Focusing of Ultrasound for Photo-Acoustic Subsurface Imaging in AFM Cantilever tip

Over the past few years, sub-surface imaging techniques at the nano-scale have become increasingly important in the semiconductor industry, whereby voids, cracks and other heterogenous features can be detected using disturbances in penetrating waves inside the substrate. A certain modality called photo-acoustic subsurface Atomic Force Microscopy (passAFM) is currently in development at the DMN group in TU Delft. PassAFM uses two fs pulsed lasers to generate and detect acoustic waves inside an AFM cantilever. This technique promises a lateral resolution of subsurface imaging in the order of the AFM tip size. It is required to focus the acoustic waves inside the tip and obtain sufficient acoustic power to detect a signal back from the tip. Therefore, acoustic lensing devices are designed and the improvement in detected signal is studied in this research.Mechanical Engineering | High-Tech Engineerin