Oxide film and dielectric element including the same

Abstract

To provide an oxide film, etc., having a small change rate of capacitance even in high temperature though having a high specific inductive capacity.SOLUTION: An oxide film includes an oxide crystal phase having Wadsley-Roth structure as a main crystal phase. A specific inductive capacity at 25°C is 125 or more at a frequency of 0.1 kHz or more and 100 kHz or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an oxide thin film containing an oxide crystal phase having the Wadsley-Roth structure as the main crystal phase, and is suitable for inclusion in dielectric elements such as capacitors because it exhibits a high relative dielectric constant. [Background technology]

[0002] In recent years, as electronic devices become more sophisticated, more integrated, and more compact, the space occupied by the various electronic components that make them up is also shrinking, and there is a demand for similar miniaturization of dielectric elements such as multilayer ceramic capacitors (MLCCs). As an example, in the automotive market, electronic control of various functions is rapidly progressing with the aim of improving safety and environmental performance, and the rate of electronic equipment installed in cars is increasing, so there is a strong demand for miniaturization of electronic equipment. In particular, electronic equipment installed in the engine room is installed in a harsh temperature environment, so the demand for electronic components that are high-capacity and can operate stably even in high-temperature environments of 150°C or more is increasing year by year.

[0003] BaTiO is a typical dielectric material used in MLCCs. 3 However, it is known that while it exhibits a very high relative dielectric constant, its relative dielectric constant drops sharply at around 120°C. 3 In the case of titanium oxide dielectrics such as these, in addition to problems such as deterioration of the substrate interface due to thermal annealing in the manufacturing process and the resulting composition shift and electrical inconsistency, many of these dielectrics have fundamental problems in that when they are thinned to achieve miniaturization and high capacity, the size effect reduces the relative dielectric constant and increases the leakage current. From the perspective of stable operation in high temperature environments, CaZrO, which exhibits paraelectric properties, is considered to be a dielectric that satisfies these requirements. 3 and TiO 2 However, these dielectric materials have low relative dielectric constants and therefore cannot provide a high-capacitance capacitor.

[0004] To address this issue, for example, Non-Patent Document 1 describes2 O-K 2 O-Nb 2 O 5 In the system, the dielectric properties of a thin film containing a tungsten bronze-type crystal phase produced by pulsed laser deposition have been reported. Further, in Patent Document 1, the dielectric properties of a laminate composed of a tungsten bronze-type crystal phase containing Ba, a rare earth element, and Ti as constituent elements and a pyrochlore-type crystal phase containing a rare earth element and Ti as constituent elements have been reported, but in all cases, it was necessary to further increase the relative dielectric constant.

[0005] In addition, as another use of the above dielectric, it is widely known that it is also used in resonance circuits and filter circuits, which applies the tunable property that the capacitance, that is, the relative dielectric constant changes by voltage application. A ferroelectric such as BaTiO 3 showing a relatively large tunability (the rate of change of the relative dielectric constant under an electric field) and a relaxor ferroelectric that causes a diffuse phase transition and changes in dielectric constant have attracted attention. The essence of this large tunability is the property brought about by its high relative dielectric constant, but it is not suitable from the viewpoint of impedance matching, and its realization in ferroelectrics has been essentially difficult.

[0006] In Non-Patent Document 2, the tunable properties of a Bi 1.5 ZnNb 1.5 O 7 thin film having a pyrochlore-type structure have been reported, but the tunability at about 1 MV / cm is as small as about 40 to 28%, and it was necessary to further increase the tunability.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Non-Patent Documents

[0008]

Non-Patent Document 1

[0009] In order to solve the above problems, an object of the present invention is to provide an oxide thin film having a high relative permittivity and a small capacitance change rate even at high temperatures, and a dielectric element including the oxide thin film. In addition, it is also an object of the present invention to provide an oxide thin film having excellent tunable characteristics. [Means for Solving the Problems]

