ultra-high-resolution polepiece

The "ultra-high-resolution polepiece" makes it possible to obtain a Cs of 0.5 mm, a Cc of 1.0 mm and a spatial resolution for a TEM image of 0.19 nm at an accelerating voltage of 200 kV, in which the tilt angle of a specimen holder is limited to ±(20°to 25°). It is used for high spatial resolution microscopy and for analytical microscopy from nm diameter areas. This polepiece gives rise to a drawback which cannot be overlooked. That is, the correct bright and dark field images cannot be often obtained. The reason is as follows: The objective aperture is normally inserted into the lower part of the polepiece to prevent the objective aperture from contacting the specimen holder when it is tilted. In this case, the diffraction pattern is formed above the aperture plane. As a result, the aperture cannot often select one diffraction spot but takes influence of neighbor spots. Thus, the bright and dark field images are influenced by the effect of other diffraction. It is noted that there is option to insert a special aperture at the polepiece gap to obtain correct bright- and dark-field images.

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