Piezoelectric thin film, Piezoelectric thin film device, Piezoelectric actuator, Piezoelectric sensor, Piezoelectric transducer, Hard disk, Print head and Inkjet printer

Abstract

Piezoelectric thin film containing a metal oxide of perovskite-like crystals, wherein the metal oxide contains bismuth, potassium, titanium, iron and the element M; the element M is at least one of the elements magnesium and nickel; all perovskite-like crystals in the piezoelectric thin film are tetragonal crystals with perovskite structure; and a (001) plane of the tetragonal crystals is oriented in the direction of the surface normal of the piezoelectric thin film, where the metal oxide has the chemical formula x(Bi α K 1-α )TiO3-yBi(M β Ti 1-β )O3-zBiFeO3, where each of x, y and z is a positive real number; x+y+z = 1; α is greater than 0 and less than 1; β is greater than 0 and less than 1; M by Mg γ No 1-γ is presented; and γ is 0 or greater and 1 or less.

Description

TECHNICAL AREA

[0001] The present invention relates to a piezoelectric thin film, a piezoelectric thin film device, a piezoelectric actuator, a piezoelectric sensor, a piezoelectric transducer, a hard disk drive, a print head, and an inkjet printer device. BACKGROUND

[0002] Piezoelectric materials are processed into various piezoelectric components depending on their intended use. For example, a piezoelectric actuator converts voltage into force through the inverse piezoelectric effect, which deforms a piezoelectric material when a voltage is applied to the piezoelectric material. Furthermore, a piezoelectric sensor converts force into voltage through the piezoelectric effect, which deforms a piezoelectric material when pressure is applied to the piezoelectric material. These piezoelectric components are incorporated into various electronic devices. In the current market, miniaturization and performance improvements of electronic devices are required, so piezoelectric devices (piezoelectric thin-film devices) using a piezoelectric thin film have been actively studied.However, the thinner the thickness of a piezoelectric material, the more difficult it is to obtain the piezoelectric effect and the inverse piezoelectric effect, so the development of a piezoelectric material with excellent piezoelectricity in the thin film state is expected.

[0003] Lead zirconate titanate (PZT), a ferroelectric perovskite material, is commonly used as a piezoelectric material. However, since PZT contains lead, which is harmful to the human body and the environment, the development of a lead-free piezoelectric material is expected to replace PZT. For example, in Non-Patent Literature 1 described below, BaTiO3-type materials are described as an example of lead-free piezoelectric materials. BaTiO3-type materials have comparatively excellent piezoelectricity among lead-free piezoelectric materials, and their application to thin-film piezoelectric devices is particularly expected.

[0004] Patent Literature 1, Patent Literature 2, Patent Literature 3 and Patent Literature 4 each show piezoelectric elements and compositions therefor. [Patent literature 1]: US 2015 / 0 364 675 A1 [Patent literature 2]: US 2015 / 0 141 834 A1 [Patent literature 3]: US 2009 / 0 230 211 A1 [Patent literature 4]: JP 2008- 4 781 A [Non-patent literature 1]: GUO, Yiping [et al.]:thickness dependence of electrical properties of highly (100)-oriented batio3 thin films prepared by one-step chemical solution deposition, Japanese Journal of Applied Physics, 2006, Vol. 45, No. 2R, p. 855. SUMMARY

[0005] The object of the present invention is to provide a piezoelectric thin film having excellent piezoelectricity, a piezoelectric thin film device and a piezoelectric actuator, a piezoelectric transducer, a hard disk drive, a print head and an inkjet printer device using the piezoelectric thin film device.

[0006] The piezoelectric thin film according to one aspect of the present invention is a piezoelectric thin film containing a metal oxide, wherein the metal oxide contains bismuth, potassium, titanium, iron and the element M, the element M is at least one of magnesium and nickel, at least a part of the metal oxide is a crystal having a perovskite structure, and a (001) plane, a (110) plane or a (111) plane of the crystal is oriented in the direction of the surface normal of the piezoelectric thin film.

[0007] The metal oxide is represented by the following chemical formula 1: x(Bi α K1- α )TiO3-yBi(M β Ti1- β )O3-ZBiFeO3 (1) where each of x, y and z in chemical formula 1 is a positive real number; x+y+z is equal to 1; α in chemical formula 1 is greater than 0 and less than 1; β in chemical formula 1 is greater than 0 and less than 1; M in chemical formula 1 is represented by Mg γ No 1γ and y is 0 or greater and 1 or less.

[0008] A three-dimensional coordinate system can be composed of an x-axis, a y-axis, and a z-axis; any coordinates in the coordinate system can be represented by (X, Y, Z); the coordinates (x, y, z) in the coordinate system can correspond to x, y, and z in the chemical formula 1; the coordinates A in the coordinate system can be (0.300, 0.100, 0.600), the coordinates B in the coordinate system can be (0.450, 0.250, 0.300), a coordinate C in the coordinate system can be (0.200, 0.500, 0.300), a coordinate D in the coordinate system can be (0.100, 0.300, 0.600), and (x, y, z) within a quadrilateral with vertices at coordinates A, coordinates B, coordinates C, and coordinates D.

[0009] The coordinates E in the coordinate system can be (0.400, 0.200, 0.400), the coordinates F in the coordinate system can be (0.200, 0.400, 0.400) and the coordinates (x, y, z) can be positioned within a quadrilateral with vertices at coordinates A, E, F and D.

[0010] The piezoelectric thin film can be an epitaxial film.

[0011] At least part of the crystal is a tetragonal crystal.

[0012] The piezoelectric thin film may be a ferroelectric thin film.

[0013] The piezoelectric thin film device according to one aspect of the present invention comprises the piezoelectric thin film described above.

[0014] The piezoelectric thin film device may include a single crystal substrate and the piezoelectric thin film stacked on the single crystal substrate.

[0015] The piezoelectric thin film device may include a single crystal substrate, an electrode layer stacked on the single crystal substrate, and the piezoelectric thin film stacked on the electrode layer.

[0016] The piezoelectric thin film device may include an electrode layer and the piezoelectric thin film stacked on the electrode layer.

[0017] The piezoelectric thin-film device may further comprise at least one intermediate layer, wherein the intermediate layer may be arranged between the single-crystal substrate and the electrode layer.

[0018] The piezoelectric thin-film device may further comprise at least one intermediate layer, wherein the intermediate layer may be arranged between the electrode layer and the piezoelectric thin film.

[0019] The electrode layer may contain a platinum crystal, wherein the (002) plane of the platinum crystal may be oriented perpendicular to the surface of the electrode layer and the (200) plane of the platinum crystal may be oriented parallel to the surface of the electrode layer.

[0020] The piezoelectric actuator according to one aspect of the present invention comprises the piezoelectric thin film device described above.

[0021] The piezoelectric sensor according to one aspect of the present invention comprises the piezoelectric thin film device described above.

[0022] The piezoelectric transducer according to one aspect of the present invention comprises the piezoelectric thin film device described above.

[0023] The hard disk drive according to one aspect of the present invention comprises a head stack assembly, wherein the head stack assembly comprises a head assembly, and the head assembly comprises the piezoelectric actuator described above.

[0024] The printhead according to one aspect of the present invention comprises the piezoelectric actuator described above.

[0025] The inkjet printing apparatus according to one aspect of the present invention comprises the printhead described above.

[0026] According to the present invention, a piezoelectric thin film having excellent piezoelectricity, a piezoelectric thin film device and a piezoelectric actuator, a piezoelectric sensor, a piezoelectric transducer, a hard disk drive, a print head, and an inkjet printer device using the piezoelectric thin film device are provided. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1A is a schematic diagram of a piezoelectric thin film device according to an embodiment of the present invention, and Fig. 1B is an exploded perspective view of the Fig. 1A shown piezoelectric thin-film device, wherein in Fig. 1B a first electrode layer, a first intermediate layer, a second intermediate layer and a second electrode layer were omitted. Fig. Figure 2 is a perspective view of a unit cell of the perovskite structure. Fig. Figure 3A is a perspective view of a unit cell of the perovskite structure showing a (001) plane of the perovskite structure; Fig. Figure 3B is a perspective view of a unit cell of the perovskite structure showing a (110) plane of the perovskite structure; and Fig.Figure 3C is a perspective view of a unit cell of the perovskite structure showing a (111) plane of the perovskite structure. Fig. Figure 4 is a three-dimensional coordinate system representing the composition of a piezoelectric thin film. Fig. 5 is a triangular coordinate system corresponding to the Fig. 4 corresponds to the triangle shown. Fig. 6 is a schematic diagram of a head assembly according to an embodiment of the present invention. Fig. 7 is a schematic diagram of a piezoelectric actuator according to an embodiment of the present invention. Fig. 8 is a schematic diagram (top view) of a gyro sensor according to an embodiment of the present invention. Fig. 9 is a cross-sectional view of the Fig. 8, seen along the arrows AA. Fig.10 is a schematic diagram of a pressure sensor according to an embodiment of the present invention. Fig. 11 is a schematic diagram of a pulse wave sensor according to an embodiment of the present invention. Fig. 12 is a schematic diagram of a hard disk drive according to an embodiment of the present invention. Fig. 13 is a schematic diagram of an inkjet printer according to an embodiment of the present invention. DETAILED PRESENTATION

[0027] The details of a suitable embodiment of the present invention will be described with reference to the drawings as follows. However, the present invention is not limited to the following embodiments. In the drawings, the same symbols are assigned to the same or corresponding elements. Fig. 1A and Fig.The X, Y, and Z axes shown in Figure 1B are three mutually orthogonal coordinate axes. Fig. 1A and Fig. 1B have nothing to do with the coordinate systems shown in Fig. 4 and Fig. 5 shown coordinate systems. (Piezoelectric thin film and piezoelectric thin film device)

[0028] The piezoelectric thin-film device according to the present embodiment comprises a piezoelectric thin film. For example, as shown in Fig.1A, a piezoelectric thin-film device 10 according to the present embodiment includes a single-crystal substrate 1, a first electrode layer 2 (lower electrode layer) stacked on the single-crystal substrate 1, a piezoelectric thin-film 3 stacked on the first electrode layer 2, and a second electrode layer 4 (upper electrode layer) stacked on the piezoelectric thin-film 3. The piezoelectric thin-film device 10 may include a first intermediate layer 5, wherein the first intermediate layer 5 may be disposed between the single-crystal substrate 1 and the first electrode layer 2, and the first electrode layer 2 may be stacked directly on the surface of the first intermediate layer 5.The piezoelectric thin-film device 10 may include a second intermediate layer 6, wherein the second intermediate layer 6 may be disposed between the first electrode layer 2 and the piezoelectric thin film 3, and the piezoelectric thin film 3 may be directly stacked on the surface of the second intermediate layer 6. The thickness of the single-crystal substrate 1, the first intermediate layer 5, the first electrode layer 2, the second intermediate layer 6, the piezoelectric thin film 3, and the second electrode layer 4 may each be uniform. As shown in FIG. Fig. 1B, the direction dn of the surface normal of the piezoelectric thin film 3 can be approximately parallel to the surface normal D N of the single crystal substrate 1.

