Reff wave photonic crystal based on lithium tantalate single crystal film

Abstract

The invention relates to the technical field of surface acoustic wave phononic crystals, and discloses a lithium tantalate single crystal film-based Left wave phononic crystal, the Left wave phononic crystal comprises a functional substrate and a piezoelectric film layer attached to the upper surface of the functional substrate, and the functional substrate comprises a plurality of layers of substrates with a high sound velocity or temperature compensation function; the piezoelectric thin film layer is a lithium tantalate single crystal thin film, and a micropore or microcolumn structure is constructed on the lithium tantalate single crystal thin film to form a phononic crystal. According to the invention, the phononic crystal is formed by constructing the micropores / columns on the lithium tantalate single crystal film, the structure is simple, preparation and integration are easy, a large-bandwidth Loff wave forbidden band can be provided, and technical support is provided for realizing a miniaturized and high-performance Loff wave device.

Description

Technical Field

[0001] The invention relates to the technical field of surface acoustic wave phononic crystals, in particular to Love wave phononic crystals based on lithium tantalate single crystal films. Background Art

[0002] Phononic crystals are a type of artificial structural material that forms a lattice that regulates the propagation of sound waves through periodic arrangement of solid materials. The role of phononic crystals in the field of acoustics is similar to that of photonic crystals in the field of optics. They cause diffraction and interference of sound waves through periodic structures, thereby generating phononic band gaps. By designing the structure of solid phononic crystals, the propagation path, speed and attenuation of sound waves can be precisely controlled. This feature can be used to isolate noise of specific frequencies or design acoustic filters.

[0003] Surface acoustic waves refer to elastic waves that propagate on the surface of a material. The propagation of surface acoustic waves is mainly concentrated in the surface area of ​​the material. Common types of surface acoustic waves are Rayleigh waves and Love waves. Among them, Love waves are a horizontal shear wave, whose vibration direction is perpendicular to the propagation direction but parallel to the surface of the propagation medium, which makes Love waves have lower energy leakage in the direction perpendicular to the propagation surface. In addition, the wave speed of Love waves is usually faster than that of Rayleigh waves, and is more suitable for the research and development of high-frequency surface acoustic waves. Therefore, Love waves are also often used in high-frequency, low-loss surface acoustic wave devices. Since the energy band of phononic crystals has a band gap, it can effectively localize sound. Therefore, phononic crystals can be used to realize the energy band and band gap of Love waves, solve the problem of Love wave localization in continuous media, and provide technical support for the preparation of more miniaturized and higher-performance Love wave resonators and filters.

[0004] In addition, among the piezoelectric materials used in surface acoustic wave devices, lithium tantalate has shown great advantages, including high temperature stability, high acid and alkali corrosion resistance, wide frequency range, and mature preparation process. Under such technical background, how to construct Love wave phononic crystals with the help of a material system based on lithium tantalate, and then realize miniaturized and high-performance Love wave devices, has become a technical problem that needs to be solved urgently in this field. Summary of the invention

[0005] The purpose of the present invention is to provide a Love wave phononic crystal based on a lithium tantalate single crystal film. The phononic crystal is formed by constructing micropores / columns on the lithium tantalate single crystal film. The phononic crystal has a simple structure and is easy to prepare and integrate. It can provide a Love wave bandgap with a large bandwidth, and provide technical support for realizing miniaturized and high-performance Love wave devices.

[0006] To achieve the above object, the present invention provides the following solutions: A Love wave phononic crystal based on a lithium tantalate single crystal film, the Love wave phononic crystal comprising a functional substrate and a piezoelectric film layer attached to the upper surface of the functional substrate, the functional substrate comprising several layers of substrates having a high sound velocity or temperature compensation function; The piezoelectric film layer is a lithium tantalate single crystal film, and a micropore or microcolumn structure is constructed on the lithium tantalate single crystal film to form a phononic crystal.

[0007] Furthermore, the material of the functional substrate is one (one layer) or more (multilayers) of (4-H or 6-H) silicon carbide, sapphire, (AT cut or BT cut or SC cut) quartz, diamond, silicon dioxide, polycrystalline silicon, and single crystal silicon.

[0008] Furthermore, the tangent direction of the lithium tantalate single crystal film is one of the Y-cuts, including 0°Y, 36°Y, 42°Y, 50°Y, 64°Y, and 128°Y. For example, in Examples 1 and 2, the tangent direction of the lithium tantalate is 42°Y.

[0009] Furthermore, the microporous structure is formed by etching a periodic or non-periodic hole or groove structure on the surface of the lithium tantalate single crystal film; and the microcolumn structure is formed by growing a periodic or non-periodic column structure on the surface of the lithium tantalate single crystal film.

