Physics Institute

Experimental electron holography is performed in a dedicated laboratory building designed for minimal vibration and ac- magnetic field disturbances. High interference resolution is a major issue of the experimental efforts of the group. This is presently addressed by a novel system design featuring a high resolution and high dynamic detector for low energy electrons.

For imaging individual molecules, free standing sample support is essential for hologram recording. Such sub-micron structures are machined in a scanning electron microscope combined with a focussed ion beam.

The numerical reconstruction of electron holograms is a second key effort of our group. It shall eventually lead to a 3-dimensional real space high resolution structure of a single bio-molecule. While holography, invented by Dennis Gabor, is an ingenious method to solve the phase problem and hologram reconstruction is, at least in principle, a straight forward coherent optics problem, to actually derive at high resolution real space information from a low energy electron hologram is associated with a number of major challenges. One of them is the so-called twin image problem which has obscured real space information ever since holography has been invented. Recently, see publication-section, this problem has finally been solved and opens up the way to twin image free phase- and amplitude-reconstructions from electron holograms of individual molecules.

For further reading on holography and related single molecule experiments see:

Bio-physics group University of Zurich