阅读说明：本技术 一种基于压电复合薄膜的双频集成超声换能器 (Dual-frequency integrated ultrasonic transducer based on piezoelectric composite film ) 是由 任丹阳 施钧辉 尹永刚 陈睿黾 李驰野 于 2021-07-16 设计创作，主要内容包括：本发明公开了一种基于压电复合薄膜的双频集成超声换能器。本发明基本结构为一种0-0-3型压电复合薄膜(高频压电复合薄膜)、AlN压电薄膜(超高频压电薄膜)以及三层电极的多层结构,结构自上而下包括金属上电极层、0-0-3型复合压电薄膜、中间金属电极层、AlN压电薄膜层、下电极层等。本发明中0-0-3型压电复合薄膜层超声换能器频率范围为数十～数百MHz,而AlN层超声换能器频率范围为GHz,因而通过本发明双频集成式超声换能器的设计,可通过切换不同的换能器层满足不同场景的频率及分辨率使用要求,进而达到提高超声换能器的频率使用范围以及一换能器多用的目的。(The invention discloses a dual-frequency integrated ultrasonic transducer based on a piezoelectric composite film. The basic structure of the invention is a multilayer structure of a 0-0-3 type piezoelectric composite film (high-frequency piezoelectric composite film), an AlN piezoelectric film (ultrahigh-frequency piezoelectric film) and three layers of electrodes, and the structure comprises a metal upper electrode layer, a 0-0-3 type composite piezoelectric film, a middle metal electrode layer, an AlN piezoelectric film layer, a lower electrode layer and the like from top to bottom. The frequency range of the 0-0-3 type piezoelectric composite thin film layer ultrasonic transducer is dozens of MHz to hundreds of MHz, and the frequency range of the AlN layer ultrasonic transducer is GHz, so that the frequency and resolution using requirements of different scenes can be met by switching different transducer layers through the design of the double-frequency integrated ultrasonic transducer, and further the purposes of improving the frequency using range of the ultrasonic transducer and having multiple purposes of one transducer are achieved.)

1. A dual-frequency integrated ultrasonic transducer based on a piezoelectric composite film is characterized by comprising a 0-0-3 type piezoelectric composite film layer, an ultrahigh frequency piezoelectric film layer and a metal electrode layer. Wherein, two kinds of piezoelectric film layers correspond to two kinds of ultrasonic transducer layers with different center frequencies. There is one metal electrode layer common to both piezoelectric thin film layers.

2. The piezoelectric composite film based dual-frequency integrated ultrasonic transducer as claimed in claim 1, wherein the ultrahigh frequency piezoelectric film layer is an AlN piezoelectric film layer or a ZnO piezoelectric film layer.

3. The piezoelectric composite film based dual-frequency integrated ultrasonic transducer as claimed in claim 1, wherein the ultrahigh frequency piezoelectric film layer is prepared by magnetron sputtering. The forming method of the 0-0-3 type piezoelectric composite film layer is a tape casting method or a spin coating method.

4. The dual-frequency integrated ultrasonic transducer based on the piezoelectric composite film as claimed in claim 1, wherein the metal electrode layer can be a single layer metal or a plurality of layers of metals, and each layer of metal is independently selected from gold, platinum, copper, titanium, and the like.

5. The dual-frequency integrated ultrasonic transducer based on the piezoelectric composite film as claimed in claim 1, wherein the transducer is a multilayer structure, and comprises an upper metal electrode layer, a 0-0-3 type piezoelectric composite film layer, a middle metal electrode layer, an ultrahigh frequency piezoelectric film layer and a lower metal electrode layer from top to bottom. The 0-0-3 type piezoelectric composite film layer and the ultrahigh frequency piezoelectric film layer share the middle metal electrode layer.

6. The piezoelectric composite film based dual-frequency integrated ultrasonic transducer according to claim 1, wherein the 0-0-3 type piezoelectric composite film layer comprises piezoelectric polymer, non-polymer piezoelectric material, MXene two-dimensional material; wherein the non-polymer piezoelectric material is piezoelectric ceramic or piezoelectric single crystal. Specifically, a non-polymer piezoelectric material is added to a piezoelectric polymer in a 0-dimensional mode, and an MXene two-dimensional material is added in a 0-dimensional mode to serve as a third phase, so that the MXene/piezoelectric polymer/non-polymer piezoelectric material composite piezoelectric material is formed to serve as a 0-0-3 type piezoelectric composite film layer.

7. The piezoelectric composite film based dual-frequency integrated ultrasonic transducer according to claim 6, wherein the piezoelectric polymer is PVDF or PVDF-based polymer.

