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Ge 116 Module 1: Scanning Electron Microscopy

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Presentation on theme: "Ge 116 Module 1: Scanning Electron Microscopy"— Presentation transcript:

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


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

5 Electron sources: Filament

6 Electron sources: Field Emission

7 Electron sources: Field Emission

8 Electron sources: Comparison
Brightness (A/cm2sr) Lifetime Source Size Beam Stability W filament 105 <100 h >30 m 1% LaB6 106 <1000 h >5 m Field Emission 108 >1000 h < 30 nm 2%

9 Electron optics Condenser Lenses Apertures Stigmators Scan Coils
Objective Lens

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

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 Beam-Specimen Interaction Volume
Increased backscatter yield for inclined specimen surface Locations of secondary electron emission Horizontal spread of backscatter emission for normal and inclined specimens

15 Backscattered Electrons

16 Backscattered Electrons
(b is specimen current image)

17 Secondary Electrons

18 Secondary Electrons

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