PHASE SHIFT METHOD FOR A TEM

摘要

A method of electron microcopy passes an electron beam through a phase plate, specifically a Zernike type phase plate, comprising a central hole, and a thin film causing a phase shift of the electrons passing through said film. This phase shift causes the Contrast Transfer Function (CTF) to change from a sine-like function to a cosine-like function. The phase plate is equipped with a film in the form of an annulus, carried by a much thinner film. As a result only in a small spatial frequency range (for low frequencies) the phase is changed (and thus the CTF), and for other spatial frequencies the phase shift is negligible, and thus the CTF remains unchanged. Due to the much smaller thickness of the carrier film the scattering of electrons is negligible as well.

主权项

1. A method of imaging a sample in a charged particle beam system, the method comprising:
directing a beam of electrons through a sample, the passage deflecting some of the electrons in the beam; passing the beam of electrons from the sample through a phase plate having three regions, each of the three regions having a different effect on the phase of the electrons passing through the region; and combining the electrons that pass through the three regions to form an image having improved contrast.