Radiant energy – Electron energy analysis
Patent
1988-10-20
1990-07-17
Anderson, Bruce C.
Radiant energy
Electron energy analysis
H01J 4944
Patent
active
049422987
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electron spectrometer of the type in which a substance under investigation is bombarded with electrons and the spectra of electrons scattered from the substance are studied. Spectrometers of this type are used to investigate for example the atomic and molecular structure of materials. The substance which is bombarded with electrons is generally referred to as the target.
The basic principles of electron spectrometry are well known and a useful description of these principles is contained in U.S. Pat. No. 3,777,159. In conventional electron spectrometers, a beam of electrons provided by an electron source is initially dispersed in energy. A monochromatic beam (in which all the electrons have the same energy) is selected from the dispersed output of the electron source and the monochromatic beam is used to bombard a target. A beam of scattered electrons results the energies of which vary and this beam of scattered electrons is in turn dispersed in energy and detected by a linear array of detectors. The output of each detector is representative of the number of electrons scattered from the target having an energy corresponding to the position of that detector.
It has been proposed to provide two dimensional electron spectrometers in which the single linear array of detectors provided in one dimensional spectrometers is replaced by a two dimensional array made of a series of arrays of detectors arranged in parallel. In one known electron spectrometer the detectors are in the form of a 100.times.100 photodiode array. In all the known electron spectrometers however, the target is bombarded with a monochromatic beam of electrons so that appropriate conclusions can be drawn from the detected energy of the resultant scattered electrons. The use of a monochromatic beam does however mean that only a small proportion of the output of the electron source is in fact utilized to bombard the target.
SUMMARY OF THE INVENTION
It is an object of the present invention to improve the sensitivity of electron spectrometers.
According to the present invention there is provided an electron spectrometer comprising an electron source for providing a beam of electrons having a predetermined energy spectrum, an electron selector for dispersing in energy the electrons of the beam to produce an elongate selector image each portion of the length of which comprises electrons having a predetermined respective energy, means for focussing the selector image on a target to produce an elongate target image including scattered electrons having a range of energies, each portion of the length of the target image resulting from a respective portion of the length of the selector image, and an analyzer for dispersing in energy the scattered electrons of the target image, the analyzer being orientated such that the electrons are dispersed in a direction substantially perpendicular to the length of the target image, whereby the analyzer produces a rectangular image made up of substantially parallel strips each including electrons of a range of energies but each resulting from the scattering by the target of electrons of a respective energy.
The invention also provides a method for producing a two-dimensional image of a target in an electron spectrometer, wherein a beam of electrons having a range of energies is dispersed in energy to produce an elongate selector image each portion of the length of which comprises electrons having a predetermined respective energy, the selector image is focussed on the target to produce an elongate target image including scattered electrons having a range of energies, each portion of the length of the target image resulting from a respective portion of the length of the selector image, and the scattered electrons of the target image are dispersed in energy, the direction of dispersion of the scattered electrons being substantially perpendicular to the length of the elongate target image, whereby a rectangular image is formed o
REFERENCES:
patent: 3777159 (1973-12-01), Hammond et al.
patent: 4300045 (1981-11-01), Ibach et al.
patent: 4435642 (1984-03-01), Neugebaur et al.
patent: 4559449 (1985-12-01), Kesmodel
patent: 4584474 (1986-04-01), Franchy
patent: 4758723 (1988-07-01), Wardell et al.
patent: 4851670 (1989-07-01), Krivanek
Anderson Bruce C.
The Victoria University of Manchester
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