Piezoelectric thin film element and piezoelectric transducer

Abstract

The piezoelectric thin film element includes an electrode layer (a first electrode layer) and a piezoelectric thin film directly or indirectly overlapping the electrode layer. The piezoelectric thin film includes a perovskite-type oxide tetragonal 1 and a perovskite-type oxide tetragonal 2. A (001) plane of the tetragonal 1 is oriented in a normal direction D of a surface of the electrode layer N The (001) plane of the tetragonal 2 is inclined with respect to the (001) plane of the tetragonal 1. A spacing of the (001) plane of the tetragonal 1 is c1. A spacing of the (100) plane of the tetragonal 1 is a1. A spacing of the (001) plane of the tetragonal 2 is c2. A spacing of the (100) plane of the tetragonal 2 is a2. c1 / a1 is larger than c2 / a2.

Description

Technical Field

[0001] This disclosure relates to piezoelectric thin film elements and piezoelectric transducers. Background Technology

[0002] Piezoelectric materials are processed into a variety of piezoelectric elements for various purposes. For example, piezoelectric actuators convert voltage into force through the inverse piezoelectric effect, which causes deformation of the piezoelectric material by applying voltage. Additionally, piezoelectric sensors convert force into voltage by generating a polarized piezoelectric effect through deformation of the piezoelectric material by applying pressure. These piezoelectric elements are incorporated into a wide variety of electronic devices.

[0003] In recent years, the market has demanded miniaturization and improved performance of electronic devices. Therefore, research has been actively conducted on piezoelectric elements (piezoelectric thin film elements) that utilize piezoelectric thin films. However, the thinner the piezoelectric material, the more difficult it is to obtain the piezoelectric effect and the inverse piezoelectric effect. Therefore, the development of piezoelectric materials with excellent piezoelectric properties in the thin film state is anticipated.

[0004] Currently, lead zirconate titanate (PZT), a perovskite-type ferroelectric material, is widely used as a piezoelectric material. However, PZT contains lead (Pb), which is harmful to human health and the environment. Therefore, the development of lead-free piezoelectric materials as an alternative to PZT is anticipated. For example, BiFeO3 is described as an example of a lead-free piezoelectric material in the following non-patent literature. BiFeO3 also exhibits relatively excellent piezoelectric properties among lead-free piezoelectric materials, and its application in piezoelectric thin film elements is particularly anticipated.

[0005] <Non-patent literature> Y.Kawahara et al, Control of Crystal Structure of BiFeO3Epitaxial Thin Films by Adjusting Growth Conditions and PiezoelectricProperties, Japanese Journal of Applied Physics.51(2012)09LB04 Summary of the Invention

[0006] The main indicator representing the performance of a piezoelectric material (piezoelectric constant) is d. 33，f (piezoelectric strain constant), and g 33 (Piezoelectric output constant). Piezoelectric strain constant d 33，f (Unit: pC / N) is an indicator of the amount of deformation (transmitted energy) per unit electric field. The piezoelectric strain constant d 33，fThe larger the value, the better the performance of the piezoelectric element as an actuator. On the other hand, the piezoelectric output constant g... 33 (unit × 10) －3 V·m / N) is an indicator of the generated electric field strength (received energy) per unit stress. The piezoelectric output constant g 33 The larger the value, the better the performance of the piezoelectric element used as a transducer or other sensor. 33 Represented as d 33，f / ε r ε0 or d 33，f / ε 33 ε0. ε r or ε 33 ε0 is the relative permittivity of the piezoelectric material (unit: none). ε0 is the permittivity of vacuum (8.854 × 102). －12 Fm －1 ). d 33，f / ε r ε0 is recorded as the "piezoelectric performance index". With d 33，f As ε increases, the piezoelectric performance index increases, and with ε r As the piezoelectric strain constant d decreases, the piezoelectric property index increases. That is, through a larger piezoelectric strain constant d... 33，f and low relative permittivity ε r The balance between piezoelectric performance index (d) 33，f / ε r ε0) increases.

[0007] One objective of this invention is to provide a piezoelectric performance index (d) that is large. 33，f / ε r A piezoelectric thin film element (ε0) and a piezoelectric transducer comprising the piezoelectric thin film element.

[0008] One aspect of the present invention provides a piezoelectric thin film element comprising an electrode layer and a piezoelectric thin film directly or indirectly superimposed on the electrode layer. The piezoelectric thin film comprises a tetragonal 1 of a perovskite oxide and a tetragonal 2 of a perovskite oxide. The (001) facet of the tetragonal 1 is oriented in the normal direction to the surface of the electrode layer. The (001) facet of the tetragonal 2 is inclined relative to the (001) facet of the tetragonal 1. The spacing between the (001) facets of the tetragonal 1 is c1. The spacing between the (100) facets of the tetragonal 1 is a1. The spacing between the (001) facets of the tetragonal 2 is c2. The spacing between the (100) facets of the tetragonal 2 is a2. c1 / a1 is larger than c2 / a2.

[0009] The absolute value of the angle between the (001) plane of tetragonal crystal 1 and the (001) plane of tetragonal crystal 2 is θ. 12 θ 12 It can also be between 1.0° and 10.0°.

[0010] c1 / a1 can also be above 1.120 or below 1.270.

[0011] c2 / a2 can also be above 1.010 or below 1.115.

[0012] The peak intensity of the X-ray diffracted from the (001) plane of tetragonal crystal 1 is I1. The peak intensity of the X-ray diffracted from the (001) plane of tetragonal crystal 2 is I2. 100×I2 / (I1+I2) can also be above 0.30 and below 10.0.

[0013] The tetragonal crystal 1 can also contain bismuth, iron, and element E. B And oxygen. Element E B It can also be at least one element selected from the group consisting of magnesium, aluminum, zirconium, titanium, nickel and zinc.

[0014] The tetragonal crystal 1 can also be represented by the following chemical formula 1. In the following chemical formula 1, E... A It can also be at least one element selected from the group consisting of Na, K, Ag, and Ba. E in the following chemical formula 1... B1 It can also be at least one element selected from the group consisting of Mg, Al, Zr, Ti, Ni, and Zn. E in the following chemical formula 1... B2 It can also be at least one element selected from the group consisting of Mg, Al, Zr, Ti, Ni, and Zn. E in the following chemical formula 1... B1 and E B2 They are all different. In the following chemical formula 1, x1 can be 0.05 or more and 0.90 or less. In the following chemical formula 1, y1 can be 0.10 or more and 0.95 or less. x1+y1 can also be 1.00. In the following chemical formula 1, α can be 0.00 or more and 1.00 or less. In the following chemical formula 1, β can be 0.00 or more and 1.00 or less.

[0015] x1(Bi 1－α E A α (E) B1 1－β E B2 β )O3-y1BiFeO3 (1)

[0016] The tetragonal crystal 2 can also contain bismuth, iron, and element E. B And oxygen. Element E B It can also be at least one element selected from the group consisting of magnesium, aluminum, zirconium, titanium, nickel and zinc.

[0017] The tetragonal crystal 2 can also be represented by the following chemical formula 2. In the following chemical formula 2, E... AIt can also be at least one element chosen from the group consisting of Na, K, Ag, and Ba. E in the following chemical formula 2... B1 It can also be at least one element selected from the group consisting of Mg, Al, Zr, Ti, Ni, and Zn. E in the following chemical formula 2... B2 It can also be at least one element selected from the group consisting of Mg, Al, Zr, Ti, Ni, and Zn. E in the following chemical formula 2... B1 and E B2 They are all different. In the following chemical formula 2, x² can be 0.05 or more and 0.90 or less. In the following chemical formula 2, y² can be 0.10 or more and 0.95 or less. x² + y² can also be 1.00. In the following chemical formula 2, α can be 0.00 or more and 1.00 or less. In the following chemical formula 2, β can be 0.00 or more and 1.00 or less.

[0018] x2(Bi 1－α E A α (E) B1 1－β E B2 β )O3-y2BiFeO3 (2)

[0019] A piezoelectric thin-film element according to one aspect of the present invention may further include a crystalline substrate and a first intermediate layer. The first intermediate layer may also be disposed between the crystalline substrate and the electrode layer. The first intermediate layer may also include ZrO2 and Y2O3.

[0020] The piezoelectric thin film element of one aspect of the present invention may further include a second intermediate layer. The second intermediate layer may also be disposed between the electrode layer and the piezoelectric thin film. The second intermediate layer may also include at least one compound selected from the group consisting of BaTiO3, SrRuO3 and LaNiO3.

[0021] The electrode layer may also contain platinum crystals. The (002) plane of the platinum crystals may also be oriented in the normal direction to the surface of the electrode layer. The (200) plane of the platinum crystals may also be oriented in the in-plane direction to the surface of the electrode layer.

[0022] One aspect of the present invention provides a piezoelectric transducer comprising the piezoelectric thin film element.

[0023] According to one aspect of the invention, a piezoelectric performance index (d) can be provided. 33，f / ε r A piezoelectric thin film element (ε0) and a piezoelectric transducer comprising the piezoelectric thin film element. Attached Figure Description

[0024] Figure 1AThis is a schematic cross-sectional view of a piezoelectric thin film element according to an embodiment of the present invention. Figure 1B yes Figure 1A An exploded three-dimensional view of the piezoelectric thin film element shown.

[0025] Figure 2 It is a three-dimensional diagram of the unit cell of a perovskite structure (perovskite oxide).

[0026] Figure 3A This is a schematic three-dimensional diagram of the unit cell of tetragonal crystal 1. Figure 3B This is a schematic three-dimensional diagram of the unit cell of a tetragonal crystal 2.

[0027] Figure 4 This is a schematic diagram showing the (001) facet of the square crystal 1 and the (001) facet of the square crystal 2 in the piezoelectric thin film.

[0028] Figure 5 This is a schematic cross-sectional view of a piezoelectric thin film element (ultrasonic transducer) according to another embodiment of the present invention.

[0029] Figure 6A and Figure 6B This is a reciprocal space map of the diffracted X-rays of the piezoelectric thin film contained in the piezoelectric thin film element of Embodiment 1 of the present invention. Detailed Implementation

[0030] Hereinafter, details of a preferred embodiment of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the following embodiment. In the drawings, the same or equivalent elements are labeled with the same symbols. Figure 1A , Figure 1B and Figure 5 The X, Y, and Z axes shown are three mutually orthogonal coordinate axes. The directions of each of the three coordinate axes are... Figure 1A , Figure 1B and Figure 5 The CCP.

[0031] The piezoelectric thin film element of this embodiment includes an electrode layer and a piezoelectric thin film directly or indirectly superimposed on the electrode layer. Figure 1A This is a cross-sectional view of the piezoelectric thin film element 10 of this embodiment. Figure 1AThe cross-section shown is perpendicular to the surfaces of the first electrode layer 7 and the piezoelectric thin film 3, respectively. The piezoelectric thin film element 10 includes: a crystalline substrate 8, a first electrode layer 7 (lower electrode layer) directly or indirectly superimposed on the crystalline substrate 8, a piezoelectric thin film 3 directly or indirectly superimposed on the first electrode layer 7, and a second electrode layer 4 (upper electrode layer) directly or indirectly superimposed on the piezoelectric thin film 3. The piezoelectric thin film element 10 may also include a first intermediate layer 5. The first intermediate layer 5 may also be disposed between the crystalline substrate 8 and the first electrode layer 7, and the first electrode layer 7 may also be directly superimposed on the surface of the first intermediate layer 5. The piezoelectric thin film element 10 may also include a second intermediate layer 6. The second intermediate layer 6 may also be disposed between the first electrode layer 7 and the piezoelectric thin film 3, and the piezoelectric thin film 3 may also be directly superimposed on the surface of the second intermediate layer 6.

[0032] Figure 1B This is an exploded perspective view of the piezoelectric thin film element 10. Figure 1B In the exploded perspective view shown, the crystalline substrate 8, the first intermediate layer 5, the second intermediate layer 6, and the second electrode layer 4 are omitted. The normal direction D of the surface of the first electrode layer 7 is shown. N It can also be approximately parallel (Z-axis direction) to the directions of the stacked crystalline substrate 8, first intermediate layer 5, first electrode layer 7, second intermediate layer 6, piezoelectric thin film 3, and second electrode layer 4. The normal direction D of the surface of the first electrode layer 7... N This can also be referred to as the thickness direction of the first electrode layer 7. The normal direction dn of the surface of the piezoelectric film 3 can also be the same as the normal direction D of the surface of the first electrode layer 7. N The surfaces are approximately parallel. That is, the surface of the piezoelectric thin film 3 can also be approximately parallel to the surface of the first electrode layer 7. The normal direction dn of the surface of the piezoelectric thin film 3 can also be referred to as the thickness direction of the piezoelectric thin film 3. The thicknesses of the crystalline substrate 8, the first intermediate layer 5, the first electrode layer 7, the second intermediate layer 6, the piezoelectric thin film 3, and the second electrode layer 4 can also be uniform.

