EP0276731B1 - Method for electron beam guidance with energy selection, and electron spectrometer - Google Patents
Method for electron beam guidance with energy selection, and electron spectrometer Download PDFInfo
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- EP0276731B1 EP0276731B1 EP88100724A EP88100724A EP0276731B1 EP 0276731 B1 EP0276731 B1 EP 0276731B1 EP 88100724 A EP88100724 A EP 88100724A EP 88100724 A EP88100724 A EP 88100724A EP 0276731 B1 EP0276731 B1 EP 0276731B1
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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
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J49/00—Particle spectrometers or separator tubes
- H01J49/02—Details
- H01J49/06—Electron- or ion-optical arrangements
Definitions
- the invention relates to a method for electron beam guidance with focussing energy selection in an energy-dispersive system with different focussing in two mutually perpendicular directions (especially in the energy selection direction and perpendicular to it with systems focusing only in one plane), and to electron spectrometers with at least one energy-dispersive system with such a beam guidance.
- Bundled electrons with a certain energy are used for the treatment and investigation of surfaces and gases.
- energy-dispersive systems are known which are used either individually as analyzers or as monochromators or in combination of analyzer and monochromator as so-called electron impact spectrometers.
- Energy-dispersive systems as analyzers are used, for example, in UV or X-ray photoelectron spectroscopy (also known under the name ESCA) and in Auger spectroscopy.
- ESCA UV or X-ray photoelectron spectroscopy
- Auger spectroscopy electrons emitted by the sample are transmitted through analyzes the analyzer for its kinetic energy.
- a lens system located between the sample and the analyzer takes care of the beam transport, the adaptation of the electron energy to the transmission energy of the analyzer and the necessary enlargement or reduction of the image of the imaged area of the sample to adapt to the input slot of the analyzer.
- Energy dispersive systems are also used to produce monochromatic electron beams, such as in inverse photoemission spectroscopy. Similar to the analyzer described above, lens systems are used between the monochromator and the sample for beam transport, for adjusting the energy and the image size.
- the electrons emitted by a cathode are monochromatized in one or more monochromators and directed onto a sample through a lens system, the energy of the electrons on the sample usually being different from the energy in the monochromators.
- the electrons hitting the sample are scattered by the sample and suffer characteristic energy losses, for example through excitation of oscillation quanta.
- the scattered electrons are directed through a lens system onto the entrance slit of one or more energy-dispersive elements conducted, which analyze the scattered electrons with regard to their energy distribution, and detected in a detector.
- Electron spectrometers of this type are used in particular for vibration spectroscopy and for the investigation of electronic losses on solid surfaces and are manufactured by a number of companies.
- the invention is therefore based on the object of providing such a beam guide with focusing energy selection or an electron spectrometer, by means of which a high energy resolution with a high electron current is achieved on the sample or on the detector.
- the inventive method of the type mentioned is characterized in that the different focusing of the electrons in the two mutually perpendicular directions is corrected by a non-circularly symmetrical lens system connected downstream or upstream of the energy-dispersive system in such a way that either the virtual or the real one Input aperture of the energy dispersive system on a given image level outside of the energy dispersive System or a sample outside the energy-dispersive system on the virtual or real output aperture of the same is mapped.
- the lens systems to be used for this purpose described with different focusing in two mutually perpendicular directions are designed or dimensioned in consideration of the focus specification and the electron trajectories in the energy-dispersive system.
- rectangular lens cross-sectional profiles can be used, in which the height and width are matched to one another in such a way that the described image occurs in cooperation with the different focusing of the electrons in the two mutually perpendicular directions within the energy-dispersive system.
- the symmetry axes of the rectangular profile must then be parallel or perpendicular to the radial plane.
- the required height and width of the lens cross-sectional profiles are calculated by solving the Laplace equation in three dimensions and calculating the electron orbits in three dimensions in the manner known to the person skilled in the art.
- Devices with beam guidance include electron monochromators with a subsequent corrective lens system between the monochromator and sample, analyzers with an upstream corrective lens system between the sample and analyzer, and electron impact spectrometers with such a lens system between the monochromator and sample and / or between the sample and analyzer.
- electron monochromators with a subsequent corrective lens system between the monochromator and sample analyzers with an upstream corrective lens system between the sample and analyzer
- electron impact spectrometers with such a lens system between the monochromator and sample and / or between the sample and analyzer.
