The FPW Resonator Device Using PZT Sol-Gel Thin Film for Liquid Sensing

[[abstract]]本論文探討鋯鈦酸鉛（PZT）壓電薄膜於撓性板波（FPW）共振元件之液體感測應用。撓性板波傳遞速度對外界干擾的物理量如應力、質量等，具有相當的敏感度。且當聲波在與液體接觸時，其波傳能量不易散射出去。而撓性板波其背部薄膜孔穴可作為待測溶液的負載區，可精確檢驗出傳遞基材受外界激發所產生的薄板負載質量與應力的變化，故適於液體感測之應用。本研究主要以溶膠-凝膠法製備鋯鈦酸鉛壓電薄膜，來進行撓性板波共振元件製作。元件的材料系統為Pt /Ti /PZT/LSMO /SiNx。在理論分析方面以耦合理論模式來模擬PZT雙埠表面聲波共振器的頻率響應，結合撓性板波的波傳特性來製造撓性板波共振元件。並實際將該元件應用於液體密度感測，結果顯示元件的插入損失和共振頻率會隨著液體負載密度的大小呈線性變化。而該元件的設計比一般撓性板波元件有更低的插入損失值，驗證了本元件於液體感測應用的可行性。[[abstract]]ABSTRACT This thesis focuses on the development of the Flexure plate wave (FPW) resonator using piezoelectric lead zirconate titanates (PZT) films for liquid sensing. The propagation velocities of the FPW are very sensitive to the stress and the loading mass on the substrate. There is less scattering of the energy from the FPW to the loading liquid due to its low phase velocity. The back cavity of the FPW device can serve as the loading area of the sensing liquid to detect the density of liquid and the stress of the membrane. This research adopts PZT piezoelectric films using Sol-Gel technique to fabricate the FPW resonator. The material system is Pt/Ti /PZT/LSMO /SiNx. This study has presented the simulation model using the COM theory for a two-port SAW resonator over a PZT substrate, which is extended to the design of the FPW resonator. The preliminary measurement results show that the resonant frequency and the liquid density have a good linear correlation, and demonstrate the feasibility of the sensor application using the FPW resonator