[0033] A variation of the piezoelectric thin film element 10 may also omit the crystalline substrate 8. For example, the crystalline substrate 8 may be removed after the first electrode layer 7 and the piezoelectric thin film 3 are formed. A variation of the piezoelectric thin film element 10 may also omit the second electrode layer 4. For example, after the piezoelectric thin film element without the second electrode layer is supplied as a product to an electronic device manufacturer, the second electrode layer may be added to the piezoelectric thin film element during the manufacturing process of the electronic device. When the crystalline substrate 8 functions as an electrode layer (first electrode layer 7), a variation of the piezoelectric thin film element 10 may omit the first electrode layer 7. That is, a variation of the piezoelectric thin film element 10 may also include a crystalline substrate 8 having the function (conductivity) of an electrode layer, and a piezoelectric thin film 3 directly or indirectly superimposed on the crystalline substrate 8. When a variation of the piezoelectric thin film element 10 omits the first electrode layer 7 but includes a crystalline substrate 8 functioning as an electrode layer, at least one of the first intermediate layer 5 and the second intermediate layer 6 may be disposed between the piezoelectric thin film 3 and the crystalline substrate 8. In a modified example of the piezoelectric thin film element 10, the first electrode layer 7 is omitted, but a crystalline substrate 8 that functions as an electrode layer is included. The normal direction D of the surface of the first electrode layer 7... N It can also be referred to as the normal direction of the surface of the crystalline substrate 8.

[0034] The piezoelectric thin film 3 comprises tetragonal crystals 1 and 2 of perovskite oxide. Of course, the perovskite oxide is an oxide having a perovskite structure. The piezoelectric thin film 3 may also comprise more than one tetragonal crystal 1 and more than one tetragonal crystal 2. The piezoelectric thin film 3 may also be composed solely of more than one tetragonal crystal 1 and more than one tetragonal crystal 2. More than one tetragonal crystal 1 and more than one tetragonal crystal 2 may also coexist mixed in the piezoelectric thin film 3. The piezoelectric thin film 3 may also comprise more than one first domain composed of more than one tetragonal crystal 1. The piezoelectric thin film 3 may also comprise more than one second domain composed of more than one tetragonal crystal 2. For example, more than one first domain and more than one second domain may also be arranged (alternating) along the surface of the first electrode layer 7. More than one first domain and more than one second domain may also be arranged along the normal direction D of the surface of the first electrode layer 7. N (Alternating) arrangement. Each first domain can also be the normal direction D along the surface of the first electrode layer 7. N Extended columnar crystals. Each second domain can also be along the normal direction D of the surface of the first electrode layer 7. N Extended columnar crystals. The total content of elements constituting tetragonal crystal 1 and tetragonal crystal 2 in the piezoelectric film can also be more than 99% mol% and less than 100 mol%.

[0035] The tetragonal crystal 1 can also contain bismuth (Bi), iron (Fe), and element E. B And oxygen (O). Element EB It can also be at least one element selected from the group consisting of magnesium (Mg), aluminum (Al), zirconium (Zr), titanium (Ti), nickel (Ni), and zinc (Zn). The tetragonal crystal 1 can also contain multiple elements, such as E. B For example, a tetragonal crystal 1 can also contain E. B1 and E B2 As element E B The tetragonal crystal 1 may also contain Bi, Fe, and E in addition to these elements. B In addition to O, it also includes element E. A . Element E A It can also be at least one element selected from the group consisting of sodium (Na), potassium (K), silver (Ag), and barium (Ba). The tetragonal crystal 1 can also contain multiple E elements. A .

[0036] The tetragonal crystal 2 can also contain bismuth, iron, and element E. B And oxygen. The element E contained in tetragonal crystal 2. B It can also be at least one element selected from the group consisting of magnesium, aluminum, zirconium, titanium, nickel, and zinc. The tetragonal crystal 2 can also contain multiple elements, including E. B For example, tetragonal crystal 2 can also contain E. B1 and E B2 As element E B The tetragonal crystal 2 may also contain Bi, Fe, and E in addition to these elements. B In addition to O, it also includes element E. A The element E contained in tetragonal crystal 2 A It can also be at least one element selected from the group consisting of sodium, potassium, silver, and barium. The tetragonal crystal 2 can also contain multiple E elements. A .

[0037] The composition of tetragonal crystal 1 can be the same as that of tetragonal crystal 2. The composition of tetragonal crystal 1 can also be different from that of tetragonal crystal 2. The individual compositions of tetragonal crystal 1 and tetragonal crystal 2 can also be approximately the same as the overall composition of the piezoelectric thin film 3. Tetragonal crystal 1 and tetragonal crystal 2 may each contain Bi, Fe, and E. A E B And elements other than O. Neither tetragonal crystal 1 nor tetragonal crystal 2 may contain Pb. Neither tetragonal crystal 1 nor tetragonal crystal 2 may contain Pb.

[0038] Figure 2 The unit cell uc represents the perovskite oxide. Figure 2 In the diagram, a, b, and c are each a fundamental vector of the perovskite structure. The element at site A in the unit cell uc can also be Bi or E. A The element located at the B site in the unit cell uc can also be Fe or E. B .

[0039] Figure 3A Let uc1 represent the unit cell of the tetragonal crystal 1. For ease of illustration, the E elements constituting the unit cell uc1 are omitted. B And O (oxygen), but Figure 3A The unit cell uc1 in the middle has the same characteristics as Figure 2 The cell uc in it has the same perovskite structure.

[0040] Figure 3A a1, b1, and c1 are each the fundamental vectors of a tetragonal crystal 1. Figure 3A Vector a1 in Figure 2 The vector 'a' in the text corresponds to this. Figure 3A Vector b1 in Figure 2 The vector b in the text corresponds to this. Figure 3A Vector c1 in Figure 2 The vector c corresponds to the vectors a1, b1, and c1. a1, b1, and c1 are perpendicular to each other. The orientation of vector a1 (a-axis) is

[100] . The orientation of vector b1 (b-axis) is

[010] . The orientation of vector c1 (c-axis) is

[001] . The length (a1) of vector a1 is the spacing between the (100) planes of the cubic crystal 1 (i.e., the lattice constant in the

[100] direction). The length (b1) of vector b1 is the spacing between the (010) planes of the cubic crystal 1 (i.e., the lattice constant in the

[010] direction). The length (c1) of vector c1 is the spacing between the (001) planes of the cubic crystal 1 (i.e., the lattice constant in the

[001] direction). Length a1 is equal to length b1. Length c1 is greater than length a1.

[0041] Figure 3B Let uc2 represent the unit cell of tetragonal crystal 2. For ease of illustration, the E that constitute the unit cell uc2 are omitted. B And O (oxygen), but Figure 3B The unit cell uc2 has the same Figure 2 The cell uc in it has the same perovskite structure.

[0042] Figure 3B a2, b2, and c2 are each the basic vectors of a tetragonal crystal 2. Figure 3B The vector a2 in Figure 2 The vector 'a' in the text corresponds to this. Figure 3B Vector b2 in Figure 2 The vector b in the text corresponds to this. Figure 3B The vector c2 in Figure 2The vector c corresponds to the vectors a2, b2, and c2. a2 (a-axis) is oriented at

[100] . b2 (b-axis) is oriented at

[010] . c2 (c-axis) is oriented at

[001] . The length (a2) of vector a2 is the spacing between the (100) planes of the cubic crystal 2 (i.e., the lattice constant in the

[100] direction). The length (b2) of vector b2 is the spacing between the (010) planes of the cubic crystal 2 (i.e., the lattice constant in the

[010] direction). The length (c2) of vector c2 is the spacing between the (001) planes of the cubic crystal 2 (i.e., the lattice constant in the

[001] direction). Length a2 is equal to length b2. Length c2 is greater than length a2.

[0043] The c1 / a1 ratio of tetragonal crystal 1 is larger than the c2 / a2 ratio of tetragonal crystal 2. That is, the anisotropy of tetragonal crystal 1 is greater than that of tetragonal crystal 2. For example... Figure 1B and Figure 3A As shown, at least part or all of the (001) plane of the tetragonal crystal 1 (cell uc1) is in the normal direction D of the surface of the first electrode layer 7. N Orientation. For example, at least some or all of the (001) planes of the cubic crystal 1 may be substantially parallel to the surface of the first electrode layer 7. At least some or all of the (001) planes of the cubic crystal 1 (cell uc1) may also be oriented in the normal direction dn of the surface of the piezoelectric thin film 3. For example, at least some or all of the (001) planes of the cubic crystal 1 may be substantially parallel to the surface of the piezoelectric thin film 3.

[0044] The tetragonal crystals of perovskite oxides tend to polarize in the

[001] direction. That is,

[001] is the orientation in which the tetragonal crystals of perovskite oxides are more likely to polarize than other crystal orientations. Therefore, the normal direction D through the (001) plane of the tetragonal crystal 1 on the surface of the first electrode layer 7... N With its upward orientation, the piezoelectric thin film 3 can exhibit excellent piezoelectricity. For the same reason, the piezoelectric thin film 3 can also be a ferroelectric material. The term "crystallization orientation" as used below refers to the direction D of the normal to the surface of the first electrode layer 7 of the (001) plane of the tetragonal crystal 1. N Upward orientation.

[0045] By possessing the aforementioned crystal orientation, the piezoelectric thin film 3 can exhibit a large piezoelectric performance index (d). 33，f / ε rε0). The aforementioned crystal orientation is an inherent characteristic of the thin film. The thin film is a crystalline film formed by methods such as vapor phase growth or solution growth. On the other hand, a bulk piezoelectric body having the same composition as the piezoelectric thin film 3 is unlikely to possess the aforementioned crystal orientation. This is because the bulk piezoelectric body is a sintered body (ceramic) containing powder of the essential elements of the piezoelectric body, making it difficult to control the structure and orientation of the large amount of crystals constituting the sintered body.

[0046] Figure 4 This indicates the orientation direction of the (001) facet of the tetragonal crystal 1 and the orientation direction of the (001) facet of the tetragonal crystal 2 in the piezoelectric thin film 3. However, the respective arrangements of the tetragonal crystal 1 and the tetragonal crystal 2 in the piezoelectric thin film 3 are not limited to... Figure 4 The configuration shown. Figure 4 In this context, (001)-T1 refers to the (001) plane of the tetragonal crystal 1. Figure 4 In this context, (001)-T2 refers to the (001) plane of the tetragonal crystal 2. Figure 4 The (001) plane of the tetragonal crystal 1, and Figure 4 The (001) plane of the square crystal 2 is in the normal direction D with the surface of the first electrode layer 7. N The piezoelectric thin film 3, cut parallel to each other, is observed at any cross-section. For example... Figure 4 As shown, at least a portion or all of the (001) planes of the square crystal 2 are inclined relative to the (001) planes of the square crystal 1. In other words, at least a portion or all of the (001) planes of the square crystal 2 are inclined relative to the normal direction D of the surface of the first electrode layer 7. N Not perpendicular. In other words, at least part or all of the (001) face of the tetragonal crystal 2 may also be non-parallel to the surface of the first electrode layer 7.

[0047] Due to the crystal orientation of tetragonal crystal 1 and the tilt of the (001) plane of tetragonal crystal 2, the piezoelectric thin film 3 can have a large piezoelectric performance index (d). 33，f / ε r ε0). The inventors speculate that the piezoelectric thin film 3 can possess a large piezoelectric performance index (d) through the following mechanism. 33，f / ε r ε0).

[0048] The (001) plane of the tetragonal crystal 1 is in the normal direction D of the surface of the first electrode layer 7. N With the piezoelectric thin film 3 oriented upwards, and the c1 / a1 ratio of tetragonal crystal 1 being larger than the c2 / a2 ratio of tetragonal crystal 2, the piezoelectric thin film 3 readily possesses a low relative permittivity ε derived from tetragonal crystal 1. rFurthermore, the (001) plane of the tetragonal crystal 2 is tilted relative to the (001) plane of the tetragonal crystal 1. Therefore, when an electric field is applied, the polarization axis of the tetragonal crystal 2 is easily rotated, and the piezoelectric film 3 easily possesses a large piezoelectric strain constant d originating from the tetragonal crystal 2. 33，f For the reasons mentioned above, it is possible to achieve a low relative permittivity ε. r and large piezoelectric strain constant d 33，f Furthermore, the piezoelectric thin film 3 possesses a large piezoelectric performance index (d). 33 / ε r ε0).

[0049] The above mechanism is hypothetical, and the technical scope of the present invention is not limited by the above mechanism.

[0050] For example, the piezoelectric performance index (d) of the piezoelectric thin film 3 33，f / ε r ε0) can also be 180×10 －3 V·m / N or higher 273×10 －3 Below V·m / N, or 200×10 －3 V·m / N or higher 246×10 －3 Below V·m / N.

