Optical actuator and method for manufacturing same

Abstract

This optical actuator driven by irradiation light includes a dielectric layer comprising SmxBi1-xFeO3 with high orientation, and a protective layer comprising amorphous oxide. Distortion is added to the dielectric layer from the protective layer. The dielectric layer is deformed by inverse piezoelectric effect by the irradiation light. The optical actuator driven by the irradiation light includes a dielectric layer comprising polycrystalline SmxBi1-xFeO3, and a protective layer comprising amorphous oxide. The dielectric layer is deformed by inverse piezoelectric effect by irradiation light.

Description

Optical actuator and method of manufacturing the same

[0001] The present invention relates to an optical actuator, and in particular to a samarium bismuth ferrite (Sm ｘ Bi １－ｘ FeO ３ The present invention relates to an optical actuator using a ferroelectric oxide thin film consisting of: 0≦x≦0.13).

[0002] Optically driven actuators (hereinafter referred to as "optical actuators") that convert light into mechanical movement differ from electrically driven actuators that convert electricity into mechanical movement in that they do not require a power source or wiring to drive the actuator, allowing for weight reduction and a simplified structure. They also allow remote control using light, offering excellent properties not found in electrically driven actuators. Optical actuators that use organic materials and are driven by light-induced conversion of the chemical bonds of the organic materials (photoisomerization) have been proposed (see, for example, Non-Patent Document 1). However, because they utilize photoisomerization, they require two types of light sources to operate as actuators, and have problems such as a slow drive speed that makes high-speed modulation difficult and a limited number of repetitions.

[0003] In response to this, an optical actuator has been proposed that uses an oxide ferroelectric material instead of an organic material, and is driven by utilizing the piezoelectric effect of electrons and holes generated by irradiating the oxide ferroelectric material with light (see, for example, Non-Patent Document 2).

[0004] Y. Chen, J. Yang, X. Zhang, Y. Feng, H. Zeng, L. Wang, et al., Mater. Horiz. 2021, 8, 728-757C. Chen and Z. Yi, Adv. Funct. Mater. 2021, 31, 2010706

[0005] However, because it is difficult to fabricate thin films of oxide ferroelectric materials, bulk oxide ferroelectrics have been used, resulting in problems such as minute displacements of a few nanometers and low resonant frequencies of 80 Hz or less, as well as the need for expensive high-energy light sources for driving.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an optical actuator that uses a thin film of an oxide ferroelectric material and that can obtain a large amount of displacement at high speed using an inexpensive, low-energy light source.

[0007] One aspect of the present disclosure is an optical actuator driven by irradiated light, comprising: a highly oriented Sm ｘ Bi １－ｘ FeO ３ and a protective layer made of amorphous oxide, wherein strain is applied to the dielectric layer from the protective layer, and the dielectric layer is deformed by the inverse piezoelectric effect caused by irradiated light.

[0008] Another aspect of the present disclosure is an optical actuator driven by irradiated light, comprising polycrystalline Sm ｘ Bi １－ｘ FeO ３ and a protective layer made of amorphous oxide, in which the dielectric layer is deformed by the inverse piezoelectric effect caused by irradiated light.

[0009] Another aspect of the present disclosure is a method for preparing a strontium titanate substrate, and depositing Sr ３ Al ２ O ６ a sacrificial layer made of Sm ｘ Bi １－ｘ FeO ３ a step of epitaxially growing a ferroelectric oxide sheet and a dielectric layer made of amorphous oxide; a step of forming a protective layer made of amorphous oxide on the dielectric layer to produce an as-grown film made of a substrate, a sacrificial layer, the dielectric layer, and the protective layer; and a step of immersing the as-grown film in a solution to dissolve the sacrificial layer and separating an oxide ferroelectric sheet made of the dielectric layer and the protective layer from the substrate.

[0010] Another aspect of the present disclosure is a method for manufacturing a semiconductor device comprising the steps of: preparing a silicon or glass substrate; and depositing a sacrificial layer of CaO or BaO on the substrate; and depositing a sacrificial layer of Sm ｘ Bi １－ｘ FeO ３a step of forming a dielectric layer made of amorphous oxide on the dielectric layer to produce an as-grown film made of a substrate, a sacrificial layer, the dielectric layer, and the protective layer; and a step of immersing the as-grown film in a solution to dissolve the sacrificial layer and separating an oxide ferroelectric sheet made of the dielectric layer and the protective layer from the substrate.

[0011] Another aspect of the present disclosure is an optical actuator driven by irradiated light, comprising: a highly oriented REE ｘ Bi １－ｘ FeO ３ The REE comprises a dielectric layer made of an element selected from the group consisting of La, Eu, Gd, and Yb, and a protective layer made of an amorphous oxide, and strain is applied to the dielectric layer from the protective layer, and the dielectric layer is deformed by the inverse piezoelectric effect caused by irradiated light.

[0012] Another aspect of the present disclosure is a method for preparing a strontium titanate substrate, and depositing Sr ３ Al ２ O ６ a sacrificial layer consisting of REE ｘ Bi １－ｘ FeO ３ The method for manufacturing an optical actuator includes the steps of epitaxially growing a dielectric layer, wherein REE is an element selected from the group consisting of La, Eu, Gd, and Yb; forming a protective layer made of an amorphous oxide on the dielectric layer to produce a laminated film made of a substrate, a sacrificial layer, the dielectric layer, and the protective layer; and immersing the laminated film in a solution to dissolve the sacrificial layer and separating an oxide ferroelectric sheet made of the dielectric layer and the protective layer from the substrate.

