EP0465695B1 - Analysator für geladene Teilchen mit sphärischer Elektrode - Google Patents

Analysator für geladene Teilchen mit sphärischer Elektrode Download PDF

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Publication number
EP0465695B1
EP0465695B1 EP19900113101 EP90113101A EP0465695B1 EP 0465695 B1 EP0465695 B1 EP 0465695B1 EP 19900113101 EP19900113101 EP 19900113101 EP 90113101 A EP90113101 A EP 90113101A EP 0465695 B1 EP0465695 B1 EP 0465695B1
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EP
European Patent Office
Prior art keywords
spherical
energy
charged particles
grid
exit opening
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP19900113101
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English (en)
French (fr)
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EP0465695A1 (de
Inventor
Hiroshi Daimon
Shozo Ino
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Shimadzu Corp
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Shimadzu Corp
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Publication date
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Priority to DE1990628700 priority Critical patent/DE69028700T2/de
Priority to EP19900113101 priority patent/EP0465695B1/de
Publication of EP0465695A1 publication Critical patent/EP0465695A1/de
Application granted granted Critical
Publication of EP0465695B1 publication Critical patent/EP0465695B1/de
Anticipated expiration legal-status Critical
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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
    • H01J49/484—Static spectrometers using electrostatic analysers, e.g. cylindrical sector, Wien filter with spherical mirrors

