EP0123860A2 - Electron energy analyser with a multichannel detector - Google Patents

Electron energy analyser with a multichannel detector Download PDF

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Publication number
EP0123860A2
EP0123860A2 EP84102967A EP84102967A EP0123860A2 EP 0123860 A2 EP0123860 A2 EP 0123860A2 EP 84102967 A EP84102967 A EP 84102967A EP 84102967 A EP84102967 A EP 84102967A EP 0123860 A2 EP0123860 A2 EP 0123860A2
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EP
European Patent Office
Prior art keywords
channel
electron
gap
mask
channel plate
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EP84102967A
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German (de)
French (fr)
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EP0123860A3 (en
Inventor
Rene Dr. Franchy
Harald Prof. Dr. Ibach
Heinz-Dieter Bruchmann
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Forschungszentrum Juelich GmbH
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Forschungszentrum Juelich GmbH
Kernforschungsanlage Juelich GmbH
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J49/00—Particle spectrometers or separator tubes
    • H01J49/44—Energy spectrometers, e.g. alpha-, beta-spectrometers
    • H01J49/46—Static spectrometers
    • H01J49/48—Static spectrometers using electrostatic analysers, e.g. cylindrical sector, Wien filter
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J49/00—Particle spectrometers or separator tubes
    • H01J49/02—Details
    • H01J49/025—Detectors specially adapted to particle spectrometers

