Spatially Resolved Local Atomic Structure from Exelfs

ABSTRACTEXELFS, extended energy loss fine structure, is one of the spectroscopic techniques provided by electron energy loss spectrometer in the transmission electron microscope. Here, EXELFS is described for its potential use for determining nanoscale physical properties of complex materials. It is demonstrated that EXELFS analysis, like EXAFS, extended X-ray absorption fine structure in bulk materials, provides short-range structural information such as atomic nearest-neighbors and their distances in amorphous an crystalline samples. Some of the problems that hindered the development and wide use of EXELFS were discussed and their solutions are presented. Further solutions and future prospects are discussed.

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Extended x-ray-absorption and electron-energy-loss fine-structure studies of the local atomic structure of amorphous unhydrogenated and hydrogenated silicon carbide

Physical Review B ◽

10.1103/physrevb.38.13099 ◽

1988 ◽

Vol 38 (18) ◽

pp. 13099-13106 ◽

Cited By ~ 43

Author(s):

Alain E. Kaloyeros ◽

Richard B. Rizk ◽

John B. Woodhouse

Keyword(s):

Silicon Carbide ◽

Fine Structure ◽

Energy Loss ◽

Electron Energy ◽

Atomic Structure ◽

Local Atomic Structure ◽

Hydrogenated Silicon ◽

X Ray ◽

Electron Energy Loss ◽

X Ray Absorption

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Analysis of Extended Energy-Loss Fine Structure of Nanometerscale Clusters

Microscopy and Microanalysis ◽

10.1017/s143192760001686x ◽

1999 ◽

Vol 5 (S2) ◽

pp. 708-709

Author(s):

Y. Ito ◽

H. Jain ◽

D.B. Williams

Keyword(s):

Fine Structure ◽

Energy Loss ◽

Atomic Clusters ◽

Nanometer Scale ◽

X Ray ◽

Small Clusters ◽

Electron Energy Loss ◽

X Ray Absorption ◽

Ionization Edge

Small atomic clusters are of great importance for applications such as catalysts whose activity depends on the surface of the cluster. Attempts to determine the atomic short-range order and size of clusters have been made by analyzing the extended X-ray absorption fine structure (EXAFS). However, the analysis was made on an average of many small clusters. Analysis of extended energy-loss fine structure (EXELFS) in an electron energy-loss spectrum (EELS) has developed to the point where in some cases, the quality of the results is comparable to its X-ray analogue, EXAFS. No other technique provides nanometer-scale spatial resolution of the analyzed area for determining the atomic structure. Most EXELFS analysis has been performed on the K-ionization edge of lighter elements. For heavier elements, a more complex ionization edge such as the L-edge has to be used, due to the inefficiency of collecting high quality EEL spectra at higher energy-losses (Z > 18).

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Comparison of the TiK extended fine structure obtained from electron energy loss spectroscopy and x-ray absorption spectroscopy

Ultramicroscopy ◽

10.1016/0304-3991(93)90004-h ◽

1993 ◽

Vol 50 (2) ◽

pp. 141-145 ◽

Cited By ~ 13

Author(s):

G. Blanche ◽

G. Hug ◽

M. Jaouen ◽

A.M. Flank

Keyword(s):

Fine Structure ◽

Energy Loss ◽

Electron Energy ◽

Absorption Spectroscopy ◽

Electron Energy Loss Spectroscopy ◽

X Ray ◽

Electron Energy Loss ◽

X Ray Absorption

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A sub-micrometer resolution hard X-ray microprobe system of BL8C at Pohang Light Source

Journal of Synchrotron Radiation ◽

10.1107/s1600577515014071 ◽

2015 ◽

Vol 22 (5) ◽

pp. 1306-1311 ◽

Cited By ~ 3

Author(s):

Nark-Eon Sung ◽

Ik-Jae Lee ◽

Kug-Seong Lee ◽

Seong-Hun Jeong ◽

Seen-Woong Kang ◽

...

Keyword(s):

Trace Elements ◽

Fine Structure ◽

South Korea ◽

Spatial Resolution ◽

High Spatial Resolution ◽

Structural Information ◽

Complex Materials ◽

X Ray ◽

Pohang Light Source ◽

X Ray Absorption

A microprobe system has been installed on the nanoprobe/XAFS beamline (BL8C) at PLS-II, South Korea. Owing to the reproducible switch of the gap of the in-vacuum undulator (IVU), the intense and brilliant hard X-ray beam of an IVU can be used in X-ray fluorescence (XRF) and X-ray absorption fine-structure (XAFS) experiments. For high-spatial-resolution microprobe experiments a Kirkpatrick–Baez mirror system has been used to focus the millimeter-sized X-ray beam to a micrometer-sized beam. The performance of this system was examined by a combination of micro-XRF imaging and micro-XAFS of a beetle wing. These results indicate that the microprobe system of the BL8C can be used to obtain the distributions of trace elements and chemical and structural information of complex materials.

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Quantitative Measurement of Compositional Enrichment in Strained Alloy Quantum Dots

Microscopy and Microanalysis ◽

10.1017/s1431927600027161 ◽

2001 ◽

Vol 7 (S2) ◽

pp. 218-219

Author(s):

P.A. Crozier ◽

M. Catalano

Keyword(s):

Quantum Dots ◽

Energy Loss ◽

Electron Energy ◽

Vision System ◽

Wetting Layer ◽

Spatially Resolved ◽

Transmission Electron ◽

Scanning Transmission ◽

Alloy Quantum Dots ◽

Electron Energy Loss

High spatial resolution information on the structure and composition of semiconductor quantum dots is necessary to relate microstructure to macroscopic electron-optical properties [1]. Scanning transmission electron microscopy (STEM) combined with electron energy-loss spectroscopy (EELS) can be used to determine the elemental composition of nanometer-sized particles. Applying these techniques to quantum dots is challenging because the dot nucleates on a very thin wetting layer of similar composition and is embedded in a matrix. Here we present a strategy to extract absolute compositional information on InGaAs dots. The method relies on modeling both the dot shape and the electron probe profile.Samples were prepared by depositing four monolayers of In0.5Ga0.5As onto a GaAs substrate giving a nominal wetting layer thickness of 1.2 nm [2]. STEM was performed on a Vacuum Generator's HB501 equipped with a GATAN parallel electron energy-loss spectrometer. An ES Vision system was used to acquire spatially resolved electron energy-loss spectra from the wetting layer and the quantum dots.

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