Graphene surface acoustic wave filter device and preparation method thereof
By growing graphene at low temperature on the catalytic metal electrode layer to form covalently bonded graphene interdigitated electrodes, the bonding strength and performance issues of graphene surface acoustic wave filter devices in high-frequency applications are solved, achieving improved filter performance with higher frequency and larger quality factor.
Patent Information
- Application Number
- CN202111417968.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2021-11-25
- Publication Date
- 2025-09-30
- Estimated Expiration
- 2041-11-25
AI Technical Summary
Existing graphene surface acoustic wave filter devices have mass loading effect and interface coupling effect in high-frequency applications. Traditional preparation methods lead to poor bonding between graphene interdigitated electrodes and piezoelectric substrates, and high-temperature growth introduces graphene wrinkles and increases in contaminants.
Graphene is directly grown on the catalytic metal electrode layer using low-temperature plasma-enhanced chemical vapor deposition to form covalently bonded graphene interdigitated electrodes. By preparing the catalytic metal electrode layer on the piezoelectric substrate and growing graphene at low temperature, defects introduced by high temperature are avoided.
It achieves thinner electrode thickness, higher frequency and larger quality factor Q value, improving filter performance while avoiding the problems of graphene wrinkles and increased contaminants caused by high-temperature growth.
Smart Images
Figure CN114094982B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the fields of communication and sensing technology, and in particular to a graphene surface acoustic wave filter device and a preparation method thereof. Background Art
[0002] Surface acoustic wave (SAW) devices, with their advantages of miniaturization, high sensitivity, and high consistency, have found widespread application in radio frequency communications, such as phased-array radar, satellites, mobile devices, and electronic countermeasures, as well as in high-precision sensing applications such as temperature and pressure. The operating frequency of current SAW devices is primarily determined by the width and thickness of their interdigital electrodes, as well as the speed of the surface acoustic wave. Traditional metal interdigital electrodes are typically around 100nm thick. At high frequencies, mass loading and interface coupling effects are significant, making them inadequate for high-frequency applications.
[0003] Graphene has a single atomic layer thickness and high electrical conductivity. It is expected to be used as a cross-finger electrode to realize new high-frequency SAW devices. In addition, graphene itself has low resistance and fast heat dissipation, which has unique advantages in improving the power tolerance and temperature stability of high-Q filters. At present, graphene cross-finger electrodes are mainly prepared by transferring graphene to a piezoelectric substrate and then etching the graphene. The graphene / piezoelectric substrate interface obtained by this method has a weak bonding force, which will seriously affect the performance of the device. In order to promote the cracking of the carbon source by direct growth without catalysis on the piezoelectric substrate, the growth temperature needs to be increased to above 1400 degrees, which is bound to introduce a series of new problems, such as graphene wrinkles, substrate surface roughening, and increased pollutants. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a graphene surface acoustic wave filter device and a preparation method thereof. The present invention can realize direct growth of graphene at low temperature, thereby ensuring the performance of graphene interdigitated electrodes and surface acoustic wave filter devices.
[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions.
[0006] A graphene surface acoustic wave filter device comprises a piezoelectric substrate, a catalytic metal electrode layer and a graphene layer which are sequentially arranged from bottom to top. The graphene layer and the catalytic metal electrode layer together constitute a graphene interdigitated electrode.
[0007] In the above-mentioned graphene surface acoustic wave filter device, preferably, the catalytic metal electrode layer is prepared using a transition metal having the function of catalytically cracking a carbon source as a raw material.
[0008] In the above-mentioned graphene surface acoustic wave filter device, preferably, the transition metal includes one of iron, cobalt, nickel and copper.
[0009] In the above-mentioned graphene surface acoustic wave filter device, preferably, the thickness of the catalytic metal electrode layer is ≤10 nm.
[0010] In the above-mentioned graphene surface acoustic wave filter device, preferably, the constituent material of the piezoelectric substrate is lithium niobate, lithium tantalate or a Group III-V compound piezoelectric material.
[0011] As a general technical concept, the present invention also provides a method for preparing the above-mentioned graphene surface acoustic wave filter device, comprising the following steps:
[0012] S1, cleaning the piezoelectric substrate;
[0013] S2, patterning and preparing a catalytic metal electrode layer on the piezoelectric substrate;
[0014] S3. Growing graphene on the catalytic metal electrode layer to form graphene interdigitated electrodes, thereby obtaining a graphene surface acoustic wave filter device.
[0015] In the above-mentioned method for preparing the graphene surface acoustic wave filter device, preferably, in step S3, the growth of the graphene is carried out by plasma enhanced chemical vapor deposition, wherein the reaction temperature is 550°C to 800°C, and the reaction time is 10s to 100s.