[0010] The present inventor has intensively studied and found an oxide thin film that can solve the above problems in a composition system different from the existing technology, and completed the present invention. The present invention is as follows (1) to (7). (1) An oxide thin film including a crystal phase of an oxide having a Wadsley-Roth structure as a main crystal phase, and having a relative permittivity of 125 or more at 25 ° C. in a frequency range of 0.1 kHz or more and 100 kHz or less. (2) The oxide thin film according to (1), having a capacitance change rate of ± 30% or less at 25 ° C. or more and 200 ° C. or less. (3) The oxide thin film according to (1) or (2), having a tunability T of T ≧ 50% under an electric field of 100 kV / cm. (4) The oxide thin film according to any one of (1) to (3), wherein the crystal phase of the oxide contains one or more elements selected from the group consisting of Ta and Nb, and one or more elements selected from the group consisting of P, Ge, and V. (5) The oxide thin film according to any one of (1) to (4), wherein the energy efficiency η is 50% or more under an electric field of 30 kV / cm or more and 350 kV / cm or less. (6) A dielectric element including the oxide thin film according to any one of (1) to (5). (7) An electronic component including the dielectric element according to (6).

Advantages of the Invention

[0011] According to the present invention, it is possible to provide an oxide thin film having a high relative permittivity and a small change rate of capacitance even at high temperatures, and a dielectric element including the oxide thin film. Furthermore, it is also possible to provide an oxide thin film having excellent tunable characteristics.

Brief Description of the Drawings

[0012]

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Mode for Carrying Out the Invention

[0013] The present invention will be described. The present invention is an oxide thin film characterized in that, as a main crystal phase, it contains a crystal phase of an oxide having a Wadsley-Roth structure, and the relative permittivity at 25 ° C. is 125 or more in the frequency range of 0.1 kHz or more and 100 kHz or less. In the following, this may also be referred to as "the oxide thin film of the present invention".

[0014] The oxide thin film of the present invention is a material obtained by heat-treating an amorphous oxide thin film to precipitate a dielectric crystal phase in the oxide thin film. This oxide thin film may be an oxide thin film composed of an amorphous phase and a crystal phase, or an oxide thin film in which the amorphous phase has all changed to a crystal phase, that is, an oxide thin film with a crystallinity of 100%. The preferred form of the crystal phase in the oxide thin film of the present invention will be described later.

[0015] Since the oxide thin film of the present invention has a high relative permittivity and a small change rate of capacitance in the temperature range from 25 ° C. to 200 ° C., it is suitable for use in dielectric elements such as capacitors for high-temperature applications. Further, since the oxide thin film of the present invention also has a high dielectric breakdown strength, it can be suitably used in applications with large capacitance and high voltage.

[0016] In the composition and the like of each component constituting the oxide thin film of the present invention, when simply denoted as "%", it shall mean "mol%". In addition, in the present specification, all compositions expressed as "%" shall mean percentages in terms of the total amount of substances in the oxide-converted composition. Here, the "oxide-converted composition" refers to a composition assuming that the oxide thin film of the present invention and oxides, nitrates, etc. used as raw materials for the constituent components of the target used during film formation are all decomposed and changed into oxides. Therefore, the "percentage in terms of the total amount of substances in the oxide-converted composition" means that the total mass of the generated oxides when all components are present as oxides is set to 100 mol%, and represents the abundance of each component relative thereto.

[0017] The thickness (film thickness) of the oxide thin film of the present invention may be, for example, 10 nm or more and 10 μm or less, and further may be 100 nm or more and 1 μm or less. The area (film formation area) of the oxide thin film of the present invention may be, for example, 1 μm 2 or more and 500 mm 2 or less. Further, the oxide thin film of the present invention may have a laminated structure.

[0018] The composition of the oxide thin film of the present invention may be determined, for example, by analysis methods such as X-ray fluorescence analysis (XRF method), inductively coupled plasma (ICP) emission analysis, and energy dispersive X-ray spectroscopy (EDX method). The crystal phase and crystal structure deposited on this oxide thin film may be determined by X-ray diffraction (XRD) method.

