Spring 2009 EE 710: Nanoscience and Engineering

Part 7: Introduction to NanoelectronicsImages and figures supplied from

Goddard, et.al, Handbook of Nanoscience, Engineering, and Technology, CRC Press, 2004d h f d i di dand other refereed sources as indicated

Instructor: John D. Williams, Ph.D.Assistant Professor of Electrical and Computer Engineering

A i t Di t f th N d Mi D i C tAssociate Director of the Nano and Micro Devices CenterUniversity of Alabama in Huntsville

406 Optics BuildingHuntsville, AL 35899Ph (256) 824 2898Phone: (256) 824-2898

Fax: (256) 824-2898email: williams@eng.uah.edu 1

Overcoming the limitations of lid h l icurrent solid state technologies

• Short term: – scale factor reduction in silicon and silicon hybrid electronics

• Size reduction increases the frequency and capacitance of silicon gate electronics, however it also increases heat production and resistive losses

Requires new heat dissipation solutions– Requires new heat dissipation solutions – 20 nm TFTs require new dielectric material solutions for gate materials

– Integration of photonic structures for optical computing• Photonic waveguides reduce heat for busses, but not on chip computing• Direct integration with on chip computing requires new material processing

parameters to develop efficient electronic/optical signal conversion

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JDW, UAHuntsville ECE, Spring 2009

Overcoming the limitations of lid h l icurrent solid state technologies

• Long term– Molecular electronics

• Has already been used to demonstrate transistors and simple electronic circuits• Bottom up assembly of molecules over large areas capable of generating sufficient gain

and low power operation may provide an alternative to silicon solid state devicesM b bl th t th t t ill b i t t d i t d ili t h l i t• More probable that these structures will be integrated into modern silicon technologies to reduce cost and increase yield.

– Spintronics• Magnetic gate technologies ranging from magnetic domain devices to single atomic spin

systems integrated with molecular or quantum electronicssystems integrated with molecular or quantum electronics– Quantum computing (multiple approaches)

• Single electron transistors• Atomic traps• Ion traps• Ion traps• NMR devices• Each method provides multiple different signal states. Unlike silicon which is simply on-off• All of these have demonstrated the ability to produce a quantum based switch with gain,

however the ability to determine exact states and design architectures by which one can y g yrecord all of the possible states, allowing computing to be performed in an entirely new realm

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JDW, UAHuntsville ECE, Spring 2009

Molecular ElectronicsMolecular Electronics • Quantum cellular automata

t d t t i ll ll l t i d ti i f 1– quantum dots: typically small electronic conducting regions of 1 um or less with a variety of geometries and dimensions

– Small dimensions quantify the electron energies• Imagine 4 quantum dots in a square array are placed in a cell such g q q y p

that electrons may tunnel between the dots but are unable to leave the cell

• When the cell is biased by excess electrons, then Coulomb repulsion will force the electrons to occupy dots on opposite cornersrepulsion will force the electrons to occupy dots on opposite corners

• The two ground state polarizations are energetically equivalent and can be labeled in a logic circuit as “0” or “1”

• The logic state of one dot can be flipped by applying a negative t ti l f th i d d tpotential near one of the occupied dots

Vo -Vo 4

JDW, UAHuntsville ECE, Spring 2009

Binary WireBinary Wire

• If we string several quantum dot wellsIf we string several quantum dot wells together then:

Vo

“Output 0”“Input 0”

-Vo

“Output 1”“Input 1” 5

JDW, UAHuntsville ECE, Spring 2009

QCA InvertersQCA Inverters

V-Vo“Output 0”

“Input 1”

“Input A 1”p

“Input B 0” “O tp t 1”

“Input C 1”

Input B 0 “Output 1”

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JDW, UAHuntsville ECE, Spring 2009

Issues with QCAsIssues with QCAs

Zengxiao Jin Thesis 2006Results taken at < 1 Kelvin

A. Palaniancoan et.al at 0.3 Kelvin

• Further reading:

Kelvin

g– Quantum dot cellular automata, GL Snider, Microelectronic Engineering 1999– The Development of Design Tools for Fault Tolerant Quantum Dot Cellular Automata Based Logic, CD Armstrong, – Testing reversible 1-D arrays of QCA arrays for Multiple Faults by J Huang etal. IEEE Proceedings 2007– Quartz sensor array using mesoporous silica hybrids for gas sensing applications, A. Palaniappan. IEEE Proceedings, 2005– A QCA cell in silicon-on-insulator technology: theory and experiment, M Macuuchi, Superlattices and Microstructures 2003– FABRICATION AND MEASUREMENT OF MOLECULAR QUANTUM CELLULARAUTOMATA (QCA) DEVICE, Zengxiao Jin

Thesis 2006Thesis 2006

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JDW, UAHuntsville ECE, Spring 2009

Crossbar ArraysCrossbar Arrays• In 1998, researchers reported a massively parallel experimental computer containing

220 000 d f t li th t d b k d f th i l CPU t i it220,000 defect lines that crossed back and forth across a single CPU to increase its speed by 100 times. This modified CPU to as Teramac achitecture.

• In molecular based Teramac computers, wires cross back and forth to link log circuit addresses on the chip.

• Today this is performed using carbon nanowires to link various molecular and solid state transistors

• Logic and Memory With Nanocell Circuits. CP Husband, IEEE Transactions on Electronic DevicesElectronic Devices

Molecule used as the nanoparticle basis within a cell 8

JDW, UAHuntsville ECE, Spring 2009

Single Nanocell with multiple nanoparticle components all strung together

To create n units of each individual cellTo create n units of each individual cell with enough gain between them to drive signals throughout a computer

Result is a working nano architecture with 1010 some odd calculations

Calculation schematic from a single array of nanoparticles within 1 cell 9

JDW, UAHuntsville ECE, Spring 2009

Extending Cross Bar Arrays to M l i l GMultiple Gates

• Nanocell Logic Gates for Molecular Computing, J. Tour, IEEE T ti N t h l 2002IEEE Transactions on Nanotechnology 2002

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JDW, UAHuntsville ECE, Spring 2009

Crossbar ArraysCrossbar Arrays• Attaching and wiring components together• Jonathan Greene, Ultra-dense nano- and molecular-electronic circuits,

Thesis, 2007 Taken from Chapter 4. The entire dissertation is worth reading

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JDW, UAHuntsville ECE, Spring 2009