TAILIEUCHUNG - Microscopy and Surface Analysis 2

Surface contamination: – The obvious contamination/alteration of surfaces that can be the result of less-than careful sample preparation – Solid surfaces can adsorb gases: At 10-6 torr, a complete monolayer of a gas (. CO) takes just 3 seconds to form. At 10-8 torr, monolayer formation takes 1 hour. – Most studies are conducted under vaccuum – although there are newer methods that don’t require this. | a W VILLANOVA UNIVERSITY Microscopy and Surface Analysis 2 Lecture Date March 17th 2008 Reading Assignments for Microscopy and Surface Analysis Skoog Holler and Nieman Chapter 21 Surface Characterization by Spectroscopy and Microscopy Hand-out Review Article C. R. Brundle J. F. Watts and J. Wolstenholme X-ray Photoelectron and Auger Electron Spectroscopy in Ewing s Analytical Instrumentation Handbook 3rd Ed. J. Cazes Ed. Marcel-Dekker 2005. 1 Introduction to the Solid State In solids atomic and molecular energy levels broaden into bands that in principle contain as many states as there are atoms molecules in the solid. Bands may be separated by a band gap with energy Eg . Cox The Electronic Structure and Chemistry of Solids Oxford University Press 1987. C. Kittel Solid-state Physics 7thEd Wiley 1999. W. A. Harrison Electronic Structure and the Properties of Solids Dover 1989. Energy Bands in the Solid State Bands are continuous and delocalized over the material Band widths are determined by size of orbital overlap Insulator Semiconductor Conductor The highest-energy filled band which may be only partially filled is called the valence band The lowest-energy empty band is called the conduction band . Cox The Electronic Structure and Chemistry of Solids Oxford University Press 1987. C. Kittel Solid-state Physics 7thEd Wiley 1999. W. A. Harrison Electronic Structure and the Properties of Solids Dover 1989. 2 The Workfunction A Barrier to Electron Emission How does the electronic arrangement in solids affect surfaces In particular how can an electron be removed For some electron being removed its energy just as it gets free is EV The energy required to remove the electron is the workfunction Ộ typically several eV . Cox The Electronic Structure and Chemistry of Solids Oxford University Press 1987. C. Kittel Solid-state Physics 7thEd Wiley 1999. W. A. Harrison Electronic Structure and the Properties of Solids Dover 1989. The Workfunction A Barrier to Electron .

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