PhotoAcoustic SubSurface Atomic Force Microscopy: Visualizing chips by touch and sound

3D imaging of subsurface structures at the nanoscale is a longstanding challenge in microscopy. Ultrasound enables subsurface imaging, but nanometer depth resolution requires high-frequency sound waves, achieved by heating with pulsed lasers. Combined with Atomic Force Microscopy (AFM), which offers atomic-scale surface resolution a promising candidate for full 3D nanoscale imaging emerges.

This thesis focuses on the development of such a combined ultrasound-AFM system.
Novel optical detection techniques are introduced for both the ultrasound and the AFM, enabling simultaneous operation.

Acoustic waves up to 100 GHz are generated and detected, used to characterize the thickness and adhesion of thin films. We demonstrate that the conical AFM tip acts as an acoustic lens, focusing the wave into the tip apex. When in contact with a sample, changes in the reflection signal confirm acoustic transmission—opening the door to true 3D nanoscale imaging.