Figure 16.31: Two-dimensional representations of (a) a quartz crystal and (b) a quartz glass.

Figure 16.31: Two-dimensional representations of (a) a quartz crystal and (b) a quartz glass. Figure 16.28: The p orbitals (a) perpendicular to the plane of th carbon ring system in graphite can combine to form (b) an extensive pie bonding network. Copyright Houghton Mifflin Company. All rights reserved. 16a 1 Copyright Houghton Mifflin Company. All rights reserved. 16a 2 The Electronic Configuration of a Magnesium Atom Orbital energy levels n 3 3 l 0 0 m l 0 0 m s +1/2-1/2 Empty 3p orbitals in Mg valence shell Mg: Ne)3s 2 3s 2s 1s 3p 2p Copyright Houghton Mifflin Company. All rights reserved. 16a 3 Copyright Houghton Mifflin Company. All rights reserved. 16a 4 1

Figure 16.24: A representation of the energy levels (bands) in a magnesium crystal Figure 16.27: Partial representation of the MO energies in (a) diamond and (b) a typical metal Copyright Houghton Mifflin Company. All rights reserved. 16a 5 Copyright Houghton Mifflin Company. All rights reserved. 16a 6 Electron sea model for metals Bonding in Solids Metallic Solids Copyright Houghton Mifflin Company. All rights reserved. 16a 7 Copyright Houghton Mifflin Company. All rights reserved. 16a 8 2

Band structure of Semiconductors Band Diagram: Semiconductor with No Doping T > 0 Conduction band (Partially Filled) E F Valence band (Partially Empty) E C E V At T = 0, lower valence band is filled with electrons and upper conduction band is empty, leading to zero conductivity. Fermi energy E F is at midpoint of small energy gap (<1 ev) between conduction and valence bands. Copyright Houghton Mifflin Company. All rights reserved. 16a 9 At T > 0, electrons thermally excited from valence to conduction band, leading to measurable conductivity. Copyright Houghton Mifflin Company. All rights reserved. 16a 10 Silicon Crystal Doped with (a) Arsenic and (b) Boron Figure 16.33: Energy-level diagrams for (a) an n-type semiconductor and (b) a p-type semiconductor. Copyright Houghton Mifflin Company. All rights reserved. 16a 11 Copyright Houghton Mifflin Company. All rights reserved. 16a 12 3

pn junction Figure 16.34: The p-n junction involves the contact of a p-type and an n-type semiconductor. Copyright Houghton Mifflin Company. All rights reserved. 16a 13 Copyright Houghton Mifflin Company. All rights reserved. 16a 14 PN Junction - 7 PN Junction with Applied Potential No current, Barrier Larger Current Flows, Barrier Smaller Copyright Houghton Mifflin Company. All rights reserved. 16a 15 Copyright Houghton Mifflin Company. All rights reserved. 16a 16 4

Herbert Kroemer Copyright Houghton Mifflin Company. All rights reserved. 16a 17 Copyright Houghton Mifflin Company. All rights reserved. 16a 18 Solar Cells p-type n-type Electron Hole Photons Load Light Amplification by Stimulated Emission Radiation Copyright Houghton Mifflin Company. All rights reserved. 16a 19 p-n Junction under Illumination Copyright Houghton Mifflin Company. All rights reserved. 16a 20 5

Solar Panels Photovoltaic Cells Schematic of a Photovoltaic (solar) cell Copyright Houghton Mifflin Company. All rights reserved. 16a 21 Copyright Houghton Mifflin Company. All rights reserved. 16a 22 A schematic of two circuits connected by a transistor. Photolithography to make semiconductor integrated circuits Copyright Houghton Mifflin Company. All rights reserved. 16a 23 http://britneyspears.ac/physics/fabrication/photolithography.htm Copyright Houghton Mifflin Company. All rights reserved. 16a 24 6

(a)-(h) The steps for forming a transistor in a crystal of initially pure silicon. (a)-(h) The steps for forming a transistor in a crystal of initially pure silicon. (cont d) Copyright Houghton Mifflin Company. All rights reserved. 16a 25 Copyright Houghton Mifflin Company. All rights reserved. 16a 26 Semiconductors key points to remember Figure 16.24: A representation of the energy levels (bands) in a magnesium crystal Band structure: Valence band gap conduction band DOPING: Group V n type, Group III p type n-p junctions Devices: (LED, laser, transistor, solar cell) Copyright Houghton Mifflin Company. All rights reserved. 16a 27 Copyright Houghton Mifflin Company. All rights reserved. 16a 28 7

Band structure of Semiconductors Semiconductors key points to remember Band structure: Valence band gap conduction band DOPING: Group V n type, Group III p type n-p junctions Devices: (LED, laser, transistor, solar cell) Copyright Houghton Mifflin Company. All rights reserved. 16a 29 Copyright Houghton Mifflin Company. All rights reserved. 16a 30 Silicon Crystal Doped with (a) Arsenic and (b) Boron Semiconductors key points to remember Band structure: Valence band gap conduction band DOPING: Group V n type, Group III p type n-p junctions Devices: (LED, laser, transistor, solar cell) Copyright Houghton Mifflin Company. All rights reserved. 16a 31 Copyright Houghton Mifflin Company. All rights reserved. 16a 32 8

pn junction Semiconductors key points to remember Band structure: Valence band gap conduction band DOPING: Group V n type, Group III p type n-p junctions Devices: (LED, laser, transistor, solar cell) Copyright Houghton Mifflin Company. All rights reserved. 16a 33 Copyright Houghton Mifflin Company. All rights reserved. 16a 34 C 60 crystals Ionic liquids Copyright Houghton Mifflin Company. All rights reserved. 16a 35 Copyright Houghton Mifflin Company. All rights reserved. 16a 36 9