Study of Phononic Surface Acoustic Wave Devices

Phononic crystal (PnC) is a new acous-tic metamaterial. PnC structures perform an-isotropic propagation and acoustic band gaps for various acoustic waves. In this project, PnCs were used to suppress the energy loss and improve the performance of surface acoustic wave (SAW) devices. A tung-sten/lithium niobate PnC for SAW was cho-sen in this project. The band structures and equal frequency contours of SAWs in the PnC were calculated. Then the band gaps and anisotropic propagation were obtained and a phononic lens was designed based on the properties. The result shows that the en-ergy velocity of the 445 MHz Rayleigh wave showed obvious negative refraction in the Γ-M direction of PnC made of 400-nm thickness and 1.6-μm radius tungsten films. Besides, tapered structure reduced the en-ergy loss at the interface and raised the transmission to 90%. In the three-dimensional simulation, the diffraction energy loss was suppressed. Then a phononic lens was fabricated by mi-cro-electro-mechanical systems (MEMS) process to verify the simulation. The study was valuable for applying PnCs in high per-formance SAW devices.

Project ID:PB10408-5763
External Project ID:MOST104-2221-E182-067