Improved Measurement and Analysis of Series of Valence Electron Energy Loss Spectra and The Local Electronic Structure

1997 ◽  
Vol 3 (S2) ◽  
pp. 943-944
Author(s):  
H. Müllejans ◽  
R. H. French ◽  
G. Duscher ◽  
M. Rühle
Keyword(s):  
Electronic Structure ◽  
Energy Loss ◽  
Electron Energy ◽  
Valence Electron ◽  
Primary Electron ◽  
Full Data ◽  
Data Set ◽  
Automatic Data ◽  
Local Electronic Structure ◽  
Electron Energy Loss

The local electronic structure of ceramic materials can be determined from valence electron energy loss (Veel) spectra via the dielectric function. The quality of the data is comparable to vacuum ultraviolet spectroscopy with the added benefit of high spatial resolution. We have built and implemented a system for spectrum imaging which not only allows automatic data acquisition but also analysis of the full data set. The system consists of a Gatan PEELS and a Gatan Digiscan fitted to a VG HB501 UX STEM and home-built hardware additions. The hardware extensions allow to acquire 1, 2, 3, 4 or 8 spectra for each pixel and in the case of 2 spectra/pixel to vary the exposure time of the specimen to the primary electron beam by controlling the beam blanker (Fig. 1). The first spectrum (2 to 20 ms) contains an unsaturated zero loss peak and the second spectrum (0.05 to 100 s) at the same position the plasmon peak near to but below saturation (Fig. 2).

Local Electronic Structure Of Defects In Gan From Spatially Resolved Electron Energy-Loss Spectroscopy

1997 ◽  
Vol 482 ◽  
Author(s):  
M. K. H. Natusch ◽  
G. A. Botton ◽  
R. F. Broom ◽  
P. D. Brown ◽  
D. M. Tricker ◽  
...  
Keyword(s):  
Optical Properties ◽  
Electronic Structure ◽  
Energy Loss ◽  
Electron Energy ◽  
Electron Energy Loss Spectroscopy ◽  
Crystal Defects ◽  
Vacuum Field ◽  
Spatially Resolved ◽  
Local Electronic Structure ◽  
Electron Energy Loss

AbstractThe optical properties and their modification by crystal defects of wurtzite GaN are investigated using spatially resolved electron energy-loss spectroscopy (EELS) in a dedicated ultra-high vacuum field emission gun scanning transmission electron microscope. The calculated density of states of the bulk crystal reproduces well the features of the measured spectra. The profound effect of a prismatic stacking fault on the local electronic structure is shown by the spatial variation of the optical properties derived from low-loss spectra. It is found that a defect state at the fault appears to bind 1.5 electrons per atom.

Insights into the Electronic Structure of Ceramics through Quantitative Analysis of Valence Electron Energy-loss Spectroscopy

2000 ◽  
Vol 6 (4) ◽  
pp. 297-306 ◽  
Author(s):  
Harald Müllejans ◽  
Roger H. French
Keyword(s):  
Electronic Structure ◽  
Quantitative Analysis ◽  
Energy Loss ◽  
Electron Energy ◽  
Valence Electron ◽  
Interband Transition ◽  
Ceramic Materials ◽  
Scanning Transmission Electron Microscope ◽  
Transition Strength ◽  
Electron Energy Loss

AbstractValence electron energy-loss (VEEL) spectroscopy was performed on six ceramic materials in a dedicated scanning transmission electron microscope (STEM). Quantitative analysis of these data is described yielding access to the complex optical properties and the electronic structure of the materials. Comparisons are made on the basis of the interband transition strength describing transitions between occupied states in the valence band and empty states in the conduction band. This proves that the quantitative analysis of VEEL data is a competitive and complementary method to be considered when investigating the electronic structure of materials. Possibilities for improvement and extension of the analysis are discussed extensively.

Quantitative analysis of spatially resolved valence electron energy-loss spectra for electronic structure studies of grain boundaries and thin intergranular films

1995 ◽  
Vol 53 ◽  
pp. 314-315
Author(s):  
Roger H. French
Keyword(s):  
Electronic Structure ◽  
Quantitative Analysis ◽  
Spectral Line ◽  
Energy Loss ◽  
Grain Boundaries ◽  
Electron Energy ◽  
Valence Electron ◽  
Transition Strength ◽  
Spatially Resolved ◽  
Electron Energy Loss

The spatial variation of the electronic structure at interfaces is critical to both interatomic bonding at atomically abrupt interfaces such as grain boundaries and also to the development of van der Waals (vdW) attraction forces at partially wetted interfaces. This interfacial electronic structure, as represented by the interband transition strength , can be determined by Kramers Kronig (KK) analysis of either vacuum ultraviolet (VUV) optical reflectance spectra or spatially resolved valence electron energy loss (SR-VEEL) spectra. Quantitative analysis of SR-VEELS requires accurate spectral line shapes coupled with single scattering deconvolution, convergence correction, and KK analysis. Both the energy loss functions (Fig. 1) and the interband transitions (Fig. 2) determined for α-Al2O3 using SR-VEELS compare well with the VUV results. In addition the use of the spectral line scan method, whereby typically 200 SR-VEEL spectra are acquired along a scan line of 20 nm, helps overcome many uncertainties in the data acquisition and analysis.

Insights into the Electronic Structure of Ceramics through Quantitative Analysis of Valence Electron Energy-loss Spectroscopy

2000 ◽  
Vol 6 (4) ◽  
pp. 297-306 ◽  
Author(s):  
Harald Müllejans ◽  
Roger H. French
Keyword(s):  
Electronic Structure ◽  
Quantitative Analysis ◽  
Energy Loss ◽  
Electron Energy ◽  
Valence Electron ◽  
Interband Transition ◽  
Ceramic Materials ◽  
Scanning Transmission Electron Microscope ◽  
Transition Strength ◽  
Electron Energy Loss

Abstract Valence electron energy-loss (VEEL) spectroscopy was performed on six ceramic materials in a dedicated scanning transmission electron microscope (STEM). Quantitative analysis of these data is described yielding access to the complex optical properties and the electronic structure of the materials. Comparisons are made on the basis of the interband transition strength describing transitions between occupied states in the valence band and empty states in the conduction band. This proves that the quantitative analysis of VEEL data is a competitive and complementary method to be considered when investigating the electronic structure of materials. Possibilities for improvement and extension of the analysis are discussed extensively.

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