JPWO2017111090A1 - Piezoelectric thin film, piezoelectric thin film element, piezoelectric actuator, piezoelectric sensor, head assembly, head stack assembly, hard disk drive, printer head, and inkjet printer apparatus - Google Patents

Abstract

A piezoelectric thin film having a large d31 and g31 is provided. The piezoelectric thin film 3 overlaps the single crystal substrate 1. The piezoelectric thin film 3 contains a crystalline oxide represented by the following chemical formula 1. One of the plane orientations of the oxide selected from the group consisting of (100), (001), (110), (101) and (111) is preferentially oriented in the normal direction DN of the single crystal substrate 1. Yes. (BixKy) TiO3 (1) [in the above chemical formula 1, 0.30 ≦ x ≦ 0.60, 0.30 ≦ y ≦ 0.60, 0.60 ≦ x + y ≦ 1.10. ]

Description

  The present invention relates to a piezoelectric thin film, a piezoelectric thin film element, a piezoelectric actuator, a piezoelectric sensor, a head assembly, a head stack assembly, a hard disk drive, a printer head, and an ink jet printer apparatus.

  Piezoelectric materials are processed into various piezoelectric thin film elements according to various purposes. For example, a piezoelectric actuator converts a voltage into a force by an inverse piezoelectric effect that applies a voltage to the piezoelectric thin film to deform the piezoelectric thin film. The piezoelectric sensor converts force into voltage by a piezoelectric effect that applies pressure to the piezoelectric thin film to deform the piezoelectric thin film. These piezoelectric thin film elements are mounted on various electronic devices.

Conventionally, lead zirconate titanate (so-called PZT), which is a perovskite ferroelectric, has been widely used as a piezoelectric material. However, since PZT contains lead that harms the human body and the environment, development of lead-free piezoelectric materials is expected as an alternative to PZT. For example, Non-Patent Document 1 describes a BaTiO ₃ -based material as an example of a lead-free piezoelectric material. The BaTiO ₃ -based material has excellent piezoelectric characteristics compared to other lead-free piezoelectric materials, and is particularly expected to be applied to piezoelectric thin film elements.

High-Performance Lead-Free Barium Titanate Piezoelectric Ceramics, Advances in Science and Technology, Vol. 54, pp. 7-12, Sep. 2008

However, the relative dielectric constant εr of the BaTiO ₃ material is high. Therefore, even if the piezoelectric constant d ₃₁ of the BaTiO ₃ material is comparable to PZT, the piezoelectric constant g ₃₁ of the BaTiO ₃ material obtained by dividing d ₃₁ by εr becomes small. A large d ₃₁ is required for a piezoelectric actuator, for example, and a large g ₃₁ is required for a piezoelectric sensor, for example, but for various applications of piezoelectric thin film elements, both g ₃₁ and d ₃₁ are A large piezoelectric thin film is required.

The present invention has been made in view of the above-described problems of the prior art. A piezoelectric thin film having a large d ₃₁ and g ₃₁ , a piezoelectric thin film element, a piezoelectric actuator using the piezoelectric thin film element, a piezoelectric sensor, a head assembly, It is an object to provide a head stack assembly, a hard disk drive, a printer head, and an inkjet printer apparatus.

A piezoelectric thin film according to one aspect of the present invention is a piezoelectric thin film overlying a single crystal substrate, and the piezoelectric thin film includes a crystalline oxide represented by the following chemical formula 1, and (100), (001), ( 110), (101), and (111), one of the plane orientations of the oxide selected from the group consisting of (111) is preferentially oriented in the normal direction of the single crystal substrate. The plane orientation of the oxide may be restated as the orientation of the crystal plane of the oxide represented by the following chemical formula 1.
_{(Bi x K y) TiO 3} (1)
[In the above chemical formula 1, 0.30 ≦ x ≦ 0.60, 0.30 ≦ y ≦ 0.60, 0.60 ≦ x + y ≦ 1.10. ]

A piezoelectric thin film element according to one aspect of the present invention includes a single crystal substrate and a piezoelectric thin film overlapping the single crystal substrate, and the piezoelectric thin film includes a crystalline oxide represented by the following chemical formula 1, (100 ), (001), (110), (101), and one of the plane orientations of the oxide selected from the group consisting of (111) is preferentially oriented in the normal direction of the single crystal substrate.
_{(Bi x K y) TiO 3} (1)
[In the above chemical formula 1, 0.30 ≦ x ≦ 0.60, 0.30 ≦ y ≦ 0.60, 0.60 ≦ x + y ≦ 1.10. ]

  The plane orientation preferentially oriented in the normal direction may be (001).

  A piezoelectric actuator according to one aspect of the present invention includes the piezoelectric thin film element.

  A piezoelectric sensor according to one aspect of the present invention includes the piezoelectric thin film element.

  A head assembly according to one aspect of the present invention includes the piezoelectric actuator.

  A head stack assembly according to one aspect of the present invention includes the head assembly.

  A hard disk drive according to one aspect of the present invention includes the head stack assembly.

  A printer head according to one aspect of the present invention includes the piezoelectric actuator.

  An ink jet printer apparatus according to one aspect of the present invention includes the printer head.

According to the present invention, a piezoelectric thin film having a large d ₃₁ and g ₃₁ , a piezoelectric thin film element, and a piezoelectric actuator, a piezoelectric sensor, a head assembly, a head stack assembly, a hard disk drive, a printer head, and an inkjet printer using the piezoelectric thin film element An apparatus is provided.

1A is a schematic view of a piezoelectric thin film element according to an embodiment of the present invention, and FIG. 1B is a perspective exploded view of the piezoelectric thin film element shown in FIG. It is a figure (In (b) in FIG. 1, a 1st electrode layer and a 2nd electrode layer are abbreviate | omitted). It is a schematic diagram of the head assembly which concerns on one Embodiment of this invention. It is a schematic diagram of the piezoelectric actuator which concerns on one Embodiment of this invention. It is a schematic diagram (plan view) of a gyro sensor according to an embodiment of the present invention. It is arrow sectional drawing along the AA line of the gyro sensor shown in FIG. It is a mimetic diagram of a pressure sensor concerning one embodiment of the present invention. It is a mimetic diagram of a pulse wave sensor concerning one embodiment of the present invention. 1 is a schematic diagram of a hard disk drive according to an embodiment of the present invention. 1 is a schematic diagram of an ink jet printer apparatus according to an embodiment of the present invention. It is an X-ray diffraction pattern of the piezoelectric thin film of Example 6 of the present invention. It is the plot of the molar ratio x of Bi and the molar ratio y of K in the piezoelectric thin film of each of the Example and comparative example of this invention.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the drawings. In the drawings, the same or equivalent elements are denoted by the same reference numerals. X, Y, and Z shown in FIG. 1 mean three coordinate axes that are orthogonal to each other. Further, when the description overlaps, the description is omitted. The present invention is not limited to the following embodiment.

