JP2008270514A - Piezoelectric thin-film element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric thin-film element containing a potassium sodium niobate thin film having excellent piezoelectric characteristics. <P>SOLUTION: The piezoelectric thin-film element 8 has a structure in which at least a lower electrode 2 such as platinum, a piezoelectric thin-film 3 having a perovskite structure represented by general formula (K<SB>x</SB>Na<SB>1-x</SB>)NbO<SB>3</SB>(0<x<1) and having a film thickness of 0.2-10 μm, and an upper electrode 4 such as platinum are disposed on a substrate 1, wherein the composition of K, Na and Nb in the piezoelectric thin-film 3 satisfies the relation 1.15<(K+Na)/Nb<1.50. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a piezoelectric thin film element.

  Piezoelectric materials are processed into various piezoelectric elements according to various purposes, and actuators that deform when voltage is applied to the elements, and conversely, deformation occurs when pressure is applied to the elements. It is widely used as a functional electronic component such as a sensor that generates a voltage in response.

As a piezoelectric material used for actuators and sensors, a lead-based ferroelectric material having excellent piezoelectric characteristics, particularly a Pb (Zr _1-x Ti _x ) O ₃ perovskite-type strong material called PZT. Dielectric materials have been widely used so far, and such ferroelectric materials are usually produced by sintering oxide powders composed of individual elements.

On the other hand, in recent years, various electronic components have been reduced in size and performance, and accordingly, piezoelectric elements such as actuators have been required to be further downsized. In such a case, the piezoelectric material is required to have a thin film shape with a film thickness of several μm to several tens of μm, and a method of forming a thin film on an appropriate substrate is used.
A piezoelectric material manufactured by a manufacturing method centering on a sintering method, which is a conventional manufacturing method, has a relatively large crystal grain, and therefore has a great problem in promoting thinning in accordance with the recent demand for miniaturization. That is, when the film thickness is about 10 μm, the film thickness approaches the size of the crystal grains constituting the material, so the influence of the characteristics of the individual crystal grains cannot be ignored. For this reason, there arises a problem that variation and deterioration of characteristics become remarkable.
Further, it is difficult to say that processing a solid sintered body into a thin film shape is a realistic method from an economic and industrial standpoint.
For these reasons, a method for forming a piezoelectric material using a thin film forming technique instead of a sintering method has been actively studied in recent years. Examples of the thin film forming technique include a sputtering method (see Patent Document 1), a PLD (laser ablation method), a sol-gel method, and the like. Recently, PZT thin films formed by RF sputtering have been put to practical use as head actuators for high-definition high-speed ink jet printers (see Patent Document 2).
On the other hand, the piezoelectric sintered body or piezoelectric thin film made of PZT described above contains about 60 to 70% by weight of lead, which is not preferable from the viewpoint of ecology and pollution prevention. Therefore, development of a piezoelectric material that does not contain lead is desired in consideration of the environment.

Currently, various lead-free piezoelectric materials have been studied, among which potassium sodium niobate (general formula: (K _x Na _1-x ) NbO ₃ (0 <x <1)). This potassium sodium niobate is a material having a perovskite structure and exhibits relatively good piezoelectric characteristics as a non-lead material, and thus is expected as a promising candidate for a non-lead piezoelectric material.

The potassium sodium niobate sintered body has excellent piezoelectric characteristics in the general formula: (K _x Na _1-x ) NbO ₃ (0 <x <1) near the composition ratio x = 0.5. However, at present, a thin film of potassium sodium niobate does not realize piezoelectric characteristics comparable to the sintered body even though it has the same composition as the sintered body.

In the prior art, the niobic acid compound has been studied for the degree of orientation of the perovskite crystal structure in order to obtain a piezoelectric thin film element having sufficient piezoelectric characteristics (see Patent Document 3), the niobic acid compound Since the withstand voltage of the thin film is very low, the withstand voltage has been studied in order to withstand practical use (see Patent Document 4), but the composition ratio of (K + Na) / Nb has been studied. There is no.

