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Introduction to Auger Electron Spectroscopy (AES) MATSE 305 - November 23, 1998

Introduction to Auger Electron Spectroscopy (AES) MATSE 305 - November 23, 1998. Center for Microanalysis of Materials Frederick Seitz Materials Research Laboratory University of Illinois at Urbana-Champaign. What is Auger?.

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Introduction to Auger Electron Spectroscopy (AES) MATSE 305 - November 23, 1998

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  1. Introduction to Auger Electron Spectroscopy (AES)MATSE 305 - November 23, 1998 Center for Microanalysis of Materials Frederick Seitz Materials Research Laboratory University of Illinois at Urbana-Champaign

  2. What is Auger? Auger Electron Spectroscopy (AES) is a widely used technique to investigate the chemical composition of surfaces.

  3. Why the Odd Name?

  4. Surface Sensitivity

  5. The Auger Process STEP 3 KLL Auger electron emitted to conserve energy released in step 2 STEP 1 Ejected electron FREE ELECTRON LEVEL CONDUCTION BAND FERMI LEVEL Auger Transition Named: KLL VALENCE BAND STEP 3 (alternative) an x-ray is emitted to conserve energy released in step 2 E(Auger)=E(K)-E(L2)-E(L3) E(X-ray)=E(K)-E(L2) L3 2p L2 2s L1 STEP 2 L electron falls to fill vacancy Incident Electron 1s K

  6. Auger Energy Scale • The AES instrument measures the kinetic energy of all collected electrons.

  7. AES Electron vs. X-ray Photon

  8. Auger Stats • Primary Beam = 3 - 20 KeV electrons • Detection Sensitivity = ~1 atomic % • Sampling Distance (depth) = 2 to 4 nm • Analysis Diameter = 80nm to several mm • Elements Detectable = Li and above

  9. Auger Data Formats Raw Data Differentiated Data

  10. AES Can Identify Elements

  11. AES Sensitivity Factors

  12. Peak Height / Quantitation For quantitation the derivative form of the data is used. Sensitivity Factors are used to adjust the peak heights of all elements present in the sample. The composition is normalized to 100% to determine the amount of each element.

  13. Additional Capabilities of Auger • Identify surface contaminants and composition. • Study composition as a function of depth. • Analyze sample features as small as 80nm. Using an electron gun for the primary beam allows small analysis spot sizes.

  14. Why UHV for Surface Analysis? Pressure Torr Degree of Vacuum • Remove adsorbed gases from the sample. • Eliminate adsorption of contaminants on the sample. • Prevent arcing and high voltage breakdown. • Increase the mean free path for electrons, ions and photons. 2 10 Low Vacuum -1 10 Medium Vacuum -4 10 High Vacuum -8 10 Ultra-High Vacuum -11 10

  15. AES Instrument Configuration • Elements of Typical Auger System: • Electron Gun • Analyzer • Secondary Electron Detector • Ion Gun • Sample Stage • Introduction System

  16. Significance of Primary Beam The Electron Beam is functioning both as the imaging beam and the primary beam for analysis. This means that the area of interest on the sample can be directly aligned for analysis.

  17. MRL Instrumentation PHI Model 660 Scanning Auger Microprobe

  18. Sputtering Samples

  19. Al/Pd/GaN Thin Film Example (cross section)

  20. Al/Pd/GaN Profile Data

  21. Al/Pd/GaN Atomic Concentration Data

  22. Area Specific Depth Profile Example

  23. Summary of Surface Techniques

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