1. Auger Electron Spectroscopy (AES) 1

2. Brief History Auger Effect discovered in 1920’s Meitner published first journal Auger transitions considered noise at first 1953-JJ Lander Characterization of solids today 2

3. Three Steps of Auger Electron Spectroscopy Note: Solid Samples 1) Atomic ionization 2) Electron emission 3) Analysis 3

4. Atomic Ionization “Core Hole” Electron Beam Core hole probability: σ=Constant x C(E i /E A )/E A ^2 4 http://pages.jh.edu/~chem/fairbr/ surfacelab/aes.html

5. The Auger Process 5 http://pages.jh.edu/~chem/fairbr/surfacelab/a es.html

6. Important Nomenclatures Electron orbitals and principle quantum number (n) Given subscripts based off spins 6 http://pages.jh.edu/~chem/fairbr/surfacelab/a es.html

7. Auger Transissions KE of Auger Electron= E(A)=EK-(EL1+EL2) Ex: Silicon K1=1600 L1=60, L2=30 E(A)=? Rough Estimate of KE 7

8. Auger Electron Spectra Direct Spectra 1x zoom (bottom) 10x zoom (top) 8 newton.phys.uaic.ro/data/ppt/L5(AES).ppt

9. Auger Electron Spectra dN(E)/dE Plotd[E*N(E)]/dE plot 9 Density of States= N(E)=(4π/h 3 )(2m h * ) 3/2 (E v -E) 1/2 newton.phys.uaic.ro/data/ppt/L5(AES).ppt

10. Qualitative Analysis Elemental Identification Procedure Main Auger Peaks ID’d Values compared to table ID’d elements labeled on spec Repeat procedure until peaks found Auger Sample 10

11. Qualitative Analysis 11 http://www.eag.com/cmss_files/imagelibrary/ auger-electron-energies.gif

12. Electron Beam/Sample Interaction Penetrates 1-3µm Mean-free path 5-50 angstroms Backscattered electrons Secondary electrons X-Rays from sample Auger Electron 12 http://en.wikipedia.org/wiki/Scanning_electro n_microscope#Detection_of_backscattered_el ectrons

13. Sample Prep Sample 1mm thickness, 1 cm diameter Mounted in Ultra-High Vacuum Sputtering Annealing 13 http://wwwold.ece.utep.edu/research/webedl /cdte/Fabrication/sputtering.gif

14. Electron Beam Monochromatic electrons Beam 0.1mm-0.5mm wide Scans surface 14 http://www.bing.com/images/search?q=Electron+Beam+Tube&view=detailv2&&&id=4CF 43715C2DE021317F945D9A8206DE75B473527&selectedIndex=9&ccid=k%2fBps2H4&simi d=608029209144657635&thid=JN.jnUWfUaASQqjpf3KGWNidQ&ajaxhist=0

15. Analyzers Grid Purposes Low Energy Electron Diffraction (LEED) 15 Retarding Field Analyzer (RFA) http://www.udel.edu/pchem/C874/LEED_lect ure.pdf

16. Non-Retarding Mode Applied Voltage without suppressor Broader energy absorbed More imaging per run Less luminescence Less angular contact 16

17. RFA LEED optics Low-energy electrons strike screen (30-300eV) De Broglie relationship λ A = (150/E eV ) 1/2 Spacing between atoms Fluoresce when strike screen 17 http://www.udel.edu/pchem/C874/LEED_lect ure.pdf

18. Data Analysis XY-Recorder-intensities Video Camera Collects all energies Single points collected Produces spectra Compared to Calculated 18 http://www.matscieng.sunysb.edu/leed/dataa cquire.html

19. Cylindrical Mirror Analyzer Two concentric metal cylinders Different V on each cylinder e- fired from gun to sample e- of certain energies analyzed Double Pass Design 19 http://uksaf.org/tech/cma.html

20. Hemispherical Analyzer Concave and Convex Hemisphere Centers of curvature are coincident so electrons come to a point at detector Electric Field-varying voltages Pass electrons to analyzer Series of lenses before detector Constant Retard Ration (CRR) Constant Analysis Energy (CAE) 20 http://uksaf.org/tech/cha.html

21. Advantages and Disadvantages Advantages Surface Sensitive Elemental and Chemical composition and analysis by comparing sample to known samples Quantitative composition information as a function of depth below the surface Good for spatial distribution of elements in sample (structure). I will fix this slide tomorrow just haven’t found out what to do yet about it. Disadvantages Samples must be able to compatible with ultra high vacuum Samples must be conductive Possibility of beam damage for organic molecules Cannot detect hydrogen or helium Quantitative detection is dependent on the element, but accurate to high sensitivity 21

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