scholarly journals A symmetry-derived mechanism for atomic resolution imaging

2020 ◽  
Vol 117 (45) ◽  
pp. 27805-27810
Author(s):  
Matus Krajnak ◽  
Joanne Etheridge
Keyword(s):  
Electron Probe ◽  
Local Symmetry ◽  
Symmetry Operation ◽  
Specimen Thickness ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Contrast Mechanism ◽  
Electron Intensity ◽  
Resolution Imaging ◽  
Degree Of Similarity

We introduce an image-contrast mechanism for scanning transmission electron microscopy (STEM) that derives from the local symmetry within the specimen. For a given position of the electron probe on the specimen, the image intensity is determined by the degree of similarity between the exit electron-intensity distribution and a chosen symmetry operation applied to that distribution. The contrast mechanism detects both light and heavy atomic columns and is robust with respect to specimen thickness, electron-probe energy, and defocus. Atomic columns appear as sharp peaks that can be significantly narrower than for STEM images using conventional disk and annular detectors. This fundamentally different contrast mechanism complements conventional imaging modes and can be acquired simultaneously with them, expanding the power of STEM for materials characterization.

1250-kilovolt scanning transmission electron microscope

1984 ◽  
Vol 42 ◽  
pp. 624-625
Author(s):  
T. Imura ◽  
S. Maruse ◽  
K. Mihama ◽  
M. Iseki ◽  
M. Hibino ◽  
...  
Keyword(s):  
High Voltage ◽  
Electron Probe ◽  
Scanning Transmission Electron Microscope ◽  
Pressure Vessels ◽  
Practical Applications ◽  
Voltage Generator ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
New Applications ◽  
High Voltage Generator

Ultra high voltage STEM has many inherent technical advantages over CTEM. These advantages include better signal detectability and signal processing capability. It is hoped that it will explore some new applications which were previously not possible. Conventional STEM (including CTEM with STEM attachment), however, has been unable to provide these inherent advantages due to insufficient performance and engineering problems. Recently we have developed a new 1250 kV STEM and completed installation at Nagoya University in Japan. It has been designed to break through conventional engineering limitations and bring about theoretical advantage in practical applications.In the design of this instrument, we exercised maximum care in providing a stable electron probe. A high voltage generator and an accelerator are housed in two separate pressure vessels and they are connected with a high voltage resistor cable.(Fig. 1) This design minimized induction generated from the high voltage generator, which is a high frequency Cockcroft-Walton type, being transmitted to the electron probe.

scholarly journals Chemical Quantification of Atomic-Scale EDS Maps under Thin Specimen Conditions

2014 ◽  
Vol 20 (6) ◽  
pp. 1782-1790 ◽  
Author(s):  
Ping Lu ◽  
Eric Romero ◽  
Shinbuhm Lee ◽  
Judith L. MacManus-Driscoll ◽  
Quanxi Jia
Keyword(s):  
Atomic Scale ◽  
Specimen Thickness ◽  
Peak Width ◽  
Thin Specimen ◽  
Gaussian Peak ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
The Relationship ◽  
Chemical Quantification

AbstractWe report our effort to quantify atomic-scale chemical maps obtained by collecting energy-dispersive X-ray spectra (EDS) using scanning transmission electron microscopy (STEM) (STEM-EDS). With thin specimen conditions and localized EDS scattering potential, the X-ray counts from atomic columns can be properly counted by fitting Gaussian peaks at the atomic columns, and can then be used for site-by-site chemical quantification. The effects of specimen thickness and X-ray energy on the Gaussian peak width are investigated using SrTiO3 (STO) as a model specimen. The relationship between the peak width and spatial resolution of an EDS map is also studied. Furthermore, the method developed by this work is applied to study cation occupancy in a Sm-doped STO thin film and antiphase boundaries (APBs) present within the STO film. We find that Sm atoms occupy both Sr and Ti sites but preferably the Sr sites, and Sm atoms are relatively depleted at the APBs likely owing to the effect of strain.

Single-atom electron microscopy for energy-related nanomaterials

2020 ◽  
Vol 8 (32) ◽  
pp. 16142-16165 ◽  
Author(s):  
Mingquan Xu ◽  
Aowen Li ◽  
Meng Gao ◽  
Wu Zhou
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Scanning Transmission Electron Microscopy ◽  
Atomic Resolution ◽  
Single Atom ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Resolution Imaging ◽  
Imaging And Spectroscopy ◽  
Atom Level

The advances in aberration correction have enabled atomic-resolution imaging and spectroscopy in scanning transmission electron microscopy (STEM) under low primary voltages and pushed their detection limit down to the single-atom level.

scholarly journals Structural Evolution of Ni-Based Co-Catalysts on [Ca2Nb3O10]− Nanosheets during Heating and Their Photocatalytic Properties

