A laminated composite magnetoelectric material with an acoustically coupled layer and a method of making the same

Abstract

The application provides a kind of acoustic coupling layer's laminated composite magnetoelectric material and preparation method thereof, it is related to laminated composite magnetoelectric material technical field, including acoustic coupling layer, piezoelectric layer and piezomagnetic layer, the characteristic acoustic impedance of acoustic coupling layer is A, the characteristic acoustic impedance of piezoelectric layer material is B, the characteristic acoustic impedance of piezomagnetic layer material is C, under the condition of B << C or C << B, satisfy B < A < C or C < A < B.The application effectively reduces the transmission resistance of acoustic wave by proposing an acoustic coupling layer structure and adding it to the laminated composite magnetoelectric material, greatly improves the magnetoelectric coupling efficiency, and according to the working mode of longitudinal wave and shear wave, two different acoustic coupling layer's laminated composite magnetoelectric material structures and preparation methods are proposed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laminated composite magnetoelectric material, and particularly relates to a laminated composite magnetoelectric material with an acoustic coupling layer and a preparation method thereof. BACKGROUND

[0002] The laminated composite magnetoelectric material generally has multiple ferroelectricity, including ferroelectricity, ferromagnetism and ferroelasticity, and can realize close coupling of the three ferroelectricity by adjusting an electric field or a magnetic field to generate a magnetoelectric effect. At present, the single-phase magnetoelectric material often has the defects of low Curie temperature or weak magnetoelectric effect, which limits the application range. In contrast, the laminated composite magnetoelectric material has realized its multi-ferroelectricity at room temperature or higher temperature. The laminated composite magnetoelectric material can be divided into 0-3 particle composite type, 2-2 laminated composite type, 1-3 columnar composite type and the like according to its composition structure. The 2-2 laminated composite structure has multiple functions, controllability, high-frequency adjustability and many other advantages, and has been widely applied in the fields of sensing, energy harvesting, device control, communication and the like.

[0003] The laminated composite magnetoelectric material is generally composed of a piezoelectric film at the bottom and a piezomagnetic film at the top, and realizes a magnetoelectric effect or an inverse magnetoelectric effect through stress continuous coupling. In order to expand the application scene range of the laminated composite magnetoelectric material, it is necessary to improve the coupling performance between the piezoelectric film and the piezomagnetic film. The existing technical solutions often design laminated composite magnetoelectric materials with different shapes and structures, and use different vibration modes of acoustic waves including shear waves and longitudinal waves to improve the coupling performance. However, these technical means have certain limitations, because it is necessary to balance the electromagnetic properties and mechanical stability of the material in the design process, which is often challenging. SUMMARY

[0004] In order to overcome the problem in the prior art that the difference in acoustic impedance between the piezoelectric material and the piezomagnetic material causes a large amount of reflection of acoustic waves between the two materials, thereby resulting in low coupling efficiency in the laminated composite magnetoelectric material, the present application provides a laminated composite magnetoelectric material with an acoustic coupling layer, which comprises: an acoustic coupling layer, a piezoelectric layer and a piezomagnetic layer, the characteristic acoustic impedance of the acoustic coupling layer is A, the characteristic acoustic impedance of the piezoelectric layer material is B, and the characteristic acoustic impedance of the piezomagnetic layer material is C, under the condition of B << C or C << B, B < A < C or C < A < B is satisfied.

[0005] Preferably, in the longitudinal wave working mode, the ratio of the acoustic impedance of the piezoelectric layer to the piezomagnetic layer is 5-10; and in the shear wave working mode, the ratio of the acoustic impedance of the piezoelectric layer to the piezomagnetic layer is 10-20.

[0006] Preferably, the acoustic coupling layer and the piezoelectric layer, piezomagnetic layer satisfy a certain function relationship:

[0007] Under the magnetoelectric effect:

[0008]

[0009] Under the inverse magnetoelectric effect:

[0010]

[0011] L - length of the acoustic coupling layer

[0012] ρ - material density of the acoustic coupling layer

[0013] Y1 - elastic modulus of the piezoelectric layer

[0014] L1 - length of the piezoelectric layer

[0015] ρ1 - material density of the piezoelectric layer

[0016] Y2 - elastic modulus of the piezomagnetic layer

[0017] L2 - length of the piezomagnetic layer

[0018] ρ2 - material density of the piezomagnetic layer.