- an electron impact spectrometer as described, consists of a monochromator part with a downstream lens system and an analyzer part with a preceding lens system
- the invention can, however, also be used separately for the monochromator with a downstream lens system and the analyzer with an upstream lens system for the various applications.
- plate capacitors can also be used, which also focus only in one plane. It is also possible to use energy-dispersive systems which have a different, in each case non-zero, focusing in two mutually perpendicular directions, in which case the lens system must be suitably adapted (selection of the height and width of the lens profiles) in such a way that the desired focusing occurs .
- the electron impact spectrometer shown in Figure 1 comprises a cathode system 1, two monochromators 2 and 3, each a lens system consisting of three elements 4, 5 and 6 or 8, 9 and 10 between the monochromators and the sample 7 and between the sample 7 and the Analyzers 11 and 12, two analyzers 11 and 12 and a detector 13.
- the two lens systems between the monochromator and the sample and between the sample and the analyzer are symmetrical to one another, so that the lens elements 4 and 10, 5 and 9 and 6 and 8 are identical to one another.
- FIGS. 2 and 3 The cross-sectional profiles of these lens elements 4 to 6 (or 8 to 10) are shown in FIGS. 2 and 3: Of these, the lens element 4 is tapered in a trapezoidal or stepped manner and the elements 5 and 6 are designed in a rectangular shape.
- the height and width of the profiles of the lens elements 8, 9 and 10 are coordinated so that in the radial plane the sample is imaged on the inlet slit of the first analyzer, perpendicularly the sample is imaged on the outlet slit of the last analyzer, so that a total of one image the sample is created at the exit slit of the second analyzer.
- the monochromatic current achieved using the lens system according to the invention, measured on the detector, as a function of the resolution is shown in FIG. 5, curve a.
- curve b shows analog values for a spectrometer which does not have the lens system according to the invention, but is otherwise identical in terms of monochromators and analyzers.
- the results refer to one Electron energy on the sample of 100 eV, while the energy of the electrons in the monochromators and analyzers (depending on the resolution) is less than 1 eV.
Description
Die Erfindung bezieht sich auf ein Verfahren zur Elektronenstrahl-Führung mit fokussierender Energieselektion in einem energiedispersiven System mit unterschiedlicher Fokussierung in zwei zueinander senkrechten Richtungen (speziell in Energieselektionsrichtung und senkrecht dazu bei nur in einer Ebene fokussierenden Systemen), sowie auf Elektronenspektrometer mit zumindest einem energiedispersiven System mit einer solchen Strahlführung.The invention relates to a method for electron beam guidance with focussing energy selection in an energy-dispersive system with different focussing in two mutually perpendicular directions (especially in the energy selection direction and perpendicular to it with systems focusing only in one plane), and to electron spectrometers with at least one energy-dispersive system with such a beam guidance.
Gebündelte Elektronen mit bestimmter Energie werden für die Behandlung und Untersuchung von Oberflächen und Gasen angewandt. Für eine fokussierende Energieselektion sind energiedispersive Systeme bekannt, die entweder einzeln als Analysatoren oder als Monochromatoren oder in Kombination von Analysator und Monochromator als sog. Elektronenstoßspektrometer zum Einsatz kommen.Bundled electrons with a certain energy are used for the treatment and investigation of surfaces and gases. For a focusing energy selection, energy-dispersive systems are known which are used either individually as analyzers or as monochromators or in combination of analyzer and monochromator as so-called electron impact spectrometers.
Energiedispersive Systeme als Analysatoren werden zum Beispiel verwendet in der UV-oder Röntgen-Photoelektronenspektroskopie (auch unter dem Namen ESCA bekannt) und in der Auger-Spektroskopie. Hierbei werden von der Probe emittierte Elektronen durch den Analysator bezüglich ihrer kinetischen Energie analysiert. Ein zwischen der Probe und dem Analysator befindliches Linsensystem sorgt dabei für den Strahltransport, die Anpassung der Elektronenenergie an die Durchlaßenergie des Analysators sowie die nötige Vergrößerung oder Verkleinerung des Bildes der abgebildeten Fläche der Probe zur Anpassung an den Eingangsschlitz des Analysators.Energy-dispersive systems as analyzers are used, for example, in UV or X-ray photoelectron spectroscopy (also known under the name ESCA) and in Auger spectroscopy. Here, electrons emitted by the sample are transmitted through analyzes the analyzer for its kinetic energy. A lens system located between the sample and the analyzer takes care of the beam transport, the adaptation of the electron energy to the transmission energy of the analyzer and the necessary enlargement or reduction of the image of the imaged area of the sample to adapt to the input slot of the analyzer.
