Surface extended energy-loss fine structure spectroscopy: extraction of structural information from spectra recorded in the second derivative mode of the electron yield

1991 ◽  
Vol 3 (30) ◽  
pp. 5693-5709
Author(s):  
J Lopez ◽  
J Rousseau ◽  
J C Le Bosse ◽  
M Rjeb
Keyword(s):  
Fine Structure ◽  
Energy Loss ◽  
Structural Information ◽  
Second Derivative ◽  
Electron Yield

Spatially Resolved Local Atomic Structure from Exelfs

1994 ◽  
Vol 332 ◽  
Author(s):  
E. A. Stern ◽  
M. Qian ◽  
M. Sarikaya
Keyword(s):  
Fine Structure ◽  
Energy Loss ◽  
Structural Information ◽  
Spectroscopic Techniques ◽  
Complex Materials ◽  
Spatially Resolved ◽  
Transmission Electron ◽  
Electron Energy Loss ◽  
X Ray Absorption ◽  
Potential Use

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.

Elfs: Energy Loss Fine Structure Analysis in Materials

1997 ◽  
Vol 3 (S2) ◽  
pp. 953-954
Author(s):  
Mehmet Sarikaya ◽  
Maoxu Qian ◽  
Edward A. Stern
Keyword(s):  
Fine Structure ◽  
Data Analysis ◽  
Energy Loss ◽  
Amorphous Materials ◽  
Structural Information ◽  
New Developments ◽  
Spectral Statistics ◽  
Modeling Theory ◽  
X Ray Absorption ◽  
Acquisition Technique

ELFS (energy loss fine structure), similar to XAFS (x-ray absorption fine structure) provides short-range order atomic structural information of crystalline and amorphous materials. Although known quite sometime, ELFS spectroscopy only until recently has gained importance, mainly due new developments in spectrometer and TEM designs, spectra acquisition and interpretation techniques. This paper focuses on some new developments in the acquisition, interpretation, and the use of the extended regime of the ELFS spectroscopy.Although fine structure spectroscopy in EELS and its similarity to XAFS were recognized sometime ago, ELFS has only seen limited use mainly because of insufficient spectral statistics, various systematic errors and drifts, and the absence of sophisticated software that faithfully uses the XAFS software and incorporates the latest advances in modeling theory. We have systematically improved the data acquisition technique and developed ELFS data analysis procedure which utilizes the sophisticated UWXAFS data analysis software package8 after correction of the differences between ELFS and XAFS data.

OBTAINING COORDINATION NUMBERS FROM EELFS SPECTRA

1997 ◽  
Vol 04 (05) ◽  
pp. 951-954 ◽  
Author(s):  
D. V. SURNIN ◽  
D. E. DENISOV ◽  
YU. V. RUTS
Keyword(s):  
Fine Structure ◽  
Energy Loss ◽  
Electron Energy ◽  
Structural Information ◽  
Quantitative Information ◽  
Distribution Functions ◽  
Radial Distribution Functions ◽  
Regularization Algorithm ◽  
Coordination Numbers ◽  
Electron Energy Loss

The electron energy loss fine structure (EELFS) method allows one to obtain information on atomic bond lengths from the surface to the bulk. But gaining more complete quantitative information for example on coordination numbers has not presently been realized. The possibility of obtaining normalized radial distribution functions (RDF's) is shown for EELFS spectra which may be used for deriving complete structural information on pure elements. RDF's were obtained by using the regularization algorithm (after A. N. Tikhonov). The method for obtaining the RDF's was applied to the experimental Fe M 2,3 EELFS spectrum.

Monte Carlo Modelling of Secondary Electron Yield from Rough Surfaces

1990 ◽  
Vol 48 (1) ◽  
pp. 422-423
Author(s):  
John C. Russ
Keyword(s):  
Monte Carlo ◽  
Energy Loss ◽  
Secondary Electron ◽  
Secondary Electron Emission ◽  
Analytical Calculation ◽  
Mean Free Path ◽  
Single Scattering ◽  
High Energy ◽  
Secondary Electron Yield ◽  
Electron Yield

Monte-Carlo programs are well recognized for their ability to model electron beam interactions with samples, and to incorporate boundary conditions such as compositional or surface variations which are difficult to handle analytically. This success has been especially powerful for modelling X-ray emission and the backscattering of high energy electrons. Secondary electron emission has proven to be somewhat more difficult, since the diffusion of the generated secondaries to the surface is strongly geometry dependent, and requires analytical calculations as well as material parameters. Modelling of secondary electron yield within a Monte-Carlo framework has been done using multiple scattering programs, but is not readily adapted to the moderately complex geometries associated with samples such as microelectronic devices, etc.This paper reports results using a different approach in which simplifying assumptions are made to permit direct and easy estimation of the secondary electron signal from samples of arbitrary complexity. The single-scattering program which performs the basic Monte-Carlo simulation (and is also used for backscattered electron and EBIC simulation) allows multiple regions to be defined within the sample, each with boundaries formed by a polygon of any number of sides. Each region may be given any elemental composition in atomic percent. In addition to the regions comprising the primary structure of the sample, a series of thin regions are defined along the surface(s) in which the total energy loss of the primary electrons is summed. This energy loss is assumed to be proportional to the generated secondary electron signal which would be emitted from the sample. The only adjustable variable is the thickness of the region, which plays the same role as the mean free path of the secondary electrons in an analytical calculation. This is treated as an empirical factor, similar in many respects to the λ and ε parameters in the Joy model.

Some Aspects of Exelfs Analysis in the Electron Microscope

1980 ◽  
Vol 38 ◽  
pp. 118-119
Author(s):  
D. E. Johnson ◽  
S. Csillag
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Energy Loss ◽  
Analytical Electron Microscopy ◽  
Interference Effects ◽  
Interatomic Distances ◽  
X Ray ◽  
Structure Information ◽  
Microanalytical Technique ◽  
Analytical Electron

Recently, the applications area of analytical electron microscopy has been extended to include the study of Extended Energy Loss Fine Structure (EXELFS). Modulations past an ionization edge in the energy loss spectrum (EXELFS), contain atomic fine structure information similar to Extended X-ray Absorbtion Fine Structure (EXAFS). At low momentum transfer the main contribution to these modulations comes from interference effects between the outgoing excited inner shell electron waves and electron waves backscattered from the surrounding atoms. The ability to obtain atomic fine structure information (such as interatomic distances) combined with the spatial resolution of an electron microscope is unique and makes EXELFS an important microanalytical technique.

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