Definitions

  • the invention relates to an electron energy analyzer according to the preamble of patent claim 1.
  • Electron energy analyzers are used especially in combination with a suitable electron monochromator as an electron spectrometer for the analysis of gases and solid surfaces, as well as for the investigation of vibration spectra of adsorbates and thus in catalysis research (see H. Ibach, DL Mills "Electron Energy Loss Spectroscopy and Surface Vibrations "Acad. Press, New York 1982).
  • the electrons pass through different paths according to their energy and reach a multichannel detector (see JL Wiza "Nucl. Instr. And Meth. 162 (1979) 567) at positions which are correlated with their energy If you carry out a location-sensitive analysis, you get a partial spectrum (or total spectrum) of the electrons.
  • a multi-channel detection in electron energy loss spectroscopy requires that a low interference background is guaranteed, since the electron energy loss to be measured Signals are several orders of magnitude smaller than the electron signals that reach the detector without loss of energy (elastically reflected).
  • the invention has for its object to provide an electron energy analyzer with multi-channel detector with the lowest possible interference background.
  • an electron energy analyzer of the type mentioned which is characterized by a grid to be brought to the potential of the input gap at the output of the analyzer at the smallest possible distance from the channel plate (s), the mesh size of which small compared to the dimension of the electron beam is that the grid does not result in any additional structure in the registered electron spectrum, with a masking mask that fades out, the masking of which corresponds to the beam dimension and the distance of the electrodes in the analyzer, and that in order to extract the from it facing channel plate surface scattered electrons is brought sufficient potential compared to this surface.
  • Such a multi-channel detection can improve the sensitivity of an electron impact spectrometer by approximately two orders of magnitude.
  • FIG. 1 A typical embodiment of an electron energy analyzer with a multi-channel detector and a low background noise is shown in FIG.
  • the electrons reflected from a sample are analyzed for their energy in an energy dispersive analyzer (127 ° cylinder, hemisphere, cylinder mirror, plate - mirror analyzer).
  • an energy dispersive analyzer 127 ° cylinder, hemisphere, cylinder mirror, plate - mirror analyzer.
  • FIG. 1 a 127 ° cylinder analyzer is shown: the electrons coming from the input slit (input slit plate 1) are deflected with the aid of the electrodes 2 of the energy analyzer and pass through the grid 3 into the channel plate system 4 (designed as a tandem channel plate) ) and finally through the gap mask 5 onto the resistance plate 6 (instead of the tandem channel plates, for example, a single-stage curved channel plate can also be provided).
  • the resistance plate 6 the location of the electrons striking the channel plate is determined in any manner (e.g. rise time difference
  • the gap of the input slit plate 1 has the height h, which determines the height of the electron beam to be measured, which falls on the detector after passing through the analyzer. Scattered electrons can, however, strike the channel plate above or below the position corresponding to the height "h" and thus generate an interference background.
  • the mask 7 of the grating 3 (see FIGS. 2a and 2b) in front of the channel plate 4 now prevents the stray electrons that do not correspond to the desired image of the entrance slit from reaching the channel plate: the stray electrons can pass the opaque coated part (see FIG 2b) do not penetrate.
  • the lattice is preferably coated with a substance with a low electron emission coefficient (e.g. graphite) in order to reduce the backscattering of electrons.
  • a substance with a low electron emission coefficient e.g. graphite
  • the electrons of the beam height "h" to be measured penetrate the grating and are detected in the detector.
  • the electrons strike the channel plate (s), in addition to the desired electron multiplication effect, scattered electrons (distributed over the entire channel plate) arise, which increase the background noise.
  • the insulated fastening (insulator 8 above the holder 9 of the channel plates 4) of the grid (with grid mask) allows the application of a voltage difference between the grid and the channel plate, so that the scattering electrons can be extracted.
  • the smaller the distance "d" see Fig. 2a), the lower the interference background is, the greater.
  • the input and output of the electron energy analyzer should be at the same potential. If there was a channel plate at the output of the analyzer, a correction of the input channel plate potential would have to be provided due to the work function and the penetration of the supply voltage of the channel plates.
  • the lattice coated with the same substance as the inlet slit 1 of the analyzer according to FIG. 1 now enables the use of different channel plates without having to compensate for their work function.
  • the channel plates typically have a thickness of 0.5 mm and require a voltage difference of approximately 1000 V for electron multiplication. With this voltage difference, an interfering penetration of the voltage into the area of the analyzer would be unavoidable, which likewise leads to a difference in the input and output potentials of the analyzer.
  • the channel plates usually have a dark count rate of 1 pulse / cm 2 sec. With an active diameter of the channel plates of 12.5 mm, this means a dark count rate of about 5 pulses / sec.
  • the gap mask (5) (with gap 10 and impermeable part 11, see FIGS. 3a and 3b) between the outlet of the channel plate 4 and the resistance plate 6 lowers the interference background by Factor that corresponds to the ratio of the gap area to the total active area of the channel plate.
  • the length of the gap corresponds to the distance between the two electrodes 2 of the electron energy analyzer according to FIG. 1.
  • the height of the gap corresponds to the height "h” of the electron beam used, plus 2 times the diffusion width (about 0.5 mm) of the channel plates and resistance plate Arrangement.
  • the diffusion width "1" is understood to mean the broadening that an electron beam of width "b” experiences as it passes through the channel plates until it hits the resistance plate (see FIG. 4).
  • the interference background is reduced by a factor of 10.
  • the gap mask 5 is used to hold the outlet duct plate (4).

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Analysing Materials By The Use Of Radiation (AREA)
  • Electron Tubes For Measurement (AREA)
  • Measurement Of Radiation (AREA)