[0013] Sm according to the present invention ｘ Bi １－ｘ FeO ３Optical actuators using dielectric layers can achieve sufficient displacement using a single, inexpensive, low-energy light source, and can perform high-speed, highly reliable, and repeated movements. Furthermore, they can be made smaller and simpler than electrically driven actuators, and can be remotely operated in environments including physiological saline.

[0014] In addition, the Sm ｘ Bi １－ｘ FeO ３ In an optical actuator using a dielectric layer, the use of a polycrystalline dielectric layer allows for a large area.

[0015] 1 is a schematic diagram of a method for manufacturing a highly oriented oxide ferroelectric sheet according to a first embodiment of the present invention. (a) X-ray diffraction (XRD) measurement results and (b) reciprocal space mapping (RSM) measurement results of an as-grown film of a highly oriented oxide ferroelectric sheet. (a) X-ray diffraction (XRD) measurement results and (b) reciprocal space mapping (RSM) measurement results of a highly oriented oxide ferroelectric sheet after peeling from a single crystal substrate. (b) Photographs of a highly oriented oxide ferroelectric sheet. (a) Photographs of a highly oriented oxide ferroelectric sheet without light irradiation, and (b) photographs of a highly oriented oxide ferroelectric sheet during light irradiation. (b) Photographs of a highly oriented oxide ferroelectric sheet with light irradiation. (c) Photographs of a highly oriented oxide ferroelectric sheet with time dependence. (d) Photographs of a highly oriented oxide ferroelectric sheet with time dependence. (e) Photographs of a highly oriented oxide ferroelectric sheet with time dependence. (f) Photographs of a highly oriented oxide ferroelectric sheet with time dependence. (g) Photographs of a highly oriented oxide ferroelectric sheet with time dependence. (h) Photographs of a highly oriented oxide ferroelectric sheet with time dependence. (i) Photographs of a highly oriented oxide ferroelectric sheet with time dependence. (ii) Photographs of a highly oriented oxide ferroelectric sheet with time dependence. (iii) Photographs of a highly oriented oxide ferroelectric sheet with time dependence. (iv) Photographs of a highly oriented oxide ferroelectric sheet with time dependence. (v) Photographs of a highly oriented oxide ferroelectric sheet with time dependence. (v) Photographs of a highly oriented oxide ferroelectric sheet with time dependence. (vi) Photographs of a highly oriented oxide ferroelectric sheet with time dependence. (vi) Photographs of a highly oriented oxide 15A and 15B are photographs of a highly oriented oxide ferroelectric sheet (a) before light irradiation (initial), (b) during green laser light irradiation (green ON), and (c) after green laser light irradiation and after irradiation has stopped (light OFF).

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[0016] In an embodiment of the present invention, Sm ｘ Bi １－ｘ FeO ３ As an optical actuator using a dielectric layer made of highly oriented Sm ｘ Bi １－ｘ FeO ３and a sheet using polycrystalline Sm ｘ Bi １－ｘ FeO ３ Two types of sheets were produced using the same material (Embodiment 2). Each type of sheet will be described below.

[0017] First Embodiment: Highly Oriented Oxide Ferroelectric Sheet Fig. 1 is a schematic diagram of a method for manufacturing a highly oriented oxide ferroelectric sheet according to a first embodiment of the present invention, the entire diagram being denoted by 100. First, as shown in Fig. 1(a), strontium titanate (SrTiO ３ ) (001) single crystal substrate 50 is prepared. Next, Sr ３ Al ２ O ６ The water-soluble sacrificial layer 60 is epitaxially grown at a substrate temperature of, for example, 700° C. to 800° C. The thickness of the sacrificial layer 60 is, for example, 20 nm to 50 nm.

[0018] Next, the dielectric layer 10 is epitaxially grown on the sacrificial layer 60 by using the pulsed laser deposition (PLD) method as well. The substrate temperature is, for example, 700° C. to 800° C. The dielectric layer 10 is made of Sm ｘ Bi １－ｘ FeO ３ (0≦x≦0.13) and is a crystalline layer having a high degree of orientation with respect to the single crystal substrate 50. The thickness of the dielectric layer 10 is, for example, 100 nm to 400 nm.

[0019] Next, a conductive electrode layer 20 is deposited on the dielectric layer 10 at room temperature. The electrode layer 20 is made of crystallized ITO (Indium Tin Oxide). The film thickness is, for example, 0 nm to 100 nm, which means that the electrode layer 20 may not be formed. The electrode layer 20 may be made of amorphous ITO (a-ITO), RuO ２ may be.

[0020] Next, an oxide protective layer 30 is deposited at room temperature on the electrode layer 20. The protective layer 30 is made of amorphous AlO ｘ The protective layer 30 is made of glass and has a thickness of, for example, 500 nm to 2 μm. ｘGlass may also be used.

[0021] Through the above steps, an as-grown film 150 is formed on the single crystal substrate 50, in which the sacrificial layer 60, the dielectric layer 10, the electrode layer 20, and the protective layer 30 are stacked, as shown in FIG. 1(a).

