Parallel Detection of Electron Energy Loss Spectra in Direct Mode

1990 ◽  
Vol 48 (2) ◽  
pp. 82-83
Author(s):  
Eckhard Quandt ◽  
Stephan laBarré ◽  
Andreas Hartmann ◽  
Heinz Niedrig
Keyword(s):  
Energy Loss ◽  
Electron Energy ◽  
Energy Resolution ◽  
Large Angle ◽  
Maximum Energy ◽  
Semiconductor Detectors ◽  
Parallel Detection ◽  
Photodiode Arrays ◽  
Electron Energy Loss ◽  
Electron Energy Loss Spectra

Due to the development of semiconductor detectors with high spatial resolution -- e.g. charge coupled devices (CCDs) or photodiode arrays (PDAs) -- the parallel detection of electron energy loss spectra (EELS) has become an important alternative to serial registration. Using parallel detection for recording of energy spectroscopic large angle convergent beam patterns (LACBPs) special selected scattering vectors and small detection apertures lead to very low intensities. Therefore the very sensitive direct irradiation of a cooled linear PDA instead of the common combination of scintillator, fibre optic, and semiconductor has been investigated. In order to obtain a sufficient energy resolution the spectra are optionally magnified by a quadrupole-lens system.The detector used is a Hamamatsu S2304-512Q linear PDA with 512 diodes and removed quartz-glas window. The sensor size is 13 μm ∗ 2.5 mm with an element spacing of 25 μm. Along with the dispersion of 3.5 μm/eV at 40 keV the maximum energy resolution is limited to about 7 eV, so that a magnification system should be attached for experiments requiring a better resolution.

Fine structure of inner shell electron energy loss edges of manganese oxides

1989 ◽  
Vol 47 ◽  
pp. 392-393
Author(s):  
James H. Paterson ◽  
Ondrej L. Krivanek ◽  
Helmut R. Poppa
Keyword(s):  
Fine Structure ◽  
Energy Loss ◽  
Electron Energy ◽  
Energy Resolution ◽  
Manganese Oxides ◽  
Scanning Transmission Electron Microscope ◽  
Parallel Detection ◽  
Scanning Transmission ◽  
And Performance ◽  
Electron Energy Loss

Rask et al. showed that electron energy loss spectroscopy (EELS) may be used to identify oxidation states of polyvalent cations. For the case of manganese, differences in oxidation state are reflected in the shape and position of the edges in the EELS spectrum due to inelastic scattering of incident electrons by the inner shells of manganese and oxygen. We have used a scanning transmission electron microscope (STEM) with a cold field emission gun (FEG) and a parallel-detection EELS system to re-investigate the variations in energy loss fine structure of EELS spectra of various manganese oxides with a significantly improved energy resolution.Spectra were recorded at 100 kV using a VG HB501 STEM with post-specimen lenses, and a Galan Model 666 parallel-detection electron energy loss spectrometer. The operation and performance of this system are discussed elsewhere in these proceedings. For the inner shell edges, the energy dispersion produced by the spectrometer was set to give 0.05 eV per channel. so that a complete spectrum of 1024 channels sampled a range of energy loss of 50 eV. The energy resolution, of the order of 0.4 eV, was therefore not limited by the spatial resolution of the photodiode array in the spectrometer. The oxygen K and manganese L2,3 edges were recorded separately.

ELNES of Iron Compounds

1990 ◽  
Vol 48 (2) ◽  
pp. 28-29
Author(s):  
Hiroki Kurata ◽  
Kazuhiro Nagai ◽  
Seiji Isoda ◽  
Takashi Kobayashi
Keyword(s):  
Energy Loss ◽  
Metal Ions ◽  
Energy Resolution ◽  
Transition Metal Oxides ◽  
Local Symmetry ◽  
Iron Compounds ◽  
Fine Structures ◽  
Electron Energy Loss ◽  
Fe Ions ◽  
Electron Energy Loss Spectra

Electron energy loss spectra of transition metal oxides, which show various fine structures in inner shell edges, have been extensively studied. These structures and their positions are related to the oxidation state of metal ions. In this sence an influence of anions coordinated with the metal ions is very interesting. In the present work, we have investigated the energy loss near-edge structures (ELNES) of some iron compounds, i.e. oxides, chlorides, fluorides and potassium cyanides. In these compounds, Fe ions (Fe2+ or Fe3+) are octahedrally surrounded by six ligand anions and this means that the local symmetry around each iron is almost isotropic.EELS spectra were obtained using a JEM-2000FX with a Gatan Model-666 PEELS. The energy resolution was about leV which was mainly due to the energy spread of LaB6 -filament. The threshole energies of each edges were measured using a voltage scan module which was calibrated by setting the Ni L3 peak in NiO to an energy value of 853 eV.

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