scholarly journals Application of Z-Contrast Imaging to Obtain Column-by-Column Spectroscopic Analysis of Materials

1992 ◽  
Vol 295 ◽  
Author(s):  
Nigel D. Browning ◽  
Stephen J. Pennycook
Keyword(s):  
Spatial Resolution ◽  
Electron Probe ◽  
Materials Science ◽  
Detection System ◽  
Image Interpretation ◽  
Core Loss ◽  
Scanning Transmission Electron Microscope ◽  
Contrast Imaging ◽  
Experimental Conditions ◽  
Z Contrast

AbstractZ-contrast imaging has been shown to be an effective method for obtaining a highresolution image from a scanning transmission electron microscope (STEM). The incoherent nature of the high-angle scattering makes image interpretation straightforward and intuitive with the resolution limited only by the 2.2 Å electron probe. The optimum experimental conditions for Z-contrast imaging also coincide with those used for analytical microscopy, enabling microanalysis to be performed with the same spatial resolution as the image. The detection limits afforded by a parallel detection system for electron energy loss spectroscopy (EELS) allows column-by-column core-loss spectroscopy to be performed using the Z-contrast image to position the electron probe. Preliminary results from the study of Yba2Cu3O7-δ illustrate the spatial resolution available with this technique and the potential applications for materials science.

Incoherent Stem Imaging at 1.5 Å Resolution With A 200 Kv FEGTEM

1999 ◽  
Vol 5 (S2) ◽  
pp. 610-611
Author(s):  
E.M. James ◽  
N.D. Browning
Keyword(s):  
Spatial Resolution ◽  
Image Interpretation ◽  
Dark Field ◽  
Contrast Imaging ◽  
Contrast Method ◽  
Transmission Electron ◽  
Annular Dark Field ◽  
Z Contrast ◽  
First Time ◽  
Electron Energy Loss

Here we demonstrate sub- 1.5 Å resolution in compositionally sensitive high-angle annular dark-field (HAADF) (“Z-contrast”) imaging. For the first time this has been achieved on a 200 kV field-emission transmission electron microscope (FEGTEM), the JEOL JEM-2010F. With a Gatan imaging filter, this type of instrument is then capable of both analytical imaging and electron energy-loss spectroscopy at similar spatial resolution as in the 300 kV dedicated STEM.The Z-contrast imaging technique has a spatial resolution given by the size of the electron probe. When used to image periodic specimens and their defects, the effective incoherent nature of the Z-contrast method leads to higher resolution for given lens Cs, higher sensitivity to atomic number and easier qualitative image interpretation than in HRTEM.In practice, the ability to form a small (atomic resolution) probe depends on the brightness of the electron source, and achieving low enough levels of mechanical and electrical instabilities that otherwise incoherently broaden the probe.

Incoherent High-Resolution Z-Contrast Imaging of Silicon and Gallium Arsenide Using HAADF-STEM

1999 ◽  
Vol 589 ◽  
Author(s):  
Y Kotaka ◽  
T. Yamazaki ◽  
Y Kikuchi ◽  
K. Watanabe
Keyword(s):  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Contrast Imaging ◽  
High Spatial Resolution Image ◽  
Transmission Electron ◽  
Eigen Value ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
Convergent Beam ◽  
Z Contrast

AbstractThe high-angle annular dark-field (HAADF) technique in a dedicated scanning transmission electron microscope (STEM) provides strong compositional sensitivity dependent on atomic number (Z-contrast image). Furthermore, a high spatial resolution image is comparable to that of conventional coherent imaging (HRTEM). However, it is difficult to obtain a clear atomic structure HAADF image using a hybrid TEM/STEM. In this work, HAADF images were obtained with a JEOL JEM-2010F (with a thermal-Schottky field-emission) gun in probe-forming mode at 200 kV. We performed experiments using Si and GaAs in the [110] orientation. The electron-optical conditions were optimized. As a result, the dumbbell structure was observed in an image of [110] Si. Intensity profiles for GaAs along [001] showed differences for the two atomic sites. The experimental images were analyzed and compared with the calculated atomic positions and intensities obtained from Bethe's eigen-value method, which was modified to simulate HAADF-STEM based on Allen and Rossouw's method for convergent-beam electron diffraction (CBED). The experimental results showed a good agreement with the simulation results.