Energiedispersive Systeme werden auch verwendet zur Herstellung monochromatischer Elektronenstrahlen, wie zum Beispiel in der inversen Photoemissionsspektroskopie. Ähnlich wie beim vorbeschriebenen Analysator werden zum Strahltransport, zur Anpassung der Energie und der Bildgröße Linsensysteme zwischen Monochromator und der Probe eingesetzt.Energy dispersive systems are also used to produce monochromatic electron beams, such as in inverse photoemission spectroscopy. Similar to the analyzer described above, lens systems are used between the monochromator and the sample for beam transport, for adjusting the energy and the image size.
In einem Elektronenstoßspektrometer werden die von einer Kathode emittierten Elektronen in ein oder mehreren Monochromatoren monochromatisiert und durch ein Linsensystem auf eine Probe gelenkt, wobei üblicherweise die Energie der Elektronen an der Probe verschieden sein kann von der Energie in den Monochromatoren. Die auf die Probe auftreffenden Elektronen werden von dieser gestreut und erleiden dabei charakteristische Energieverluste zum Beispiel durch Anregung von Schwingungsquanten. Die gestreuten Elektronen werden durch ein Linsensystem auf den Eintrittsspalt eines oder mehrerer energiedispersiver Elemente geleitet, die die gestreuten Elektronen hinsichtlich ihrer Energieverteilung analysieren, und in einem Detektor nachgewiesen. Elektronenspektrometer dieser Art werden insbesondere zur Schwingungsspektroskopie und zur Untersuchung elektronischer Verluste an Festkörperoberflächen eingesetzt und von einer Reihe von Firmen hergestellt.In an electron impact spectrometer, the electrons emitted by a cathode are monochromatized in one or more monochromators and directed onto a sample through a lens system, the energy of the electrons on the sample usually being different from the energy in the monochromators. The electrons hitting the sample are scattered by the sample and suffer characteristic energy losses, for example through excitation of oscillation quanta. The scattered electrons are directed through a lens system onto the entrance slit of one or more energy-dispersive elements conducted, which analyze the scattered electrons with regard to their energy distribution, and detected in a detector. Electron spectrometers of this type are used in particular for vibration spectroscopy and for the investigation of electronic losses on solid surfaces and are manufactured by a number of companies.
In einem Elektronenstoßspektrometer wird die maximal erreichbare Intensität des auf die Probe fallenden Strahles und damit auch die Intensität des von diesem erzeugten Nutzsignales grundsätzlich durch die Raumladung im Monochromator begrenzt. Theoretische Rechnungen zeigen (H. Ibach, D.L. Mills, Electron Energy Loss Spectroscopy and Surface Vibrations, Academic Press, New York, 1982, p. 16 ff.), daß die Stärke des monochromatischen Stromes von der Energiebreite des durch den Monochromator hindurchgelassenen Elektronenstrahls abhängt und nur in relativ bescheidenem Umfang durch Auslegungsparameter des Systems beeinflußt werden kann.In an electron impact spectrometer, the maximum achievable intensity of the beam falling on the sample and thus also the intensity of the useful signal generated by it is fundamentally limited by the space charge in the monochromator. Theoretical calculations show (H. Ibach, DL Mills, Electron Energy Loss Spectroscopy and Surface Vibrations, Academic Press, New York, 1982, p. 16 ff.) That the strength of the monochromatic current depends on the energy width of the electron beam transmitted through the monochromator and can only be influenced to a relatively modest extent by design parameters of the system.
