The high resolution standard
Meanwhile the correction of spherical aberration has become a standard in high resolution electron microscopy. Several hundred microscope installations world-wide contain a Cs-corrector, more than 90% of which are CEOS correctors. These microscopes have STEM probe correctors or TEM image correctors or even a combination of both.
Cs-corrected transmission microscopy shows a point resolution of the same size as the information limit of the microscope. Therefore, no artifacts or delocalization effects are observed in phase contrast imaging of non periodic regions of the specimen. This enables also a quantitative interpretation of electron micrographs as has been shown in numerous publications. Some examples can be found in our literature list.
Pioneering work and early improvements
The Forschungszentrum in Jülich and the Ernst Ruska Center became pioneers in the application of spherical aberration correction using the development prototype of CEOS's corrector. One of the early exciting results with the prototype corrector was the direct visualization of oxygen atoms published by the Jülich group. Using modern corrected microscopes these institutions continue to push aberration corrected microscopy to new limits.
The next step in corrector development was the correction of fifth-order spherical aberration (C5). We have published a paper about this at the EMC 2004 at Antwerp. Read the excerpt of the results!
Cs-Correctors are now available for most of the high-end TEM's and STEM's. The major suppliers of these instruments have all reported sub-Ångstrøm resolution in their instruments. For details, please consult the following links (listing in alphabetic order):
- FEI reports sub-Ångstrøm-resolution in a Cs-corrected TEM equipped with CEOS's corrector.
- FEI reports 1.4 Ångstrøm resolution at only 80 kV acceleration voltage with CEOS's corrector.
- HITACHI offers an atomic resolution of 80 pm in dark-field STEM mode using CEOS's corrector. The high probe current allows for rapid acquisition of elemental distribution images, even for elements at low concentration.
- JEOL guarantees sub-Ångstrøm STEM resolution for their ARM200F microscope . Their double corrected microscope at Oxford University had reached sub-Ångstrøm-resolution in TEM and STEM mode.
- ZEISS published sub-Ångstrøm resolution results at 200 kV using CEOS's monochromator and Cs-Corrector.
Today it is not unusual that electron microscopes are equipped with CCD cameras resolving 4kx4k pixels or more. The high-resolution field of view of such a microscope is no longer limited by the CCD's modulation transfer function but by off-axial aberrations. The dominating aberration is the off-axial coma.
To overcome this limitation CEOS offers a new type of hexapole corrector system called B-COR. Additionally this novel design is free of axial aberrations up to fifth order including the sixfold astigmatism. The characteristics of the new corrector are described in detail in this poster.
Please contact the microscope manufacturers for a quotation, q.v. links.