[0029] A modified example of the piezoelectric thin-film device 10 may not include a single-crystal substrate 1. For example, the single-crystal substrate 1 may be removed after forming the first electrode layer 2 and the piezoelectric thin-film film 3. A modified example of the piezoelectric thin-film device 10 may not include a second electrode layer 4. After a piezoelectric thin-film device without a second electrode layer is delivered as a product to an electronic device manufacturer, a second electrode layer may be attached to the piezoelectric thin-film device in a manufacturing process of the electronic device. In the case where the single-crystal substrate 1 functions as an electrode, a modified example of the piezoelectric thin-film device 10 may not include a first electrode layer 2.In other words, a modified example of the piezoelectric thin-film device 10 may include a single-crystal substrate 1 and a piezoelectric thin film 3 stacked on the single-crystal substrate 1. The piezoelectric thin film 3 may be stacked directly on the single-crystal substrate 1. The piezoelectric thin film 3 may be stacked on the single-crystal substrate 1 via at least the first intermediate layer 5 or the second intermediate layer 6.

[0030] The piezoelectric thin film 3 contains a metal oxide. The metal oxide contains bismuth (Bi), potassium (K), titanium (Ti), iron (Fe), and an element M. The element M is at least one of magnesium (Mg) and nickel (Ni). The metal oxide is the main component of the piezoelectric thin film 3. The proportion of the metal oxide in the entire piezoelectric thin film 3 can be 99 mol% or more and 100 mol% or less. The piezoelectric thin film 3 must consist only of the metal oxide.

[0031] At least part of the metal oxide is a crystal with a perovskite structure. The entire metal oxide may be a crystal with a perovskite structure. In the following, crystals with a perovskite structure are referred to as perovskite-like crystals. The unit cell of perovskite-like crystals is Fig.2. An element that occupies an A-site of a unit cell uc is Bi or K. An element that occupies a B-site of a unit cell uc is Ti, Mg, Ni or Fe. The elements in Fig. The unit cell uc shown in Figure 2 is the same as that shown in Fig. 3A, Fig. 3B and Fig. 3C shown unit cell uc. In Fig. 3A, Fig. 3B and Fig. However, in Figure 3C, the B site and oxygen (O) are omitted from the unit cell uc to represent a crystal plane. The symbol a is a lattice constant corresponding to the distance between the (100) planes of a perovskite-like crystal. The symbol b is a lattice constant corresponding to the distance between the (010) planes of a perovskite-like crystal. The symbol c is a lattice constant corresponding to the distance between the (001) planes of a perovskite-like crystal.

[0032] The (001) plane, the (110) plane, or the (111) plane of the perovskite-like crystal is oriented in the direction of the surface normal dn of the piezoelectric thin film 3. For example, as in Fig. 3A, the (001) plane of a perovskite-like crystal may face the surface normal dn of a piezoelectric thin film 3. In other words, the

[001] direction (orientation of the crystal plane) of a perovskite-like crystal may be approximately parallel to the surface normal dn of the piezoelectric thin film 3. As shown in Fig. 3B, the (110) plane of a perovskite-like crystal may face the surface normal dn of the piezoelectric thin film 3. In other words, the

[110] direction (orientation of the crystal plane) of a perovskite-like crystal may be approximately parallel to the surface normal dn of the piezoelectric thin film 3. As shown in Fig.As shown in Figure 3C, the (111) plane of a perovskite-type crystal may face the surface normal dn of the piezoelectric thin film 3. In other words, the

[111] direction (crystal plane orientation) of a perovskite-type crystal may be approximately parallel to the surface normal dn of the piezoelectric thin film 3. The perovskite-type crystal may be polarized in the

[001] ,

[110] , or

[111] direction. Consequently, since the (001) plane, the (110) plane, or the (111) plane is oriented toward the surface normal dn of the piezoelectric thin film 3, the piezoelectric thin film 3 may exhibit piezoelectricity. The crystal orientation described below means that the (001) plane, the (110) plane, or the (111) plane of a perovskite-like crystal is oriented in the direction of the surface normal dn of the piezoelectric thin film 3.

[0033] The piezoelectric thin film 3 may contain a plurality of perovskite-like crystals, and the (001) planes of all perovskite-like crystals may be oriented in the direction of the surface normal dn of the piezoelectric thin film 3. The (110) planes of all perovskite-like crystals may be oriented in the direction of the surface normal dn of the piezoelectric thin film 3. The (111) planes of all perovskite-like crystals may be oriented in the direction of the surface normal dn of the piezoelectric thin film 3.The (001) planes of a portion of the perovskite-like crystals may be oriented in the direction of the surface normal dn of the piezoelectric thin film 3, the (110) planes of another portion of the perovskite-like crystals may be oriented in the direction of the surface normal dn of the piezoelectric thin film 3, and the (111) planes of another portion of the perovskite-like crystals may be oriented in the direction of the surface normal dn of the piezoelectric thin film 3. The (001) planes of a portion of the perovskite-like crystals may be oriented in the direction of the surface normal dn of the piezoelectric thin film 3, and the (110) planes of a remaining portion of the perovskite-like crystals may be oriented in the direction of the surface normal dn of the piezoelectric thin film 3.The (110) planes of a portion of the perovskite-like crystals may be oriented in the direction of the surface normal dn of the piezoelectric thin film 3, and the (111) planes of a remaining portion of the perovskite-like crystals may be oriented in the direction of the surface normal dn of the piezoelectric thin film 3. The (001) planes of a portion of the perovskite-like crystals may be oriented in the direction of the surface normal dn of the piezoelectric thin film 3, and the (111) planes of a remaining portion of the perovskite-like crystals may be oriented in the direction of the surface normal dn of the piezoelectric thin film 3.

[0034] The orientation degree of the respective crystal planes can be quantified by the orientation degree. The orientation degree of the respective crystal planes can be calculated based on the X-ray diffraction reflection of the respective crystal plane. The X-ray diffraction reflections of the respective crystal planes can be measured in out-of-plane measurement of the surface of the piezoelectric thin film 3. The orientation degree of the (001) plane can be calculated by 100×I (001) / IΣ (hkl) The degree of orientation of the (110) plane can be represented by 100×I (110) / IΣ (hkl) The degree of orientation of the (111) plane can be represented by 100×I (111) / IΣ (hkl) be presented. I (001) is the maximum of the X-ray diffraction reflection of the (001) plane. I (110) is the maximum of the X-ray diffraction reflection of the (110) plane. I (111) is the maximum of the X-ray diffraction reflection of the (111) plane. ΣI (hkl) is I (001) +I (110) +I(111) The degree of orientation of the (001) plane can be determined by 100×S (001) / ΣS (hkl) The degree of orientation of the (110) plane can be represented by 100×S (110) / ΣS (hkl) The degree of orientation of the (111) plane can be represented by 100×S (111) / ΣS (hkl) be displayed. S (001) is the area of ​​the X-ray diffraction reflection of the (001) plane (integration of the peak). S (110) is the area of ​​the X-ray diffraction reflection of the (110) plane (integration of the peak). S (111) is the area of ​​the X-ray diffraction reflection of the (111) plane (integration of the peak). ΣS (hkl) is S (001) +S (110) +S (111)The orientation degree of each crystal plane can be quantified by the orientation degree F according to the Lotgering method. The higher the orientation degree of the crystal plane, the larger the piezoelectric constant of a piezoelectric thin film. Therefore, the orientation degree of a crystal plane can be 70% or more and 100% or less, preferably 80% or more and 100% or less, or more preferably 90% or more and 100% or less.

[0035] Since the piezoelectric thin film 3 tends to have a large piezoelectric constant (d 33 ), it is particularly preferable that the (001) plane of a perovskite-type crystal is oriented in the direction of the surface normal dn of the piezoelectric thin film 3. In other words, it is preferable that the orientation degree of the (001) plane is higher than the orientation degree of the (110) plane and the (111) plane.

[0036] The perovskite-like crystal may be at least one selected from the group consisting of tetragonal crystals, cubic crystals, and rhombohedral crystals at room temperature, at Curie temperature, or temperatures below. It is preferable that at least a part of the perovskite-like crystals be tetragonal crystals. In other words, it is preferable that a is equal to b and c / a is greater than 1.0. It is even more preferable that all the perovskite-like crystals be tetragonal crystals. Since an in-plane stress is applied to the surface of the piezoelectric thin film 3, the piezoelectric thin film 3 tends to contract in the in-plane direction.As a result, the lattice constants a and b in the in-plane direction of the piezoelectric thin film 3 tend to be smaller than the lattice constant c in the surface normal direction dn of the piezoelectric thin film 3, so the perovskite-like crystal tends to be a tetragonal crystal. When the perovskite-like crystal is a tetragonal crystal with the crystal orientation described above, the piezoelectric thin film 3 tends to have a large piezoelectric constant d. 33 .

[0037] The (001) plane of the tetragonal crystal should preferably be oriented in the direction of the surface normal dn of the piezoelectric thin film 3. Due to the in-plane stress described above, the lattice constant c in the direction of the surface normal dn of the piezoelectric thin film 3 tends to be larger than the in-plane lattice constants a and b. As a result, the piezoelectric thin film 3 tends to be polarized in the direction of the surface normal dn of the piezoelectric thin film 3, and the (001) plane of the tetragonal crystal tends to be oriented in the direction of the surface normal dn of the piezoelectric thin film 3. Since the (001) plane of the tetragonal crystal is oriented in the direction of the surface normal dn of the piezoelectric thin film 3, the piezoelectric thin film 3 tends to have an even larger piezoelectric constant d 33Unlike piezoelectric thin films, 3 in bulk piezoelectric materials, distortions in the crystal structure due to in-plane strain rarely occur. Therefore, most perovskite-like crystals in bulk piezoelectric materials are cubic crystals, and it is difficult for bulk piezoelectric materials to exhibit the piezoelectricity caused by tetragonal perovskite-like crystals.

[0038] Since the piezoelectric thin film 3 has the above-described composition and crystal orientation, the piezoelectric thin film 3 can have a large piezoelectric constant (d 33). The crystal orientation described above is a property inherent in a thin film. The thin film is a crystalline film formed by a vapor-phase growth process or a solution-phase process. On the other hand, it is difficult for a bulk piezoelectric material having the same composition as the piezoelectric thin film 3 to exhibit the crystal orientation described above. This is because the bulk piezoelectric material is a sintered material powder (ceramic) containing the elements required for the piezoelectric material, so it is difficult to control the structure and orientation of many crystals constituting the sintered material. Since the bulk piezoelectric material contains Fe, the resistivity of the bulk piezoelectric material is lower compared to the piezoelectric thin film 3.As a result, leakage current tends to occur in the piezoelectric bulk material. Accordingly, it is difficult to polarize the piezoelectric bulk material by applying a high electric field, and it is difficult to achieve a large piezoelectric constant (i.e., λ). 33 ) to obtain.

