Electron Optics of a Scanning Electron Microscope

  • Ludwig Reimer
Part of the Springer Series in Optical Sciences book series (SSOS, volume 45)


The purpose of the electron optics of a SEM is to produce a small electron probe at the specimen by demagnifying the crossover, the smallest cross-section of the electron beam near the cathode. For the practical application of a SEM, it must be possible to vary the electron-probe size, aperture and current but this cannot, however, be done independently because these quantities are related by the gun brightness. A geometric optical theory of electron-probe formation can be employed when using a thermionic cathode but for a field-emission gun a wave-optical theory is necessary. Electron-beam deflection by transverse electrostatic and magnetic fields is incorporated for scanning the electron probe across the specimen, for tilting the direction of the incident electron beam for stereo-viewing and for recording electron channelling patterns. Deflection systems are further used for the blanking or chopping of the electron beam up to gigahertz frequencies for stroboscopic modes and time-resolved signals. Due to the large depth of focus, focusing of SEM images raises no problems but the resolution is limited by the electron-probe size and the compensation of the final lens astigmatism.


Deflection Angle Electron Optic Spherical Aberration Probe Diameter Condenser Lens 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. 2.1
    M.E. Haine, P.A. Einstein: Characteristics of the hot cathode electron microscope gun. Brit.J.Appl.Phys. 3, 40 (1952) 2.2 A.N. Broers: Electron gun using long-life LaB6 cathode. J.Appl.Phys. 38, 1991 (1967)Google Scholar
  2. 2.2
    A.N. Broers: Electron gun using long-life LaB6 cathode. J.Appl.Phys. 38, 1991 (1967)Google Scholar
  3. 2.3
    A.N. Broers: Some experimental and estimated characteristics of the LaB6 rod cathode electron gun. J.Phys.E 2, 273 (1969)ADSCrossRefGoogle Scholar
  4. 2.4
    S.F. Vogel: Pyrolythic graphite in the design of a compact inert heater of a LaB6 cathode. Rev.Sci.Instr. 41, 585 (1970)ADSCrossRefGoogle Scholar
  5. 2.5
    R. Vogt: Richtstrahlwert und Energieverteilung der Elektronen aus einem Elektronenstrahlerzeuger mit LaB6-Kathode. Optik 36, 262 (1972)Google Scholar
  6. 2.6
    S.D. Ferris, D.C. Joy, H.J. Leamy, C.K. Crawford: A directly heated LaB6 electron source. SEM 1975, p. 11Google Scholar
  7. 2.7
    S. Nakagawa, T. Yanaka: A highly stable electron probe obtained with LaB6 cathode electron gun. SEM 1975, p. 19Google Scholar
  8. 2.8
    C.K. Crawford: Mounting methods and operating characteristics for LaB6 cathodes. SEM 1979/I, p.19Google Scholar
  9. 2.9
    J.A. Swift, A.C. Brown: SEM electron source: pointed tungsten filaments with long-life and high brightness. Scanning 2, 42 (1979)CrossRefGoogle Scholar
  10. 2.10
    P.H. Schmidt, D.C. Joy, L.D. Longinotti, H.J. Leamy, S.D. Ferris, Z. Fisk: Anisotropy of thermionic electron emission values for LaB6 single-crystal emitter cathodes. Appl.Phys.Lett. 29, 400 (1976)ADSCrossRefGoogle Scholar
  11. 2.11
    R. Shimizu, T. Shinike, T. Tanaka, C. Oshima, S. Kawai, H. Hiraoka, H. Hagiwara: Brightness of single crystal LaB6 of 100 and 110 orientations. SEM 1979/I, p.11Google Scholar
  12. 2.12
    J.D. Verhoeven: On the problem of obtaining optimum brightness from your LaB6 gun. SEM 1977/I, p.581Google Scholar
  13. 2.13
    P.B. Sewell: High brightness thermionic electron guns for electron microscopes. SEM 1980/I, p.11Google Scholar
  14. 2.14
    H. Hagiwara, H. Hiraoka, R. Terasaki, M. Ishii, R. Shimizu: Crystallographical and geometrical effects on thermionic emission change of single crystal LaB6 cathodes. SEM 1982/II, p.473Google Scholar
