Scanning Electron Microscopy

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Focusing the Beam • After the beam is formed it is focused by a condenser lens system to form a ‘probe’. • The lenses are electromagnetic – the focal length changes as current in the coil changes. • After focusing, the beam is passed through an aperture which excludes electrons which are not on the optical axis – improving resolution. • Inconsistencies in the beam are corrected by stigmators and the beam focused onto the sample. A typical Electro Magnetic Lens Analytical Workshop 2012
Scanning the Beam\Beam Interactions • Deflector coils move the beam back and forth over the sample and the signal generated from each area is collected simultaneously, building up the final image shown on the monitor. • Many signals are generated at the surface of the sample and many different forms of analysis may be performed. • The ‘interaction volume’ is the area of the sample excited by the electron beam to produce a signal. Incident Electrons (Electron Probe) Auger Electrons Secondary Electrons Backscattered Electrons Continuum X-Rays Fluorescence X-Rays Characteristic X-Rays Signals generated in the interaction volume 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: Comparison of Sources •W filament
Page 13 and 14: Signal Detection • The Everhard -
Page 15 and 16: Variable Pressure SEM •Localised
Page 17 and 18: Compositional Analysis - Back Scatt
Page 19 and 20: BackScattered Imaging • Back scat
Page 21 and 22: Examples Images Imaged using ET Det
Page 23: Conclusions •Scanning Electron Mi

Scanning Electron Microscopy

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