[0016] In the above-mentioned method for preparing a graphene surface acoustic wave filter device, preferably, in step S2, the patterned preparation of the catalytic metal electrode layer comprises the following steps: depositing a catalytic metal thin film on the piezoelectric substrate, then spin-coating a photoresist on the catalytic metal thin film, exposing and developing the photoresist, and then using the photoresist as a mask to perform Ar ion etching to form a preset pattern, and removing the photoresist to obtain the catalytic metal electrode layer;
[0017] In the above-mentioned method for preparing the graphene surface acoustic wave filter device, preferably, in step S2, the patterned preparation of the catalytic metal electrode layer includes the following steps: spin coating photoresist on the piezoelectric substrate, exposing and developing, depositing a catalytic metal film of a preset pattern and soaking it in acetone for peeling off to obtain a catalytic metal electrode layer.
[0018] In the above-mentioned method for preparing the graphene surface acoustic wave filter device, preferably, in step S2, the catalytic metal electrode layer is deposited by electron beam evaporation or magnetron sputtering.
[0019] In the above-mentioned method for preparing the graphene surface acoustic wave filter device, preferably, in step S1, the cleaning process is: first ultrasonically cleaning the piezoelectric substrate with an acetone solution for 5 minutes to 10 minutes, then ultrasonically cleaning it with an isopropyl alcohol solution for 5 minutes to 10 minutes, and then ultrasonically cleaning it with water for 5 minutes to 10 minutes, blowing it dry with nitrogen, and repeating the above steps until the surface of the piezoelectric substrate is free of impurity particles and water stains when observed under a microscope.
[0020] In the present invention, the III-V compound piezoelectric material refers to a type of piezoelectric material composed of elements from Group IIIA and Group VA of the periodic table.
[0021] Compared with the prior art, the advantages of the present invention are:
[0022] 1. Compared with existing surface acoustic wave filters, the graphene surface acoustic wave filter device of the present invention has a thinner electrode thickness and lighter weight, so the filtering frequency can be higher and the quality factor Q value can be larger.
[0023] 2. The present invention uses chemical vapor deposition to directly grow graphene on the catalytic metal electrode layer, and the resulting graphene / metal layer interface force is a covalent bond. Compared with the graphene surface acoustic wave device obtained by the traditional graphene transfer method, the graphene interdigitated electrodes prepared by this method have a stronger bonding force with the piezoelectric substrate, and the catalytic metal electrode layer is very thin and will not weaken the surface acoustic waves generated by the piezoelectric substrate in the graphene interdigitated electrodes. Therefore, it can be beneficial to improve the quality factor Q value, increase the filter frequency, and improve the performance of the graphene surface acoustic wave filter device.
[0024] 3. The present invention adopts a method combining PECVD with catalytic cracking of the metal layer. Compared with the method of direct growth on a piezoelectric substrate without catalysis, it can significantly reduce the graphene growth temperature, avoid the problems of graphene wrinkling, substrate surface roughening, and increased pollutants introduced by high-temperature growth, further improve the quality of graphene, and thus realize high-performance graphene surface acoustic wave filter devices. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Figure 1 Schematic diagram of the top view of the graphene surface acoustic wave filter device in Example 1 of the present invention.
[0026] Figure 2 This is a process flow chart of the method for preparing a graphene surface acoustic wave filter device in Example 1 of the present invention.
[0027] Legend:
[0028] 1. Piezoelectric substrate; 2. Catalytic metal electrode layer; 3. Graphene layer; 4. Surface acoustic wave generator; 5. Surface acoustic wave receiver. DETAILED DESCRIPTION
[0029] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but the scope of protection of the present invention is not limited thereby. The materials and instruments used in the following examples are all commercially available.
[0030] Example 1:
[0031] A graphene surface acoustic wave filter device of the present invention, such as Figure 1 As shown, it includes a piezoelectric substrate 1, a catalytic metal electrode layer 2, and a graphene layer 3 arranged in sequence from bottom to top. The graphene layer 3 covers the catalytic metal electrode layer 2. Both are interdigitated structures. The graphene layer 3 and the catalytic metal electrode layer 2 together constitute a graphene interdigitated electrode. Figure 1 The interdigitated electrodes on the left and right sides are respectively called a surface acoustic wave generator 4 and a surface acoustic wave receiver 5 .
[0032] In this embodiment, the catalytic metal electrode layer 2 is prepared using a transition metal having a catalytic cracking carbon source function as a raw material. The transition metal is specifically nickel. The thickness of the catalytic metal electrode layer 2 is 10 nm.
[0033] In this embodiment, the piezoelectric substrate 1 is made of lithium niobate piezoelectric material, and surface acoustic waves are generated in the graphene interdigitated electrodes through the inverse piezoelectric effect.