Abstract

Bei einem Elektronenenergie-Analysator, bei dem die über einen Eingangsspalt in das energiedispersive System gelangenden Elektronen am Ausgang desselben mit einem mit Kanalplatten arbeitenden Vielkanaldetektor simultan analysiert werden, wird der Störpegel durch ein Spalt/Gitter-System am Ausgang des Analysators herabgesetzt. Dieses umfaßt ein auf das Potential des Eingangsspalts zu bringendes, möglichst feinmaschiges Gitter (3) am Ausgang des Analysators, das in möglichst geringem Abstand von der oder den Kanalplatte(n) (4) angeordnet ist sowie ein ausblendende Gittermaske, deren Ausblendung der Strahldimension und dem Abstand der Elektroden (2) im Analysator entspricht. Das Gitter wird auf ein ausreichendes Potential zum Absaugen von an der Kanalplattenfläche entstehenden Streuelektronen gebracht. Vorzugsweise wird bei einem Detektor mit Widerstandsplatte (6) am Ausgang der Kanalplatte(n) (4) eine Spalt-Maske (5) zwischen Widerstandsplatte und Kanalplatte(n) vorgesehen, deren Spaltfläche der freien Fläche der Gitter-Maske entspricht.In the case of an electron energy analyzer, in which the electrons entering the energy-dispersive system via an input gap are simultaneously analyzed at the output of the same with a multi-channel detector working with channel plates, the interference level is reduced by a gap / grating system at the output of the analyzer. This comprises a mesh (3) at the output of the analyzer which is to be brought to the potential of the input gap and is as fine-meshed as possible, which is arranged as close as possible to the channel plate (s) (4) as well as a masking mask, the masking of the beam dimension and corresponds to the distance between the electrodes (2) in the analyzer. The grating is brought to a sufficient potential for the extraction of scattering electrons which are formed on the channel plate surface. In the case of a detector with a resistance plate (6), a gap mask (5) is preferably provided between the resistance plate and the channel plate (s) at the outlet of the channel plate (s) (4), the gap surface of which corresponds to the free area of the grating mask.

Description

Die Erfindung bezieht sich auf einen Elektronenenergie-Analysator gemäß dem Oberbegriff des Patentanspruchs 1.The invention relates to an electron energy analyzer according to the preamble of patent claim 1.

Elektronenenergie-Analysatoren werden insbesondere in Kombination mit einem geeigneten Elektronen-Monochromator als Elektronenspektrometer zur Analyse von Gasen und Festkörperoberflächen, sowie zur Untersuchung von Schwingungsspektren von Adsorbaten und damit in der Katalyseforschung verwendet (s. H. Ibach, D.L. Mills "Electron Energy Loss Spectroscopy and Surface Vibrations" Acad. Press, New York 1982).Electron energy analyzers are used especially in combination with a suitable electron monochromator as an electron spectrometer for the analysis of gases and solid surfaces, as well as for the investigation of vibration spectra of adsorbates and thus in catalysis research (see H. Ibach, DL Mills "Electron Energy Loss Spectroscopy and Surface Vibrations "Acad. Press, New York 1982).

Bei einem solchen Elektronenenergie-Analysator durchlaufen die Elektronen entsprechend ihrer Energie verschiedene Bahnen und gelangen auf einen Vielkanaldetektor (s. J.L. Wiza "Nucl. Instr. and Meth. 162 (1979) 567) an Positionen, die mit ihrer Energie korreliert sind. Führt man nun eine ortsempfindliche Analyse durch, so erhält man ein Teilspektrum(oder Gesamtspektrum) der Elektronen.In such an electron energy analyzer, the electrons pass through different paths according to their energy and reach a multichannel detector (see JL Wiza "Nucl. Instr. And Meth. 162 (1979) 567) at positions which are correlated with their energy If you carry out a location-sensitive analysis, you get a partial spectrum (or total spectrum) of the electrons.

Eine Vielkanaldetektion in der Elektronenenergieverlust-Spektroskopie setzt voraus, daß ein niedriger Störuntergrund gewährleistet ist, da die zu messenden Elektronen-Energie-Verlust-Signale um einige Größenordnungen kleiner sind als die Elektronen-Signale, die ohne Energie-Verlust (elastisch reflektiert) auf den Detektor gelangen.A multi-channel detection in electron energy loss spectroscopy requires that a low interference background is guaranteed, since the electron energy loss to be measured Signals are several orders of magnitude smaller than the electron signals that reach the detector without loss of energy (elastically reflected).

Die aus diesem Grund dem eigentlichen Nachweiselement bekanntermaßen vorgeschaltete Anordnung eines Analysators mit Kanalplatte(n) an seinem Ausgang ist noch nicht voll befriedigend.The arrangement of an analyzer with a channel plate (s) at its outlet, which is known to be upstream of the actual detection element for this reason, is not yet completely satisfactory.