Günstige Verhältnisse hinsichtlich der Raumladung ergeben sich insbesondere bei der Verwendung von einem oder mehreren Zylinderkondensatoren mit Schlitzen als Ein- bzw. Austrittsblende. Fokussierung der Elektronen von der Ein- auf die Austrittsblende und Energieselektion erfolgen dabei nur in radialer Richtung, während senkrecht dazu weder Fokussierung noch Energieselektion erfolgt. Die fehlende Fokussierung senkrecht zur Radialebene hat (ohne die erfindungsgemäße Strahlführung) nachteilige Auswirkungen auf die Intensität des Nutzsignals. Dasselbe gilt sinngemäß für den Analysator, wenn dort Zylinderkondensatoren eingesetzt werden.Favorable conditions with regard to the space charge result in particular when using one or more cylindrical capacitors with slots as the inlet or outlet diaphragm. Focusing of the electrons from the entrance to the exit aperture and energy selection take place only in the radial direction, while vertical there is neither focusing nor energy selection. The lack of focusing perpendicular to the radial plane (without the beam guidance according to the invention) has an adverse effect on the intensity of the useful signal. The same applies analogously to the analyzer if cylindrical capacitors are used there.
Es ist versucht worden (siehe EP-PS 0013003), diesen bekannten Nachteil von Zylinderkondensatoren dadurch auszugleichen, daß die von der Kathode emittierten Elektronen in der Radialebene durch ein geeignetes Linsensystem auf den Eintrittsspalt des Monochromators fokussiert werden, während senkrecht dazu durch eine entsprechende Auslegung des Kathodensystems sowie des Linsensystems zwischen Monochromator und Probe und zwischen Probe und Analysator in einem näherungsweise parallelen Strahlengang ohne weiteren Zwischenfokus auf den Detektor fokussiert wird. Gegenüber einer freien nichtfokussierenden Strahlausbreitung bietet diese Strahlführung eine Verbesserung.Attempts have been made (see EP-PS 0013003) to compensate for this known disadvantage of cylindrical capacitors in that the electrons emitted by the cathode are focused in the radial plane by a suitable lens system on the entrance slit of the monochromator, while perpendicular to this by an appropriate design of the The cathode system and the lens system between the monochromator and the sample and between the sample and the analyzer are focused on the detector in an approximately parallel beam path without any further intermediate focus. Compared to a free, non-focusing beam spread, this beam guidance offers an improvement.
Eine analoge Art der Fokussierung wird in der US-PS 4 559 449 beschrieben.An analog type of focusing is described in U.S. Patent 4,559,449.
Eine nähere Untersuchung zeigt jedoch, daß eine Reihe entscheidender Nachteile bestehen bleiben. So ist der Winkel des auf den Detektor gelangenden Strahlenbündels senkrecht zur Radialebene klein, wodurch gemäß den Grundsätzen der Optik die Intensität klein bleibt. Ferner ist senkrecht zur Radialebene der Strahlengang an der Probe nahezu parallel.However, closer examination shows that a number of crucial disadvantages remain. So the angle of the beam reaching the detector perpendicular to the radial plane is small, which means according to the principles of optics, the intensity remains small. Furthermore, perpendicular to the radial plane, the beam path on the sample is almost parallel.
Dies bedeutet, daß nur ein kleiner Raumwinkel der gestreuten Elektronen erfaßt wird. Darüber hinaus ist die beschriebene Art der Strahlführung störanfällig für kleine Fehlpotentiale, wie sie bei den häufig verwendeten niedrigen Energien durch Inhomogenitäten der Austrittsarbeiten unvermeidbar sind.This means that only a small solid angle of the scattered electrons is detected. In addition, the described type of beam guidance is susceptible to malfunctions, such as are unavoidable at the frequently used low energies due to inhomogeneities in the work functions.
Der Erfindung liegt daher die Aufgabe zugrunde, eine solche Strahlführung mit fokussierender Energieselektion bzw. ein Elektronenspektrometer vorzusehen, durch das eine hohe Energieauflösung bei hohem Elektronenstrom an der Probe bzw. am Detektor erzielt wird.The invention is therefore based on the object of providing such a beam guide with focusing energy selection or an electron spectrometer, by means of which a high energy resolution with a high electron current is achieved on the sample or on the detector.