[0019] Preferably, in the longitudinal wave working mode, the acoustic coupling layer of the stacked composite magnetoelectric material from bottom to top is silicon substrate, air cavity, lower electrode, piezoelectric layer, upper electrode, acoustic coupling layer and piezomagnetic layer; in the shear wave working mode, the acoustic coupling layer of the stacked composite magnetoelectric material from bottom to top is silicon substrate, lower electrode, piezoelectric layer, acoustic coupling layer, piezomagnetic layer and upper electrode.

[0020] The second aspect of the present application discloses a preparation method of the stacked composite magnetoelectric material with acoustic coupling layer in the longitudinal wave working mode, which comprises the following steps:

[0021] Step one: using photolithography process to photoetch vertical grooves on the silicon substrate;

[0022] Step two: filling amorphous silicon sacrificial layer in the grooves;

[0023] Step three: using magnetron sputtering method to deposit lower electrode on the surface of the sacrificial layer and etching;

[0024] Step four: using small molecule evaporation method to prepare piezoelectric layer on the surface of the lower electrode;

[0025] Step five: using magnetron sputtering method to deposit upper electrode on the surface of the piezoelectric layer;

[0026] Step six: bonding acoustic coupling layer on the surface of the upper electrode by adhesive;

[0027] Step seven: depositing and etching the magnetic layer on the surface of the acoustic coupling layer by magnetron sputtering method;

[0028] Step eight: releasing the sacrificial layer in the groove to form a cavity and drying.

[0029] Preferably, the preparation of the layered composite magnetoelectric material with acoustic coupling layer in longitudinal wave operation mode should meet the following conditions, including:

[0030] (1) the photoetching process is wet etching or dry etching;

[0031] (2) when preparing the lower electrode by magnetron sputtering method, the sputtering pressure is 0.8-1.2 Pa, the sputtering power is 180-220 W, and the sputtering temperature is room temperature water cooling;

[0032] (3) when preparing the piezoelectric layer by small molecule evaporation method, the evaporation temperature is 150-200℃, the substrate temperature is 20-50℃, and the vacuum degree is 10 -6 ~10 -7 Torr;

[0033] (4) when preparing the upper electrode by magnetron sputtering method, the sputtering atmosphere is argon, the pressure is 0.8-1.2 Pa, the sputtering power is 180-220 W, and the sputtering temperature is room temperature water cooling;

[0034] (5) when depositing the magnetic layer by magnetron sputtering method, the sputtering atmosphere is oxygen, the pressure is 3-5 Pa, the sputtering power is 350-400 W, the substrate temperature is 500-600℃, and after deposition, annealing is carried out, the annealing temperature is 700-750℃;

[0035] (6) after the preparation of the magnetic layer is completed, the device is etched by dry etching process, so that the upper electrode and the lower electrode are exposed, and then the sacrificial layer is released by XeF2.

[0036] Preferably, the preparation of the layered composite magnetoelectric material with acoustic coupling layer in longitudinal wave operation mode should meet the following conditions, including:

[0037] (1) the depth of the groove is 1-3 μm;

[0038] (2) the thickness of the sacrificial layer is equal to the depth of the groove;

[0039] (3) the thickness of the lower electrode is 50-150 nm;

[0040] (4) the thickness of the piezoelectric layer is 175-275 nm;

[0041] (5) the thickness of the upper electrode is 50-150 nm;

[0042] (6) the thickness of the acoustic coupling layer is 500-700 nm;

[0043] (7) the thickness of the magnetostrictive layer is 1-2 μm.

[0044] Preferably, the method for preparing the layered composite magnetoelectric material with acoustic coupling layer in shear wave mode comprises the following steps:

[0045] Step 1: covering part of the silicon substrate with a shielding layer, and depositing the lower electrode on the surface of the silicon substrate by magnetron sputtering;

[0046] Step 2: preparing the piezoelectric layer on the surface of the lower electrode by small molecule evaporation;

[0047] Step 3: depositing the upper electrode on the surface of the piezoelectric layer by magnetron sputtering, and peeling off the shielding layer;

[0048] Step 4: setting the shielding layer on the upper electrode and the exposed area of the silicon substrate respectively, keeping a certain distance between the shielding layers, depositing the acoustic coupling layer on the surface of the shielding layer by magnetron sputtering, and peeling off the shielding layer;

[0049] Step 5: preparing the shielding layer on the upper surface of the upper electrode and the acoustic coupling layer, depositing the magnetostrictive layer by magnetron sputtering, and ensuring that the upper surface of the magnetostrictive layer is flush with the upper surfaces of the acoustic coupling layer and the piezoelectric film;

[0050] Step 6: peeling off the shielding layer, and exposing the surface of the lower electrode by dry etching.

