scholarly journals Characterization of Newly Synthesized Novel Graphite Films

1988 ◽  
Vol 121 ◽  
Author(s):  
Kannan M. Krishnan ◽  
John Kouvetakis ◽  
Takayoshi Sasaki ◽  
Neil Bartlett
Keyword(s):  
Cross Sections ◽  
Core Loss ◽  
Careful Study ◽  
New Materials ◽  
Carbon And Nitrogen ◽  
Resonance Energies ◽  
Fine Structures ◽  
Electron Energy Loss ◽  
Boron Carbon

ABSTRACTReactions of C5H6 and BCl3 at 800°C yields a metallic graphite-like material of composition BCx (3.0 ≤ x ≤ 4.00) while reactions of BCl3, NH3 and C2 produces a B/C/N graphitic semiconductor of approximate stoichiometry B2CN2. Both materials were shown to be homogeneous using Auger electron spectroscopy and extensively characterized by electron energy-loss spectroscopy. Single loss profiles of the EELS data were obtained using the fourier-log deconvolution method. Compositions were determined using hydrogenic cross-sections. A careful study of the plasmon resonance energies and the fine structures of the core-loss edges of these materials has been invaluable in demonstrating that the boron, carbon and nitrogen atoms are all sp2 hybridized. Therefore, these new materials are in-sheet graphite hybrids and not intercalations.

Oxygen K near edge structures studied with multiple scattering calculations

1988 ◽  
Vol 46 ◽  
pp. 504-505
Author(s):  
Xudong Weng ◽  
Peter Rez
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Partial Cross Section ◽  
Energy Window ◽  
Edge Structure ◽  
Fine Structures ◽  
Hydrogenic Model ◽  
Electron Energy Loss ◽  
Quantitative Chemical

In electron energy loss spectroscopy, quantitative chemical microanalysis is performed by comparison of the intensity under a specific inner shell edge with the corresponding partial cross section. There are two commonly used models for calculations of atomic partial cross sections, the hydrogenic model and the Hartree-Slater model. Partial cross sections could also be measured from standards of known compositions. These partial cross sections are complicated by variations in the edge shapes, such as the near edge structure (ELNES) and extended fine structures (ELEXFS). The role of these solid state effects in the partial cross sections, and the transferability of the partial cross sections from material to material, has yet to be fully explored. In this work, we consider the oxygen K edge in several oxides as oxygen is present in many materials. Since the energy window of interest is in the range of 20-100 eV, we limit ourselves to the near edge structures.

Terra Incognita: Spectra from Edges and Elements not in the EELS Atlas

1998 ◽  
Vol 4 (S2) ◽  
pp. 532-533
Author(s):  
J. A. Former ◽  
E. C. Buck
Keyword(s):  
Cross Sections ◽  
Fuel Cycle ◽  
Core Loss ◽  
High Energy ◽  
Spectral Lines ◽  
Road Map ◽  
Terra Incognita ◽  
Ccd Array ◽  
Array Detection ◽  
Electron Energy Loss

The EELS Core-Loss Atlas, like a road map, serves as an essential guide for practitioners of electron energy loss spectroscopy (EELS). Even the best maps will be incomplete, however, and one may need to plot a course by other means. Our work with materials from the nuclear fuel cycle has required new spectral lines, and even new elements, to be charted. The actinides and technetium, for instance, have important spectral features above 2 keV. The EELS technique has not often been used for detecting lines above about 2 keV because of the rapidly diminishing differential cross sections for these higher energy transitions. However, as instrumentation has progressed from scanning to parallel to CCD-array detection, statistical limitations on the high energy data have been improved by orders of magnitude. Also, in some cases, the notion of higher energy lines as “weak” is excessively pessimistic.

