Observation of buried interfaces with low energy electron microscopy

In this Letter we show that a coherent low energy electron beam (<100 eV) can be used to obtain real space images of structures and defects buried deep below the surface of the sample. The elastic strain fields of such buried structures, extending to the free surface, are found to give rise to localized phase shifts in the reflected electron waves, resulting in excellent image contrast under slight objective lens defocus conditions. We can now image the formation and evolution of buried interfaces and defects in situ, and in real time. Because of the very low electron energies used, this imaging method is nondestructive. © 1993 The American Physical Society.