[0010] Furthermore, the cross-sectional shapes of the hole or groove structure and the column structure are one or more combinations of circular, elliptical, triangular, polygonal or other irregular shapes.

[0011] Furthermore, the material of the column structure is lithium tantalate, silicon, silicon dioxide, silicon nitride or a metal material, and the metal material includes aluminum, copper, nickel, and chromium; and the height of the column structure is 0-1000 microns.

[0012] Furthermore, the depth of the hole or groove structure is less than the thickness of the lithium tantalate single crystal film, equal to the thickness of the lithium tantalate single crystal film, or greater than the thickness of the lithium tantalate single crystal film (i.e., the phononic crystal structure is located not only in the lithium tantalate single crystal film, but also in the functional substrate material).

[0013] Furthermore, the lattice of the phononic crystal is a triangular lattice, a tetragonal lattice, a honeycomb lattice, a cage lattice or other lattices with symmetry, and the lattice period ranges from 0 to 1000 microns.

[0014] Furthermore, the lithium tantalate single crystal film has a thickness of 0-10 microns.

[0015] Furthermore, the phononic crystal is a multi-layer one-dimensional phononic crystal or a two-dimensional phononic crystal, and the number of layers is 1-1000.

[0016] According to the specific embodiments provided by the present invention, the Love wave phononic crystal based on lithium tantalate single crystal film provided by the present invention discloses the following technical effects: based on the lithium tantalate single crystal film attached to the upper surface of the functional substrate, the micropores / columns are constructed to form the phononic crystal, which has a simple structure and is easy to prepare and integrate; the phononic crystal has a wider directional band gap of the Love wave, and the phononic crystal can be used to achieve efficient suppression of the Love wave, which is beneficial to the preparation of a surface acoustic wave resonator or filter based on the Love wave; without affecting the heat dissipation and working bandwidth of the surface acoustic wave device, the surface acoustic wave phononic crystal provided by the present invention can achieve a higher quality factor, a lower insertion loss and a smaller device size, which is of great significance for realizing a new generation of stable, high-performance and miniaturized microwave acoustic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0018] Figure 1 It is a schematic diagram of the top view structure of the Love wave phononic crystal based on the lithium tantalate single crystal film of the present invention; Figure 2 Schematic diagram of the cross section of the Love wave hole type phononic crystal along the section line AA' in Example 1 of the present invention; Figure 3 Schematic diagram of the cross section of the Love wave column type phononic crystal along the section line AA' in Example 1 of the present invention; Figure 4 The surface acoustic wave band gap structure of the Love wave hole type phononic crystal in the 42°Y direction in Example 1 of the present invention, wherein (a) is a schematic diagram of the Love mode band gap along the Г-X direction of the Brillouin zone of the phononic crystal, and (b) and (c) are respectively a top view and a front view of the acoustic field distribution in the phononic crystal unit cell; Figure 5 Schematic diagram of energy bands and transmission spectra corresponding to the Love wave phononic crystal based on lithium tantalate single crystal thin film in Example 1 of the present invention; Figure 6 Schematic diagram of the cross section of the Love wave hole type phononic crystal along the section line AA' in Example 2 of the present invention; Figure 7 Schematic diagram of the cross section of the Love wave column type phononic crystal along the section line AA' in Example 2 of the present invention; Figure 8The surface acoustic wave band gap structure of the Love wave hole type phononic crystal in the 42°Y direction in Example 2 of the present invention, wherein (a) is a schematic diagram of the Love mode band gap along the Г-X direction of the Brillouin zone of the phononic crystal, and (b) and (c) are respectively a top view and a front view of the acoustic field distribution in the phononic crystal unit cell; Fig. 9 Schematic diagram of energy bands and transmission spectra corresponding to the Love wave phononic crystal based on lithium tantalate single crystal thin film in Example 2 of the present invention; Fig.10 Schematic diagram of the cross section of the Love wave hole type phononic crystal along the section line AA' in Example 3 of the present invention; Fig.11 Schematic diagram of the cross section of the Love wave column type phononic crystal along the section line AA' in Example 3 of the present invention; Fig.12 The surface acoustic wave band gap structure of the Love wave hole type phononic crystal in the 42°Y direction in Example 3 of the present invention, wherein (a) is a schematic diagram of the Love mode band gap along the Г-X direction of the Brillouin zone of the phononic crystal, and (b) and (c) are respectively a top view and a front view of the acoustic field distribution in the phononic crystal unit cell; Fig.13 Schematic diagram of the energy band and transmission spectrum corresponding to the Love wave phononic crystal based on lithium tantalate single crystal film in Example 3 of the present invention.

