The document discusses scanning electron microscopy (SEM) and its use in characterizing materials. SEM uses an electron beam focused into a probe that scans over a sample, creating signals like secondary electrons and backscattered electrons. These signals are detected and used to form a magnified image of the sample's surface on a cathode ray tube. SEM provides higher magnification than light microscopes, with a greater depth of field. It is capable of elemental analysis and mapping at magnifications from around 10x to 300,000x, with typical operating ranges of 500eV-50keV beam energy.

1. Characterization of Materials
(MT 606)
MME 6th SEMESTER,
National Institute of Foundry and Forge, 2020
Dr Tapabrata Maity (Assistant Professor)

2. Scanning Electron Microscope
Scanning electron microscopy Characterization of Materials
Chapter TWO

3. ScanningElectronMicroscopy(SEM) 1.2.2
The Scanning Electron Microscope (SEM) is often the first analytical instrument
used when a "quick look" at a material is required and the light microscope no
longerprovides adequateresolution. In the SEMan electron beam is focusedinto a
fine probe and subsequently raster scanned over a small rectangular area. As the
beam interactswith the sampleit createsvarioussignals(secondaryelectrons,inter-
nal currents, photon emission, etc.), all of which can be appropriately detected.
These signals are highly localized to the area directly under the beam. By using
these signals to modulate the brightness of a cathode ray tube, which is raster
scanned in synchronismwith the electronbeam, an image is formed on the screen.
This image is highly magnified and usually has the U 1 ~ ~ k "of a traditional micro-
scopic image but with a much greater depth of field. With ancillary detectors, the
instrument is capableof elementalanalysis.
Main use High magnification imaging and composition
(elemental) mapping
No, some electron beam damage
10~-300,000~;5000~-100,000~is the typical
operating range
500eV-50 keV; typically,20-30 keV
conducting film; must be vacuum compatible
Less thanO.lmm, up to 10cm or more
1-50 nm in secondaryelectron mode
Varies from a few nm to a few pm, depending upon
the acceleratingvoltageand the mode of analysis
Destructive
Magnification range
Beam energy range
Samplerequirements Minimal, occasionally must be coated with a
Samplesize
Lateralresolution
Depth sampled
Bonding information No
Depth profiling Only indirect
capabilities
Instrument cost $100,000-$300,000is typical
Size Electronicsconsole3ft. x 5 fi.;electron beam column
3 ft. x 3 ft.
Basicfeatures
Scanning electron microscopy Characterization of Materials

4. SchematicdiagramofaSEM
Scanning electron microscopy Characterization of Materials

5. SignalwhichmaybeusedintheSEM
Scanning electron microscopy Characterization of Materials

6. InteractionvolumeX
Scanning electron microscopy Characterization of Materials

7. Detectingsecondaryelectrons
Scanning electron microscopy Characterization of Materials

8. Detectingbackscatteredelectrons
Scanning electron microscopy Characterization of Materials

9. Detectingbackscatteredelectrons
Scanning electron microscopy Characterization of Materials