ch18 - II. Functional Properties of Materials Chapters: 18...

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1 II. Functional Properties of Materials What properties of a material allow it to fulfill a particular function? Examples of devices requiring specific properties: magnetic latches electronic devices Optical fibers precision positioning devices computer chips Thermal tiles Chapters: 18 & 19
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2 www.memx.com ems.colorado.edu/c1.gen.intro/mems.shtml ¾ M icro E lectro M echanical S ystems ± A new technology for producing superminiature mechanical devices (motors and sensors). ± silicon devices ² mass produced like integrated circuits ¾ MEMS device used as a sensor: ± becomes integral part of an integrated circuit ± programmed to make decisions based on conditions sensed MEMS Devices
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3 Bell Labs ¾ An array of 256 microscopic mirrors. ¾ Each mirror is the size of the head of a pin. ¾ The mirrors tilt to steer lightwave signals from one optical fibre to another. MEMS Mirror Array
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Electronic Devices: Power Mac G5
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Inside the box…
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Venturing deeper…
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Semiconductors: The Brains of the Operation
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The Brains of the Operation
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Making it Possible
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10 Scanning electron microscope images of an IC An elemental distribution map showing location of Si: Si shows up as light regions. An elemental distribution map showing location of Al Al shows up as light regions. 0.5mm 45 μ m Al Si (doped) Fig. (a), (b), (c) from Fig. 18.0, Callister 6e . From Fig. 18.25, Callister 6e . (Fig. 18.25 is courtesy Nick Gonzales, National Semiconductor Corp., West Jordan, UT.) An Integrated Circuit
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11 Electronic Materials The race for faster chips Graph: Intel website: presentation “towards the 65nm node” , Yokohama Japan
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12 Electrical Properties of Solids Chapter 18 What you should understand by the end of this chapter: ± The physical basis for electrical conductivity in metals, semiconductors and ceramics. This involves band theory . ± The effect of temperature on conductivity for each class of material. ± The importance of pure Si to semiconductor technology. ± The role of dopants in semiconductors.
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13 Fundamentals ¾ Ohm’s Law: V = I R or J = σ ε ¾ Resistance ( R ) depends on the configuration of the system. ¾ The related material property is resistivity ( ρ ). ¾ Conductivity is related to resistivity: A l R = ρ ρ σ 1 =
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14 Conduction Mechanisms ¾ electronic ± flow of electrons (or holes) ± This dominates in most electronic device applications. ¾ ionic ± diffusion of charged ions ± This is important for high temperature and specialized devices. ² e.g. fuel cells
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15 Band Structure ¾ electronic conduction ± depends strongly on how electrons fill orbitals in an atom band structure ¾ Pauli exclusion principle ± each electron occupies an independent state isolated atoms orbital states solid (many atoms) energy bands
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16 Band Structure ¾ simple picture of band structure ¾ Think of a solid with N atoms: s shell N states (2 electrons / state) p shell 3 N states d shell 5 N states
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17 Conductor or Insulator?
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ch18 - II. Functional Properties of Materials Chapters: 18...

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