[0051] Preferably, the preparation of the layered composite magnetoelectric material with acoustic coupling layer in shear wave mode should meet the following conditions, including:

[0052] (1) before laying the shielding layer on the silicon substrate, cleaning the surface of the silicon substrate with acetone and ethanol solution, and blowing dry with nitrogen;

[0053] (2) when preparing the lower electrode by magnetron sputtering process, the sputtering pressure is 0.8-1.2 Pa, the sputtering power is 180-220 W, and the sputtering temperature is room temperature water cooling;

[0054] (3) when preparing the piezoelectric layer by small molecule evaporation process, the evaporation temperature is 150-200℃, the substrate temperature is 20-50℃, and the vacuum degree is 10 -6 -10 -7 Torr;

[0055] (4) when preparing the upper electrode by using the magnetron sputtering process, the sputtering pressure is 0.8-1.2 Pa, the sputtering power is 180-220 W, and the sputtering temperature is room temperature water cooling;

[0056] (5) when depositing the pressure magnetic layer by using the magnetron sputtering method, the sputtering atmosphere is oxygen, the pressure is 3-5 Pa, the sputtering power is 350-400 W, the substrate temperature is 500-600 DEG C, and after the deposition is completed, annealing is carried out, and the annealing temperature is 700-750 DEG C.

[0057] Preferably, the preparation of the layered composite magnetoelectric material with the acoustic coupling layer in the shear wave operation mode should meet the following conditions, including:

[0058] (1) the width of the exposed area of the silicon substrate after laying the shielding layer is 130-200 nm;

[0059] (2) the thickness of the lower electrode is 50-150 nm;

[0060] (3) the thickness of the piezoelectric layer is 0.5-2 mu m;

[0061] (4) the thickness of the upper electrode is 50-150 nm;

[0062] (5) the distance between the upper electrode and the shielding layer on the silicon substrate is 320-400 nm;

[0063] (6) the thickness of the acoustic coupling layer is 0.5-2 mu m;

[0064] (7) the thickness of the piezomagnetic layer is 0.5-2 mu m, and the width is 700-900 nm.

[0065] Compared with the prior art, the beneficial effects of the present application are:

[0066] 1. The present application designs an acoustic coupling layer and adds it to the layered composite magnetoelectric material, effectively reduces the resistance of acoustic wave transmission by increasing the acoustic coupling layer in the piezoelectric film and the piezomagnetic film, realizes the reduction of the large reflection of acoustic wave energy between the piezoelectric layer and the piezomagnetic layer, avoids the great loss of acoustic wave energy in the transmission process, and thus improves the efficiency of the magnetoelectric coupling.

[0067] 2. The present application analyzes two different operation modes (longitudinal wave mode and shear wave mode) of the acoustic wave in the composite magnetoelectric material, proposes the transverse insertion mode of the acoustic coupling layer in the longitudinal wave mode and the tangential insertion mode in the shear wave mode, and realizes the impedance matching in the longitudinal wave mode and the shear wave mode. BRIEF DESCRIPTION OF DRAWINGS

[0068] In order to make the technical solutions of the embodiments of the present application or the prior art clearer, the accompanying drawings needed in the embodiments or the prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description only show some embodiments of the present application, and all other embodiments obtained by those of ordinary skill in the art without any creative effort based on the accompanying drawings belong to the protection scope of the present application.

[0069] Figure 1 Structure schematic diagram of the laminated composite magnetoelectric material in the longitudinal wave working mode;

[0070] Figure 2 Structure schematic diagram of the laminated composite magnetoelectric material in the shear wave working mode;

[0071] Figure 3a Process flow chart of the laminated composite magnetoelectric material in the longitudinal wave working mode;

[0072] Figure 4a Process flow chart of the laminated composite magnetoelectric material in the shear wave working mode;

[0073] Wherein, 1 is a silicon substrate, 2 is a sacrifice layer, 3 is a lower electrode layer, 4 is a piezoelectric layer, 5 is an upper electrode layer, 6 is an acoustic coupling layer, 7 is a piezomagnetic layer, 8 is a shielding layer, and 9 is a cavity. DETAILED DESCRIPTION

[0074] The technical solutions of the present application will be described clearly and completely in combination with specific embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without any creative effort belong to the protection scope of the present application.

