2000Angert Zero Loss

Citation

Angert, I., Majorovits, E. and Schröder, R.R. 2000. Zero-loss image formation and modified contrast transfer theory in EFTEM. Ultramicroscopy. 81, 3-4 (2000), 203–222.

Abstract

For a weak phase/weak amplitude object the information transfer in the imaging process of TEM is described by the common formalism of the contrast transfer function (CTF). So far the e!ects of inelastic scattering were not accounted for in this formalism. In conventional imaging they were simply neglected. In energy "lteringTEM (EFTEM), where removal of inelastic electrons leads to higher specimen contrast, they were modelled by a global increase of the elastic amplitude contrast. Thus, the description of inelastic and elastic scattering was mixed. Here a new ansatz is proposed which treats elastic and inelastic contrast transfer separately by adding an inelastic contribution to the scattering potentials. In EFTEM this has the e!ect of adding a "lter contrast which depends on the characteristics of the inelastic scattering. For samples with dominant plasmon loss the additional "lter contrast is restricted to low resolution. Because of its strong dependence on the nature of the inelastic scattering process, the "lter contrast cannot in general be uni"ed with the conventional elastic amplitude contrast. The modi"ed CTF theory for EFTEM was tested experimentally on a variety of samples. Images of amorphous layers of copper, aluminium, and carbon "lms, as well as zero-loss images of proteins embedded in amorphous ice were evaluated. The values of the parameters of the additional "lter contrast were determined for carbon "lm and proteins embedded in vitri"ed ice. Comparison of di!erent CTF models used to reconstruct 3D volumes from zero-loss images con"rmed that best agreement with the atomic model is attained with the new, modi"ed CTF theory.

Links

https://www.sciencedirect.com/science/article/pii/S0304399199001904