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The probe

Some material used from:. The probe. EPMA - electron probe microanalysis. Probe signals. EPMA - electron probe microanalysis. 'New' signal - cathodoluminescence visible and near-visible radiation. Application: identify impurities in semiconductors. EPMA - electron probe microanalysis.

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The probe

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  1. Some material used from: The probe

  2. EPMA - electron probe microanalysis Probe signals

  3. EPMA - electron probe microanalysis 'New' signal - cathodoluminescence visible and near-visible radiation Application: identify impurities in semiconductors

  4. EPMA - electron probe microanalysis The instrument

  5. EPMA - electron probe microanalysis Measuring x-ray wavelengths In Braggs' law, keep d constant (d is known) use single crystal (remember monochromator)  = 2d sin  Measure  to get  - identify & quantify element Use curved single crystal for focusing

  6. EPMA - electron probe microanalysis Measuring x-ray wavelengths Focusing or Rowland circle radius kept constant. Vary  by translating crystal away from specimen & rotating. Counter moved to stay near focus point on circle.

  7. EPMA - electron probe microanalysis Qualitative Identify and characterize phases (shape, size, surface relief, etc.) Elements present in each phase Quantitative Complete chemical analysis on a sub-micro scale Elemental concentration mapping

  8. EPMA - electron probe microanalysis Interaction volume details

  9. EPMA - electron probe microanalysis Interaction volume Depth increases with accelerating voltage decreases with at. no.

  10. EPMA - electron probe microanalysis Interaction volume Diameter increases with probe current

  11. EPMA - electron probe microanalysis Matrix corrections for quantitative x-ray analysis For a each element: C/C°~ I/I° = k or: C/C° = k • ZAF C = concn in specimen C°= concn in std I = intensity from specimen I° = intensity from std ZAF = matrix corrections Z - at. no. A - absorption F - fluorescence

  12. Varies with composition and accelerating voltage EPMA - electron probe microanalysis Atomic no. correction Function of electron backscattering factor & electron stopping power - depend upon the average at. nos. of unknown and standard

  13. EPMA - electron probe microanalysis Absorption correction

  14. A varies with , takeoff angle, accelerating voltage EPMA - electron probe microanalysis Absorption correction

  15. EPMA - electron probe microanalysis Fluorescence correction electrons ––> primary fluorescent x-rays ––> secondary fluorescent x-rays

  16. Varies with composition and accelerating voltage EPMA - electron probe microanalysis Fluorescence correction electrons ––> primary fluorescent x-rays ––> secondary fluorescent x-rays

  17. EPMA - electron probe microanalysis Can't calculate ZAFs unless concns known. Use k values (I/I° = k) to estimate compositions of each element. Then calculate ZAFs, and refine by iteration

  18. EPMA - electron probe microanalysis Micro scale elemental analysis

  19. EPMA - electron probe microanalysis Micro scale elemental analysis Pd on particles

  20. EPMA - electron probe microanalysis Micro scale elemental analysis

  21. EPMA - electron probe microanalysis Micro scale elemental analysis

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