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  3. Wavelength Dispersive Spectroscopy (WDS)
  4. Wave Spectrometer

Wave Spectrometer

AZtecWave Spectrometer

The Wave spectrometer delivers the highest spectral resolution available for the SEM due to its unique, fully focusing Rowland circle geometry and curved crystals. The AZtecWave software combines the unique capability of the Wave spectrometer with Ultim Max for EDS to deliver a highly sensitive and accurate solution for major through to trace element analysis on the SEM. 

The Wave spectrometer provides:

  • Separation of more X-ray peak overlaps, providing positive element identification and accurate quantification

  • Lower detection limits (<100 ppm for many elements)


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Why add Wave to a Scanning Electron Microscope (SEM)?

Schematic showing the internal mechanical parts of the Rowland Circle Wave Spectrometer for WDS analysis

High spectral resolution:

  • Achieve the highest spectral resolution with the only fully focussing Rowland circle geometry Wavelength Dispersive X-ray Spectrometer (WDS / WDX) available for the SEM (e.g. Si Kα = <2 eV, Fe Kα = <25 eV)
  • Bent and ground crystals and a motorised counter entrance slit further optimises resolution and peak to background for every X-ray line
  • Fully separate the most closely spaced X-ray lines that cannot be achieved with other techniques – for example, the Ti Kβ/V Kα overlap can only be fully resolved with Wave
  • Make more accurate quantitative measurements of elements impacted by peak overlaps in the EDS spectrum
Wave provides for the highest spectral resolution for the SEM – for the separation of closely spaced X-ray lines
Comparison of a WDS scan result and an EDS spectrum acquired from a sample containing sulphur and molybdenum showing that Rowland circle WDS can resolve the X-ray peak overlaps between these elements
The highest SEM-WDS resolution available - for separation of closely spaced lines, such as S Kα = 2.307 keV and Mo Lα = 2.293 keV

Low detection limits over a wide energy range:

  • Wave delivers detection limits of <100 ppm for many elements (e.g. Si Kα = 9 ppm, Fe Kα = 15 ppm)
  • Positive identification and accurate quantification of minor and trace elements
  • Optimised for a wide range of X-ray energies (max of 0.07 – 15.33 keV) enabling the ideal X-ray lines to be selected to give more accurate results
  • Analyse a wide range of X-ray energies, which is essential for many applications
  • Unique dual counters in series using Ar-CH4 for optimised light element and Xe for optimised high energy collection

Straightforward sample and spectrometer setup:

  • The inclined angle of the Wave spectrometer on the SEM column makes it relatively insensitive to sample height
  • Analytical focus can simply be achieved with SEM secondary electron imaging
  • No requirement for fragile optic, time-consuming focussing routines, or transmission losses for higher energy lines
  • Setup Spectrometer in the AZtecWave software ensures the Wave spectrometer is optimized prior to analysis
  • Spectrometer miniview and mimic shows spectrometer position and status at all times
Graphical user interface showing status mini-view for the Wave Spectrometer in the AZtecWave software
Spectrometer miniview in the AZtecWave software

AZtecWave brings electron microprobe (EPMA) like performance to the SEM – enabling an effective combination of highly accurate quantitative elemental analysis with high resolution electron imaging and other SEM-based techniques (e.g. EBSD).

Snapshot of the AZtecWave software interface showing elemental data displayed in a table
| Composition of a stainless steel determined by a combination of EDS and WDS in AZtecWave

Wave Spectrometer with W1 electronics

Design/geometry

Fully focussing 210 mm Rowland circle with a 2θ range of 33° to 135°
(i.e. electron microprobe style)

Orientation on SEM column

Inclined

Attachment to SEM

Interface with motorised gate valve as standard

Diffracting crystals

Maximum of 6 on rotating crystal turret
Standard: TAP, PET, LiF (200), plus LSM80N or LSM60 and LSM200
Additional options: LSM200, LSM80N, LSM80E, LSM60, LiF (220)

Quantification range

Wave 500 spectrometer = 0.17 – 10.84 keV (B to Pu)
Wave 700 spectrometer = 0.07 – 10.84 keV (Be to Pu)
Maximum achievable = 0.07 – 15.33 keV

Spectral resolution

Si Kα = <2 eV
Fe Kα = <25 eV

Detection limit

Si Kα = 9 ppm
Fe Kα = 15 ppm

X-ray counters

P10 (Ar-CH4) flow proportional counter and Xe sealed proportional counter mounted in tandem

Flyer: AZtecWave WDS & EDS Hardware
Application note: Using WDS and AZtecWave For Quality Control and Quality Assurance of Metals
Flyer: AZtecWave Software
Flyer: 5 Reasons to Add a Wave Spectrometer and AZtecWave to your SEM
Technical Data sheet: Max+
Technical Data sheet: AZtec Standards
Infosheet: WDS Explained
Blog: WDS-SEM approach for studying doping in semiconductors
Blog: 5 Reasons to add a Wave Spectrometer to your SEM
Blog: Why is Spectral Resolution so Important when Analysing using WDS?
Blog: Why do all WD spectrometers not give the same results?
Video: WDS detection & EDS speed with AZtec accuracy and accessibility
Video: Introduction to Wavelength Dispersive Spectrometry (WDS / WDX)
Video: Why AZtecWave? 

High quality reference standards for standardizing WDS and EDS quantitative analysis

Periodic table showing in colour the elements that are present in the 37 and 55 microanalysis standard blocks
  • Available in 37 standard (42 elements), and 55 standard (56 element) blocks
  • All standards are supplied with certificate of analysis
  • Standard blocks include a Faraday cup for accurate measurement of beam current
  • All standard blocks are manufactured for Oxford Instruments by Micro-Analysis Consultants Ltd

 

 

 

Schematic illustration of a standard block containing pure elements, simple binaries, and minerals
Schematic illustration of a standard block containing pure elements, simple binaries, and minerals

Max+ interface optimises EDS when using very high beam currents

Drawings of the max plus aperture assembly showing its position with the associated EDS detector retracted and inserted Technical depiction of the range of beam currents that are possible to use for different types of analysis when using the max plus aperture assembly Graph showing the range of beam currents required for different types of microanalysis and showing how the max+ aperture assembly can extend the possible range for EDS in order to be able to effectively measure trace elements concurrently with WDS

The Max+ interface has apertures of varying size used to reduce X-ray count rate into the EDS detector when working at very high beam currents

  • Optimum EDS performance always achieved so the analysis can be optimised for WDS detection
  • Large area EDS Ultim Max detectors with Max+ are compatible with all applications from low beam current EDS nano-analysis to combined EDS and WDS microanalysis
  • AZtec Wave always produces accurate answers 

Detailed Applications for WDS 

Wavelength Dispersive Spectroscopy (WDS) lends itself to applications requiring quantitative compositional results from solid samples, particularly where concentrations of minor and trace elements need to be accurately determined. Application examples exist in a wide range of sectors, including metallurgy, geology, electronics, semiconductors, forensics, and energy generation and storage. Combining WDS with EDS analysis, through AZtecWave, provides a versatile system for non-destructive, compositional analysis in the SEM.

Discover detailed applications examples

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