[0051] For example, the piezoelectric strain constant d of the piezoelectric thin film 3 33，f It can also be 62pC / N or higher than 150pC / N, or 84pC / N or higher than 129pC / N.

[0052] For example, the relative permittivity ε of the piezoelectric thin film 3 r (or ε) 33 It can also be 39 or more but less than 89, or 41 or more but less than 64.

[0053] like Figure 4 As shown, the absolute value of the angle between the (001) plane of tetragonal crystal 1 and the (001) plane of tetragonal crystal 2 is θ. 12 θ 12 It can also be between 1.0° and 10.0°. That is, Figure 4 The absolute value θ of the angle between (001)-T1 and (001)-T2 12 It can also be between 1.0° and 10.0°. At θ 12 When the angle is greater than 1.0°, the (001) plane of the tetragonal crystal 2 is sufficiently tilted. Therefore, the piezoelectric thin film 3 easily possesses a large piezoelectric strain constant d. 33，f At θ 12 When the angle is below 10°, it is difficult to damage the crystal orientation of the tetragonal crystal 1, and the piezoelectric thin film 3 easily possesses a large piezoelectric strain constant d. 33，f .

[0054] The spacing of the (100) planes of the crystals (lower crystals) contained in the first electrode layer 7 or the second intermediate layer 6 is denoted as aL. aL is preferably not equal to a1. For example, aL can also be greater than a1. aL can also be less than a1. The lattice mismatch rate Δa is defined as 100×(aL-a1) / a1. For example, the absolute value of the lattice mismatch rate Δa can also be 3.0% or more and 12.1% or less. That is, the absolute value of 100×(aL-a1) / a1 can also be 3.0% or more and 12.1% or less. When aL is not equal to a1 and the absolute value of Δa is within the above range, the (001) plane of the tetragonal crystal 1 is easily in the normal direction D of the surface of the first electrode layer 7. N With upward orientation, the (001) plane of tetragonal crystal 2 is easily tilted relative to the (001) plane of tetragonal crystal 1, c1 / a1 is easily greater than c2 / a2, θ 12 The lattice mismatch rate Δa can be easily controlled between 1.0° and 10.0°. a1 depends on the composition and crystal structure of the piezoelectric thin film 3, while aL depends on the composition and crystal structure of the first electrode layer 7 or the second intermediate layer 6. Therefore, the lattice mismatch rate Δa can also be controlled by selecting and combining the compositions and crystal structures of the piezoelectric thin film 3, the first electrode layer 7, and the second intermediate layer 6.

[0055] Compared to piezoelectric thin film 3, it is difficult for lattice mismatch to cause strain in the crystal structure in the bulk piezoelectric material. Therefore, most of the perovskite oxides constituting the bulk piezoelectric material are cubic crystals, and compared to piezoelectric thin film 3, the bulk piezoelectric material is less likely to have piezoelectricity caused by the tetragonal crystals of perovskite oxides.

[0056] The spacing and orientation of each crystal plane of tetragonal crystal 1 and tetragonal crystal 2, and θ 12 The determination can also be based on the X-ray diffraction (XRD) pattern of the piezoelectric film 3 measured in both out-of-plane and in-plane directions on the surface of the piezoelectric film 3. The crystal plane can also be referred to as a crystal facet. The spacing and orientation of each crystal plane of tetragonal crystal 1 and tetragonal crystal 2 can also be determined according to the reciprocal space mapping. That is, tetragonal crystal 1 and tetragonal crystal 2 can also be detected and identified by the reciprocal space map of the X-ray diffraction pattern of the piezoelectric film 3. The reciprocal space map can also be referred to as the intensity distribution map of diffracted X-rays in reciprocal space. For example, the reciprocal space map can also be obtained by, along the selected ω axis, The intensity of the diffracted X-rays of the piezoelectric thin film 3 is measured using two or more scanning axes, consisting of the ω-axis, χ-axis, 2θ-axis, and 2θχ-axis. For example, the reciprocal space diagram can also be constructed from the X-ray diffraction pattern measured by the ω-scan and 2θ / ω-scan. The reciprocal space diagram can also be a two-dimensional diagram of a coordinate system composed of orthogonal horizontal and vertical axes. The horizontal axis of the two-dimensional reciprocal space diagram can also represent the value corresponding to the reciprocal of the lattice constant in the in-plane direction of the surface of the piezoelectric thin film 3. For example, the horizontal axis of the reciprocal space diagram can also represent the value corresponding to the reciprocal of the spacing a (100) plane (i.e., 1 / a). The vertical axis of the two-dimensional reciprocal space diagram can also represent the value corresponding to the reciprocal of the lattice constant in the normal direction dn of the surface of the piezoelectric thin film 3. For example, the vertical axis of the reciprocal space diagram can also represent the value corresponding to the reciprocal of the spacing c (i.e., 1 / c) of the (001) plane. The reciprocal space diagram contains multiple spots. A spot corresponds to a diffracted X-ray originating from a crystallographic plane of either tetragonal crystal 1 or tetragonal crystal 2. The spacing and orientation of a crystallographic plane of either tetragonal crystal 1 or tetragonal crystal 2 can also be determined from the coordinates of a spot in the reciprocal space diagram.

[0057] Figure 6A and Figure 6B This is an example of the reciprocal space diagram of the piezoelectric thin film 3. Figure 6A S-T1 in the image is a spot corresponding to the (003) plane of the tetragonal crystal 1. Figure 6A S-T2 in the image is a spot corresponding to the (003) plane of the tetragonal crystal 2. Figure 6B S-T1 in the image is the spot corresponding to the (103) plane of tetragonal crystal 1. Figure 6B S-T2 in the diagram corresponds to the (103) plane of tetragonal crystal 2. The difference between the coordinates of S-T1 and S-T2 suggests the tilt of the (003) plane (and (001) plane) of tetragonal crystal 2 relative to the (003) plane (and (001) plane) of tetragonal crystal 1. That is, the difference between the coordinates of S-T1 and S-T2 suggests θ 12 .

[0058] The c1 / a1 ratio of the tetragonal crystal 1 can also be 1.120 or higher and 1.270 or lower, or 1.120 or higher and 1.267 or lower. When c1 / a1 is 1.120 or higher, the piezoelectric film 3 tends to have a low relative permittivity derived from the tetragonal crystal 1, and the piezoelectric performance index of the piezoelectric film 3 tends to increase. When c1 / a1 is 1.270 or lower, polarization reversal of the tetragonal crystal 1 tends to occur, and the piezoelectric performance index of the piezoelectric film 3 tends to increase. For example, c1 can also be... above Below. For example, a1 can also be... above the following.

[0059] c2 / a2 can also be between 1.010 and 1.115, or between 1.014 and 1.111. Since c2 / a2 falls within these ranges, polarization reversal of the tetragonal crystal 2 is easily induced, and the piezoelectric film 3 tends to possess a large d-value originating from the tetragonal crystal 2. 33，f The piezoelectric thin film 3 tends to have a large piezoelectric index. When c2 / a2 is outside the range mentioned above, the relative permittivity of the tetragonal crystal 2 tends to be too high or the piezoelectricity of the tetragonal crystal 2 itself deteriorates. For example, c2 can also be... above The following. For example, a2 can also be... above The following, or above the following.

[0060] The piezoelectric film 3 may also contain trace amounts of crystals other than tetragonal crystal 1 and tetragonal crystal 2.

[0061] For example, the piezoelectric thin film 3 may also contain a third tetragonal crystal as a tetragonal crystal of a perovskite-type oxide. The (001) plane of the third tetragonal crystal may also be in the normal direction D of the surface of the first electrode layer 7. N The orientation is upward. The spacing of the (001) planes of the third tetragonal crystal is c3. The spacing of the (100) planes of the third tetragonal crystal is a3. c3 / a3 can also be less than c1 / a1. The c3 / a3 of the third tetragonal crystal can also be between 1.010 and 1.115. The composition of the third tetragonal crystal can also be the same as that of tetragonal crystal 1 or tetragonal crystal 2. The composition of the third tetragonal crystal can also be different from that of tetragonal crystal 1 or tetragonal crystal 2. Except for the orientation of the (001) planes, the third tetragonal crystal can also be the same as that of tetragonal crystal 2.

[0062] For example, the piezoelectric thin film 3 may also contain rhombohedral crystals of perovskite-type oxides. The (001) facet of the rhombohedral crystal may also be in the normal direction D of the surface of the first electrode layer 7. N Upward orientation. The spacing a4 of the (001) face of the rhombohedral crystal can also be approximately the same as the spacing c3 of the (001) face of the third tetragonal crystal. The composition of the rhombohedral crystal can also be the same as that of tetragonal crystal 1, tetragonal crystal 2, or the third tetragonal crystal. The composition of the rhombohedral crystal can also be different from that of tetragonal crystal 1, tetragonal crystal 2, or the third tetragonal crystal.

[0063] The peak intensity (maximum intensity) of the X-ray diffracted from the (001) plane of tetragonal crystal 1 is I1. The peak intensity (maximum intensity) of the X-ray diffracted from the (001) plane of tetragonal crystal 2 is I2. 100×I2 / (I1+I2) can also be 0.30 or more and 10.0 or less, or 0.40 or more and 9.80 or less. When 100×I2 / (I1+I2) is within the above range, it is easy to take into account the low relative permittivity (ε) originating from tetragonal crystal 1.r ) and the large piezoelectric strain constant (d) originating from tetragonal crystal 2 33，f As a result, the piezoelectric film 3 tends to have a large piezoelectric performance index. The units for I1 and I2 can also be, for example, cps (counts per second). I1 and I2 can also be determined by out-of-plane measurement on the surface of the piezoelectric film 3. The measurement conditions for I1 and I2 can also be set such that I1 and I2 are each at least 3 bits higher than the background intensity.

[0064] I1 can also be proportional to the total area of ​​the (001) facets of the tetragonal crystal 1, and I2 can also be proportional to the total area of ​​the (001) facets of the tetragonal crystal 2. In other words, I1 can also be proportional to the amount of tetragonal crystal 1 contained in the piezoelectric film 3, and I2 can also be proportional to the amount of tetragonal crystal 2 contained in the piezoelectric film 3. Therefore, I2 / (I1+I2) can also be the presence ratio of tetragonal crystal 2 relative to the total amount of tetragonal crystal 1 and tetragonal crystal 2. That is, the presence ratio of tetragonal crystal 2 I2 / (I1+I2) relative to the total amount of tetragonal crystal 1 and tetragonal crystal 2 can also be 0.30% or more and less than 10.0%.

[0065] The degree of orientation of the (001) plane of tetragonal crystal 1 and the (001) plane of tetragonal crystal 2 can also be quantified based on the degree of orientation. The greater the degree of orientation of the (001) plane of tetragonal crystal 1 and the (001) plane of tetragonal crystal 2, the easier it is for the piezoelectric film 3 to have a large piezoelectric performance index. The degree of orientation of each crystal plane can also be calculated based on the peaks of diffracted X-rays originating from each crystal plane. The peaks of diffracted X-rays originating from each crystal plane can also be determined by out-of-plane measurement on the surface of the piezoelectric film 3.

[0066] The orientation degree of the (001) plane of the tetragonal crystal 1 can also be expressed as 100×I1 / ΣI 1(hkl) ΣI 1(hkl) It is the sum of the peak intensities of diffracted X-rays from each crystal plane of the tetragonal crystal 1, measured in the out-of-plane direction on the surface of the piezoelectric thin film 3. ΣI 1(hkl) For example, it can also be I. 1(001) +I 1(110) +I 1(111) I 1(001) This refers to I1 as mentioned above. That is, I. 1(001) The peak intensity (maximum intensity) of the diffracted X-rays from the (001) plane of the tetragonal crystal 1 is measured in the out-of-plane direction on the surface of the piezoelectric thin film 3. 1(110) The peak intensity (maximum intensity) of the diffracted X-rays from the (110) plane of the tetragonal crystal 1 is measured in the out-of-plane direction on the surface of the piezoelectric thin film 3. 1(111)The peak intensity (maximum intensity) of the diffracted X-rays on the (111) plane of the tetragonal crystal 1 is measured in the out-of-plane direction on the surface of the piezoelectric thin film 3.