Zur Lösung dieser Aufgabe ist das erfindungsgemäße Verfahren der eingangs genannten Art dadurch gekennzeichnet, daß die unterschiedliche Fokussierung der Elektronen in den beiden zueinander senkrechten Richtungen durch ein dem energiedispersiven System nach- oder vorgeschaltetes nicht zirkular symmetrisches Linsensystem derart korrigiert wird, daß entweder die virtuelle oder reelle Eingangsblende des energiedispersiven Systems auf einer vorgegebenen Bildebene außerhalb des energiedispersiven Systems oder eine Probe außerhalb des energiedispersiven Systems auf der virtuellen oder reellen Ausgangsblende desselben abgebildet wird.To achieve this object, the inventive method of the type mentioned is characterized in that the different focusing of the electrons in the two mutually perpendicular directions is corrected by a non-circularly symmetrical lens system connected downstream or upstream of the energy-dispersive system in such a way that either the virtual or the real one Input aperture of the energy dispersive system on a given image level outside of the energy dispersive System or a sample outside the energy-dispersive system on the virtual or real output aperture of the same is mapped.
Die für diesen beschriebenen Zweck einzusetzenden Linsensysteme mit unterschiedlicher Fokussierung in zwei zueinander senkrechten Richtungen werden unter Beachtung der Fokussierungsvorgabe und der Elektronenbahnen im energiedispersiven System gestaltet bzw. dimensioniert. In spezieller Ausgestaltung der Erfindung können rechteckförmige Linsenquerschnittsprofile verwendet werden, bei denen Höhe und Breite so aufeinander abgestimmt sind, daß im Zusammenwirken mit der unterschiedlichen Fokussierung der Elektronen in den zwei zueinander senkrechten Richtungen innerhalb des energiedispersiven Systems die beschriebene Abbildung eintritt. Bei Verwendung von Zylinderkondensatoren als energiedispersive Systeme müssen dann die Symmetrieachsen des Rechteckprofils parallel bzw. senkrecht zur Radialebene sein. Die erforderliche Höhe und Breite der Linsenquerschnittsprofile errechnen sich durch Lösung der Laplace-Gleichung in drei Dimensionen und Berechnung der Elektronenbahnen in drei Dimensionen in der dem Fachmann bekannten Weise.The lens systems to be used for this purpose described with different focusing in two mutually perpendicular directions are designed or dimensioned in consideration of the focus specification and the electron trajectories in the energy-dispersive system. In a special embodiment of the invention, rectangular lens cross-sectional profiles can be used, in which the height and width are matched to one another in such a way that the described image occurs in cooperation with the different focusing of the electrons in the two mutually perpendicular directions within the energy-dispersive system. When using cylindrical capacitors as energy-dispersive systems, the symmetry axes of the rectangular profile must then be parallel or perpendicular to the radial plane. The required height and width of the lens cross-sectional profiles are calculated by solving the Laplace equation in three dimensions and calculating the electron orbits in three dimensions in the manner known to the person skilled in the art.
Zur Korrektur von Bildfehlern, insbesondere des für die Abbildung eines Schlitzes wichtigen Astigmatismusfehlers, hat sich gezeigt, daß es zweckmäßig ist, bei ein oder mehreren Linsenelementen von der Rechteckform abzuweichen und Linsenquerschnittsprofile vorzusehen, bei denen die lichte Weite entlang einer Symmetrieachse eine zum Beispiel trapezförmige oder gestufte oder kurvenförmige Verjüngung aufweist.For the correction of image errors, in particular that important for the imaging of a slot Astigmatism error, it has been shown that it is advisable to deviate from the rectangular shape with one or more lens elements and to provide lens cross-sectional profiles in which the clear width along an axis of symmetry has a trapezoidal or stepped or curved taper, for example.
Zu Vorrichtungen mit erfindungsgemäßer Strahlführung gehören Elektronenmonochromatoren mit nachgeschaltetem korrigierenden Linsensystem zwischen Monochromator und Probe, Analysatoren mit vorgeschaltetem korrigierenden Linsensystem zwischen Probe und Analysator sowie Elektronenstoßspektrometer mit einem solchen Linsensystem zwischen Monochromator und Probe und/oder zwischen Probe und Analysator. Im nachfolgenden wird die Erfindung vornehmlich anhand eines bezüglich Monochromator und Analysator symmetrisch aufgebauten Elektronenstoßspektrometers erläutert. Da ein Elektronenstoßspektrometer, wie beschrieben, aus einem Monochromatorteil mit nachgeschaltetem Linsensystem und einem Analysatorteil mit vorgeschaltetem Linsensystem besteht, kann die Erfindung jedoch auch für den Monochromator mit nachgeschaltetem Linsensystem und den Analysator mit vorgeschaltetem Linsensystem getrennt mit Vorteil für die verschiedenen Anwendungsfälle eingesetzt werden.Devices with beam guidance according to the invention include electron monochromators with a subsequent corrective lens system between the monochromator and sample, analyzers with an upstream corrective lens system between the sample and analyzer, and electron impact spectrometers with such a lens system between the monochromator and sample and / or between the sample and analyzer. In the following, the invention will be explained primarily on the basis of an electron impact spectrometer constructed symmetrically with respect to the monochromator and analyzer. Since an electron impact spectrometer, as described, consists of a monochromator part with a downstream lens system and an analyzer part with a preceding lens system, the invention can, however, also be used separately for the monochromator with a downstream lens system and the analyzer with an upstream lens system for the various applications.
