STEM Analysis of Atom Location in (Cu, Au, Ni)6Sn5 Intermetallic Compounds

2018 ◽  
Vol 273 ◽  
pp. 95-100
Author(s):  
Wen Hui Yang ◽  
Tomokazu Yamamoto ◽  
Kazuhiro Nogita ◽  
Syo Matsumura
Keyword(s):  
Dark Field ◽  
Hexagonal Structure ◽  
Atomic Resolution ◽  
Chemical Mapping ◽  
Soldering Process ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
Direct Alloying ◽  
Resolution Level ◽  
Evolution Of Microstructure

Cu6Sn5 is an important intermetallic compound in soldering and electronic packaging. It is formed at the interface between molten solder and substrate during the soldering process, and the evolution of microstructure and properties also occurs in service. Previous studies revealed that Au and Ni are stabilization alloying elements for hexagonal η-Cu6Sn5 intermetallic. For better understanding of stabilization mechanisms at atomic resolution level, in this work, we made an attempt atomic structure analysis on a stoichiometric (Cu, Au, Ni)6Sn5 intermetallic prepared by direct alloying. High-angle annular dark-field (HAADF) imaging and atomic-resolution chemical mapping were taken by the aberration-corrected (Cs-corrected) scanning transmission electron microscopy (STEM). It is found that Au and Ni doped Cu6Sn5 has hexagonal structure. The atom sites of Cu1 and Sn can be distinguished in atomic-resolution images after being observed from orientation [2110], which is also confirmed by atomic-resolution chemical mapping analysis. Importantly, atomic-resolution about distribution of alloying Au atom was directly observed, and Au atoms occupy the Cu1 sites in η-Cu6Sn5.

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.

Origin of the superstructure elucidated by atomic resolution HAADF-STEM and HREM in the Ce10W22O81lanthanide tungstate phase

2018 ◽  
Vol 51 (2) ◽  
pp. 344-350 ◽  
Author(s):  
Loïc Patout ◽  
Abdelali Hallaoui ◽  
Thomas Neisius ◽  
Andrea P. C. Campos ◽  
Christian Dominici ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
High Resolution Electron Microscopy ◽  
Dark Field ◽  
Atomic Resolution ◽  
Orthorhombic Unit Cell ◽  
Transmission Electron ◽  
New Information ◽  
Resolution Electron ◽  
Scanning Transmission ◽  
Annular Dark Field

The present paper provides new information on the attribution of the cationic sites of the orthorhombic Ce10W22O81crystal phase prepared in the CeO2–Ce2O3–WO3ternary system. Atomic resolution HAADF-STEM (high-angle annular dark-field scanning transmission electron microscopy) and HREM (high-resolution electron microscopy) investigations have highlighted the presence of two mixed columns of Ce and W cations along theaaxis that were previously assigned to pure W cations in the asymmetric unit. This discovery explains the presence of a commensurate superstructure doubling the orthorhombic unit-cell lengthao.

scholarly journals Atomic Resolution Mapping Using Quantitative High-angle Annular Dark Field Scanning Transmission Electron Microscopy

2009 ◽  
Vol 15 (S2) ◽  
pp. 464-465 ◽  
Author(s):  
S Van Aert ◽  
J Verbeeck ◽  
S Bals ◽  
R Erni ◽  
D Van Dyck ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Scanning Transmission Electron Microscopy ◽  
Dark Field ◽  
Atomic Resolution ◽  
High Angle ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
Resolution Mapping

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

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.

Effect of strain on ADF-STEM high-resolution images

1991 ◽  
Vol 49 ◽  
pp. 666-667
Author(s):  
M. Kelly ◽  
D.M. Bird
Keyword(s):  
High Resolution ◽  
Strong Influence ◽  
Intensity Variation ◽  
Dark Field ◽  
Atomic Resolution ◽  
Strain Fields ◽  
High Resolution Image ◽  
Annular Dark Field ◽  
High Resolution Images ◽  
Interesting Alternative

It is well known that strain fields can have a strong influence on the details of HREM images. This, for example, can cause problems in the analysis of edge-on interfaces between lattice mismatched materials. An interesting alternative to conventional HREM imaging has recently been advanced by Pennycook and co-workers where the intensity variation in the annular dark field (ADF) detector is monitored as a STEM probe is scanned across the specimen. It is believed that the observed atomic-resolution contrast is correlated with the intensity of the STEM probe at the atomic sites and the way in which this varies as the probe moves from cell to cell. As well as providing a directly interpretable high-resolution image, there are reasons for believing that ADF-STEM images may be less suseptible to strain than conventional HREM. This is because HREM images arise from the interference of several diffracted beams, each of which is governed by all the excited Bloch waves in the crystal.

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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