(Piezoelectric thin film and piezoelectric thin film element)
As shown in FIG. 1, a piezoelectric thin film element 100 according to this embodiment includes a single crystal substrate 1, a first electrode layer 2 (lower electrode layer) that overlaps the single crystal substrate 1, and a first electrode layer 2. A piezoelectric thin film 3 overlapping the single crystal substrate 1 and a second electrode layer 4 (upper electrode layer) overlapping the piezoelectric thin film 3 are provided. That is, in the piezoelectric thin film element 100, the piezoelectric thin film 3 is sandwiched between a pair of electrode layers. The modification of the piezoelectric thin film element 100 may not include the second electrode layer 4. For example, after a piezoelectric thin film element without a second electrode layer is supplied as a product to a manufacturer of an electronic device, the second electrode layer is added to the piezoelectric thin film element in the process of assembling and manufacturing the electronic device. Good.

The single crystal substrate 1 may be, for example, a substrate made of a single crystal of Si or a substrate made of a single crystal of a compound semiconductor such as GaAs. The single crystal substrate 1 may be a substrate made of a single crystal of an oxide such as MgO or a perovskite oxide (for example, SrTiO ₃ ). The thickness of the single crystal substrate 1 may be, for example, 10 to 1000 μm. When the single crystal substrate 1 has conductivity, the first electrode layer 2 may be omitted because the single crystal substrate 1 functions as an electrode. That is, when the single crystal substrate 1 has conductivity, the piezoelectric thin film 3 may directly overlap the single crystal substrate 1. The single crystal substrate 1 having conductivity may be, for example, a single crystal of SrTiO ₃ doped with Nb (niobium). When the single crystal substrate 1 is a single crystal of Si, an adhesion layer made of Ti, Cr, or the like may be formed on the surface of the single crystal substrate 1 in order to improve the adhesion of the first electrode layer 2.

One of the plane orientation of the crystal structure of the single crystal substrate 1 may be equal to the normal direction D _N of the single crystal substrate 1. That is, any crystal plane of the crystal structure of the single crystal substrate 1 may be oriented in the normal direction D _N of the single crystal substrate 1. The single crystal substrate 1 may be a uniaxially oriented substrate. For example, one of the plane orientations of the crystal structure of the single crystal substrate 1 selected from the group consisting of (100), (001), (110), (101), and (111) is the normal direction D of the single crystal substrate. _N may be equal.

The first electrode layer 2 includes, for example, Pt (platinum), Pd (palladium), Rh (rhodium), Au (gold), Ru (ruthenium), Ir (iridium), Mo (molybdenum), Ti (titanium), Ta (Tantalum) and at least one metal selected from the group consisting of Ni (nickel) may be used. The first electrode layer 2 may be made of a conductive metal oxide such as SrRuO ₃ or LaNiO ₃ , for example. The first electrode layer 2 may be crystalline. One of the plane orientation of the crystal structure of the first electrode layer 2 may have oriented in the normal direction D _N of the single crystal substrate 1. And the plane orientation of the single crystal substrate 1, and the plane orientation of the crystal structure of the first electrode layer 2, both may be oriented in the normal direction D _N of the single crystal substrate 1. The plane orientation of the crystal structure of the first electrode layer 2 to be oriented in the normal direction D _N may be the same as the plane orientation of the single crystal substrate 1 for alignment in the normal direction D _N. The thickness of the first electrode layer 2 may be 1 nm to 1.0 μm, for example. The formation method of the first electrode layer 2 may be a sputtering method, a vacuum evaporation 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, the first electrode layer 2 may be heated to increase the crystallinity of the first electrode layer 2.

The piezoelectric thin film 3 contains a crystalline oxide represented by the following chemical formula 1 as a main component. The main component means a component having a ratio of 99% mol or more to all components constituting the piezoelectric thin film 3. Hereinafter, the oxide represented by the following chemical formula 1 is referred to as “oxide BKT”. The piezoelectric thin film 3 may consist only of the crystalline oxide BKT. Crystalline oxide BKT has a perovskite structure. The crystalline oxide BKT may be tetragonal at room temperature.
_{(Bi x K y) TiO 3} (1)
[In the above chemical formula 1, 0.30 ≦ x ≦ 0.60, 0.30 ≦ y ≦ 0.60, 0.60 ≦ x + y ≦ 1.10. ]

(100), (001), (110), (101) and one of the plane orientation of the oxide BKT crystalline selected from the group consisting of (111), priority in the normal direction _{D N} single crystal substrate 1 Oriented. Due to the preferential orientation of the plane orientation of the crystalline oxide BKT, the d ₃₁ and g ₃₁ of the piezoelectric thin film 3 become large. The entire oxide BKT or piezoelectric thin film 3 may be a single crystal. The oxide BKT or the entire piezoelectric thin film 3 may be polycrystalline.

Presence / absence of the preferential orientation of the surface orientation of the oxide BKT is determined by the orientation degree of the surface orientation of the oxide BKT. The degree of orientation is expressed as F (HKL). The orientation degree F (HKL) may be rephrased as the orientation degree of the plane orientation (HKL) of the oxide BKT. The degree of orientation F (HKL) may be restated as the degree of orientation of the (HKL) plane of the oxide BKT. The plane orientation (HKL) means any plane orientation selected from the group consisting of (100), (001), (110), (101) and (111). The degree of orientation F (HKL) is a value defined by the Lotgering method. The unit of the degree of orientation F (HKL) is [%]. The orientation degree F (HKL) is defined by the following formula A.
F (HKL) = {(ρ−ρ ₀ ) / (1−ρ ₀ )} × 100 (A)
ρ = ΣI _(HKL) / ΣI _(hkl)
ρ ₀ = ΣI _{0 (HKL)} / ΣI _{0 (hkl)}
ΣI (hkl) is the sum of X-ray diffraction intensities (measured values) of all crystal planes (hkl) of the crystalline oxide BKT.
ΣI (HKL) is the sum of X-ray diffraction intensities (measured values) of a specific crystal plane (HKL) that is crystallographically equivalent in the crystalline oxide BKT. For example, the equivalent crystal plane is each (M00) plane. Here, M is an integer of 1 or more.
ΣI ₀ (hkl) is the total sum of X-ray diffraction intensities (measured values) of all crystal planes (hkl) of (Bi _0.5 K _0.5 ) TiO ₃ having no orientation.
ΣI ₀ (HKL) is the sum of X-ray diffraction intensities of specific crystal planes (HKL) that are crystallographically equivalent in non-oriented (Bi _0.5 K _0.5 ) TiO ₃ . Of the degree of orientation of the orientation of each oxide BKT crystalline, if the orientation of the plane orientation that matches the normal direction D _N of the single crystal substrate 1 is 100% or less than 80%, the plane orientation (HKL ) are oriented preferentially in the direction normal D _N of the single crystal substrate 1. In particular, if a 100% orientation degree F (HKL), the plane orientation (HKL) is completely oriented in the normal direction _{D N} of the single crystal substrate 1. If the degree of orientation F (HKL) is 0.0%, the orientation of the plane orientation of the oxide BKT in the normal direction _{D N} single crystal substrate 1 (HKL) is not. In the normal direction _{D N} single crystal substrate 1, orientation degree F of the plane orientation of the oxide BKT (HKL) (HKL) may be 80 to 98%.
When measuring the X-ray diffraction pattern of the piezoelectric thin film element 100 for the calculation of the orientation degree F (HKL), the temperature of the piezoelectric thin film element 100 may be less than the Curie point of the oxide BKT (for example, room temperature).