Der Erfindung liegt die Aufgabe zugrunde, einen Elektronenenergie-Analysator mit Vielkanaldetektor mit einem möglichst niedrigen Störuntergrund anzugeben.The invention has for its object to provide an electron energy analyzer with multi-channel detector with the lowest possible interference background.

Diese Aufgabe wird gemäß der Erfindung durch einen Elektronenenergie-Analysator der eingangs genannten Art gelöst, der gekennzeichnet ist durch ein auf das Potential des Eingangsspalts zu bringendes Gitter am Ausgang des Analysators in möglichst geringem Abstand von der oder den Kanalplatte(n), dessen Maschendimension derart klein gegen die Dimension des Elektronenstrahls ist, daß sich durch das Gitter keine zusätzliche Struktur im registrierten Elektronenspektrum ergibt, mit einer ausblendenden Gitter-Maske, deren Ausblendung der Strahldimension und dem Abstand der Elektroden im Analysator entspricht und das auf ein zum Absaugen der von der ihm zugewandten Kanalplattenfläche gestreuten Elektronen ausreichendes Potential gegenüber dieser Fläche gebracht wird.This object is achieved according to the invention by an electron energy analyzer of the type mentioned, which is characterized by a grid to be brought to the potential of the input gap at the output of the analyzer at the smallest possible distance from the channel plate (s), the mesh size of which small compared to the dimension of the electron beam is that the grid does not result in any additional structure in the registered electron spectrum, with a masking mask that fades out, the masking of which corresponds to the beam dimension and the distance of the electrodes in the analyzer, and that in order to extract the from it facing channel plate surface scattered electrons is brought sufficient potential compared to this surface.

Durch eine solche Vielkanaldetektion kann die Empfindlichkeit eines Elektronenstoßspektrometers um etwa zwei Größenordnungen verbessert werden.Such a multi-channel detection can improve the sensitivity of an electron impact spectrometer by approximately two orders of magnitude.

Die wirksame Erniedrigung des Störuntergrundes wird im wesentlichen durch folgende Effekte erreicht:

  • 1. Streuelektronen, die auf den für Elektronen undurchlässigen Teil der Gitter-Maske stoßen (deren durchlässiger Teil oder "Spalt" der Höhe des zu messenden Elektronenstrahls entspricht), werden von der Kanalplatte ferngehalten.
  • 2. Streuelektronen, die durch den Stoß der Elektronen mit der Kanalplatte entstehen, werden durch das Gitter abgesaugt, das sich auf einem geeigneten Potential befindet.
  • 3. Streuelektronen, die beim Elektronenbeschuß von Maske und Gitter entstehen können, werden vorzugsweise durch eine Beschichtung des Maske-Gitter-Systems mit einer Substanz mit kleinem Sekundärelektronenemissionskoeffizienten vermindert.
  • 4. Die durch die Kanalplatten bedingte Dunkelzählrate kann durch Einschaltung einer Spalt- Maske zwischen Ausgang der Kanalplatte(n) und Widerstandsplatte reduziert werden, und zwar um einen Faktor, der dem Verhältnis der Fläche des Spaltes zur aktiven Gesamtfläche der Kanalplatte entspricht.
The effective lowering of the interference background is essentially achieved by the following effects:
  • 1. Scattered electrons that strike the electron-impermeable part of the grid mask (whose permeable part or "gap" corresponds to the height of the electron beam to be measured) are kept away from the channel plate.
  • 2. Scattered electrons, which result from the impact of the electrons with the channel plate, are sucked off through the grid, which is at a suitable potential.
  • 3. Scattered electrons, which can arise during electron bombardment of the mask and the lattice, are preferably reduced by coating the mask-lattice system with a substance with a small secondary electron emission coefficient.
  • 4. The dark count rate caused by the channel plates can be reduced by switching on a gap mask between the output of the channel plate (s) and the resistance plate, by a factor which corresponds to the ratio of the area of the gap to the total active area of the channel plate.