[0022] Finally, the as-grown film 150 is immersed in pure water to dissolve the water-soluble sacrificial layer 60. This causes the laminate of the dielectric layer 10, the electrode layer 20, and the protective layer 30 to be peeled off from the single-crystal substrate 50, yielding a highly oriented oxide ferroelectric sheet 100 as shown in FIG.

[0023] FIG. 2(a) shows the as-grown film 150 (Sm ｘ Bi １－ｘ FeO ３ 2(a) shows the results of X-ray diffraction (XRD) measurement of the dielectric layer 10 (x=0.06), and FIG. 2(b) shows the results of reciprocal space mapping (RSM) measurement.

[0024] 2A, the horizontal axis represents the scattering vector, and the vertical axis represents the scattering intensity. ３ The peak (*) derived from the single crystal substrate 50 and Sm ｘ Bi １－ｘ FeO ３ Diffraction peaks of 001 and 002 originating from the crystalline structure were detected.

[0025] In FIG. 2B, the horizontal axis represents the scattering vector (x-axis component), and the vertical axis represents the scattering vector (z-axis component). ３ Along with the spots originating from the (001) single crystal substrate (STO103), Sm ｘ Bi １－ｘ FeO ３ The results of Figures 2(a) and 2(b) show that the as-grown film 150 contains Sm ｘ Bi １－ｘ FeO ３ The dielectric layer 10 is made of SrTiO ３ It can be seen that the crystal has been epitaxially grown on the single crystal substrate 50 with a high degree of orientation.

[0026] On the other hand, FIG. 3(a) shows the highly oriented oxide ferroelectric sheet 100 (Sm ｘ Bi １－ｘ FeO ３ 3(a) shows the results of X-ray diffraction (XRD) measurement of the dielectric layer 10 (x=0.06), and FIG. 3(b) shows the results of reciprocal space mapping (RSM) measurement.

[0027] From the X-ray diffraction results of FIG. 3(a), it is clear that the highly oriented oxide ferroelectric sheet 100 after peeling also contains Sm ｘ Bi １－ｘ FeO ３ Diffraction peaks of 001 and 002 originating from the highly oriented oxide ferroelectric sheet 100 were detected, indicating that high orientation was maintained. Note that the mark "*" indicates a peak originating from the PT substrate to which the highly oriented oxide ferroelectric sheet 100 was attached.

[0028] Furthermore, the reciprocal lattice space mapping measurement results in Fig. 3(b) also show that Sm ｘ Bi １－ｘ FeO ３ A spot (103) derived from the antibody was observed.

[0029] Thus, the highly oriented oxide ferroelectric sheet 100 after peeling also gave similar XRD and RSM measurement results to the as-grown film 150, and Sm ｘ Bi １－ｘ FeO ３ The dielectric layer 10 is made of strontium titanate (SrTiO ３ ) (001) It can be seen that a high orientation state with respect to the crystal direction of the single crystal substrate 50 is maintained.

[0030] 4 shows photographs of the highly oriented oxide ferroelectric sheet 100, with the top photograph being a planar photograph and the bottom photograph being a side photograph. The highly oriented oxide ferroelectric sheet 100 was photographed in a state where it was fixed to a tungsten rod with ultraviolet curing resin. (a) to (f) show the results of the dielectric layer 10 being made of Sm with x=0, 0.03, 0.06, 0.09, 0.11, and 0.13, respectively. ｘ Bi １－ｘ FeO ３ Corresponds to.

[0031] As can be seen from each photograph, a highly oriented oxide ferroelectric sheet 100 of millimeter size was obtained.

[0032] In addition, Sm for x = 0, 0.03, 0.09, 0.11, and 0.13 ｘ Bi １－ｘ FeO ３ As a result of XRD and RSM measurements, the highly oriented oxide ferroelectric sheet 100 including the dielectric layer 10 also showed that the Sm ｘ Bi １－ｘ FeO ３ It has been confirmed that the dielectric layer 10 maintains a highly oriented state.

[0033] FIG. 5 shows a highly oriented dielectric layer 10 (Sm ｘ Bi １－ｘ FeO ３ Photographs of a highly oriented oxide ferroelectric sheet 100 containing a highly oriented oxide ferroelectric material (x=0.06) are shown in (a) a case where it is not irradiated with light and (b) a case where it is irradiated with light. The light used for irradiation was a single light source of green laser light with a wavelength of 526 nm and an energy of 180 mW.

[0034] It can be seen that the upper end of the highly oriented oxide ferroelectric sheet 100 is displaced to the left by the light irradiation. The amount of displacement at the upper end was about 1.8 mm.

[0035] Figure 6 is a graph showing the time dependence of the displacement of the highly oriented oxide ferroelectric sheet 100, with the horizontal axis representing time and the vertical axis representing displacement. Using a shutter, the above-mentioned green laser light was repeatedly irradiated and unirradiated at a cycle of 0.5 Hz. In Figure 6, the colored areas indicate no light irradiation, and the uncolored areas indicate light irradiation. It can be seen that the displacement is repeated by simply turning a single light source on and off, without using multiple light sources with different wavelengths. It can also be seen that displacement occurs immediately after light irradiation. Furthermore, the displacement is reproducible by turning the light on and off.

[0036] 7 is a graph showing the irradiation energy dependency of the displacement of the highly oriented oxide ferroelectric sheet 100, where the horizontal axis represents the energy of the irradiated laser light and the vertical axis represents the displacement. As can be seen from FIG. 7, the larger the energy of the irradiated light, the larger the deformation, and it can be seen that the deformation shows a linear correlation with the energy.