JP 2002-151754 A Japanese Patent Laid-Open No. 11-135850 JP 2007-19302 A JP 2007-42740 A

The potassium sodium niobate crystal has an orthorhombic perovskite structure. K, Na (metal R) are arranged at each vertex of the orthorhombic crystal, Nb (metal M) is arranged at the body center, and oxygen O is arranged at each face center of the orthorhombic crystal around the metal M. The orientation of the NbO ₆ octahedron composed of oxygen and metal M is easily distorted by the interaction with the metal R, thereby causing a phase transition to a less symmetric tetragon. Due to this phase transition, the physical properties of the crystal change.
Therefore, unless the composition of K, Na and Nb constituting potassium sodium niobate is studied, it is difficult to change the crystal properties of the potassium sodium niobate thin film, and it is considered that excellent piezoelectric characteristics cannot be obtained.
As described above, the conventional potassium sodium niobate thin film does not give any consideration to the composition of K, Na and Nb, which causes a decrease in piezoelectric characteristics.

  An object of the present invention is to provide a piezoelectric thin film element using a potassium sodium niobate thin film having excellent piezoelectric characteristics.

The first aspect of the present invention has at least a lower electrode on the substrate, a perovskite structure represented by the general formula (K _x Na _1-x ) NbO ₃ (0 <x <1), and a film thickness of 0. A piezoelectric thin film element having a structure in which a piezoelectric thin film of 2 μm or more and 10 μm or less and an upper electrode are arranged, and the composition of K, Na, and Nb in the piezoelectric thin film is 1.15 <(K + Na) / Nb <1 .50 relationship.

The second aspect of the present invention has at least a lower electrode on the substrate, a perovskite structure represented by the general formula (K _x Na _1-x ) NbO ₃ (0 <x <1), and a film thickness of 0. A piezoelectric thin film element having a structure in which a piezoelectric thin film of 2 μm or more and 10 μm or less and an upper electrode are arranged, and the composition of K, Na, and Nb in a part of the layer of the piezoelectric thin film is 1.15 <(K + Na ) / Nb <1.50.

  According to a third aspect of the present invention, in the invention described in the first aspect, the composition of K, Na and Nb in the piezoelectric thin film is gradually within a range of 1.15 <(K + Na) / Nb <1.50. It is characterized by being a graded layer changed to.

  According to a fourth aspect of the present invention, in the invention according to the second aspect, the composition of K, Na, and Nb in the partial layer of the piezoelectric thin film is 1.15 <(K + Na) / Nb <1.50. It is characterized by being a graded layer that is gradually changed within the range.

  According to the present invention, a piezoelectric thin film element using a potassium sodium niobate thin film having excellent piezoelectric characteristics can be obtained.

The inventors changed the piezoelectric characteristics of potassium sodium niobate by changing the composition ratio (K + Na) / Nb, and set the composition ratio (K + Na) / Nb in a certain range instead of the value of x. It was found that a piezoelectric thin film element having excellent piezoelectric characteristics was obtained.
Based on this knowledge, the best mode for carrying out the present invention will be described below. However, this embodiment is shown as an example, and various modifications can be made without departing from the technical idea of the present invention. It is.

[Structure of piezoelectric thin film element]
As shown in FIG. 1, the piezoelectric thin film element 8 in this embodiment is formed of a substrate 1, a lower electrode 2, a piezoelectric thin film 3, and an upper electrode 4.

[Substrate and electrode material]
The substrate 1 is required to have heat resistance that can withstand the temperature at the time of film formation of potassium sodium niobate, and it is also an industrially important factor that it is inexpensive. The most suitable substrate 1 is preferably a Si substrate, but other substrates can be used technically. Moreover, the electrode material which comprises the upper electrode 4 and the lower electrode 2 needs to have heat resistance similarly, Although it is preferable to use platinum etc., it is not limited to this.