[0039] The metal oxide contained in the piezoelectric thin film 3 can be represented by Chemical Formula 1 described below. Chemical Formula 1 is essentially the same as Chemical Formula 1a described below. x(Bi α K 1-α )TiO3-yBi(M β Ti 1-β )O3-zBiFeO3 (1) (Bi α K 1-α ) x Bi y+z Ti x (M β Ti 1-β ) y Fe z O 3±δ (1a)

[0040] In chemical formula 1, x, y, and z are each positive real numbers. Here, x+y+z is equal to 1. x in chemical formula 1 is greater than 0 and less than 1. y in chemical formula 1 is greater than 0 and less than 1. z in chemical formula 1 is greater than 0 and less than 1. α in chemical formula 1 is greater than 0 and less than 1. β in chemical formula 1 is greater than 0 and less than 1. Since the piezoelectric thin film 3 tends to have a large d 33 to have, α can be 0.5 and β can be 0.5. M is represented in the chemical formula 1 by Mg γ Ni1- γrepresented. Here, γ is 0 or more and 1 or less. The molar sum of Bi and K in the metal oxide can be represented by [A], and the molar sum of Ti, Fe, and element M in the metal oxide can be represented by [B], and [A] / [B] can be 1.0. As long as the metal oxide can have a perovskite structure, [A] / [B] can take a value other than 1.0. In other words, [A] / [B] can be less than 1.0 or greater than 1.0. δ is 0 or greater in Chemical Formula 1a. As long as the metal oxide can have a perovskite structure, δ can take a value other than 0, for example, δ can be more than 0 and 1.0 or less. For example, δ can be calculated from the valences of the respective ions on the A site and the B site of the perovskite structure. The valences of the respective ions can be measured by X-ray photoelectron spectroscopy (XPS).As long as the piezoelectricity of the piezoelectric thin film 3 is not impaired, the piezoelectric thin film 3 may contain another element besides Bi, K, Ti, Fe, an element M and O.

[0041] In the following (Bi α K1- α )TiO3 is referred to as BKT. Bi(M β Ti1- β )O3 is called BMT. BiFeO3 is called BFO. A metal oxide with a composition represented by the sum of BKT and BMT is called BKT-BMT. A metal oxide with a composition represented by the chemical formula 1 is called xBKT-yBMT-zBFO. The crystals of BKT, BMT, BFO, BKT-BMT, and xBKT-yBMT-zBFO each have a perovskite structure.

[0042] A BKT crystal is a tetragonal crystal at room temperature, and BKT is a ferroelectric material. A BMT crystal is a rhombohedral crystal at room temperature, and BMT is a ferroelectric material. A BFO crystal is a rhombohedral crystal at room temperature, and BFO is a ferroelectric material. A BKT-BMT thin film is a tetragonal crystal at room temperature. The c / a of the BKT-BMT tetragonal crystal tends to be larger than the c / a of BKT and BMT, respectively. A BKT-BMT thin film exhibits excellent ferroelectric properties compared to a BKT thin film and a BMT thin film. A xBKT-yBMT-zBFO thin film tends to be a tetragonal crystal at room temperature. The c / a of the tetragonal crystal of xBKT-yBMT-zBFO tends to be larger than the c / a of BKT-BMT.A thin film of xBKT-yBMT-zBFO has excellent ferroelectric properties compared to a thin film of BKT-BMT. In other words, the piezoelectric thin film 3 containing xBKT-yBMT-zBFO may be a ferroelectric thin film. It is suspected that the ferroelectric properties of the piezoelectric thin film 3 are caused by the composition of xBKT-yBMT-zBFO, which exhibits a morphotropic phase boundary (MPB). Due to the ferroelectric properties, the piezoelectric thin film 3 easily exhibits a large piezoelectric constant (i.e., λ). 33 ). In contrast to the piezoelectric thin film 3, the crystals contained in a bulk material of xBKT-yBMT-zBFO are quasi-cubic crystals, so it is difficult for a bulk material of xBKT-yBMT-zBFO to achieve the crystal orientation and ferroelectric properties described above.

[0043] A composition of xBKT-yBMT-zBFO can be represented on the basis of a three-dimensional coordinate system. The three-dimensional coordinate system is composed, as in Fig. 4, consists of an X-, a Y-, and a Z-axis. Each coordinate in the coordinate system is represented by (X, Y, Z). The coordinates (x, y, z) in the coordinate system correspond to x, y, and z in the chemical formula 1. The sum of x, y, and z in the chemical formula 1 is 1, and each x, y, and z is a positive real number. Accordingly, the coordinates (x, y, z) are located within a triangle drawn by dashed lines in a plane represented by X+Y+Z=1. In other words, the coordinates (x, y, z) lie within a triangle with vertices at the coordinates (1, 0, 0), the coordinates (1, 1, 0), and the coordinates (0, 0, 1). The triangle is in Fig. 5 as triangular coordinates. The coordinates A in Fig.5 are (0.300, 0.100, 0.600). The B coordinates are (0.450, 0.250, 0.300). The C coordinates are (0.200, 0.500, 0.300). The D coordinates are (0.100, 0.300, 0.600). The E coordinates are (0.400, 0.200, 0.400). The F coordinates are (0.200, 0.400, 0.400). Each of the coordinates A, B, C, D, E, and F lies within the plane represented by X+Y+Z=1. The coordinates (x, y, z) referring to x, y, and z in the chemical formula 1 can be positioned within a quadrilateral with the vertices at coordinates A, coordinates B, coordinates C, and coordinates D. In the case where the coordinates (x, y, z) are within the quadrilateral ABCD, the composition of xBKT-yBMT-zBFO slightly exhibits MPB, so that the piezoelectricity and ferroelectric properties of the piezoelectric thin film 3 are easily improved.For the same reason, the coordinates (x, y, z) can be positioned within the quadrilateral with vertices at coordinates A, E, F, and D. x can be equal to y. When x is equal to y, the coordinates (x, y, z) are positioned on a straight line passing through coordinates (0, 500, 0, 500, 0) and (0, 0, 1). When x is equal to y, the composition of xBKT-yBMT-zBFO slightly exhibits MPB, thus slightly improving the piezoelectricity and ferroelectric properties of the piezoelectric thin film 3.

[0044] x can be 0.100 or greater and 0.450 or less; y can be 0.100 or greater and 0.500 or less; and z can be 0.300 or greater and 0.600 or less. x can be 0.100 or greater and 0.400 or less; y can be 0.100 or greater and 0.400 or less; and z can be 0.400 or greater and 0.600 or less. x can be 0.150 or greater and 0.350 or less; y can be 0.150 or greater and 0.350 or less; and z can be 0.300 or greater and 0.600 or less. x can be 0.250 or greater and 0.300 or less; y can be 0.250 or greater and 0.300 or less; and z can be 0.400 or larger and 0.600 or smaller. In the case where x, y, and z are within the above-described range and x+y+z is 1, the composition of xBKT-yBMT-zBFO readily includes MPB, so that the piezoelectricity and ferroelectric properties of the piezoelectric thin film 3 can be easily improved.

[0045] The thickness of the piezoelectric thin film 3 may be, for example, 10 nm or more and 10 µm or less. The area of ​​the piezoelectric thin film 3 may be, for example, 1 µm 2 or more and 500 mm 2 or less. The area of ​​the single-crystal substrate 1, the first intermediate layer 5, the first electrode layer 2, the second intermediate layer 6, and the second electrode layer 4 may each be the same as the area of ​​the piezoelectric thin film 3.

[0046] The composition of the piezoelectric thin film can be analyzed using X-ray fluorescence spectroscopy (XRF) or inductively coupled plasma emission spectroscopy (ICP). The crystal structure and crystal orientation of the piezoelectric thin film can be identified using X-ray diffraction (XRD).

[0047] The piezoelectric thin film 3 can be formed, for example, by the following method.

[0048] As a raw material for the piezoelectric thin film 3, a target having the same composition as the piezoelectric thin film 3 can be used. The method for preparing the target is as follows.

[0049] For example, powders of bismuth oxide, potassium carbonate, titanium oxide, an oxide of element M, and iron oxide can be used as starting materials. The oxide of element M can be at least one of magnesium oxide and nickel oxide. As starting materials, materials that become oxides by sintering, such as carbonates or oxalates, can be used instead of the oxides described above. These starting materials are sufficiently dried at 100°C or more, and then each of the starting materials is weighed so that the number of moles of Bi, K, Ti, an element M, and Fe is within the range prescribed by Chemical Formula 1. In the gas-phase growth process described below, Bi and K in a target are more volatile than other elements. Accordingly, the molar ratio of Bi in the target can be set to a value higher than the molar ratio of Bi in the piezoelectric thin film 3.The molar ratio of K in the target can be set to a value higher than the molar ratio of K in the piezoelectric thin film 3.

[0050] The weighed raw materials are sufficiently mixed in an organic solvent or water. The mixing time can be 5 hours or more and 20 hours or less. The mixing means can be a ball mill. After mixing, the raw materials are sufficiently dried and then shaped by a press machine. The shaped raw materials are calcined to obtain a calcined material. The calcination temperature can be 750°C or more and 900°C or less. The calcination time can be 1 hour or more and 3 hours or less. The calcined material is pulverized in an organic solvent or water. The pulverization time can be 5 hours or more and 30 hours or less. The grinding means can be a ball mill.After drying the calcined and pulverized material, a binder solution is added to the calcined material to be granulated, resulting in a powder of the calcined material. The powder of the calcined material is then molded into a block-shaped product by compression molding.

[0051] The molded product in block form is heated to volatilize the binder in the molded product. The heating temperature can be 400°C or more and 800°C or less. The heating time can be 2 hours or more and 4 hours or less. The molded product is then sintered. The sintering temperature can be 800°C or more and 1100°C or less. The sintering time can be 2 hours or more and 4 hours or less. The temperature rise and fall rate of the molded product during the sintering process can be, for example, 50°C / hour or more and 300°C / hour or less.

[0052] A target is obtained through the steps described above. The average particle diameter of the crystal grains of the metal oxide contained in the target can be, for example, 1 µm or more and 20 µm or less.

[0053] The piezoelectric thin film 3 can be formed by a vapor-phase growth method using the target described above. In the vapor-phase growth method, the elements constituting the target are evaporated under a vacuum atmosphere. The evaporated elements adhere to and deposit on any surface of the second intermediate layer 6, the first electrode layer 2, or the single-crystal substrate 1, thereby growing the piezoelectric thin film 3. The vapor-phase growth method can be, for example, a sputtering method, an electron beam vapor deposition method, a chemical vapor deposition method, or a pulsed laser deposition method. Hereinafter, a pulsed laser deposition method is referred to as a PLD method.The use of these vapor-phase growth methods enables the piezoelectric thin film 3 to be densely formed at the atomic level, while suppressing the segregation of elements in the piezoelectric thin film 3. The excitation source varies depending on the type of vapor-phase growth method. The excitation source of a sputtering process is an Ar plasma. The excitation source of an electron beam vapor deposition process is an electron beam. The excitation source of a PLD process is laser light (e.g., an excimer laser). When a target is exposed to these excitation sources, the elements that comprise the target evaporate.

