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Ge 116 Module 1: Scanning Electron Microscopy Part 1: Electron optics, beam- specimen interactions & imaging.

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Presentation on theme: "Ge 116 Module 1: Scanning Electron Microscopy Part 1: Electron optics, beam- specimen interactions & imaging."— Presentation transcript:

1 Ge 116 Module 1: Scanning Electron Microscopy Part 1: Electron optics, beam- specimen interactions & imaging

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3 What is an SEM? Parts of an SEM: Vacuum chamber and pumps Electron source Electron column: High Voltage Optics Scan coils Stage Detectors Analog or digital display

4 Electron sources: Filament

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6 Electron sources: Field Emission

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8 Electron sources: Comparison SourceBrightness (A/cm 2 sr) LifetimeSource Size Beam Stability W filament10 5 <100 h >30 m 1% LaB <1000 h >5 m 1% Field Emission 10 8 >1000 h< 30 nm2%

9 Electron optics Condenser Lenses Apertures Stigmators Scan Coils Objective Lens

10 Electron Beam Limits Minimum beam diameter ~1 Spherical Aberration Coefficient, ~2 cm Electon DeBroglie wavelength, ~9 pm Probe current Source Brightness

11 Electron Beam Limits

12 Beam-Specimen Interactions Elastic –Back-scattered electrons Inelastic –Secondary electrons –Bremsstrahlung X-rays –Characteristic X-rays –Auger electrons Other –Cathodoluminescence –Specimen current

13 Beam-Specimen Interaction Volume

14 Increased backscatter yield for inclined specimen surface Horizontal spread of backscatter emission for normal and inclined specimens Locations of secondary electron emission

15 Backscattered Electrons

16 (b is specimen current image)

17 Secondary Electrons

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