Mapping acoustic field distributions of VHF to SHF SAW transducers using a Scanning Electron Microscope

Mapping the energy distribution of Surface Acoustic Wave (SAW) devices operating in the Very High Frequency (VHF) and Super-High Frequency (SHF) range provides a quantitative indicator of energy confinement, a core parameter when addressing low loss filters or high quality factor resonators. We here demonstrate the use of Scanning Electron Microscopy (SEM) for mapping Rayleigh wave acoustic field and shear transverse wave (STW) propagating on quartz. Furthermore, the availability of Focused Ion Beam (FIB) for milling the piezoelectric substrate allows for creating obstacles on the acoustic path and hence tune the acoustic wave propagation direction by reflecting the waves along directions which might otherwise exhibit poor electromechanical coupling.