8. The piezoelectric composite film based dual-frequency integrated ultrasonic transducer according to claim 7, wherein the PVDF-based polymer is P (VDF-TrFE), PVDF-HFP, P (VDF-CTFE), or P (VDF-TrFE-CTFE).

9. The piezoelectric composite film based dual-frequency integrated ultrasonic transducer according to claim 6, wherein the piezoelectric single crystal is PMN-PT, PMN, PZN-PT, LiNbO3, LiTaO₃And the like. The piezoelectric ceramics are PZN and the like.

10. The piezoelectric composite film based dual-frequency integrated ultrasonic transducer according to claim 6, wherein the MXene two-dimensional material is Ti₃C₂、Ti₂C、Ta₃CN or Ti₃CN, and the like.

Technical Field

The invention belongs to the technical field of micro electro mechanical systems, and particularly relates to a dual-frequency integrated ultrasonic transducer based on a piezoelectric composite film.

Background

The polymer/piezoelectric ceramic composite material is a composite functional material containing both polymer and piezoelectric ceramic. The composite material has the characteristics of low acoustic impedance and high reception coefficient of the polymer and has the piezoelectric ceramic high-voltage electric strain constant d₃₃And high electromechanical coupling coefficient. However, the current research on the composite piezoelectric material shows that the performance of the composite piezoelectric material prepared by simply mixing the polymer and the piezoelectric ceramic material is not good. The reason is that most of PVDF-based polymers in the composite piezoelectric material are alpha phases without piezoelectric performance, and the beta phase with the piezoelectric performance accounts for a little bit, so that the piezoelectric performance of the composite material is limited to a certain extent. In addition, the composite piezoelectric material prepared by simply mixing the polymer and the piezoelectric ceramic is very easy to have insufficient polarization due to the difference of the polarization voltages of the polymer and the ceramic.

Disclosure of Invention

The invention aims to provide a dual-frequency integrated ultrasonic transducer based on a piezoelectric composite film, aiming at the defects of the prior art. The invention prepares a dual-frequency ultrasonic transducer based on a 0-0-3 type piezoelectric composite film and an AlN film, and by the design of the dual-frequency integrated ultrasonic transducer, the frequency and resolution ratio using requirements of different scenes can be met by switching different transducer layers, so that the frequency using range of the ultrasonic transducer from tens of MHZ to GHz is further improved, the aim of one transducer to be multipurpose is achieved, and the dual-frequency ultrasonic transducer can be applied to medical transdermal drug delivery, detection of tissues in a body and the like.

The purpose of the invention is realized by the following technical scheme: a dual-frequency integrated ultrasonic transducer based on a piezoelectric composite film comprises a 0-0-3 type piezoelectric composite film layer, an ultrahigh frequency piezoelectric film layer and a metal electrode layer. Wherein, two kinds of piezoelectric film layers correspond to two kinds of ultrasonic transducer layers with different center frequencies. There is one metal electrode layer common to both piezoelectric thin film layers.

Further, the ultrahigh frequency piezoelectric thin film layer is an AlN piezoelectric thin film layer or a ZnO piezoelectric thin film layer.

Further, the ultrahigh frequency piezoelectric film layer is prepared by a magnetron sputtering method. The forming method of the 0-0-3 type piezoelectric composite film layer is a tape casting method or a spin coating method.

Further, the metal electrode layer may be a single layer metal or a plurality of layers of metals, each layer of metal being independently selected from gold, platinum, copper, titanium, and the like.

Furthermore, the composite electrode is of a multilayer structure and comprises an upper metal electrode layer, a 0-0-3 type piezoelectric composite film layer, a middle metal electrode layer, an ultrahigh frequency piezoelectric film layer and a lower metal electrode layer from top to bottom. The 0-0-3 type piezoelectric composite film layer and the ultrahigh frequency piezoelectric film layer share the middle metal electrode layer.

Further, the 0-0-3 type piezoelectric composite film layer comprises a piezoelectric polymer, a non-polymer piezoelectric material and an MXene two-dimensional material; wherein the non-polymer piezoelectric material is piezoelectric ceramic or piezoelectric single crystal. Specifically, a non-polymer piezoelectric material is added to a piezoelectric polymer in a 0-dimensional mode, and an MXene two-dimensional material is added in a 0-dimensional mode to serve as a third phase, so that the MXene/piezoelectric polymer/non-polymer piezoelectric material composite piezoelectric material is formed to serve as a 0-0-3 type piezoelectric composite film layer.

Further, the piezoelectric polymer is PVDF or PVDF-based polymer.

Further, the PVDF-based polymer is P (VDF-TrFE), PVDF-HFP, P (VDF-CTFE), or P (VDF-TrFE-CTFE).

Further, the piezoelectric single crystal is PMN-PT, PMN, PZN-PT, LiNbO3, LiTaO₃And the like. The piezoelectric ceramics are PZN and the like.

