Regensburg 2013 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 11: Topical Session: TEM-Symposium - STEM
MM 11.9: Vortrag
Montag, 11. März 2013, 18:00–18:15, H4
Electrostatic Phase Plates for Transmission Electron Microscopy — •Simon Hettler1, Manuel Dries1, Nicole Frindt2, Rasmus R. Schröder2, and Dagmar Gerthsen1 — 1Laboratorium für Elektronenmikroskopie, KIT, Karlsruhe, Germany — 2BioQuant CellNetworks, Universität Heidelberg, Heidelberg, Germany
Physical phase plates (PP) for transmission electron microscopy (TEM) enhance phase contrast of (weak-)phase objects by inducing an additional relative phase shift between the scattered and unscattered electrons. The phase shift can be varied by the use of electrostatic PPs, which generate a variable electrostatic field at the zero-order beam position in the back focal plane. An important property of the PP is the cut-on frequency which limits the maximum size of the objects to be imaged with phase contrast. The cut-on frequency is determined by the spatial localization of the electrostatic field which can be optimized by adequate PP design. Moreover, obstruction of scattered electrons in the back focal plane by the PP structure as well as contamination and charging of the device additionally affect PP TEM.
We implemented a PP optimized in size and shape in a Zeiss 912 Omega transmission electron microscope. The obtained images of different samples show contrast enhancement and inversion. Charging and contamination is minimized using an integrated heating device in the vicinity of the PP. The inhomogeneous potential is analyzed and compared to simulations. The effect of inelastic scattering on phase contrast is studied.