[0054] Among the vapor-phase growth methods described above, the PLD method is comparatively superior in the following respects. With the PLD method, each of the elements constituting the target can be converted into plasma at the same time without any unevenness. Accordingly, the piezoelectric thin film 3 with approximately the same composition as the target can be easily formed. Furthermore, with the PLD method, the thickness of the piezoelectric thin film 3 can be easily controlled by changing the laser pulse number (repetition frequency).

[0055] The piezoelectric thin film 3 may be an epitaxial layer. In other words, the piezoelectric thin film 3 can be formed by epitaxial growth. A piezoelectric thin film 3 with excellent crystal orientation can be easily formed by epitaxial growth. In the case of forming the piezoelectric thin film 3 by the PLD method, the piezoelectric thin film 3 is easily formed by epitaxial growth.

[0056] In the PLD method, the piezoelectric thin film 3 can be formed by heating the single-crystal substrate 1 and the first electrode layer 2 in a vacuum chamber. The temperature of the single-crystal substrate 1 and the first electrode layer 2 (deposition temperature) can be, for example, 300°C or more and 800°C or less, 500°C or more and 700°C or less, or 500°C or more and 600°C or less. The higher the deposition temperature, the higher the cleanliness of the surface of the single-crystal substrate 1 or the first electrode layer 2, and the crystallinity of the piezoelectric thin film 3 is improved, and the degree of crystal plane orientation is slightly increased. If the deposition temperature is too high, Bi or K is easily dissolved from the piezoelectric thin film 3, so the composition of the piezoelectric thin film 3 is difficult to control.

[0057] In the PLD method, the oxygen partial pressure in a vacuum chamber can be, for example, more than 10 mTorr and less than 400 mTorr, 15 mTorr or more and 300 mTorr or less, or 20 mTorr or more and 200 mTorr or less. In other words, the oxygen partial pressure in a vacuum chamber can be, for example, more than 1 Pa and less than 53 Pa, 2 Pa or more and 40 Pa or less, or 3 Pa or more and 30 Pa or less. When the oxygen partial pressure is maintained in the above-described range, Bi, K, Ti, an element M, and Fe deposited on the single crystal substrate 1 tend to be sufficiently oxidized. When the oxygen partial pressure is too high, the growth rate of the piezoelectric thin film 3 tends to decrease, so that the degree of orientation of the crystal plane of the piezoelectric thin film 3 tends to decrease.

[0058] Examples of parameters other than those mentioned above that are controlled in the PLD method include the laser oscillation frequency and the distance between the substrate and the target. By controlling these parameters, the crystal structure and crystal orientation of the piezoelectric thin film 3 can be easily controlled. For example, when the laser oscillation frequency is 10 Hz or less, the degree of crystal plane orientation of the piezoelectric thin film 3 tends to increase.

[0059] After the piezoelectric thin film 3 is grown, an annealing treatment (heat treatment) of the piezoelectric thin film 3 may be performed. The temperature of the piezoelectric thin film 3 during the annealing treatment (annealing temperature) may be, for example, 300°C or more and 1000°C or less, 600°C or more and 1000°C or less, or 850°C or more and 1000°C or less. By annealing the piezoelectric thin film 3, the piezoelectricity of the piezoelectric thin film 3 tends to be further improved. In particular, by annealing at 850°C or more and 1000°C or less, the piezoelectricity of the piezoelectric thin film 3 can be slightly improved. However, the annealing treatment is not absolutely necessary.

[0060] The single crystal substrate 1 can be, for example, a substrate made of a Si single crystal, or a substrate made of a single crystal of a compound semiconductor such as GaAs. The single crystal substrate 1 can be a substrate made of an oxide single crystal such as MgO or a perovskite-type oxide (e.g., SrTiO3). The thickness of the single crystal substrate 1 can be, for example, 10 µm or more and 1000 µm or less. In the case that the single crystal substrate 1 is conductive, the single crystal substrate 1 functions as an electrode, so the first electrode layer 2 need not be present. The conductive single crystal substrate 1 can be, for example, a niobium (Nb)-doped SrTiO3 single crystal.

[0061] The crystal orientation of the single crystal substrate 1 can be related to the orientation of the surface normal D Nof the single crystal substrate 1. In other words, the surface of the single crystal substrate 1 may be parallel to the crystal plane of the single crystal substrate 1. The single crystal substrate 1 may be a uniformly oriented substrate. For example, a crystal plane selected from the group consisting of the (100) plane, the (001) plane, the (110) plane, the (101) plane, and the (111) plane may be parallel to the surface of the single crystal substrate 1. In other words, an orientation selected from the group consisting of

[100] ,

[001] ,

[110] ,

[101] , and

[111] may be parallel to the surface normal D N of the single crystal substrate 1.

[0062] In the case that the (100) plane of the single crystal substrate 1 (e.g., Si) is parallel to the surface of the single crystal substrate 1, the (001) plane of the perovskite-like crystal in the piezoelectric thin film 3 is slightly oriented in the direction of the surface normal dn of the piezoelectric thin film 3. In the case that the (110) plane of the single crystal substrate 1 is parallel to the surface of the single crystal substrate 1, the (110) plane of the perovskite crystal in the piezoelectric thin film 3 is slightly oriented in the direction of the surface normal dn of the piezoelectric thin film 3. In the case that the (111) plane of the single crystal substrate 1 is parallel to the surface of the single crystal substrate 1, the (111) plane of the perovskite crystal in the piezoelectric thin film 3 is slightly oriented in the direction of the surface normal dn of the piezoelectric thin film 3.

[0063] As described above, the first intermediate layer 5 may be arranged between the single-crystal substrate 1 and the first electrode layer 2. The first intermediate layer 5 may contain at least one component selected from the group consisting of, for example, titanium (Ti), chromium (Cr), titanium oxide (TiO2), silicon oxide (SiO2), and zirconium oxide (ZrO2). By interposing the first intermediate layer 5, the first electrode layer 2 can be easily adhered to the single-crystal substrate 1. The first intermediate layer 5 may be crystalline. The crystal plane of the first intermediate layer 5 may be oriented in the direction of the surface normal D N of the single crystal substrate 1. Both the crystal plane of the single crystal substrate 1 and the crystal plane of the first intermediate layer 5 can be oriented in the direction of the surface normal D Nof the single crystal substrate 1. The method for forming the first intermediate layer 5 may be a sputtering method, a vacuum deposition method, a printing method, a spin coating method, or a sol-gel method.

[0064] The first intermediate layer 5 may contain ZrO2 and a rare earth element oxide. Since the first intermediate layer 5 contains ZrO2 and the rare earth element oxide, the first electrode layer 2 made of platinum crystal is easily formed on the surface of the first intermediate layer 5. The (002) plane of the platinum crystal is slightly oriented toward the surface normal of the first electrode layer 2, and the (200) plane of the platinum crystal is slightly oriented toward the surface plane of the first electrode layer 2. The rare earth element can be at least one element from the group 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).The first intermediate layer 5 may be made of yttria-stabilized zirconia (ZrO2 with Y2O3 added). Due to the first intermediate layer 5 being made of yttria-stabilized zirconia, the first electrode layer 2 made of platinum crystal is easily formed on the surface of the first intermediate layer 5, the (002) plane of the platinum crystal is slightly oriented toward the surface normal of the first electrode layer 2, and the (200) plane of the platinum crystal is slightly oriented toward the surface plane of the first electrode layer 2. For the same reason, the first intermediate layer 5 may include a first layer made of ZrO2 and a second layer made of Y2O3. The first layer may be directly laminated onto the surface of the single-crystal substrate 1, the second layer may be directly laminated onto the surface of the first layer, and the first electrode layer 2 may be directly laminated onto the surface of the second layer.

[0065] The first electrode layer 2 can consist of at least one metal, which is selected, for example, from the group comprising Pt (platinum), Pd (palladium), Rh (rhodium), Au (gold), Ru (ruthenium), Ir (iridium), Mo (molybdenum), Ti (titanium), Ta (tantalum), and Ni (nickel). The first electrode layer 2 can consist, for example, of a conductive metal oxide such as strontium ruthenate (SrRuO3), lanthanum nickelate (LaNiO3), or lanthanum strontium cobaltate ((La,Sr)CoO3). The first electrode layer 2 can be crystalline. The crystal plane of the first electrode layer 2 can be oriented in the direction of the surface normal D N of the single-crystal substrate 1. The crystal plane of the first electrode layer 2 can run approximately parallel to the surface of the single-crystal substrate 1. Both the crystal plane of the single-crystal substrate 1 and the crystal plane of the first electrode layer 2 can be oriented in the direction of the surface normal D Nof the single crystal substrate 1. The crystal plane of the first electrode layer 2 may be approximately parallel to the crystal plane of the perovskite crystal oriented in the piezoelectric thin film 3. The thickness of the first electrode layer 2 may be, for example, 1 nm or more and 1.0 µm or less. The method for forming the first electrode layer 2 may be a sputtering method, a vacuum deposition method, a printing method, a spin coating method, or a sol-gel method. In the printing method, the spin coating method, or the sol-gel method, a heat treatment (annealing) of the first electrode layer 2 may be performed to increase the crystallinity of the first electrode layer 2.

[0066] The first electrode layer 2 may contain a platinum crystal. The first electrode layer 2 may also consist solely of platinum crystal. The platinum crystal is a cubic crystal with a face-centered cubic lattice structure. The (002) plane of the platinum crystal may be oriented in the direction of the surface normal of the first electrode layer 2, and the (200) plane of the platinum crystal may be oriented in the direction of the surface plane of the first electrode layer 2. This means that the (002) plane of the platinum crystal may be approximately parallel to the surface of the first electrode layer 2, and the (200) plane of the platinum crystal may be approximately perpendicular to the surface of the first electrode layer 2.Since the (002) plane and the (200) plane of the platinum crystal constituting the first electrode layer 2 have the orientation described above, the piezoelectric thin film 3 easily grows epitaxially on the surface of the first electrode layer 2. The piezoelectric thin film 3 easily contains the tetragonal crystal of a perovskite-type crystal, and the (001) plane of the tetragonal crystal tends to be preferentially oriented in the direction of the surface normal dn of the piezoelectric thin film 3. The surface of the first electrode layer 2 may be approximately parallel to the surface of the piezoelectric thin film 3. In other words, the direction of the surface normal of the first electrode layer 2 may be approximately parallel to the surface normal dn of the piezoelectric thin film 3.