[0019] Description of reference numerals: 1, microporous phononic crystal; 1', microcolumn phononic crystal; 2, piezoelectric film layer; 3, 4, 5, 6, functional substrate (one or more layers of substrate that can achieve high sound velocity or temperature compensation function). DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] In the description of invention patents, it is necessary to understand that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", "center", "longitudinal", "lateral", "vertical", "horizontal", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. When an element is referred to as being "fixed to" another element, it may be directly on the other element or there may also be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time.

[0022] The purpose of the present invention is to design a Love wave phononic crystal with a simple structure, which is easy to prepare and integrate and can provide a Love wave bandgap with a large bandwidth.

[0023] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] like Figure 1 , Figure 2 , Figure 3 , Figure 6 , Figure 7 , Fig.10 , Fig.11 As shown, the present invention provides a Love wave phononic crystal based on a lithium tantalate single crystal film, comprising a functional substrate and a piezoelectric film layer 2 attached to the upper surface of the functional substrate, wherein the functional substrate comprises several layers (i.e., one or more layers) of substrates having a high sound velocity or temperature compensation function, such as Figure 2 and Figure 3 Functional substrate 3 to functional substrate 5, and Figure 6 and Figure 7 Functional base 6 in; The piezoelectric film layer 2 is a lithium tantalate single crystal film, and a micropore or microcolumn structure is constructed on the lithium tantalate single crystal film to form a phononic crystal.

[0025] For example, the material of the functional substrate is one (one layer) or more (multiple layers) of (4-H or 6-H) silicon carbide, sapphire, (AT cut or BT cut or SC cut) quartz, diamond, silicon dioxide, polycrystalline silicon, and single crystal silicon. Different layers of the substrate may use different materials.

[0026] Specifically, the tangent direction of the lithium tantalate single crystal film is one of the Y-cuts, including 0°Y, 36°Y, 42°Y, 50°Y, 64°Y, and 128°Y. For example, in embodiments 1 and 2, the tangent direction of the lithium tantalate is 42°Y. For example, the thickness of the lithium tantalate single crystal film is 0-10 microns.

[0027] For example, the microporous structure is formed by etching a periodic or non-periodic hole or groove structure on the surface of the lithium tantalate single crystal film; the microcolumn structure is formed by growing a periodic or non-periodic column structure on the surface of the lithium tantalate single crystal film.

[0028] The cross-sectional shapes of the hole or groove structure and the column structure are one or more combinations of circular, elliptical, triangular, polygonal or other irregular shapes. The polygonal shapes include quadrilaterals (squares, rhombuses, rectangles), pentagons and hexagons.

[0029] The material of the column structure is lithium tantalate (the same source as the piezoelectric film layer), silicon, silicon dioxide, silicon nitride or metal material, and the metal material includes aluminum, copper, nickel, and chromium; the height of the column structure is 0-1000 microns.

[0030] The depth of the hole or groove structure can be less than the thickness of the lithium tantalate single crystal film, equal to the thickness of the lithium tantalate single crystal film, or greater than the thickness of the lithium tantalate single crystal film (that is, the phononic crystal structure is not only located in the lithium tantalate single crystal film, but also in the functional substrate material).

[0031] For example, the lattice of the phononic crystal is a triangular lattice, a tetragonal lattice, a honeycomb lattice, a kagome lattice or other lattices with symmetry, and the lattice period ranges from 0 to 1000 micrometers.

[0032] For example, the phononic crystal is a multi-layer one-dimensional phononic crystal or a two-dimensional phononic crystal, and the number of layers is 1-1000.

[0033] Figure 1 A top view of a Love wave phononic crystal based on a lithium tantalate single crystal film provided in Example 1 and Example 2 of the present invention.

[0034] Example 1 In this embodiment 1, in one implementation mode, the phononic crystal is formed by etching periodic or non-periodic holes or groove structures on the surface of the lithium tantalate single crystal film. The lattice of the phononic crystal is a tetragonal lattice with C4 symmetry, and the lattice period is 1.5 microns. The etched hole structure forms a microporous phononic crystal 1. The shape of the micropore is circular, that is, a circular hole, and the diameter of the circular hole is 1 micron and the depth is 600 nanometers, forming a Love wave hole type phononic crystal. The cross-sectional view of the Love wave hole type phononic crystal along the section line A-A' is shown in FIG. Figure 2 shown.

