy 0.035 ≦ x ≦ 0.052, may satisfy 0.040 ≦ x ≦ 0.052, may satisfy 0.045 ≦ x ≦ 0.052, and may satisfy 0.048 ≦ x ≦ 0.052.

[0019] The dielectric 10 may satisfy 1.44 ≦ y ≦ 1.50. In this case, the region where the valence of Ce is likely to fluctuate can be made smaller. As a result, a chemically more stable dielectric 10 can be obtained. The dielectric 10 may satisfy 1.44 ≦ y ≦ 1.47.

[0020] The dielectric 10 may contain a crystal phase having a fluorite-type crystal structure. In addition, the dielectric 10 may be a polycrystalline film. According to such a configuration, the dielectric 10 is likely to exhibit ferroelectricity. The crystal phase having a fluorite-type crystal structure is, for example, an orthorhombic phase, a monoclinic phase, a tetragonal phase, and a cubic phase.

[0021] The dielectric 10 may contain an orthorhombic phase as a crystal phase. The orthorhombic phase may have polarization in the out-of-plane direction. Therefore, when the dielectric 10 contains an orthorhombic phase as a crystal phase, the dielectric 10 is likely to exhibit ferroelectricity.

[0022] The dielectric 10 may have a monoclinic phase, a tetragonal phase, a cubic phase, and an orthorhombic phase. Thereby, the dielectric 10 is likely to exhibit ferroelectricity.

[0023] In the X-ray diffraction (XRD) pattern of the dielectric 10, 0.87 ≦ a / (a + b) ≦ 0.98 may be satisfied. Here, a is the peak area of the diffraction peak attributed to the reflection from the (111) plane of the cubic crystal phase in the X-ray diffraction pattern of the dielectric 10, and b is the peak area of the diffraction peak attributed to the reflection from the (001) plane of the cubic crystal phase in the X-ray diffraction pattern of the dielectric 10. According to such a configuration, the dielectric 10 is likely to exhibit ferroelectricity.

[0024] The peak area a indicates the peak area of the diffraction peak confirmed around 2θ = 30.2° in the XRD spectrum. This peak is the diffraction peak attributed to the reflection from the (111) plane of the cubic crystal phase. The peak area b indicates the area of the diffraction peak confirmed around 2θ = 35.4° in the XRD spectrum. This peak is the diffraction peak attributed to the reflection from the (001) plane of the cubic crystal phase.

[0025] In the present disclosure, the phrases "around 2θ = 30.2°" and "around 2θ = 35.4°" each mean "2θ = 30.2 ± 0.5°" and "2θ = 35.4 ± 0.5°", respectively.

[0026] In the orthorhombic crystal phase, when the (111) plane and the (001) plane are present, the dielectric 10 is likely to have polarization in the out-of-plane direction. As a result, the dielectric 10 is likely to exhibit ferroelectricity. On the other hand, in the orthorhombic crystal phase, when the (001) plane is present, the (010) plane is likely to coexist. When the (010) plane is present, the dielectric 10 is likely to have polarization in the in-plane direction and less likely to have polarization in the out-of-plane direction. When the dielectric 10 contains the (001) plane of the orthorhombic crystal phase, since the dielectric also contains the (010) plane, variations in dielectric properties are likely to occur. In the present embodiment, the dielectric 10 satisfies 0.87 ≤ a / (a + b) ≤ 0.98. According to such a configuration, the peak area of the diffraction peak attributed to the reflection from the (001) plane is smaller than the peak area of the diffraction peak attributed to the reflection from the (111) plane. That is, in the orthorhombic crystal phase, the proportion of the (001) plane is reduced compared to the proportion of the (111) plane. Along with this, in the orthorhombic crystal phase, the proportion of the (010) plane can also be reduced. That is, by satisfying 0.87 ≤ a / (a + b) ≤ 0.98, a dielectric 10 in which the (010) plane is less likely to be present can be obtained, so the dielectric 10 is likely to exhibit ferroelectricity. The dielectric 10 may satisfy 0.90 ≤ a / (a + b) ≤ 0.98.

[0027] The peak area a and the peak area b can be obtained as follows. XRD measurement is performed on the dielectric 10 to obtain an XRD pattern. For this XRD pattern, Peak Parameters processing is performed on the desired peaks using the analysis software Data Viewer of Malvern Panalytical. Thereby, the peak area a and the peak area b can be calculated. The desired peaks are the peaks around 2θ = 30.2° and the peaks around 2θ = 35.4°. The Peak Parameters processing is a function that can automatically calculate the net peak area. In addition, in the calculation of the peak area a and the peak area b, manual peak fitting and baseline adjustment are not performed.

