Pt/Ti Electrodes of PZT Thin Films Patterning by Novel Lift-Off Using ZnO as a Sacrificial Layer

We achieve a successful novel lift-off of patterning Pt/Ti electrodes on SiO2/Si substrates by employing ZnO sacrificial layer deposition and patterning, successive uniform Pt/Ti deposition and final lift-off. Then we deposit PZT thin films on the electrodes. Compared with the conventional lift-off processes for the electrodes, this novel process does not need post-annealing, which must be performed after conventional lift-off process. It is demonstrated that the electrodes patterned by the novel lift-off process have stronger adhesion. The electrodes and the PZT films on the electrodes are more compact and smoother than those by the conventional lift-off process.     

UNIFORM GROOVE-DEPTH RAC BY USING TRANSDUCER WEIGHTING

A new weighting method,transducer weighting.for the uniform groove-deph RAC is proposed in thispaper.The weighted input and output transducersform a weighting transversal filter In addition,the groove-width weighting,which can be used as an auxiliary is also discussed. By using the new methods,two uniform groove depth RACs have been designed and fabricated,Thesidelobe suppressions achieved are 31 dB and 32 dB.respectively.The results are considered satisfactorybecause the phase compensation by metal strip was not applied.     

SCATTERING OF NORMALLY INCIDENT RAYLEIGH WAVE FROM SHORT-CIRCUITED METALLIC GRATING

Starting from piezoelectric crystal dynamic equation etc.,both the electric potential and surface chargeinduced by the incident wave are obtained with electrical boundary perturbation technique.The scatteredwaves are then derived including both surface and bulk waves through integral transformation with theinduced charge as exciting source.The scattered surface waves from the grating on YZ-LiNbO_3 are then numerically calculated,and boththe reflective and forward scattering coefficients are given vs.the strip width.Furthermore,the surface wavephase velocity change when passing the grating is derived and numerically calculated too.The theoreticalprediction agrees well with measured results.     

声束在固体中的聚焦及其在声成像中的应用

本文主要研究表面换能器阵列在固体中产生的聚焦及轴上焦场的情形,讨论各级次焦点处场的值与条宽阵元的关系.用数值计算求出某一频率时不同的阵元宽度的焦场分布,并从实用角度出发,讨论将这种聚焦用于无损检测和成像时,横向和纵向分辨率等问题,为了进一步说明理论,做了一些探索性的实验.     

Focusing of Surface Acoustic Wave on a Piezoelectric Crystal

We investigate the focusing phenomena of a surface acoustic wave （SAW） field generated by a circular-arc interdigital transducer （IDT） on a piezoelectric crystal. A rigorous vector field theory of surface excitation on the crystal we developed previously is used to evaluate the convergent SAW field instead of the prevalent scalar angular spectrum used in optics. The theoretical results show that the anisotropy of a medium has great impact on the focusing properties of the acoustic beams, such as focal length and symmetrical distributions near the focus. A dark field method is used in experiment to observe the focusing of the SAW tield optically. Although the convergent phenomena of SAW field on the anisotropic media or piezoelectric crystals are very complicated, the experimental data are in agreement with those from the rigorous theory.     

圆形振动膜ZnO压电微传声器的研制

本文介绍了一种新型圆形振动膜ZnO压电微传声器的制备，并对传声器制备的工艺过程进行了较为详细的描述。圆形振动膜的压电传卢器与以前方形振动膜结构设计相比，较大幅度提高了传声器的灵敏度和成品率，灵敏度达到-70dB（相对于1V／Pa），成品率达到80％。     

声表面波梯形谐振滤波器级联结构的研究

本对声表面波梯形谐振滤波器4级级联的5种不同级联结构进行了理论分析，计算出了其频响特性曲线。对5种不同结构的特性进行了比较，得出了不同结构在带宽、矩形系数、带外抑制等方面的特性，以期对以后实际器件的设计提供理论根据。     

SAW器件在扩展频谱通信中的应用

扩展频谱(以下简称“扩频”)通信在现代通信中是一种很重要的技术,具有抗干扰性强和保密性好的能力;在测距中可以改善测距精度,因为测距精度与扩展带宽有关;利用具有相同谱的码分多址,多个用户可以共用一个信道。 SAW器件在通信系统中有很多应用。本文主要是介绍SAW-MSK信号调制器/产生器和SAW卷积器在扩频通信系统中的应用并报道某些实验结果。     

THE EFFECT OF ELECTRIC LOAD ON THE CHARACTERISTICS FOR PIEZOELECTRIC VIBRATIONAL SYSTEM

The effect of electric load on the piezoelectric vibrational system due to electroacoustic coupling isanalytically investigated.The analytical results show that:(1)when load impedance continuallychanges from ∞to+∞,the mechanical resonant frequency of the system would fill all frequencydomain from 0 to ∞;(2)the displacement and stress distributions also would change,even the dis-placement may be zero at both free ends(i.e.at points where stress is equal to zero). Finally,the experiments for longitudinal vibration of piezoelectric strip of lateral polarizationare given and compared with theoretical results.     

ANALYSIS OF SURFACE EXCITATION OF ELASTIC WAVE FIELD IN A HALF SPACE OF PIEZOELECTRIC CRYSTAL——GENERAL FORMULAE OF SURFACE EXCITATION OF ELASTIC WAVE FIELD

This paper developes the general theory of the surface excitation of elastic wave field in a halfspace of piezoelectric crystal for both free and metallized surfaces.It is shown that the general elas-tic wave field U is equal to the convolution of the generalized Green's functions G and the general-ized forces T, U = G Twhere symbol,expresses dot-product-convolution. The generalized Green's functions are independent of excitation conditions and only dependenton material parameters and orientation. For the piezoelectric crystal,not only a mechanical source distribution at the surface,but anelectrical source distribution can also excite the elastic wave fields.Complete expressions of thegeneralized forces representing mechanical and electrical source distribution respectively are given.Especially for the free surface,the surface electrical sources can be composed of the discontinuityof normal electric displacement at the surface,and of the discontinuity of the tangential electric fieldas well.