The Evolution of Off-axis Electron Holography towards a Versatile TEM-Method

According to the original proposal by Dennis Gabor, electron holography was invented to overcome the electron-optical aberrations in the transmission electron microscope (TEM) by a-posteriori light optical correction. In order to fulfill Gabor’s dream, it took many decades and important developments like e.g. coherent electron sources, stable microscopes and rooms, fast CCD-cameras as well as dedicated computer software for reconstruction and correction. Nowadays with hardware aberration correctors, however, atomic resolution electron holography with a-posteriori correction of aberrations plays a less significant role. Meanwhile, the phase of the electron wave as carrier of information of electric potentials and/or magnetic fields in or around samples comes into focus for real-world applications pushing the development off-axis electron holography towards a method for measurements of these quantities on the nanometer scale. An interesting alternative electron-optical setup is dark-field off-axis electron holography for measurements of strain fields in solids. More recently, gating the interference fringe contrast by deliberately introducing of noise has open new developments towards time-resolved electron holography with a time-resolution in the nanosecond range. The talk will cover this evolution of electron holography up to the latest developments.