[0019] The oxide thin film of the present invention may be formed, for example, by the following method.

[0020] As raw materials for the oxide thin film of the present invention, three types of targets of ceramics, glass, or crystallized glass may be used. The method for producing the ceramic target is as follows.

[0021] Weigh and mix raw materials so as to obtain the target composition ratio to obtain a raw material mixture. Examples of the mixing method include ball mill mixing using balls such as zirconia and mixing using a mixer. Further, in these mixings, wet mixing or dry mixing may be mentioned, and either may be appropriately selected.

[0022] The obtained raw material mixture may be calcined at any temperature. The calcined product may be pulverized using balls such as zirconia, and this may be formed by biaxial pressure molding or cold isostatic pressing in which it is filled into a mold and compression-pressed (pressed). The shape of the formed body is not particularly limited and may be appropriately determined.

[0023] The sintering conditions of the obtained formed body may be appropriately determined according to the composition. The sintering temperature is preferably 900°C or higher and 1400°C or lower, and the holding time is preferably 1 hour or longer and 48 hours or shorter.

[0024] A ceramic target is obtained by the above steps.

[0025] The method for producing a glass target and a crystallized glass target is as follows. (i) A step of melting raw materials weighed and mixed to have a target composition and cooling the melt to obtain a glass, and, if necessary, (ii) a crystallization step of converting the glass into a crystallized glass by heat-treating the glass at a temperature above its glass transition point.

[0026] (1) Step (i) The raw materials weighed and mixed to have a target composition are put into a platinum crucible, a quartz crucible, or an alumina crucible and melted in an electric furnace or a combustion furnace in a temperature range of 1200°C or higher and 1500°C or lower for 1 hour or longer and 24 hours or shorter, homogenized by stirring, and then the melt is rapidly cooled to form a glass. The raw materials are not particularly limited, and raw materials such as oxides, hydroxides, carbonates, nitrates, fluorides, chlorides, and metaphosphate compounds may be appropriately selected, and the vitrification conditions may be appropriately set according to the glass composition, the melting amount, etc.

[0027] (2) Step (ii) The crystallization step involves heat-treating the glass obtained in step (i) to convert it into a crystallized glass. This heat treatment is carried out at a temperature above the glass transition point of the glass. The glass transition point (Tg) varies depending on the composition but is generally in the range of 500°C or higher and 750°C or lower. The upper limit of the heat treatment temperature is not particularly limited, but it is preferably set to a temperature 400°C higher than the temperature indicating the crystallization peak observed by DTA measurement. The maximum crystallization temperature of the glass varies greatly depending on the composition but is generally in the range of 650°C or higher and 1100°C or lower. Also, the heat treatment time is the time that can convert the glass into a crystallized glass. It is shorter when the heat treatment temperature is high and longer when it is low, and it is usually in the range of 0.1 hour or more and 100 hours or less. Note that this crystallization step may be a one-step heat treatment or may go through a heat treatment process of two steps or more.

[0028] A glass target is obtained by the above step (i), and a crystallized glass target is obtained by the above steps (i) and (ii).

[0029] An oxide thin film may be formed by a vapor phase growth method using at least one of the above three types of targets. In the vapor phase growth method, in a vacuum atmosphere, the elements constituting the target are evaporated. The evaporated elements adhere and deposit on an electrode layer or the like, whereby an oxide thin film grows. The vapor phase growth method may be, for example, a sputtering method, an electron beam evaporation method, a chemical vapor deposition (CVD) method, or a pulsed laser deposition (PLD) method. Hereinafter, this pulsed laser deposition method is referred to as the PLD method. By using these vapor phase growth methods, it is possible to form a dense oxide thin film at the atomic level, and segregation of elements in the oxide thin film is suppressed. Depending on the type of vapor phase growth method, the excitation source is different. The excitation source of the sputtering method is Ar plasma. The excitation source of the electron beam evaporation method is an electron beam. The excitation source of the PLD method is laser light (for example, a YAG laser or an excimer laser, etc.). When these excitation sources irradiate the target, the elements constituting the target are evaporated.

