title: Development and Implementation of In-Focus Phase Contrast TEM for Materials and Life Sciences
creator: Barton, Bastian
subject: ddc-530
subject: 530 Physics
description: Transmission electron microscopy (TEM) allows the imaging of objects from materials sciences and biology with a resolution of a few nm to a few Å. Biological systems can be reconstructed in 3D under physiological conditions using cryo TEM. However, the low signal-to-noise ratio (SNR) of individual images hampers resolution. Weak-phase objects such as native biological samples can be visualized only by phase contrast, which is generated in conventional TEM by defocusing. The defocus technique yields weak contrast and incomplete transfer of object information, which makes reconstruction difficult. Therefore, generating contrast by placing a phase plate in the back focal plane of the objective lens is desirable. This allows for artefact-free imaging of weak-phase objects with strong contrast. For TEM, phase plates have been realised only in the form of a thin carbon film which causes loss of signal and resolution. This work presents the first technical implementation of an electrostatic (Boersch) phase plate for TEM and gives the experimental proof-of-principle for this device. The Boersch phase plate generates maximum phase contrast while avoiding resolution loss. It consists of a miniaturised electrostatic einzel lens that shifts the phase of the unscattered wave. Obstruction effects are minimised by optically magnifying the focal plane. The advancement to an entirely obstruction-free phase plate is outlined which generates pseudo-topographic (Hilbert) contrast. The enhancement of electron-microscopic reconstruction by such a Hilbert phase plate is demonstrated for electron tomography of unstained cell sections. 
date: 2008
type: Dissertation
type: info:eu-repo/semantics/doctoralThesis
type: NonPeerReviewed
format: application/pdf
identifier: https://archiv.ub.uni-heidelberg.de/volltextserverhttps://archiv.ub.uni-heidelberg.de/volltextserver/8514/1/2Doktorarbeit_Bastian_Barton.pdf
identifier: DOI:10.11588/heidok.00008514
identifier: urn:nbn:de:bsz:16-opus-85146
identifier:   Barton, Bastian  (2008) Development and Implementation of In-Focus Phase Contrast TEM for Materials and Life Sciences.  [Dissertation]     
relation: https://archiv.ub.uni-heidelberg.de/volltextserver/8514/
rights: info:eu-repo/semantics/openAccess
rights: http://archiv.ub.uni-heidelberg.de/volltextserver/help/license_urhg.html
language: eng