2材料物理课件_(14).ppt
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1、Nano-devices,1, Nano-scale devices 2, Molecular devices 3, Devices with nano-materials,Nanoscale devices,Nano-computers,Electronic Nanocomputers Quantum mechanical tunneling effect Chemical Nanocomputers Stores information in the chemical bonds: DNA etc. Mechanical Nanocomputers Moving molecular sca
2、le parts: how to assemble ? Quantum computer Each bit of information as a quantum state: spins etc,Nanoelectronic Devices,Solid state nanoelectronic devices,Quantum dots “artificial atoms” (QD): 0-D Resonant Tunneling Devices (RTD, RTT): 1- or 2-D Single Electron Transistor (SET): 3-D Quantum Cellul
3、ar Automata (QCA) Magnetic Random Access Memory (MRAM),Islands confine electrons,Microelectronic Transistor: structure, operation, obstacles to miniaturization,Function of transistor - Two state device or switch - Amplification,n- and p-type Silicon Semiconductor,p-type B doped Hole carrier n-type P
4、, As doped Electron carrier,B,P,Depletion region,- + - + - +,+,-,EF,p n,Some of the free electrons in the n-region diffuse across the junction and combine with holes to form negative ions. In so doing they leave behind positive ions at the donor impurity sites.,Structure and Operation of MOSFET,I-V
5、Charateristics of n-type MOSFET,VGate = 5V 4 V 3 V 2 V,Obstacles to Further Scaling of FET,High electric field due to bias voltage to short distance - avalanche break down due to high kinetic energy electrons - tunneling through insulating layers Heat Dissipation of transistors due to limited thermo
6、dynamic efficiency - molecular scaled device: as much heat as gunpowder Vanishing bulk properties and nonuniform dopant concentration - few dopant atoms in nano scale: functioning as transistor? - quantum mechanical effect Shrinkage of depletion regions(0.1mm) - current leakage Shrinkage and unevene
7、ss of the thin oxide layer - tunneling,Resonant Tunneling Device (RTD),Single Electron Transistor - Island potential is capacitively controlled by the gate. - Coulomb blockade is overcome by changing the gate voltage Advantage - ultra low power operation - fast,e,source,drain,gate,Island,I,V,Vg =1V,
8、Vg =-1V,Single Electron Transistor,Coulomb Blockade Effect,Coulomb Blockade Effect Quantum tunneling of electron between source and drain can be blocked If the charging energy Ec = e2/2C kT DE = eV Ec R1) - Current steps at e/2C2 + n(e/C2),e,source,drain,gate,Island,N= 2 1 0,N= 2 1,v,I,V,on,off,R1 R
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- 材料 物理 课件 14
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