D according to (b) of FIG. 1 (HKL) is the orientation of (HKL) plane of the oxide BKT are oriented preferentially in the direction normal _{D N} of the single crystal substrate 1. As shown in (b) of FIG. 1, the plane direction D (HKL) may be parallel to the normal direction _{D N} of the single crystal substrate _1. Plane orientation D (HKL) may be the same as the normal direction _{D N.} Plane orientation D are oriented preferentially in the normal direction _{D N} (HKL) is preferably a (001). The oxide BKT has a tetragonal structure at room temperature, and the plane orientation of the spontaneous polarization direction of the oxide BKT is (001). When the plane orientation of the spontaneous polarization directions are aligned preferentially in the normal direction D _N single crystal substrate 1, it tends piezoelectric d constant (d ₃₁₎ is large and the relative dielectric constant εr is also reduced easily, The piezoelectric g constant (g ₃₁ ) obtained by dividing d ₃₁ by εr tends to be large. When the plane orientation D are oriented preferentially in the normal direction D _N (HKL) is (001), the orientation of the crystal plane of the single crystal substrate 1 for alignment in the normal direction D _N of the single crystal substrate 1 (001).

When the normal direction _DN of the single crystal substrate 1 is the same as the plane orientation (001) of the single crystal substrate 1, the plane orientation D (HKL) of the oxide BKT may be (100) or (001). . When the normal direction _DN of the single crystal substrate 1 is the same as the plane orientation (110) of the single crystal substrate 1, the plane orientation D (HKL) of the oxide BKT may be (110) or (101). When the normal direction _DN of the single crystal substrate 1 is the same as the plane orientation (111) of the single crystal substrate 1, the plane orientation D (HKL) of the oxide BKT may be (111).

As described in Chemical Formula 1, the molar ratio x of Bi (bismuth) in the oxide BKT is 0.30 to 0.60, and the molar ratio y of K (potassium) in the oxide BKT is 0.30 to 0.00. 60, and (x + y) is 0.60 to 1.10. When at least one of x, y and (x + y) is out of the above range, a different phase other than the oxide BKT (for example, a Bi layered compound or a Ti compound) is generated in the process of forming the piezoelectric thin film 3. As a result, the orientation degree of the plane orientation of the oxide BKT is lowered, and the piezoelectric characteristics of the piezoelectric thin film are rapidly deteriorated. x may be 0.50 to 0.60, and y may be 0.50 to 0.60. When x is 0.50 to 0.60 and y is 0.50 to 0.60, the orientation degree of the surface orientation of the oxide BKT tends to be high, d ₃₁ is likely to be large, and εr is small. G ₃₁ tends to be large. x may be 0.45 to 0.55, and y may be 0.45 to 0.55.

The thickness of the piezoelectric thin film 3 may be about 10 nm to 10 μm, for example. The area of the piezoelectric thin film 3 may be, for example, 1 μm ^{2 to} 500 mm ² . The areas of the single crystal substrate 1, the first electrode layer 2, and the second electrode layer 4 may be the same as the area of the piezoelectric thin film 3.

The Curie point of the conventional BaTiO ₃ system material is low. Therefore, when the piezoelectric thin film is heated in the manufacturing process of an electronic device using the piezoelectric thin film element (for example, solder reflow process), the phase transition of the BaTiO ₃ material constituting the piezoelectric thin film is likely to occur, and the mechanical strength and piezoelectricity are increased. Properties are easily lost. On the other hand, the Curie point of the oxide BKT is higher than that of the conventional BaTiO ₃ material. Therefore, in the manufacturing process of the electronic apparatus using the piezoelectric thin film element 100 according to this embodiment, even if the piezoelectric thin film 3 is heated, the phase transition of the oxide BKT hardly occurs, and the mechanical strength and the piezoelectric characteristics are impaired. hard. The Curie point of the oxide BKT may be, for example, about 250 to 400 ° C.

  The piezoelectric thin film 3 may be formed by the following method, for example.

  A BKT target is used to form the piezoelectric thin film 3. The BKT target is a target made of the oxide BKT. The method for producing the BKT target is as follows.

  As starting materials, for example, raw material powders of bismuth oxide, potassium carbonate, and titanium oxide are prepared. After these starting materials are sufficiently dried at 100 ° C. or higher, the number of moles of Bi, the number of moles of K, and the number of moles of Ti are within the range defined by the above chemical formula 1 in the composition analysis after film formation. And weigh each starting material. As a starting material, instead of the above oxide, a substance that becomes an oxide by firing, such as carbonate or oxalate, may be used.

  The weighed starting materials are sufficiently mixed in an organic solvent or water for 5 to 20 hours using, for example, a ball mill or the like. The starting material after mixing is sufficiently dried and then molded with a press. The formed starting material is calcined at 750 to 900 ° C. for about 1 to 3 hours. Subsequently, the calcined product is pulverized in an organic solvent or water for 5 to 30 hours using a ball mill or the like. The pulverized calcined product is dried again, and a binder solution is added and granulated to obtain a calcined product powder. This powder is press-molded to obtain a block-shaped molded body.

  The block-shaped molded body is heated at 400 to 800 ° C. for about 2 to 4 hours to volatilize the binder. Subsequently, the molded body is fired at 800 to 1100 ° C. for about 2 to 4 hours. What is necessary is just to adjust the temperature increase rate and temperature decrease rate of this molded object at the time of this baking to about 50-300 degreeC / hour, for example.

  A BKT target is obtained by the above process. The average particle diameter of the crystal grains of the oxide BKT contained in the BKT target may be, for example, about 1 to 20 μm.

  The piezoelectric thin film 3 may be formed by a vapor phase growth method using the BKT target. In the vapor phase growth method, elements constituting the BKT target are evaporated in a vacuum atmosphere. The evaporated element is deposited and deposited on the surface of the smooth first electrode layer 2 or the surface of the single crystal substrate 1 to grow the piezoelectric thin film 3. The vapor phase growth method may be, for example, a sputtering method, an electron beam evaporation method, a chemical vapor deposition method, or a pulsed laser deposition method. Hereinafter, the pulse laser deposition method is referred to as a PLD method. By using these vapor phase growth methods, a dense film can be formed at the atomic level, and segregation or the like hardly occurs. The excitation source differs depending on the type of vapor phase growth method. The excitation source of the sputtering method is Ar plasma. The excitation source of the electron beam evaporation method is an electron beam. The excitation source of the PLD method is laser light (for example, excimer laser). When these excitation sources are irradiated to the BKT target, the elements constituting the BKT target are evaporated.

  Among the above vapor phase growth methods, the PLD method is relatively superior in the following points. In the PLD method, each element constituting the BKT target can be converted into plasma instantly and without spots by a pulse laser. Therefore, it is easy to form the piezoelectric thin film 3 having almost the same composition as the BKT target. In the PLD method, the thickness of the piezoelectric thin film 3 can be easily controlled by changing the number of pulses (repetition frequency) of the laser.

