Non Epitaxial Growth Of ZnO Thin Films And Study On Related Surface Acoustic Wave Sensors

Surface acoustic wave(SAW)sensor has been successfully applied in the fields of bioengineering,environmental monitoring,food industry and so on,due to the characteristics of high sensitivity,good versatility,high working frequency and easy integration.In this paper,the propagation characteristics of SAWs are simulated firstly by a 3D Finite Element Method(FEM)multi-physics simulation model in COMSOL,which provide the theoretical basis for the fabrication and application of related sensors.Then the(11^-20)ZnO films are non-epitaxial grown on the silica glass substrate by RF magnetron sputtering,and the related SAW devices are fabricated based on the layered structure.The main contents of this paper are as follows:1)The properties of the delay lines based on the multi-layered structure of ZnO films/Silica Glass and ZnO films/36?YX-LiTaO3 are studied by the 3D FEM models in COMSOL,such as the phase velocity,electro-mechanical coupling coefficient,admittance,insertion loss,mass sensitivity and temperature coefficient of frequency(TCF).Then,the influences of the crystal texture of ZnO piezoelectric thin films,as well as the propagation direction of the acoustic wave,on the characteristics of SAW excited in the structures of ZnO films/non-piezoelectric substrate and the ZnO films/piezoelectric substrate are studied.2)The characteristics of SAW sensors based on the structure of(11^-20)ZnO films/Silica Glass substrate are simulated by the 3D FEM models in COMSOL,in which the sensors are operated in liquid environment.The effects of the mechanical and electrical factors of the adsorbed water layer on the properties of as-modeled SAW sensors are studied numerically,such as the resonant frequency,insertion loss and the sensitivity.3)The(11^-20)ZnO films are non-epitaxial deposited on the silica glass substrate by RF magnetron sputtering.The crystal structure and surface morphology of the ZnO thin films are characterized by X-ray Diffraction(XRD)and Scanning Electron Microscopy(SEM),by which the sputtering conditions are optimized.In addition,the related SAW devices are fabricated with the optimized factors,such as the thickness of(11^-20)ZnO films.