[0075] Since the laminated composite magnetoelectric material is usually composed of two materials, i.e. piezoelectric film and pieomagnetic film, the piezoelectric film can be regarded as a piezoelectric transducer, and the pieomagnetic film can be regarded as a pieomagnetic transducer. There is no patent and technology in the prior art for impedance matching of the two materials in the laminated composite magnetoelectric material. At present, in order to improve the coupling performance of the laminated composite magnetoelectric material, the existing technology usually adjusts the formation and structure of the laminated composite magnetoelectric material to reduce the formation of stray waves of sound waves and reduce the leakage of sound wave energy, which is often challenging because it usually needs to consider the balance between the electromagnetic properties and mechanical stability of the material. Researchers have achieved acoustic impedance matching of piezoelectric ultrasonic transducers and objects to be measured, but the technology of adding an acoustic coupling layer to the laminated composite magnetoelectric material is often overlooked. For various piezoelectric materials and pieomagnetic materials with different acoustic impedances, the difference in acoustic impedance often causes a large amount of reflection of sound waves between the two materials, increases the transmission resistance of sound waves, and reduces the magnetoelectric coupling rate of the laminated composite material.

[0076] The applicant of the present application has long observed, summarized, experimented and made sufficient theoretical calculations, and proposes a laminated composite magnetoelectric material with an acoustic coupling layer and a preparation method thereof. By adding an acoustic coupling layer of different materials to the laminated composite magnetoelectric material according to the piezoelectric layer and the pieomagnetic layer with different acoustic impedances, and according to different acoustic wave working modes, a laminated composite magnetoelectric material with an acoustic coupling layer and a preparation method thereof are proposed, which effectively reduces the reflection of sound waves between the piezoelectric layer and the pieomagnetic layer.

[0077] A laminated composite magnetoelectric material with an acoustic coupling layer, comprising an acoustic coupling layer, a piezoelectric layer and a pieomagnetic layer, the characteristic acoustic impedance of the acoustic coupling layer is A, the characteristic acoustic impedance of the piezoelectric layer material is B, and the characteristic acoustic impedance of the pieomagnetic layer material is C, under the condition of B << C or C << B, B < A < C or C < A < B is satisfied.

[0078] Specifically, in the longitudinal wave working mode, the ratio of the acoustic impedance of the piezoelectric layer to the pieomagnetic layer is 5-10; in the shear wave working mode, the ratio of the acoustic impedance of the piezoelectric layer to the pieomagnetic layer is 10-20.

[0079] Specifically, the acoustic coupling layer, the piezoelectric layer and the pieomagnetic layer satisfy a certain functional relationship.

[0080] Under the magnetoelectric effect:

[0081]

[0082] Under the inverse magnetoelectric effect:

[0083]

[0084] L - length of the acoustic coupling layer

[0085] p - material density of the acoustic coupling layer

[0086] Y1 - elastic modulus of the piezoelectric layer

[0087] L1 - length of the piezoelectric layer

[0088] p1 - material density of the piezoelectric layer

[0089] Y2 - elastic modulus of the magnetostrictive layer

[0090] L2 - length of the magnetostrictive layer

[0091] p2 - material density of the magnetostrictive layer.

[0092] Specifically, in the longitudinal wave operating mode, the layered composite magnetoelectric material with the acoustic coupling layer has a structure from bottom to top as follows: a silicon substrate, an air cavity, a lower electrode, a piezoelectric layer, an upper electrode, an acoustic coupling layer, and a magnetostrictive layer; in the shear wave operating mode, the layered composite magnetoelectric material with the acoustic coupling layer has a structure from bottom to top as follows: a silicon substrate, a lower electrode, a piezoelectric layer, an acoustic coupling layer, a magnetostrictive layer, and an upper electrode.

