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Electron Spectroscopy for chemical analysis, ESCA and Auger Electron Spectroscopy, AES,

Electron Spectroscopy for chemical analysis, ESCA and Auger Electron Spectroscopy, AES,. KMU 396 Material Science and Technology. Emre Ertuğrul 20824006 Emin Şahin 20824259 Seçkin Gökçe 20824044. Outline of Lecture. ESCA. AES. Introduction -History of AES -General Uses

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Electron Spectroscopy for chemical analysis, ESCA and Auger Electron Spectroscopy, AES,

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  1. Electron Spectroscopy for chemical analysis, ESCAandAuger Electron Spectroscopy, AES, • KMU 396 Material Science and Technology Emre Ertuğrul 20824006 Emin Şahin 20824259 Seçkin Gökçe 20824044

  2. Outline of Lecture ESCA AES • Introduction • -History of AES • -General Uses • Principles of Operation • Instrumentation • Auger Spectrum • Common Applications • Advantages & Disadvantages of AES • Introduction -advantages, -disadvantages • Principles of ESCA • The photoelectron effect • Instrumentation • Analysis Capabilities -Elemental analysis -Chemical state analysis -More complex effects • Surface Sensitivity

  3. Introduction • ESCA provides unique information about chemical composition • And chemical state of a surface • useful for biomaterials • advantages -- surface sensitive (top few monolayers) -- wide range of solids -- relatively non-destructive • disadvantages -- expensive, slow, poor spatial resolution, requires high vacuum

  4. Principles of ESCA • ESCA is based on the photoelectron effect. • A high energy X-ray photon can ionize anatom • Detecting electrons ejected from higher orbitals • producing an ejected free electron with kinetic energy KE: • KE=hv-BE *BE=energy necessary to remove a specific electron from an atom. BE ≈ orbital energy *h=Planck Constant *v=frequency of light

  5. Instrumentation • Essential components: • Sample: usually 1 cm2 • X-ray source: Al: 1486.6 eV; Mg 1256.6 eV • Electron Energy Analyzer: 100 mm radius concentric hemispherical analyzer; vary voltages to vary pass energy. • Detector: electron multiplier (channeltron) • Electronics, Computer • Note: All in ultrahigh vacuum (<10-8 Torr) (<10-11 atm) • State-of-the-art small spot ESCA: 10 mm spot size. Figure A

  6. http://www.sphysics.com/ AES in Laboratory

  7. Analysis Capabilities • Elemental Analysis: atoms have valence and core electrons: Core-level Binding energies provide unique signature of elements. • Quantitative analysis: measure intensities, use standards or sensitivity factor

  8. Applications -- Surface contamination -- Failure analysis -- Effects of surface treatments -- Coating, films -- Tribological effects -- Depth Profiling (Ar+ sputtering)

  9. ESCA studies of polyimide Pyromellitic dianhydride -- oxydianiline PMDA - ODA Figure B

  10. Introduction to Auger Electron Spectroscopy (AES) • 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).

  11. General Uses • Surface composition analysis for metals, powders, insulators, • Identification of particulates, localized dopants or contaminants, visual defects • Investigation of submicrometer dimension structures • Grain boundary investigations, e.g. intergranular corrosion • Analysis of surface coatings and thin films • When combined with ion sputtering, elemental depth profiling of surface and/or interfacial layers

  12. Principles of Operation Auger Electron Spectroscopy Ions Electrons Photons Ions Electrons Photons • samplebombardment by electrons • core electron removed • electron from a higher energy level fall into the vacancy • release of energy. • measured energy anddefinedsample Vacuum

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

  14. Auger Spectrum Figure C http://mee-inc.com/sam.html

  15. Advantages • Monolayer-sensitive surface analysis with high spatial resolution • Elemental mapping across surface • Elemental depth profiling with uniform sensitivity • It is sensitive to light elements (except H and He).

  16. Limits of Techniqueand Disadvantages • Surface Sensitivity: < 1 nm • Lateral Resolution: < 50 nm • Analytical Volume: 10-18 cm3 • Insulators are difficult to study due to surface charging. • Surface may be damaged by the incident electron beam.

  17. Summary ESCA & AES is very important analytical techniques used in materials scienceto investigate molecular surface structures and their electronic properties.

  18. References • http://www.rci.rutgers.edu/.../LECTURE5 • http://nanoall.blogspot.com/2011/10/auger-electron-spectrometry-aes.html • http://www.orlabs.com/AugerElectronSpectroscopy.php • http://www.wellesley.edu/Chemistry/Chris/AES.html • http://www.Ism.rutgers.edu/esca/principles.html • http://www.jhu.edu/chem/fairbr/surfacelab/aes.html

  19. ThankYouAll …

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