[Piezoelectric thin film]
The piezoelectric thin film 3 is a potassium sodium niobate thin film having a perovskite structure represented by a general formula (K _x Na _1-x ) NbO ₃ (0 <x <1).
When the potassium sodium niobate thin film crystal is an ideal cubic crystal, the composition ratio of (K + Na) / Nb is 1.0. However, in this embodiment, the composition ratio of (K + Na) / Nb of the piezoelectric thin film 3 is in the range of 1.15 <(K + Na) / Nb <1.50. The piezoelectric thin film 3 is formed as a single layer, and the composition ratio is uniform so as to fall within the above range.
Regarding the lower limit of the composition ratio, a sufficiently large piezoelectric constant is obtained when the composition ratio exceeds 1.15 from the relationship between the piezoelectric constant and the composition ratio described later (FIG. 7), and conversely, the composition ratio is less than 1.15. A large piezoelectric constant cannot be obtained.
Regarding the upper limit of the composition ratio, if the composition ratio exceeds 1.50, the perovskite structure collapses and causes deterioration of the piezoelectric characteristics. Conversely, if the composition ratio is less than 1.50, the perovskite structure does not collapse and the piezoelectric characteristics deteriorate. Does not occur.
Therefore, the composition ratio is preferably 1.15 to 1.50. If the composition ratio is within this range, a sufficiently large piezoelectric constant can be obtained, and deterioration of piezoelectric characteristics does not occur.
The film thickness of the piezoelectric thin film 3 is 0.2 μm or more and 10 μm or less. When the film thickness is 0.2 μm or more, effective piezoelectric characteristics as the piezoelectric thin film element 8 can be obtained, and when it is desired to produce the piezoelectric thin film 3 having a film thickness of 10 μm or more, a sintered body is used as in the prior art. May be used.
In addition, when a small amount of additive (for example, Li having an atomic number concentration of 8% or less) is mixed into the potassium sodium niobate thin film, an effect of improving the piezoelectric characteristics can be expected.
Further, when the piezoelectric thin film 3 has a multilayer structure or a gradient composition structure, the same effect can be expected when 5% or more of the total film thickness of the piezoelectric thin film 3 is a thin film having the above composition ratio. Further, it is desirable that 20% or more of the film thickness is a thin film having the above composition ratio.

[Method of manufacturing piezoelectric thin film element]
As shown in FIG. 1, a platinum lower electrode 2 is formed on a substrate 1 by sputtering, for example. The potassium sodium niobate thin film 3 is formed on the lower electrode 2. Examples of the film forming method include a sputtering method, a CVD method, a PLD method, and a sol-gel method. In the case of forming a film by sputtering, in order to make the composition ratio of (K + Na) / Nb 1.15 or more, the composition of the target potassium sodium niobate sintered body has a low Nb content (for example, (K + Na ) / Nb> 1)) or by adjusting the water cooling of the target to increase the target surface temperature during film formation. Thereafter, the platinum upper electrode 4 is formed in the same manner as the platinum lower electrode 2. Thus, the piezoelectric thin film element 8 is manufactured.

[Effects of Embodiment by Piezoelectric Thin Film Element]
According to the piezoelectric thin film element of the present embodiment, the following effects can be obtained.
Since the composition of K, Na, and Nb in the piezoelectric thin film has a relationship of 1.15 <(K + Na) / Nb <1.50, a sufficiently large piezoelectric constant can be obtained without causing deterioration of piezoelectric characteristics. As a result, excellent piezoelectric characteristics comparable to a sintered body can be realized. Further, since the piezoelectric thin film element does not contain lead at all, it can easily cope with lead-free environmental problems.
Furthermore, since the thickness of the piezoelectric thin film is 0.2 μm or more and 10 μm or less, it is possible to sufficiently meet the demand for miniaturization of the piezoelectric thin film element. For example, it can be used for small electronic components such as inkjet printers, scanners, gyros, ultrasonic generators, ultrasonic sensors, pressure sensors, speed sensors, and acceleration sensors.

