ECE474S11_Lec05_21Jan11

# ECE474S11_Lec05_21Jan11 - ECE 474 Principles of Electronic...

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ECE 474: Principles of Electronic Devices Prof. Virginia Ayres Michigan State University [email protected]

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V.M. Ayres, ECE474, Spring 2011 Lecture 05: Chapter 01: quantify physical structures of crystal systems that are important for devices: ± Cubic systems: bcc, fcc, diamond, zinc-blende ¾ Number of atoms in unit cell ¾ Lattice constant “a” ² Volume density of atoms ² Packing fraction ² Nearest neighbor distances ² lattice-matched compositions for devices ² Predicted density ² wafer synthesis from melt Examples of each
V.M. Ayres, ECE474, Spring 2011 Density : Density is measured grams/cm 3 . WHY Density: It is very useful to have a theoretical ideal value for the density of a new nanostructure. Nanostructures can be hard to “weigh”.

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V.M. Ayres, ECE474, Spring 2011 Density : Density is measured grams/cm 3 . Calculate the Density from the Unit cell volume, # of atoms inside the Unit cell, atomic weight(s) of each type of atom and Avogadro's number. Avogadro’s number: 6.02 x10 23 atoms/mole Atomic weight (also called mass number): # grams/mole Therefore: Atomic weight/Avogadro’s number = grams/atom Therefore: volume cell Unit atoms # atom grams Density =
V.M. Ayres, ECE474, Spring 2011 Example: Density of Cu (fcc) =? 8 x 1/8

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ECE474S11_Lec05_21Jan11 - ECE 474 Principles of Electronic...

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