Scanning Electron Microscopy

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Back Scattered Electrons 0.5 Backscattered electrons 0.4 Electron yield 0.3 0.2 0.1 Secondary electrons 0 20 40 60 80 Atomic number (Z) Electron yield (i.e. intensity) as a function of atomic number for backscattered and Secondary electrons. • Back Scattered electron have approximately the same energy as the primary electron beam and are therefore easy to detect - simply by a semiconductor placed above the sample :- Analytical Workshop 2012 Schematic of a backscattered electron detector.
BackScattered Imaging • Back scattered electrons are deflected more by heavier atoms leading to a brighter contrast in BEI images – the lighter the region the heavier the element present. a) b) White region Dark region Grey region • a)Secondary image of a cement showing surface morphology • b)Backscattered image of same area showing compositional inhomogeneity • Three distinct regions in b), EDS analysis can then be used to find the different compositions of the these regions. Analytical Workshop 2012
Page 1 and 2: Scanning Electron Microscopy Field
Page 3 and 4: Improving Resolution • Firstly, t
Page 5 and 6: Layout of a Generic SEM Gun 1 Apert
Page 7 and 8: Thermionic Gun Filament Wehnelt cyl
Page 9 and 10: Comparison of Sources •W filament
Page 11 and 12: Scanning the Beam\Beam Interactions
Page 13 and 14: Signal Detection • The Everhard -
Page 15 and 16: Variable Pressure SEM •Localised
Page 17: Compositional Analysis - Back Scatt
Page 21 and 22: Examples Images Imaged using ET Det
Page 23: Conclusions •Scanning Electron Mi

Scanning Electron Microscopy

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