[0028] The dielectric 10 may contain a solid solution of hafnium oxide and cerium oxide.

[0029] The manufacturing method of the dielectric 10 is not limited to a specific method. The manufacturing method of the dielectric 10 includes, for example, manufacturing a film for the dielectric and crystallizing the film for the dielectric.

[0030] In the manufacture of the film for the dielectric, for example, film formation methods such as RF magnetron sputtering method, pulsed laser deposition method (PLD), atomic layer deposition method (ALD), chemical vapor deposition method (CVD), mist CVD method, sol-gel method, hydrothermal method, anodic oxidation method, etc. can be used. For the crystallization of the film for the dielectric, for example, methods such as rapid thermal annealing (RTA) can be used. Thereby, the crystalline dielectric 10 can be obtained.

[0031] By appropriately adjusting the conditions in the manufacture of the dielectric 10, a dielectric 10 can be obtained in which the molar ratio of the oxygen content to the sum of the hafnium content and the cerium content is greater than 0 and less than or equal to 1.50. For example, by appropriately adjusting the environment in film formation and the environment in rapid thermal annealing, or by appropriately selecting the material of the electrode in contact with the dielectric 10, a dielectric 10 in which the molar ratio is greater than 0 and less than or equal to 1.50, and a functional element 1a using this dielectric 10 can be obtained.

[0032] As shown in FIG. 1, the functional element 1a includes a first electrode 21, a dielectric 10, and a second electrode 22. The dielectric 10 is located between the first electrode 21 and the second electrode 22. The dielectric 10 is disposed in contact with the first electrode 21. The second electrode 22 may cover at least a part of the dielectric 10. The first electrode 21 may be disposed on a support. Since the functional element 1a includes the dielectric 10, the chemical stability of the functional element 1a is likely to be improved.

[0033] FIG. 2 is a cross-sectional view showing another example of the functional element of the present disclosure. The functional element 1b shown in FIG. 2 is configured in the same manner as the functional element 1a, except for the parts to be specifically described. The components of the functional element 1b that are the same as or corresponding to the components of the functional element 1a are denoted by the same reference numerals, and detailed descriptions thereof are omitted. The description regarding the functional element 1a applies to the functional element 1b as well, unless there is a technical contradiction.

[0034] As shown in FIG. 2, in the functional element 1b, at least a part of the first electrode 21 is porous. According to such a configuration, the surface area of the first electrode 21 is likely to increase. Such a porous structure can be formed by etching a metal foil, sintering a powder, or the like.

[0035] As shown in FIG. 2, for example, a film of the dielectric 10 is formed on the surface of the porous portion of the first electrode 21. In this case, as a method for forming the dielectric 10, a chemical vapor deposition method such as an atomic layer deposition method (ALD method), a CVD method, or a mist CVD method can be employed.

[0036] The first electrode 21 may contain at least one selected from the group consisting of a metal, a conductive nitride, and a conductive oxide. Examples of the metal are Pt, Au, Al, Ta, and Zr. Examples of the conductive nitride are TiN and TaN. Examples of the conductive oxide are indium tin oxide (ITO), antimony tin oxide (ATO), and ZnO. The first electrode 21 preferably contains a metal. That is, the first electrode 21 preferably contains at least one selected from the group consisting of Pt, Au, Al, Ta, and Zr. The first electrode 21 may contain Al or may be Al.

[0037] The second electrode 22 may contain at least one selected from the group consisting of a metal, a conductive nitride, and a conductive oxide. Examples of the metal, the conductive nitride, and the conductive oxide are as described above.

[0038] The first electrode 21 and the second electrode 22 can be manufactured by methods such as RF magnetron sputtering method, pulsed laser deposition method (PLD), atomic layer deposition method (ALD), chemical vapor deposition method (CVD), mist CVD method, sol-gel method, hydrothermal method, vacuum evaporation method, etc.

[0039] In the functional elements 1a and 1b, an electrolyte 23 may be disposed between the first electrode 21 and the second electrode 22, more specifically, between the dielectric 10 and the second electrode 22. The electrolyte 23 may be in contact with the second electrode 22. The electrolyte 23 may be in contact with the dielectric 10. In the functional element 1b, the electrolyte 23 is disposed, for example, so as to fill the voids around the porous portion of the first electrode 21.