  15. 2.15
    H. Boersch: Experimentelle Bestimmung der Energieverteilung in thermisch ausgelösten Elektronenstrahlen. Z.Phys. 139, 115 (1954)ADSCrossRefGoogle Scholar
  16. 2.16
    K.H. Loeffler: Energy-spread generation in electron-optical instruments. Z.angew.Phys. 27, 145 (1969)Google Scholar
  17. 2.17
    H. Rose, R. Spehr: On the theory of the Boersch effect. Optik 57, 339 (1980)Google Scholar
  18. 2.18
    D.B. Langmuir: Theoretical limitations of cathode ray tubes. Proc. IRE 25, 977 (1937) J. Dosse: Theoretische und experimentelle Untersuchungen Ober Elektronenstrahler. Z.Phys. 115, 530 (1940)Google Scholar
  19. 2.19
    L. Reimer: Transmission Electron Microscopy, Physics of Image Formation and Microanalysis, Springer Ser. Opt. Sci., Vol. 36 ( Springer, Berlin, Heidelberg 1984 )Google Scholar
  20. 2.20
    J.F. Hainfeld: Understanding and using field emission sources. SEM 1977/I, p.591Google Scholar
  21. 2.21
    A.N. Broers: Electron sources for scanning electron microscopy. SEM 1975, p. 661Google Scholar
  22. 2.22
    L. Reimer, B. Volbert, P. Bracker: STEM semiconductor detector for testing SEM quality parameters. Scanning 2, 96 (1979)CrossRefGoogle Scholar
  23. 2.23
    P.B. Sewell, K.N. Ramachandran: A source imaging detector for the SEM. SEM 1977/I, p.17Google Scholar
  24. 2.24
    C. Wells: Experimental method for measuring the electron-optical parameters of the SEM. SEM 1977/I, p.25Google Scholar
  25. 2.25
    W. Glaser: Grundlagen der Elektronenoptik ( Springer, Wien 1952 )zbMATHGoogle Scholar
  26. 2.26
    T. Mulvey: Unconventional lens design. In Magnetic Electron Lenses, P.W. Hawkes, Topics Current Phys. Vol. 18 ( Springer, Berlin, Heidelberg 1982 ) p. 359Google Scholar
  27. 2.27
    R. Hill, K.C.A. Smith: The single-pole lens as a SEM objective. SEM 1982/II, p.465Google Scholar
  28. 2.28
    V.E. Cosslett: Probe size and probe current in the STEM. Optik 36, 85 (1972)Google Scholar
  29. 2.29
    W. Glaser: Strenge Berechnung magnetischer Linsen der Feldform H =H0/[1+(z/a)2]. Z.Phys. 117, 285 (1941)ADSzbMATHCrossRefMathSciNetGoogle Scholar
  30. 2.30
    R.L. Barnes, I.K. Openshaw: A comparison of experimental and theoretical C values for some probe-forming lenses. J.Phys.E 1, 628 (1968)ADSCrossRefGoogle Scholar
  31. 2.31
    S. Nakagawa: A method for measuring the spherical and chromatic aberration coefficients of an objective lens. SEM 1977/I, p.33Google Scholar
  32. 2.32
    O. Scherzer: The theoretical resolution limit of the electron microscope. J.Appl.Phys. 20, 20 (1949)Google Scholar
  33. 2.33
    C.W. Oatley, W.C. Nixon, R.F.W. Pease: Scanning electron microscopy. Adv.Electr.Electron Phys. 21, 181 (1965)CrossRefGoogle Scholar
  34. 2.34
    P. Gentsch, P. Hagemann, L. Reimer: Comparison of the resolution using a 100 keV electron microscope in the conventional mode and with a scanning device. In Electron Microscopy 1974, Vol. 1, ed. by J.V. Sanders and D.J. Goodchild ( Australian Acad.Sci., Canberra 1974 ) p. 256Google Scholar
  35. 2.35
    V.E. Cosslett, M.E. Haine: The tungsten point cathode as an electron source. In Proc. 3rd Internat. Conf. Electron Microscopy, ed. R. Ross ( Royal Micr. Soc., London 1954 ) p. 639Google Scholar
  36. 2.36
    J.R.A. Cleaver, K.C.A. Smith: Two-lens probe forming system employing field emission guns. SEM 1973, p. 49Google Scholar
  37. 2.37
    C. Colliex, C. Mory: Quantitative aspects of STEM. In Quantitative Electron Microscopy, ed. by J.N. Chapman and A.J. Craven ( Scottish Univ. Summer School in Physics, Edinburgh 1984 ) p. 149Google Scholar
  38. 2.38