Background modeling alternatives in EELS and their implications on microanalysis

1988 ◽  
Vol 46 ◽  
pp. 538-539
Author(s):  
Kannan M. Krishnan ◽  
M. T. Stampfer
Keyword(s):  
Cross Sections ◽  
Core Loss ◽  
Energy Window ◽  
Ionization Cross ◽  
Inverse Power Law ◽  
Power Law Function ◽  
Edge Based ◽  
Electron Energy Loss ◽  
Source Of Error ◽  
Ionization Edge

With the advent of parallel detectors, electron energy-loss spectroscopy (EELS) is expected to be employed increasingly in the routine microanalysis of light elements. The quantitation formulae that are used are relatively simple and straightforward and require only a measurement of the integrated core-loss intensity over a particular energy window beyond the ionization edge (Δi) and most often, a calculated ionization cross-section. Even though the hydrogenic cross-sections that are used routinely for microanalysis can be a source of error, it is observed that the procedure that largely determines the accuracy of quantification is the removal of the contribution of the background below the ionization edge. Based on empirical observations, an inverse power law function of the form I = AE-r, where the exponent ‘r’ takes values from 2 to 6, is now commonly used for the background. A background fitting region preceding the ionization edge (Δb) is chosen, the constants A and r determined by least squares refinement and the background extrapolated beyond the ionization edge for the required energy window (Δi).

Characterization of Some 3d Transition Metal Oxides through Core Loss Electron Energy Loss Spectroscopy

1980 ◽  
Vol 38 ◽  
pp. 122-123
Author(s):  
L. A. Grunes
Keyword(s):  
Energy Loss ◽  
Electron Energy ◽  
Electron Energy Loss Spectroscopy ◽  
Transition Metal Oxides ◽  
Core Loss ◽  
The Core ◽  
Medium Resolution ◽  
Core Losses ◽  
Electron Energy Loss

Electron Energy Loss Spectroscopy (EELS) is a useful technique for chemical microanalysis in the electron microscope. In particular, medium resolution (˜leV) measurements of core losses involving ionization of the tightly bound inner shell electrons reveal fine structure which identify both the core atom and the neighboring chemical environment. The transition metals of the third period possess narrow partly filled d-bands which give rise to striking magnetic and electronic properties of technological importance.

A simple parameterization scheme for inner-shell cross sections

1988 ◽  
Vol 46 ◽  
pp. 532-533
Author(s):  
R.F. Egerton
Keyword(s):  
Solid State ◽  
Energy Loss ◽  
Cross Section ◽  
Cross Sections ◽  
Elemental Analysis ◽  
Incident Energy ◽  
Core Loss ◽  
Dipole Oscillator ◽  
Electron Energy Loss ◽  
Hand Calculator

Quantitative elemental analysis by electron energy-loss spectroscopy requires values of core-loss cross section σ(β,Δ) integrated up to a scattering angle β and over an energy range Δ above the ionization threshold. Such cross sections can be calculated using atomic models [1-3], neglecting solid-state effects. They can also be determined experimentally [4,5], but only for particular values of β,Δ and incident energy E0. By representing σ(β,Δ) in terms of an integrated dipole oscillator strength f(Δ) which is independent of β and E0, we realize two advantages: (1) measurements on solids can be directly compared with one another and with theory, and (2) values of σ(β,Δ) for K, L and M edges can be derived from tabulated values of f(Δ) by use of a hand calculator or a very short computer program.

Extending the limits of molecular microanalysis

1994 ◽  
Vol 52 ◽  
pp. 946-947
Author(s):  
J. H. Blackson ◽  
D. W. Susnitzky ◽  
D. R. Beaman
Keyword(s):  
Core Loss ◽  
Electron Dose ◽  
Edge Structure ◽  
Thin Sections ◽  
Selective Staining ◽  
Present Procedure ◽  
Staining Methods ◽  
Electron Energy Loss ◽  
Contrast Image

Modern polymer blends are frequently composed of domains and interfacial phases having submicron dimensions. Previously, die characterization of specific unknown submicron polymer phases has been limited to selective staining methods that help to classify the phase but rarely lead to chemical identification. The present procedure uses parallel detection electron energy loss spectroscopy (PEELS) to perform submicron molecular microanalysis on beam sensitive materials. Polymer domains are first differentiated by their elemental composition and then by their characteristic carbon core loss edge structure. These spectra are compared to spectra recorded from polymers of known composition.A polymer film composed of alternating 0.5 μm layers of polycarbonate (PC) and polymethylmethacrylate (PMMA) was used as a test specimen (Fig. 1). Ultra-thin sections (<50 nm) were prepared by microtomy, collected on unsupported 600 mesh copper grids and examined at −160°C usinga VG HB601UX dedicated STEM fitted with a Gatan 666 UHV PEELS. The combination of beam blanking, simplecontrol of electron dose, UHV, low energy spread FEG, stage stability and the ability to produce a high contrast image at a very low electron dose makes this instrument ideally suited for this experiment.