Definitions

  • the present invention relates to an analyzer for analyzing the composition, structure, or electronic condition of a sample by measuring the kinetic energy of charged particles emitted from the sample and the angular distribution of the particles, and more particularly, to such an analyzer suitable for measuring the energy distribution of the charged particles emitted from the sample or the angular distribution of charged particles of particular energy to be noted from the surface of the sample in a two-dimensional manner.
  • a part-spherical electrode 2 Concentric with the part-spherical grid 1, a part-spherical electrode 2 is disposed.
  • a sample S is positioned within the part-spherical grid 1 and far from the spherical center of the part-spherical grid 1.
  • a screen plate 3 is provided having an opening A symmetric with the sample S, with respect to the center of the part-spherical grid 1.
  • a two-dimensional detector 4 is positioned within a space opposed to the part-spherical grid 1 as to the screen plate 3 and faced to the opening A.
  • a suitable voltage is applied between the part-spherical grid 1 and the part-spherical electrode 2, then no electric field appears within the bottom space of the part-spherical grid 1.
  • the sample S When an excitation beam is incident on the sample S, the sample S emits charged particles.
  • the emitted charged particles linearly travel at the bottom space of the part-spherical grid 1 from the incident portion of the exciting beam. They fly an elliptical orbit having one focus at 0 within the space between the part-spherical grid 1 and the part-spherical electrode 2.
  • Some charged particles with too high energy are eliminated by being struck with the part-spherical electrode 2.
  • Some charged particles with lower energy can return to the bottom space of the part-spherical grid 1.
  • Some charged particles having particular energy defined by a voltage applied between the part-spherical grid 1 and the part-spherical electrode 2 can transit through the opening A in the direction parallel with the direction of the emission of the charged particles from the sample S.
  • the output pictures of the two-dimensional detector 4 represent the angular distribution of the charged particles with the particular energy.
  • the particular energy can be selected by the voltage applied between the part-spherical grid 1 and the part-spherical electrode 2.
  • the above-described analyzer can measure the angular distribution of the charged particles having the particular energy among the charged particles emitted from the excited portion on the surface of the sample S.
  • the part-spherical grid 1 and the part-spherical electrode 2 do not conform any low pass filter.
  • no energy filter is provided by which all of the charged particles having energy more than particular energy Ec are introduced into the part-spherical electrode 2 and all of the charged particles having enery less than Ec are reflected.
  • the charged particles with the particular energy can be gathered into the opening A and transit it while the charged particles with the other energy are scattered over the screen plate 3 not to transit it. The selection of the charged particles in terms of the energy is done in this manner.
  • the resolution of the energy depends upon the position of the sample, from which the charged particles are emitted, the position and the largeness of the opening A.
  • the transmittance of the charged particles with various kinetic energies through the opening A is calculated as a function of a deviation of energy as to the particular energy Eo ( ⁇ E/Eo), which results are shown in FIG. 6.
  • the numerals in the graph of FIG. 6 represent 10 times a ratio of a distance s from the center O of the sample S and the opening A as compared to the radius a of the part-spherical grid 1, namely, 10 ⁇ s/a.
  • the transmittance shows that the analyzer is a low-pass filter.
  • the transmittance curve is symmetric.
  • the half value width of the transmittance is narrow.
  • the resolution is about 1 %, which is approximate to the resolution of the conventional spectrometer.
  • the disadvantage of this spectrometer is that the resolution is not uniform about the emission angle of the charged particles from the sample.
  • the resolution at some angular region is better than the average value, and at some region it is worse than the average value.
  • the resolution is the worst as illustrated by the broken line of FIG. 4.
  • the abscissa is the emission angle ⁇ and the ordinate is a deviation of energy (%) from the energy (Eo) to be analyzed.
  • the plotted data represent the energy of the charged particle having about one half of the transmittance.
  • the S/N ratio is too bad to observe the pictures.
  • both sides cannot reach zero promptly due to the poor resolution at this angular range.
  • the orbit of the charged particles collides with the outer spherical electrode 2, so that the resolution at the high energy side becomes good.
  • FIG. 1 shows a preferred embodiment of a part-spherical electrode type charged particle analyzer of the present invention.
  • a part-spherical grid 1 and a part-spherical electrode 2 are concentric having a common center of O.
  • the radius of the part-spherical electrode 2 is twice the radius of the part-spherical grid 1.
  • the solid angle of detection is 2 ⁇ steradian, which is the whole emission angle from sample surface.
  • Guard rings 5 are provided between the edges of the grid 1 and the electrode 2. They are arranged in the concentric manner and connected to the resistor 6 as illustrated. One side of the resistor 6 is connected to the grid 1 and is also grounded.
  • the other side of the resistor 6 is connected to the eletrode 2 and is also connected to the power supply 7.
  • the guard rings 5 are provided for preventing the electric field between the grid 1 and the electrode 2 from being disturbed at the edges of the grid 1 and the electrode 2.
  • a screen plate 3 is positioned at the bottom of the grid 1, being made of an electrically conductive material and grounded. With the above-described structure, the energy of charged particles to be detected can be scanned by changing the output voltage of the power supply 7.
  • the screen plate 3 has an entry window W, separated by a distance slightly smaller than the radius of the grid 1 from the center O, for setting a sample S.
  • the screen plate 3 has an exit opening symmetrical with the position of the entry window W with respect to the center O.
  • Apertures h 1 and h 2 are bored in the grid 1 and the electrode 2, respectively, through which exciting beams such as X-rays for exciting the sample S are incident on the sample S.
  • An electron gun 11 is positioned at a space between the grid 1 and the screen plate 3 for emitting electron beams to the sample S.
  • the sample S can be excited with the X-rays or the electron beams.
  • a two-dimensional detector 4 is positioned below the screen plate 3 and faced against the exit opening A.
  • the two-dimensional detector 4 composed of microchannel plates and a fluorescent plate. The light emitted from the fluorescent plate is detected with a two-dimensional photomultiplier Ph, so that the output is processed with a computer Cp to calculate the emission points on the fluorescent plate.
  • the angular distribution of the charged particles emitted from the sample S and having the characteristic energy as defined by the voltage applied between the electrode 2 and the grid 1 is represented.
  • Four-fold part-spherical grids 8, 81, 91, and 9 are provided between the exit opening A and the two-dimensional detector 4. They are concentric with the center of the exit opening A.
  • the potential of the innermost grid 8 is the same as that of the screen plate 3.
  • the grids 81 and 91 are set to a slightly lower voltage than the energy of the charged particles to be detected, so that the charged particle having energy lower than the specific energy to be detected are blocked.
  • the voltage of the outermost grid 9 is set, so that the charged particles being incident upon the two-dimensional detector 4 are accelerated.
  • An obstacle plate 10 is a ring-segment-like plate which is axially symmetric around the axis OA, and positioned in an equatorial plane passing through the spherical center O of the spherical electrode 2 and normal to the axis OA.
  • the obstacle plate 10 is isolated from the electrode 2 and is set to a voltage identical with the normal potential between the grid 1 and the electrode 2 at the internal peripheral edges.
  • the potential adjacent the portion where the obstacle plate 10 penetrates the electrode 2 is disturbed, but the potentials within the electrode 2 as a whole are not disturbed.
  • the orbits of the charged particles are not changed as compared to the case without the obstacle plate 10.
  • the charged particles having the energy higher than the particular energy among the charged particles emitted from the sample S in the normal direction are obstructed by the obstacle plate 10.
  • the orbits of the charged particles finally going into the exit opening A are the same regardless of setting the particular energy, as shown in FIG. 1. Then the inner radius of the obstacle plate 10 can be fixed while the applied voltage should be changed in proportional to the voltage applied to the electrode 2.
  • FIG. 2 shows a more efficient shape of the obstacle plate 10, in which the obstacle plate 10 is shaped a partial sphere having an angle of 2 ⁇ around the center O of the electrode 2.
  • FIG. 4 shows a graph of the energy resolution according to the emission direction of the charged particles when the obstacle plate of FIG. 2 is applied.
  • the broken line of FIG. 4 indicates the resolution data without the obstacle plate 10.
  • the maximum point of the resolution appears around 80° (10° inclination from the normal) and there is a small problem relating to the uniformity of resolution. This maximum point of the resolution is due to the effect at the edges of the obstacle plate 10.
  • FIG. 5 shows a graph of using six obstacle rings-segments to make the resolution approximately uniform.
  • the large dip B of FIG. 4 can be eliminated and 6 small dips are present, so that approximately uniform resolution can be given.
  • the envelope plane of the orbits of the charged particles with the specific energy emitted from the emission point of the sample into the exit opening A is not a sphere having the center O of the electrode 2, but a shape of which the center is vertically displaced downward compared to the sphere. Therefore, the orbits of the charged particles having more energy than the specific energy are out of that envelope plane.
  • the energy resolution of such a charged particle is the lowest as shown in the broken line of FIG. 4.
  • the charged particles having the energy more than the particular energy are obstructed by colliding with the obstacle plate 10, so that they cannot pass through the exit opening A.
  • the interruption energy of high-pass filter of the part-spherical grids positioned below the exit opening A is set slightly lower than the above particular energy, the charged particles having the energy lower than the particular energy, which cannot be removed by the obstacle plate, can be removed.
  • the energy resolution of the charged particles in this direction can be improved, so that the energy resolution is uniform in all directions.

