ch12_electrical

ch12_electrical - CHAPTER 12: ELECTRICAL PROPERTIES 12.1...

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12.1 Introduction How a material respond to the application of an electric field Electrical resistance (by electrons) Electron energy band structure of the material Metals, semiconductors and insulators Dielectric characteristics of insulating materials Ferroelectricity and piezoelectricity For semiconductors, how is conductivity affected by impurities (doping) and T? 1 CHAPTER 12: ELECTRICAL PROPERTIES
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2 Scanning electron microscope images of an IC: A dot map showing location of Si (a semiconductor): --Si shows up as light regions. A dot map showing location of Al (a conductor): --Al shows up as light regions. 0.5mm 45 μ m Al Si (doped) Fig. (a), (b), (c) from Fig. 18.0, Callister 6e . Fig. (d) from Fig. 18.25, Callister 6e . (Fig. 18.25 is courtesy Nick Gonzales, National Semiconductor Corp., West Jordan, UT.) (a) (b) (c) (d) VIEW OF AN INTEGRATED CIRCUIT
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3 • 12.2 Ohm's Law: V = I R in most cases V = V = V 2 – V 1 voltage drop (volts) resistance (Ohms) current (amps) V I e - A (cross sect. area) L Resistivity, ρ and Conductivity, σ : --geometry-independent forms of Ohm's Law    V L = I A ρ E: electric field intensity resistivity (Ohm-m) J: current density    σ = I ρ conductivity Resistance:    R = ρ L A = L A σ I. ELECTRICAL CONDUCTION
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Polystyrene <10 -14 Polyethylene 10 -15 -10 -17 Silver 6.8 x 10 7 Copper 6.0 x 10 7 Iron 1.0 x 10 7 METALS Silicon 4 x 10 -4 Germanium 2 x 10 0 GaAs 10 -6 SEMICONDUCTORS Soda-lime glass 10 -10 Concrete 10 -9 Aluminum oxide <10 -13 CERAMICS POLYMERS conductors semiconductors insulators 4 Room T values (Ohm-m) -1 Selected values from Tables 18.1, 18.2, and 18.3, Callister 6e . 12.3 Electrical Conductivity
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5 Problem 12.2, p. 524, Callister 2e : What is the minimum diameter (D) of the wire so that V < 1.5V? 100m Cu wire I = 2.5A - + e - V    R = L A σ = V I < 1.5V 2.5A 6.07 x 10 (Ohm-m) 7 -1    π D 2 4 100m Solve to get D > 1.88 mm EX: CONDUCTIVITY PROBLEM
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12.4 Electronic and Ionic Conduction Electronic conduction (by electrons) Ionic materials, ionic donduction
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6 Metals: -- Thermal energy puts many electrons into a higher energy state. + - net e - flow Energy States: -- the cases below for metals show that nearby energy states are accessible by thermal fluctuations. Energy filled band filled valence band empty band filled states 12.5 Energy Band Structure in Solids filled band Energy partly filled valence band empty band GAP
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Insulators: --Higher energy states not accessible due to gap. Semiconductors: --Higher energy states separated by a smaller gap. Energy filled band filled valence band empty band filled states GAP Energy filled band filled valence band empty band GAP ? AND SEMICONDUCTORS
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This note was uploaded on 03/08/2010 for the course CHEN 313 taught by Professor Seminario during the Fall '07 term at Texas A&M.

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ch12_electrical - CHAPTER 12: ELECTRICAL PROPERTIES 12.1...

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