scholarly journals Quantitative ADF-STEM and STEM-EELS at the atomic level

2014 ◽  
Vol 70 (a1) ◽  
pp. C1450-C1450
Author(s):  
Christian Dwyer
Keyword(s):  
Quantitative Imaging ◽  
Dark Field ◽  
Core Level ◽  
Chemical Mapping ◽  
Transmission Electron ◽  
Experimental Parameters ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
Quantitative Basis ◽  
Electron Energy Loss

The ability to count, locate and distinguish the atoms in a material is one of the ultimate pursuits of nanomaterials characterization. In recent decades, significant advances toward this goal have occurred in the field of scanning transmission electron microscopy (STEM), with the establishment of a class of imaging modes capable of ~0.1 nm spatial resolution and high chemical sensitivity. High-angle annular dark-field (ADF) imaging and chemical mapping via core-level spectroscopy are prominent techniques in this class, with applicability to a wide variety of nanostructured materials, such as nanoparticles, interfaces, and embedded phases. With such advances comes the ability to perform fully quantitative imaging for unprecedented accuracy in nanostructure characterization. However, full realization of this goal requires that we must be able to isolate and quantify all of the experimental parameters pertinent to imaging at 0.1 nm resolution, so that the only remaining unknown is the nanostructure itself. This is demonstrated in the present work. We present a systematic study of the influence of experimental factors pertinent to 0.1 nm ADF-STEM. We demonstrate that ADF-STEM images can be interpreted on a quantitative basis, in terms of the number, positions and species of atoms in the material, *without* recourse to adjustable parameters [1]. The figure presents a demonstration for [001]-oriented LaB6. A similar demonstration will be shown for atomic-resolution chemical mapping based on core-level electron energy-loss spectroscopy (EELS) [2]. The approach demonstrated here improves on previous works by removing instrumental unknowns from the analysis. Applications of this approach will be presented.

Atomic Ordering and Disordering of Amorphous CoNiP Alloy

2018 ◽  
Vol 386 ◽  
pp. 377-382
Author(s):  
Evgenii V. Pustovalov ◽  
Alexander F. Fedorets ◽  
Vladimir V. Tkachev ◽  
Vladimir S. Plotnikov
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Scanning Transmission Electron Microscopy ◽  
Dark Field ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
Electron Energy Loss ◽  
Temperature Heating ◽  
Thermal Stability Of

The structure of electrolytically deposited nanocrystalline alloys of the CoP-CoNiP systems under low-temperature heating was investigated by means of high-resolution transmission electron microscopy (HRTEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF STEM), and analytical methods such as energy dispersive x-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS). Structural relaxation and crystallization were investigated at temperatures from 150°C to 300°C. Structural and compositional inhomogeneities were found in the CoP-CoNiP alloys, while the local changes in composition were found to reach 15 at.%. Nanocrystals in the alloys grew most intensely in the presence of a free surface. It was determined that the local diffusion coefficient ranged from 1.2 to 2.4 10−18 m2/s, which could be explained by the surface diffusion prevalence. The data gathered in these investigations can be further used to predict the thermal stability of CoP-CoNiP alloys.

scholarly journals Quantitative Chemical Mapping of InGaN Quantum Wells from Calibrated High-Angle Annular Dark Field Micrographs

2015 ◽  
Vol 21 (4) ◽  
pp. 994-1005 ◽  
Author(s):  
Daniel Carvalho ◽  
Francisco M. Morales ◽  
Teresa Ben ◽  
Rafael García ◽  
Andrés Redondo-Cubero ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Dark Field ◽  
Successful Implementation ◽  
Chemical Mapping ◽  
High Angle ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
Dark Field Micrographs ◽  
Ingan Quantum Wells

AbstractWe present a simple and robust method to acquire quantitative maps of compositional fluctuations in nanostructures from low magnification high-angle annular dark field (HAADF) micrographs calibrated by energy-dispersive X-ray (EDX) spectroscopy in scanning transmission electron microscopy (STEM) mode. We show that a nonuniform background in HAADF-STEM micrographs can be eliminated, to a first approximation, by use of a suitable analytic function. The uncertainty in probe position when collecting an EDX spectrum renders the calibration of HAADF-STEM micrographs indirect, and a statistical approach has been developed to determine the position with confidence. Our analysis procedure, presented in a flowchart to facilitate the successful implementation of the method by users, was applied to discontinuous InGaN/GaN quantum wells in order to obtain quantitative determinations of compositional fluctuations on the nanoscale.