[0067] The orientation degree of the (001) plane of tetragonal crystal 2 can also be expressed as 100×I² / ΣI. 2(hkl) ΣI 2(hkl) It is the sum of the peak intensities of diffracted X-rays from each crystal plane of the tetragonal crystal 2, measured in the out-of-plane direction on the surface of the piezoelectric thin film 3. ΣI 2(hkl) For example, it can also be I. 2(001) +I 2(110) +I 2(111) I 2(001) This refers to I2 as mentioned above. That is, I. 2(001) The peak intensity (maximum intensity) of the diffracted X-rays from the (001) plane of the tetragonal crystal 2 is measured in the out-of-plane direction on the surface of the piezoelectric thin film 3. 2(110) The peak intensity (maximum intensity) of the diffracted X-rays from the (110) plane of the tetragonal crystal 2 is measured in the out-of-plane direction on the surface of the piezoelectric thin film 3. 2(111) The peak intensity (maximum intensity) of the diffracted X-rays on the (111) plane of the tetragonal crystal 2 is measured in the out-of-plane direction on the surface of the piezoelectric thin film 3.

[0068] The degree of orientation of the (001) facet of tetragonal crystal 1 and the (001) facet of tetragonal crystal 2 can also be quantified by the degree of orientation F based on the Lotgering method. Even when the degree of orientation is calculated by any of the above methods, the degree of orientation of the (001) facet of tetragonal crystal 1 and the (001) facet of tetragonal crystal 2 can be 70% or more and 100% or less, preferably 80% or more and 100% or less, more preferably 90% or more and 100% or less. In other words, the (001) facet of tetragonal crystal 1 can also be preferred over other crystal faces of tetragonal crystal 1 in the normal direction D of the surface of the first electrode layer 7. N Upward orientation. The (001) plane of the tetragonal crystal 2 can also be oriented in the out-of-plane direction of the surface of the piezoelectric film 3, preferentially over other crystal planes of the tetragonal crystal 2.

[0069] The tetragonal crystal 1 can also be represented by the following chemical formula 1. The following chemical formula 1 is actually the same as the following chemical formula 1a.

[0070] x1(Bi 1－α E A α (E) B1 1－β E B2 β)O3-y1BiFeO3 (1)

[0071] (Bi x1(1－α)+y1 E A x1α (E) B1 x1(1－β) E B2 x1β Fe y1 )O 3±δ (1a)

[0072] In the above chemical formula 1, x1+y1 can also be 1.00. E in the above chemical formula 1... A It can also be at least one element selected from the group consisting of Na, K, Ag, and Ba. E in the above chemical formula 1... B1 It can also be at least one element selected from the group consisting of Mg, Al, Zr, Ti, Ni, and Zn. E in the above chemical formula 1... B2 It can also be at least one element selected from the group consisting of Mg, Al, Zr, Ti, Ni, and Zn. E B1 and E B2 They are all different. The units for α, β, x1, and y1 can also be moles.

[0073] Bi in the above chemical formula 1a x1(1－α)+y1 E A x1α The element at site A corresponds to the element in the perovskite structure. E in the above chemical formula 1a... B1 x1(1－β) E B2 x1β Fe y1 It corresponds to the element located at the B site in the perovskite structure.

[0074] In the above chemical formula 1, x1 can also be 0.05 or more and 0.90 or less. When x1 is 0.05 or more and 0.90 or less, the (001) plane of the tetragonal crystal 1 is easily in the normal direction D of the surface of the first electrode layer 7. N With upward orientation, the (001) plane of tetragonal crystal 2 is easily tilted relative to the (001) plane of tetragonal crystal 1, c1 / a1 is easily greater than c2 / a2, θ 12 It is easy to control the temperature between 1.0° and 10.0°.

[0075] In the above chemical formula 1, y1 can also be 0.10 or more and 0.95 or less. When y1 is 0.10 or more and 0.95 or less, the (001) plane of the tetragonal crystal 1 is easily in the normal direction D of the surface of the first electrode layer 7. NWith upward orientation, the (001) plane of tetragonal crystal 2 is easily tilted relative to the (001) plane of tetragonal crystal 1, c1 / a1 is easily greater than c2 / a2, θ 12 It is easy to control the temperature between 1.0° and 10.0°.

[0076] In the above chemical formula 1, α can also be 0.00 or more and less than 1.00. α can also be 0.00 or 0.50. In the above chemical formula 1, β can also be 0.00 or more and less than 1.00. β can also be 0.00 or 0.50.

[0077] In the above chemical formula 1a, δ can also be greater than 0. As long as the crystal structure (perovskite structure) of tetragonal crystal 1 is maintained, δ can also be a value other than 0. For example, δ can also be greater than 0 and less than 1.0. For example, δ can also be calculated based on the valence of each ion located at each of the A and B sites in tetragonal crystal 1. The valence of each ion can also be determined by X-ray photoelectron spectroscopy (XPS).

[0078] Bi and E contained in tetragonal crystal 1 A The total number of moles can also be expressed as [A]1, the E contained in tetragonal crystal 1. B1 E B2 The total number of moles of Fe can also be expressed as [B]1, and [A]1 / [B]1 can also be 1.0. As long as the crystal structure of tetragonal crystal 1 (perovskite structure) is maintained, [A]1 / [B]1 can also be a value other than 1.0. That is, [A]1 / [B]1 can be lower than 1.0, and [A]1 / [B]1 can also be greater than 1.0.

[0079] The tetragonal crystal 2 can also be represented by the following chemical formula 2. The following chemical formula 2 is actually the same as the following chemical formula 2a.

[0080] x2(Bi 1－α E A α (E) B1 1－β E B2 β )O3-y2BiFeO3 (2)

[0081] (Bi x2(1－α)+y2 E A x2α (E) B1 x2(1－β) E B2 x2β Fe y2 )O 3±δ (2a)

[0082] In the above chemical formula 2, x² + y² can also be 1.00. E in the above chemical formula 2...A It can also be at least one element chosen from the group consisting of Na, K, Ag, and Ba. E in the above chemical formula 2... B1 It can also be at least one element selected from the group consisting of Mg, Al, Zr, Ti, Ni, and Zn. E in the above chemical formula 2... B2 It can also be at least one element selected from the group consisting of Mg, Al, Zr, Ti, Ni, and Zn. E B1 and E B2 They are all different. The units for α, β, x², and y² can also be moles.

[0083] E in the above chemical formula 2 A It can be combined with E in the above chemical formula 1 A They can be the same, or they can be different. E in the above chemical formula 2... B1 It can be combined with E in the above chemical formula 1 B1 They can be the same, or they can be different. E in the above chemical formula 2... B2 It can be combined with E in the above chemical formula 1 B2 The same or different. x2 in chemical formula 2 can be the same as or different from x1 in chemical formula 1. y2 in chemical formula 2 can be the same as or different from y1 in chemical formula 1. α in chemical formula 2 can be the same as or different from α in chemical formula 1. β in chemical formula 2 can be the same as or different from β in chemical formula 1.

[0084] Bi in the above chemical formula 2a x2(1－α)+y2 E A x2α The element at site A corresponds to the element in the perovskite structure. E in the above chemical formula 2a... B1 x2(1－β) E B2 x2β Fe y2 It corresponds to the element located at the B site in the perovskite structure.

[0085] In the above chemical formula 2, x2 can also be 0.05 or more and 0.90 or less. When x2 is 0.05 or more and 0.90 or less, the (001) plane of the tetragonal crystal 1 is easily perpendicular to the normal direction D of the surface of the first electrode layer 7. N With upward orientation, the (001) plane of tetragonal crystal 2 is easily tilted relative to the (001) plane of tetragonal crystal 1, c1 / a1 is easily greater than c2 / a2, θ 12 It is easy to control the temperature between 1.0° and 10.0°.

[0086] In the above chemical formula 2, y2 can also be 0.10 or more and 0.95 or less. When y2 is 0.10 or more and 0.95 or less, the (001) plane of the tetragonal crystal 1 is easily aligned with the normal direction D of the surface of the first electrode layer 7. N With upward orientation, the (001) plane of tetragonal crystal 2 is easily tilted relative to the (001) plane of tetragonal crystal 1, c1 / a1 is easily greater than c2 / a2, θ 12 It is easy to control the temperature between 1.0° and 10.0°.

[0087] In the above chemical formula 2, α can also be 0.00 or more and less than 1.00. α can also be 0.00 or 0.50. In the above chemical formula 2, β can also be 0.00 or more and less than 1.00. β can also be 0.00 or 0.50.

[0088] In the above chemical formula 2a, δ can also be greater than 0. As long as the crystal structure (perovskite structure) of tetragonal crystal 2 is maintained, δ can also be a value other than 0. For example, δ can also be greater than 0 and less than 1.0. For example, δ can also be calculated based on the valence of each ion located at each of the A and B sites in tetragonal crystal 2. The valence of each ion can also be determined by X-ray photoelectron spectroscopy (XPS).

[0089] Bi and E contained in tetragonal crystal 2 A The total number of moles can also be expressed as [A]2, where the E contained in tetragonal crystal 2 is... B1 E B2 The total number of moles of Fe can also be expressed as [B]2, and [A]2 / [B]2 can also be 1.0. As long as the tetragonal crystal structure (perovskite structure) is maintained, [A]2 / [B]2 can also be a value other than 1.0. That is, [A]2 / [B]2 can be lower than 1.0, and [A]2 / [B]2 can also be greater than 1.0.

[0090] The piezoelectric thin film 3 can also be an epitaxial film. That is, the piezoelectric thin film 3 can also be formed by epitaxial growth. Through epitaxial growth, piezoelectric thin films 3 with excellent anisotropy and crystal orientation can be easily formed.

[0091] For example, the normal direction D of the surface of the first electrode layer 7 N The thickness of the piezoelectric thin film 3 can also be between 500 nm and 10,000 nm. The thickness of the piezoelectric thin film 3 can also be in the direction normal to the surface of the first electrode layer 7, D. NThe cross-section of the parallel piezoelectric thin film 3 is measured using a scanning electron microscope (SEM). The crystalline substrate 8, the first intermediate layer 5, the first electrode layer 7, the second intermediate layer 6, the piezoelectric thin film 3, and the second electrode layer 4 can also be identified based on the brightness differences in the reflected electron image of the cross-section of the piezoelectric thin film element 10. The thicknesses of the crystalline substrate 8, the first intermediate layer 5, the first electrode layer 7, the second intermediate layer 6, and the second electrode layer 4 can also be measured using the same method as for the thickness of the piezoelectric thin film 3.

[0092] For example, the surface area of ​​the piezoelectric thin film 3 can also be 1 μm. 2 Above 500mm 2 The areas of the crystalline substrate 8, the first intermediate layer 5, the first electrode layer 7, the second intermediate layer 6, and the second electrode layer 4 can also be the same as the area of ​​the piezoelectric thin film 3.

[0093] The composition of the piezoelectric thin film 3 can also be analyzed by at least one method selected from the group consisting of X-ray fluorescence (XRF), inductively coupled plasma (ICP) luminescence spectrometry, and X-ray photoelectron spectroscopy (XPS). It can also be analyzed along the normal direction D to the surface of the first electrode layer 7. N The piezoelectric thin film 3 is cut in a roughly parallel direction, and the composition of the tetragonal crystal 1 and tetragonal crystal 2 is determined by analyzing the cross-section of the piezoelectric thin film 3. The energy-dispersive X-ray diffraction (EDS) apparatus of a scanning electron microscope (SEM) or a scanning transmission electron microscope (STEM) can also be used for the cross-section analysis of the piezoelectric thin film 3. The crystal structure and crystal orientation of the piezoelectric thin film 3 can also be the crystal structure and crystal orientation at room temperature.

[0094] The piezoelectric thin film 3 is directly formed on the surface of the first electrode layer 7 or the second intermediate layer 6 through the following film-forming process. In the film-forming process, the piezoelectric thin film 3 is formed using pulsed-laser deposition (PLD) of a target material. The target material is the raw material for the piezoelectric thin film 3. The target material may also be composed of all elements common to all elements constituting the piezoelectric thin film 3. The composition of the target material may also be adjusted so that the molar ratio of each element constituting the target material is approximately the same as the molar ratio of each element constituting the piezoelectric thin film 3. For example, the molar ratio of each element constituting the target material may also be approximately the same as the molar ratio of each element constituting the above-described chemical formula 1 or chemical formula 2.

[0095] In the PLD method, the elements constituting the target are plasma-ionized and evaporated by irradiating the target with a pulsed laser. According to the PLD method, each element constituting the target can be plasma-ionized uniformly in an instant. As a result, the molar ratio of each element in the piezoelectric film 3 is easily made to match the molar ratio of each element in each target, thus easily suppressing elemental segregation in the piezoelectric film 3. Furthermore, according to the PLD method, the piezoelectric film 3 is easily epitaxially grown, readily forming a dense piezoelectric film 3 at atomic energy levels. For example, the pulsed laser can also be an excimer laser such as a KrF laser with a wavelength of 248 nm.

