Visualization of Surface Acoustic Wave by Transmission Mode Microwave Impedance Microscopy

Surface acoustic wave (SAW) devices based on piezoelectric materials play a critical role in modern information technology and the research field of phononic metamaterials and quantum computing. High-resolution real-space mapping of the phononic modes is therefore of fundamental importance for the understanding of propagation, scattering, diffraction, and localization of the acoustic waves. However, it was challenging to image the GHz-range acoustic properties in piezoelectrics directly. Using a transmission-mode microwave impedance microscope (T-MIM), we demonstrate the ability to visualize SAW in multiple systems, including band-pass filter, resonator, and phononic crystals. Our results show that T-MIM can be used to locally probe acousto-electronic behaviors in various platforms with nanoscale spatial resolution.