Analytical High-Resolution TEM Study on Au/TiO2 Catalysts

1999 ◽  
Vol 589 ◽  
Author(s):  
T. Akita ◽  
K. Tanaka ◽  
S. Tsubota ◽  
M. Haruta
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Transmission Electron Microscope ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
High Resolution Tem ◽  
Electron Energy Loss

AbstractHRTEM(High-Resolution Transmission Electron Microscope), HAADF-STEM (High Angle Annular Dark Field Scanning Transmission Electron Microscope) and EELS(Electron Energy Loss Spectroscopy) techniques were applied for the characterization of Au/TiO2 catalysts. HAADFSTEM provides precise size distributions for Au particles smaller than ∼2nm in diameter. It was observed that many small particles under 2nm were supported on anatase TiO2 having a large surface area. The HAADF-STEM method was examined as a way to measure the shape of Au particles. EELS measurements were also used to examine the interface between Au and TiO2 support to study electronic structure effects.

Microscopic Examination of SiO2/4H-SiC Interfaces

2011 ◽  
Vol 679-680 ◽  
pp. 330-333 ◽  
Author(s):  
Tetsuo Hatakeyama ◽  
Hirofumi Matsuhata ◽  
T. Suzuki ◽  
Takashi Shinohe ◽  
Hajime Okumura
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Scanning Transmission Electron Microscopy ◽  
Dark Field ◽  
Rich Region ◽  
Spatially Resolved ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
Electron Energy Loss

SiO2/4H-SiC interfaces are examined by high-resolution transmission electron microscopy (HRTEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), and spatially resolved electron energy-loss spectroscopy (EELS). HRTEM and HAADF-STEM images of SiO2/4H-SiC interfaces reveal that abrupt interfaces are formed irrespective of the fabrication conditions. Transition regions around the interfaces reported by Zheleva et al. were not observed. Using EELS, profiles of the C/Si and O/Si ratios across an interface were measured. Our measurements did not reveal a C-rich region on the SiC side of the interface, which was reported by Zheleva et al.

Materials analysis by aberration-corrected STEM

2004 ◽  
Vol 839 ◽  
Author(s):  
Ondrej L. Krivanek ◽  
Neil J. Bacon ◽  
George C. Corbin ◽  
Niklas Dellby ◽  
Andrew McManama-Smith ◽  
...  
Keyword(s):  
Spherical Aberration ◽  
Dark Field ◽  
Optical Aberration ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
Powerful Research Tool ◽  
Electron Microscopes ◽  
Electron Energy Loss ◽  
Aberration Corrected

ABSTRACTElectron-optical aberration correction has recently progressed from a promising concept to a powerful research tool. 100–120 kV scanning transmission electron microscopes (STEMs) equipped with spherical aberration (Cs) correctors now achieve sub-Å resolution in high-angle annular dark field (HAADF) imaging, and a 300 kV Cs-corrected STEM has reached 0.6 Å HAADF resolution. Moreover, the current available in an atom-sized probe has grown by about 10x, allowing electron energy loss spectroscopy (EELS) to detect single atoms. We summarize the factors that have made this possible, and outline likely future progress.

Design of a new objective lens for an HB-501A STEM

1991 ◽  
Vol 49 ◽  
pp. 416-417
Author(s):  
Earl J. Kirkland ◽  
Robert J. Keyse
Keyword(s):  
High Resolution ◽  
Spherical Aberration ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Objective Lens ◽  
Specimen Holder ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
High Resolution Microscopy

An ultra-high resolution pole piece with a coefficient of spherical aberration Cs=0.7mm. was previously designed for a Vacuum Generators HB-501A Scanning Transmission Electron Microscope (STEM). This lens was used to produce bright field (BF) and annular dark field (ADF) images of (111) silicon with a lattice spacing of 1.92 Å. In this microscope the specimen must be loaded into the lens through the top bore (or exit bore, electrons traveling from the bottom to the top). Thus the top bore must be rather large to accommodate the specimen holder. Unfortunately, a large bore is not ideal for producing low aberrations. The old lens was thus highly asymmetrical, with an upper bore of 8.0mm. Even with this large upper bore it has not been possible to produce a tilting stage, which hampers high resolution microscopy.

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