Die unterschiedliche Fokussierung zwischen Monochromator und Probe bzw. Probe und Analysator unterscheidet die erfindungsgemäße Anordnung vom Spektrometer gemäß der US-PS 4 559 449, bei dem an dieser Stelle keine unterschiedliche Fokussierung in beiden Richtungen vorgesehen wird, sondern lediglich eine Auftrennung der Linsen zur Strahlablenkung.The different focus between monochromator and sample or sample and Analyzer distinguishes the arrangement according to the invention from the spectrometer according to US Pat. No. 4,559,449, in which no different focusing is provided in both directions at this point, but only a separation of the lenses for beam deflection.
Statt Zylinderkondensatoren als energiedispersive Systeme im Monochromator und/oder Analysator können auch Plattenkondensatoren verwendet werden, die ebenfalls nur in einer Ebene fokussieren. Es können auch energiedispersive Systeme verwendet werden, die eine unterschiedliche, jeweils von Null verschiedene Fokussierung in zwei zueinander senkrechten Richtungen aufweisen, wobei dann eine entsprechend angepaßte Auslegung des Linsensystems (Auswahl von Höhe und Breite der Linsenprofile) so vorzunehmen ist, daß die gewünschte Fokussierung eintritt.Instead of cylinder capacitors as energy-dispersive systems in the monochromator and / or analyzer, plate capacitors can also be used, which also focus only in one plane. It is also possible to use energy-dispersive systems which have a different, in each case non-zero, focusing in two mutually perpendicular directions, in which case the lens system must be suitably adapted (selection of the height and width of the lens profiles) in such a way that the desired focusing occurs .
Nachfolgend wird die Erfindung anhand eines Ausführungsbeispieles unter Bezugnahme auf die Zeichnungen näher erläutert; es zeigen schematisch:
Figur 1- ein Elektronenstoßspektrometer mit je zwei Monochromatoren und Analysatoren.
Figuren 2 und 3- Querschnittsprofile der Linsenelemente der in
Figur 1 angedeuteten Linsensysteme Figur 4- die Elektronenbahnen zwischen Austrittsspalt des Monochromators und der Probe (a) in der Radialebene und (b) senkrecht dazu, und
Figur 5- ein Schaubild für den Verlauf des monochromatischen Stroms am Detektor in Abhängigkeit von der Energieauflösung mit und ohne erfindungsgemäße Strahlführung.
- Figure 1
- an electron impact spectrometer with two monochromators and analyzers each.
- Figures 2 and 3
- Cross-sectional profiles of the lens elements of the lens systems indicated in FIG. 1
- Figure 4
- the electron paths between the exit slit of the monochromator and the sample (a) in the radial plane and (b) perpendicular thereto, and
- Figure 5
- a diagram for the course of the monochromatic current at the detector depending on the energy resolution with and without the beam guide according to the invention.