[0093] Specifically, the piezoelectric layer is a polyvinylidene fluoride (PVDF) film, with a thickness of 225 nm and a lateral area of 100 μm x 100 μm in the longitudinal wave mode, and with a lateral width of 130 nm and a tangential area of 100 μm x 100 μm in the shear wave mode.

[0094] Specifically, the magnetostrictive layer is a yttrium iron garnet (YIG) film, with a thickness of 1.3 μm and a lateral area of 100 μm x 100 μm in the longitudinal wave mode, and with a lateral width of 800 nm and a tangential area of 100 μm x 100 μm in the shear wave mode.

[0095] Specifically, the acoustic coupling layer in the longitudinal wave operating mode is annealed magnesium metal, with a thickness of 600 nm and a lateral area of 100 μm x 100 μm.

[0096] Specifically, the acoustic coupling layer in the shear wave operating mode is Al, with a lateral width of 320 nm and a tangential area of 100 μm x 100 μm.

[0097] The following respectively gives a specific embodiment 1 of preparation of the layered composite magnetoelectric material with the acoustic coupling layer in the longitudinal wave operating mode and an embodiment 2 of preparation of the layered composite magnetoelectric material with the acoustic coupling layer in the shear wave operating mode.

[0098] Reference Figure 3a ~i, embodiment 1:

[0099] S1, a groove is photoetched on the surface of a silicon substrate by dry etching, the depth of the groove being 1 μm.

[0100] S2, a layer of amorphous silicon is sputter-deposited as a sacrificial layer in the groove, the thickness of the sacrificial layer being 1 μm.

[0101] S3, a layer of metal Mo is sputter-deposited as a lower electrode layer on the surface of the silicon substrate by magnetron sputtering under the conditions of a sputtering pressure of 1 Pa, a sputtering power of 220 W and water cooling at a sputtering temperature of 24°C, the thickness of the lower electrode layer being 100 nm.

[0102] S4, a layer of piezoelectric layer is evaporated on the surface of the lower electrode by small molecule evaporation method under the conditions of an evaporation temperature of 170°C, a substrate temperature of 40°C and a vacuum degree of 10 -6 Torr, the piezoelectric layer material being PVDF, the thickness being 225 nm.

[0103] S5, a layer of upper electrode metal Mo is deposited on the surface of the piezoelectric layer by magnetron sputtering under the conditions of a sputtering atmosphere of argon, a sputtering pressure of 1 Pa, a sputtering power of 220 W and water cooling at a substrate temperature of 24°C, the sputtering thickness being 100 nm.

[0104] S6, the annealed metal magnesium is bonded to the surface of the upper electrode layer as an acoustic coupling layer by adhesive, the thickness being 600 nm.

[0105] S7, a layer of magnetostrictive layer is deposited on the surface of the acoustic coupling layer by magnetron sputtering under the conditions of a sputtering atmosphere of oxygen, a sputtering pressure of 4 Pa, a sputtering power of 400 W and a substrate temperature of 550°C, the magnetostrictive layer material being YIG, the deposition thickness being 1.3 μm. Annealing is performed after deposition, the annealing temperature being 700°C.

[0106] S8, dry etching is performed on one end of the layered composite magnetoelectric material with acoustic coupling layer, so that the lower electrode and the upper electrode layer are exposed.

[0107] S9, the sacrificial layer is released by XeF2, forming a closed cavity and drying.

[0108] Reference Figure 4a ~h, Example 2:

[0109] S1, the surface of a silicon substrate is cleaned by using acetone and ethanol solution, and then the surface of the silicon substrate is blown by nitrogen until no solution residue is left.

[0110] S2, an adhesive is used to paste a shielding layer on the surface of the silicon substrate, so that the width of the exposed area on the silicon substrate is 130 nm.

[0111] S3, under the conditions of sputtering pressure of 1 Pa, sputtering power of 220 W, and water-cooling sputtering temperature of 24℃, a layer of metal Mo is sputtered on the surface of the exposed area of the silicon substrate and the shielding layer as a lower electrode layer by using a magnetron sputtering process, and the thickness of the lower electrode layer is 100 nm.

[0112] S4, under the conditions of evaporation temperature of 180℃, substrate temperature of 50℃, and vacuum degree of 10 -7 Torr, a piezoelectric layer is evaporated on the surface of the lower electrode by using a small molecule evaporation process, the piezoelectric layer material is PVDF, and the thickness is 1 μm.