[0040] The electrolyte 23 contains, for example, at least one selected from the group consisting of an electrolytic solution, a conductive polymer, and manganese oxide. Examples of the conductive polymer are polypyrrole, polythiophene, polyaniline, and their derivatives. The electrolyte 23 may be a manganese compound such as manganese oxide. The electrolyte 23 may contain a solid electrolyte.

[0041] The functional elements 1a and 1b are not limited to specific elements. The functional elements 1a and 1b are, for example, at least one selected from the group consisting of a capacitor, an electro-optical element, a memory element, a transistor, a ferroelectric data storage, a piezoelectric element, and a pyroelectric element. For example, in these functional elements, the ferroelectricity of the dielectric 10 can be utilized. The functional elements 1a and 1b are preferably at least one selected from the group consisting of a capacitor and a memory element.

[0042] The functional elements 1a and 1b are disposed, for example, in at least one selected from the group consisting of an actuator, an inkjet head, a gyro sensor, a vibration power generation element, a surface acoustic wave resonator, a thin film bulk acoustic resonator, a piezoelectric mirror, and a piezoelectric sensor. In this case, in the actuator or the like, the piezoelectric effect associated with the ferroelectricity of the dielectric 10 can be utilized.

[0043] (Appendix) From the above description, the following technologies are disclosed.

[0044] (Technology 1) It contains an oxide containing hafnium and cerium, The molar ratio of the content of cerium to the sum of the content of hafnium and the content of cerium is 0.031 or more and 0.052 or less, The molar ratio of the content of oxygen to the sum is greater than 0 and 1.50 or less, Dielectric.

[0045] According to Technology 1, a novel dielectric 10 suitable for use in functional elements such as capacitors can be provided.

[0046] (Technology 2) The molar ratio of the content of oxygen to the sum is 1.44 or more and 1.50 or less, The dielectric described in Technology 1.

[0047] According to Technology 2, a chemically more stable dielectric 10 can be obtained.

[0048] (Technology 3) The dielectric has a composition represented by the compositional formula Hf 1-x Ce x O y and satisfies 0.031 ≤ x ≤ 0.052 and y ≤ 1.50, The dielectric described in Technology 1 or 2.

[0049] (Technology 4) Satisfies 1.44 ≤ y ≤ 1.50, The dielectric described in Technology 3.

[0050] (Technology 5) The dielectric contains a crystal phase having a fluorite-type crystal structure, The dielectric is a polycrystalline film, The dielectric described in any one of Technologies 1 to 4.

[0051] According to Technology 5, the dielectric 10 is likely to exhibit ferroelectricity.

[0052] (Technique 6) The dielectric includes a cubic phase, in the X-ray diffraction pattern of the dielectric, 0.87 ≦ a / (a + b) ≦ 0.98 is satisfied, where a is the peak area of the diffraction peak attributed to the reflection from the (111) plane of the cubic phase in the X-ray diffraction pattern, and b is the peak area of the diffraction peak attributed to the reflection from the (001) plane of the cubic phase in the X-ray diffraction pattern, The dielectric according to any one of Items 1 to 5.

[0053] According to Technique 6, the dielectric 10 is likely to exhibit ferroelectricity.

[0054] (Technique 7) A first electrode, a second electrode, and the dielectric according to any one of Items 1 to 6, located between the first electrode and the second electrode, Functional element.

[0055] According to Technique 7, since the functional element 1a includes the dielectric 10, the chemical stability of the functional element 1a is likely to be improved.

[0056] (Technique 8) At least a part of the first electrode is porous, The functional element according to Item 7.

[0057] According to Technique 8, the surface area of the first electrode 21 is likely to increase.

[0058] ] (Technique 9) The first electrode includes at least one selected from the group consisting of a metal, a conductive nitride, and a conductive oxide, The functional element according to Item 7 or 8.

[0059] (Technique 10) The first electrode includes at least one selected from the group consisting of Pt, Au, Al, Ta, and Zr. The functional element according to any one of Aspects 7 to 9.

[0060] (Aspect 11) The first electrode includes Al. The functional element according to any one of Aspects 7 to 10.

[0061] According to Aspects 9 to 11, since the dielectric 10 is provided, the chemical stability of the functional element 1a is likely to be improved.

[0062] (Aspect 12) The functional element further includes an electrolyte positioned between the second electrode and the dielectric. The electrolyte includes at least one selected from the group consisting of an electrolytic solution, a conductive polymer, and manganese oxide. The functional element according to any one of Aspects 7 to 11.

[0063] According to Aspect 12, the chemical stability of the functional element 1b provided with the electrolyte is likely to be improved.

