1. Scanning Electron Microscopy

2. What is an SEM?

3. What is an SEM?
A Scanning Electron Microscope is an instrument that investigates the surfaces of solid samples by using a beam of electrons in a vacuum.

4. What is an SEM?
A Scanning Electron Microscope is an instrument that investigates the surfaces of solid samples by using a beam of electrons in a vacuum.
The image is generated by the secondary emissions from the sample.

5. Advantages of using an SEM instead of a light microscope

6. Advantages of using an SEM instead of a light microscope
Imaging
high resolution (because of short wavelength) - >1.4nm

7. Advantages of using an SEM instead of a light microscope
Imaging
high resolution (because of short wavelength) - >1.4nm
Secondary electron imaging for topology

8. Advantages of using an SEM instead of a light microscope
Imaging
high resolution (because of short wavelength) - >1.4nm
Secondary electron imaging for topology
Backscatter electron imaging for chemistry

9. Advantages of using an SEM instead of a light microscope
Imaging
high resolution (because of short wavelength) - >1.4nm
Secondary electron imaging for topology
Backscatter electron imaging for chemistry
High depth of field

10. Advantages of using an SEM instead of a light microscope
Imaging
high resolution (because of short wavelength) - >1.4nm
Secondary electron imaging for topology
Backscatter electron imaging for chemistry
High depth of field
Elemental Analysis – EDXS (Energy-dispersive X-ray analysis)

11. Advantages of using an SEM instead of a light microscope
Imaging
high resolution (because of short wavelength) - >1.4nm
Secondary electron imaging for topology
Backscatter electron imaging for chemistry
High depth of field
Elemental Analysis – EDXS (Energy-dispersive X-ray analysis)
Structural Analysis – EBSD (Electron Back-scatter Diffraction analysis)

12. Advantages of using an SEM instead of a light microscope
Imaging
high resolution (because of short wavelength) - >1.4nm
Secondary electron imaging for topology
Backscatter electron imaging for chemistry
High depth of field
Elemental Analysis – EDXS (Energy-dispersive X-ray analysis)
Structural Analysis – EBSD (Electron Back-scatter Diffraction analysis)
Ease of sample preparation since most SEMs only require the sample to be conductive.

13. Sample Constraints

14. Sample Constraints
Must fit in chamber (!)

15. Sample Constraints Must fit in chamber
Must be compatible with vacuum (even for ESEM samples)

16. Sample Constraints Must fit in chamber
Must be compatible with vacuum (even for ESEM samples)
Must have conductive surface (not necessary for ESEM samples)

17. JEOL 5910 General-Purpose SEM

18. FEI XL30 FEG-ESEM

19. JEOL 6320 High-resolution SEM

20. Secondary Electron Images
Give information about sample's topography

21. Give information about sample's chemistry
BSE Images
Give information about sample's chemistry

22. Give information about sample's composition
EDS Spectra
Give information about sample's composition

23. Give information about elemental distribution in the sample
X-Ray Maps
Give information about elemental distribution in the sample SE Cu Pb Sn

24. Electron beam strikes a crystalline material tilted at 70°
Backscatter patterns composed of intersecting bands
Indexable patterns
Scanning Electron Microscope (SEM) strikes a crystalline material mounted at an incline around 70°, the electrons disperse beneath the surface, and diffract among the crystallographic planes. The diffracted beam produces electron backscatter patterns composed of intersecting bands, These patterns are imaged by placing a phosphor screen very close to the sample in the SEM sample chamber.
The bands in the pattern are directly related to the crystal lattice structure in the sampled region. Analyzing of the pattern and bands can provide key information about the crystal structure for the measured phase such as:
The symmetry of the crystal lattice is reflected in the pattern.
The width and intensity of the bands are directly related to the spacing of atoms in the crystal planes.
The angles between the bands are directly related to the angles between planes in the crystal lattice.
Indexable patterns can be obtained from about 0.2 microns with a tungsten filament SEM and from about 0.05 microns with a field emission source.

25. The data obtained can be processed to create Orientation Imaging Micrographs, providing a visual representation of the crystallographic microstructure. Each point can be assigned a color or gray scale value based on a variety of parameters such as orientation, image quality, confidence index, phase, etc.
Crystals with their 111 axis normal to the surface of the sample will be blue, and so on.
Grain boundary Map can be obtained by comparing the orientation between each pair of neighboring points in an orientation imaging microscopy (OIM) scan. A line is drawn separating a pair of points if the difference in orientation between the points exceeds a given tolerance angle.
These figures illustrate a side-by-side comparison of optical and OIM micrographs of an intergranular stress corrosion crack in a nickel- based super alloy

26. Center for Materials Science and Engineering Electron Microscopy SEF
Location:
Normal Working Hours: 8:30 am – 4:45 pm on M-F
24 hr accessible for evening/weekend users (not for undergraduates)
Staff:
Dr. Anthony (Tony) Garratt-Reed (TEM, SEM, STEM)
Dr. Yong Zhang (TEM, SEM, STEM)
Mr. Patrick Boisvert (SEM, Microtome)