Lecture 27, 102908 - Announcements Chapter 7 Homework due...

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Announcements Chapter 7 Homework due Wednesday October 29 Chapter 8 Homework due Wednesday Nov. 5 Chapter 8 “Molecules and Materials” Chapter 9 “Energy and Chemistry” introduce Friday Next Exam November 12 on Chapters 7, 8 and 9
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Band Theory and Conductivity Order of increasing band gap: Metals < metalloids < nonmetals
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Semiconductors Energy Energy from an external source
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Semiconductors Conduction through doping DOPING: Carefully controlled trace amounts of another element are added Energy
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Semiconductors Conduction through doping Semiconductor: Silicon – 4 valence electrons Dopant: Phosphorous – 5 valence electrons Energy Phosphorous acts as a donor to the conduction band promoting conduction to a lower band gap
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Semiconductors Formation of n-type doped silicon
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Semiconductors Conduction through doping Semiconductor: Silicon – 4 valence electrons Dopant: Aluminum – 3 valence electrons Energy Phosphorous acts as an acceptor to the valence band promoting conduction due to a lower band gap
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Semiconductors Formation of p-type doped silicon
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Conduction at Junctions A p-n junction can act as a simple switch when the correct voltage polarity is applied .
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Intermolecular Forces Attractive forces betwee n molecules and ions. Determine bulk properties of matter. Much weaker than intramolecular forces. Covalent bonds and ionic bonds Intermolecular forces known as van der Waals forces Ion–dipole forces Dipole–dipole forces London dispersion forces Hydrogen “bonds.”
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Polar covalent bonds form between atoms with different electronegativity.
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This note was uploaded on 08/29/2010 for the course CHM 2045 taught by Professor Brant during the Fall '08 term at University of South Florida.

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Lecture 27, 102908 - Announcements Chapter 7 Homework due...

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