[0064] (Aspect 13) The functional element is at least one selected from the group consisting of a capacitor, an electro-optical element, a memory element, a transistor, a ferroelectric data storage, a piezoelectric element, and a pyroelectric element. The functional element according to any one of Aspects 7 to 12.

[0065] According to Aspect 13, a functional element utilizing the ferroelectricity of the dielectric 10 can be provided.

[0066] (Aspect 14) The dielectric is in contact with the first electrode. The second electrode covers at least a part of the dielectric. The functional element according to any one of Aspects 7 to 13.

Example

[0067] Hereinafter, the present disclosure will be described in more detail based on examples. However, the present disclosure is not limited to the following examples.

[0068] (Preparation of Samples) As a substrate, a Si(111) wafer was used. A buffer layer of ZrO2 was formed on this substrate. The thickness of the buffer layer was 60 nm. On this buffer layer, a Pt(111) film was epitaxially grown to form a thin film as the lower electrode. The thickness of this thin film was 150 nm. In this way, a substrate with a lower electrode formed on the substrate was obtained.

[0069] Next, using HfO2 and CeO2 as targets, a film for the dielectric was formed on the lower electrode of the substrate by the RF magnetron sputtering method. The sputtering time was adjusted so that the thickness of the dielectric was 10 nm to 30 nm. In sputtering, the environment of the substrate was maintained at a pressure of 2 Pa where argon gas occupied 100% of the volume. The substrate was not heated.

[0070] Thereafter, the film for the dielectric was crystallized by rapid thermal annealing (RTA) to obtain a dielectric film. The environment in the rapid thermal annealing was maintained at a pressure of 1 atm in which nitrogen gas and oxygen gas were mixed at a desired ratio. The heat treatment in the rapid thermal annealing was carried out by a process of heating to 750 °C at a rate of 5 °C / sec, holding at this temperature for 30 seconds, and then naturally cooling. Thereafter, an Au film having a thickness of 150 nm was formed on the dielectric film by the vacuum evaporation method to obtain an Au electrode as the upper electrode. The diameter of the Au electrode was 200 μm. In this way, samples according to Examples 1 to 3 and samples according to Comparative Examples 1 to 4 were prepared.

[0071] (Evaluation of Composition) Using the X-ray photoelectron spectroscopy (XPS) apparatus JPS-9010TR manufactured by JEOL Ltd., the composition of the dielectric related to each sample was evaluated. First, after forming the upper electrode, X-ray photoelectron spectroscopy (XPS) was performed on the dielectric film related to each sample to obtain narrow spectra of the Hf4f orbital, Ce3d orbital, and O1s orbital of the dielectric film related to each sample. Based on the obtained spectra, the elemental concentrations of each element contained in the dielectric film related to each sample were determined using the analysis software SpecSurf attached to the above apparatus. Then, using the obtained elemental concentrations, when the composition formula of the dielectric was assumed to be Hf 1-x Ce x O y the values of x and y of the dielectric film related to each sample were determined. Specifically, the value of x was determined by calculating the ratio of the elemental concentration of Ce to the elemental concentrations of Hf and Ce. Also, the value of y was determined by calculating the ratio of the elemental concentration of O to the elemental concentrations of Hf and Ce. The results are shown in Table 1.

[0072] (Evaluation of dielectric properties) Using the ferroelectric tester PremierII manufactured by Radiant Technologies, after forming the upper electrode, Polarization-Electric field measurement was performed on the dielectric film related to each sample to obtain the P-E curve of the dielectric film related to each sample. Based on this P-E curve, the dielectric properties of the dielectric films according to the examples and comparative examples were evaluated. When the dielectric film showed ferroelectricity, it was evaluated as "A", and when it showed normal dielectricity, it was evaluated as "B". The results are shown in Table 1.

[0073] (Evaluation of crystal phase) The crystal phases contained in the dielectric films according to Examples 1 to 3 were evaluated using an X-ray diffractometer X’Pert PRO MPD manufactured by Malvern Panalytical. Before forming the upper electrode, X-ray diffraction measurements were performed on the dielectric films according to Examples 1 to 3 to obtain XRD patterns by 2θ / θ scan of each dielectric film. In this measurement, Cu-Kα rays were used as the X-ray source. Thereafter, with respect to the XRD patterns, the peak area a and the peak area b were calculated by the above-described method using the analysis software Data Viewer attached to the above apparatus. Thereafter, a / (a + b) was calculated. Here, the peak area a is the peak area of the diffraction peak attributed to the reflection from the (111) plane in the XRD spectrum of the dielectric. The peak area b is the peak area of the diffraction peak attributed to the reflection from the (001) plane in the XRD spectrum of the dielectric. Specifically, the value of a was determined by calculating the area of the peak confirmed around 2θ = 30.2°. The value of b was determined by calculating the area of the peak confirmed around 2θ = 35.4°. The results are shown in Table 1.