[0030] Among the above-described vapor deposition methods, the PLD method is relatively excellent in the following respects. In the PLD method, each element constituting the target can be instantaneously and uniformly turned into plasma by a pulsed laser. Therefore, an oxide thin film having substantially the same composition as the target is likely to be formed. Also, in the PLD method, it is easy to control the thickness of the oxide thin film by changing the number of laser pulses (repetition frequency).

[0031] In the PLD method, the film-forming pressure (oxygen partial pressure) in the vacuum chamber may be, for example, 10 mTorr or more and 400 mTorr or less, 10 mTorr or more and 300 mTorr or less, or 10 mTorr or more and 200 mTorr or less. In other words, the film-forming pressure in the vacuum chamber may be, for example, 1 Pa or more and 53 Pa or less, 1 Pa or more and 40 Pa or less, or 1.3 Pa or more and 30 Pa or less.

[0032] After forming the oxide thin film, the oxide thin film of the present invention containing a dielectric crystal phase can be produced by performing annealing treatment (heat treatment). The annealing temperature may be, for example, 300°C or more and 1200°C or less, 500°C or more and 1000°C or less, or 700°C or more and 900°C or less.

[0033] The oxide thin film of the present invention contains, as the main crystal phase, a crystal phase of an oxide having a Wadsley-Roth structure. And this crystal phase of the oxide having a Wadsley-Roth structure can be formed by forming an oxide thin film with a predetermined thickness from a target with a predetermined composition by a vapor deposition method and then annealing this oxide thin film under predetermined conditions, and an oxide thin film of the present invention having a predetermined relative permittivity and the like can be obtained. Examples of the composition of the crystal phase of the oxide having a Wadsley-Roth structure include PNb 9 O 25 , GeNb 18 O 47 , VNb 9 O 25 , VTa 9 O 25, and one or more selected from the group consisting of these solid solutions. In the oxide thin film of the present invention, since the effects of the present invention are more easily exhibited, the crystal phase of the oxide having this Wadsley-Roth structure is, as an essential component, one or more elements selected from the group consisting of Ta and Nb, and one or more elements selected from the group consisting of P, Ge, and V. It is more preferable to contain, and it is even more preferable to contain Nb and P or Ge.

[0034] Here, the "main crystal phase" means a crystal phase that accounts for more than 50% (more than 50 mol%) of all the crystal phases contained in the oxide thin film of the present invention. This is preferably 55% or more, more preferably 60% or more, even more preferably 65% or more, even more preferably 70% or more, even more preferably 75% or more, even more preferably 80% or more, even more preferably 85% or more, even more preferably 90% or more, even more preferably 95% or more, and even more preferably 99% or more. Also, the "solid solution" refers to a solid (crystalline solid) in which a crystal phase as exemplified above and other elements are mutually dissolved to form a uniform solid phase. There are two types: a substitution type in which atoms existing at lattice points in the crystal structure are replaced by other atoms, and an interstitial type in which other atoms enter the gaps between these lattice points. For example, a solid solution in which a Ge component is dissolved in PNb 9 O 25 , a solid solution of (P,Ge)Nb 9 O 25 in which a Ta component is dissolved in PNb 9 O 25 , a solid solution of P(Nb,Ta) 9 O 25 in which a V component is dissolved in PNb 9 O 25 , a solid solution of (P,V)Nb 9 O 25 are exemplified, but not limited thereto. And this crystal phase may be determined by analyzing the XRD pattern obtained by the X-ray diffraction (XRD) method using an X-ray diffractometer (such as D8 DISCOVER manufactured by Bruker) (for example, separating diffraction peaks from each other after function fitting of diffraction peaks and analyzing the area ratio thereof, or analysis by the Rietveld method).

