Home > Uncategorized > Introduction to Solid State Chemistry Lecture 13: Semiconductors

Introduction to Solid State Chemistry Lecture 13: Semiconductors

Overview
Okay folks, put a muffler on that. Class average on the test was 66. Today’s lecture is 51 minutes

Details
Metallic solids have high electrical conductivity, high thermal conductivity, luster, ductility. Paul Drude modeled a solid as a sea of delocalized mobile valence electrons. Cations are ordered.

Bloch applied QM to solids. Atoms are arranged in arrays or xytls. Apply SHE, we get a periodic answer and wavelike properties. Allows electron mobility.

Heitler and London. A postdoc is slave labor. Apply LCAO-MO to large aggregates.

From:
-a*
-a
to many energy levels, any sigma bonds, a vertiable sea of them. We get a “band” of states. Populate it.

Cu 3d10s1

0.25 eV is 300 K.

Be 2s2
C 2s2 2p2 to 2sp3
The gap from a to a* is 5 eV from the valence band to the conduction band. Bandgap.

Visible light is 1eV. For Si, sp3, n=3.

BG>3 eV Insulator
BG<1 semiconductor
BG=0 metal

color comes from promotion and re-emission.

E = hc/lambda = hf

Absorption edge

229 nm for carbon

for silicon 1125nm,

Applying a potential, electrons are promoted from teh bonding orbitals to the antibonding orbitals.

Impregnant silicon billets with irradiation. Truck MIT.

1 eV is 11600K

Broken bonds are holes. The number of electrons equals the number of holes.

conductivity = population x charge x mobility

Bandgap and the periodic table:
C 5.4
Si 1.1
Ge 0.72
Sn 0.8
Pb 0

Tin is used in night vision. Comes in white and dark flavors.

Review
IE eV, electron acceptor, nonmetal.

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  1. July 8, 2017 at 7:58 pm

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