[0067] As described above, the second intermediate layer 6 may be disposed between the first electrode layer 2 and the piezoelectric thin film 3. The second intermediate layer 6 may, for example, contain at least one of the group consisting of SrRuO3, LaNiO3, and (La,Sr)CoO3. By interposing the second intermediate layer 6, the piezoelectric thin film 3 can be easily adhered to the first electrode layer 2. The second intermediate layer 6 may be crystalline. The crystal plane of the second intermediate layer 6 may be oriented in the direction of the surface normal D N of the single crystal substrate 1. Both the crystal plane of the single crystal substrate 1 and the crystal plane of the second intermediate layer 6 can be oriented in the direction of the surface normal D Nof the single crystal substrate 1. The method for forming the second intermediate layer 6 may be a sputtering method, a vacuum deposition method, a printing method, a spin coating method, or a sol-gel method.

[0068] The second electrode layer 4 may consist of at least one metal selected, for example, from the group consisting of Pt, Pd, Rh, Au, Ru, Ir, Mo, Ti, Ta, and Ni. The second electrode layer 4 may consist of at least one conductive metal oxide selected, for example, from the group consisting of LaNiO3, SrRuO3, and (La, Sr)CoO3. The second electrode layer 4 may be crystalline. The crystal plane of the second electrode layer 4 may be oriented in the direction of the surface normal D. Nof the single crystal substrate 1. The crystal plane of the second electrode layer 4 may be approximately parallel to the surface of the single crystal substrate 1. The crystal plane of the second electrode layer 4 may be approximately parallel to the crystal plane of the perovskite-like crystal oriented in the piezoelectric thin film 3. The thickness of the second electrode layer 4 may be, for example, 1 nm or more and 1.0 µm or less. The method for forming the second electrode layer 4 may be a sputtering method, a vacuum deposition method, a printing method, a spin coating method, or a sol-gel method. In the printing method, the spin coating method, or the sol-gel method, heat treatment (annealing) of the second electrode layer 4 may be performed to increase the crystallinity of the second electrode layer 4.

[0069] A third intermediate layer may be disposed between the piezoelectric thin film 3 and the second electrode layer 4. The interposition of the third intermediate layer allows the second electrode layer 4 to easily adhere to the piezoelectric thin film 3. The composition, crystal structure, and manufacturing method of the third intermediate layer may be the same as those of the second intermediate layer.

[0070] The surface of the piezoelectric thin-film device 10 can be at least partially or completely covered with a protective layer. Covering the surface with a protective layer improves, for example, the moisture resistance of the piezoelectric thin-film device 10.

[0071] The applications of the piezoelectric thin-film device according to the present embodiment are diverse. The piezoelectric thin-film device can be used, for example, for a piezoelectric actuator. The piezoelectric actuator can be used, for example, for a head assembly, a head stack assembly, or a hard disk drive. The piezoelectric actuator can be used, for example, for a print head or an inkjet printer device. The piezoelectric device can be, for example, a piezoelectric transducer. The piezoelectric thin-film device can be used, for example, for a piezoelectric sensor. The piezoelectric sensor can be, for example, a gyro sensor, a pressure sensor, a pulse wave sensor, an ultrasonic sensor, or a shock sensor. The piezoelectric thin-film device can be applied, for example, to a microphone. The piezoelectric thin-film component can be applied to a part of microelectromechanical systems (MEMS). (Piezoelectric actuator)

[0072] Fig. Figure 6 shows a head assembly 200 for installation on a hard disk drive (HDD). The head assembly 200 consists of a base plate 9, a load beam 11, a flexure 17, first and second piezoelectric thin-film devices 100, and a head slider 19. The first and second piezoelectric thin-film devices 100 are drive devices for the head slider 19. The head slider 19 has a head device 19a.

[0073] The load beam 11 includes a base end portion 11b attached to the base plate 9, a first leaf spring portion 11c and a second leaf spring portion 11d extending from the base end portion 11b, an opening 11e formed between the leaf springs 11c and 11d, and a beam main portion 11f extending linearly to the leaf spring portions 11c and 11d. The first leaf spring portion 11c and the second leaf spring portion 11d are tapered. The beam main portion 11f is also tapered.

[0074] The first and second piezoelectric thin-film devices 100 are arranged at a predetermined pitch on a flexible wiring substrate 15 as part of the flexure 17. The head slider 19 is attached to one end of the flexure 17 and rotates with the expansion and contraction of the first and second piezoelectric thin-film devices 100.

[0075] Fig.7 shows a piezoelectric actuator 300 for the print head. The piezoelectric actuator 300 includes a base 20, an insulating layer 23 stacked on the base 20, a single-crystal substrate 14 stacked on the insulating layer 23, a piezoelectric thin film 25 stacked on the single-crystal substrate 14, and an upper electrode layer 26 (second electrode layer) stacked on the piezoelectric thin film 25. The single-crystal substrate 14 is conductive and also functions as a lower electrode layer. The lower electrode layer can be described as the first electrode layer described above. The upper electrode layer can be described as the second electrode layer described above.

[0076] If no specified discharge signal is applied and no electric field is applied between the single-crystal substrate 14 (lower electrode layer) and the upper electrode layer 26, the piezoelectric thin film 25 is not deformed. No pressure change occurs in a pressure chamber 21 adjacent to the piezoelectric thin film 25, to which no discharge signal is applied, so no ink droplet is ejected from a nozzle 27.

[0077] However, when a specified discharge signal is applied and an electric field is applied between the single-crystal substrate 14 (lower electrode layer) and the upper electrode layer 26, the piezoelectric thin film 25 is deformed. Since the insulating layer 23 undergoes a large displacement due to the deformation of the piezoelectric thin film 25, the pressure in the pressure chamber 21 immediately increases, causing an ink droplet to be ejected from the nozzle 27. (pressure sensor)

[0078] Fig. 8 and Fig. 9 shows a gyro sensor 400, which is a type of piezoelectric sensor. The gyro sensor 400 consists of a base 110 and a pair of arms 120 and 130 connected to a surface of the base 110. The pair of arms 120 and 130 constitute a tuning fork oscillator. In other words, the gyro sensor 400 is a tuning fork oscillator-type device for detecting angular velocity. The gyro sensor 400 is formed into a tuning fork-type oscillator by processing a piezoelectric thin film 30, an upper electrode layer 31, and a single-crystal substrate 32, which are included in the above-described piezoelectric thin film device. The base 110 and the arms 120 and 130 are integrated into the piezoelectric thin film device. The single crystal substrate 32 is conductive and simultaneously functions as the lower electrode layer.

[0079] The drive electrode layers 31a and 31b and a detection electrode layer 31d are formed on a first main surface of an arm 120. Similarly, the drive electrode layers 31a and 31b and a detection electrode layer 31c are formed on a first main surface of another arm 130. Each of the electrode layers 31a, 31b, 31c, and 31d is obtained by etching the upper electrode layer 31 into a specific electrode shape.

[0080] The single-crystal substrate 32 (lower electrode layer) is formed on the entire second main surface (back surface of the first main surface) of the base 110 and the arms 120 and 130. The single-crystal substrate 32 (lower electrode layer) serves as the ground electrode of the gyro sensor 400.

[0081] The longitudinal direction of each of the arms 120 and 130 is defined as the Z direction, and the plane including the major surfaces of the arms 120 and 130 is defined as the XZ plane, defining a rectangular XYZ coordinate system.

[0082] When a drive signal is applied to the drive electrode layers 31a and 31b, the two arms 120 and 130 are excited to an in-plane vibration state. The in-plane vibration state is a state in which the two arms 120 and 130 are excited in the direction parallel to the main surfaces of the two arms 120 and 130. For example, if one arm 120 is excited at a velocity V1 in the minus X direction, another arm 130 is excited at a velocity V2 in the plus X direction.

[0083] In such a state, when the gyro sensor 400 is caused to rotate at an angular velocity ω around the Z-axis as the rotation axis, a Coriolis force acts on each of the arms 120 and 130 in the direction perpendicular to the velocity direction. As a result, the arms 120 and 130 begin to be excited in an out-of-plane vibration state. The out-of-plane vibration state is a state in which the two arms 120 and 130 are excited in the direction orthogonal to the main surfaces of the two arms 120 and 130. For example, if a Coriolis force F1 acting on one arm 120 occurs in the minus Y direction, a Coriolis force F2 acting on another arm 130 occurs in the plus Y direction.

[0084] Since the magnitude of the Coriolis forces F1 and F2 is proportional to the angular velocity ω, the mechanical distortion of the arms 120 and 130 caused by the Coriolis forces F1 and F2 is converted by the piezoelectric thin film 30 into electrical signals (detection signals), which are obtained for detecting the angular velocity ω via the detection electrode layers 31c and 31d.

[0085] Fig.10 shows a pressure sensor 500, which is a type of piezoelectric sensor. The pressure sensor 500 includes a piezoelectric thin-film device 40, a support 44 supporting the piezoelectric thin-film device 40, a current amplifier 46, and a voltmeter 47. The piezoelectric thin-film device 40 consists of a common electrode layer 41, a piezoelectric thin-film 42 stacked on the common electrode layer 41, and a single electrode layer 43 stacked on the piezoelectric thin-film 42. The common electrode layer 41 is a conductive single-crystal substrate. A cavity 45 surrounded by the common electrode layer 41 and the support 44 responds to pressure. When an external force is applied to the pressure sensor 500, the piezoelectric thin film device 40 undergoes a deflection and a voltage is detected by the voltmeter 47.

[0086] Fig.11 shows a pulse wave sensor 600, which is a type of piezoelectric sensor. The pulse wave sensor 600 includes a piezoelectric thin-film device 50, a support 54 supporting the piezoelectric thin-film device 50, and a voltmeter 55. The piezoelectric thin-film device 50 consists of a common electrode layer 51, a piezoelectric thin-film layer 52 stacked on the common electrode layer 51, and a single electrode layer 53 stacked on the piezoelectric thin-film layer 52. The common electrode layer 51 is a conductive single-crystal substrate.When the back surface of the substrate 54 of the pulse wave sensor 600 (surface on which no piezoelectric thin film device 50 is installed) is brought into contact with an artery of a living body, the substrate 54 and the piezoelectric thin film device 50 undergo a displacement due to the pressure of the pulse of the living body, and a voltage is detected by the voltmeter 55. (hard disk drive)

[0087] Fig. 12 shows a hard disk drive 700 in which the Fig. 6 shown head assembly is installed. A head assembly 65 in Fig. 12 is the same as the head assembly 200 in Fig. 6.

[0088] The hard disk drive 700 consists of a housing 60, a hard disk 61 (recording medium) disposed within the housing 60, and a head stack assembly 62. The hard disk 61 is rotated by a motor. The head stack assembly 62 records magnetic data onto the hard disk 61 or reproduces the magnetic data recorded on the hard disk 61.