[0037] FIG. 8 shows the highly oriented dielectric layer 10 (Sm ｘ Bi １－ｘ FeO ３ ) and the relationship between the amount of Sm in the highly oriented oxide ferroelectric sheet 100 and the displacement amount / sheet length (Δd / L). The horizontal axis represents the amount of Sm, and the vertical axis represents the displacement amount / sheet length (Δd / L). Here, "displacement amount / sheet length" is the value of the displacement amount at the tip of the highly oriented oxide ferroelectric sheet 100 (the displacement amount at the upper end in FIG. 5) / the length of the highly oriented oxide ferroelectric sheet 100 (the length from the upper end to the lower end of the sheet, the length in the vertical direction in FIG. 5). The wavelength of the irradiated light was 526 nm, and the energy was 160 mW.

[0038] As shown in FIG. 8, the displacement / sheet length is the largest when x=0.06. When x is 0 to 0.05, Sm ｘ Bi １－ｘ FeO ３ The layer structure is rhombohedral, but as x increases further, it becomes a rhombohedral + tetragonal structure from around x = 0.06, and as x increases further and exceeds around x = 0.13, it becomes a rhombohedral + tetragonal + orthorhombic structure. Due to this change in layer structure, it is thought that the displacement / sheet length becomes the largest at x = 0.06.

[0039] FIG. 9 shows the highly oriented Sm ｘ Bi １－ｘ FeO ３ 1 is a graph showing the time dependence of the light absorptance of a highly oriented oxide ferroelectric sheet 100 including a dielectric layer 10 (x=0.06), where the horizontal axis represents the irradiated wavelength and the vertical axis represents the absorptance.

[0040] As can be seen from FIG. 9, the highly oriented oxide ferroelectric sheet 100 has a high absorptance for light with a wavelength of 560 nm or less. ｘ Bi １－ｘ FeO ３ The band gap of (x=0.06) is estimated to be 2.2 eV.

[0041] FIG. 10 shows the highly oriented Sm ｘ Bi １－ｘ FeO ３(x=0.06) This is a graph showing the energy dependence of the displacement amount when a highly oriented oxide ferroelectric sheet 100 including a dielectric layer 10 is irradiated with UV laser light, blue laser light, and green laser light of different wavelengths, where the horizontal axis represents the energy of the irradiated light and the vertical axis represents the displacement amount.

[0042] The wavelengths of the irradiated light are 266 nm for the UV laser light, 470 nm for the blue laser light, and 532 nm for the green laser light, and as shown in FIG. 9, the respective absorptivities are 100%, 80%, and 35%.

[0043] 10, it can be seen that the highly oriented oxide ferroelectric sheet 100 exhibits optical actuator function when irradiated with any laser light, for light with a photon energy greater than the band gap (light with a wavelength of 560 nm or less). Furthermore, for a constant laser energy value, such as 20 mW, the displacement increases in the order of UV laser light, blue laser light, and green laser light. This is thought to be due to the dependence of the absorptivity of each light.

[0044] In addition, highly oriented Sm ｘ Bi １－ｘ FeO ３ When a highly oriented oxide ferroelectric sheet 100 including a dielectric layer 10 (x=0.06) was immersed in water (e.g., physiological saline) and irradiated with green laser light at regular intervals, the highly oriented oxide ferroelectric sheet 100 was displaced in response to the light irradiation. In this way, it has been confirmed that the highly oriented oxide ferroelectric sheet 100 can function as an optical actuator even in water.

[0045] As described above, highly oriented Sm ｘ Bi １－ｘ FeO ３ It has been confirmed that the highly oriented oxide ferroelectric sheet 100 containing the above-mentioned material can obtain a sufficiently large displacement amount by light irradiation using a single light source, and in particular, a sufficient displacement amount can be obtained even when an inexpensive low-energy light source is used. The following two mechanisms are considered to be responsible for this.

[0046] The first possible mechanism is the influence of the photovoltaic and piezoelectric effects due to ferroelectricity. That is, ferroelectrics have spontaneous ferroelectric polarization, and accordingly, photoexcited electrons and holes move in opposite directions. As a result, photovoltaic force is generated within the domain, which generates a piezoelectric effect, distorting the dielectric layer 10. On the other hand, the size of the protective layer 30 made of an AlOx glass layer does not change even when irradiated with light. As a result, the curvature of the highly oriented oxide ferroelectric sheet 100 changes, causing it to bend to one side. Also, BiFeO ３ has spontaneous polarization in the

[111] direction.

[0047] The second possible mechanism is Sm ｘ Bi １－ｘ FeO ３ 11 shows photographs of the highly oriented oxide ferroelectric sheet 100, in which (a) is a photograph before light irradiation (initial stage), (b) is a photograph during green laser light irradiation (green ON), and (c) is a photograph after green laser light irradiation has stopped (light OFF).

[0048] As can be seen by comparing the photographs (a) and (c), the shape of the sheet changes before and after irradiation with the green laser light. This is because the green laser light causes the Sm ｘ Bi １－ｘ FeO ３ This suggests that a structural phase transition of Sm ｘ Bi １－ｘ FeO ３ This suggests that the crystal system is easily variable between rhombohedral, orthorhombic, and tetragonal, and that this change in crystal system could be induced by light.

