Thermal Wave Imaging with Thermoacoustic Detection

Thermoacoustic imaging is a new technique that permits the detection and imaging of microscopic surface and subsurface fea- tures in a sample. We present a detailed theoretical treatment of the thermoacoustic process with particular emphasis on the roles of ther- mal and elastic parameters in both one and three dimensions. Exam- ples are presented of thermoacoustic images obtained with a scanning electron microscope. These include images of subsurface mechanical defects, metallic grains and grain boundaries, and of dislocation net- works and dopant regions in semiconductor crystals.