Electron microscope phase enhancement

Details Electron microscope phase enhancement Electron microscope phase enhancement

2005-07-12

2010-06-15

Berman, Jack I (Department: 2881)

Radiant energy

With charged particle beam deflection or focussing

Magnetic lens

C250S309000, C250S311000

Reexamination Certificate

active

07737412

ABSTRACT:
A microfabricated electron phase shift element is used for modifying the phase characteristics of an electron beam passing though its center aperture, while not affecting the more divergent portion of an incident beam to selectively provide a ninety-degree phase shift to the unscattered beam in the back focal plan of the objective lens, in order to realize Zernike-type, in-focus phase contrast in an electron microscope. One application of the element is to increase the contrast of an electron microscope for viewing weakly scattering samples while in focus. Typical weakly scattering samples include biological samples such as macromolecules, or perhaps cells. Preliminary experimental images demonstrate that these devices do apply a ninety degree phase shift as expected. Electrostatic calculations have been used to determine that fringing fields in the region of the scattered electron beams will cause a negligible phase shift as long as the ratio of electrode length to the transverse feature-size aperture is about 5:1. Calculations are underway to determine the feasibility of aspect smaller aspect ratios of about 3:1 and about 2:1.

REFERENCES:
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patent: 2002/0130276 (2002-09-01), Sogard
patent: 2003/0066964 (2003-04-01), Nagayama et al.
patent: 2003/0132383 (2003-07-01), Benner
patent: 0 782 170 (1997-07-01), None

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