Das in Figur 1 gezeigte Elektronenstoßspektrometer umfaßt ein Kathodensystem 1, zwei Monochromatoren 2 und 3, je ein Linsensystem bestehend aus drei Elementen 4, 5 und 6 bzw. 8, 9 und 10 zwischen den Monochromatoren und der Probe 7 sowie zwischen der Probe 7 und den Analysatoren 11 und 12, zwei Analysatoren 11 und 12 und einen Detektor 13. Die beiden Linsensysteme zwischen Monochromator und Probe und zwischen Probe und Analysator sind zueinander symmetrisch, so daß sich die Linsenelemente 4 und 10, 5 und 9 sowie 6 und 8 untereinander gleichen.The electron impact spectrometer shown in Figure 1 comprises a
Die Querschnittsprofile dieser Linsenelemente 4 bis 6 (bzw. 8 bis 10) sind in Figuren 2 und 3 dargestellt: Von diesen ist das Linsenelement 4 trapezförmig bzw. gestuft verjüngt und die Elemente 5 und 6 sind rechteckförmig gestaltet.The cross-sectional profiles of these
Die Höhe und Breite des lichten Profils der Linsenelemente 4, 5 und 6 sind so abgestimmt, daß in der Radialebene (=Zeichenebene in Figur 1) der Ausgangsspalt des Monochromators auf die Probe abgebildet wird (Figur 4a), senkrecht dazu jdoch der Eintrittsspalt (Figur 4b), so daß, im Zusammenwirken mit der Abbildung in der Radialebene durch die Zylinderkondensatoren, in beiden Richtungen ein Bild des Eintrittsspalts des ersten Monochromators an der Probe entsteht. Für diese Wirkungsweise ist es wesentlich, daß zwischen dem ersten und zweiten Monochromator keine Linsenelemente existieren. Vielmehr wird die geforderte Abbildung auf die Probe ausschließblich durch das Linsensystem 4 bis 6 im Zusammenwirken mit den Monochromatoren erzielt. In gleicher Weise sind Höhe und Breite der Profile der Linsenelemente 8, 9 und 10 so abgestimmt, daß in der Radialebene die Probe auf den Eintrittsspalt des ersten Analysators, senkrecht dazu die Probe auf den Austrittsspalt des letzten Analysators abgebildet wird, so daß insgesamt ein Bild der Probe am Austrittsspalt des zweiten Analysators entsteht.The height and width of the clear profile of the
Der mit Verwendung des erfindungsgemäßen Linsensystems erzielte monochromatische Strom, gemessen am Detektor, als Funktion der Auflösung ist aus Figur 5, Kurve a ersichtlich. Im Vergleich dazu zeigt Kurve b analoge Werte für ein Spektrometer, welches das erfindungsgemäße Linsensystem nicht aufweist, ansonsten aber bezüglich der Monochromatoren und Analysatoren baugleich ist. Die Ergebnisse beziehen sich auf eine Elektronenenergie an der Probe von 100 eV, während die Energie der Elektronen in den Monochromatoren und Analysatoren (je nach Auflösung) unter 1 eV liegt.The monochromatic current achieved using the lens system according to the invention, measured on the detector, as a function of the resolution is shown in FIG. 5, curve a. In comparison, curve b shows analog values for a spectrometer which does not have the lens system according to the invention, but is otherwise identical in terms of monochromators and analyzers. The results refer to one Electron energy on the sample of 100 eV, while the energy of the electrons in the monochromators and analyzers (depending on the resolution) is less than 1 eV.
Claims (9)
- Process for electron beam guidance with focusing energy selection in an energy-dispersive system with differing focusing in two mutually perpendicular directions, characterised in that the differing focusing of the electrons in the two mutually perpendicular directions is corrected by a non-circularly-symmetrical lens system situated downstream or upstream of the energy-dispersive system, in such a manner that either the virtual or real entrance diaphragm of the energy-dispersive system is imaged on a predetermined image plane outside the energy-dispersive system, or a specimen is imaged outside the energy-dispersive system on the virtual or real exit diaphragm thereof.
- Process according to Claim 1, characterised in that lens systems having a rectangular, especially tapered-rectangular cross sectional profile of the lenses are used.
- Electron spectrometer having an emission system and having at least one energy-dispersive system with differing focusing in two mutually perpendicular directions, characterised by a lens system (4-6), situated downstream of an energy-dispersive system (2, 3) for energy selection in front of the specimen (7), with non-circular focusing differing in the two mutually perpendicular directions, which lens system in conjunction with the focusing properties of the energy-dispersive system, generates an image of the virtual or real entrance diaphragm of the energy-dispersive system (2, 3) at the specimen location and/or a lens system (8-10), situated upstream of an energy-dispersive system (11, 12) for energy selection behind a specimen (7), with non-circular focusing differing in the two mutually perpendicular directions, which lens system, in conjunction with the focusing properties of the energy-dispersive system, images the image at the specimen location onto a virtual or real exit diaphragm of the energy-dispersive system (11, 12).