[0096] In the PLD method, the flux of the pulsed laser is controlled. Flux is translated into the energy density of the pulsed laser irradiating the target (unit: mJ / cm²). 2 The flux of a pulsed laser can also be expressed as the energy of the pulsed laser per unit area of ​​the target surface. The flux of a pulsed laser can also be expressed as 8 mJ / cm². 2 Above 12mJ / cm 2 The following applies when the flux of the pulsed laser is 8 mJ / cm². 2 Above 12mJ / cm 2 In the following situations, by appropriately controlling the epitaxial growth rate of the piezoelectric thin film 3, lattice mismatch between the piezoelectric thin film 3 and the first electrode layer 7, or lattice mismatch between the piezoelectric thin film 3 and the second intermediate layer 6, the growth of the piezoelectric thin film 3 is appropriately affected. As a result, the (001) plane of the tetragonal crystal 1 is easily affected by the normal direction D of the surface of the first electrode layer 7. N With upward orientation, the (001) plane of tetragonal crystal 2 is easily tilted relative to the (001) plane of tetragonal crystal 1, c1 / a1 is easily greater than c2 / a2, θ 12 It is easily controlled between 1.0° and 10.0°. This applies when the flux of the pulsed laser is below 8 mJ / cm². 2 In this case, the piezoelectric film 3 is difficult to have crystallinity, and the (001) plane of the tetragonal crystal 1 is difficult to be in the normal direction D of the surface of the first electrode layer 7. N Upward orientation. This is achieved when the flux of the pulsed laser is greater than 12 mJ / cm². 2 In this case, the (001) plane of tetragonal crystal 2 is difficult to tilt relative to the (001) plane of tetragonal crystal 1. That is, when the flux of the pulsed laser is greater than 12 mJ / cm 2 In this case, the epitaxial growth rate of the piezoelectric thin film 3 is too fast, therefore, the aforementioned lattice mismatch is unlikely to affect the growth of the piezoelectric thin film 3. As a result, not only the (001) plane of the tetragonal crystal 1, but also the (001) plane of the tetragonal crystal 2 is easily affected by the normal direction D of the surface of the first electrode layer 7. N Upward orientation.

[0097] In the PLD method, the growth rate of the piezoelectric film 3, as well as the anisotropy and orientation of the tetragonal crystals 1 and 2, can be controlled by changing the number of pulses (repetition frequency) of the pulsed laser. As the repetition frequency of the pulsed laser decreases, the growth rate of the piezoelectric film 3 decreases, and the anisotropy of the tetragonal crystals 1 and 2, as well as the orientation of their respective crystal planes, becomes higher. For example, the repetition frequency f of the pulsed laser in the film deposition process can also be approximately 10 Hz. When the repetition frequency f of the pulsed laser is 10 Hz, the (001) plane of the tetragonal crystal 1 is more likely to be in the normal direction D of the surface of the first electrode layer 7. N With upward orientation, the (001) plane of tetragonal crystal 2 is easily tilted relative to the (001) plane of tetragonal crystal 1, c1 / a1 is easily greater than c2 / a2, θ 12 It is easy to control the temperature between 1.0° and 10.0°.

[0098] The target material used as the raw material for the piezoelectric thin film 3 can also be manufactured by the following method.

[0099] Bi and E can also be used as initial raw materials for the target material. A E B And the respective oxides of Fe. As starting materials, substances that are calcined into oxides, such as carbonates or oxalates, can also be used instead of oxides. After thoroughly drying these starting materials at 100°C or higher, Bi and E are used. A E B The initial raw materials were weighed in a manner that ensured the molar ratio of Fe was consistent with the molar ratio of each element in the piezoelectric thin film 3. During the film formation process, Bi in the target material is more volatile than other elements. Therefore, the molar ratio of Bi in the target material can be adjusted to a higher value than the molar ratio of Bi in the piezoelectric thin film 3. When using raw materials containing K as E... A In this case, K in the target material is more volatile than other elements during the film formation process. Therefore, the molar ratio of K in the target material can also be adjusted to a higher value than the molar ratio of K in the piezoelectric thin film 3.

[0100] The weighed initial raw materials are thoroughly mixed in an organic solvent or water. The mixing time can be 5 to 20 hours. The mixing device can be, for example, a ball mill. After thoroughly drying the mixed initial raw materials, the initial raw materials are shaped using a stamping press. The shaped initial raw materials are pre-calcined to obtain a pre-calcined material. The pre-calcination temperature can be 750°C to 900°C. The pre-calcination time can be 1 to 3 hours. The pre-calcined material is pulverized in an organic solvent or water. The pulverization time can be 5 to 30 hours. The pulverization device can also be a ball mill. After drying the pulverized pre-calcined material, the pre-calcined material with added binder solution is granulated to obtain a pre-calcined material powder. The pre-calcined material powder is stamped to obtain a block-shaped shaped body.

[0101] By heating the block-shaped molded body, the binder in the molded body evaporates. The heating temperature can be above 400℃ but below 800℃. The heating time can be above 2 hours but below 4 hours.

[0102] After the binder evaporates, the molded body is sintered. The sintering temperature can be between 800°C and 1100°C. The sintering time can be between 2 hours and 4 hours. The heating and cooling rates of the molded body during the sintering process can be, for example, between 50°C / hour and 300°C / hour.

[0103] The target material is manufactured through the above processes. The average grain size of the perovskite oxide crystal contained in the target material can be, for example, between 1 μm and 20 μm.

[0104] In the film-forming process, the elements constituting the target material are evaporated under a vacuum atmosphere using the PLD method. The evaporated elements adhere to and accumulate on the surface of the first electrode layer 7 or the second intermediate layer 6, forming a piezoelectric thin film 3. Alternatively, the interior of the vacuum chamber can be heated during the film-forming process, simultaneously forming the piezoelectric thin film 3 within the vacuum chamber. For example, the temperature inside the vacuum chamber (film-forming temperature) can be between 450°C and 600°C. Higher film-forming temperatures improve the surface cleanliness of the first electrode layer 7 or the second intermediate layer 6, making it easier to improve the crystallinity of the piezoelectric thin film 3. At excessively high film-forming temperatures, the piezoelectric thin film 3 is difficult to crystallize. Furthermore, at excessively high film-forming temperatures, the elements constituting the piezoelectric thin film 3 are over-reduced, making it difficult to obtain a piezoelectric thin film 3 with the desired composition. Additionally, at excessively high film-forming temperatures, Bi or K easily detaches from the piezoelectric thin film 3, making it difficult to control the composition of the piezoelectric thin film 3.

[0105] For example, the oxygen partial pressure within the vacuum chamber can be between 0.1 Pa and 3.0 Pa. When the oxygen partial pressure is too low, it is difficult to fully oxidize the elements originating from the target material, making it difficult to form perovskite-type oxides, and the crystallinity of the piezoelectric thin film 3 is easily deteriorated. When the oxygen partial pressure is too high, the growth rate of the piezoelectric thin film 3 is easily reduced, and the crystallinity of the piezoelectric thin film 3 is easily deteriorated.

[0106] In the film formation process, in addition to controlling the flux and the repetition frequency of the pulsed laser, the number of times the pulsed laser irradiates the target (film formation time) can also be controlled. As the number of times the pulsed laser irradiates the target (film formation time) increases, the thickness of the piezoelectric film 3 tends to increase. In the film formation process, the distance between the surface of the first electrode layer 7 or the second intermediate layer 6 and the target can also be controlled. As the distance between the surface of the first electrode layer 7 or the second intermediate layer 6 and the target decreases, the thickness and growth rate of the piezoelectric film 3 tend to increase.

[0107] Alternatively, after forming the piezoelectric thin film 3 through a film-forming process, the piezoelectric thin film 3 can be annealed (heat-treated) in a vacuum chamber. The temperature of the piezoelectric thin film 3 during annealing (annealing temperature) can be, for example, between 300°C and 1000°C. Annealing of the piezoelectric thin film 3 tends to further improve its piezoelectric properties. In particular, annealing at temperatures between 850°C and 1000°C easily improves the piezoelectric properties of the piezoelectric thin film 3. However, annealing is not always necessary.

[0108] During the cooling process following the formation of the piezoelectric thin film 3 described above, compressive stress caused by temperature changes can also be generated within the piezoelectric thin film 3. Through this compressive stress, the piezoelectric thin film 3 is compressed in directions approximately parallel to the surface of the first electrode layer 7 (the a-axis and b-axis directions). As a result, tetragonal crystals 1 and 2 are easily formed.

[0109] The crystalline substrate 8 can also be a single-crystal substrate. For example, the crystalline substrate 8 can be a substrate made of a single crystal of Si, or a substrate made of a single crystal of a compound semiconductor such as GaAs. The crystalline substrate 8 can also be a substrate made of a single crystal of an oxide. The single crystal of the oxide can be, for example, MgO or perovskite-type oxide (e.g., SrTiO3). For example, the thickness of the crystalline substrate 8 can be 10 μm or more but less than 1000 μm. When the crystalline substrate 8 is conductive, the crystalline substrate 8 functions as an electrode layer (first electrode layer 7), therefore, the first electrode layer 7 may not be necessary. For example, the conductive crystalline substrate 8 can also be a single crystal of SrTiO3 doped with niobium (Nb). SOI (Silicon-on-Insulator) substrates can also be used as the crystalline substrate 8.

[0110] The crystal orientation of the crystalline substrate 8 can also be equal to the normal direction of its surface. That is, the surface of the crystalline substrate 8 can also be parallel to its crystal plane. The normal direction of the surface of the crystalline substrate 8 is parallel to the normal direction D of the surface of the first electrode layer 7. N Approximately parallel. The crystalline substrate 8 can also be a uniaxially oriented substrate. For example, the (100) plane of the crystalline substrate 8 of Si or the like can also be parallel to the surface of the crystalline substrate 8. That is, the

[100] direction of the crystalline substrate 8 of Si or the like can also be parallel to the normal direction of the surface of the crystalline substrate 8.

[0111] When the (100) plane of the crystalline substrate 8 (such as Si) is parallel to the surface of the crystalline substrate 8, the (001) plane of the tetragonal crystal 1 is easily aligned with the normal direction D of the surface of the first electrode layer 7. N Upward orientation.

[0112] As described above, the first intermediate layer 5 can also be disposed between the crystalline substrate 8 and the first electrode layer 7. The first intermediate layer 5 can also contain at least one material selected from the group consisting of titanium (Ti), chromium (Cr), titanium oxide (TiO2), silicon oxide (SiO2), zirconium oxide (ZrO2), and yttrium oxide (Y2O3). By interposing the first intermediate layer 5, the first electrode layer 7 can easily adhere to the crystalline substrate 8. The first intermediate layer 5 can also be crystalline. The crystalline surface of the first intermediate layer 5 can also be oriented in the normal direction to the surface of the crystalline substrate 8. Both the crystalline surface of the crystalline substrate 8 and the crystalline surface of the first intermediate layer 5 can also be oriented in the normal direction to the surface of the crystalline substrate 8. The first intermediate layer 5 can also be formed by sputtering, vacuum evaporation, printing, spin coating, or sol-gel methods.

[0113] The first intermediate layer 5 may also contain ZrO2 and oxides of rare earth elements. By including ZrO2 and oxides of rare earth elements in the first intermediate layer 5, the first electrode layer 7, composed of platinum crystals, is easily formed on the surface of the first intermediate layer 5. The (002) plane of the platinum crystals is easily formed in the normal direction D of the surface of the first electrode layer 7. N The platinum crystal (200) plane is readily oriented in the in-plane direction on the surface of the first electrode layer 7. The rare earth element may also be at least one selected from the group consisting of scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

[0114] The first intermediate layer 5 may also contain ZrO2 and Y2O3. For example, the first intermediate layer 5 may also be composed of yttrium oxide-stabilized zirconium oxide (ZrO2 with added Y2O3). The first intermediate layer 5 may also have a first layer composed of ZrO2 and a second layer composed of Y2O3. The first layer composed of ZrO2 may also be directly stacked on the surface of the crystalline substrate 8. The second layer composed of Y2O3 may also be directly stacked on the surface of the first layer. The first electrode layer 7 may also be directly stacked on the surface of the second layer composed of Y2O3. When the first intermediate layer 5 contains ZrO2 and Y2O3, the piezoelectric thin film 3 is easily epitaxially grown, and the (001) plane of the tetragonal crystal 1 is easily grown in the normal direction D of the surface of the first electrode layer 7. N With upward orientation, the (001) plane of tetragonal crystal 2 is easily tilted relative to the (001) plane of tetragonal crystal 1, c1 / a1 is easily greater than c2 / a2, θ 12 It is easy to control the temperature between 1.0° and 10.0°. Furthermore, when the first intermediate layer 5 contains ZrO2 and Y2O3, the first electrode layer 7, composed of platinum crystals, is easily formed on the surface of the first intermediate layer 5, and the (002) plane of the platinum crystals is easily formed in the normal direction D of the surface of the first electrode layer 7. N With upward orientation, the (200) plane of the platinum crystal is easily oriented in the in-plane direction on the surface of the first electrode layer 7.