[0035] In this embodiment 1, the thickness of the lithium tantalate single crystal film is 600 nanometers, that is, the micropore depth is equal to the thickness of the lithium tantalate single crystal film. The tangent direction of the lithium tantalate is 42° in the Y direction. Substrate 3-substrate 5 constitute a functional substrate, wherein substrate 3 is 500 nanometers thick silicon dioxide, substrate 4 is 1 micron thick polycrystalline silicon, and substrate 5 is single crystal silicon with a (100) crystal orientation.

[0036] Alternatively, another embodiment, such as Figure 3 As shown, the phononic crystal is formed by growing a periodic or non-periodic column structure on the surface of the lithium tantalate single crystal film. The column structure forms a micro-column phononic crystal 1', the micro-column is a cylinder, the cylinder height is 50 nanometers, the material is aluminum, the lattice period is 1.5 microns, the cylinder diameter is 1 micron, forming a Love wave column type phononic crystal. For the Love wave column type phononic crystal, its cross-sectional view along the section line A-A' is as follows Figure 3 shown.

[0037] The microporous phononic crystal in Example 1 has a Love mode bandgap along the Г-X direction of the Brillouin zone of the phononic crystal, and the bandgap range is 0.942-1.482 GHz. Figure 4 As shown in (a). Love waves are horizontal shear waves, the acoustic energy is mainly distributed on the substrate surface, and the wave vibration direction is perpendicular to the wave propagation direction. In Example 1, the top view and the front view of the acoustic field distribution in the phononic crystal cell are shown as follows: Figure 4 As shown in (b) and (c).

[0038] For the microporous phononic crystal in Example 1, the energy band and transmission spectrum of the Love wave phononic crystal are as follows: Figure 5 shown.

[0039] Example 2 In this embodiment 2, in one implementation mode, the phononic crystal is formed by etching periodic or non-periodic holes or groove structures on the surface of the lithium tantalate single crystal film. The lattice of the phononic crystal is a tetragonal lattice with C4 symmetry, and the lattice period is 1.5 microns. The etched hole structure forms a microporous phononic crystal 1. The shape of the micropore is circular, that is, a circular hole, and the diameter of the circular hole is 1 micron and the depth is 300 nanometers, forming a Love wave hole type phononic crystal. The cross-sectional view of the Love wave hole type phononic crystal along the section line A-A' is shown in FIG. Figure 6 shown.

[0040] In this embodiment 2, the lithium tantalate single crystal film has a thickness of 300 nanometers, and the tangent direction of the lithium tantalate is 42° in the Y direction. A layer of substrate 6 constitutes a functional substrate, wherein the substrate 6 is a high-acoustic-velocity substrate, and its material is 6-H silicon carbide, and its thickness is 9.7 micrometers.

[0041] Alternatively, another embodiment, such as Figure 7 As shown, the phononic crystal is formed by growing a periodic or non-periodic column structure on the surface of the lithium tantalate single crystal film. The column structure forms a micro-column phononic crystal 1', the micro-column is a cylinder, the cylinder height is 50 nanometers, the material is aluminum, the lattice period is 1.5 microns, the cylinder diameter is 1 micron, forming a Love wave column type phononic crystal. For the Love wave column type phononic crystal, its cross-sectional view along the section line A-A' is as follows Figure 7 shown.

[0042] The microporous phononic crystal in Example 2 has a Love mode bandgap along the Г-X direction of the Brillouin zone of the phononic crystal, and the bandgap range is 1.714-2.125 GHz. Figure 8 As shown in (a). Love waves are horizontal shear waves, the acoustic energy is mainly distributed on the substrate surface, and the wave vibration direction is perpendicular to the wave propagation direction. In Example 2, the top view and the front view of the acoustic field distribution in the phononic crystal cell are shown as follows: Figure 8 As shown in (b) and (c).

[0043] For the microporous phononic crystal in Example 2, the energy band and transmission spectrum of the Love wave phononic crystal are as follows: Fig. 9 shown.

[0044] Example 3 In this embodiment 3, in one implementation mode, the phononic crystal is formed by etching periodic or non-periodic holes or groove structures on the surface of the lithium tantalate single crystal film. The lattice of the phononic crystal is a tetragonal lattice with C4 symmetry, and the lattice period is 1.5 microns. The etched hole structure forms a microporous phononic crystal 1. The shape of the micropore is circular, that is, a circular hole, and the diameter of the circular hole is 1 micron and the depth is 300 nanometers, forming a Love wave hole type phononic crystal. The cross-sectional view of the Love wave hole type phononic crystal along the section line A-A' is shown as follows: Fig.10 shown.