[0089] The head stack assembly 62 includes a voice coil motor 63, an actuator arm 64 mounted on a spindle, and a head assembly 65 connected to the actuator arm 64. The actuator arm 64 is freely rotated around the spindle by the voice coil motor 63. The actuator arm 64 is branched into multiple arms, and the head assembly 65 is connected to each of the arms. In other words, a plurality of arms and head assemblies 65 are stacked along the spindle. A head slider 19 is mounted at the end of the head assembly 65 opposite the hard disk 61.

[0090] The head assembly 65 (200) allows a head device 19a to be moved in two steps. A relatively large movement of the head device 19a is controlled by the overall drive of the head assembly 65 and the actuator arm 64 by the voice coil motor 63. A micromovement of the head device 19a is controlled by the drive of the head carriage 19 positioned at the end of the head assembly 65. (inkjet printer)

[0091] Fig. 13 shows an inkjet printer 800. The inkjet printer 800 consists of a print head 70, a main body 71, a tray 72 and a head drive mechanism 73. The print head 70 in Fig. 13 has the piezoelectric actuator 300 from Fig. 7.

[0092] The inkjet printer 800 consists of ink cartridges with a total of four colors: yellow, magenta, cyan, and black. Full-color printing is possible with the inkjet printer 800. A dedicated control board or the like is installed inside the inkjet printer 800. The dedicated control board or the like controls the timing of ink ejection from the print head 70 and the scanning of the head drive mechanism 73. A tray 72 is located on the back of the main body 71, and an automatic cut-sheet feeder (automatic continuous paper feed mechanism) 76 is located at one end of the tray 72. The automatic sheet feeder 76 automatically feeds a sheet 75 to be printed and ejects it from a front outlet 74. [Examples]

[0093] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the examples. (Example 1)

[0094] A Si single-crystal substrate was used to fabricate a piezoelectric thin-film device in Example 1. The (100) plane of Si was parallel to the surface of the single-crystal substrate. The single-crystal substrate had a square shape with dimensions of 20 mm × 20 mm. The thickness of the single-crystal substrate was 500 µm.

[0095] In a vacuum chamber, a crystalline first interlayer consisting of ZrO2 and Y2O3 was formed over the entire surface of the single-crystal substrate. The first interlayer was formed by a sputtering process. The thickness of the first interlayer was 30 nm.

[0096] In a vacuum chamber, a first electrode layer made of Pt crystal was formed over the entire surface of the first intermediate layer. The first electrode layer was formed by a sputtering process. The thickness of the first electrode layer was 200 nm. The temperature of the single-crystal substrate (deposition temperature) was maintained at 500°C during the formation of the first electrode layer.

[0097] An X-ray diffraction (XRD) pattern of the first electrode layer was measured by measuring the out-of-plane surface of the first electrode layer. Another XRD pattern of the first electrode layer was measured by measuring the in-plane surface of the first electrode layer. An X-ray diffractometer (SmartLab) from Rigaku Corporation was used to measure these XRD patterns. The measurement conditions were adjusted so that the diffraction peak intensities in the XRD pattern were at least three orders of magnitude larger than the background intensity. An X-ray diffraction peak of the (002) plane of the Pt crystal was detected by the out-of-plane measurement. In other words, the (002) plane of the Pt crystal was oriented in the direction of the surface normal of the first electrode layer. An X-ray diffraction peak of the (200) plane of the Pt crystal was detected by the in-plane measurement.That is, the (200) plane of the Pt crystal was oriented towards the surface of the first electrode layer.

[0098] A piezoelectric thin film was formed in a vacuum chamber over the entire surface of the first electrode layer. The piezoelectric thin film was fabricated using a PLD method. The thickness of the piezoelectric thin film was 2000 nm. The temperature of the single-crystal substrate (deposition temperature) was maintained at 500°C during the formation of the piezoelectric thin film. The oxygen partial pressure in the vacuum chamber during the formation of the piezoelectric thin film was maintained at 10 Pa. A target (sintered material made from raw material powder) was used as the starting material for the piezoelectric thin film. During the preparation of the target, the mixing ratio of the raw material powder (bismuth oxide, potassium carbonate, titanium oxide, magnesium oxide, and iron oxide) was adjusted to the intended composition of the piezoelectric thin film.The intended composition of the piezoelectric thin film was represented by the chemical formula 1A described below. The values ​​of x, y, and z from the chemical formula 1A are shown below in Table 1. xBi 0,5 K 0,5 TiO3-yBiMg 0,5 Ti 0,5 O3-zBiFeO3 (1A)

[0099] The composition of the piezoelectric thin film was analyzed using X-ray fluorescence spectroscopy (XRF method). A PW2404 instrument manufactured by Philips Japan, Ltd. was used for the analysis. As a result of the analysis, the composition of the piezoelectric thin film in Example 1 was represented by Chemical Formula 1A, and the values ​​of x, y, and z in Chemical Formula 1A were as shown below in Table 1. In other words, the composition of the piezoelectric thin film approximately matched the composition of the target.

[0100] An XRD pattern of the piezoelectric thin film was measured by measuring the out-of-plane surface of the piezoelectric thin film. Another XRD pattern of the piezoelectric thin film was measured by measuring the in-plane surface of the piezoelectric thin film. The measurement apparatus and measurement conditions of the XRD patterns were the same as those described above.

[0101] The XRD pattern of the piezoelectric thin film showed that the piezoelectric thin film is composed of a perovskite-like crystal. The X-ray diffraction reflections of the (001) plane of the perovskite-like crystal were detected by out-of-plane measurement. In other words, the (001) plane of the perovskite-like crystal was oriented in the direction of the surface normal of the piezoelectric thin film. The orientation degree of the (001) plane of the perovskite-like crystal was calculated based on the XRD pattern. The orientation degree of the (001) plane is expressed as 100×I. (001) / IΣ (hkl) The details of the definition of the orientation degree are as described above. The orientation degree of the (001) plane in Example 1 is shown in Table 1 below.

[0102] The lattice constant c of the perovskite-like crystal in the direction normal to the surface of the piezoelectric thin film was determined by out-of-plane measurement. The lattice constant c is described as the distance between the crystal planes parallel to the surface of the piezoelectric thin film. The lattice constants a and b of the perovskite-like crystal in the direction parallel to the surface of the piezoelectric thin film were determined by in-plane measurement. The lattice constants a and b are described as the distance between the crystal planes perpendicular to the surface of the piezoelectric thin film. The lattice constants a and b were approximately equal. Each of a and b was smaller than c. In other words, the perovskite-like crystal contained in the piezoelectric thin film was a tetragonal crystal.

[0103] By the method described above, a laminate was manufactured comprising a single-crystal substrate, a first intermediate layer stacked on the single-crystal substrate, a first electrode layer stacked on the first intermediate layer, and a piezoelectric thin film stacked on the first electrode layer. The following laminate-forming step was further performed.

[0104] A second electrode layer made of Pt was formed over the entire surface of the piezoelectric thin film in a vacuum chamber. The second electrode layer was formed by a sputtering method. The temperature of the single-crystal substrate was maintained at 500°C during the formation of the second electrode layer. The thickness of the second electrode layer was 200 nm.

[0105] Through the steps described above, a laminate was fabricated, comprising a single-crystal substrate, a first intermediate layer stacked on the single-crystal substrate, a first electrode layer stacked on the first intermediate layer, a piezoelectric thin film stacked on the first electrode layer, and a second electrode layer stacked on the piezoelectric thin film. In subsequent photolithography, the laminate structure was patterned on the single-crystal substrate. After patterning, the laminate was dicing.

[0106] Through the above-described steps, a strip-shaped piezoelectric thin-film device was obtained in Example 1. The piezoelectric thin-film device consisted of a single-crystal substrate, a first intermediate layer stacked on the single-crystal substrate, a first electrode layer stacked on the first intermediate layer, a piezoelectric thin film stacked on the first electrode layer, and a second electrode layer stacked on the piezoelectric thin film. The area of ​​a movable part of the piezoelectric thin film was 20 mm × 1.0 mm. [Measurement of the piezoelectric constant d 33,f ]

[0107] The piezoelectric constant d 33,fThe piezoelectric thin film was measured on the piezoelectric thin film device from Example 1. For the measurement, an apparatus with an atomic force microscope (AFM) and a ferroelectric material evaluation system was used. The atomic force microscope was an SPA-400 from Seiko Instruments Inc., and the ferroelectric material evaluation system was the FCE from TOYO Corporation. The frequency of the alternating electric field (AC voltage) used to measure the piezoelectric constant d 33,f was 5 Hz. The maximum value of the voltage applied to the piezoelectric thin film was 20 V. The unit of d 33,f is pm / V. The piezoelectric constant d 33,f from Example 1 is shown in the following Table 1. (Examples 2 to 18 and comparative examples 1 to 3)

[0108] A piezoelectric thin film device of each of Examples 2 to 18 and Comparative Examples 1 to 3 was manufactured in the same manner as in Example 1 except that the composition of the target used for forming the piezoelectric thin film was different.

[0109] An XRD image of the first electrode layer of Examples 2 to 18 was measured in the same manner as in Example 1. In each case of Examples 2 to 18, the (002) plane of the Pt crystal constituting the first electrode layer was oriented in the direction of the surface normal of the first electrode layer, and the (200) plane of the Pt crystal was oriented in the direction inside the surface of the first electrode layer.

[0110] The composition of the piezoelectric thin film of Examples 2 to 18 and Comparative Examples 1 to 3 was analyzed in the same manner as in Example 1. In all cases of Examples 2 to 18 and Comparative Examples 1 to 3, the composition of the piezoelectric thin film was approximately the same as the composition of the target. The composition of the piezoelectric thin film (x, y, and z values, respectively) of Examples 2 to 18 and Comparative Examples 1 to 3 is shown in Table 1 below. x, y, and z of Examples 2 to 16 and 18 are shown as coordinates (x, y, z) in Fig. 5 (triangular coordinates). The coordinates A in Fig. 5 correspond to Example 1. The coordinates B in Fig. 5 correspond to Example 2. The coordinates C in Fig. 5 correspond to example 3. The coordinates D in Fig. 5 correspond to example 4. The coordinates E in Fig.5 correspond to Example 5. The coordinates F in Fig. 5 correspond to example 6.

[0111] XRD patterns of the piezoelectric thin films of Examples 2 to 18 and Comparative Examples 1 to 3 were measured in the same manner as in Example 1. Each of the XRD images of Examples 2 to 18 and Comparative Examples 1 to 3 showed that the piezoelectric thin film was composed of a perovskite-like crystal. In all cases of Examples 2 to 18 and Comparative Examples 1 to 3, the (001) plane of the perovskite-like crystal was oriented in the surface normal direction of the piezoelectric thin film. In all cases of Examples 2 to 18, the perovskite-like crystal contained in the piezoelectric thin film was a tetragonal crystal. The degree of orientation of the (001) plane of Examples 2 to 18 and Comparative Examples 1 to 3 is shown in Table 1 below.

