Das Aufl�sungsverm�gen des elektrostatisch-magnetischen Energieanalysators f�r schnelle Elektronen

Abstract

The electrostatic magnetic energy analyzer 1 consists of a Wien filter (crossed electric and magnetic fields) between two immersion lenses. The energetic resolution of the analyzer is calculated. The intensity problem in connection with the generation of a monoenergetic electron beam is discussed considering anomalous energy spread in high density beams. With an arrangement containing two analyzers of the same kind the resolving power is experimentally determined to 0.017 ev.

Limits to the spatial, energy and momentum resolution of electron energy-loss spectroscopy

“…The highest energy resolutions (in the range 2-100 meV) have been obtained by combining these relative monochromators with relative spectrometer systems; the same high voltage is used to retard the electrons when they are analyzed, so that high-voltage fluctuations are compensated [59][60][61][62]. Such an arrangement has the disadvantage of requiring high potential to be applied to the postspecimen portion of the TEM column.…”

Developments in EELS instrumentation for spectroscopy and imaging

“…If the same high tension (HT) supply is used for the electron gun as well as for all the deaccelerators and accelerators in such an instrument, fluctuations of the HT of several volts have no effect on the resolution, which is instead determined by the stability of the auxiliary power supply which controls the much smaller potential difference between the primary voltage and the deaccelerating voltage applied to the two filters. An instrument of this type was developed by Boersch, Geiger and coworkers, who succeeded in obtaining energy resolution better than 3 meV already some time ago [12,36] at 30 kV primary voltage. Their approach is now being applied at 80 kV primary voltage [13].…”

“…Energy-filtered imaging, which was originally developed by Castaing and Henry [7], has also lead to a commercially available instrument, and is now being used for imaging with improved contrast as well as for chemical mapping of major constituents [8]. There is also much interest in improving the attainable energy resolution, both by optimizing the performance of spectrometers attached to microscopes using cold field emission guns with a narrow energy spread [9][10][11], and by decreasing the energy spread of the gun further through the use of a monochromator [12,13].…”

Instrumentation

“…In high-energy electron trans-mission spectroscopy, a Wien filter (crossed electric and magnetic fields) was also used successfully, and in fact the best resolution reported so far (Δ£ =1.8 meV) was obtained with a Wien filter spectrometer [2]. Low-energy electron spectrometers generally employ energy dispersive systems of the electrostatic deflector type.…”