[0113] S5, under the conditions of sputtering pressure of 1 Pa, sputtering power of 220 W, and water-cooling sputtering temperature of 24℃, a layer of metal Mo is deposited on the surface of the piezoelectric layer as an upper electrode by using a magnetron sputtering method, and the thickness of the upper electrode is 100 nm.

[0114] S6, the shielding layer is peeled off, and a shielding layer is arranged on the upper electrode and the exposed area of the silicon substrate respectively, and the distance between the shielding layers is 320 nm.

[0115] S7, under the conditions of sputtering pressure of 1 Pa, sputtering power of 220 W, and water-cooling sputtering temperature of 24℃, a layer of metal Al is deposited on the gap between the shielding layers and the shielding layers as an acoustic coupling layer by using a magnetron sputtering method, and the thickness of the acoustic coupling layer is 1.1 μm.

[0116] S8, the shielding layer is peeled off, and a layer of YIG is deposited on the surface of the upper electrode and the acoustic coupling layer as a magnetostrictive layer by using a magnetron sputtering method under the conditions of sputtering atmosphere of oxygen, pressure of 5 Pa, sputtering power of 400 W, and substrate temperature of 600℃, and the thickness of the magnetostrictive layer is 1.1 μm, and the width is 800 nm. After the deposition, annealing is performed at a temperature of 700℃.

[0117] S9, the shielding layer is peeled off, and the lower electrode is exposed by using a dry etching process.

[0118] The above further describes the present application by means of specific embodiments, but it should be understood that the specific description herein should not be understood as limiting the essence and scope of the present application, and various modifications made to the above embodiments by those skilled in the art after reading the description all belong to the scope protected by the present application.

[0119] The application inserts an acoustic coupling layer in a laminated composite magnetoelectric material, increases the acoustic wave energy transferred into the piezomagnetic layer by reducing the acoustic wave resistance, and further improves the magnetoelectric coupling efficiency. By analyzing two different working modes (longitudinal wave mode and shear wave mode) of acoustic waves in the composite magnetoelectric material, the acoustic coupling layer is inserted transversely in the longitudinal wave mode and tangentially in the shear wave mode, and impedance matching in the longitudinal wave mode and the shear wave mode is realized.

[0120] The shear wave speed and longitudinal wave speed of the piezoelectric film PVDF are 627 m / s and 2140 m / s, respectively, and the transverse acoustic impedance and longitudinal acoustic impedance are 1.12×10 6 kg / m 2 s and 3.81×10 6 kg / m 2 s, respectively. The shear wave speed and longitudinal wave speed of the piezomagnetic film YIG are 3840 m / s and 5000 m / s, respectively, and the transverse acoustic impedance and longitudinal acoustic impedance are 2×10 7 kg / m 2 s and 2.6×10 7 kg / m 2 s, respectively.

[0121] According to the acoustic wave transmission coefficient calculation formula of the two materials: t=4Z1Z2 / (Z1+Z2) 2 (Z1 and Z2 are the acoustic impedance of the piezoelectric film and the piezomagnetic film, respectively), the transmission coefficients of PVDF and YIG in the shear wave mode and the longitudinal wave mode are 0.2 and 0.44, respectively. The acoustic wave is reflected at the interface between the two materials, which is one of the reasons for the low composite magnetoelectric coupling efficiency.

[0122] In the shear wave mode, the material of the acoustic coupling layer is selected as metal Al, and the transverse acoustic impedance is 8.2×10 6 kg / m 2 s. In the longitudinal wave mode, the material of the acoustic coupling layer is selected as annealed magnesium, and the longitudinal acoustic impedance is 1×10 7 kg / m 2 s. Similarly, the acoustic wave transmission coefficient formula between the three materials is used: t'=16Z1Z2Zc 2 / [(Z1+Z c )(Z c +Z2)] 2 (where Z cFor the acoustic impedance of the acoustic coupling layer, the transmission coefficients of the shear wave and longitudinal wave modes can be calculated as 0.35 and 0.64, respectively, and the energy transmission rates are increased by 1.75 and 1.45 times, respectively. It is clear that the insertion of the acoustic coupling layer in the composite magnetoelectric material improves the transmission rate of the acoustic wave, and more acoustic energy means higher coupling efficiency.

