Search results for "electron tomography"
showing 6 items of 16 documents
“Ab-initio” structure solution of nano-crystalline minerals and synthetic materials by automated electron tomography
2012
Most of the newly discovered mineral phases, as well as many new synthesized industrial materials, appear only in the form of nano crystals, with a size not sufficient for single-crystal x-ray structure analysis. The development of techniques able to investigate the structure of nano crystalline materials is therefore one of the most important frontiers of crystallography. The most widespread technique providing relatively fast and well consolidated routes for structure analysis of bulk materials is x-ray powder diffraction (XRPD). Nevertheless, XRPD suffers from intrinsic 1-dimension reduction of information that greatly limits its applicability in presence of peak broadening and overlappi…
Comparison of the decameric structure of peroxiredoxin-II by transmission electron microscopy and X-ray crystallography
2001
Abstract The decameric human erythrocyte protein torin is identical to the thiol-specific antioxidant protein-II (TSA-II), also termed peroxiredoxin-II (Prx-II). Single particle analysis from electron micrographs of Prx-II molecules homogeneously orientated across holes in the presence of a thin film of ammonium molybdate and trehalose has facilitated the production of a ≥20 A 3-D reconstruction by angular reconstitution that emphasises the D5 symmetry of the ring-like decamer. The X-ray structure for Prx-II was fitted into the transmission electron microscopic reconstruction by molecular replacement. The surface-rendered transmission electron microscopy (TEM) reconstruction correlates well…
3D superconducting hollow nanowires with tailored diameters grown by focused He+ beam direct writing
2020
Currently, the patterning of innovative three-dimensional (3D) nano-objects is required for the development of future advanced electronic components. Helium ion microscopy in combination with a precursor gas can be used for direct writing of three-dimensional nanostructures with a precise control of their geometry, and a significantly higher aspect ratio than other additive manufacturing technologies. We report here on the deposition of 3D hollow tungsten carbide nanowires with tailored diameters by tuning two key growth parameters, namely current and dose of the ion beam. Our results show the control of geometry in 3D hollow nanowires, with outer and inner diameters ranging from 36 to 142 …
Image enhancement in photoemission electron microscopy by means of imaging time-of-flight analysis
2004
Abstract Photoemission electron microscopy (PEEM) is widely used in combination with synchrotron sources as a powerful tool to observe chemical and magnetic properties of metal and semiconductor surfaces. Presently, the resolution limit of these instruments using soft-X-ray excitation is limited to about 50 nm, because of the chromatic aberation of the electron optics used. Various sophisticated approaches have thus been reported for enhancing the spatial resolution in photoemission electron microscopy. This work demonstrates the use of a simple imaging energy filter based on electron time-of-flight (ToF) selection. The spatial resolution could be improved dramatically, even though the inst…
Engineering 3D ordered molecular thin films by a nanoscale control
2010
This perspective aims to report on experimental preparation and investigation tools for engineering molecular thin films with a three-dimensional (3D) nanoscale control that is of relevant interest for different emerging applications as well as for the development of calibration standards. Such thin films may be obtained by man-made methods, self-assembly or spatio-temporal self-organization and/or by the combination of these last approaches with external tools. Understanding the main features and the physical-chemistry underlying the related ordering phenomena is in due course and a theoretical framework is under development. In this respect it is of fundamental importance to achieve the a…