Analysis of the Atomic Scale Defect Chemistry in Oxygen Deficient Materials by STEM

1999 ◽  
Vol 589 ◽  
Author(s):  
Y. Ito ◽  
S. Stemmer ◽  
R. F. Klie ◽  
N. D. Browning ◽  
A. Sane ◽  
...  
Keyword(s):  
Preliminary Investigation ◽  
High Mobility ◽  
Scanning Transmission Electron Microscope ◽  
Defect Chemistry ◽  
Atomic Scale ◽  
Contrast Imaging ◽  
Separation Membranes ◽  
Oxidation Reduction ◽  
Scanning Transmission ◽  
Z Contrast

AbstractThe high mobility of anion vacancies in oxygen deficient perovskite type materials makes these ceramics potential candidates for oxygen separation membranes. As a preliminary investigation of the defect chemistry in these oxides, we show here the analysis of SrCoO3−σ using atomic resolution Z-contrast imaging and electron energy loss spectroscopy in the scanning transmission electron microscope. In particular, after being subjected to oxidation/reduction cycles at high temperatures we find the formation of ordered microdomains with the brownmillerite structure.

Quantification of Compositional Modulations in Self-Assembled Multisheet (Cd, Zn, Mn)Se Quantum Dot Structures

2001 ◽  
Vol 7 (S2) ◽  
pp. 202-203
Author(s):  
T. Topuria ◽  
P. Möck ◽  
N.D. Browning ◽  
L.V. Titova ◽  
M. Dobrowolska ◽  
...  
Keyword(s):  
Quantum Dot ◽  
Imaging Technique ◽  
Optoelectronic Device ◽  
Scanning Transmission Electron Microscope ◽  
Contrast Imaging ◽  
Cdse Qds ◽  
Scanning Transmission ◽  
Device Applications ◽  
Incoherent Imaging ◽  
Z Contrast

CdSe/ZnSe based semiconductor quantum dot (Q D) structures are a promising candidate for optoelectronic device applications. However, key to the luminescence properties is the cation distribution and ordering on the atomic level within the CdSe QDs/agglomerates. Here the Z contrast imaging technique in the scanning transmission electron microscope (STEM) is employed to study multisheet (Cd,Zn,Mn)Se QD structures. Since Z-contrast is an incoherent imaging technique, problems associated with strain contrast in conventional TEM are avoided an accurate size and composition determinations can be made.For this work we used a JEOL JEM 201 OF field emission STEM/TEM. The sample was grown by molecular beam epitaxy in order to achieve vertical self-ordering of Cd rich quasi-2D platelet This sample comprises 8 sequences of 10 ML (2.83 nm)Zn0.9Mn0.1Se cladding layer and 0.3 ML (0.09 nm) CdSe sheet, a further 10 ML of Zn0.9Mn0.1Se, and a 50 nm ZnSe capping layer.

Simulation and Quantification of High-Resolution Z-Contrast Imaging of Semiconductor Interfaces

1989 ◽  
Vol 159 ◽  
Author(s):  
D. E. Jesson ◽  
S. J. Pennycook ◽  
M. F. Chisholm
Keyword(s):  
High Resolution ◽  
Cross Section ◽  
Image Interpretation ◽  
Bloch Wave ◽  
Small Computer ◽  
High Angle ◽  
Contrast Imaging ◽  
Resolution Function ◽  
Semiconductor Interfaces ◽  
Z Contrast

ABSTRACTIncoherent characteristics of Z-contrast STEM images are explained using a Bloch wave approach. To a good approximation, the image is given by the columnar high-angle cross-section multiplied by the s-state intensity at the projected atom sites, convoluted with an appropriate resolution function. Consequently, image interpretation can be performed intuitively and quantitative simulation can be implemented on a small computer. The feasibility of ‘column-by-column’ compositional mapping is discussed.

Atomic-Resolution Z-Contrast Imaging and its Application to Compositional Ordering and Segregation

1999 ◽  
Vol 583 ◽  
Author(s):  
S. J. Pennycook ◽  
Y. Yan ◽  
A. Norman ◽  
Y. Zhang ◽  
M. Al-Jassim ◽  
...  
Keyword(s):  
High Resolution Electron Microscopy ◽  
Scanning Transmission Electron Microscope ◽  
Ferroelectric Materials ◽  
Atomic Scale ◽  
Atomic Resolution ◽  
High Angle ◽  
Contrast Imaging ◽  
Resolution Electron ◽  
Scanning Transmission ◽  
Z Contrast

AbstractIn the last ten years, the scanning transmission electron microscope (STEM) has become capable of forming electron probes of atomic dimensions making possible a new approach to high-resolution electron microscopy, Z-contrast imaging. Formed by mapping the intensity of high-angle scattered electrons as the probe is scanned across the specimen, the Z-contrast image represents a direct map of the specimen scattering power at atomic resolution. It is an incoherent image, and can be directly interpreted in terms of atomic columns. High angle scattering comes predominantly from the atomic nuclei, so the scattering cross section depends on atomic number (Z) squared. Z-contrast microscopy can therefore be used to study compositional ordering and segregation at the atomic scale. Here we present three examples of ordering: first, ferroelectric materials, second, III-V semiconductor alloys, and finally, cooperative segregation at a semiconductor grain boundary, where a combination of Z-contrast imaging with first principles theory provides a complete atomic-scale view of the sites and configurations of the segregant atoms.