[0115] The first electrode layer 7 may also be composed of at least one metal selected from the group consisting of platinum (Pt), palladium (Pd), rhodium (Rh), gold (Au), ruthenium (Ru), iridium (Ir), molybdenum (Mo), titanium (Ti), tantalum (Ta), and nickel (Ni). The first electrode layer 7 may also be composed of conductive metal oxides such as strontium ruthenium ruthenium oxide (SrRuO3), lanthanum nickel oxide (LaNiO3), or lanthanum strontium cobalt oxide ((La,Sr)CoO3). The first electrode layer 7 may also be crystalline. The crystalline plane of the first electrode layer 7 may also be in the normal direction D of the surface of the first electrode layer 7. N Upward orientation. That is, the crystal plane of the first electrode layer 7 can also be approximately parallel to the surface of the first electrode layer 7. The normal direction D of the surface of the first electrode layer 7... N The crystal plane of the upwardly oriented first electrode layer 7 can also be approximately parallel to the (001) plane of the tetragonal crystal 1. The thickness of the first electrode layer 7 can be, for example, 1 nm or more and 1.0 μm or less. The first electrode layer 7 can be formed by sputtering, vacuum evaporation, printing, spin coating, or sol-gel method. In the case of printing, spin coating, or sol-gel method, in order to improve the crystallinity of the first electrode layer 7, heat treatment (annealing) of the first electrode layer 7 can also be performed.

[0116] The first electrode layer 7 may also contain platinum crystals. The first electrode layer 7 may also consist solely of platinum crystals. The platinum crystals are cubic crystals with a face-centered cubic (fcc) lattice structure. The (002) plane of the platinum crystals may also be located in the normal direction D of the surface of the first electrode layer 7. N In terms of orientation, the (200) plane of the platinum crystal can also be oriented in the in-plane direction of the surface of the first electrode layer 7. In other words, the (002) plane of the platinum crystal can also be approximately parallel to the surface of the first electrode layer 7, and the (200) plane of the platinum crystal can also be approximately perpendicular to the surface of the first electrode layer 7. When the (002) plane and (200) plane of the platinum crystal constituting the first electrode layer 7 have the above-mentioned orientation, the piezoelectric thin film 3 is easy to grow epitaxially, and the (001) plane of the tetragonal crystal 1 is easily oriented in the normal direction D of the surface of the first electrode layer 7. N With upward orientation, the (001) plane of tetragonal crystal 2 is easily tilted relative to the (001) plane of tetragonal crystal 1, c1 / a1 is easily greater than c2 / a2, θ 12 It is easy to control the temperature between 1.0° and 10.0°.

[0117] As described above, the second intermediate layer 6 can also be disposed between the first electrode layer 7 and the piezoelectric thin film 3. The second intermediate layer 6 may also contain at least one compound selected from the group consisting of BaTiO3, SrRuO3, LaNiO3, and (La,Sr)CoO3. (La,Sr)CoO3 may also be, for example, La. 0.5 Sr 0.5 CoO3. The second intermediate layer 6 can also be crystalline. The second intermediate layer 6 can also be a laminate composed of at least two buffer layers selected from the group consisting of a layer containing BaTiO3 crystals, a layer containing SrRuO3 crystals, a layer containing LaNiO3 crystals, and a layer containing (La,Sr)CoO3 crystals. Any one of BaTiO3, SrRuO3, LaNiO3, and (La,Sr)CoO3 has a perovskite structure. Therefore, when the second intermediate layer 6 contains at least one compound selected from the group consisting of BaTiO3, SrRuO3, LaNiO3, and (La,Sr)CoO3, the piezoelectric thin film 3 is easily epitaxially grown, and the (001) plane of the tetragonal crystal 1 is easily grown in the normal direction D of the surface of the first electrode layer 7. N With upward orientation, the (001) plane of tetragonal crystal 2 is easily tilted relative to the (001) plane of tetragonal crystal 1, c1 / a1 is easily greater than c2 / a2, θ 12 The angle can be easily controlled between 1.0° and 10.0°. Furthermore, by introducing the second intermediate layer 6, the piezoelectric film 3 can easily adhere to the first electrode layer 7. The crystal plane of the second intermediate layer 6 can also be in the normal direction D of the surface of the first electrode layer 7. NThe second intermediate layer 6 can also be formed by sputtering, vacuum evaporation, printing, spin coating, or sol-gel method.

[0118] The second electrode layer 4 can also be composed of at least one metal selected from the group consisting of Pt, Pd, Rh, Au, Ru, Ir, Mo, Ti, Ta, and Ni. The second electrode layer 4 can also be composed of at least one conductive metal oxide selected from the group consisting of LaNiO3, SrRuO3, and (La,Sr)CoO3. The second electrode layer 4 can also be crystalline. The crystal plane of the second electrode layer 4 can also be in the normal direction D of the first electrode layer 7. N Upward orientation. The crystal plane of the second electrode layer 4 can also be approximately parallel to the surface of the first electrode layer 7. The normal direction D of the surface of the first electrode layer 7... N The crystal plane of the upwardly oriented second electrode layer 4 can also be approximately parallel to the (001) plane of the tetragonal crystal 1. The thickness of the second electrode layer 4 can be, for example, 1 nm or more and 1.0 μm or less. The second electrode layer 4 can be formed by sputtering, vacuum evaporation, printing, spin coating, or sol-gel method. In the case of printing, spin coating, or sol-gel method, in order to improve the crystallinity of the second electrode layer 4, heat treatment (annealing) of the second electrode layer 4 can also be performed.

[0119] Another intermediate layer (another second intermediate layer) may also be disposed between the piezoelectric thin film 3 and the second electrode layer 4. By intervening the other intermediate layer, the second electrode layer 4 can easily adhere to the piezoelectric thin film 3. The composition, crystal structure, and formation method of the other intermediate layer (another second intermediate layer) may also be the same as those of the second intermediate layer 6 described above. The other intermediate layer may also contain at least one selected from, for example, SrRuO3, LaNiO3, and (La,Sr)CoO3. The formation method of the other intermediate layer may also be sputtering, vacuum evaporation, printing, spin coating, or sol-gel method.

[0120] At least a portion or all of the surface of the piezoelectric thin film element 10 may also be covered by a protective film. By covering it with a protective film, the durability (moisture resistance, etc.) of the piezoelectric thin film element 10 is improved.

[0121] The piezoelectric thin film element of this embodiment has a wide variety of applications. For example, it can also be used in piezoelectric transducers and piezoelectric sensors. That is, the piezoelectric transducer of this embodiment (e.g., an ultrasonic transducer) can also include the piezoelectric thin film element described above. The piezoelectric transducer can also be an ultrasonic transducer, such as an ultrasonic sensor. The piezoelectric thin film element can also be a data acquisition device (vibration power generation element), for example. As mentioned above, the piezoelectric thin film element of this embodiment has excellent piezoelectric performance index; therefore, it is suitable for ultrasonic transducers. The piezoelectric thin film element can also be a piezoelectric sensor. For example, it can be a piezoelectric microphone, gyroscope sensor, pressure sensor, pulse wave sensor, or impact sensor. The piezoelectric thin film element can also be a SAW filter, BAW filter, oscillator, or acoustic multilayer film. The piezoelectric thin film element described above can also be included in a microelectromechanical system (MEMS). That is, the piezoelectric thin film element can be part or the entirety of a microelectromechanical system. For example, piezoelectric thin film elements can also be part of or integral to piezoelectric micromachined ultrasonic transducers (PMUTs). For example, products using piezoelectric micromachined ultrasonic transducers can also be biometric sensors (fingerprint sensors, vascular sensors, etc.), medical / healthcare sensors (blood pressure monitors, vascular imaging sensors, etc.), or ToF (Time of Flight) sensors.

[0122] Figure 5 This diagram shows a schematic cross-section of an ultrasonic transducer 10a comprising the aforementioned piezoelectric thin film element. The cross-section of the ultrasonic transducer 10a is perpendicular to the surfaces of the first electrode layer 7 and the piezoelectric thin film 3. The ultrasonic transducer 10a may also include: substrates 8a and 8b, a first electrode layer 7 disposed on substrates 8a and 8b, a piezoelectric thin film 3 overlapping the first electrode layer 7, and a second electrode layer 4 overlapping the piezoelectric thin film 3. An acoustic cavity 8c may also be provided below the piezoelectric thin film 3. Ultrasonic signals are transmitted or received through the flexure or vibration of the piezoelectric thin film 3. A first intermediate layer may also be disposed between substrates 8a and 8b and the first electrode layer 7. A second intermediate layer may also be disposed between the first electrode layer 7 and the piezoelectric thin film 3.

[0123] [Example]

[0124] The present invention will be described in detail through the following embodiments and comparative examples. The present invention is not limited to the following embodiments.

[0125] (Example 1)

[0126] In the fabrication of the piezoelectric thin film element in Example 1, a crystalline substrate made of Si was used. The (100) facet of the Si was parallel to the surface of the crystalline substrate. The crystalline substrate was a square of 20 mm × 20 mm. The thickness of the crystalline substrate was 500 μm.

[0127] Within a vacuum chamber, a first intermediate layer of crystalline material, composed of ZrO2 and Y2O3, is integrally formed on the surface of a crystalline substrate. The first intermediate layer is formed by sputtering. The thickness of the first intermediate layer is 30 nm.

[0128] Within a vacuum chamber, a first electrode layer composed of Pt crystals is integrally formed on the surface of the first intermediate layer. The first electrode layer is formed by sputtering. The thickness of the first electrode layer is 200 nm. The temperature inside the vacuum chamber is maintained at 500 °C during the formation of the first electrode layer.

[0129] The XRD pattern of the first electrode layer was measured using out-of-plane measurements on the surface of the first electrode layer. The XRD pattern of the first electrode layer was also measured using in-plane measurements on the surface of the first electrode layer. An X-ray diffraction apparatus (Smart Lab) manufactured by Rigaku Corporation was used for these XRD pattern measurements. Measurement conditions were set such that the peak intensity in each XRD pattern increased by at least three positions relative to the background intensity. Out-of-plane measurements detected the peaks of diffracted X-rays from the (002) plane of Pt crystals. That is, the peaks of diffracted X-rays from the (002) plane of Pt crystals in the normal direction D of the surface of the first electrode layer were detected. N Upward orientation. In-plane measurements revealed a peak in the diffraction X-rays from the (200) plane of the Pt crystal. That is, the (200) plane of the Pt crystal is oriented in the in-plane direction on the surface of the first electrode layer.

[0130] A piezoelectric thin film is directly formed on the surface of the first electrode layer by performing the above-described film deposition process (PLD method) in a vacuum chamber. A KrF laser with a wavelength of 248 nm is used as the pulsed laser in the film deposition process. The flux of the pulsed laser is adjusted to the values ​​shown in Table 1 below. The repetition frequency f1 of the pulsed laser in the film deposition process is adjusted to 10 Hz. The oxygen partial pressure in the vacuum chamber in the first film deposition process is maintained at 1 Pa. The temperature inside the vacuum chamber (film deposition temperature) during the formation of the first piezoelectric layer is maintained at 450 °C. The thickness of the piezoelectric thin film is adjusted to 2000 nm.

[0131] The composition of the target material used in the film-forming process is represented by the following chemical formula 1. In the case of Example 1, E in the following chemical formula 1 A E B1 and E B2The elements are those shown in Table 1 below. In the case of Example 1, α, β, x1, and y1 in the following chemical formula 1 are the values ​​shown in Table 1 below.

[0132] x1(Bi 1－α E A α (E) B1 1－β E B2 β )O3-y1BiFeO3 (1)

[0133] The composition of the piezoelectric thin film was analyzed using XRF. The results showed that the composition of the piezoelectric thin film was consistent with that of the target material.

[0134] The XRD pattern of the piezoelectric thin film was measured using out-of-plane measurements on the surface of the first piezoelectric layer with the aforementioned X-ray diffraction apparatus. Additionally, another XRD pattern of the piezoelectric thin film was measured using in-plane measurements on the surface of the first piezoelectric layer. Reciprocal space mapping of the piezoelectric thin film was performed using these measurements. Measurement conditions were set such that the peak intensity in each XRD pattern increased by at least one bit relative to the background intensity. The measurement apparatus and conditions for each XRD pattern were the same as described above. The reciprocal lattice space map of Example 1 is shown in... Figure 6A and Figure 6B As shown in the image.

[0135] The results of the above analysis using an X-ray diffraction apparatus indicate that the piezoelectric thin film has the following characteristics.

[0136] The piezoelectric thin film is composed of tetragonal perovskite oxide 1 and tetragonal perovskite oxide 2. It is difficult to identify tetragonal 1 and tetragonal 2 based on their composition.