The embodiment of the present invention has been described above. However, the present invention is not limited to the embodiment described above.
For example, in the embodiment, the piezoelectric thin film is formed as a single layer and the composition ratio is uniform so as to be within the above range. However, the piezoelectric thin film is formed of two or more layers, and at least one layer (some layers) ) May be uniform so as to fall within the above range. Further, the piezoelectric thin film may be an inclined layer whose composition ratio gradually changes, and the composition ratio may be changed so as to fall within the above range. In these cases, the film thickness in a part of the layers having the composition ratio is preferably 5% or more of the total film thickness of the piezoelectric thin film, and more preferably 20% or more (FIG. 9).
In the embodiment, K and Na are mixed in the metal R, but a small amount of additive, for example, Li having an atomic concentration of 8% or less may be mixed in the metal R. The effect of improving the piezoelectric characteristics can be expected as in the embodiment.

Preferred embodiments of the present invention will be additionally described.
According to the first aspect, the substrate has at least a lower electrode, a perovskite structure represented by the general formula (K _x Na _1-x ) NbO ₃ (0 <x <1), and a film thickness of 0.2 μm. A piezoelectric thin film element having a structure in which a piezoelectric thin film having a thickness of 10 μm or less and an upper electrode is provided, and the composition of K, Na, and Nb in the piezoelectric thin film is 1.15 <(K + Na) / Nb <1. A piezoelectric thin film element having 50 relationships is provided.

According to a second aspect, at least a lower electrode having a perovskite structure represented by the general formula _{(K x Na 1-x)} NbO 3 (0 <x <1), thickness of 0.2μm on the substrate A piezoelectric thin film element having a structure in which a piezoelectric thin film of 10 μm or less and an upper electrode are arranged, and the composition of K, Na, and Nb in a part of the piezoelectric thin film is 1.15 <(K + Na) A piezoelectric thin film element having a relationship of /Nb<1.50 is provided.

  According to a third aspect, in the invention according to the first aspect, the composition of K, Na and Nb in the piezoelectric thin film is gradually reduced within a range of 1.15 <(K + Na) / Nb <1.50. A piezoelectric thin film element that is a changed graded layer is provided.

  According to a fourth aspect, in the invention according to the second aspect, the composition of K, Na, and Nb in the partial layer of the piezoelectric thin film satisfies 1.15 <(K + Na) / Nb <1.50. A piezoelectric thin film element is provided that is a graded layer that is gradually changed within a range.

According to the fifth aspect, the step of forming the lower electrode on the substrate, and the perovskite structure represented by the general formula (K _x Na _1-x ) NbO ₃ (0 <x <1) on the lower electrode Crystal growth of a piezoelectric thin film having a step of forming an upper electrode on the piezoelectric thin film,
In the crystal growth step, the film thickness is 0.2 μm or more and 10 μm or less, and the composition of K, Na, and Nb is 1 by sputtering using a (K _x Na _1-x ) NbO ₃ sintered body as a target. A method of manufacturing a piezoelectric thin film element is provided, in which a piezoelectric thin film having a relationship of .15 <(K + Na) / Nb <1.50 is grown.

According to the sixth aspect, the step of forming the lower electrode on the substrate, and the perovskite structure represented by the general formula (K _x Na _1-x ) NbO ₃ (0 <x <1) on the lower electrode And growing a piezoelectric thin film having a film thickness of 0.2 μm or more and 10 μm or less by a sputtering method using a (K _x Na _1-x ) NbO ₃ sintered body as a target, and on the piezoelectric thin film Forming an upper electrode on
In the crystal growth step, a piezoelectric thin film in which a piezoelectric thin film in which a composition of K, Na, and Nb has a relationship of 1.15 <(K + Na) / Nb <1.50 is grown on a part of the piezoelectric thin film. An element manufacturing method is provided.

  This will be described below with reference to examples. The composition of the piezoelectric thin film is defined by the composition ratio calculated from the composition of K, Na, and Nb measured by AES (Auger electron spectroscopy measurement) or XPS (X-ray photoelectron spectroscopy measurement).

