Environmental Optimization for Sub-0.2NM Scanning Transmission Electron Microscopy

2000 ◽  
Vol 6 (S2) ◽  
pp. 110-111
Author(s):  
D. A. Muller ◽  
J. Grazul ◽  
F. H. Baumann ◽  
R. Hynes ◽  
T. L. Hoffman
Keyword(s):  
Electromagnetic Interference ◽  
Dark Field ◽  
Limiting Factors ◽  
Scanning System ◽  
Dark Field Imaging ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
Electrical Loads ◽  
Field Imaging

Sub-0.2 nm probes can now be readily obtained on Schottky field-emission microscopes[1]. However environmental instabilities are proving to be the limiting factors for atomic resolution spectroscopy and distortion-free annular-dark field imaging, as a result of the long acquisition times (comparable to those required for inline holography[2]), and from the serial nature of the scanning system where instabilities result in image distortions rather than reductions in contrast. Troubleshooting the two most common environmental problems are discussed here.Electromagnetic interference can cause beam deflections in both the scanning system and the spectrometer [3](< 0.3 mG r.ms for 0.3nm, < 0.2 mG for 0.2 nm). These are most easily dealt with before the machine is installed, as substantial rewiring may be necessary. There is little that can be done about quasi-DC fields, such as from elevators and nearby trains and buses. Major sources of AC electromagnetic interference are unbalanced electrical loads.

scholarly journals Annular Dark Field Imaging of Catalyst Nanoparticles in Single Shot Dynamic Transmission Electron Microscopy

2009 ◽  
Vol 15 (S2) ◽  
pp. 1082-1083
Author(s):  
D Masiel ◽  
B Reed ◽  
T LaGrange ◽  
ND Browning
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Dark Field ◽  
Single Shot ◽  
Catalyst Nanoparticles ◽  
Dark Field Imaging ◽  
Transmission Electron ◽  
Annular Dark Field ◽  
Field Imaging

Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009

Structure and Chemistry across Interfaces at Nanoscale of a Ge Quantum Well Embedded within Rare Earth Oxide Layers

2011 ◽  
Vol 17 (5) ◽  
pp. 759-765 ◽  
Author(s):  
Tanmay Das ◽  
Somnath Bhattacharyya
Keyword(s):  
Rare Earth ◽  
Solid Phase ◽  
Rare Earth Oxide ◽  
Dark Field ◽  
X Ray ◽  
Dark Field Imaging ◽  
Transmission Electron ◽  
Annular Dark Field ◽  
Electron Energy Loss ◽  
Field Imaging

AbstractStructure and chemistry across the rare earth oxide-Ge interfaces of a Gd2O3-Ge-Gd2O3 heterostructure grown on p-Si (111) substrate using encapsulated solid phase epitaxy method have been studied at nanoscale using various transmission electron microscopy methods. The structure across both the interfaces was investigated using reconstructed phase and amplitude at exit plane. Chemistry across the interfaces was explored using elemental mapping, high-angle annular dark-field imaging, electron energy loss spectroscopy, and energy dispersive X-ray spectrometry. Results demonstrate the structural and chemical abruptness of both the interfaces, which is most essential to maintain the desired quantum barrier structure.

Annular Dark Field Imaging in Stem

1994 ◽  
Vol 332 ◽  
Author(s):  
Sean Hillyard ◽  
John Silcox
Keyword(s):  
Phonon Scattering ◽  
Dark Field ◽  
Probe Intensity ◽  
Dark Field Imaging ◽  
Quantitative Measurements ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
Computer Based ◽  
Diffraction Patterns

ABSTRACTAnnular dark field scanning transmission electron microscopy (ADF STEM) is chemically sensitive at high spatial resolution (e.g., 1.8ë at 100keV). Images can be digitally acquired and recorded, permitting quantitative analysis. It is particularly powerful when used in combination with complementary analysis modes such as x-ray microanalysis and transmission electron energy loss spectroscopy. Critical to the interpretation of these data is an understanding and determination of the electron probe intensity, shape and propagation characteristics inside the specimen. Quantitative measurements of diffraction patterns and images in comparison with computer-based simulations (including phonon scattering) provide a basis for developing that information. Results of a series of studies are reviewed that address questions such as defocus and other instrumental factors, and also the formation of channeling peaks that appear on the atomic columns along zone axes. For example, along Si(100) a peak forms and penetrates over 500ë whereas along Ge(100) it developes rapidly but disappears in less than 200ë. In higher atomic number elements, the penetration is even less (e.g. 1 O0ë for In).

scholarly journals Atomic-Scale Characterization of Commensurate and Incommensurate Vacancy Superstructures in Natural Pyrrhotites

2021 ◽  
Vol 106 (1) ◽  
pp. 82-96 ◽  
Author(s):  
Lei Jin ◽  
Dimitrios Koulialias ◽  
Michael Schnedler ◽  
Andreas U. Gehring ◽  
Mihály Pósfai ◽  
...  
Keyword(s):  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Atomic Scale ◽  
Past Century ◽  
Dark Field Imaging ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
Local Measurements ◽  
Scale Characterization

Abstract Pyrrhotites, characterized by the chemical formula Fe1–δS (0 &lt; δ ≤ 1/8), represent an extended group of minerals that are derived from the NiAs-type FeS aristotype. They contain layered arrangements of ordered Fe vacancies, which are at the origin of the various magnetic signals registered from certain natural rocks and can act as efficient electrocatalysts in oxygen evolution reactions in ultrathin form. Despite extensive studies over the past century, the local structural details of pyrrhotite superstructures formed by different arrangements of Fe vacancies remain unclear, in particular at the atomic scale. Here, atomic-resolution high-angle annular dark-field imaging and nanobeam electron diffraction in the scanning transmission electron microscope are used to study natural pyrrhotite samples that contain commensurate 4C and incommensurate 4.91 ± 0.02C constituents. Local measurements of both the intensities and the picometer-scale shifts of individual Fe atomic columns are shown to be consistent with a model for the structure of 4C pyrrhotite, which was derived using X-ray diffraction by Tokonami et al. (1972). In 4.91 ± 0.02C pyrrhotite, 5C-like unequally sized nano-regions are found to join at anti-phase-like boundaries, leading to the incommensurability observed in the present pyrrhotite sample. This conclusion is supported by computer simulations. The local magnetic properties of each phase are inferred from the measurements. A discussion of perspectives for the quantitative counting of Fe vacancies at the atomic scale is presented.

Theoretical considerations in lattice resolution high-angle annular dark-field imaging

1992 ◽  
Vol 50 (2) ◽  
pp. 1226-1227
Author(s):  
Adam Amali ◽  
Peter Rez
Keyword(s):  
Large Angle ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Theoretical Interpretation ◽  
High Angle ◽  
Dark Field Imaging ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
Lattice Resolution

The highly coherent probe in the scanning transmission electron microscope(STEM) equipped with a with high angle annular dark field (HAADF) detector has become an important tool for high resolution work in the study of crystals.with potential for providing chemically sensitive information.The results of Pennycook and Boatner and the calculations of Kirkland et al clearly demonstrated that lattice resolution was possible using HAADF imaging.There has been other contributions since then.The theoretical interpretation of these images however remains controversial and other contributions have focussed on whether the imaging is coherent or incoherent.In the present work we analyse the various mechanisms that contribute to the large angle signal obtained in the HAADF detector.Bloch waves are used to describe the elastic dynamical scattering; and in the abscence of any strong Bragg reflections.the amplitude observed in the detector plane in the STEM may be represented by a simple convolution between the scattering function of the object and the probe.

Sign in / Sign up

Export Citation Format

Share Document