lec8 - ENGR 111 Lecture 10 Reading Chapters 25 Class notes...

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ENGR 111 Lecture 10 Reading: Chapters 25 Class notes, hyperlinked websites
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Conductors, Semiconductors, Insulators z Metals conduct electricity at room temperatures z Insulators do not conduct electricity z Semiconductors are in between { Normally not-conductive, but can be made to conduct { They can be “doped” to conduct electricity
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What’s the difference? z An atom consists of nucleus and electrons z Electrons orbit the nucleus in “shells” z The outer shell electrons allow bonds between atoms –molecules, crystals… z In metals, these outer shell electrons can easily float away from the atom { Form an electron “gas” between atoms { These free electrons conduct electricity
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What’s the difference? z The electrons are in two energy bands, valence band and conduction band Insulator Semiconductor Metal Conduction band Valence band
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What’s the difference? z In metals, at room temperature, there are many free electrons (Aluminum, Copper) z In Semiconductors, there are very few free electrons (Silicon, Germanium) { But, the energy needed to become free (move to the conduction band) is not high z In Insulators, the energy needed to pry electrons free is very high (Diamond)
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This note was uploaded on 03/26/2008 for the course ENGR 111 taught by Professor Walker during the Fall '07 term at Texas A&M.

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lec8 - ENGR 111 Lecture 10 Reading Chapters 25 Class notes...

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