Characterization of Reactively Sputtered Titanium Carbide Films by Analytical Electron Microscopy

1985 ◽  
Vol 62 ◽  
Author(s):  
J. Tafto ◽  
G. Rajeswaran ◽  
T. Saulys
Keyword(s):  
Electron Microscopy ◽  
Core Loss ◽  
Analytical Electron Microscopy ◽  
Face Centered Cubic ◽  
Transmission Electron ◽  
Partial Pressures ◽  
The Face ◽  
Face Centered ◽  
Electron Energy Loss

ABSTRACTTICx films prepared by reactive sputtering using a Ti target and different methane partial pressures were characterized by analytical transmission electron microscopy. The films are polycrystalline, and the plasmon energy increases considerably with increasing carbon content. Combination of the information obtained from electron energy loss plasmon and core loss spectra, and electron diffraction indicates that x in TiCx increases linearly with methane partial pressure. We find that the face centered cubic TIC phase spans the composition from TiC0.2 to TiC1.0 and when x<l we have a mixture of TiC1.0 and amorphous C.

scholarly journals Contribution of core-loss fine structures to the characterization of ion irradiation damages in the nanolaminated ceramic Ti3AlC2

2013 ◽  
Vol 61 (19) ◽  
pp. 7348-7363 ◽  
Author(s):  
M. Bugnet ◽  
V. Mauchamp ◽  
P. Eklund ◽  
M. Jaouen ◽  
T. Cabioc’h
Keyword(s):  
Ion Irradiation ◽  
Core Loss ◽  
Fine Structures

Characterization of Ga-Mn Decagonal Quasicrystals in GaAs

2000 ◽  
Vol 643 ◽  
Author(s):  
K. Sun ◽  
N. D. Browning
Keyword(s):  
Magnetic Moments ◽  
Core Loss ◽  
Contrast Imaging ◽  
Low Loss ◽  
Plasmon Peak ◽  
Decagonal Quasicrystals ◽  
Icosahedral Quasicrystals ◽  
Z Contrast ◽  
Electron Energy Loss

AbstractGa-Mn decagonal quasicrystals (DQC), as well as a Ga-Mn approximant and a normal crystal in GaAs are investigated by electron energy-loss spectroscopy (EELS) and energy dispersive X- ray spectroscopy (EDS) combined with Z-contrast imaging. Plasmon peak positions (Ep), full- width-half-maxima (FWHM) and Mn L3/L2ratios of these three phases are derived from their low-loss spectra and core-loss spectra respectively. Mn, Ga and As distributions in ion implanted GaAs layers are characterized by EDS at line-scan mode. These results show that the Ga-Mn DQC has higher Ep and FWHMs than those of its normal crystal counterpart, as well as all other reported QCs. The much larger L3/L2 intensity ratio of the Ga-Mn DQC over that of the Al-Mn icosahedral quasicrystals (IQC) may suggest Mn atoms in the Ga-Mn DQC have much larger local magnetic moments.

SIGMAL: A Program for Calculating L-Shell lonization Cross-Sections

1981 ◽  
Vol 39 ◽  
pp. 198-199 ◽  
Author(s):  
R.F. Egerton
Keyword(s):  
Cross Sections ◽  
Fortran Program ◽  
Absorption Data ◽  
X Ray ◽  
Atomic Electrons ◽  
Energy Dependent ◽  
Hydrogenic Model ◽  
Electron Energy Loss ◽  
X Ray Absorption ◽  
Shell Ionization

SIGMAL is a short (∼ 100-line) Fortran program designed to rapidly compute cross-sections for L-shell ionization, particularly the partial crosssections required in quantitative electron energy-loss microanalysis. The program is based on a hydrogenic model, the L1 and L23 subshells being represented by scaled Coulombic wave functions, which allows the generalized oscillator strength (GOS) to be expressed analytically. In this basic form, the model predicts too large a cross-section at energies near to the ionization edge (see Fig. 1), due mainly to the fact that the screening effect of the atomic electrons is assumed constant over the L-shell region. This can be remedied by applying an energy-dependent correction to the GOS or to the effective nuclear charge, resulting in much closer agreement with experimental X-ray absorption data and with more sophisticated calculations (see Fig. 1 ).

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