[0049] Furthermore, after the shape has changed from (a) to (c), if the irradiation of the green laser light is again repeatedly turned on and off, the shape of the highly oriented oxide ferroelectric sheet 100 will repeatably between (b) and (c).

[0050] Next, the durability of the highly oriented oxide ferroelectric sheet according to the first embodiment will be described. The sample used in the durability test has a two-layer structure consisting of a dielectric layer and a protective layer. The dielectric layer is made of BiFeO ３ It consists of (Sm ｘ Bi１－ｘ FeO ３ In this case, x=0), the film thickness is 200 nm, the protective layer is made of AlOx, and the film thickness is 1000 nm. The electrode layer is not included.

[0051] FIG. 12 is a photograph of a highly oriented oxide ferroelectric sheet, one end of which is fixed to a stainless steel wire.

[0052] FIG. 13 is a schematic diagram of a resonator device used in a durability test of an optical actuator, and includes a laser light source that irradiates the optical actuator with laser light, a laser modulator that turns the laser light on and off at the resonance frequency of the optical actuator, a displacement sensor that irradiates the optical actuator with detection laser light and detects the displacement of the optical actuator as a displacement signal from the position of the reflected detection laser light, and a phase-locked loop circuit that changes the resonance frequency to synchronize with the frequency of the displacement signal.

[0053] Specifically, the device uses a green laser beam (wavelength 532 nm, output 1.8 mW) to illuminate a BiFeO ３ The dielectric sheet is irradiated with green laser light, causing it to deform. As shown in the photograph in Figure 12, the dielectric sheet is irradiated with green laser light while one end is fixed to a stainless steel wire.

[0054] In the device, a synchronization signal from a PLL (Phase Locked Loop) is input to an optical chopper to turn the green laser light on and off, and the dielectric sheet deforms in response to the on / off state of the green laser light.

[0055] In addition to the green laser light, the dielectric sheet is irradiated with red laser light (wavelength 880 nm) through a lens (focal length f = 125 mm), and the red laser light reflected by the dielectric sheet is detected by a PSD (Position Sensitive Detector). The displacement of the dielectric sheet is detected based on the position of the red laser light detected by the PSD.

[0056] The lock-in amplifier demodulates the phase component of the displacement signal by referencing the modulation frequency of the optical chopper and sends it to the PLL. This controls the on / off of the optical chopper so that it matches the resonance frequency of the dielectric sheet. For example, even if the resonance frequency changes from its initial value due to a temperature change in the dielectric sheet, the on / off signal of the optical chopper can be synchronized to match the changed resonance frequency.

[0057] The results of the durability test using the device of FIG. 13 will be described below with reference to FIGS.

[0058] Figure 14(a) shows the results of measuring the amplitude intensity of a dielectric sheet when the frequency of the optical chopper's on / off signal is swept in the range of 120 kHz to 10 kHz using the device shown in Figure 13, with the horizontal axis representing frequency and the vertical axis representing amplitude intensity. The dielectric sheet was irradiated with green laser light with a wavelength of 532 nm and a power of 1.8 mW via the optical chopper. As can be seen from Figure 14(a), there are points where the amplitude increases at several frequencies, and these points are the resonance points. For the durability test, a resonance frequency of 4.82 kHz was selected.

[0059] Figure 14(b) shows the amplitude intensity and phase angle when the frequency of the optical chopper on / off signal is varied within a range of ±153 Hz (approximately 4.7 kHz to 4.9 kHz) around the resonant frequency. As in Figure 14(a), the amplitude reaches a maximum at 4.82 kHz, and the phase angle simultaneously reaches 0°. The Q factor at the resonant frequency fres = 4.82 kHz was 48.9.

[0060] Figure 15 shows the change in power spectral density (PSD) over time, with the horizontal axis representing time and the vertical axis representing frequency. In Figure 15, the lighter-colored areas represent resonating regions, one of which is at 4.82 kHz. Figure 15 shows that stable resonance was achieved near 4.82 kHz for approximately six hours. The figure inserted in Figure 15 shows the relationship between frequency and power spectrum 30 minutes after the start of measurement, with the horizontal axis representing frequency and the vertical axis representing power spectrum. It can be seen that the resonant frequency of 4.82 kHz was maintained after 30 minutes had passed.

[0061] Figure 16 is an enlarged view of Figure 15, with the horizontal axis representing time and the number of cycles, and the vertical axis representing the frequency deviation (Δf) from 4.82 kHz. In the graph of Figure 16, the lighter shaded areas represent the actual measured values, and the darker shaded areas represent the moving average values. Although deviations of about ±10 Hz around 4.85 kHz are observed, it can be seen that a nearly stable resonance was obtained near 4.85 kHz over a period of 6 hours (100 M cycles).

[0062] The experimental results shown in Figures 15 and 16 show that stable resonance is obtained at 116,991,040 cycles (= 24,272 seconds × 4.82 kHz) or more, the change in the resonance peak of the resonance frequency is less than ±10 Hz, and stable resonance is obtained near 4.85 kHz.

[0063] It should be noted that the experiment was intentionally stopped during the above cycle, and this does not indicate the upper limit of the durability of the sheet.

