Research Of Magnetoelectric SAW Resonator With Piezoelectric/Magnetostrictive Structure

Aiming at the problem that the sensitivity of the magnetic field sensor is not high enough and the volume is too large at this stage,this paper proposed a resonator based on the combination of magnetoelectric composite multilayer structure and surface acoustic wave(SAW),to realize the weak magnetic field detection.The surface acoustic wave resonator of this paper is based on ScAlN / FeGa magnetoelectric composite multilayer structure,which can be applied to the detection of DC or low frequency magnetic field.The main contents of this thesis are as follows:1.The propagation characteristics of ScAlN/FeGa multilayers were calculated by using the same material parameters by the scattering matrix method and COMSOL Multiphysics simulation method,the propagation characteristics include the SAW dispersion curve and the electromechanical coupling coefficient and the cut-off Young's modulus.The results of the scattering matrix method show that when f*hScAlN is less than0.32 GHz.?m the SAW velocity is between 2089m/s and 2249m/s,and the electromechanical coupling coefficient value first increase from 0.2% to 0.8% and then decrease to 0.02%.For the resonator to work properly,it is necessary to limit the value of f*hScAlN to less than 0.29 GHZ.?m.In this paper,the results of COMSOL simulation software are used to verify the results of scattering matrix method.The results show that the SAW velocity and the electromechanical coupling coefficient are consistent with each other.2.A piezoelectric film with high c-axis orientation was prepared by RF magnetron sputtering.The effects of each sputtering condition on the orientation and surface morphology of AlN films were investigated,and the optimum conditions for the preparation films were obtained,the FWHM is 5oand RMS is 2.8nm.Base on this high orientation ScAlN films with different Sc content was prepared.The ScAlN film with Sc content of 14.5% had a half width of 3.6o and RMS of 2.36 nm.The effects of each sputtering condition on the properties of ScAl N thin films were investigated.The effects of different doping amounts on the growth rate and crystal structure of ScAlN films were investigated.In view of the significant difference in the demand for N2 partial pressure during the preparation of two kinds of piezoelectric films this paper presents the explanation of the difference in the process of film growth and use the first-principleto calculate.3.Polishing and testing the FeGa substrate,using life-off method to fabricate a resonator.Get the polishing requirements of the polishing process.Using mechanical resonance method to test the ?E effect of FeGa substrate.Frabricate a one port SAW resonator and test the S11 parameter,the resonance frequency is seen at 218 MHz and the SAW velocity is 3488 m/s.