Weitere Besonderheiten der Erfindung gehen aus den Unteransprüchen und der nachfolgenden Beschreibung eines Ausführungsbeispiels unter Bezugnahme auf die angefügten Zeichnungen hervor;Further special features of the invention emerge from the subclaims and the following description of an exemplary embodiment with reference to the attached drawings;

es zeigen (schematisch):

  • Figur 1 einen Elektronenenergie-Analysator mit erfindungsgemäßer Detektoranordnung (in Aufsicht und Vorderansicht);
  • Figur 2 Vorder- und Seitenansicht von Gitter und Gittermaske;
  • Figur 3 Vorder- und Seitenansicht der Spaltmaske; und
  • Figur 4 ein Schema zur Erläuterung der Diffusionsbreite.
it shows (schematically):
  • 1 shows an electron energy analyzer with a detector arrangement according to the invention (in plan and front view);
  • Figure 2 front and side view of the grid and grid mask;
  • FIG. 3 front and side view of the slit mask; and
  • Figure 4 is a diagram for explaining the diffusion width.

Eine typische Ausführungsform eines Elektronenenergie-Analysators mit Vielkanaldetektor und niedrigem Störuntergrund ist in Figur 1 dargestellt. Die von einer Probe reflektierten Elektronen werden bezüglich ihrer Energie in einem energiedispersiven Analysator (127°-Zylinder-, Halbkugel-, Zylinder-Spiegel-, Platten--Spiegel-Analysator) analysiert. Im Ausführungsbeispiel, Figur 1, ist ein 127°-Zylinder-Analysator gezeigt: Die vom Eingangsspalt (Eingangsspaltplatte 1) herkommenden Elektronen werden mit Hilfe der Elektroden 2 des Energieanalysators abgelenkt und gelangen durch das Gitter 3 in das Kanalplattensystem 4 (ausgebildet als Tandem-Kanalplatte) und schließlich durch die Spaltmaske 5 auf die Widerstandsplatte 6 (statt der Tandem-Kanalplatten kann auch z.B. eine einstufige gekrümmte Kanalplatte vorgesehen werden). Mit Hilfe der Widerstandsplatte 6 wird in beliebig zu wählender Art und Weise (z.B. Anstiegszeitdifferenz- oder Ladungsteilung-Messung) der Ort der auf die Kanalplatte stoßenden Elektronen bestimmt.A typical embodiment of an electron energy analyzer with a multi-channel detector and a low background noise is shown in FIG. The electrons reflected from a sample are analyzed for their energy in an energy dispersive analyzer (127 ° cylinder, hemisphere, cylinder mirror, plate - mirror analyzer). In the exemplary embodiment, FIG. 1, a 127 ° cylinder analyzer is shown: the electrons coming from the input slit (input slit plate 1) are deflected with the aid of the electrodes 2 of the energy analyzer and pass through the grid 3 into the channel plate system 4 (designed as a tandem channel plate) ) and finally through the gap mask 5 onto the resistance plate 6 (instead of the tandem channel plates, for example, a single-stage curved channel plate can also be provided). With the help of the resistance plate 6, the location of the electrons striking the channel plate is determined in any manner (e.g. rise time difference or charge sharing measurement).

Der Spalt der Eingangsspaltplatte 1 hat die Höhe h, welche die Höhe des zu messenden Elektronenstrahls bestimmt, der nach Durchgang des Analysators auf den Detektor fällt. Gestreute Elektronen können aber über oder unter der der Höhe "h" entsprechenden Position auf die Kanalplatte auftreffen und so einen Störuntergrund erzeugen. Die Maske 7 des Gitters 3 (s. Figur 2a und 2b) vor der Kanalplatte 4 verhindert nun, daß die Streuelektronen, die nicht der gewünschten Abbildung des Eingangsspalts entsprechen, auf die Kanalplatte gelangen: Die Streuelektronen können den undurchlässigen beschichteten Teil (s. Abb. 2b) nicht durchdringen.The gap of the input slit plate 1 has the height h, which determines the height of the electron beam to be measured, which falls on the detector after passing through the analyzer. Scattered electrons can, however, strike the channel plate above or below the position corresponding to the height "h" and thus generate an interference background. The mask 7 of the grating 3 (see FIGS. 2a and 2b) in front of the channel plate 4 now prevents the stray electrons that do not correspond to the desired image of the entrance slit from reaching the channel plate: the stray electrons can pass the opaque coated part (see FIG 2b) do not penetrate.

