Electron holography: state and prospects

The phase loss encountered in conventional (S)TEM means a substantial loss of object information, because essential structure components, e.g. electric and magnetic fields, mainly modulate the image phase hence are virtually invisible in a conventional micrograph. This presents a huge obstacle for a thorough understanding of modern functional materials e.g. in semiconductors and nano-magnetism. Phases can only be determined by interference of the image wave with a reference wave. Gabor’s bright idea of holography was to use the interference pattern (hologram) as a diffraction grating, where one of the diffracted waves turns out a replica of the image wave. This replica wave is reconstructed from the hologram allowing subsequent quantitative evaluation of both amplitude and phase separately.