Further, the MXene two-dimensional material is Ti₃C₂、Ti₂C、Ta₃CN or Ti₃CN, and the like.

The invention has the beneficial effects that:

(1) the piezoelectric composite film material prepared based on the PVDF-based polymer is prepared by the method, on the basis of the PVDF-based polymer/PMN-PT piezoelectric composite material, by adding the graphene-like two-dimensional material MXene with rich functional groups (-OH, -O, -H, -F and the like) as a third phase, the 0-0-3 type flexible composite piezoelectric film is formed, the arrangement orientation of molecular chains of the PVDF-based polymer is effectively improved, the piezoelectric performance of the PVDF-based polymer is obviously improved, thereby ensuring the performance of the composite material, not only ensuring lower acoustic impedance and ensuring that the composite material has acoustic impedance matched with a human body in the application of the ultrasonic transducer, but also having better piezoelectric performance (such as piezoelectric strain constant, piezoelectric voltage constant, electromechanical coupling coefficient, quality factor and the like), thereby being used for preparing a high-frequency ultrasonic transducer layer with the working frequency of tens to hundreds of MHz;

(2) the piezoelectric film material in the other ultrahigh frequency ultrasonic transducer layer is an AlN layer, and the working frequency can reach GHz. And the ultrasonic transducer is integrated with the 0-0-3 type high-frequency ultrasonic transducer into a dual-frequency ultrasonic transducer. The dual-frequency integrated ultrasonic transducer is an ultrasonic transducer with two working frequency bands, has a wider frequency application range and has a wider application prospect compared with the traditional single-frequency ultrasonic transducer. The method can be applied to semiconductor defect detection, medical transdermal drug delivery, detection of internal tissues of bodies and the like.

Drawings

FIG. 1 is a schematic structural diagram of an embodiment of the present invention;

fig. 2 is a schematic flow chart of a manufacturing process of a dual-frequency integrated ultrasonic transducer according to an embodiment of the present invention.

Detailed Description

The invention relates to a double-frequency integrated ultrasonic transducer based on a piezoelectric composite film, which has a basic structure of a multilayer structure consisting of a 0-0-3 type piezoelectric composite film, an ultrahigh frequency piezoelectric film and three layers of electrodes; the two piezoelectric film layers of the 0-0-3 type piezoelectric composite film and the ultrahigh frequency piezoelectric film correspond to two ultrasonic transducer layers with different central frequencies, and therefore the dual-frequency integrated ultrasonic transducer is achieved. Specifically, as shown in fig. 1, the structure of the present invention includes, from top to bottom, a metal upper electrode layer, a 0-0-3 type composite piezoelectric film (high frequency ultrasonic transducer layer), a middle metal electrode layer, an ultrahigh frequency piezoelectric film layer, and a lower electrode layer. In the invention, the two ultrasonic transducer layers share the middle metal electrode layer.

The metal electrode layer in the invention can be a single-layer metal or a plurality of layers of metals, and each layer of metal is independently selected from gold, platinum, copper, titanium and the like.

The 0-0-3 type piezoelectric composite material consists of a piezoelectric polymer, a non-polymer piezoelectric material and an MXene two-dimensional material; the non-polymer piezoelectric material is piezoelectric ceramic or piezoelectric single crystal. The piezoelectric polymer in the 0-0-3 type piezoelectric composite material can be PVDF or PVDF-based copolymer; among them, the PVDF-based copolymer includes P (VDF-TrFE), PVDF-HFP, P (VDF-CTFE), P (VDF-TrFE-CTFE), and the like. The piezoelectric single crystal in the 0-0-3 type piezoelectric composite material can be Pb (Mg)_1/3Nb_2/3)O₃-PbTiO₃(PMN-PT)、PMN、PZN-PT、LiNbO₃Lithium niobate, LiTaO₃Etc.; the piezoelectric ceramic may be PZT or the like. The MXene two-dimensional material selected by the invention can be Ti₃C₂、Ti₂C、Ta₃CN、Ti₃CN, and the like. The forming method of the 0-0-3 type piezoelectric composite film material is a tape casting method or a spin coating method.

The ultrahigh frequency piezoelectric film layer selected by the invention can be AlN, ZnO and other piezoelectric film layers. The ultrahigh frequency piezoelectric film layer is prepared by a magnetron sputtering method.