[Example 1, comparative example]
(Preparation of piezoelectric thin film)
In Example 1, a (K _0.5 Na _0.5 ) NbO ₃ piezoelectric thin film was produced. The produced piezoelectric thin film body is shown in FIG.
As the substrate 1, a Si substrate ((001) plane orientation, thickness 0.5 mm) was used.
A platinum lower electrode 2 ((111) plane single orientation, film thickness 0.2 μm) was formed on the Si substrate 1 by RF magnetron sputtering. The platinum lower electrode 2 was formed under the conditions of a substrate temperature of 600 ° C., a discharge power of 200 W, an introduced gas in an Ar atmosphere, a pressure of 2.5 Pa, and a film formation time of 10 minutes.
A (K _0.5 Na _0.5 ) NbO ₃ piezoelectric thin film 5 (thickness: 3.0 μm) was formed thereon by RF magnetron sputtering. _(K 0.5 _Na 0.5) NbO ₃ piezoelectric thin film 5, a sputtering target (K + Na) / composition ratio of Nb is 1.2 and K / (K + Na) composition ratio of 0.5 in _(K x Na _{A 1-x} ) NbO ₃ sintered body was used, and the film was formed under the conditions of a substrate temperature of 570 ° C., a discharge power of 100 W, an introduced gas in an Ar atmosphere, a pressure of 0.4 Pa, and a film formation time of 4 hours.
Thus, the (K _0.5 Na _0.5 ) NbO ₃ piezoelectric thin film body 9 in Example 1 was produced.
In addition, with respect to the piezoelectric thin film body of the comparative example, Example 1 was used except that a (K _x Na _1-x ) NbO ₃ sintered body having a (K + Na) / Nb composition ratio of 1.0 was used as the sputtering target. It produced similarly.

(Composition distribution measurement)
The elemental composition distribution in the depth direction of the piezoelectric thin film body 9 of Example 1 and Comparative Example was measured by AES (Auger Electron Spectroscopy), and the results are shown in FIGS. 3 and 4, respectively. According to FIG. 3, the atomic concentration of Nb in Example 1 is 17.5 (atomic%, hereinafter referred to as at%), the atomic concentration of K is 11.5 (at%), and the atomic concentration of Na is 10.0 ( at%). As a result, in the piezoelectric thin film 5 of Example 1, the composition ratio of (K + Na) / Nb was about 1.37, which was in the range of 1.15 to 1.50.
According to FIG. 4, in the piezoelectric thin film 5 of the comparative example, the atomic concentration of Nb is 19.5 (at%), the atomic concentration of K is 10.8 (at%), and the atomic concentration of Na is 9.3 (at %)Met. As a result, in the piezoelectric thin film 5 of the comparative example, the composition ratio of (K + Na) / Nb was about 1.03, which was outside the range of 1.15 to 1.50.

(Piezoelectric property evaluation measurement)
In order to perform the piezoelectric characteristic evaluation measurement, the platinum upper electrode 4 (film thickness: 0.02 μm) was formed on the piezoelectric thin film 5 by the RF magnetron sputtering method, and the piezoelectric thin film element 8 shown in FIG. 1 was obtained.
FIG. 5A is a diagram showing an outline of a unimorph cantilever 15 for performing piezoelectric characteristic evaluation measurement. As shown in FIG. 5 (a), a strip sample having a length of 20 mm × width of 2.5 mm is cut out from the piezoelectric thin film element 8, and a longitudinal end thereof is clamped by a clamp 20 installed on a vibration isolation table 22. A simple unimorph cantilever 15 was constructed. The effect of the vibration on the unimorph cantilever 15 can be removed by the vibration isolation table 22.
By applying a voltage to the (K _0.5 Na _0.5 ) NbO ₃ thin film 13 between the platinum upper and lower electrodes 12 and 14 formed on the Si substrate 11 and expanding and contracting the thin film 13, FIG. ), The entire unimorph cantilever 15 was bent, and the tip of the unimorph cantilever 15 was moved. The tip maximum displacement 30 (Δt) was measured with a laser Doppler displacement meter 21. The relationship between the applied voltage and the maximum tip displacement (hereinafter referred to as piezoelectric displacement) in Example 1 and the comparative example obtained as a result is shown in FIG. From FIG. 6, it was found that the amount of displacement of the tip of the unimorph cantilever due to the piezoelectric was about three times that of the piezoelectric thin film element of Example 1 as compared with the piezoelectric thin film element of the comparative example.