[0035] Further, although not limited, as an example of the composition range of the components constituting the oxide thin film of the present invention, Ta 2 O 5 component, Nb 2 O 5 component, or the total content thereof may be 30.0% or more, further 35.0% or more, further 40.0% or more, and the upper limit may be 90.0% or less, further 85.0% or less, further 80.0% or less, further 75.0% or less, further 70.0% or less, further 65.0% or less, further 60.0% or less, further 55.0% or less. Further, P 2 O 5 component, GeO 2 component, V 2 O 5 component, or the total content thereof may be 10.0% or more, further 15.0% or more, further 20.0% or more, further 25.0% or more, and the upper limit may be 40.0% or less, further 35.0% or less, further 30.0% or less. In addition, SiO 2 component, Al 2 O 3 component, CaO component, BaO component, ZnO component, or the total content thereof may be 35.0% or less, further 30.0% or less, further 25.0% or less, further 20.0% or less, further 15.0% or less, further 10.0% or less, further 5.0% or less.

[0036] The oxide thin film of the present invention has a relative permittivity ε r of 125 or more at 25 ° C. and a frequency of 0.1 kHz or more and 100 kHz or less. This relative permittivity ε ris more preferably 130 or more, still more preferably 135 or more, still more preferably 150 or more, still more preferably 175 or more, and still more preferably 200 or more. In the oxide thin film of the present invention, the relative dielectric constant is measured for capacitance and dielectric loss (tan δ) using an impedance analyzer (for example, E4990A manufactured by Keysight Technologies), and C = ε 0 ε r S / d (where C is capacitance, ε 0 is the permittivity of vacuum, ε r is the relative dielectric constant of the material, S is the electrode area, and d is the sample thickness) is calculated from the formula.

[0037] The film thickness of the oxide thin film of the present invention can be measured by analysis software after obtaining an SEM image of the cross-section of this oxide thin film with a scanning electron microscope (for example, IT700-HR manufactured by JEOL Ltd.).

[0038] In the oxide thin film of the present invention, as shown in FIG. 1, the recoverable energy density W rec and the loss energy density W loss are calculated by integrating the P-E hysteresis loop. And the energy efficiency η (%) is the ratio of the recoverable energy density to the total value of the recoverable energy density and the loss energy density. The recoverable energy density of the oxide thin film of the present invention is preferably 0.01 J / cm 3 or more, more preferably 0.03 J / cm 3 or more, still more preferably 0.06 J / cm 3 or more, and still more preferably 0.1 J / cm 3 or more. The loss energy density is preferably 0.5 J / cm 3 or less, more preferably 0.4 J / cm 3 or less, and still more preferably 0.3 J / cm 3The following are more preferable. The energy efficiency is preferably 50% or more, more preferably 55% or more, and even more preferably 60% or more under an electric field of 30 kV / cm or more and 350 kV / cm or less. Further, this energy efficiency is preferably 50% or more, more preferably 55% or more, even more preferably 60% or more, and still more preferably 65% or more under an electric field of 30 kV / cm or more and 130 kV / cm or less.

[0039] The tunability T represents the rate of change of the dielectric constant under a constant DC electric field, and is calculated by (ε 0 -ε E ) / ε 0 ×100. In the formula, ε 0 is the dielectric constant when the electric field is 0 kV / cm, and ε E represents the dielectric constant when the electric field is applied. The larger the tunability, the wider the adjustment range of the capacitance of the capacitor by the DC bias voltage. Therefore, for this value in the oxide thin film of the present invention, it is preferable that the tunability T is T≧50% (50% or more) under an electric field of 100 kV / cm, more preferably T≧55% (55% or more), even more preferably T≧60% (60% or more), and still more preferably T≧65% (65% or more).