[0112] The piezoelectric constant d 33, f of the piezoelectric thin film of Examples 2 to 18 and Comparative Examples 1 to 3 was measured in the same manner as in Example 1. The piezoelectric constant d 33, f of Examples 2 to 18 and Comparative Examples 1 to 3 is shown in Table 1 below. [Table 1] Table 1 Piezoelectric thin film d 33,f x y z Orientation level Degree of orientation [%] Example 1 0,300 0,100 0,600 (001) Level 99 92 Example 2 0,450 0,250 0,300 (001) Level 99 81 Example 3 0,200 0,500 0,300 (001) Level 99 84 Example 4 0,100 0,300 0,600 (001) Level 99 91 Example 5 0,400 0,200 0,400 (001) Level 99 95 Example 6 0,200 0,400 0,400 (001) Level 99 94 Example 7 0,350 0,150 0,500 (001) Level 99 88 Example 8 0,150 0,350 0,500 (001) Level 99 93 Example 9 0,250 0,250 0,500 (001) Level 99 110 Example 10 0,200 0,200 0,600 (001) Level 99 104 Example 11 0,300 0,300 0,400 (001) Level 99 98 Example 12 0,350 0,350 0,300 (001) Level 99 87 Example 13 0,450 0,150 0,400 (001) Level 99 76 Example 14 0,150 0,450 0,400 (001) Level 99 73 Example 15 0,350 0,050 0,600 (001) Level 99 78 Example 16 0,050 0,350 0,600 (001) Level 99 75 Example 17 0,325 0,325 0,350 (001) Level 99 72 Example 18 0,375 0,375 0,250 (001) Level 99 74 Comparison example 1 0,500 0,000 0,500 (001) Level 99 48 Comparison example 2 0,800 0,200 0,000 (001) Level 99 32 Comparison example 3 0,000 0,500 0,500 (001) Level 99 20 (Examples 20 and 21 and Comparative Example 4)

[0113] The oxygen partial pressure in a vacuum chamber during the formation of the piezoelectric thin film of Example 20 was maintained at 1 Pa.

[0114] The oxygen partial pressure in a vacuum chamber during the formation of the piezoelectric thin film of Example 21 was maintained at 20 Pa.

[0115] The oxygen partial pressure in a vacuum chamber during the formation of the piezoelectric thin film of Comparative Example 4 was maintained at 0.1 Pa.

[0116] A piezoelectric thin film device of Examples 20 and 21 and Comparative Example 4 was fabricated in the same manner as Example 9 except for the oxygen partial pressure during the formation of the piezoelectric thin film.

[0117] An XRD image of the first electrode layer of Examples 20 and 21 and Comparative Example 4 was measured in the same manner as in Example 1. In each case of Examples 20 and 21 and Comparative Example 4, the (002) plane of the Pt crystal constituting the first electrode layer was oriented in the direction of the surface normal of the first electrode layer, and the (200) plane of the Pt crystal was oriented in the direction within the plane of the surface of the first electrode layer.

[0118] The composition of the piezoelectric thin film of Examples 20 and 21 and Comparative Example 4 was analyzed in the same manner as in Example 1. In all cases of Examples 20 and 21 and Comparative Example 4, the composition of the piezoelectric thin film was approximately consistent with the composition of the target. The composition of the piezoelectric thin film (x, y, and z values, respectively) of Examples 20 and 21 and Comparative Example 4 is shown in Table 2 below.

[0119] The XRD images of the piezoelectric thin film of Examples 20 and 21 and Comparative Example 4 were measured in the same manner as in Example 1. Each of the XRD images of Examples 20 and 21 and Comparative Example 4 showed that the piezoelectric thin film was composed of a perovskite-like crystal.

[0120] In the case of Example 20, the (110) plane of the perovskite-like crystal was oriented in the direction of the surface normal of the piezoelectric thin film.

[0121] In the case of Example 21, the (111) plane of the perovskite-like crystal was oriented in the direction of the surface normal of the piezoelectric thin film.

[0122] In Comparative Example 4, the specific crystal plane of the perovskite-like crystal was not oriented in the direction of the surface normal of the piezoelectric thin film. In other words, in Comparative Example 4, the degree of orientation of one of the crystal planes was less than 50%.

[0123] Based on the XRD image, the orientation degree of the (110) plane of the perovskite-like crystal from Example 20 was calculated. The orientation degree of the (110) plane is given by 100×I (110) / IΣ (hkl)The detailed definition of the degree of orientation is as described above. The degree of orientation of the (110) plane from Example 20 is shown in Table 2 below.

[0124] Based on the XRD image, the orientation degree of the (111) plane of the perovskite-like crystal from Example 21 was calculated. The orientation degree of the (111) plane is given by 100×I (111) / IΣ (hkl) The detailed definition of the degree of orientation is as described above. The degree of orientation of the (111) plane of Example 21 is shown in Table 2 below.

[0125] A piezoelectric constant d 33, f of the piezoelectric thin film of Examples 20 and 21 and Comparative Example 4 was measured in the same manner as in Example 1. The piezoelectric constant d 33, f of Examples 20 and 21 and Comparative Example 4 is shown in Table 2 below. [Table 2] Table 2 Piezoelectric thin film d 33,f x y z Oriented plane Degree of orientation [%] Example 9 0,250 0,250 0,500 (001) Level 99 110 Example 20 0,250 0,250 0,500 (110) Level 83 76 Example 21 0,250 0,250 0,500 (111) Level 95 85 Comparison example 4 0,250 0,250 0,500 No - 37 (Examples 22 and 23)

[0126] In Examples 22 and 23, a second intermediate layer was formed on the entire surface of the first electrode layer, and a piezoelectric thin film was formed on the entire surface of the second intermediate layer. The second intermediate layer of Example 22 was made of crystalline SrRuO3. The thickness of the second intermediate layer of Example 22 was 50 nm. The second intermediate layer of Example 23 was made of crystalline LaNiO3. The thickness of the second intermediate layer of Example 23 was 50 nm.

[0127] A piezoelectric thin film device of Examples 22 and 23 was fabricated in the same manner as in Example 9 except for the formation of the second intermediate layer.

[0128] An XRD image of the first electrode layer of Examples 22 and 23 was measured in the same manner as in Example 1. In each case of Examples 22 and 23, the (002) plane of the Pt crystal constituting the first electrode layer was oriented in the direction of the surface normal of the first electrode layer, and the (200) plane of the Pt crystal was oriented toward the surface of the first electrode layer.

[0129] The composition of the piezoelectric thin film of Examples 22 and 23 was analyzed in the same manner as in Example 1. In both cases of Examples 22 and 23, the composition of the piezoelectric thin film was approximately consistent with the composition of the target. The composition of the piezoelectric thin film (x, y, and z values, respectively) of Examples 22 and 23 is shown in Table 3 below.

[0130] XRD images of the piezoelectric thin films of Examples 22 and 23 were measured in the same manner as in Example 1. Each of the XRD images of Examples 22 and 23 indicated that the piezoelectric thin film was composed of a perovskite-like crystal. In all cases of Examples 22 and 23, the (001) plane of the perovskite-like crystal was oriented in the direction of the surface normal of the piezoelectric thin film. In all cases of Examples 22 and 23, the perovskite-like crystal contained in the piezoelectric thin film was a tetragonal crystal.

[0131] A piezoelectric constant d 33,f of the piezoelectric thin film of Examples 22 and 23 was measured in the same manner as in Example 1. The piezoelectric constant d 33,f of Examples 22 and 23 is shown in Table 3 below. [Table 3] Table 3 Piezoelectric thin film Second intermediate layer d 33,f x y z Oriented plane Degree of orientation [%] Example 9 0,250 0,250 0,500 (001) Level 99 absent 110 Example 22 0,250 0,250 0,500 (001) Level 99 SrRuO3 106 Example 23 0,250 0,250 0,500 (001) Level 99 LaNiO3 108 (Examples 24 to 26)

[0132] In the fabrication of a piezoelectric thin-film device of Example 24, no first intermediate layer was formed. A first electrode layer composed of crystalline SrRuO3 was directly formed on the entire surface of a single-crystal substrate in the step of fabricating the piezoelectric thin-film device of Example 24. The thickness of the first electrode layer of Example 24 was 200 nm. The piezoelectric thin-film device of Example 24 was fabricated in the same manner as Example 9 except for these points.

[0133] In the fabrication of a piezoelectric thin-film device of Example 25, no first intermediate layer was formed. A first electrode layer consisting of crystalline SrRuO3 was directly formed on the entire surface of a single-crystal substrate during the fabrication of a piezoelectric thin-film device of Example 25. The thickness of the first electrode layer of Example 25 was 200 nm. The piezoelectric thin-film device of Example 25 was fabricated in the same manner as Example 20 except for these points.

[0134] In the fabrication of a piezoelectric thin-film device of Example 26, no first intermediate layer was formed. A first electrode layer consisting of crystalline SrRuO3 was directly formed on the entire surface of a single-crystal substrate during the fabrication of a piezoelectric thin-film device of Example 26. The thickness of the first electrode layer of Example 26 was 200 nm. The piezoelectric thin-film device of Example 26 was fabricated in the same manner as Example 21 except for these points.

[0135] An XRD image of the first electrode layer of Examples 24 to 26 was measured in the same manner as in Example 1. In all cases of Examples 24 to 26, the crystal plane of the first electrode layer was not oriented toward the surface of the first electrode layer. In other words, in all cases of Examples 24 to 26, the crystal plane of the first electrode layer lacked in-plane orientation.

[0136] The composition of the piezoelectric thin film of Examples 24 to 26 was analyzed in the same manner as in Example 1. In all cases of Examples 24 to 26, the composition of the piezoelectric thin film was approximately consistent with the composition of the target. The composition of the piezoelectric thin film (x, y, and z values, respectively) of Examples 24 to 26 is shown in Table 4 below.

[0137] XRD images of the piezoelectric thin film of Examples 24 to 26 were measured in the same manner as in Example 1. Each of the XRD images of Examples 24 to 26 showed that the piezoelectric thin film was composed of a perovskite-like crystal.

[0138] In the case of Example 24, the (001) plane of the perovskite-like crystal was oriented in the direction of the surface normal of the piezoelectric thin film. The degree of orientation of the (001) plane in Example 24 is shown in Table 4 below.

[0139] In the case of Example 25, the (110) plane of the perovskite-like crystal was oriented in the direction of the surface normal of the piezoelectric thin film. The degree of orientation of the (110) plane in Example 25 is shown in Table 4 below.

[0140] In the case of Example 26, the (111) plane of the perovskite-like crystal was oriented in the direction of the surface normal of the piezoelectric thin film. The degree of orientation of the (111) plane in Example 26 is shown in Table 4 below.