[0137] The normal direction D of the (001) plane of the tetragonal crystal 1 on the surface of the first electrode layer N Top-priority orientation. That is, the normal direction D of the surface of the first electrode layer. N The orientation degree of the (001) plane of the tetragonal crystal 1 is 90% or more. As mentioned above, the orientation degree of the (001) plane of the tetragonal crystal 1 is expressed as 100×1 1(001) / (I 1(001) +I 1(110) +I 1(111) ). In the normal direction D of the surface of the first electrode layer N The crystal planes of the preferred orientation tetragonal crystal 1 are referred to as "orientation planes" in the following tables.

[0138] The (001) plane of the square crystal 2 is inclined relative to the (001) plane of the square crystal 1.

[0139] The c1 / a1 of tetragonal crystal 1 is greater than the c2 / a2 of tetragonal crystal 2.

[0140] θ in Example 1 12 The values ​​are shown in Table 1 below. θ 12 The definition is as described above.

[0141] The c1 / a1 values ​​in Example 1 are shown in Table 2 below.

[0142] The c2 / a2 values ​​in Example 1 are shown in Table 2 below.

[0143] In Example 1, 100×I2 / (I1+I2) is the value shown in Table 2 below. The definition of 100×I2 / (I1+I2) is as described above.

[0144] Inside a vacuum chamber, a second electrode layer composed of Pt is integrally formed on the surface of the piezoelectric thin film. The second electrode layer is formed by sputtering. The temperature of the crystalline substrate is maintained at 500°C during the formation of the second electrode layer. The thickness of the second electrode layer is 200 nm.

[0145] The laminate of Example 1 is fabricated through the above steps. Next, the laminate structure on the crystalline substrate is patterned using photolithography. After patterning, the laminate is cut and diced.

[0146] Through the above processes, a piezoelectric thin film element of Example 1 with a quadrilateral shape is obtained. The piezoelectric thin film element is composed of a crystalline substrate, a first intermediate layer directly superimposed on the crystalline substrate, a first electrode layer directly superimposed on the first intermediate layer, a piezoelectric thin film directly superimposed on the first electrode layer, and a second electrode layer directly superimposed on the piezoelectric thin film. The area of ​​the movable portion of the piezoelectric thin film is 600 μm × 600 μm.

[0147] <Evaluation of piezoelectricity>

[0148] The piezoelectricity of piezoelectric thin films is evaluated using the following methods.

[0149] [Calculation of relative permittivity]

[0150] The electrostatic capacitance C of the piezoelectric thin film element was measured. Details of the measurement of electrostatic capacitance C are as follows.

[0151] Measurement apparatus: ImpedanceGain-Phase Analyzer 4194A manufactured by Hewlett Packard Corporation

[0152] Frequency: 1kHz

[0153] Electric field: 10V / μm

[0154] Based on the following formula A, the relative permittivity ε is calculated from the measured value of the electrostatic capacitance C. r .

[0155] ε in Example 1 r As shown in Table 2 below.

[0156] C=ε0×ε r ×(S / d) (A)

[0157] In equation A, ε0 is the permittivity of vacuum (8.854 × 10⁻⁶). －12 Fm －1 In equation A, S represents the surface area of ​​the piezoelectric film. S can also be interpreted as the area of ​​the first electrode layer overlapping the piezoelectric film. In equation A, d represents the thickness of the piezoelectric film.

[0158] [Piezoelectric strain constant d] 33，f [Determination]

[0159] The piezoelectric strain constant d of a piezoelectric thin film was determined using a piezoelectric thin film element. 33，f . d 33，f The details of the measurement are as follows. Example 1: Piezoelectric strain constant d 33，f (The average value of the three measurement points) is shown in Table 2 below. (Diagram showing the average value of the three measurement points) 33，f and ε r Calculate the piezoelectric performance index (d) 33，f / ε r ε0). d of Example 1 33，f / ε r ε0 is shown in Table 2 below.

[0160] Measuring apparatus: d-meter manufactured by the Chinese Academy of Sciences 33 Instrument (ZJ-4B)

[0161] Frequency: 110Hz

[0162] Clamping pressure: 0.25N

[0163] (Examples 2-10, Comparative Examples 1 and 2)

[0164] The compositions of the targets in Examples 2-10, Comparative Examples 1 and 2 are represented by the above-described chemical formula 1. The E of the targets in Examples 2-10, Comparative Examples 1 and 2 is... A E B1 and E B2 The elements are shown in Table 1 below. The values ​​of α, β, x1, and y1 for Examples 2-10, Comparative Examples 1 and 2 are shown in Table 1 below. Only the pulsed laser flux of Comparative Example 2 differs from that of Example 1 in Examples 2-10, Comparative Examples 1 and 2. The flux of Comparative Example 2 was adjusted to the values ​​shown in Table 1 below.

[0165] In addition to the above, piezoelectric thin film elements of Examples 2-10, Comparative Examples 1 and 2 were prepared by the same method as in Example 1.

[0166] The analyses and measurements related to the piezoelectric films of Examples 2-10, Comparative Examples 1 and 2 were performed using the same method as in Example 1.

[0167] In any of Examples 2-10, Comparative Examples 1 and 2, the composition of the piezoelectric film is consistent with the composition of the target material.

[0168] In any of Examples 2-10 and Comparative Example 1, the piezoelectric thin film was composed of tetragonal perovskite oxide 1 and tetragonal perovskite oxide 2. It is difficult to identify tetragonal oxide 1 and tetragonal perovskite oxide 2 based on their composition.

[0169] The piezoelectric thin film of Comparative Example 2 is composed only of tetragonal crystals 1 of perovskite-type oxide. That is, the piezoelectric thin film of Comparative Example 2 does not contain tetragonal crystals 2.

[0170] In any of Examples 2-10 and Comparative Examples 1 and 2, the (001) plane of the tetragonal crystal 1 is in the normal direction D of the surface of the first electrode layer. N Prioritization.

[0171] In any of the embodiments 2 to 10, the (001) face of the square crystal 2 is inclined relative to the (001) face of the square crystal 1.

[0172] In Comparative Example 1, the (001) plane of the tetragonal crystal 2 is not inclined relative to the (001) plane of the tetragonal crystal 1. That is, in Comparative Example 1, not only the (001) plane of the tetragonal crystal 1, but also the (001) plane of the tetragonal crystal 2 is in the normal direction D of the surface of the first electrode layer. N Upward orientation.

[0173] In any of Examples 2-10 and Comparative Example 1, the c1 / a1 of the tetragonal crystal 1 is greater than the c2 / a2 of the tetragonal crystal 2.

[0174] θ of each of Examples 2-10 and Comparative Example 1 12 The values ​​are shown in Table 1 below.

[0175] The c1 / a1 values ​​for Examples 2-10, Comparative Examples 1 and 2 are shown in Table 2 below.

[0176] The c2 / a2 values ​​for Examples 2-10 and Comparative Example 1 are shown in Table 2 below.

[0177] The 100×I2 / (I1+I2) for Examples 2-10 and Comparative Example 1 are the values ​​shown in Table 2 below.

[0178] The piezoelectric properties of the piezoelectric films of Examples 2-10, Comparative Examples 1 and 2 were evaluated using the same method as in Example 1. The ε values ​​of the piezoelectric films of Examples 2-10, Comparative Examples 1 and 2 were also evaluated. r d 33 , f and d 33，f / ε r ε0 is shown in Table 2 below.

[0179] [Table 1]

[0180] unit <![CDATA[mJ / mm 2 ]]> － － － － － － － － angle Example 1 10 K Ti none 0.5 0.0 0.10 0.90 (001) 3.5 Example 2 10 Na Zr none 0.5 0.0 0.20 0.80 (001) 1.0 Example 3 10 Ag Zr none 0.5 0.0 0.05 0.95 (001) 5.4 Example 4 10 none Al none 0.0 0.0 0.10 0.90 (001) 8.4 Example 5 10 Na Ti none 0.5 0.0 0.85 0.15 (001) 10.0 Example 6 10 Ba Mg Ti 0.5 0.5 0.50 0.50 (001) 2.5 Example 7 10 K Mg Ti 0.5 0.5 0.15 0.85 (001) 7.2 Example 8 10 none Mg Ti 1.0 0.0 0.30 0.70 (001) 9.3 Example 9 10 Ag Ti none 0.5 0.0 0.70 0.30 (001) 3.5 Example 10 10 none Zn Ti 0.0 0.5 0.90 0.10 (001) 2.1 Comparative Example 1 25 K Mg Ti 0.5 0.5 0.50 0.50 (001) 0.0 Comparative Example 2 10 none Zn Ti 0.0 0.0 1.00 0.00 (001) －

[0181] [Table 2]

[0182]

[0183]

[0184] (Comparative Example 3)

[0185] As shown in Table 3, the temperature inside the vacuum chamber (film formation temperature) in the film formation process of Comparative Example 3 was maintained at 700°C. Except for the film formation temperature, the piezoelectric thin film element of Comparative Example 3 was fabricated using the same method as in Example 1.

[0186] The analyses and measurements related to the piezoelectric thin film of Comparative Example 3 were performed using the same method as in Example 1. The piezoelectric thin film of Comparative Example 3 was not crystalline. That is, neither tetragonal crystal 1 nor tetragonal crystal 2 was detected in the piezoelectric thin film of Comparative Example 3. As a result, the orientation plane and θ of Comparative Example 3 could not be measured. 12 c1 / a1, c2 / a2 and 100×I2 / (I1+I2).

[0187] The piezoelectricity of the piezoelectric film of Comparative Example 3 was evaluated using the same method as in Example 1. The ε... r d 33，f and d 33，f / ε r ε0 is shown in Table 4 below.

[0188] [Table 3]

[0189] unit ℃ <![CDATA[mJ / mm 2 ]]> － － － － － － － － angle Example 1 450 10 K Ti none 0.5 0.0 0.10 0.90 (001) 3.5 Comparative Example 3 700 10 K Ti none 0.5 0.0 0.10 0.90 none －

[0190] [Table 4]

[0191] unit － pC / N <![CDATA[10 －3 V·m / N]]> ％ － － Example 1 55 120 246 1.8 1.225 1.042 Comparative Example 3 253 30 13 － － －

[0192] (Examples 11-13)

[0193] In any of Examples 11-13, a second intermediate layer is integrally formed on the surface of the first electrode layer, and a piezoelectric thin film is integrally formed on the surface of the second intermediate layer. In Example 11, the second intermediate layer is composed of crystalline SrRuO3. The thickness of the second intermediate layer in Example 11 is 50 nm. In Example 12, the second intermediate layer is composed of crystalline LaNiO3. The thickness of the second intermediate layer in Example 12 is 50 nm. In Example 13, the second intermediate layer is composed of crystalline BaTiO3. The thickness of the second intermediate layer in Example 13 is 50 nm. In any of Examples 11-13, the (001) surface of the second intermediate layer is in the normal direction D of the surface of the first electrode layer. N Upward orientation. In Table 5 below, "SRO" refers to SrRuO3. In Table 5 below, "LNO" refers to LaNiO3. In Table 5 below, "BTO" refers to BaTiO3.

[0194] Except for the formation of a second intermediate layer, the piezoelectric thin film elements of Examples 11 to 13 were fabricated using the same method as in Example 1.

[0195] The analyses and measurements related to the piezoelectric films of Examples 11-13 were performed using the same method as in Example 1.

[0196] In any of the examples 11-13, the composition of the piezoelectric film is consistent with the composition of the target material.

[0197] In any of Examples 11-13, the piezoelectric thin film is composed of tetragonal perovskite oxide 1 and tetragonal perovskite oxide 2. It is difficult to identify tetragonal oxide 1 and tetragonal perovskite oxide 2 based on their composition.

[0198] In any of the embodiments 11-13, the (001) plane of the tetragonal crystal 1 is in the normal direction D of the surface of the first electrode layer. N Prioritization.

[0199] In any of the examples 11 to 13, the (001) plane of the square crystal 2 is inclined relative to the (001) plane of the square crystal 1.

[0200] In any of the examples 11 to 13, the c1 / a1 of the tetragonal crystal 1 is greater than the c2 / a2 of the tetragonal crystal 2.

[0201] Examples 11-13, each with θ 12 The values ​​are shown in Table 5 below.

[0202] The c1 / a1 values ​​for each of Examples 11 to 13 are shown in Table 6 below.

[0203] The c2 / a2 values ​​for each of Examples 11 to 13 are shown in Table 6 below.

[0204] The 100×I2 / (I1+I2) for each of Examples 11 to 13 are the values ​​shown in Table 6 below.

[0205] The piezoelectric properties of the piezoelectric films of Examples 11-13 were evaluated using the same method as in Example 1. The ε-coating of the piezoelectric films of Examples 11-13 was also evaluated. r d 33，f and d 33，f / ε r ε0 is shown in Table 6 below.