(Piezoelectric constant)
From the relationship between the dimensions and the applied voltage and the amount of piezoelectric displacement of the sample, the result of calculation of the piezoelectric constant d _31, the piezoelectric constant d ₃₁ of the piezoelectric thin film device produced by this example was 92 (-pm / V) . On the other hand, the piezoelectric constant d ₃₁ of the piezoelectric thin film element produced by the comparative example was 30 (−pm / V).
From this, it was confirmed that by using the present invention, the (K _x Na _1-x ) NbO ₃ piezoelectric thin film 5 having better piezoelectric characteristics than the prior art can be produced.
Further, (K _x Na _1-x ) NbO ₃ piezoelectric thin films having different composition ratios of (K + Na) / Nb were formed, and the respective piezoelectric constants d ₃₁ were calculated by the same method as described above. The relationship between the piezoelectric constant and the composition ratio is shown in FIG. As shown in FIG. 7, when the composition ratio of (K + Na) / Nb is less than 1.15, the piezoelectric constant d ₃₁ is 40 (−pm / V) or less, but the composition ratio of (K + Na) / Nb is 1.15. It has been found that the value of the piezoelectric constant d ₃₁ increases rapidly as the value increases.

[Example 2, comparative example]
(Production of piezoelectric thin film element)
The (K _0.5 Na _0.5 ) NbO ₃ piezoelectric thin film of Example 2 is different from Example 1 in that the (K _0.5 Na _0.5 ) NbO ₃ piezoelectric thin film is formed not by a single layer but by two layers. This is the point. The piezoelectric thin film body 10 produced in Example 2 is shown in FIG.
As the first piezoelectric thin film 6, a (K _x Na _1-x ) NbO ₃ sintered body having a composition ratio (K + Na) /Nb=1.2 and K / (K + Na) = 0.5 was used as a target. A (K _x Na _1-x ) NbO ₃ thin film having a composition of (K + Na) richer than Nb was formed under the condition of a film time of 50 minutes.
As a second layer of the piezoelectric thin film 7, using the composition ratio (K + Na) /Nb=1.0,K/ (K + Na) = 0.5 in _{(K x Na 1-x)} NbO 3 sintered body target, formed A (K _x Na _1-x ) NbO ₃ thin film having the same composition ratio of (K + Na) and Nb was formed under the condition of a film time of 3 hours and 10 minutes.
As a result, the total thickness of the two piezoelectric thin films 6 and 7 was set to 3.0 μm.
From the relationship of the deposition time of the upper and lower thin films, the proportion of the first thin film is 21% of the entire (K _0.5 Na _0.5 ) NbO ₃ piezoelectric thin film, as viewed from the thickness of the entire thin film. The proportion of the thin film was 79%.

(Composition distribution measurement)
In the same manner as in Example 1, the elemental composition distribution in the depth direction of the piezoelectric thin film in Example 2 was measured. The results are shown in FIG. According to FIG. 9, in the piezoelectric thin film body 10 of Example 2, the Nb atomic concentration is 17 in the first thin film 6 among the two-layered (K _0.5 Na _0.5 ) NbO ₃ thin films. 0.5 (at%), the atomic concentration of K was 11.5 (at%), and the atomic concentration of Na was 10.0 (at%). Therefore, the composition ratio of (K + Na) / Nb was about 1.37, which was in the range of 1.15 to 1.50.
In the second thin film 7, the Nb atomic concentration was 19.5 (at%), the K atomic concentration was 11.0 (at%), and the Na atomic concentration was 9.0 (at%). Therefore, the composition ratio of (K + Na) / Nb was about 1.03, which was outside the range of 1.15 to 1.50.

(Piezoelectric property evaluation measurement)
Similarly to Example 1, a platinum upper electrode was prepared, and piezoelectric property evaluation measurement was performed in Example 2 and Comparative Example. The relationship between the applied voltage and the maximum tip displacement obtained as a result is shown in FIG.
From FIG. 10, the amount of displacement of the tip of the unimorph cantilever due to the piezoelectric was larger in the piezoelectric thin film element using the present invention than in the piezoelectric thin film element fabricated using the conventional technique.

