hw2_solution - ECE 440 Homework 2 Solution Due: Friday,...

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ECE 440 Homework 2 Solution Fall 2009 Due: Friday, September 11, 2009 1. Gold, one of the best conductors, has a face-centered cubic lattice. The lattice constant is 4.08Å. The force holding the lattice together is the metallic bonding, i.e. an interaction between positive ion cores and surrounding free electrons in the so-called electron sea. Assume that each gold atom contributes one electron to the electron sea. Determine the free electron density in gold, and compare that to the electron density of intrinsic silicon, which is 1.5x10 10 /cm 3 . Answer: We can compute using what we know about FCC: 3 22 3 0 10 9 . 5 1 * 08 . 4 * ) 4 ( cm e atom electron A cell unit cell unit atoms n e × = = Or using the properties of gold that we know: m V n atom a e ρ = = Where: mole atoms number Avogadro atoms per electrons of number m Kg mole gram Mass Atomic m a atoms 23 3 3 10 022 . 6 1 10 3 . 19 7 . 196 × = = = = × = = = 3 22 23 3 3 10 9 . 5 197 . 0
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This note was uploaded on 10/14/2009 for the course ECE 440 taught by Professor Lie during the Fall '09 term at University of Illinois at Urbana–Champaign.

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hw2_solution - ECE 440 Homework 2 Solution Due: Friday,...

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