Das Gitter wird vorzugsweise mit einer Substanz mit niedrigem Elektronenemissionskoeffizienten (z.B. Graphit) beschichtet, um die Rückstreuung von Elektronen zu vermindern.The lattice is preferably coated with a substance with a low electron emission coefficient (e.g. graphite) in order to reduce the backscattering of electrons.

Die zu messenden Elektronen der Strahlhöhe "h" durchdringen das Gitter und werden im Detektor nachgewiesen. Beim Auftreffen der Elektronen auf die Kanalplatte(n) entstehen neben dem gewünschten Effekt der Elektronenvervielfachung durch die Kanalplatte reflektierte Streuelektronen (verteilt über die gesamte Kanalplatte), die den Störuntergrund erhöhen. Die isolierte Befestigung (Isolator 8 über der Halterung 9 der Kanalplatten 4) des Gitters (mit Gittermaske) erlaubt das Anlegen einer Spannungsdifferenz zwischen dem Gitter und der Kanalplatte, so daß die Streuelektronen abgesaugt werden können. Je kleiner der Abstand "d" (s. Abb. 2a) ist, um so größer ist die Erniedrigung des Störuntergrunds.The electrons of the beam height "h" to be measured penetrate the grating and are detected in the detector. When the electrons strike the channel plate (s), in addition to the desired electron multiplication effect, scattered electrons (distributed over the entire channel plate) arise, which increase the background noise. The insulated fastening (insulator 8 above the holder 9 of the channel plates 4) of the grid (with grid mask) allows the application of a voltage difference between the grid and the channel plate, so that the scattering electrons can be extracted. The smaller the distance "d" (see Fig. 2a), the lower the interference background is, the greater.

Eingang und Ausgang des Elektronenenergie-Analysators sollten auf gleichem Potential sein. Befände sich am Ausgang des Analysators eine Kanalplatte, so müßte wegen der Austrittsarbeit und wegen des Durchgriffs der Versorgungsspannung der Kanalplatten eine Korrektur des Eingangskanalplatten-Potentials vorgesehen werden. Das mit der gleichen Substanz wie der Eingangs-Spalt 1 des Analysators gemäß Figur 1 beschichtete Gitter ermöglicht nun die Verwendung verschiedener Kanalplatten, ohne daß deren Austrittsarbeit kompensiert werden muß.The input and output of the electron energy analyzer should be at the same potential. If there was a channel plate at the output of the analyzer, a correction of the input channel plate potential would have to be provided due to the work function and the penetration of the supply voltage of the channel plates. The lattice coated with the same substance as the inlet slit 1 of the analyzer according to FIG. 1 now enables the use of different channel plates without having to compensate for their work function.

Die Kanalplatten haben typischerweise eine Dicke von 0,5 mm und benötigen zur Elektronenvervielfachung eine Spannungsdifferenz von etwa 1000 V. Bei dieser Spannungsdifferenz wäre ein störender Durchgriff der Spannung in den Bereich des Analysators unvermeidbar, was ebenfalls zu einem Unterschied der Eingangs- und Ausgangs-Potentiale des Analysators führen würde. Das auf geeignetem Potential befindliche Gitter-System (3, 7) vor der Kanalplatte 4 verhindert den Durchgriff der Kanalplattenspannung in den Analysatorraum.The channel plates typically have a thickness of 0.5 mm and require a voltage difference of approximately 1000 V for electron multiplication. With this voltage difference, an interfering penetration of the voltage into the area of the analyzer would be unavoidable, which likewise leads to a difference in the input and output potentials of the analyzer. The grid system (3, 7 ) in front of the channel plate 4, which is at a suitable potential, prevents the passage of the channel plate voltage in the analyzer room.