[0040] The rate of change of the capacitance represents the degree of change in capacitance accompanying temperature change with respect to the capacitance at the reference temperature (25°C). It can be said that the smaller this change range, the better the temperature characteristics. Therefore, the rate of change of the capacitance of the oxide thin film of the present invention is more preferably within ±30% in the temperature range of 25°C or more and 200°C or less, and even more preferably within ±28% in the temperature range of 25°C or more and 200°C or less. Further, this rate of change of the capacitance is preferably within ±30% in the temperature range of 25°C or more and 150°C or less, more preferably within ±20% in the temperature range of 25°C or more and 150°C or less, and even more preferably within ±15% in the temperature range of 25°C or more and 150°C or less.

[0041] The applications of the oxide thin film according to this embodiment are diverse. For example, the oxide thin film of the present invention may be used in dielectric elements such as MLCCs and gate oxides for transistors. Among these types of dielectric elements, those having a high relative dielectric constant are applied to various electronic components and used in all electronic devices. In addition, since the oxide thin film of the present invention also has a high dielectric breakdown strength, it may be used as a dielectric for high voltage. Furthermore, since the oxide thin film of the present invention is also excellent in tunable characteristics, it may be used as a dielectric element such as a variable capacitance element.

Example

[0042] Hereinafter, the present invention will be described more specifically by way of examples, but the present invention is not limited to these examples.

[0043] (Example 1) Composition: 29.0P 2 O 5 -4.5SiO 2 -1.5Al 2 O 3 -40.0Nb 2 O 5 -5.0BaO - 5.0CaO - 15.0ZnO (mol%) In the production of the oxide thin film, fused quartz (SiO 2 ) on which a Pt electrode was formed as a film-forming substrate and glass having the above composition as a target were used. By the PLD method, film formation was carried out under the conditions shown in Table 1, and as a result of confirming the crystal phase of the oxide thin film immediately after film formation with an X-ray diffractometer (D8 DISCOVER manufactured by Bruker), a halo pattern peculiar to amorphous was confirmed. After heat-treating the obtained amorphous oxide thin film at 900 °C for 10 min and then confirming the crystal phase, as a main crystal phase, an X-ray diffraction pattern resulting from the crystal phase of an oxide having a Wadsley-Roth structure of PNb 9 O 25 was obtained (Figure 2). When the film thickness of this oxide thin film was measured with a scanning electron microscope (IT700-HR manufactured by JEOL Ltd.), the film thickness was 720 nm. Figure 3 shows a transmission electron micrograph and an electron diffraction pattern of the oxide thin film of Example 1. As shown in Figure 3(a), from the electron diffraction pattern, PNb9 O 25 was confirmed to be deposited in the film. The capacitance and dielectric loss at 25 °C were measured using an impedance analyzer (manufactured by Keysight Technologies, E4990A), and the relative permittivity was calculated. Fig. 4 shows the frequency dependence of the relative permittivity and dielectric loss of this oxide film at 25 °C. At 25 °C, the relative permittivity and dielectric loss of this oxide film at 1 kHz were 297 and 0.061, respectively. Fig. 5 shows the results of examining the polarization-electric field characteristics (P-E hysteresis loop) of Example 1. Fig. 6 shows the relationship between the electric field and the recoverable energy density of Example 1, Fig. 7 shows the relationship between the electric field and the loss energy density of Example 1, and Fig. 8 shows the relationship between the electric field and the energy efficiency of Example 1. The hysteresis loop shows an S curve, and the recoverable energy density (W rec ), loss energy density (W loss ) and energy efficiency (η) calculated from this hysteresis loop were 0.29 J / cm 3 , 0.15 J / cm 3 and 66%, respectively. Fig. 9 shows the tunable characteristics of Example 1. The tunability under an electric field of 100 kV / cm showed a high value of 71%. Fig. 10 shows the temperature dependence of this capacitance. It can be seen that the change rate of the capacitance is within 20% over a wide temperature range from 25 °C to 150 °C, and it has excellent stability against temperature changes.