Catalysts ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 13 ◽  
Author(s):  
Siyuan Zhang ◽  
Leo Diehl ◽  
Sina Wrede ◽  
Bettina V. Lotsch ◽  
Christina Scheu
Keyword(s):  
Ostwald Ripening ◽  
Structural Evolution ◽  
Scanning Transmission Electron Microscope ◽  
Ex Situ ◽  
Shell Nanoparticles ◽  
Co Catalysts ◽  
Nickel Compounds ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Resolution Imaging

Nickel compounds are among the most frequently used co-catalysts for photocatalytic water splitting. By loading Ni(II) precursors, submonolayer Ni(OH)2 was uniformly distributed onto photocatalytic [Ca2Nb3O10]− nanosheets. Further heating of the nanocomposite was studied both ex situ in various gas environments and in situ under vacuum in the scanning transmission electron microscope. During heating in non-oxidative environments including H2, argon and vacuum, Ni nanoparticles form at ≥200 °C, and they undergo Ostwald ripening at ≥500 °C. High resolution imaging and electron energy loss spectroscopy revealed a NiO shell around the Ni core. Ni loading of up to 3 wt% was demonstrated to enhance the rates of photocatalytic hydrogen evolution. After heat treatment, a further increase in the reaction rate can be achieved thanks to the Ni core/NiO shell nanoparticles and their large separation.

scholarly journals Segmentation of Static and Dynamic Atomic-Resolution Microscopy Data Sets with Unsupervised Machine Learning Using Local Symmetry Descriptors

2021 ◽  
pp. 1-11
Author(s):  
Ning Wang ◽  
Christoph Freysoldt ◽  
Siyuan Zhang ◽  
Christian H. Liebscher ◽  
Jörg Neugebauer
Keyword(s):  
Machine Learning ◽  
Feature Space ◽  
Local Symmetry ◽  
Atomic Resolution ◽  
Video Sequences ◽  
Data Sets ◽  
Unsupervised Machine Learning ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Microscopy Data

We present an unsupervised machine learning approach for segmentation of static and dynamic atomic-resolution microscopy data sets in the form of images and video sequences. In our approach, we first extract local features via symmetry operations. Subsequent dimension reduction and clustering analysis are performed in feature space to assign pattern labels to each pixel. Furthermore, we propose the stride and upsampling scheme as well as separability analysis to speed up the segmentation process of image sequences. We apply our approach to static atomic-resolution scanning transmission electron microscopy images and video sequences. Our code is released as a python module that can be used as a standalone program or as a plugin to other microscopy packages.

Determination of Crystal Thickness from Relative Transmission Measurements

1975 ◽  
Vol 33 ◽  
pp. 242-243 ◽  
Author(s):  
D. C. Joy ◽  
D. M. Maher
Keyword(s):  
Amorphous Materials ◽  
Accurate Estimate ◽  
Foil Thickness ◽  
Specimen Thickness ◽  
Crystal Thickness ◽  
Crystalline Materials ◽  
Transmission Electron ◽  
Relative Transmission ◽  
History Of ◽  
Electron Intensity

An accurate knowledge of the specimen foil thickness often is required in quantitative transmission electron microscopy. The methods used for thickness determinations of thin crystalline materials (e.g. the trace method, thickness fringe counts and stereoscopic measurements) generally are selected according to the history of the specimen and nature of the microstructure. For amorphous materials a measurement of the relative transmission of electrons I/I0, where I is the transmitted and I0 the incident electron intensity, affords an accurate estimate of the specimen thickness. In this case, for a sufficiently large specimen thickness, I/I0 varies exponentially according to the mass thickness relationship e-μt, where μ is the mass absorption coefficient and t is the specimen thickness. The purpose of this paper is to demonstrate that the thickness of a crystalline specimen also may be determined accurately from a measurement of I/I0, provided that well defined diffracting conditions are used. The results presented here are for silicon.

Surface resonance channelling in scanning reflection electron microscopy

1988 ◽  
Vol 46 ◽  
pp. 692-693
Author(s):  
J.M. Cowley ◽  
P.A. Crozier
Keyword(s):  
Electron Microscopy ◽  
Crystal Surface ◽  
Scanning Transmission Electron Microscope ◽  
Diffraction Effect ◽  
Transmission Electron ◽  
Surface Resonance ◽  
Scanning Transmission ◽  
Reflection Electron Microscopy ◽  
Resolution Imaging ◽  
Electron Energy Loss

The phenomena of the channelling of electrons along planes or rows of atoms in the surface layers of crystals has been investigated recently in relation to microdiffraction and RHEED, REM, (reflection electron microscopy) and REELS (reflection electron energy loss spectroscopy) by using a conventional TEM in the reflection mode.The renewed interest in this phenomenon, known for many years, is the evidence from calculations of dynamical diffraction effect at surfaces that the electrons may be channelled along the topmost layers of atoms on a crystal surface and that the RHEED, REM and REELS signals may thus be sensitive to the structure and composition of the surface layer. These techniques may therefore provide a powerful new approach to the study of surfaces in which surface microanalysis and diffraction studies may be combined with nanometer-resolution imaging.An investigation has now been made of the analogous techniques which may be applied to the study of surfaces by use of a scanning transmission electron microscope.

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