    H. Hantsche: Entwicklung einer verbesserten Sondenstromstabilisierung für Rasterelektronenmikroskope. Scanning 2, 20 (1979)CrossRefGoogle Scholar
  39. 2.39
    S.J.B. Reed: Probe current stability in electron-probe microanalysis. J.Phys.E 1, 136 (1968)ADSCrossRefGoogle Scholar
  40. 2.40
    H.F. Wellenstein, R.E. Ensman: A regulated filament temperature power supply for electron guns. Rev.Sci.Instr. 44, 922 (1973)ADSCrossRefGoogle Scholar
  41. 2.41
    J. Arndt, H. Hantsche, D. Schmidt: A simple beam current stabi-lizing unit for SEMs, Scanning 1, 125 (1978)CrossRefGoogle Scholar
  42. 2.42
    L.J. Balk, K. Elbern, E. Kubalek: Elektronische Zusätze zum Rasterelektronenmikroskop. BEDO 8, 313 (1975)Google Scholar
  43. 2.43
    J.R.A. Cleaver, K.C.A. Smith: Optical characteristics of a field emission scanning microscope. In Scanning Electron Microscopy: systems and applications (Inst. of Physics, London 1973 ) p. 6Google Scholar
  44. 2.44
    R. ChristenhuB, G. Pfefferkorn: Bild-Drehung und -Verzerrung beim Raster-Elektronenmikroskop Stereoscan. BEDO 1, 129 (1968)Google Scholar
  45. 2.45
    A. Higgs: A digital rotating system. J.Phys.E. 15, 266 (1982)ADSCrossRefGoogle Scholar
  46. 2.46
    A. Boyde: Quantitative photogrammetric analysis and qualitative stereoscopic analysis of SEM images. J.Micr. 98, 452 (1973)CrossRefGoogle Scholar
  47. 2.47
    P.G.T. Howell: The derivation of working formulae for SEM photo-grammetry. Scanning 1, 230 (1978)CrossRefGoogle Scholar
  48. 2.48
    A.R. Dinnis: After-lens deflection and its uses. SEM 1971, p.41; Limiting factors in direct stereoviewing. In Scanning Electron Microscopy: systems and applications (Inst. of Physics, London 1973 ) p. 76Google Scholar
  49. 2.49
    A. Boyde: A stereo-plotting device for SEM micrographs; and a real time 3-D system for the SEM. SEM 1974, p. 93Google Scholar
  50. 2.50
    E.J. Chatfield, J. More, V.H. Nielsen: Stereoscopic SEM at T.V. scan rates. SEM 1974, p. 117Google Scholar
  51. 2.51
    J.B. Pawley: Design and performance of presently available TV-rate stereo SEM systems. SEM 1978/I, p.157Google Scholar
  52. 2.52
    W. Bröcker, G. Hauck, H. Weigelt, G. Pfefferkorn: Lock-in technique applied to cathodoluminescence of biological specimens in the SEM. Scanning 4, 165 (1981)CrossRefGoogle Scholar
  53. 2.53
    L.J. Balk, E. Kubalek: Use of phase sensitive-(lock-in)-amplification with scanning electron microscope. BEDO 6, 551 (1973)Google Scholar
  54. 2.54
    A.E. Lukianov, G.V. Spivak: Electron mirror microscopy of transient phenomena in semiconductor diodes. In Electron Microscopy 1966, Vol.I, R. Uyeda ( Maruzen, Tokyo 1966 ) p. 611Google Scholar
  55. 2.55
    I. Szentesi: Stroboscopic electron mirror microscopy at frequencies up to 100 MHz. J.Phys. E 5, 563 (1972)Google Scholar
  56. 2.56
    M. Weinfeld, A. Bouchoule: Electron gun for generation of subnanosecond electron packets at very high repetition rates. Rev.Sci.Instr. 47, 412 (1976)ADSCrossRefGoogle Scholar
  57. 2.57
    S.M. Davidson: Wehnelt modulation beam blanking in the SEM. In Electron Microscopy and Analysis 1981, ed. by M.J. Goringe ( Inst. of Physics, Bristol 1982 ) p. 39Google Scholar
  58. 2.58
    R. Schief, M. Steiner: Energieverbreiterung eines durch hochfrequente Wehneltspannung gepulsten Elektronenstrahls. Optik 38, 261 (1973)Google Scholar
  59. 2.59
    A.J. Gonzales, M.W. Powell: Internal waveform measurements of the MOS three transistor, dynamic RAM using SEM stroboscopic techniques. Techn. Digest of IEDM, IEEE, New York 1975, p. 119Google Scholar
  60. 2.60
    G.S. Plows, W.C. Nixon: Stroboscopic SEM. J.Phys.E 1,595 (1968)Google Scholar
  61. 2.61
    E. Menzel, E. Kubalek: Electron beam chopping system in the SEM. SEM 1979/I, p.305Google Scholar
  62. 2.62