[0064] In this way, the dielectric sheet according to the first embodiment can vibrate at a stable resonant frequency for a long period of time, and can be used, for example, as a resonator, etc. Furthermore, since the resonant frequency also changes when the temperature or humidity around the dielectric sheet changes or when an attachment occurs, it is possible to detect the temperature, humidity, or the presence or absence of attachment from the change in resonant frequency, and the dielectric sheet can also be used as a sensor.

[0065] The structure of the highly oriented oxide ferroelectric sheet described in the first embodiment can also be applied to the highly oriented oxide ferroelectric sheet of the third embodiment by replacing Sm in the dielectric layer 10 with a rare earth element (La, Eu, Gd, or Yb). In the manufacturing method, a pulsed laser deposition (PLD) method is used in which La or the like is used in place of Sm, and the REE ｘ Bi １－ｘ FeO ３ (0≦x≦0.15) The dielectric layer can be epitaxially grown. The other steps are the same as those in the first embodiment.

[0066] <Second Embodiment: Polycrystalline Oxide Ferroelectric Sheet> Figure 17 is a schematic diagram of a method for manufacturing a polycrystalline oxide ferroelectric sheet according to a second embodiment of the present invention, generally designated 200. First, as shown in Figure 17(a), a Si substrate or a quartz glass substrate 55 is prepared. Next, a water-soluble sacrificial layer 65 made of CaO or BaO is formed on the substrate 55 using pulsed laser deposition (PLD). The substrate temperature is, for example, 700°C to 800°C. The film thickness of the sacrificial layer 65 is, for example, 20 nm to 100 nm.

[0067] Next, the dielectric layer 10 is formed on the sacrificial layer 65 by using the pulsed laser deposition (PLD) method. The substrate temperature is, for example, 700° C. to 800° C. The dielectric layer 15 is made of Sm ｘ Bi １－ｘ FeO ３ (0≦x≦0.13) and the film thickness is, for example, 100 nm to 400 nm.

[0068] Next, a conductive electrode layer 25 is deposited on the dielectric layer 15 at room temperature. The electrode layer 25 is made of crystallized ITO (Indium Tin Oxide). The film thickness is, for example, 0 nm to 100 nm, which means that the electrode layer 25 may not be formed. The electrode layer 25 may be made of amorphous ITO (a-ITO), RuO ２ may be.

[0069] Next, a protective oxide layer 35 is deposited at room temperature on the electrode layer 25. The protective oxide layer 35 is made of amorphous AlO ｘ The protective layer 35 is made of glass and has a thickness of, for example, 500 nm to 2 μm. ｘ Glass may also be used.

[0070] Through the above steps, an as-grown film 250 is formed on the substrate 55, in which the sacrificial layer 65, the dielectric layer 15, the electrode layer 25, and the protective layer 35 are laminated, as shown in FIG. 17(a).

[0071] Finally, the as-grown film 250 is immersed in pure water to dissolve the water-soluble sacrificial layer 65. This causes the laminate of the dielectric layer 15, the electrode layer 25, and the protective layer 35 to be peeled off from the substrate 55, yielding a polycrystalline oxide ferroelectric sheet 200 as shown in FIG.

[0072] FIG. 18 shows the as-grown film 150 (Sm ｘ Bi １－ｘ FeO ３ 18 shows the results of grazing incidence X-ray diffraction (GI-XRD) measurement of the dielectric layer 10 (x=0.06), where the horizontal axis represents the diffraction angle (2θ) and the vertical axis represents the diffraction intensity. ｘ Bi １－ｘ FeO ３ Diffraction peaks 012 and 104 resulting from the crystallization were obtained, indicating that a polycrystalline dielectric layer 15 was obtained.

[0073] FIG. 19 shows a polycrystalline oxide ferroelectric sheet 200 (Sm ｘ Bi １－ｘ FeO ３ : x = 0.06). The polycrystalline oxide ferroelectric sheet 200 is fixed to the tungsten rod with ultraviolet curing resin, and it can be seen that a millimeter-sized polycrystalline oxide ferroelectric sheet 200 is obtained.

[0074] FIG. 20 shows a polycrystalline oxide ferroelectric sheet (Sm ｘ Bi １－ｘ FeO ３ 1 is a graph showing the time dependence of the displacement of the polycrystalline oxide ferroelectric sheet 200 (x = 0.06), where the horizontal axis is time and the vertical axis is displacement. A shutter was used to repeatedly irradiate and not irradiate with green laser light at a cycle of 0.5 Hz. The colored areas indicate no light irradiation, and the uncolored areas indicate light irradiation. It can be seen that even in the polycrystalline oxide ferroelectric sheet 200, the displacement is repeated by simply turning a single light source on and off, without using light sources of multiple wavelengths.

[0075] In the polycrystalline oxide ferroelectric sheet 200, as in the case of the highly oriented oxide ferroelectric sheet 100 (see FIG. 6), a displacement occurred immediately after light irradiation, and the displacement was reproducible by turning the light on and off. However, the amount of displacement was about 60% of that of the highly oriented oxide ferroelectric sheet 100.

[0076] Thus, the polycrystalline oxide ferroelectric sheet 200 has a displacement of only about 60% compared to the highly oriented oxide ferroelectric sheet 100, but has the advantage that it can be fabricated on a large-area substrate such as a Si substrate or a glass substrate 55, making it possible to increase the area of ​​the polycrystalline oxide ferroelectric sheet 200.