Die Kanalplatten haben üblicherweise eine Dunkelzählrate von 1 Impuls/cm2sec. Bei einem aktiven Durchmesser der Kanalplatten von 12,5 mm bedeutet dies eine Dunkelzählrate von etwa 5 Impulsen/sec. Die Spalt-Maske (5) (mit Spalt 10 und undurchlässigem Teil 11, s. Figur 3a und 3b) zwischen dem Ausgang der Kanalplatte 4 und der Widerstandsplatte 6 erniedrigt den Störuntergrund um den Faktor, der dem Verhältnis der Spaltfläche zur aktiven Gesamtfläche der Kanalplatte entspricht.The channel plates usually have a dark count rate of 1 pulse / cm 2 sec. With an active diameter of the channel plates of 12.5 mm, this means a dark count rate of about 5 pulses / sec. The gap mask (5) (with gap 10 and impermeable part 11, see FIGS. 3a and 3b) between the outlet of the channel plate 4 and the resistance plate 6 lowers the interference background by Factor that corresponds to the ratio of the gap area to the total active area of the channel plate.

Die Länge des Spaltes entspricht dem Abstand zwischen den beiden Elektroden 2 des Elektronenenergie-Analysators gemäß Figur 1. Die Höhe des Spaltes entspricht der Höhe "h" des verwendeten Elektronenstrahls plus 2 mal die Diffusionsbreite (etwa 0,5 mm) der Kanalplatten und Widerstandsplatten-Anordnung. Unter der Diffusionsbreite "1" versteht man die Verbreiterung, die ein Elektronenstrahl der Breite "b" beim Durchlaufen der Kanalplatten bis zum Auftreffen auf die Widerstandsplatte erfährt (s. Figur 4).The length of the gap corresponds to the distance between the two electrodes 2 of the electron energy analyzer according to FIG. 1. The height of the gap corresponds to the height "h" of the electron beam used, plus 2 times the diffusion width (about 0.5 mm) of the channel plates and resistance plate Arrangement. The diffusion width "1" is understood to mean the broadening that an electron beam of width "b" experiences as it passes through the channel plates until it hits the resistance plate (see FIG. 4).

Bei einem 127°-Zylinder-Analysator, der einen Elektronenstrahl der Höhe 2 mm verwendet und einen Elektrodenabstand von 25 mm hat, erhält man eine Reduktion des Störuntergrunds um den Faktor 10.With a 127 ° cylinder analyzer that uses an electron beam with a height of 2 mm and an electrode spacing of 25 mm, the interference background is reduced by a factor of 10.

Um den Abstand zwischen dem Ausgang der Kanalplatte und der Widerstandsplatte klein zu halten, damit eine hohe Ortsauflösung realisiert wird, wird die Spalt-Maske 5 zur Halterung der Ausgangskanalplatte (4) verwendet.In order to keep the distance between the outlet of the duct plate and the resistance plate small, so that a high spatial resolution is achieved, the gap mask 5 is used to hold the outlet duct plate (4).

Versuche haben gezeigt, daß durch die erfindungsgemäßen Maßnahmen der Störuntergrund erheblich reduziert wird.Tests have shown that the interference background is considerably reduced by the measures according to the invention.