  In the PLD method, the piezoelectric thin film 3 is formed while heating the single crystal substrate 1 and the first electrode layer 2 in a vacuum chamber. The temperature (film formation temperature) of the single crystal substrate 1 and the first electrode layer 2 may be, for example, 300 to 800 ° C, 500 to 700 ° C, or 500 to 600 ° C. The higher the film formation temperature, the better the cleanliness of the surface of the single crystal substrate 1 or the first electrode layer 2, the higher the crystallinity of the piezoelectric thin film 3, and the degree of orientation of the plane direction of the piezoelectric thin film 3 (oxide BKT). Easy to rise. When the film forming temperature is too high, Bi or K is easily detached from the piezoelectric thin film 3, and the composition of the piezoelectric thin film 3 is difficult to control.

  In the PLD method, the oxygen partial pressure in the vacuum chamber may be, for example, greater than 10 mTorr and less than 400 mTorr, 15 to 300 mTorr, or 20 to 200 mTorr. In other words, the oxygen partial pressure in the vacuum chamber may be, for example, greater than 1 Pa and less than 53 Pa, 2-40 Pa, or 3-30 Pa. By maintaining the oxygen partial pressure within the above range, Bi, K and Ti deposited on the surface of the single crystal substrate 1 or the first electrode layer 2 can be easily oxidized. When the oxygen partial pressure is too high, the growth rate and the degree of orientation of the piezoelectric thin film 3 tend to decrease.

  Other parameters controlled by the PLD method are, for example, the laser oscillation frequency and the distance between the substrate and the target. By controlling these parameters, desired piezoelectric characteristics of the piezoelectric thin film 3 can be easily obtained. For example, when the laser oscillation frequency is 10 Hz or less, the orientation degree of the plane orientation of the piezoelectric thin film 3 is likely to increase.

The second electrode layer 4 may be made of, for example, at least one metal selected from the group consisting of Pt, Pd, Rh, Au, Ru, Ir, Mo, Ti, Ta, and Ni. The second electrode layer 4 may be made of a conductive metal oxide such as SrRuO ₃ or LaNiO ₃ , for example. The second electrode layer 4 may be crystalline. The crystal orientation of the crystal structure of the second electrode layer 4 may be the same as the crystal orientation of the crystal structure of the single crystal substrate 1. The orientation of the plane orientation of the crystal structure of the second electrode layer 4 may be the same as the orientation of the plane orientation of the crystal structure of the oxide BKT. The thickness of the second electrode layer 4 may be, for example, 1 nm to 1.0 μm. The formation method of the second electrode layer 4 may be a sputtering method, a vacuum evaporation 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, the first electrode layer 2 may be heated to increase the crystallinity of the first electrode layer 2.

A first intermediate layer may be interposed between the first electrode layer 2 and the piezoelectric thin film 3. The material constituting the first intermediate layer may be at least one selected from the group consisting of SrRuO ₃ and LaNiO ₃ , for example. The first intermediate layer may be crystalline. One of the plane orientation of the crystal structure of the first intermediate layer may have oriented in the normal direction D _N of the single crystal substrate 1. And the plane orientation of the single crystal substrate 1, and the plane orientation of the crystal structure of the first intermediate layer, both, may be oriented in the normal direction D _N of the single crystal substrate 1. The plane orientation of the crystal structure of the first intermediate layer to orient in the normal direction D _N may be the same as the plane orientation of the single crystal substrate 1 for alignment in the normal direction D _N.

A second intermediate layer may be interposed between the piezoelectric thin film 3 and the second electrode layer 4. The material constituting the second intermediate layer may be the same as the material constituting the first intermediate layer. The second intermediate layer may be crystalline. One of the plane orientation of the crystal structure of the second intermediate layer may have oriented in the normal direction D _N of the single crystal substrate 1. And the plane orientation of the single crystal substrate 1, and the plane orientation of the crystal structure of the second intermediate layer, both, may be oriented in the normal direction D _N of the single crystal substrate 1. Plane orientation of the crystal structure of the second intermediate layer to orient in the normal direction D _N may be the same as the plane orientation of the single crystal substrate 1 for alignment in the normal direction D _N.

  At least part or all of the surface of the piezoelectric thin film element 100 may be covered with a protective film. By covering with the protective film, for example, the moisture resistance of the piezoelectric thin film element 100 is improved.

According to the above-described embodiment, the piezoelectric thin film 3 and the piezoelectric thin film element 100 are provided with large d ₃₁ and g ₃₁ . Applications of the piezoelectric thin film element 100 having a large d ₃₁ and g ₃₁ are diverse. The piezoelectric thin film element 100 may be used for a piezoelectric actuator, for example. The piezoelectric actuator may be used, for example, in a head assembly, a head stack assembly, or a hard disk drive. The piezoelectric actuator may be used in, for example, a printer head or an ink jet printer apparatus. The piezoelectric thin film element 100 may be used for a piezoelectric sensor, for example. The piezoelectric sensor may be, for example, a gyro sensor, a pressure sensor, a pulse wave sensor, or a shock sensor. In particular, in the gyro sensor, the piezoelectric thin film 3 and the piezoelectric thin film element 100 are required in order that both d ₃₁ and g ₃₁ are large. The piezoelectric thin film 3 and the piezoelectric thin film element 100 may be applied to a microphone, for example.

  Below, the specific example of the use of the piezoelectric thin film 3 and the piezoelectric thin film element 100 is demonstrated in detail.

(Piezoelectric actuator)
FIG. 2 shows a head assembly 200 mounted on a hard disk drive (HDD). The head assembly 200 includes a base plate 9, a load beam 11, a flexure 17, first and second piezoelectric thin film elements 100, and a head slider 19. The first and second piezoelectric thin film elements 100 are drive elements for the head slider 19. The head slider 19 has a head element 19a.

  The load beam 11 includes a base end portion 11b fixed to the base plate 9, a first plate spring portion 11c and a second plate spring portion 11d extending from the base end portion 11b, and plate spring portions 11c and 11d. An opening portion 11e formed therebetween and a beam main portion 11f extending linearly continuously from the leaf spring portions 11c and 11d are provided. The first leaf spring portion 11c and the second leaf spring portion 11d are tapered. The beam main part 11f is also tapered.

  The first and second piezoelectric thin film elements 100 are arranged on the wiring flexible substrate 15 which is a part of the flexure 17 with a predetermined interval. The head slider 19 is fixed to the tip of the flexure 17 and rotates as the first and second piezoelectric thin film elements 100 expand and contract.

  FIG. 3 shows a piezoelectric actuator 300 for a printer head. The piezoelectric actuator 300 includes a base 20, an insulating film 23 overlapping the base 20, a single crystal substrate 24 overlapping the insulating film 23, a piezoelectric thin film 25 overlapping the single crystal substrate 24, and an upper electrode layer 26 ( A second electrode layer). The single crystal substrate 24 has conductivity and also functions as a lower electrode layer. The lower electrode layer may be rephrased as the first electrode layer. The upper electrode layer may be rephrased as the second electrode layer.

  When a predetermined ejection signal is not supplied and an electric field is not applied between the single crystal substrate 24 (lower electrode layer) and the upper electrode layer 26, the piezoelectric thin film 25 is not deformed. In the pressure chamber 21 adjacent to the piezoelectric thin film 25 to which no discharge signal is supplied, no pressure change occurs and no ink droplet is discharged from the nozzle 27.