[0141] A piezoelectric constant d 33,f of the piezoelectric thin film of Examples 24 to 26 was measured in the same manner as in Example 1. The piezoelectric constant d 33,f of Examples 24 to 26 is shown in Table 4 below. [Table 4] Table 4 Piezoelectric thin film First electrode layer d 33,f x y z Oriented plane Degree of orientation [%] Orientation in the plane Example 9 0,250 0,250 0,500 (001) Level 99 available 110 Example 20 0,250 0,250 0,500 (110) Level 85 available 76 Example 21 0,250 0,250 0,500 (111) Level 95 available 85 Example 24 0,250 0,250 0,500 (001) Level 91 absent 98 Example 25 0,250 0,250 0,500 (110) Level 81 absent 72 Example 26 0,250 0,250 0,500 (111) Level 89 absent 81 (Examples 27 to 29)

[0142] When preparing the target of Example 27, the mixing ratio of the raw material powder (bismuth oxide, potassium carbonate, titanium oxide, magnesium oxide, nickel oxide, and iron oxide) was adjusted to the intended composition of the piezoelectric thin film. The intended composition of the piezoelectric thin film is represented by the chemical formula 1B described below. The values ​​of x, y, z, and y in the following formula corresponded to the values ​​shown in Table 5 below. xBi 0,5 K 0,5 TiO3-yBi(Mg γ No 1-γ ) 0,5 Ti 0,5 O3-zBiFeO3 (1B)

[0143] A piezoelectric thin film device of Example 27 was fabricated in the same manner as in Example 1 except that the composition of the target used for forming the piezoelectric thin film was different.

[0144] In the case of Example 28, y in Chemical Formula 1B was 1 / 3. In the case of Example 29, y in Chemical Formula 1B was 0. In other words, in the case of Example 29, no magnesium oxide was used in the raw material powder of the target. The piezoelectric thin-film devices of Examples 28 and 29 were fabricated in the same manner as Examples 27, except for y.

[0145] In Examples 27 to 29, an XRD image of the first electrode layer was measured in the same manner as in Example 1. In each case of Examples 27 to 29, the (002) plane of the Pt crystal constituting the first electrode layer was oriented in the direction of the surface normal of the first electrode layer, and the (200) plane of the Pt crystal was oriented toward the surface of the first electrode layer.

[0146] The composition of the piezoelectric thin film of Examples 27 to 29 was analyzed in the same manner as in Example 1. In all cases of Examples 27 to 29, the composition of the piezoelectric thin film was approximately consistent with the composition of the target. The composition of the piezoelectric thin film of Examples 27 to 29 (values ​​of x, y, z, and γ, respectively) is shown in Table 5 below.

[0147] XRD images of the piezoelectric thin film of Examples 27 to 29 were measured in the same manner as in Example 1. Each of the XRD images of Examples 27 to 29 indicated that the piezoelectric thin film was composed of a perovskite-like crystal. In all cases of Examples 27 to 29, the (001) plane of the perovskite-like crystal was oriented in the direction of the surface normal of the piezoelectric thin film. In all cases of Examples 27 to 29, the perovskite-like crystal contained in the piezoelectric thin film was a tetragonal crystal. The degree of orientation of the (001) plane of each of Examples 27 to 29 is shown in Table 5 below.

[0148] A piezoelectric constant d 33,f of the piezoelectric thin film of Examples 27 to 29 was measured in the same manner as in Example 1. The piezoelectric constant d 33,f of Examples 27 to 29 is shown in Table 5 below.

[0154] [Table 5] Table 5 x y z γ Oriented plane Degree of orientation [%] d 33,f Example 27 0,250 0,250 0,500 0,500 (001) Level 99 100 Example 28 0,250 0,250 0,500 1 / 3 (001) Level 99 96 Example 29 0,250 0,250 0,500 0,000 (001) Level 99 89

[0155] [Industrial Applicability]

[0149] The piezoelectric thin film according to the present invention is used, for example, in a piezoelectric actuator and a piezoelectric sensor.

[0156] [Reference character list] 10, 40, 50 and 100: PIEZOELECTRIC THIN FILM DEVICE, 1 single crystal substrate, 2 FIRST ELECTRODE LAYER, 3, 25, 30, 42 and 52 PIEZOELECTRIC THIN FILM, 4 SECOND ELECTRODE LAYER, 5 FIRST INTERMEDIATE LAYER, 6 SECOND INTERMEDIATE LAYER, D N DIRECTION OF THE SURFACE NORMAL OF THE SINGLE CRYSTAL SUBSTRATE, dn DIRECTION OF THE SURFACE NORMAL OF THE PIEZOELECTRIC THIN FILM, uc UNIT CELL OF THE PEROVSKITE STRUCTURE, a DISTANCE BETWEEN (100)-PLANES OF THE UNIT CELL, b DISTANCE BETWEEN (010) PLANES OF THE UNIT CELL, c DISTANCE BETWEEN (001) PLANES OF THE UNIT CELL, 200 HEAD ARRANGEMENT, 9 BASE PLATE, 11 LOAD BEAMS, 11b BASE END SECTION, 11c FIRST LEAF SPRING PART, 11d SECOND LEAF SPRING PART, 11th OPENING, 11f Main beam section, 15 FLEXIBLE WIRING SUBSTRATE, 17 BENDING ELEMENT, 19 HEAD SLIDES, 19a HEAD DEVICE, 300 PIEZOELECTRIC ACTUATOR, 20 BASE, 21 PRESSURE CHAMBER, 23 INSULATION LAYER, 24 SINGLE CRYSTAL SUBSTRATE, 26 UPPER ELECTRODE LAYER (FIRST ELECTRODE LAYER), 27 NOZZLE, 400 GYRO SENSOR, 110 BASE, 120 and 130 ARMS, 31 UPPER ELECTRODE LAYER (FIRST ELECTRODE LAYER), 31a and 31b DRIVE ELECTRODE LAYERS, 31c and 31d detection electrode layers, 32 SINGLE CRYSTAL SUBSTRATE, 500 PRESSURE SENSOR, 41 COMMON ELECTRODE LAYER, 43 SINGLE ELECTRODE LAYER, 44 CARRIER, 45 CAVITY, 46 CURRENT AMPLIFIERS, 47 VOLTMETER, 600 PULSE WAVE SENSOR, 51 COMMON ELECTRODE LAYER, 53 SINGLE ELECTRODE LAYER, 54 CARRIER, 55 VOLTMETER, 700 HARD DRIVE, 60 HOUSINGS, 61 HARD DRIVE, 62 HEADSTACK ARRANGEMENT, 63 Voice coil motor, 64 ACTUATOR ARM, 65 HEAD ARRANGEMENT, 800 inkjet printers, 70 PRINT HEAD, 71 MAIN BODY, 72 TIMES, 73 HEAD DRIVE MECHANISM, 74 OUTLET, 75 SHEETS TO BE PRINTED, 76 AUTOMATIC SHEET FEED (AUTOMATIC CONTINUOUS PAPER FEED MECHANISM).

Claims

[1] Piezoelectric thin film containing a metal oxide of perovskite-like crystals, wherein the metal oxide contains bismuth, potassium, titanium, iron and the element M; the element M is at least one of the elements magnesium and nickel; all perovskite-like crystals in the piezoelectric thin film are tetragonal crystals with perovskite structure; and a (001) plane of the tetragonal crystals is oriented in the direction of the surface normal of the piezoelectric thin film, where the metal oxide has the chemical formula x(Bi α K 1-α )TiO3-yBi(M β Ti 1-β )O3-zBiFeO3, where each of x, y and z is a positive real number; x+y+z = 1; α is greater than 0 and less than 1; β is greater than 0 and less than 1; M by Mg γ No 1-γ is presented; and γ is 0 or greater and 1 or less. [2] Piezoelectric thin film according to claim 1, wherein a three-dimensional coordinate system is composed of an X-axis, a Y-axis and a Z-axis; any coordinates in the coordinate system are represented by (X, Y, Z); the coordinates (x, y, z) in the coordinate system correspond to x, y and z in x(Bi α K 1-α )TiO3-yBi(M β Ti 1-β )O3-zBiFeO3; The coordinates A in the coordinate system are (0.300, 0.100, 0.600), The coordinates B in the coordinate system are (0.450, 0.250, 0.300), The coordinates C in the coordinate system are (0.200, 0.500, 0.300), the coordinates D in the coordinate system are (0.100, 0.300, 0.600), and (x, y, z) are positioned within a quadrilateral with vertices at coordinates A, coordinates B, coordinates C and coordinates D. [3] Piezoelectric thin film according to claim 2, where the coordinates E are in the coordinate system (0.400, 0.200, 0.400), the coordinates F in the coordinate system are (0.200, 0.400, 0.400), and the coordinates (x, y, z) are positioned within a quadrilateral with the vertices at coordinates A, coordinates E, coordinates F and coordinates D. [4] The piezoelectric thin film according to any one of claims 1 to 3, wherein the piezoelectric thin film is an epitaxial film. [5] The piezoelectric thin film according to any one of claims 1 to 4, wherein the piezoelectric thin film is a ferroelectric thin film. [6] A piezoelectric thin film device comprising: the piezoelectric thin film according to any one of claims 1 to 5. [7] Piezoelectric thin film device according to claim 6, comprising: a single crystal substrate and the piezoelectric thin film stacked on the single crystal substrate. [8] Piezoelectric thin film device according to claim 6, comprising: a single crystal substrate; an electrode layer stacked on the single crystal substrate; and the piezoelectric thin film stacked on the electrode layer. [9] Piezoelectric thin film device according to claim 6, comprising: an electrode layer and the piezoelectric thin film stacked on the electrode layer. [10] A piezoelectric thin film device according to claim 8, further comprising: at least one intermediate layer, wherein the intermediate layer is arranged between the single crystal substrate and the electrode layer. [11] A piezoelectric thin film device according to claim 8 or 10, further comprising: at least one intermediate layer, wherein the intermediate layer is arranged between the electrode layer and the piezoelectric thin film. [12] Piezoelectric thin-film device according to one of claims 8 to 11, wherein the electrode layer contains a platinum crystal, a (002) plane of the platinum crystal is oriented in the direction of the surface normal of the electrode layer and a (200) plane of the platinum crystal is oriented in the plane towards the surface of the electrode layer. [13] Piezoelectric actuator, comprising: the piezoelectric thin film device according to any one of claims 6 to 12. [14] Piezoelectric sensor, comprising: the piezoelectric thin film device according to any one of claims 6 to 12. [15] Piezoelectric transducer, comprising: the piezoelectric thin film device according to any one of claims 6 to 12. [16] Hard disk drive having a head stack assembly, wherein the head stack assembly comprises a head assembly, and the head assembly comprises the piezoelectric actuator according to claim 13. [17] Print head comprising: the piezoelectric actuator according to claim 13. [18] Inkjet printer, comprising: the printhead according to claim 13.

Images