Energy filtering

The field of corrected microscopes has just begun with the instruments discussed above. The progress in this field is very rapid and proposals for a sub-Angstrom TEM (SATEM) or even the combination of this instrument with a corrected energy filter to fonn a sub-electronvolt/sub-Angstrom TEM (SESAM) are underway. 

Reimer L 995 Energy-Filtering Transmission Electron Microscopy (BerWn Springer)... 

EFTEM Energy-filtered Transmission Electron Microscopy... 

All the energy-filter systems referred to above are incorporated into the electron-microscopic column, usually between the diffraction lens and the following intermedium lens. They are, therefore, known as in-column filters, which are also commer-... 

Fig. 2.34. Arrangement of post-column and incolumn imaging energy filters [2.173],...

Fig. 2.42. Energy-filtered TEM (three-window method), imaging ofthe Cr distribution in the Ni-base superalloy SCI 6.

Fig. 2.44. Chemical-bond mapping (a) comparison of EEL spectra recorded from matrix and SiC-fibre with the window for energy filtering shown (b) map of oxidic-bound Si.

The basic principle of e-beam SNMS as introduced by Lipinsky et al. in 1985 [3.60] is simple (Fig. 3.30) - as in SIMS, the sample is sputtered with a focused keV ion beam. SN post-ionization is accomplished by use of an e-beam accelerated between a filament and an anode. The applied electron energy Fe a 50 20 eV is higher than the range of first ionization potentials (IP) of the elements (4—24 eV, see Fig. 3.31). Typical probabilities of ionization are in the 0.01% range. SD and residual gas suppression is achieved with electrostatic lenses before SN post-ionization and energy filtering, respectively. 

Positive secondary ions (SI" ) are repelled by an electrode in e-beam SNMS or completely (in DBM) or widely (in HFM, see below) re-attracted by the sample surface in HF-plasma SNMS. Ionized plasma species (Ar", contamination) are suppressed by energy filtering. 

The precise description of geometrical structures of CNTs has been reported by lijima [1], who was the first discoverer of carbon microtubules. Electron diffraction (ED) results are presented in Chap. 3. In this chapter, the authors will focus on the electronic structures of CNTs from the viewpoint of EELS by using TEM equipped with an energy-filter in the column or under the column. 

Fig. 5. Electron ray path of Castaing-Henry energy filter.

Reimer, L., Energy-Filtering Transmission Electron Microscopy, Springer-Verlag, Berlin, Heidelberg, 1995, pp. 1-42 and pp. 347-400. 

Figure 6. Schematic outline of the first commercially available multiple collector ICPMS, the Plasma 54, after Halhday et al. (1995). This instrument uses Nier-Johnson double-focusing and is equipped with eight independently adjustable Faraday collectors. The axial collector can be wound down to provide access to a Daly detector equipped with ion counting capabilities and a second-stage energy filter for high abundance sensitivity measurements. The sample may be introduced to the plasma source by either solution aspiration or laser ablation.

Luo X, Rehkamper M, Lee D-C, Halliday AN (1997) High precision °Th/ Th and " U/ U measurements using energy-filtered ICP magnetic sector mrrltiple collector mass spectrometry. Inti J Mass Spectrom Ion Processes 171 105-117... 

Neder H, Heusser G, Laubenstein M (2000) Low-level y-ray germanium-spectrometer to measure veiy low primordial radionuclide concentrations. ApplRadiat Isot 53 191-195 Palacz ZA, Freedman PA, Walder AJ (1992) Thorium isotope ratio measurements at high abundance sensitivity using a VG 54-30, an energy-filtered thermal ionization mass spectrometer. Chem Geol 101 157-165... 

A mass-energy filter may be included to remove contaminant ions, and multiply charged and clustered ions of the main beam species. Ions of the required mass and energy pass through the filter, while unwanted species are deflected out of the beam. Prior to final focussing, the beam is deflected through a few degrees, and any neutral particles will be undeviated and are therefore separated out. 

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