1. ED and WD X-ray Analysis
Elemental analysis in the SEM
The ‘what’, ‘where’ and ‘how much’?

2. ‘What’ - Identifying the elements
Locate the electron beam on the region of the sample
Start acquisition
Spectrum shows peaks
Elements are identified and labelled
The higher the peak is above the background, the higher the concentration of that element

3. X-ray Generation L lines K lines
Demonstrate K and L series lines for, say, Fe and Mo using spectrum synthesis
L lines
K lines

4. X-ray line series
Sn L series
Ca K series

5. ED and/or WD? Energy dispersive Measures X-ray from its energy
Wavelength dispersive
Measures X-ray from its wavelength
Energy in keV = / wavelength in Angstroms
High energy = short wavelength
Low energy = long wavelength

6. ED detectors
Old type Si(Li) detectors needed to be kept at liquid nitrogen temperature
New type SDD detectors are cooled to Peltier temperature
X-ray energy converted to charge pulse and then to a voltage pulse
Simultaneous acquisition of elements Be to U
Mention X-ray pulse processor

7. WD spectrometer Diffraction according to Bragg’s law nλ=2dsinθ
Much better peak resolution then ED
Much better sensitivity for trace elements
Sequential analysis of elements Be to U
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8. ED and WD together resolution sensitivity
Explain advantages/disadvantages of ED/WD
Why it’s good to use both

9. What can be analysed? Just about anything you can put in the SEM!
Microanalysis – typical volume analysed about 1µm
Depends on accelerating voltage and density
Nanoanalysis – need to reduce electron beam penetration
Reduce accelerating voltage
For best results the sample should be flat and polished and conducting
But often you can achieve adequate results from ‘rough’ samples

10. Typical applications Comparing ‘good’ and ‘bad’ samples
Identifying compositions in fine grain structures
Identifying sources of contamination
Measuring variation in composition across an interface

11. Industrial and research applications
Failure analysis - automotive, aerospace, semiconductors
Materials research
Quality Control
Photovoltaics
Light Emitting Diodes
Thin film analysis
Artefact conservation
Steel inclusions
Gun Shot Residue forensics

12. ‘Where’ - Mapping
Scan the electron beam and acquire X-ray information at each pixel position
Display the results as a series of maps for each element or as a single colour image

13. Individual maps

14. ED spectrum at each point

15. Interaction volume
Ni 5kV
0.1 µm
1µm
Si 5kV
0.4 µm

16. Mapping large areas Field width 0.53mm 3x3 maps stitched
WD geometry requirement – will defocus at low mag.

17. ‘How much’ – Quantitative Analysis
Element
Weight%
Al K
1.42
Ti K
1.29
Cr K
17.46
Fe K
33.65
Ni K
42.29
Mo L
3.88
Totals
100.00

18. Processing for quant Measure peak areas Compare with standards
Apply inter-element corrections
For accurate results, the sample should be flat, polished, homogeneous (on the micro-scale) and conducting

19. Detection limits Typically 0.1% to 0.5% for ED
Order of magnitude better for WD
Exact detection limit depends on operating conditions and composition

20. ED or WD? ED for major elements, fast analysis, rough samples
Ideal for a ‘quick look’
WD for minor and trace elements and overlaps
Better sensitivity and resolution, but slow
ED and WD are complementary techniques for analysis