M. Matijevic

SESAM: Exploring the frontiers of electron microscopy

We report on the sub-electron-volt-sub-angstrom microscope (SESAM), a high-resolution 200-kV FEG-TEM equipped with a monochromator and an in-column MANDOLINE filter. We report on recent results obtained with this instrument, demonstrating its performance (e.g., 87-meV energy resolution at 10-s exposure time, or a transmissivity of the energy filter of T1 ev = 11,000 nm2). New opportunities to do unique experiments that may advance the frontiers of microscopy in areas such as energy-filtered TEM, spectroscopy, energy-filtered electron diffraction and spectroscopic profiling are also discussed.

Electron optical design of the Phase Aberration Corrected Electron Microscope

Thin biomolecular specimens are weak phase objects. Therefore image contrast is described by the so called Phase Contrast Transfer Function (PCTF) which depends on the phase introduced by the spherical aberration and defocus. The PCTF describes the signal transfer as a function of the spatial frequency. Due to the sine-type transfer function artefacts arise from contrast reversal and cancellation of low spatial frequencies. Substantial improvement of the quality of the images can be achieved by using a Phase Plate (PP) integrated in a CS-corrected microscope. The PP normally placed in the back focal plane of the objective helps to transfer lower frequencies while the CS corrector is essential for the transfer of higher frequencies. This offers the possibility of artefact free imaging over a wide range of spatial frequencies. In this paper we describe the electron optical design of the Phase Aberration Corrected Electron Microscope (PACEM), which is developed in collaboration with the Max- Plank-Institute for Biophysics in Frankfurt. First results will be presented.

Advanced deflector elements for high-throughput electron optical systems

We have successfully produced and outfitted in-lens deflector elements which can be used for off-axis aberration correction in high throughput electron optics. A thorough analysis of mechanical tolerances, the study of the effect of mechanical tolerances on the imaging performance, and the comparison of calculated and measured deflection fields indicate the capability of such deflector elements for reaching the demands of high throughput electron optical devices.