ISSN:
1432-2021
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Chemie und Pharmazie
,
Geologie und Paläontologie
,
Physik
Notizen:
Abstract High-resolution transmission electron microscopy (HRTEM) is a powerful technique for crystal structure imaging and real structure analysis. It is theoretically possible to resolve inter-atomic distances with modern high resolution microscopes. In practice, however, the effects of sample and lens parameters such as crystal tilt and phase contrast transfer function (CTF) distort the images, reduce the resolution offered, and make image interpretation difficult. We have analyzed to what extent it is possible to reconstruct interpretable images of a tilted mineral by image processing. HRTEM images of orthopyroxene were simulated for a series of crystal tilts and thicknesses under Scherzer defocus condition using the parameters of a 400 kV microscope. The tilted images were reconstructed by crystallographic image processing. After correcting for crystal tilt, the images were as good as electron density maps calculated from X-ray diffraction structure factors. The effects of crystal tilt could easily be removed by image processing, if specimen thickness and the tilt angle are less than 10 nm and 2.5°, respectively. For larger crystal thicknesses (〉20 nm) the effect of tilting could be removed only for small tilt angles (〈1°). For a given crystal thickness, a slight tilt often resulted in an improved reconstructed image.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00209378
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