The Growth Of ZnO Piezoelectric Thin Films And The Research Of SAW Devices

SAW?surface acoustic wave?devices are low-cost,miniature and multifunctional and,therefore,have captured a dominant share of the communication market due to their low-cost,miniature and multifunction.Moreover,SAW has been widely investigated in the sensor field and indicated a promising prospect in the market of microfluidics as well.As a piezoelectric material,ZnO has many advantages such as low cost,high electro-mechanical coupling factor and good biocompatibility,etc.ZnO film with different orientations can be accessed using versatile technologies.It is regarded to replace these expensive piezoelectric single-crystal materials such as LiNbO₃ and LiTaO₃,and serve as the main material for the production of SAWD.This study contains following contents:?1?First of all,two ZnO films with different orientations??0002?and?11???0??are respectively fabricated on substrates Si and SiO₂?200nm?/Si using the radio frequency magnetron sputtering.Effects of sputtering pressure,argon-oxygen ratio and deposition temperature on the ZnO growing orientation are discussed.We find that it is likely to fabricate the?0002?ZnO film under the technological condition of high puttering pressure?1Pa?,high argon-oxygen ratio?9:1?and high deposition temperature?400??,while as it is proper to fabricate the?11???0?ZnO film under the condition of low puttering pressure?0.1Pa?,low argon-oxygen ratio?100%O₂?and high deposition temperature?500??.?2?The finite element method is used to analyze the effects of the thicknesses of films on dispersion characteristics of Love wave in the multilayer structure of the ZnO/SiO₂/Si has been calculated with the thickness variety of Zn O and SiO₂,respectively.which includes phase velocity,electro-mechanical coupling factor and temperature coefficient of frequency.Based on the simulation results,the Love wave with the optimized structure of IDT/ZnO?11???0?(h_{Zn O}/?=0.2)/SiO₂(h_SiO2/?=0.1)/Si?100?shows the velocity,the electro-mechanical coupling and the temperature coefficient of frequency factor are 3308m/s,3.37%and-0.1ppm/?,respectively.The simulation results agrees with the experiments.?3?A surface acoustic wave microfluidic device is fabricated,and The mechanism of both Rayleigh wave and shear wave driving liquid drop is simulated and discussed using the finite element method via acoustic pressure and acoustic streaming fields.The simulation shows the Rayleigh wave radiates energy effectively into the liquid drop through the vertical component of the displacement of particle motion on surface,while the shear wave transfers less energy into the liquid drop by means of surface tension which is induced by the horizontal component of the displacement.