  On the other hand, when a predetermined discharge signal is supplied and a constant electric field is applied between the single crystal substrate 24 (lower electrode layer) and the upper electrode layer 26, the piezoelectric thin film 25 is deformed. Since the insulating film 23 is greatly deflected by the deformation of the piezoelectric thin film 25, the pressure in the pressure chamber 21 is instantaneously increased, and an ink droplet is ejected from the nozzle 27.

(Piezoelectric sensor)
4 and 5 show a gyro sensor 400 which is a kind of piezoelectric sensor. The gyro sensor 400 includes a base 110 and a pair of arms 120 and 130 connected to one surface of the base 110. The pair of arms 120 and 130 are tuning fork vibrators. That is, the gyro sensor 400 is a tuning fork vibrator type angular velocity detection element. The gyro sensor 400 is obtained by processing the piezoelectric thin film 30, the upper electrode layer 31, and the single crystal substrate 32 constituting the above-described piezoelectric thin film element into the shape of a tuning fork vibrator. The base 110 and the arms 120 and 130 are integrated with the piezoelectric thin film element. The single crystal substrate 32 has conductivity and also functions as a lower electrode layer.

  Drive electrode layers 31 a and 31 b and a detection electrode layer 31 d are formed on the first main surface of one arm 120. Similarly, drive electrode layers 31 a and 31 b and a detection electrode layer 31 c are formed on the first main surface of the other arm 130. Each electrode layer 31a, 31b, 31c, 31d is obtained by processing the upper electrode layer 31 into a predetermined electrode shape by etching.

  Single-crystal substrate 32 (lower electrode layer) is formed on the entire base 110 and second main surfaces (back surfaces of the first main surfaces) of arms 120 and 130. The single crystal substrate 32 (lower electrode layer) functions as a ground electrode of the gyro sensor 400.

  The longitudinal directions of the arms 120 and 130 are defined as the Z direction, and the plane including the main surfaces of the arms 120 and 130 is defined as the XZ plane, thereby defining the XYZ orthogonal coordinate system.

  When a drive signal is supplied to the drive electrode layers 31a and 31b, the two arms 120 and 130 are excited in the in-plane vibration mode. The in-plane vibration mode is a mode in which the two arms 120 and 130 are excited in a direction parallel to the main surfaces of the two arms 120 and 130. For example, when one arm 120 is excited at the speed V1 in the −X direction, the other arm 130 is excited at the speed V2 in the + X direction.

In this state, when the gyro sensor 400 is rotated at an angular velocity ω with the Z axis as the rotation axis, a Coriolis force acts on each of the arms 120 and 130 in a direction perpendicular to the velocity direction. As a result, the arms 120 and 130 start to be excited in the out-of-plane vibration mode. The out-of-plane vibration mode is a mode in which the two arms 120 and 130 are excited in a direction orthogonal to the main surfaces of the two arms 120 and 130. For example, when the Coriolis force F1 acting on one arm 120 is in the −Y direction, the Coriolis force F2 acting on the other arm 130 is in the + Y direction.

  Since the magnitude of the Coriolis forces F1 and F2 is proportional to the angular velocity ω, mechanical distortion of the arms 120 and 130 caused by the Coriolis forces F1 and F2 is converted into an electric signal (detection signal) by the piezoelectric thin film 30, and this is detected. By taking out from the electrode layers 31c and 31d, the angular velocity ω is obtained.

  FIG. 6 shows a pressure sensor 500 which is a kind of piezoelectric sensor. The pressure sensor 500 includes a piezoelectric thin film element 40, a support 44 that supports the piezoelectric thin film element 40, a current amplifier 46, and a voltage measuring instrument 47. The piezoelectric thin film element 40 includes a common electrode layer 41, a piezoelectric thin film 42 overlapping the common electrode layer 41, and an individual electrode layer 43 overlapping 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 corresponds to pressure. When an external force is applied to the pressure sensor 500, the piezoelectric thin film element 40 bends, and the voltage is detected by the voltage measuring device 47.

  FIG. 7 shows a pulse wave sensor 600 which is a kind of piezoelectric sensor. The pulse wave sensor 600 includes a piezoelectric thin film element 50, a support 54 that supports the piezoelectric thin film element 50, and a voltage measuring device 55. The piezoelectric thin film element 50 includes a common electrode layer 51, a piezoelectric thin film 52 that overlaps the common electrode layer 51, and an individual electrode layer 53 that overlaps the piezoelectric thin film 52. The common electrode layer 51 is a conductive single crystal substrate. When the back surface (the surface on which the piezoelectric thin film element 50 is not mounted) of the support body 54 of the pulse wave sensor 600 is brought into contact with the living artery, the support body 54 and the piezoelectric thin film element 50 are bent by the pressure of the living body pulse. The voltage is detected by the voltage measuring device 55.

(Hard disk drive)
FIG. 8 shows a hard disk drive 700 on which the head assembly shown in FIG. 2 is mounted. The head assembly 65 in FIG. 8 is the same as the head assembly 200 in FIG.

  The hard disk drive 700 includes a housing 60, a hard disk 61 (recording medium) installed in 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 information on the hard disk 61 and reproduces magnetic information recorded on the hard disk 61.

  The head stack assembly 62 includes a voice coil motor 63, an actuator arm 64 supported by a support shaft, and a head assembly 65 connected to the actuator arm 64. The actuator arm 64 is rotatable around the support shaft by the voice coil motor 63. The actuator arm 64 is divided into a plurality of arms, and a head assembly 65 is connected to each arm. That is, the plurality of arms and the head assembly 65 are stacked along the support shaft. A head slider 19 is attached to the tip of the head assembly 65 so as to face the hard disk 61.

  The head assembly 65 (200) varies the head element 19a in two steps. The relatively large movement of the head element 19 a is controlled by the entire drive of the head assembly 65 and the actuator arm 64 by the voice coil motor 63. The minute movement of the head element 19 a is controlled by driving the head slider 19 located at the tip of the head assembly 65.

(Inkjet printer device)
FIG. 9 shows an inkjet printer device 800. The ink jet printer apparatus 800 includes a printer head 70, a main body 71, a tray 72, and a head driving mechanism 73. The printer head 70 in FIG. 9 has the piezoelectric actuator 300 in FIG.

  The ink jet printer apparatus 800 includes ink cartridges of a total of four colors, yellow, magenta, cyan, and black. Full color printing by the ink jet printer apparatus 800 is possible. A dedicated controller board or the like is mounted inside the ink jet printer apparatus 800. The controller board or the like controls ink ejection timing by the printer head 70 and scanning of the head driving mechanism 73. A tray 72 is provided on the back surface of the main body 71, and an auto sheet feeder (automatic continuous paper feed mechanism) 76 is provided on one end side of the tray 72. The auto sheet feeder 76 automatically feeds the recording paper 75 and discharges the recording paper 75 from the front discharge port 74.