Claims

1. A laminated composite magnetoelectric material with an acoustic coupling layer, comprising an acoustic coupling layer, a piezoelectric layer, and a piezomagnetic layer. The characteristic acoustic impedance of the acoustic coupling layer is A, the characteristic acoustic impedance of the piezoelectric layer material is B, and the characteristic acoustic impedance of the piezomagnetic layer material is C. Under the condition of B << C or C << B, B < A < C or C < A < B is satisfied; The following functional relationships are satisfied between the acoustic coupling layer and the piezoelectric layer and the piezomagnetic layer: Under the magnetoelectric effect: Under the inverse magnetoelectric effect: in: L - The length of the acoustic coupling layer ρ - The material density of the acoustic coupling layer Y1 - The elastic modulus of the piezoelectric layer L1 - The length of the piezoelectric layer ρ1 - The material density of the piezoelectric layer Y2 - The elastic modulus of the piezomagnetic layer L2 - The length of the piezomagnetic layer ρ2 - The material density of the piezomagnetic layer.

2. The multilayered composite magnetoelectric material with an acoustic coupling layer according to claim 1, characterized in that, In the longitudinal wave working mode, the ratio of the acoustic impedance of the piezoelectric layer to that of the piezomagnetic layer is 5 - 10; in the shear wave working mode, the ratio of the acoustic impedance of the piezoelectric layer to that of the piezomagnetic layer is 10 - 20.

3. The multilayered composite magnetoelectric material with an acoustic coupling layer according to claim 1, characterized in that, In the longitudinal wave working mode, the laminated composite magnetoelectric material with an acoustic coupling layer includes a substrate, an air cavity, a lower electrode, a piezoelectric layer, an upper electrode, an acoustic coupling layer, and a piezomagnetic layer stacked in sequence; In the shear wave working mode, the laminated composite magnetoelectric material with an acoustic coupling layer includes a substrate, a lower electrode, a piezoelectric layer, an acoustic coupling layer, a piezomagnetic layer, and an upper electrode stacked in sequence.

4. A method for preparing a multilayered composite magnetoelectric material with an acoustic coupling layer according to any one of claims 1 to 3, characterized in that, The preparation method of the laminated composite magnetoelectric material with an acoustic coupling layer in the longitudinal wave working mode includes: Step A: A groove is etched on the substrate, and a sacrificial layer is formed in the groove; Step B: A lower electrode is deposited on the surface of the sacrificial layer; Step C: A piezoelectric layer is prepared on the surface of the lower electrode; Step D: An upper electrode is deposited on the surface of the piezoelectric layer; Step E: An acoustic coupling layer is set on the surface of the upper electrode; Step F: A piezomagnetic layer is deposited on the upper surface of the acoustic coupling layer by magnetron sputtering; Step G: The sacrificial layer is made to form a cavity and dried.

5. The method for preparing a multilayered composite magnetoelectric material with an acoustic coupling layer according to claim 4, characterized in that, When preparing the laminated composite magnetoelectric material with an acoustic coupling layer in the longitudinal wave working mode, the following conditions should be satisfied, including: In Step A, the process of forming a groove on the substrate is a photolithography process, and the photolithography process is wet etching or dry etching; In Step B, the process of depositing the lower electrode is magnetron sputtering. When preparing the lower electrode by magnetron sputtering, the sputtering pressure is 0.8 - 1.2 Pa, the sputtering power is 180 - 220 W, and the sputtering temperature is 20 - 30 °C; In step C, the piezoelectric layer is prepared by small molecule evaporation deposition. When preparing the piezoelectric layer using this method, the deposition temperature is 150℃~200℃, the substrate temperature is 20℃~50℃, and the vacuum degree is 10. -6 ~10 -7 Torr; In Step D, the method of preparing the upper electrode is magnetron sputtering. When preparing the upper electrode by magnetron sputtering, the sputtering atmosphere is argon, the pressure is 0.8 - 1.2 Pa, the sputtering power is 180 - 220 W, and the sputtering temperature is 20 - 30 °C; In Step F, the method of preparing the piezomagnetic layer is magnetron sputtering. When depositing the piezomagnetic layer by magnetron sputtering, the sputtering atmosphere is oxygen, the pressure is 3 - 5 Pa, the sputtering power is 350 - 400 W, the substrate temperature is 500 - 600 °C, and annealing is performed after deposition, and the annealing temperature is 700 - 750 °C; In step G, after the piezomagnetic layer is prepared, the device is etched using a dry etching process to expose the upper and lower electrodes, and then the sacrificial layer is released using XeF2.

