Operation of Aberration Correctors in EMs
- Practical Electron Microscopy and Database -
- An Online Book -


This book (Practical Electron Microscopy and Database) is a reference for TEM and SEM students, operators, engineers, technicians, managers, and researchers.


The human operator is no longer able to manually perform a full series of aberration corrections in EMs because a large number of degrees of aberration freedom originated from the large number of elements and power supplies of the correctors are routinely corrected, and even more there are many possible misalignments. Fortunately, the control of computer and commercial software can help overcome this limitation. This control can automatically analyze, adjust, compensate some optical alignments and most third-order and higher order aberrations. The main day-to-day work on the modern aberration correctors is that the EM users need to correctly judge what corrections they need to do, what buttons they need to push, and what parameters they need to input into the user interface on their PC.

Particularly, in the aberration-correction process, it is necessary to:
        i)  Compensate for the axial second-order aberrations:
                □ The coma
                □ The three-fold astigmatism
        ii) Suppress the non spherical axial third-order aberrations:
                □ The star aberration
                □ The four-fold astigmatism
Those parasitic aberrations must be reduced sufficiently so that the residual phase shift induced by those aberrations is smaller than π/4 in the entire range of the transferred spatial frequencies.




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