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M T Otten

Publications and source records attributed to M T Otten.

2 recordsLinked to original sources

The effect of inelastic scattering on crystal structure refinement from electron diffraction patterns recorded under almost parallel illumination.

Recently a number of crystal structures were determined using electron diffraction data with an almost parallel electron beam. In many cases no energy filtering was applied. On the other hand, the contrast in convergent beam electron diffraction patterns is greatly improved by energy filtering of the electrons. To investigate whether energy filtering will improve the accuracy of the structure analysis from diffraction data recorded under an almost parallel beam condition, we recorded diffraction patterns of the [100] zone of YBa(2)Cu(3)O(7) using unfiltered electrons, zero-loss electrons and plasmon-loss electrons, respectively. Subsequently, the structure is refined based on these different electron diffraction datasets, using the program MSLS (Acta Crystallogr. A 54 (1998) 91). The results show that the obtained atomic positions are not significantly different for the chosen filter conditions. Even with amorphous carbon deposited on the specimen, which will cause a significant increase (>40 times) of energy-loss electrons, the structure refinement led to the same atomic positions.

Journal Article↗

High-angle annular dark-field imaging on a TEM/STEM system.

The technique of high-angle annular dark-field (HAADF) imaging, which is highly sensitive to atomic-number contrast, can be performed on TEM/STEM systems using the standard annular dark-field detector. For optimum HAADF imaging, the TEM/STEM must have a high maximum diffraction angle, small minimum camera length, and a descanning facility. The sensitivity of the technique is demonstrated to be about 10(5) to 10(6) times higher than energy-dispersive X-ray spectroscopy. Examples are shown from semiconductor, catalysis, ceramics, and particle analysis applications.

Catalysis↗