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Electron Tubes For Measurement (AREA)

Claims (3)

  1. Analysator für geladene Teilchen, mit:
    einem teil-sphärischen Gitter (1),
    einer teil-sphärischen Elektrode (2), die außerhalb von und konzentrisch zu dem teil-sphärischen Gitter angeordnet ist,
    einem Eintrittsfenster (W) für die geladenen Teilchen, welches Eintrittsfenster in einer Platte (3) ausgebildet und in einer Ebene angeordnet ist, die durch das Kugelzentrum (O) des teil-sphärischen Gitters verläuft,
    einer Austrittsöffnung (A), die in dieser Platte ausgebildet und in bezug auf das Kugelzentrum des teil-sphärischen Gitters symmetrisch zu der Position des Eintrittsfensters angeordnet ist, und
    einem Detektor (4), der auf der dem teil-sphärischen Gitter entgegengesetzten Seite der Austrittsöffnung (A) angeordnet und der Austrittsöffnung zugewandt ist,
    gekennzeichnet durch
    mehrere zweite teil-sphärische Gitter (8, 81, 91, 9), die in einer Position zwischen der Austrittsöffnung und dem Detektor (4) um das Zentrum der Austrittsöffnung (A) herum angeordnet sind, welche mehreren teil-sphärischen Gitter ein Hochpaßfilter für die geladenen Teilchen bilden, und
    eine gekrümmte Hindernisplatte (10), die innerhalb der teil-sphärischen Elektrode (2) angeordnet und axialsymmetrisch in bezug auf eine Achse (OA) ist, die durch das Kugelzentrum (O) der teil-sphärischen Elektrode und durch die Austrittsöffnung (A) verläuft, welche Hindernisplatte parallel zu einer durch das Kugelzentrum (O) verlaufenden Äquatorebene angeordnet ist,
    wobei die Hindernisplatte (10) dazu eingerichtet ist, den Eintritt von geladenen Teilchen mit einer Energie oberhalb einer bestimmten Energie (E0) in die Austrittsöffnung (A) zu verhindern, und die mehreren zweiten teil-sphärischen Gitter eine Sperrenergie etwas unterhalb dieser bestimmten Energie haben und dazu dienen, die geladenen Teilchen zu entfernen, deren Energie kleiner als die bestimmte Energie ist.
  2. Analysator für geladene Teilchen nach Anspruch 1, bei dem die Hindernisplatte als ein Kugelsegment geformt ist, das zu der teil-sphärischen Elektrode (2) konzentrisch ist.
  3. Analysator für geladene Teilchen nach Anspruch 1, bei dem die Hindernisplatte (10) in mehrere Ringsegmente aufgeteilt ist, die in unterschiedlichen Radien (r1-r6) um das Kugelzentrum (O) der teil-sphärischen Elektrode herum angeordnet und um unterschiedliche Winkel (α1-α6) gegenüber der genannten Äquatorialebene versetzt sind.
EP19900113101 1990-07-09 1990-07-09 Analysator für geladene Teilchen mit sphärischer Elektrode Expired - Lifetime EP0465695B1 (de)

Priority Applications (2)

Application Number Priority Date Filing Date Title
DE1990628700 DE69028700T2 (de) 1990-07-09 1990-07-09 Analysator für geladene Teilchen mit sphärischer Elektrode
EP19900113101 EP0465695B1 (de) 1990-07-09 1990-07-09 Analysator für geladene Teilchen mit sphärischer Elektrode

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP19900113101 EP0465695B1 (de) 1990-07-09 1990-07-09 Analysator für geladene Teilchen mit sphärischer Elektrode

Publications (2)

Publication Number Publication Date
EP0465695A1 EP0465695A1 (de) 1992-01-15
EP0465695B1 true EP0465695B1 (de) 1996-09-25

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EP19900113101 Expired - Lifetime EP0465695B1 (de) 1990-07-09 1990-07-09 Analysator für geladene Teilchen mit sphärischer Elektrode

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DE (1) DE69028700T2 (de)

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63126148A (ja) * 1986-11-14 1988-05-30 Hiroshi Daimon 荷電粒子アナライザ−

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DE69028700D1 (de) 1996-10-31
DE69028700T2 (de) 1997-04-30
EP0465695A1 (de) 1992-01-15

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