Lecture 16 - ENGR 4250 Advanced Materials Engineering...

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ENGR 4250 – Advanced Materials Engineering Lecture 16 Electrical Properties Ch 18; Callister 8/e Dr. A. Keshavarz - ENGR 4250U
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ISSUES TO ADDRESS. .. How are electrical conductance and resistance characterized ? What are the physical phenomena that distinguish conductors, semiconductors, and insulators? For metals, how is conductivity affected by imperfections, T , and deformation? Chapter 18: Electrical Properties Dr. A. Keshavarz - ENGR 4250U
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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. Fig. (a), (b), (c) from Fig. 18.0, Callister 7e . Fig. (d) from Fig. 18.27 (a), Callister 7e . (Fig. 18.27 is courtesy Nick Gonzales, National Semiconductor Corp., West Jordan, UT.) (b) (c) View of an Integrated Circuit 0.5mm (a) (d) 45 µ m Al Si (doped) (d) Dr. A. Keshavarz - ENGR 4250U
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Electrical Conduction Resistivity, ρ and Conductivity, σ : -- geometry-independent forms of Ohm's Law E : electric field intensity resistivity (Ohm-m) J : current density conductivity ρ = A I L V σ = 1 ρ Resistance: σ = ρ = A L A L R Ohm's Law: V = I R voltage drop (volts = J/C) C = Coulomb resistance (Ohms) current (amps = C/s) I e - A (cross sect. area) V L Dr. A. Keshavarz - ENGR 4250U
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Electrical Properties Which will conduct more electricity? Analogous to flow of water in a pipe So resistance depends on sample geometry, etc. D 2 D I VA RA = = ρ Dr. A. Keshavarz - ENGR 4250U
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Room T values (Ohm-m) -1 Selected values from Tables 18.1, 18.3, and 18.4, Callister 7e . Conductivity: Comparison Silver 6.8 x 10 7 Copper 6.0 x 10 7 Iron 1.0 x 10 7 METALS conductors Silicon 4 x 10 -4 Germanium 2 x 10 0 GaAs 10 -6 SEMICONDUCTORS semiconductors = ( - m) -1 Polystyrene <10 -14 Polyethylene 10 -15 -10 -17 Soda-lime glass 10 Concrete 10 -9 Aluminum oxide <10 -13 CERAMICS POLYMERS insulators -10 -10 -11 Dr. A. Keshavarz - ENGR 4250U
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What is the minimum diameter ( D ) of the wire so that V < 1.5 V? Example: Conductivity Problem 100m Cu wire I = 2.5A - + e - V Solve to get D > 1.87 mm < 1.5V 2.5A 6.07 x 10 (Ohm-m) 7 -1 100m I V A L R = σ = 4 2 D π Dr. A. Keshavarz - ENGR 4250U
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Conduction Electronic: Solids Ionic: Liquids Dr. A. Keshavarz - ENGR 4250U
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Electron Energy States Dr. A. Keshavarz - ENGR 4250U
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Metals ( Conductors ): -- Thermal energy puts many electrons into a higher energy state. Energy States:
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Lecture 16 - ENGR 4250 Advanced Materials Engineering...

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