[0077] In addition, Sm for x = 0, 0.03, 0.09, 0.11, and 0.13 ｘ Bi １－ｘ FeO ３ It has been confirmed that each of the polycrystalline oxide ferroelectric sheets 200 including the dielectric layer 10 also has displacement characteristics similar to those obtained when x=0.06.

[0078] As described in the first and second embodiments, the Sm ｘ Bi １－ｘ FeO ３ Optical actuators using dielectric layers can achieve sufficient displacement using an inexpensive, single-wavelength, low-energy light source. They also enable high-speed, reproducible displacement. Furthermore, polycrystalline oxide ferroelectric sheets can be used to achieve large areas. In particular, they can be made smaller and simpler than electrically driven actuators, and can be remotely controlled in environments including physiological saline.

[0079] <Embodiment 3: Highly Oriented Oxide Ferroelectric Sheet Using Other Rare Earth> Figure 21 is a graph showing the time dependence of the displacement of a highly oriented oxide ferroelectric sheet using other rare earths in the dielectric layer, where the horizontal axis represents time and the vertical axis represents the displacement. ０．０６ Bi ０．９４ FeO ３ , (b) is Eu ０．０６ Bi ０．９４ FeO ３ , (c) Gd ０．０６ Bi ０．９４FeO ３ , (d) Yb ０．０６ Bi ０．９４ FeO ３ are used as the dielectric material.

[0080] Other highly oriented oxide ferroelectric sheets using rare earth elements have a two-layer structure of a dielectric layer and a protective layer. ０．０６ Bi ０．９４ FeO ３ (REE is La, Eu, Gd, or Yb) and has a film thickness of 200 nm, and the protective layer is made of AlOx and has a film thickness of 1000 nm.

[0081] Except for the material of the dielectric layer, the aspects applied to the highly oriented oxide ferroelectric sheet of embodiment 1, such as including an electrode layer between the dielectric layer and the protective layer, can also be applied to the highly oriented oxide ferroelectric sheet of embodiment 3. The mechanism by which the highly oriented oxide ferroelectric sheet deforms is also the same as in embodiment 1.

[0082] The dielectric sheet was deformed by repeatedly irradiating and not irradiating with green laser light having a wavelength of 526 nm and an energy of 180 mW at a cycle of 0.5 Hz.

[0083] 21, it can be seen that the displacement of the highly oriented oxide ferroelectric sheet using other rare earth elements (La, Eu, Gd, and Yb) can be repeated by simply turning a single light source on and off. It can also be seen that the displacement occurs immediately after light irradiation, and that the displacement is reproducible by turning the light on and off.

[0084] In particular, the value of the displacement / sheet length (Δd / L) is (a) Yb ０．０６ Bi ０．９４ FeO ３ (b) Eu ０．０６ Bi ０．９４ FeO ３ 5.9%, (c) Gd ０．０６ Bi ０．９４ FeO ３ 7.8%, (d) Yb ０．０６ Bi ０．９４ FeO ３ The value was 27.5% at 1000 kJ / cm2, which was a large value in the highly oriented oxide ferroelectric sheet using La and Yb as rare earth elements.

[0085] In this way, it was confirmed that even with a highly oriented oxide ferroelectric sheet using a rare earth other than Sm, a sufficiently large displacement can be obtained by light irradiation using a single light source, that a sufficient displacement can be obtained even when an inexpensive low-energy light source is used, and that high-speed, highly reliable repeated operation is possible.

[0086] In addition, in FIG. 21, the dielectric layer is ｘ Bi １－ｘ FeO ３ Although the measurement results for the case of 0≦x≦0.15 are shown, it has been confirmed that a similar displacement occurs within the range of 0≦x≦0.15.

[0087] The optical actuator using the oxide ferroelectric thin film according to the present invention can be applied to electronics technologies such as MEMS devices, microrobots, filters, and microfluidic devices, as well as medical technologies.

[0088] 10, 15 Dielectric layer 20, 25 Electrode layer 30, 35 Protective layer 50, 55 Substrate 60, 65 Sacrificial layer 100 Highly oriented oxide ferroelectric sheet 150 As-grown film (laminated film) 200 Polycrystalline oxide ferroelectric sheet 250 As-grown film (laminated film)

Claims

1. An optical actuator driven by irradiated light, comprising highly oriented Sm ｘ Bi １－ｘ FeO ３ and a protective layer made of an amorphous oxide, wherein strain is applied to the dielectric layer from the protective layer, and the dielectric layer is deformed by an inverse piezoelectric effect caused by irradiated light.

2. An optical actuator driven by irradiated light, comprising polycrystalline Sm ｘ Bi １－ｘ FeO ３ and a protective layer made of an amorphous oxide, wherein the dielectric layer is deformed by an inverse piezoelectric effect caused by irradiated light.

3. Sm ｘ Bi １－ｘ FeO ３ is Sm ｘ Bi １－ｘ FeO ３ 3. The optical actuator according to claim 1, wherein x is a number in the range of 0≦x≦0.

13.

4. The optical actuator according to claim 1 or 2, wherein the crystal structure of the dielectric layer is further changed by irradiation with light.

5. The optical actuator according to claim 1 or 2, wherein the irradiated light is laser light of a single wavelength selected from the group consisting of UV laser light, blue laser light, and green laser light.