    A. Gopinath, M.S. Hill: SEM stroboscopy at 9 GHz. SEM 1973, p.197Google Scholar
  63. 2.63
    G.Y. Robinson: Stroboscopic SEM at GHz frequencies. Rev.Sci.Instr. 42, 251 (1971)Google Scholar
  64. 2.64
    K. Ura, H. Fujioka, T. Hosokawa: Electron optical design of picosecond pulse stroboscopic SEM. SEM 1978/I, p.747Google Scholar
  65. 2.65
    T. Hosokawa, H. Fujioka, K. Ura: Generation and measurement of subpicosecond electron beam pulses. Rev.Sci.Instr. 49, 624 (1978)Google Scholar
  66. 2.66
    A. Gopinath, M.S. Hill: Deflection beam chopping in the SEM. J.Phys. E 10, 229 (1977)Google Scholar
  67. 2.67
    J. Stabenow: Herstellung dünnwandiger Objektivaperturblenden für die Elektronenmikroskopie. Naturwiss. 54, 163 (1967)ADSCrossRefGoogle Scholar
  68. 2.68
    E. Schablach: A method for the fabrication of thin foil apertures for electron microscopy. J.Micr. 101, 121 (1974)CrossRefGoogle Scholar
  69. 2.69
    J.P. Martin, R. Speidel: Zur Verwendung von Dünnschicht-Apertur- blenden im Elektronen-Rastermikroskop. BEDO 4/2, 345 (1971)Google Scholar
  70. 2.70
    N.C. Yew: Dynamic focusing technique for tilted samples in SEM.SEM 1971, p. 33Google Scholar
  71. 2.71
    J. Hersener, Th. Ricker: Eine automatische Fokussierungseinrichtung für Rasterelektronenmikroskope. BEDO 5, 377 (1972)Google Scholar
  72. 2.72
    S. Shirai, A. Onoguchi, T. Ichinogawa: An automatic focusing system for the SEM. In Proc. 6th Int. Conf. on t-Ray Optics and Microanalysis, ed. by G. Shinoda et al. ( Univ. Tokyo Press, Tokyo 1972 ) p. 511Google Scholar
  73. 2.73
    W.J. Tee, K.C.A. Smith, D.M. Holburn: An automatic focusing and stigmating system for the SEM. J.Phys. E 12, 35 (1979)Google Scholar
  74. 2.74
    S.J. Erasmus, K.C.A. Smith: An automatic focusing and astigmatism correction system for the SEM and CTEM. J.Micr. 127, 105 (1982)CrossRefGoogle Scholar
  75. 2.75
    R.F.W. Pease, W.C. Nixon: High resolution SEM. J.Sci.Instr. 42, 81 (1965)ADSCrossRefGoogle Scholar
  76. 2.76
    A.N. Broers: A new high resolution reflection SEM. Rev.Sci.Instr. 40, 1040 (1969)ADSCrossRefGoogle Scholar
  77. 2.77
    R. Simon: Resolving power of the SEM. J.Appl.Phys. 40, 2851 (1969)ADSCrossRefGoogle Scholar
  78. 2.78
    R. Speidel, J.P. Martin, B. Bauer: Testobjekte für die Bestimmung des Punktauflösungsvermögens im Elektronen-Rastermikroskop. Optik 34, 321 (1971)Google Scholar
  79. 2.79
    P. Gentsch, H. Gilde, L. Reimer: Measurement of the top-bottom effect in STEM of thick amorphous specimens. J.Micr. 100, 81 (1974)CrossRefGoogle Scholar
  80. 2.80
    S.A. Rishton, S.P. Beaumont, C.D.W. Wilkinson: Measurement of the profile of finely focused electron beams in a SEM. J.Phys.E 17, 296 (1984)ADSCrossRefGoogle Scholar
  81. 2.81
    K. Schur, C. Schulte, L. Reimer: Auflösungsvermögen und Kontrast von Oberflächenstufen bei der Abbildung mit einem Raster-Elektronenmikroskop. Z.angew.Phys. 23, 405 (1967)Google Scholar
  82. 2.82
    A.N. Broers: The use of Schottky emission LaB6 cathodes for high resolution SEM. In Microscopie Electronique 1370,Vol.1 ed. By P. Favard (Soc. Française Microscopie Electronique, Paris 1970)p.239Google Scholar
  83. 2.83
    L. Reimer, B. Volbert, P. Bracker: Quality control of SEM micrographs by laser diffractometry. Scanning 1, 233 (1978)CrossRefGoogle Scholar
  84. 2.84
    S.J. Erasmus, D.M. Holburn, K.C.A. Smith: On-line computation of diffractograms for the analysis of SEM images. Scanning 3, 273 (1980)CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 1985

Authors and Affiliations

  • Ludwig Reimer
    • 1
  1. 1.Physikalisches InstitutWestfätlische Wilhelms-Univeraität MünsterMünsterFed. Rep. of Germany

Personalised recommendations