The 0-0-3 type piezoelectric film layer in the high-frequency ultrasonic transducer layer of the invention forms the MXene/PVDF-based polymer/PMN-PT composite piezoelectric material by adding the two-dimensional sheet material MXene with a large number of active groups (-OH, -O, -H, -F, etc.) and good conductivity as the third phase material, functional groups on the MXene surface can be combined with polar F atoms in PVDF in a mode of forming hydrogen bonds, thereby not only improving the orientation arrangement of molecular chains of the PVDF-based polymer and preparing the flexible piezoelectric polymer film with higher beta-phase content, leading all components of the composite material to be dispersed uniformly, but also improving the conductivity of the whole substrate, further improving the piezoelectric performance, reducing the required polarization voltage and leading the MXene/PVDF-based polymer/PMN-PT composite piezoelectric material to be more polarized fully, and the piezoelectric property of the composite material is improved while the lower acoustic impedance of the composite material is kept. The composite piezoelectric film slurry with high piezoelectric performance is prepared by adjusting the volume fractions of the MXene phase, the non-polymer piezoelectric material phase and the piezoelectric polymer phase, and is prepared for tape casting. The working frequency range of the integrated ultrasonic transducer of the 0-0-3 type composite piezoelectric layer prepared by the invention can reach dozens to hundreds of MHz.

The ultrahigh frequency ultrasonic transducer layer is an AlN piezoelectric thin film layer integrated ultrasonic transducer prepared by a magnetron sputtering method, and the center frequency of the ultrahigh frequency ultrasonic transducer layer can reach GHz.

The preparation method of the dual-frequency integrated ultrasonic transducer comprises the following steps: sputtering Pt electrode on a silicon substrate to form an electrode layer, sputtering an AlN piezoelectric film on the electrode layer by adopting a magnetron sputtering method, sputtering a Pt metal electrode layer, casting 0-0-3 type slurry into a piezoelectric composite film by adopting a casting method, and finally preparing a third layer of Pt metal electrode by adopting a sputtering method.

In order to make the aforementioned objects, features and advantages of the present application more comprehensible, embodiments accompanying the present application are described in detail below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. This application is capable of embodiments in many different forms than those described herein and those skilled in the art will be able to make similar modifications without departing from the spirit of the application and it is therefore not intended to be limited to the embodiments disclosed below.

As shown in fig. 2, an embodiment of a dual-frequency integrated ultrasonic transducer based on a piezoelectric composite film according to the present invention is prepared by the following steps:

1) immersing a silicon wafer into an acetone solution for ultrasonic cleaning for 10-60 minutes, taking the silicon wafer out of the acetone solution, putting the silicon wafer into deionized water for cleaning, taking the silicon wafer out, immersing the silicon wafer into absolute ethyl alcohol for ultrasonic cleaning for 10-60 minutes, taking the silicon wafer out, cleaning and blow-drying the silicon wafer by the deionized water, and then putting a substrate into HF for soaking to remove a surface oxide layer of the substrate.

2) In order to firmly combine the Pt electrode with the substrate, Ti with proper thickness is sputtered to be used as a buffer layer, and then the sputtering of the Pt electrode is carried out to obtain a lower electrode layer.

3) And then selecting an Al target as a sputtering target material, using working gases of nitrogen, nitrogen-argon mixed gas and nitrogen-argon-hydrogen mixed gas, adjusting the working pressure, sputtering power and other process parameters, and beginning to deposit the AlN piezoelectric film layer.

4) And then sputtering a Pt layer on the AlN thin film layer to be used as a common electrode layer (an intermediate metal electrode layer) of the dual-frequency integrated ultrasonic transducer.

5) Weighing a certain amount of PVDF or PVDF-based polymer powder, adding a proper amount of Dimethylformamide (DMF) solution, uniformly stirring to obtain a uniform PVDF solution, then adding a small amount of MXene powder of a two-dimensional sheet layer, stirring for several hours to obtain a DMF/MXene/PVDF composite solution, adding a proper amount of PMN-PT powder in a ratio into the prepared DMF/MXene/PVDF composite solution, stirring, and ultrasonically dispersing for a certain time until the mixture is uniformly dispersed to obtain MXene/PVDF/PMN-PT composite slurry.

6) Coating the MXene/PVDF/PMN-PT composite solution obtained in the step 5) on the horizontally placed multilayer structure obtained in the step 4) to enable the solution to flow uniformly, then placing the solution into an oven, adjusting the temperature and drying. In this embodiment, the oven temperature may be 30-150 ℃ and the drying time may be 0.5-5h, thereby obtaining a dried cast film.

7) And (3) carrying out hot press molding on the casting film obtained in the step 6) to obtain the 0-0-3 type composite piezoelectric film. In this embodiment, the hot-pressing temperature can be 50-170 deg.C, the pressure can be 0.001-10MPa, and the time can be 0.1-10 h.

8) Sputtering a Pt layer as a third layer electrode (metal upper electrode layer) on the structure obtained in step 7).

9) And leading out a cable and an outer frame from the three layers of electrodes, and finishing the preparation of the dual-frequency integrated ultrasonic transducer.