6. Sm ｘ Bi １－ｘ FeO ３ is Sm ｘ Bi １－ｘ FeO ３ 3. The optical actuator according to claim 1, wherein x=0.

06.

7. The optical actuator according to claim 1 or 2, further comprising a conductive electrode layer between the dielectric layer and the protective layer.

8. The electrode layer is made of ITO or RuO ２ The optical actuator according to claim 7, comprising:

9. The optical actuator according to claim 1 or 2, wherein the thickness of the dielectric layer is 100 nm to 400 nm.

10. The protective layer is amorphous Al ２ O ３ or amorphous SiO ２ 3. The optical actuator according to claim 1, wherein 11. The optical actuator according to claim 1 or 2, wherein the protective layer has a thickness of 500 nm to 2 μm.

12. A step of preparing a strontium titanate substrate; and depositing Sr ３ Al ２ O ６ a sacrificial layer made of Sm ｘ Bi １－ｘ FeO ３ a step of epitaxially growing a ferroelectric film comprising a substrate and a dielectric layer comprising an amorphous oxide; a step of forming a protective layer comprising an amorphous oxide on the dielectric layer to produce a laminated film comprising a substrate, a sacrificial layer, the dielectric layer, and the protective layer; and a step of immersing the laminated film in a solution to dissolve the sacrificial layer and separating an oxide ferroelectric sheet comprising the dielectric layer and the protective layer from the substrate.

13. A method for manufacturing a silicon or glass substrate, and forming a sacrificial layer of CaO or BaO on the substrate and a sacrificial layer of Sm ｘ Bi １－ｘ FeO ３ a step of forming a dielectric layer consisting of an amorphous oxide on the dielectric layer to produce a laminated film consisting of a substrate, a sacrificial layer, the dielectric layer, and the protective layer; and a step of immersing the laminated film in a solution to dissolve the sacrificial layer and separating an oxide ferroelectric sheet consisting of the dielectric layer and the protective layer from the substrate.

14. The manufacturing method according to claim 12 or 13, further comprising the step of depositing a conductive electrode layer between the dielectric layer and the protective layer, and the step of dissolving the sacrificial layer to separate the oxide ferroelectric sheet consisting of the dielectric layer, the electrode layer and the protective layer from the substrate.

15. The dielectric layer is Sm ｘ Bi １－ｘ FeO ３ The method according to claim 12 or 13, wherein x is 0≦x≦0.

13.

16. The protective layer is amorphous Al ２ O ３ or amorphous SiO ２ The method according to claim 12 or 13, comprising:

17. An optical actuator driven by irradiated light, comprising: a highly oriented REE ｘ Bi １－ｘ FeO ３ an optical actuator comprising: a dielectric layer in which the REE is an element selected from the group consisting of La, Eu, Gd, and Yb; and a protective layer made of an amorphous oxide, wherein strain is applied to the dielectric layer from the protective layer, and the dielectric layer is deformed by an inverse piezoelectric effect caused by irradiated light.

18. REE ｘ Bi １－ｘ FeO ３ Is, REE ｘ Bi １－ｘ FeO ３ 18. The optical actuator according to claim 17, wherein x is a number in the range of 0≦x≦0.

15.

19. The optical actuator according to claim 17, wherein the crystal structure of the dielectric layer is further changed by irradiation with light.

20. The optical actuator according to claim 17, wherein the irradiating light is laser light of a single wavelength selected from the group consisting of UV laser light, blue laser light, and green laser light.

21. REE ｘ Bi １－ｘ FeO ３ Is, REE ｘ Bi １－ｘ FeO ３ 18. The optical actuator according to claim 17, wherein (x=0.06).

22. The optical actuator according to claim 17, further comprising a conductive electrode layer between the dielectric layer and the protective layer.

23. The electrode layer is made of ITO or RuO ２ 23. The optical actuator according to claim 22, comprising:

24. The optical actuator according to claim 17, wherein the thickness of the dielectric layer is 100 nm to 400 nm.

25. The protective layer is amorphous Al ２ O ３ or amorphous SiO ２ The optical actuator according to claim 17, comprising:

26. The optical actuator according to claim 17, wherein the protective layer has a thickness of 100 nm to 2 μm.

27. A method for manufacturing a strontium titanate substrate, comprising: ３ Al ２ O ６ a sacrificial layer consisting of REE ｘ Bi １－ｘ FeO ３ a step of epitaxially growing a dielectric layer comprising the substrate, the dielectric layer being an element selected from the group consisting of La, Eu, Gd, and Yb; a step of forming a protective layer made of an amorphous oxide on the dielectric layer to produce a laminated film made of the substrate, the sacrificial layer, the dielectric layer, and the protective layer; and a step of immersing the laminated film in a solution to dissolve the sacrificial layer and separating an oxide ferroelectric sheet made of the dielectric layer and the protective layer from the substrate.

28. The manufacturing method according to claim 27, further comprising the step of depositing a conductive electrode layer between the dielectric layer and the protective layer, and the step of dissolving the sacrificial layer to separate the oxide ferroelectric sheet consisting of the dielectric layer, the electrode layer and the protective layer from the substrate.

29. The dielectric layer is REE ｘ Bi １－ｘ FeO ３ The method of claim 27, wherein x is 0≦x≦0.

15.

30. The protective layer is amorphous Al ２ O ３ or amorphous SiO ２ The method of claim 27, comprising:

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