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