[0206] [Table 5]

[0207]

[0208] [Table 6]

[0209] unit － pC / N <![CDATA[10 －3 V·m / N]]> ％ － － Example 1 55 120 246 1.8 1.225 1.042 Example 11 56 121 244 2.2 1.210 1.037 Example 12 51 109 241 0.9 1.249 1.049 Example 13 63 123 221 4.9 1.267 1.028

[0210] (Example 14)

[0211] In the fabrication process of the piezoelectric thin film element of Example 14, neither the first intermediate layer nor the second intermediate layer was formed. In the fabrication process of the piezoelectric thin film element of Example 14, a first electrode layer composed of crystalline SrRuO3 was directly formed on the entire surface of a crystalline substrate. The (001) plane of SrRuO3 is in the normal direction D of the surface of the first electrode layer. N Upward orientation. The thickness of the first electrode layer in Example 14 is 200 nm.

[0212] Apart from the above, the piezoelectric thin film element of Example 14 was fabricated using the same method as in Example 1.

[0213] Measurements related to the first electrode layer of Example 14 were performed using the same method as in Example 1. In the case of Example 14, the crystal planes of the first electrode layer were not oriented in the in-plane direction on the surface of the first electrode layer. That is, in the case of Example 14, there was no in-plane orientation of the crystals of the first electrode layer.

[0214] The analyses and measurements related to the piezoelectric thin film of Example 14 were performed using the same method as in Example 1.

[0215] In Example 14, the composition of the piezoelectric film is consistent with the composition of the target material.

[0216] In Example 14, the piezoelectric film is composed of tetragonal perovskite oxide 1 and tetragonal perovskite oxide 2. It is difficult to identify tetragonal oxide 1 and tetragonal oxide 2 based on their composition.

[0217] In the case of Example 14, the (001) plane of the tetragonal crystal 1 is in the normal direction D of the surface of the first electrode layer. N Prioritization.

[0218] In the case of Example 14, the (001) face of the square crystal 2 is inclined relative to the (001) face of the square crystal 1.

[0219] In Example 14, the c1 / a1 of the tetragonal crystal 1 is greater than the c2 / a2 of the tetragonal crystal 2.

[0220] θ in Example 14 12 The values ​​are shown in Table 7 below.

[0221] The c1 / a1 values ​​for Example 14 are shown in Table 8 below.

[0222] The c2 / a2 values ​​in Example 14 are shown in Table 8 below.

[0223] The 100×I2 / (I1+I2) of Example 14 is the value shown in Table 8 below.

[0224] The piezoelectricity of the piezoelectric film of Example 14 was evaluated using the same method as in Example 1. The ε... r d 33，f and d 33，f / ε r ε0 is shown in Table 8 below.

[0225] [Table 7]

[0226]

[0227] [Table 8]

[0228] unit － pC / N <![CDATA[10 －3 V·m / N]]> ％ － － Example 1 55 120 246 1.8 1.225 1.042 Example 14 64 129 228 0.6 1.142 1.015

[0229] (Examples 15, 16, Comparative Examples 4 and 5)

[0230] The flux of the pulsed lasers in Examples 15, 16, and Comparative Examples 4 and 5 was adjusted to the values ​​shown in Table 9 below. Except for the flux, the piezoelectric thin film elements of Examples 15, 16, and Comparative Examples 4 and 5 were fabricated using the same method as in Example 1.

[0231] The analyses and measurements related to the piezoelectric thin films of Examples 15, 16, Comparative Examples 4 and 5 were performed using the same method as in Example 1.

[0232] In any of Examples 15, 16, Comparative Examples 4 and 5, the composition of the piezoelectric film is consistent with the composition of the target material.

[0233] The piezoelectric film of Comparative Example 4 was not crystalline. That is, neither tetragonal crystal 1 nor tetragonal crystal 2 was detected in the piezoelectric films of Comparative Example 4. As a result, the orientation plane and θ of Comparative Example 4 could not be determined. 12 c1 / a1, c2 / a2 and 100×I2 / (I1+I2).

[0234] In any of Examples 15, 16, and Comparative Example 5, the piezoelectric thin film was composed of tetragonal perovskite oxide 1 and tetragonal perovskite oxide 2. It was difficult to identify tetragonal oxide 1 and tetragonal perovskite oxide 2 based on their composition.

[0235] In any of the cases in Examples 15, 16 and Comparative Example 5, the (001) plane of the tetragonal crystal 1 is in the normal direction D of the surface of the first electrode layer. N Prioritization.

[0236] In the cases of Examples 15 and 16, the (001) face of the square crystal 2 is inclined relative to the (001) face of the square crystal 1.

[0237] In Comparative Example 5, the (001) plane of the tetragonal crystal 2 is not tilted relative to the (001) plane of the tetragonal crystal 1. That is, in Comparative Example 5, not only the (001) plane of the tetragonal crystal 1, but also the (001) plane of the tetragonal crystal 2 is in the normal direction D of the surface of the first electrode layer. N Upward orientation.

[0238] In any of the cases in Examples 15, 16 and Comparative Example 5, the c1 / a1 of the tetragonal crystal 1 is greater than the c2 / a2 of the tetragonal crystal 2.

[0239] θ of each of Examples 15, 16 and Comparative Example 5 12 The values ​​are shown in Table 9 below.

[0240] The c1 / a1 values ​​for Examples 15, 16 and Comparative Example 5 are shown in Table 10 below.

[0241] The c2 / a2 values ​​for Examples 15, 16 and Comparative Example 5 are shown in Table 10 below.

[0242] The 100×I2 / (I1+I2) values ​​for Examples 15, 16 and Comparative Example 5 are shown in Table 10 below.

[0243] The piezoelectric properties of the piezoelectric films of Examples 15, 16, and Comparative Examples 4 and 5 were evaluated using the same method as in Example 1. The ε-coating properties of the piezoelectric films of Examples 15, 16, and Comparative Examples 4 and 5 were also evaluated. r d 33，f and d 33，f / ε rε0 is shown in Table 10 below. However, the piezoelectric film of Comparative Example 4 does not have sufficient piezoelectricity. The d of Comparative Example 4 could not be measured. 33，f Therefore, it is impossible to determine d in Comparative Example 4. 33，f / ε r ε0.

[0244] [Table 9]

[0245] unit <![CDATA[mJ / mm 2 ]]> － － － － － － － － angle Comparative Example 4 5 K Ti none 0.5 0.0 0.10 0.90 none Example 15 8 K Ti none 0.5 0.0 0.10 0.90 (001) 4.2 Example 1 10 K Ti none 0.5 0.0 0.10 0.90 (001) 3.5 Example 16 12 K Ti none 0.5 0.0 0.10 0.90 (001) 1.8 Comparative Example 5 15 K Ti none 0.5 0.0 0.10 0.90 (001) 0.0

[0246] [Table 10]

[0247] unit － pC / N <![CDATA[10 －3 V·m / N]]> ％ － － Comparative Example 4 130 － － － － － Example 15 61 126 233 1.5 1.190 1.037 Example 1 55 120 246 1.8 1.225 1.042 Example 16 50 105 237 3.6 1.230 1.045 Comparative Example 5 41 60 165 5.3 1.240 1.040

[0248] Industrial availability

[0249] For example, the piezoelectric thin film element of one aspect of the present invention can also be applied to piezoelectric transducers and piezoelectric sensors.

[0250] Explanation of reference numerals in the attached figures

[0251] 3…piezoelectric thin film, 4…second electrode layer, 5…first intermediate layer, 6…second intermediate layer, 7…first electrode layer, 8…crystalline substrate, 8a, 8b…substrate, 10…piezoelectric thin film element, 10a…ultrasonic transducer (piezoelectric thin film element), D N …the normal direction of the surface of the first electrode layer, dn…the normal direction of the surface of the piezoelectric film, uc…the unit cell of the perovskite structure, uc1…the unit cell of tetragonal crystal 1, uc2…the unit cell of tetragonal crystal 2.

Claims

1. A piezoelectric thin film element comprising: Electrode layer; and A piezoelectric thin film, which is directly or indirectly superimposed on the electrode layer. The piezoelectric thin film comprises tetragonal crystal 1 of perovskite oxide and tetragonal crystal 2 of perovskite oxide. The tetragonal crystal 1 contains bismuth, iron, and element E. B And oxygen, The element E contained in the tetragonal crystal 1 B The element is selected from at least one element in the group consisting of magnesium, aluminum, zirconium, titanium, nickel, and zinc. The tetragonal crystal 2 contains bismuth, iron, and element E. B And oxygen, The element E contained in the tetragonal crystal 2 B The element is selected from at least one element in the group consisting of magnesium, aluminum, zirconium, titanium, nickel, and zinc. The (001) facet of the tetragonal crystal 1 is oriented in the normal direction of the surface of the electrode layer. The (001) facet of the square crystal 2 is inclined relative to the (001) facet of the square crystal 1. The spacing of the (001) planes of the square crystal 1 is c1. The spacing of the (100) planes of the square crystal 1 is a1. The spacing of the (001) planes of the square crystal 2 is c2. The spacing between the (100) planes of the square crystal 2 is a2. c1 / a1 is greater than c2 / a2. The absolute value of the angle between the (001) plane of the square crystal 1 and the (001) plane of the square crystal 2 is θ. 12 , The θ 12 For angles between 1.0° and 10.0°, The peak intensity of the X-rays diffracted from the (001) plane of the tetragonal crystal 1 is I1, and the peak intensity of the X-rays diffracted from the (001) plane of the tetragonal crystal 2 is I2. 100×I2 / (I1+I2) is above 0.30 and below 10.

0.

2. The piezoelectric thin film element according to claim 1, wherein, The c1 / a1 ratio is between 1.120 and 1.

270.

3. The piezoelectric thin film element according to claim 1, wherein, The c2 / a2 ratio is between 1.010 and 1.

115.

4. The piezoelectric thin film element according to claim 1, wherein, The tetragonal crystal 1 is represented by the following chemical formula 1. E in the following chemical formula 1 A The element is selected from at least one element in the group consisting of Na, K, Ag, and Ba. E in the following chemical formula 1 B1 It is selected from at least one element in the group consisting of Mg, Al, Zr, Ti, Ni and Zn. E in the following chemical formula 1 B2 It is selected from at least one element in the group consisting of Mg, Al, Zr, Ti, Ni and Zn. The E in the following chemical formula 1 B1 and the E mentioned above B2 They are different. In the following chemical formula 1, x1 is 0.05 or more and 0.90 or less. In the following chemical formula 1, y1 is 0.10 or more and 0.95 or less. x1 + y1 equals 1.

00. In the following chemical formula 1, α is greater than or equal to 0.00 and less than or equal to 1.

00. In the following chemical formula 1, β is greater than or equal to 0.00 and less than or equal to 1.

00. x1(Bi) 1－α E A α )(E B1 1－β E B2 β )O3-y1BiFeO3 (1).

5. The piezoelectric thin film element according to claim 1, wherein, The tetragonal crystal 2 is represented by the following chemical formula 2. E in the following chemical formula 2 A The element is selected from at least one element in the group consisting of Na, K, Ag, and Ba. E in the following chemical formula 2 B1 It is selected from at least one element in the group consisting of Mg, Al, Zr, Ti, Ni and Zn. E in the following chemical formula 2 B2 It is selected from at least one element in the group consisting of Mg, Al, Zr, Ti, Ni and Zn. The E in the following chemical formula 2 B1 and the E mentioned above B2 They are different. In the following chemical formula 2, x2 is greater than or equal to 0.05 and less than or equal to 0.

90. In the following chemical formula 2, y2 is between 0.10 and 0.

95. x² + y² = 1.00 In the following chemical formula 2, α is greater than or equal to 0.00 and less than or equal to 1.

00. In the following chemical formula 2, β is greater than or equal to 0.00 and less than or equal to 1.

00. x2(Bi 1－α E A α (E) B1 1－β E B2 β (O3-y2BiFeO3(2)) 6. The piezoelectric thin film element according to claim 1, wherein, It also has a crystalline substrate and a first intermediate layer. The first intermediate layer is disposed between the crystalline substrate and the electrode layer. The first intermediate layer contains ZrO2 and Y2O3.

7. The piezoelectric thin film element according to claim 1, wherein, It also has a second intermediate layer. The second intermediate layer is disposed between the electrode layer and the piezoelectric film. The second intermediate layer comprises at least one compound selected from the group consisting of BaTiO3, SrRuO3 and LaNiO3.

8. The piezoelectric thin film element according to claim 1, wherein, The electrode layer contains platinum crystals. The (002) plane of the platinum crystal is oriented in the normal direction of the surface of the electrode layer. The (200) facet of the platinum crystal is oriented in the in-plane direction of the surface of the electrode layer.

9. A piezoelectric transducer comprising a piezoelectric thin film element according to any one of claims 1 to 8.

Images