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Auger electron Spectroscopy
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Auger electron Spectroscopy

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electron spectroscopy of core electrons

electron spectroscopy of core electrons

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Auger electron Spectroscopy Auger electron Spectroscopy Presentation Transcript

  • AUGER ELECTRON SPECTROSCOPY PRINCIPLES AND APPLICATIONS Yash CNS CUG
  • WHAT IS AUGER ELECTRON SPECTROSCOPY ? Auger Electron Spectroscopy (AES), is a widely used technique to investigate the composition of surfaces.  First discovered in 1923 by Lise Meitner and later independently discovered once again in 1925 by Pierre Auger [1]  Lise Meitner Pierre Victor Auger 1. P. Auger, J. Phys. Radium, 6, 205 (1925). 2
  • THE PARTICLE-SURFACE INTERACTIONS Auger Electron Spectroscopy Ions Electrons Photons Ions Electrons Photons Vacuum 3
  • BASIC OF AUGER ELECTRON SPECTROSCOPY Auger spectroscopy can be considered as involving three basic steps : (1) Atomic ionization (by removal of a core electron) (2) Electron emission (the Auger process) (3) Analysis of the emitted Auger electrons This last stage is simply a technical problem of detecting charged particles with high sensitivity, with the additional requirement that the kinetic energies of the emitted electrons must be determined. 4
  • PHOTOELECTRON VS. AUGER ELECTRON EMISSION 5
  • AUGER ELECTRON SPECTROSCOPY 6
  • PHYSICS BASIS An Auger transition is therefore characterized primarily by :1. the location of the initial hole 2. the location of the final two holes In general, since the initial ionisation is non-selective and the initial hole may therefore be in various shells, there will be many possible Auger transitions for a given element - some weak, some strong in intensity. AUGER SPECTROSCOPY is based upon the measurement of the kinetic energies of the emitted electrons. Each element in a sample being studied will give rise to a characteristic spectrum of peaks at various kinetic energies. This is an Auger spectrum of Pd metal - generated using a 2.5 keV electron beam to produce the initial core vacancies and hence to stimulate the Auger emission process. The main peaks for palladium occur between 220 & 340 eV. The peaks are situated on a high background which arises from the vast number of so-called secondary electrons generated by a multitude of inelastic scattering processes. Auger spectra are also often shown in a differentiated form : the reasons for this are partly historical, partly because it is possible to actually measure spectra directly in this form and by doing so get a better sensitivity for detection. The plot below shows the same spectrum in such a 7 differentiated form.
  • SITE DIFFERENTIATION CATSYMP19 PRESCHOOL 17TH JAN 2009 8
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  • SURFACE ANALYSIS DEPTHS CATSYMP19 PRESCHOOL 17TH JAN 2009 10
  • SCANNING AUGER ELECTRON SPECTROMETER 11
  • CATSYMP19 PRESCHOOL 17TH JAN 2009 12
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  • ELEMENTAL SHIFTS 14
  • QUANTITATIVE SURFACE ANALYSIS: AES By assuming the concentration to be a relative ratio of atoms, we can neglect the terms that depend only on the instrument: The values of S are determined theoretically or empirically with standards. AES is considered to be a semi-quantitative technique 15
  • Auger Analysis Examples A - Chemical composition, thickness and spatial distribution of the elements on cerium conversion layers deposited on galvanised steel. Effect of the treatment time. 16
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  • AES DEPTH PROFILING: AN EXAMPLE 18
  • CHEMICAL SHIFT 19
  • SEMICONDUCTOR DOPING SHIFT IN AES CATSYMP19 PRESCHOOL 20
  • DOPING MAP BY AES 21
  • THANK YOU FOR ATTENTION FROM YASH 22