[0034] A method for preparing the graphene surface acoustic wave filter device of this embodiment is as follows: Figure 2 As shown, the following steps are included:
[0035] S1. Provide a piezoelectric substrate 1 and clean its surface: In a clean room, ultrasonically clean the piezoelectric substrate 1 in an acetone solution for 5 minutes, then ultrasonically clean it in an isopropyl alcohol solution for 5 minutes, and then ultrasonically clean it in deionized water for 5 minutes. Blow it clean with a high-purity nitrogen gun, and repeat the above cleaning process until there are no obvious foreign particles and water stains on the surface of the piezoelectric substrate observed under a microscope.
[0036] S2. Patterning a catalytic metal electrode layer 2 on the piezoelectric substrate 1: A catalytic metal thin film is deposited on the piezoelectric substrate 1. In this embodiment, electron beam evaporation is used for deposition. A photoresist is spin-coated on the catalytic metal thin film. After exposure and development, the photoresist is used as a mask to etch the catalytic metal thin film with Ar ions to form an interdigitated structure. The photoresist is then removed to obtain the catalytic metal electrode layer 2.
[0037] S3. Growing graphene on the catalytic metal electrode layer 2: placing the piezoelectric substrate covered with the catalytic metal electrode layer 2 in a plasma chemical vapor deposition system, after the temperature is raised to 600°C, introducing precursor gases containing carbon sources such as methane and hydrogen and turning on the plasma, waiting for 20 seconds, turning off the plasma and stopping the introduction of the carbon source, cooling down, completing the direct growth of graphene on the catalytic metal electrode layer 2, and forming a graphene layer 3. The graphene layer 3 and the catalytic metal electrode layer 2 together constitute a graphene interdigitated electrode, thus obtaining a graphene surface acoustic wave filter device.
[0038] In other embodiments, in step S2 , the piezoelectric substrate 1 may be first spin-coated with photoresist, exposed, and developed, and then a catalytic metal film may be deposited and then immersed in acetone for stripping to obtain the catalytic metal electrode layer 2 .
[0039] The above description is only a preferred embodiment of the present invention and does not constitute any formal limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the spirit and technical solution of the present invention, use the methods and technical contents disclosed above to make many possible changes and modifications to the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention, still fall within the scope of protection of the technical solution of the present invention.
Claims
1. A method for preparing a graphene surface acoustic wave filter device, characterized in that: The following steps are involved: S1, cleaning the piezoelectric substrate (1); S2, patterning a catalytic metal electrode layer (2) on the piezoelectric substrate (1); S3, growing graphene on the catalytic metal electrode layer (2) to form graphene interdigitated electrodes, thereby obtaining a graphene surface acoustic wave filter device; In step S3, the growth of the graphene is carried out by plasma enhanced chemical vapor deposition, wherein the reaction temperature is 550°C to 800°C and the reaction time is 10s to 100s; the graphene surface acoustic wave filter device comprises a piezoelectric substrate (1), a catalytic metal electrode layer (2) and a graphene layer (3) arranged in sequence from bottom to top, wherein the graphene layer (3) and the catalytic metal electrode layer (2) together constitute a graphene interdigitated electrode; the catalytic metal electrode layer (2) is prepared using a transition metal having a catalytic cracking carbon source function as a raw material; the transition metal comprises one of iron, cobalt, nickel and copper; the thickness of the catalytic metal electrode layer (2) is ≤10nm; the constituent material of the piezoelectric substrate (1) is lithium niobate, lithium tantalate or a III-V compound piezoelectric material.
2. The method for preparing a graphene surface acoustic wave filter device according to claim 1, wherein: In step S2, the patterned preparation of the catalytic metal electrode layer (2) includes the following steps: depositing a catalytic metal film on the piezoelectric substrate (1), then spin-coating a photoresist on the catalytic metal film, exposing and developing the film, and then using the photoresist as a mask to etch a preset pattern with Ar ions, removing the photoresist, and obtaining the catalytic metal electrode layer (2); Alternatively, in step S2, the patterned preparation of the catalytic metal electrode layer (2) includes the following steps: spin coating photoresist on the piezoelectric substrate (1), exposing, and developing, then depositing a catalytic metal film of a preset pattern and soaking it in acetone for peeling, thereby obtaining the catalytic metal electrode layer (2).
3. The method for preparing a graphene surface acoustic wave filter device according to claim 2, wherein: In step S2, the catalytic metal electrode layer (2) is deposited by electron beam evaporation or magnetron sputtering.
4. The method for preparing a graphene surface acoustic wave filter device according to claim 3, wherein: In step S1, the cleaning process is as follows: the piezoelectric substrate (1) is first ultrasonically cleaned with an acetone solution for 5 minutes to 10 minutes, then ultrasonically cleaned with an isopropyl alcohol solution for 5 minutes to 10 minutes, then ultrasonically cleaned with water for 5 minutes to 10 minutes, and blown dry with nitrogen. The above steps are repeated until the surface of the piezoelectric substrate (1) is free of impurities and water stains when observed under a microscope.