Erik Essers

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.

The MANDOLINE filter and its performance

The MANDOLINE filter, proposed by Uhlemann and Rose [1], was developed within the SESAM (Sub-Electronvolt Sub-?ngstrom Microscope) project [2]. This highly sophisticated in-column imaging energy filter recently passed its final acceptance tests, surpassing all its specifications considerably.

Advances In Variable Pressure Imaging and Detection

The variable pressure scanning electron microscopy (VPSEM) has gained considerable interest since its commercial introduction more than 30 years ago [1]. Unlike a conventional SEM, which functions only in high vacuum, the VPSEM can be operated under a gas pressure in the specimen chamber. This permits observation of non-conductive samples without coating, as well as outgassing specimens, which are normally not compatible with high vacuum. However, due to the skirt effect [2] of the primary electron beam, resolution of a VPSEM is usually significantly reduced compared to a conventional SEM. Furthermore the VPSEM is also particularly troublesome for EDS applications, because additional X-ray signal is produced by the electron skirt. In this contribution we will introduce the newly developed VP implementation of next-generation Zeiss SEM, which features not only a very restricted skirt effect under high gas pressures, but also enables the detection of pure secondary electron (SE) signal using all Zeiss Gemini technology in-lens detectors.