应用于气体传感器的具有铝/金电极的单模式两端对声表面波谐振器

为改善气体传感器性能,通过器件优化设计获得了一种应用于气体传感器的具有低损耗、高品质因子(Q)的单模式两端对声表面波(SAW)谐振器。该谐振器由两个换能器、分置于换能器两边的短路栅反射器以及在换能器之间分布的用于敏感膜镀膜的约2.5mm金属薄层构成。谐振器采用铝/金双层电极以降低测试气体环境的腐蚀影响。利用经典耦合模(COM)理论对器件性能进行了仿真以提取优化的结构设计参数。基于仿真结果,实验研制了基于300MHz频率的新型铝/金电极SAW两端对谐振器,测试结果显示所研制器件具有较低损耗(〈7dB),较高Q值(-3000)以及单一谐振模式的特点,并且,以所研制的新型谐振器为频率控制单元的谐振器型振荡器表现出良好的频率稳定度(t15Hz/h),这对于改善气体传感器的检测下限及稳定性等性能指标具有重要意义。 

Development of two-port surface acoustic wave resonator with Al/Au electrode for gas sensing

Simple and efficient surface acoustic wave (SAW) two-port resonators with low insertion loss and high Q-values on ST-X quartz substrate using a corrosion-proof A1/Au-stripe electrode structure are developed for gas sensing. It was composed of two shorted grating reflectors and adjacent intedigital transducers (IDT), and an active metal film in the cavity between the IDTs for the sensitive film coating. The devices are expected to provide good protection towards metal electrode for gas sensors application in chemically reactive environments. Excellent device performance as low insertion loss, high Q-Values and single-mode are achieved by carefully selecting the metallic electrode thickness, cavity length and acoustic aperture. Prior to fabrication, the coupling of modes (COM) model was performed for device simulation to determine the optimal design parameters. The fabricated single-mode SAW resonator at operation frequency of 300 MHz range exhibits matched insertion loss of ~ 6.5 dB and loaded Q values in the 3000 range. Using the fabricated resonator as the feedback element, a dual-resonator-oscillator with excellent frequency stability (0.1 ppm) was developed and evaluated experimentally, and it is significant for performance improvement of SAW gas sensor.