  As mentioned above, although preferred embodiment of this invention was described, this invention is not necessarily limited to embodiment mentioned above. Various modifications of the present invention are possible without departing from the spirit of the present invention, and these modified examples are also included in the present invention.

  For example, the piezoelectric thin film 3 may be formed by a solution method instead of the vapor phase growth method.

  EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to these Examples.

Example 1
A single crystal substrate made of SrTiO ₃ was prepared. The orientation (001) of the crystal plane of SrTiO ₃ was the same as the normal direction of the single crystal substrate. The single crystal substrate was a 20 mm × 20 mm square. The thickness of the single crystal substrate was 500 μm.

In the vacuum chamber, a first electrode layer made of SrRuO ₃ was formed on the entire surface of the single crystal substrate. The first electrode layer was formed by the PLD method. The temperature of the single crystal substrate in the process of forming the first electrode layer was maintained at 400 ° C. The oxygen partial pressure in the vacuum chamber during the formation process of the first electrode layer was maintained at 50 mTorr. As a target composed of SrRuO ₃ , a target manufactured by Kojundo Chemical Laboratory Co., Ltd. was used. The power of the laser irradiated to the target was 250 mJ. The thickness of the first electrode layer was adjusted to 0.1 μm.

In the vacuum chamber, a piezoelectric thin film was formed on the entire surface of the first electrode layer. The piezoelectric thin film was formed by the PLD method. The temperature (film formation temperature) of the single crystal substrate during the formation of the piezoelectric thin film was maintained at 500 ° C. The oxygen partial pressure in the vacuum chamber during the formation of the piezoelectric thin film was maintained at 50 mTorr. A BKT target was used for forming the piezoelectric thin film. When producing the BKT target, the blending ratio of the BKT target raw material powder (bismuth oxide, potassium carbonate and titanium oxide) was determined according to the composition of the target piezoelectric thin film, and the composition of the BKT target was adjusted. The composition of the target piezoelectric thin film was represented by the following chemical formula 1. The values of x, y and x + y in the following formula 1 were the values shown in Table 1 below. The power of the laser irradiated to the BKT target was 250 mJ. The thickness of the piezoelectric thin film was adjusted to 200 nm.
_{(Bi x K y) TiO 3} (1)

  By the above method, a laminate including a single crystal substrate, a first electrode layer overlapping the single crystal substrate, and a piezoelectric thin film overlapping the first electrode layer was manufactured. The composition of the piezoelectric thin film located on the surface of the laminate was analyzed by X-ray fluorescence analysis (XRF method). For the analysis, a device PW2404 manufactured by Phillips was used. As a result of the analysis, it was confirmed that the composition of the piezoelectric thin film of Example 1 was represented by the above chemical formula 1, and the values of x, y and x + y in the chemical formula 1 were the values shown in Table 1 below.

  The following steps were further performed using the laminate produced by the above method.

  In the vacuum chamber, a second electrode layer made of Pt was formed on the entire surface of the piezoelectric thin film. The second electrode layer was formed by a sputtering method. The temperature of the single crystal substrate during the formation process of the second electrode layer was maintained at 500 ° C. The thickness of the second electrode layer was adjusted to 0.1 μm.

  Through the above steps, a laminate including a single crystal substrate, a first electrode layer overlapping the single crystal substrate, a piezoelectric thin film overlapping the first electrode layer, and a second electrode layer overlapping the piezoelectric thin film was produced. Subsequently, the laminated structure on the single crystal substrate was patterned by photolithography. Subsequently, the entire laminate was cut by dicing.

  Through the above steps, a strip-shaped piezoelectric thin film element of Example 1 was obtained. The piezoelectric thin film element includes a single crystal substrate, a first electrode layer overlapping the single crystal substrate, a piezoelectric thin film overlapping the first electrode layer, and a second electrode layer overlapping the piezoelectric thin film. The dimension of the movable part of the piezoelectric thin film was 20 mm × 1.0 mm.

The X-ray diffraction (XRD) pattern of the piezoelectric thin film element of Example 1 was measured. For the measurement, an X-ray diffractometer (SmartLab) manufactured by Rigaku Corporation was used. 2θ-θ measurement was performed in the range of diffraction angle 2θ = 10 to 70 °. Measurement conditions were set so that each peak intensity in the XRD pattern was at least three orders of magnitude higher than the background intensity. Only the peaks of the (100), (001), (110), (101), and (111) plane orientations derived from the oxide BKT constituting the piezoelectric thin film were extracted from the XRD pattern.
The crystal plane spacing a of the oxide BKT (lattice constant of the oxide BKT in the direction parallel to the single crystal substrate) was determined by In Plane measurement. The crystal plane spacing c of the oxide BKT (the lattice constant of the oxide BKT in the direction perpendicular to the single crystal substrate) was determined by Out of plane measurement. By comparing the crystal plane spacing a and the crystal plane spacing c, the (100) plane orientation and the (001) plane orientation were distinguished. Further, the (110) plane orientation was distinguished from the (101) plane orientation by comparing the crystal plane spacing a and the crystal plane spacing c. That is, the oxide BKT is tetragonal at room temperature, and in the oxide BKT, the (001) face spacing is larger than the (100) face spacing, and the (101) face spacing is larger than the (110) face spacing. . Therefore, the (001) plane orientation and the (101) plane orientation were defined with reference to the direction where the plane spacing is large.
Based on the peak intensity of each plane orientation of (100), (001), (110), (101), and (111) derived from the oxide BKT, and the total value ΣI _(hkl) thereof, Ρ of each plane orientation was calculated.
(Bi _0.5 K _0.5 ) TiO ₃ powder (standard sample) was prepared. The X-ray diffraction pattern of this standard sample was measured. Based on the X-ray diffraction pattern of the standard sample, ρ ₀ of each plane orientation was calculated.
Based on ρ and ρ ₀ of each plane orientation of the oxide BKT, the orientation degree F of each plane orientation of the oxide BKT was calculated. Of the orientation degrees F of the respective plane orientations, the plane orientation coinciding with the normal direction of the single crystal substrate and the orientation degree are shown in Table 1 below. When the degree of orientation of the plane orientation that matches the normal direction of the single crystal substrate is 80% or more, the plane orientation of the oxide BKT is preferentially oriented in the normal direction of the single crystal substrate. The plane orientation preferentially oriented in the normal direction of the crystal substrate is hereinafter referred to as “preferential orientation orientation”.
ρ = I ₍₁₀₀₎ / ΣI _(hkl)
ρ ₀ = I _{0 (100)} / ΣI _{0 (hkl)}
F (100) = {(ρ−ρ ₀ ) / (1−ρ ₀ )} × 100

ρ = I ₍₀₀₁₎ / ΣI _(hkl)
ρ = I _{0 (001)} / ΣI _{0 (hkl)}
F (001) = {(ρ−ρ ₀ ) / (1−ρ ₀ )} × 100

ρ = I ₍₁₁₀₎ / ΣI _(hkl)
ρ = I _{0 (110)} / ΣI _{0 (hkl)}
F (110) = {(ρ−ρ ₀ ) / (1−ρ ₀ )} × 100

ρ = I ₍₁₀₁₎ / ΣI _(hkl)
ρ = I _{0 (101)} / ΣI _{0 (hkl)}
F (101) = {(ρ−ρ ₀ ) / (1−ρ ₀ )} × 100