scholarly journals Direct retrieval of crystal structures by maximum-entropy analysis of incoherent Z-contrast images

1994 ◽  
Vol 52 ◽  
pp. 916-917
Author(s):  
A. J. McGibbon ◽  
S. J. Pennycook
Keyword(s):  
Image Processing ◽  
Maximum Entropy ◽  
Crystal Structures ◽  
Electron Probe ◽  
Current Density Distribution ◽  
Incident Electron ◽  
Image Processing Technique ◽  
Bayesian Probability ◽  
Contrast Imaging ◽  
Z Contrast

Z-contrast imaging of crystalline specimens in a scanning transmission electron microscope (STEM) can provide directly interpretable images of crystal structures at atomic resolution with strong compositional sensitivity. The key feature of the technique is that, by recording images using high-anglethermally diffuse scattered electrons, the resultant image is incoherent, and can be interpreted as aconvolution between the incident electron probe and the projected crystal structure of the specimen. Consequently, the technique is ideally suited to the application of deconvolution routines which enable the retrieval of the original crystal lattice by means of an incident electron probe approximation, and with no prior assumption of the nature of the crystal itself. Here, we show that by applying the image processing technique of maximum entropy, such a retrieval can be achieved with high accuracy,enhancing spatial resolution whilst preserving Z-sensitivity.Maximum entropy is an image processing routine based on Bayesian probability which produces a ‘most likely’ reconstruction of the original image given a particular point spread function, or in this case, electron probe current density distribution.

Atomic resolution determination of the structure and chemistry of ceramic grain boundaries

1995 ◽  
Vol 53 ◽  
pp. 320-321
Author(s):  
N. D. Browning ◽  
M. M. McGibbon ◽  
M. F. Chisholm ◽  
S. J. Pennycook
Keyword(s):  
Grain Boundaries ◽  
Scanning Transmission Electron Microscope ◽  
Atomic Scale ◽  
Secondary Phases ◽  
Contrast Imaging ◽  
Scanning Transmission ◽  
Recent Developments ◽  
Contrast Technique ◽  
Z Contrast

Characterization of grain boundaries in ceramics is complicated by the multicomponent nature of the materials, the presence of secondary phases, and the tendency for the grain boundary plane to “wander” on the length scale of a few nanometers. However, recent developments in the scanning transmission electron microscope (STEM) have now made it possible to correlate directly the structure, composition and bonding at grain boundaries on the atomic scale. This direct experimental characterization of grain boundaries is achieved through the combination of Z-contrast imaging (structure) and electron energy loss spectroscopy (EELS) (composition and bonding). For crystalline materials in zone-axis orientations, where the atomic spacing is larger than the probe size, the Z-contrast technique provides a direct image of the metal (high Z) columns. This image, being formed from only the high-angle scattering, can be used to position the electron probe with atomic precision for simultaneous EELS. Under certain collection conditions, the spectrum can have the same atomic spatial resolution as the image, thus permitting the spectra to be correlated with a known atomic location.

Planning of Energy-Selective Neutron Imaging Instrument at CSNS and its Application Prospect in Materials Science

2016 ◽  
Vol 850 ◽  
pp. 161-166 ◽  
Author(s):  
Jie Chen ◽  
Lun Hua He ◽  
Jun Rong Zhang ◽  
Fang Wei Wang
Keyword(s):  
Neutron Source ◽  
Spatial Resolution ◽  
Materials Science ◽  
Neutron Radiography ◽  
Ccd Camera ◽  
Neutron Imaging ◽  
Crystallographic Structure ◽  
Neutron Guide ◽  
Contrast Imaging ◽  
Imaging Instrument

In order to serve a growing multidisciplinary community beyond the traditional scattering areas, an energy-selective neutron imaging instrument is proposed in the China Spallation Neutron Source (CSNS). The instrument is planned to provide analytical techniques such as state-of-the-art energy-selective neutron imaging, neutron radiography, tomography, polarized neutron imaging, neutron phase contrast imaging, and combined neutron diffraction. Coupled hydrogen moderator (CHM) will be chosen as its neutron source. A flight path of 40 m from moderator to sample will provide good energy resolution better than ~0.4%. Super mirror neutron guide will be used to transport neutron from moderator to aperture selector. Aperture selector with 5 apertures and a set of slits will be used to adjust the neutron beam for different modalities. The best spatial resolution will be 50 μm. Different types of detectors will be needed including high spatial resolution CCD camera, TOF detector, and scintillator detector. With a main emphasis on advanced materials and engineering studies, the instrument will enable 2D/3D mapping of the microstructure, chemical composition, and crystallographic structure (grain size, stress and strain, phase position, texture, and so on). It will also support a broad range of studies in archaeology, biology, biomedicine, geosciences, building technology, manufacturing processes, forensic, and homeland security applications.

Sign in / Sign up

Export Citation Format

Share Document