PubMed Health⌕ Search

Biomedical subjects

Christoph T Koch

Publications and source records attributed to Christoph T Koch.

2 recordsLinked to original sources

Projected potential profiles across interfaces obtained by reconstructing the exit face wave function from through focal series.

An iterative method for reconstructing the exit face wave function from a through focal series of transmission electron microscopy image line profiles across an interface is presented. Apart from high-resolution images recorded with small changes in defocus, this method works also well for a large defocus range as used for Fresnel imaging. Using the phase-object approximation the projected electrostatic as well as the absorptive potential profiles across an interface are determined from this exit face wave function. A new experimental image alignment procedure was developed in order to align images with large relative defocus shift. The performance of this procedure is shown to be superior to other image alignment procedures existing in the literature. The reconstruction method is applied to both simulated and experimental images.

Journal Article↗

Solving non-centrosymmetric two-dimensional crystal structures by dynamic electron diffraction.

Despite the fast increase in expertise developed in the field of electron crystallography, dynamic scattering effects still remain a severe obstacle in this field, a hurdle that is being circumvented rather than fully tackled. In this paper, a new way of straightforward interpretation of conventional many-beam zone-axis dynamical electron diffraction patterns is presented that helps to solve the phase problem for non-centrosymmetric two-dimensional crystal structures, in particular if these contain only a few heavier atoms. While the implementation of this method is easiest for fairly weak multiple scattering, its extension to arbitrarily strong dynamical effects is mentioned. A method to obtain high-resolution diffraction data in the presence of specimen bending is proposed.

Journal Article↗