ρ = I ₍₁₁₁₎ / ΣI _(hkl)
ρ = I _{0 (111)} / ΣI _{0 (hkl)}
F (111) = {(ρ−ρ ₀ ) / (1−ρ ₀ )} × 100

A continuous driving test using the piezoelectric thin film element of Example 1 was performed according to the following procedure. In the test, a sine wave voltage having a maximum value of 5 V was applied between the first electrode layer and the second electrode layer of the piezoelectric thin film element. This voltage is a value assumed to be applied to the piezoelectric thin film element as an actual product. The displacement of the piezoelectric thin film accompanying voltage application was measured using a laser Doppler displacement meter. Measurement of the displacement, based on the values such as the thickness of the piezoelectric thin film was calculated piezoelectric constant d _31. In addition, the capacitance of the piezoelectric thin film was measured. For measurement of the capacitance, an LCR meter (4980A) manufactured by Keysight Technologies was used. The relative dielectric constant εr of the piezoelectric thin film was calculated from the measured capacitance value, the area of each electrode layer, and the thickness of the piezoelectric thin film. The piezoelectric constant g ₃₁ of the piezoelectric thin film was calculated using the piezoelectric constant d ₃₁ and the relative dielectric constant εr. The d ₃₁ [pm / V], εr [−] and g ₃₁ [× 10 ⁻³ Vm / N] of Example 1 are shown in Table 1 below.

(Examples 2-18, Comparative Examples 1-6, Comparative Example 9, Comparative Examples 21-29)
Except that the composition of the BKT target used for forming the piezoelectric thin film is different, the piezoelectric thin film elements of Examples 2 to 18 and Comparative Examples 1 to 6, 9, and 21 to 29 are prepared in the same manner as in Example 1. Produced.

  The compositions of the piezoelectric thin films of Examples 2 to 18 and Comparative Examples 1 to 6, 9, and 21 to 29 were analyzed by the same XRF method as that of Example 1. The compositions (x, y and x + y values) of Examples 2 to 18 and Comparative Examples 1 to 6, 9, 21 to 29 are shown in Table 1 or Table 2 below.

In the same manner as in Example 1, the preferential orientation directions of the oxides BKT constituting the piezoelectric thin films of Examples 2 to 18 and Comparative Examples 1 to 6, 9, 21 to 29 were determined. The preferential orientation directions of Examples 2 to 18 and Comparative Examples 1 to 6, 9, 21 to 29 are shown in Table 1 or Table 2 below. Examples 1 to 6, and Comparative Examples 1 to 6, 9, 21 to 29 show the degree of orientation of the preferred orientation directions in Table 1 or Table 2 below. In the table below, when the orientation degree of the plane orientation of the oxide BKT in the normal direction of the single crystal substrate is less than 80%, “none” is described in the column of the preferential orientation orientation. However, even when there is no preferred orientation direction, the orientation degree of the plane orientation of the oxide BKT in the normal direction of the single crystal substrate is described in the column of orientation degree in the following table. Further, the d ₃₁ , εr and g ₃₁ of Examples 2 to 18 and Comparative Examples 1 to 6, 9, 21 to 29 obtained by the same measurement and calculation of Example 1 are shown in Table 1 or Table 2 below. Shown in In the table below, the comparative example in which d ₃₁ , εr and g ₃₁ are not described indicates that the electrical resistance of the piezoelectric thin film is too low to measure d ₃₁ , εr and g _31. Yes. That is, in the comparative example in which d ₃₁ , εr and g ₃₁ are not described in the following table, it was desired to obtain desired piezoelectric characteristics.

(Examples 19 and 20, Comparative Examples 15 and 16)
In the formation processes of the piezoelectric thin films of Examples 19 and 20 and Comparative Examples 15 and 16, the oxygen partial pressure in the vacuum chamber was adjusted to the values shown in Table 3 below. Except for this difference in oxygen partial pressure, piezoelectric thin film elements of Examples 19 and 20 and Comparative Examples 15 and 16 were produced in the same manner as in Example 13.

  The compositions of the piezoelectric thin films of Examples 19 and 20 and Comparative Examples 15 and 16 were analyzed by the same XRF method as that of Example 1. The compositions (x, y, and x + y values) of Examples 19 and 20 and Comparative Examples 15 and 16 are shown in Table 3 below.

The preferential orientation directions of the oxide BKT constituting the piezoelectric thin films of Examples 19 and 20 and Comparative Examples 15 and 16 were determined in the same manner as in Example 1. The preferred orientation directions of Examples 19 and 20 and Comparative Examples 15 and 16 are shown in Table 3 below. Table 3 below shows the degree of orientation of the preferred orientation directions of Examples 19 and 20 and Comparative Examples 15 and 16. In addition, Table 3 below shows d ₃₁ , εr, and g ₃₁ of Examples 19 and 20 and Comparative Examples 15 and 16 obtained by the same measurement and calculation of Example 1.

(Examples 21 to 24)
In Example 21, the temperature (film formation temperature) of the single crystal substrate during the piezoelectric thin film formation process was maintained at 600 ° C. This film formation temperature was higher than the film formation temperature (500 ° C.) in Examples 1 and 13 above. In the formation process of the piezoelectric thin film of Example 21, the oxygen partial pressure in the vacuum chamber was adjusted to the values shown in Table 4 below.

In the single crystal substrates used in Examples 22 and 23, the (110) plane orientation of SrTiO ₃ was the same as the normal direction of the single crystal substrate. In Example 23, the temperature (film formation temperature) of the single crystal substrate during the piezoelectric thin film formation process was maintained at 600 ° C. This film forming temperature was higher than the film forming temperature in Example 22 (500 ° C.). In each of the piezoelectric thin film formation processes of Examples 22 and 23, the oxygen partial pressure in the vacuum chamber was adjusted to the values shown in Table 4 below.

In the single crystal substrate used in Example 24, the (111) plane orientation of SrTiO ₃ was the same as the normal direction of the single crystal substrate. In the formation process of the piezoelectric thin film of Example 24, the oxygen partial pressure in the vacuum chamber was adjusted to the values shown in Table 4 below.

  Except for the above differences, the piezoelectric thin film elements of Examples 21 to 24 were produced in the same manner as in Example 13.

  The composition of each of the piezoelectric thin films of Examples 21 to 24 was analyzed by the same XRF method as that of Example 1. The compositions (x, y, and x + y values) of each of the piezoelectric thin films of Examples 21 to 24 are shown in Table 4 below.

The preferred orientation direction of the oxide BKT constituting each of the piezoelectric thin films in Examples 21 to 24 was determined in the same manner as in Example 1. The preferred orientation directions of Examples 21 to 24 are shown in Table 4 below. The degree of orientation of each of the preferred orientation directions of Examples 21 to 24 is shown in Table 4 below. In addition, Table ₃₁ below shows d ₃₁ , εr, and g ₃₁ of Examples 21 to 24 obtained by the same measurement and calculation of Example 1.

