lecture_16_Surface Characterization by Spectroscopy

lecture_16_Surface Characterization by Spectroscopy -...

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Lecture #16 Surface Characterization by Spectroscopy Reading: Chapter 21, page 589 – 621 ; Problems: 21-2,4,5. • Basics of surface science; • General technique in surface spectroscopy; • X-ray photoelectron spectroscopy; • Auger electron spectroscopy;
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Surface science • Surface --- the boundary layer between a solid and a vacuum, gas, or liquid. • Surface differs substantially from the interior of the solid both in chemical composition and physical properties. • As the dimension of a solid becomes smaller (in nanometer range), the ratio of surface atoms increases dramatically. For a 3 nm CdSe nanoparticle, ~ 50% atoms are on surface, while for a large bulk material, the surface layer is generally only a tiny fraction of the total solid. • Surface characterization is crucial for explaining many surface phenomena and improving the properties of many solid materials. Typical examples include 1. heterogeneous catalysis, 2. semiconductor thin film technology (e.g. computer chips), 3. corrosion and adhesion mechanisms, 4. metal/alloy surface, 5. embrittlement properties, 6. behavior and function of biological membranes.
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Types of surface measurement Two major instrumentation techniques for surface analysis: 1. Surface spectroscopy: a) identifying the surface chemical species and determining the concentrations; b) providing both qualitative and quantitative (less used) information about the composition of surface layer (a few to a few tens of Å depth). 2. Surface microscopy: a) imaging the surface and determining the morphology, physical properties and features at different size scale (nanometers to micrometers); b) 3-dimensional surface structure with high resolution (see next lecture).
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Spectroscopic surface methods • Some common types of surface spectroscopic methods are listed in Table 21- 1, page 591. Only XPS and AES are covered in this lecture. • General techniques in surface spectroscopy (Figure 21-1): primary beam --- made up of photons, electrons, ions, or neutral molecules , secondary beam --- also consisting of photons, electrons, ions, or neutral molecules bounced from the solid surface, but not necessary the same as the primary beam. The secondary beam is a result of scattering, sputtering, or emission.
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This note was uploaded on 05/15/2010 for the course CHEM 434 taught by Professor None during the Spring '07 term at University of Michigan-Dearborn.

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lecture_16_Surface Characterization by Spectroscopy -...

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