- Electron spectrometer according to Claim 3, characterised in that the energy-dispersive system (2, 3) in front of the specimen (7) and/or the energy-dispersive system (11, 12) behind the specimen (7) focuses only in one direction.
- Electron spectrometer according to Claim 3 or 4, characterised in that one or more clear lens cross sectional profiles of the lens element (4-6 or 8-10) have a non-circular design.
- Electron spectrometer according to Claim 5, characterised in that one or more clear lens cross sectional profiles are rectangular.
- Electron spectrometer according to Claim 5, characterised in that one or more clear cross sectional profiles of the lens elements exhibit a trapezoidal, stepped or curved taper along one axis.
- Electron spectrometer according to one of Claims 3 to 7, characterised in that the energy-dispersive system (2, 3) for energy selection in front of the specimen is formed by a first and an immediately following second monochromator.
- Electron spectrometer according to one of Claims 3 to 8, characterised in that the energy-dispersive systems are formed by cylindrical condensers.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19873702696 DE3702696A1 (en) | 1987-01-30 | 1987-01-30 | METHOD FOR ELECTRON BEAM GUIDANCE WITH ENERGY SELECTION AND ELECTRON SPECTROMETER |
| DE3702696 | 1987-01-30 |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| EP0276731A2 EP0276731A2 (en) | 1988-08-03 |
| EP0276731A3 EP0276731A3 (en) | 1990-01-24 |
| EP0276731B1 true EP0276731B1 (en) | 1993-03-10 |
Family
ID=6319818
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP88100724A Expired - Lifetime EP0276731B1 (en) | 1987-01-30 | 1988-01-20 | Method for electron beam guidance with energy selection, and electron spectrometer |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US4845361A (en) |
| EP (1) | EP0276731B1 (en) |
| JP (1) | JP2529712B2 (en) |
| DE (2) | DE3702696A1 (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE69027602T2 (en) * | 1990-08-08 | 1997-01-23 | Philips Electronics Nv | Energy filter for charge carrier device |
| JP2636113B2 (en) * | 1992-03-26 | 1997-07-30 | 広島大学長 | Bandpass filter type inverse photoelectron spectroscopy detector |
| US5466933A (en) * | 1992-11-23 | 1995-11-14 | Surface Interface, Inc. | Dual electron analyzer |
| DE19633496B4 (en) * | 1996-08-20 | 2006-06-08 | Ceos Corrected Electron Optical Systems Gmbh | Monochromator for electron optics, in particular electron microscopy |
| EP1139091B1 (en) * | 2000-03-27 | 2009-08-19 | ELLCIE Maintenance GmbH | Electron spectrometer with deflection unit |
| KR20060088272A (en) * | 2005-02-01 | 2006-08-04 | 삼성전자주식회사 | X-ray photoelectron spectroscopy |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2856244A1 (en) * | 1978-12-27 | 1980-07-03 | Kernforschungsanlage Juelich | ELECTRONIC SHOCK SPECTROMETER |
| US4559449A (en) * | 1984-05-23 | 1985-12-17 | Indiana University Foundation | High resolution particle spectrometer |
| US4742223A (en) * | 1984-05-23 | 1988-05-03 | Indiana University Foundation | High resolution particle spectrometer |
-
1987
- 1987-01-30 DE DE19873702696 patent/DE3702696A1/en not_active Withdrawn
-
1988
- 1988-01-20 EP EP88100724A patent/EP0276731B1/en not_active Expired - Lifetime
- 1988-01-20 DE DE8888100724T patent/DE3878939D1/en not_active Expired - Lifetime
- 1988-01-27 JP JP63014812A patent/JP2529712B2/en not_active Expired - Lifetime
- 1988-01-28 US US07/149,596 patent/US4845361A/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| DE3878939D1 (en) | 1993-04-15 |
| EP0276731A3 (en) | 1990-01-24 |
| EP0276731A2 (en) | 1988-08-03 |
| DE3702696A1 (en) | 1988-08-11 |
| JPS63276861A (en) | 1988-11-15 |
| JP2529712B2 (en) | 1996-09-04 |
| US4845361A (en) | 1989-07-04 |
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