6. The method for preparing a multilayered composite magnetoelectric material with an acoustic coupling layer according to claim 5, characterized in that, The laminated composite magnetoelectric material with acoustic coupling layer should meet the following conditions during fabrication in longitudinal wave mode, including: (1) The depth of the groove is 1~3μm; (2) The thickness of the sacrificial layer is equal to the depth of the groove; (3) The thickness of the lower electrode is 50~150nm; (4) The thickness of the piezoelectric layer is 175~275nm; (5) The thickness of the upper electrode is 50~150nm; (6) The thickness of the acoustic coupling layer is 500~700nm; (7) The thickness of the piezomagnetic layer is 1~2μm.

7. A method for preparing a multilayered composite magnetoelectric material with an acoustic coupling layer according to any one of claims 1 to 3, characterized in that, The preparation method of the stacked composite magnetoelectric material with acoustic coupling layer in shear wave operating mode includes: Step A: Cover part of the substrate with a shielding layer and deposit the lower electrode on the substrate surface; Step B: Prepare a piezoelectric layer on the surface of the lower electrode; Step C: Deposit an electrode on the surface of the piezoelectric layer and peel off the shielding layer; Step D: A shielding layer is provided on the exposed area of ​​the upper electrode and the substrate respectively, and the shielding layers are spaced a certain distance apart. After depositing an acoustic coupling layer on the surface of the shielding layer, the shielding layer is peeled off. Step E: Prepare a shielding layer on the upper surface of the upper electrode and the acoustic coupling layer, and deposit a piezomagnetic layer to ensure that the upper surface of the piezomagnetic layer is flush with the upper surface of the acoustic coupling layer and the piezoelectric layer; Step F: Peel off the shielding layer to expose the lower electrode.

8. The method for preparing a multilayered composite magnetoelectric material with an acoustic coupling layer according to claim 7, characterized in that, The laminated composite magnetoelectric material with acoustic coupling layer should meet the following conditions during fabrication in shear wave mode, including: Before step A, the surface of the silicon substrate is cleaned with acetone and ethanol solution and dried with nitrogen gas before the shielding layer is laid on the silicon substrate. In step A, the method for preparing the lower electrode is magnetron sputtering. When preparing the lower electrode using magnetron sputtering, the sputtering pressure is 0.8~1.2 Pa, the sputtering power is 180~220 W, and the sputtering temperature is 20~30℃. In step B, the piezoelectric layer is prepared by small molecule evaporation deposition. When preparing the piezoelectric layer using this process, the deposition temperature is 150℃~200℃, the substrate temperature is 20℃~50℃, and the vacuum degree is 10. -6 ~10 -7 Torr; In step C, the method for preparing the upper electrode is magnetron sputtering. When preparing the upper electrode using magnetron sputtering, the sputtering pressure is 0.8~1.2 Pa, the sputtering power is 180~220 W, and the sputtering temperature is 20~30℃. In step D, the method for depositing the acoustic coupling layer is magnetron sputtering; In step E, the method for preparing the piezomagnetic layer is magnetron sputtering. When depositing the piezomagnetic layer using magnetron sputtering, the sputtering atmosphere is oxygen, the pressure is 3~5 Pa, the sputtering power is 350~400 W, the substrate temperature is 500~600 °C, and after deposition, annealing is performed at a temperature of 700~750 °C. In step F, the method for exposing the lower electrode is dry etching.

9. The method for preparing a multilayered composite magnetoelectric material with an acoustic coupling layer according to claim 8, characterized in that, The laminated composite magnetoelectric material with acoustic coupling layer should meet the following conditions during fabrication in shear wave mode, including: (1) The width of the exposed area of ​​the silicon substrate after the shielding layer is laid is 130~200nm; (2) The thickness of the lower electrode is 50~150nm; (3) The thickness of the piezoelectric layer is 0.5~2μm; (4) The thickness of the upper electrode is 50~150nm; (5) The distance between the upper electrode and the shielding layer on the silicon substrate is 320~400nm; (6) The thickness of the acoustic coupling layer is 0.5~2μm; (7) The thickness of the piezomagnetic layer is 0.5~2μm and the width is 700~900nm.

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