[0045] In this embodiment 3, the lithium tantalate single crystal film has a thickness of 300 nanometers, and the tangential direction of the lithium tantalate is 42° in the Y direction. The substrate 3 and the substrate 5 form a functional substrate, wherein the substrate 3 is silicon dioxide, and the substrate 5 is single crystal silicon with a (100) crystal orientation.

[0046] Alternatively, in another embodiment, the phononic crystal is formed by growing a periodic or non-periodic column structure on the surface of the lithium tantalate single crystal film. The column structure forms a micro-column phononic crystal 1', the micro-column is a cylinder, the cylinder height is 50 nanometers, the material is aluminum, the lattice period is 1.5 microns, the cylinder diameter is 1 micron, and the Love wave column type phononic crystal is formed. For the Love wave column type phononic crystal, its cross-sectional view along the section line A-A' is as follows Fig.11 shown.

[0047] The microporous phononic crystal in Example 3 has a Love mode bandgap along the Г-X direction of the Brillouin zone of the phononic crystal, and the bandgap range is 0.946-1.492 GHz. Fig.12 As shown in (a). Love waves are horizontal shear waves, the acoustic energy is mainly distributed on the substrate surface, and the wave vibration direction is perpendicular to the wave propagation direction. In Example 3, the top view and the front view of the acoustic field distribution in the phononic crystal cell are shown as follows: Fig.12 As shown in (b) and (c).

[0048] For the microporous phononic crystal in Example 3, the energy band and transmission spectrum of the Love wave phononic crystal are as follows: Fig.13 shown.

[0049] In summary, the Love wave phononic crystal based on lithium tantalate single crystal film provided by the present invention has a wider directional band gap of the Love wave, and a significant decrease in transmission efficiency can be found within the band gap range, which is of great significance for realizing a new generation of high-performance and miniaturized microwave acoustic devices.

[0050] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A Love wave phononic crystal based on lithium tantalate single crystal film, characterized in that: The Love wave phononic crystal comprises a functional substrate and a piezoelectric film layer attached to the upper surface of the functional substrate, wherein the functional substrate comprises several layers of substrates having high sound velocity or temperature compensation functions; The piezoelectric film layer is a lithium tantalate single crystal film, and a micropore or microcolumn structure is constructed on the lithium tantalate single crystal film to form a phononic crystal.

2. The Love wave phononic crystal based on lithium tantalate single crystal film according to claim 1, characterized in that: The material of the functional substrate is one or more of silicon carbide, sapphire, quartz, diamond, silicon dioxide, polycrystalline silicon, and single crystal silicon.

3. The Love wave phononic crystal based on lithium tantalate single crystal thin film according to claim 1, characterized in that: The tangent direction of the lithium tantalate single crystal film is one of the Y-cuts, including 0°Y, 36°Y, 42°Y, 50°Y, 64°Y, and 128°Y.

4. The Love wave phononic crystal based on lithium tantalate single crystal film according to claim 1, characterized in that: The microporous structure is formed by etching a periodic or non-periodic hole or groove structure on the surface of the lithium tantalate single crystal film; the microcolumn structure is formed by growing a periodic or non-periodic column structure on the surface of the lithium tantalate single crystal film.

5. The Love wave phononic crystal based on lithium tantalate single crystal film according to claim 4, characterized in that: The cross-sectional shapes of the hole or groove structure and the column structure are one or more combinations of circular, elliptical, triangular, polygonal or other irregular shapes.

6. The Love wave phononic crystal based on lithium tantalate single crystal film according to claim 4, characterized in that: The material of the column structure is lithium tantalate, silicon, silicon dioxide, silicon nitride or metal material, and the metal material includes aluminum, copper, nickel, and chromium; the height of the column structure is 0-1000 microns.

7. The Love wave phononic crystal based on lithium tantalate single crystal film according to claim 4, characterized in that: The depth of the hole or groove structure is less than the thickness of the lithium tantalate single crystal film, equal to the thickness of the lithium tantalate single crystal film, or greater than the thickness of the lithium tantalate single crystal film.

8. The Love wave phononic crystal based on lithium tantalate single crystal film according to claim 4, characterized in that: The lattice of the phononic crystal is a triangular lattice, a tetragonal lattice, a honeycomb lattice, a cage lattice or other lattices with symmetry, and the lattice period ranges from 0 to 1000 microns.

9. The Love wave phononic crystal based on lithium tantalate single crystal thin film according to claim 1, characterized in that: The thickness of the lithium tantalate single crystal film is 0-10 microns.

10. The Love wave phononic crystal based on lithium tantalate single crystal film according to claim 1, characterized in that: The phononic crystal is a multi-layer one-dimensional phononic crystal or a two-dimensional phononic crystal, and the number of layers is 1-1000.

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