The X-ray diffraction pattern of Example 6 is shown in FIG. Excluding the peak derived from SrTiO ₃ (single crystal substrate) and the peak derived from SrRuO ₃ (first electrode layer), the steepness derived from the (100) plane of the oriented oxide BKT (piezoelectric thin film) There was a peak. The peak intensity of the oxide BKT having a plane orientation other than (100) and (200) was slight. Moreover, the peak originating in a different phase (subcomponent which may arise in the formation process of oxide BKT) was not confirmed. The profile of this pattern suggests that an oxide BKT (piezoelectric thin film) having a high degree of orientation and no heterogeneous phase was obtained. The XRD patterns of other examples and comparative examples were analyzed to evaluate the presence or absence of different phases in the piezoelectric thin films of other examples and comparative examples. The evaluation results are shown in Tables 1 to 4 below.

  As shown in FIG. 11, x and y of all Examples and Comparative Examples were plotted. A diamond mark in FIG. 11 corresponds to the example, and a triangle mark corresponds to the comparative example.

As shown in Tables 1 to 4 above, the compositions of the piezoelectric thin films of all the examples satisfied the following chemical formula 1. In the piezoelectric thin films of all the examples, one of the plane orientations of the oxide BKT was preferentially oriented in the normal direction of the single crystal substrate. No heterogeneous phase was detected in the piezoelectric thin films of all the examples. D _{31 of} all Examples was 30 pm / V or more. G _{31 of} all Examples was 10 × 10 ⁻³ Vm / N or more.
_{(Bi x K y) TiO 3} (1)
[In the above chemical formula 1, 0.30 ≦ x ≦ 0.60, 0.30 ≦ y ≦ 0.60, 0.60 ≦ x + y ≦ 1.10. ]

On the other hand, there was no comparative example in which the composition of the piezoelectric thin film satisfied the chemical formula 1 and the preferential orientation direction of the oxide BKT was present. Further, there was no comparative example in which d ₃₁ was 30 pm / V or more and g ₃₁ was 10 × 10 ⁻³ Vm / N or more.

  As shown in Table 3, it was found that the orientation degree of the plane orientation of the oxide BKT changes depending on the oxygen partial pressure in the vacuum chamber in the process of forming the piezoelectric thin film.

As shown in Examples 13 and 21 to 24 (data in Table 4), the preferred orientation direction of the piezoelectric thin film depends on the film forming temperature of the piezoelectric thin film, the oxygen partial pressure during film formation, and the plane orientation of the single crystal substrate. It has changed. Regardless of the difference in preferred orientation, d ₃₁ of Examples 13 and 21 to 24 was 30 pm / V or more, and g ₃₁ of Examples 13 and 21 to 24 was 10 × 10 ⁻³ Vm / N or more. .

According to the present invention, a piezoelectric thin film having a large d ₃₁ and g ₃₁ , a piezoelectric thin film element, and a piezoelectric actuator, a piezoelectric sensor, a head assembly, a head stack assembly, a hard disk drive, a printer head, and an inkjet printer using the piezoelectric thin film element An apparatus is provided.

DESCRIPTION OF SYMBOLS 100 ... Piezoelectric thin film element, 1 ... Single crystal substrate, 2 ... 1st electrode layer, 3 ... Piezoelectric thin film, 4 ... 2nd electrode layer, _DN ... The normal direction of the single crystal substrate 1, D (HKL) ... Single crystal the plane orientation of the oxide BKT are oriented preferentially in the direction normal _{D N} of the substrate 1, 200 ... head assembly, 9 ... base plate, 11 ... load beam, 11b ... proximal end, 11c ... first plate spring portion , 11d: second leaf spring part, 11e: opening, 11f: beam main part, 15 ... flexible substrate, 17 ... flexure, 19 ... head slider, 19a ... head element, 300 ... piezoelectric actuator, 20 ... base, 21 ... Pressure chamber, 23 ... insulating film, 24 ... single crystal substrate, 25 ... piezoelectric thin film, 26 ... upper electrode layer (first electrode layer), 27 ... nozzle, 400 ... gyro sensor, 110 ... base, 120, 130 ... arm, DESCRIPTION OF SYMBOLS 0 ... Piezoelectric thin film, 31 ... Upper electrode layer (first electrode layer), 31a, 31b ... Drive electrode layer, 31c, 31d ... Detection electrode layer, 32 ... Single crystal substrate, 500 ... Pressure sensor, 40 ... Piezoelectric thin film element, DESCRIPTION OF SYMBOLS 41 ... Common electrode layer, 42 ... Piezoelectric thin film, 43 ... Individual electrode layer, 44 ... Support body, 45 ... Cavity, 46 ... Current amplifier, 47 ... Voltage measuring device, 600 ... Pulse wave sensor, 50 ... Piezoelectric thin film element, 51 ... Common electrode layer, 52 ... Piezoelectric thin film, 53 ... Individual electrode layer, 54 ... Support, 55 ... Voltage measuring device, 700 ... Hard disk drive, 60 ... Housing, 61 ... Hard disk, 62 ... Head stack assembly, 63 ... Voice Coil motor, 64 ... Actuator arm, 65 ... Head assembly, 800 ... Inkjet printer device, 70 ... Printer head, 71 ... Main body, 72 ... Tray, 73 ... Head driving mechanism, 74 ... outlet, 75 ... recording sheet, 76 ... sheet feeder (automatic continuous feed mechanism).

Claims (11)

A piezoelectric thin film overlapping a single crystal substrate,
The piezoelectric thin film includes a crystalline oxide represented by the following chemical formula 1,
One of the plane orientations of the oxide selected from the group consisting of (100), (001), (110), (101) and (111) is preferentially oriented in the normal direction of the single crystal substrate. Yes,
Piezoelectric thin film.
_{(Bi x K y) TiO 3} (1)
[In the above chemical formula 1, 0.30 ≦ x ≦ 0.60, 0.30 ≦ y ≦ 0.60, 0.60 ≦ x + y ≦ 1.10. ] The plane orientation preferentially oriented in the normal direction is (001).
The piezoelectric thin film according to claim 1. A single crystal substrate, and a piezoelectric thin film overlapping the single crystal substrate,
The piezoelectric thin film includes a crystalline oxide represented by the following chemical formula 1,
One of the plane orientations of the oxide selected from the group consisting of (100), (001), (110), (101) and (111) is preferentially oriented in the normal direction of the single crystal substrate. Yes,
Piezoelectric thin film element.
_{(Bi x K y) TiO 3} (1)
[In the above chemical formula 1, 0.30 ≦ x ≦ 0.60, 0.30 ≦ y ≦ 0.60, 0.60 ≦ x + y ≦ 1.10. ] The plane orientation preferentially oriented in the normal direction is (001).
The piezoelectric thin film element according to claim 3. The piezoelectric thin film element according to claim 3 or 4,
Piezoelectric actuator. The piezoelectric thin film element according to claim 3 or 4,
Piezoelectric sensor. The piezoelectric actuator according to claim 5 is provided.
Head assembly. The head assembly according to claim 7 is provided.
Head stack assembly. The head stack assembly according to claim 8 is provided.
Hard disk drive. The piezoelectric actuator according to claim 5 is provided.
Printer head. The printer head according to claim 10.
Inkjet printer device.

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