[0044] (Example 2) Composition: 18.2 GeO 2 - 81.8 Nb 2 O 5 (mol%) Using GeNb 9 O 25 ceramics having the above composition as a target, an oxide film was fabricated under the conditions shown in Table 1 by the same method as in Example 1, and heat treatment was performed under the conditions of 1000 °C for 120 min. Measurements were carried out in the same manner as in Example 1. The film thickness of this oxide film was 462 nm, and the relative permittivity and dielectric loss at 1 kHz at 25 °C were 218 and 0.026, respectively.

[0045] (Example 3) Composition: 10.0P 2 O 5 -90.0 Nb 2 O 5 (mol%) Using PNb 9 O 25 ceramics with the above composition as the target, an oxide thin film was fabricated under the conditions of Table 1 in the same manner as in Examples 1 and 2, and heat treatment was performed under the conditions of 1000 °C for 10 min. Measurement was carried out in the same manner as in Example 1. The film thickness of this oxide thin film was 563 nm, and the relative permittivity and dielectric loss at 1 kHz at 25 °C were 178 and 0.044, respectively. This oxide thin film showed a linear hysteresis loop, and the hysteresis disappeared at 137 kV / cm. The recoverable energy density (W rec ), loss energy density (W loss ), and energy efficiency (η) calculated from this hysteresis loop were 0.10 J / cm 3 , 0.036 J / cm 3 , and 73%, respectively.

[0046] (Comparative Example 1) Composition: Nb 2 O 5 Using Nb 2 O 5 ceramics as the target, an oxide thin film was fabricated under the conditions of Table 1 in the same manner as in Examples 1 to 3, and heat treatment was performed under the conditions of 900 °C for 10 min. Measurement was carried out in the same manner as in Example 1. The film thickness of this oxide thin film was 601 nm, and in the XRD analysis, Nb 2 O 5And an X-ray diffraction pattern resulting from an oxide crystal with Nb in a reduced state was obtained (Figure 2). Figure 4 shows the frequency dependence of the relative permittivity and dielectric loss of the oxide thin film of Comparative Example 1 at 25°C. At 25°C, the relative permittivity and dielectric loss of this oxide thin film at 1 kHz were 104 and 0.043, respectively. The hysteresis loop was linear, the hysteresis disappeared at 80 kV / cm, and an electric field of 111 kV / cm or more could not be applied. The recoverable energy density (W rec ), loss energy density (W loss ), and energy efficiency (η) calculated from the hysteresis loop were 0.054 J / cm 3 , 0.018 J / cm 3 , and 74%, respectively. Figure 5 shows the result of examining the polarization-electric field characteristics (P-E hysteresis loop) of Comparative Example 1. Figure 6 shows the relationship between the electric field and the recoverable energy density of Comparative Example 1. Figure 7 shows the relationship between the electric field and the loss energy density of Comparative Example 1. Figure 8 shows the relationship between the electric field and the energy efficiency of Comparative Example 1.

[0047] [Table 1]

Claims

Claim 1 An oxide thin film comprising a crystal phase of an oxide having a Wadsley-Roth structure as a main crystal phase, with a relative permittivity of 125 or more at a frequency of 0.1 kHz or more and 100 kHz or less at 25°C. Claim 2 The oxide thin film according to claim 1, wherein the change rate of capacitance at 25°C or more and 200°C or less is within ±30%. Claim 3 The oxide thin film according to claim 1 or 2, wherein the tunability T is T≧50% under an electric field of 100 kV / cm. Claim 4 The oxide thin film according to claim 1 or 2, wherein the crystal phase of the oxide contains one or more elements selected from the group consisting of Ta and Nb, and one or more elements selected from the group consisting of P, Ge, and V. Claim 5 The oxide thin film according to claim 1 or 2, wherein the energy efficiency η is 50% or more under an electric field of 30 kV / cm or more and 350 kV / cm or less. Claim 6 A dielectric element including the oxide thin film according to claim 1 or 2. Claim 7 An electronic component including the dielectric element according to claim 6.

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