Claims (6)

1. Elektronenenergie-Analysator, bei dem die über einen Eingangsspalt in das energiedispersive System gelangenden Elektronen am Ausgang desselben mit einem mit Kanalplatten arbeitenden Vielkanaldetektor simultan analysiert werden, gekennzeichnet durch ein auf das Potential des Eingangsspalts zu bringendes Gitter (3) am Ausgang des Analysators in möglichst geringem Abstand von der oder den Kanalplatte(n) (4), dessen Maschendimension derart klein gegen die Dimension des Elektronenstrahls ist, daß sich durch das Gitter (3) keine zusätzliche Struktur im registrierten Elektronenspektrum ergibt, mit einer ausblendenden Gittermaski (7), deren Ausblendung der Strahldimension und dem Abstand der Elektroden (2) im Analysator entspricht und das auf ein zum Absaugen der von der ihm zugewandten Kanalplattenfläche gestreuten Elektronen ausreichendes Potential gegenüber dieser Fläche gebracht wird.1.Electronic energy analyzer, in which the electrons entering the energy-dispersive system via an input gap are simultaneously analyzed at the output of the same with a multi-channel detector working with channel plates, characterized by a grid (3) to be brought to the potential of the input gap at the output of the analyzer in the smallest possible distance from the channel plate (s) (4), the mesh dimension of which is so small compared to the dimension of the electron beam that there is no additional structure in the registered electron spectrum due to the grating (3), with a masking grating mask (7), whose blanking corresponds to the beam dimension and the spacing of the electrodes (2) in the analyzer and which is brought to a sufficient potential in relation to this surface to extract the electrons scattered from the channel plate surface facing it. 2. Elektronenenergie-Analysator, dadurch gekennzeichnet , daß das Potential des Gitters (3) (gegenüber der Kanalplattenfläche) für bis 20 V reichende Elektronenstrahlenergien zwischen 0 und 2 V liegt.2. Electron energy analyzer, characterized in that the potential of the grid (3) (opposite the channel plate surface) for electron beam energies reaching up to 20 V is between 0 and 2 V. 3. Elektronenenergie-Analysator nach Anspruch 1 oder 2, dadurch gekennzeichnet , daß Gitter (3) und Maske (7) mit einer Substanz mit niedrigem Sekundärelektronenemissionskoeffizienten beschichtet sind.3. Electron energy analyzer according to claim 1 or 2, characterized in that the grating (3) and mask (7) with one Substance with a low secondary electron emission coefficient are coated. 4. Elektronenenergie-Analysator nach einem der Ansprüche 1 bis 3, gekennzeichnet durch einen Detektor mit Widerstandsplatte (6) am Ausgang der Kanalplatte(n) (4) und eine Spalt-Maske (5) zwischen Widerstandsplatte und Kanalplatte(n), bei der die Fläche des Spaltes (10) der freien Fläche der Gitter-Maske (7) entspricht.4. Electron energy analyzer according to one of claims 1 to 3, characterized by a detector with a resistance plate (6) at the outlet of the channel plate (s) (4) and a gap mask (5) between the resistance plate and channel plate (s), in which the area of the gap (10) corresponds to the free area of the grid mask (7). 5. Elektronenenergie-Analysator nach einem der vorangehenden Ansprüche, gekennzeichnet durch eine Maschenweite des Gitters (3) zwischen 10 und 100 µm.5. Electron energy analyzer according to one of the preceding claims, characterized by a mesh size of the grid (3) between 10 and 100 microns. 6. Elektronenenergie-Analysator nach einem der vorangehenden Ansprüche, gekennzeichnet durch eine Gitterdicke unter 0,5 mm, insbesondere von 10 bis 100 µm.6. Electron energy analyzer according to one of the preceding claims, characterized by a lattice thickness below 0.5 mm, in particular from 10 to 100 µm.
EP84102967A 1983-03-26 1984-03-17 Electron energy analyser with a multichannel detector Withdrawn EP0123860A3 (en)

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DE19833311195 DE3311195A1 (en) 1983-03-26 1983-03-26 ELECTRONIC POWER ANALYZER WITH MULTI-CHANNEL DETECTOR
DE3311195 1983-03-26

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US4584474A (en) 1986-04-22
DE3311195A1 (en) 1984-10-04
JPS59189548A (en) 1984-10-27
EP0123860A3 (en) 1986-01-15

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