(Piezoelectric constant)
As in Example 1, the piezoelectric constant d ₃₁ was calculated. As a result, the piezoelectric constant d ₃₁ of the piezoelectric thin film element of Example 2 was 64 (−pm / V).
This confirms that even if the piezoelectric thin film using the present invention occupies only 21% of the entire piezoelectric thin film, it is possible to produce a (K _x Na _1-x ) NbO ₃ piezoelectric thin film having better piezoelectric characteristics than the prior art. did it.

Is a cross-sectional view of a _{(K x Na 1-x)} NbO 3 piezoelectric thin film element according to an embodiment of the present invention. It is a cross-sectional view of the Example 1 and Comparative Example _{(K 0.5} Na 0.5) NbO ₃ piezoelectric thin films. 2 is an element composition distribution diagram in the depth direction of a (K _0.5 Na _0.5 ) NbO ₃ piezoelectric thin film in Example 1. FIG. Comparison is _{(K 0.5} Na 0.5) NbO ₃ elemental composition distribution diagram of the depth direction of the piezoelectric thin film in the example. It is explanatory drawing which shows the method of a piezoelectric characteristic evaluation measurement. It is the figure which showed the relationship between the applied voltage and the tip maximum displacement amount in Example 1 and a comparative example. And _{(K x Na 1-x)} NbO 3 piezoelectric thin film of the piezoelectric constant _{d 31,} is a diagram showing the relationship between the composition ratio of Nb and (K + Na). 6 is a cross-sectional view of a (K _0.5 Na _0.5 ) NbO ₃ piezoelectric thin film body in Example 2. FIG. 6 is an elemental composition distribution diagram in the depth direction of a (K _0.5 Na _0.5 ) NbO ₃ piezoelectric thin film in Example 2. FIG. It is the figure which showed the relationship between the applied voltage and the tip maximum displacement amount in Example 1 and a comparative example.

Explanation of symbols

1 substrate 2 lower electrode _{3 (K x Na 1-x} ) NbO 3 piezoelectric thin film 4 upper electrode _{5 (K 0.5 Na 0.5) NbO} 3 piezoelectric thin film 6 first layer of the piezoelectric thin film 7 second layer of the piezoelectric thin film 8 Piezoelectric thin film element 9 Piezoelectric thin film body 10 Piezoelectric thin film body 11 Si substrate 12 Platinum lower electrode 13 (K _0.5 Na _0.5 ) NbO ₃ Piezoelectric thin film 14 Platinum upper electrode 15 Unimorph cantilever 20 Clamp 21 Laser Doppler displacement meter 22 Removal Shake base 30 Maximum tip displacement

Claims (4)

A piezoelectric thin film having at least a lower electrode, a perovskite structure represented by the general formula (K _x Na _1-x ) NbO ₃ (0 <x <1), and a film thickness of 0.2 μm or more and 10 μm or less And a piezoelectric thin film element having a structure in which an upper electrode is disposed,
The piezoelectric thin film element, wherein the composition of K, Na, and Nb in the piezoelectric thin film has a relationship of 1.15 <(K + Na) / Nb <1.50. A piezoelectric thin film having at least a lower electrode, a perovskite structure represented by the general formula (K _x Na _1-x ) NbO ₃ (0 <x <1), and a film thickness of 0.2 μm or more and 10 μm or less And a piezoelectric thin film element having a structure in which an upper electrode is disposed,
A piezoelectric thin film element, wherein the composition of K, Na, and Nb in a part of the piezoelectric thin film has a relationship of 1.15 <(K + Na) / Nb <1.50.   The composition of K, Na, and Nb in the piezoelectric thin film is a graded layer that is gradually changed within a range of 1.15 <(K + Na) / Nb <1.50. Piezoelectric thin film element. The composition of K, Na, and Nb in a part of the piezoelectric thin film is a graded layer that is gradually changed within a range of 1.15 <(K + Na) / Nb <1.50. Item 3. The piezoelectric thin film element according to Item 2.

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