[0074] As shown in Table 1, the dielectrics according to Examples 1 to 3 exhibited ferroelectricity. In the dielectrics according to Examples 1 to 3, in the composition formula Hf 1-x Ce x O y , 0.031 ≦ x ≦ 0.052 and 0 < y ≦ 1.50 were satisfied. In the dielectrics according to Examples 1 to 3, since the addition concentration of Ce was reduced, it can be understood that the chemical stability was improved.

[0075] FIG. 3 is a graph showing the relationship between polarization and electric field strength in the dielectric films according to Examples 1 to 3. In FIG. 3, the vertical axis represents polarization and the horizontal axis represents electric field strength. As shown in FIG. 3, in the dielectric films according to Examples 1 to 3, when the electric field strength was 0 MV / cm, the polarization was not 0 μC / cm 2 but a remanent polarization was observed. That is, the dielectrics according to Examples 1 to 3 exhibited ferroelectricity.

[0076] FIG. 4 is a graph showing the relationship between polarization and electric field strength in the dielectric films according to Comparative Examples 1 to 4. In FIG. 4, the vertical axis represents polarization and the horizontal axis represents electric field strength. As shown in FIG. 4, in the dielectric films according to Comparative Examples 1 to 4, when the electric field strength was 0 MV / cm, the polarization was not 0 μC / cm 2 . This polarization was the polarization derived from the leakage current. The dielectric films according to Comparative Examples 1 to 4 did not exhibit ferroelectricity. The dielectrics according to Comparative Examples 1 to 4 had normal dielectric properties.

[0077] FIG. 5 is a graph showing the X-ray diffraction patterns of the dielectrics according to Examples 1 to 3. As shown in FIG. 5, in the dielectric films according to Examples 1 to 3, peaks were observed near 2θ = 30.2° and near 2θ = 35.4°. In addition, as shown in Table 1, in Examples 1 to 3, 0.87 ≦ a / (a + b) ≦ 0.98 was satisfied. This result indicates that the dielectrics used in Examples 1 to 3 are excellent from the viewpoint of exhibiting ferroelectricity.

[0078]

Table 1

Industrial Applicability

[0079] The dielectric of the present disclosure is advantageous from the viewpoint of improving chemical stability.

Explanation of Reference Numerals

[0080] 1a, 1b Functional elements 10 Dielectric 21 First electrode 22 Second electrode 23 Electrolyte

Claims

1. A dielectric having a composition represented by the compositional formula Hf1−x Cex Oy, satisfying 0.031 ≦ x ≦ 0.052 and 1.44 ≦ y ≦ 1.

50. The dielectric.

2. The dielectric includes a crystal phase having a fluorite-type crystal structure. The dielectric is a polycrystalline film. The dielectric according to claim 1.

3. The dielectric includes an orthorhombic phase. In the X-ray diffraction pattern of the dielectric, 0.87 ≦ a / (a + b) ≦ 0.98 is satisfied, where a is the peak area of the diffraction peak attributed to the reflection from the (111) plane of the orthorhombic phase in the X-ray diffraction pattern, and b is the peak area of the diffraction peak attributed to the reflection from the (001) plane of the orthorhombic phase in the X-ray diffraction pattern. The dielectric according to claim 1.

4. A first electrode, A second electrode, And a dielectric according to any one of claims 1 to 3, located between the first electrode and the second electrode. The functional device.

5. At least a part of the first electrode is porous. The functional device according to claim 4.

6. The first electrode includes at least one selected from the group consisting of metals, conductive nitrides, and conductive oxides. The functional device according to claim 4.

7. The first electrode includes at least one selected from the group consisting of Pt, Au, Al, Ta, and Zr. The functional device according to claim 4.

8. The first electrode includes Al. The functional device according to claim 4.

9. The functional device further includes an electrolyte located between the second electrode and the dielectric. The electrolyte includes at least one selected from the group consisting of electrolytic solutions, conductive polymers, and manganese oxides. The functional device according to claim 4.

10. The functional device is at least one selected from the group consisting of capacitors, electro-optical devices, memory devices, transistors, ferroelectric data storage, piezoelectric devices, and pyroelectric devices. The functional device according to claim 4.

11. The dielectric is in contact with the first electrode. The second electrode covers at least a part of the dielectric. The functional device according to claim 4.

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