Spring 2009 EE 710: Nanoscience and Engineering

Part 3: Carbon NanowiresImages and figures supplied from

Bhushan, Springer Handbook of Nanotechnology 2nd ed., Springer, 2007Ch 4 b D lh l d Ch 5 b Sh d CChapter 4 by Dresselhaus, et.al., and Chapter 5 by Shang and Cao

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

General RemarksGeneral Remarks• Wires with two quantum confined directions and 1 unconfined direction available for

l t i l d tielectrical conductions• Used for electrical conduction rather than tunneling transport• QM confinement often produces very different electrical, magnetic, and optical

properties than their bulk counterpartp p p• Enhanced nonlinearity of properties is available due to the 1-D DoS that allows

independent control in nanowires that is not available in their bulk counterparts• Drivers of this field

New R &D opportunities– New R &D opportunities– Smaller length scales used in semiconductor, optoelectronics, and magnetics industries– Development of biotech industry at the nanoscale

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JDW, UAHuntsville ECE, Spring 2009

Template SynthesisTemplate Synthesis• Common templates: Porous

alumina, nanochannel glass, ion track-etched polymers, mica p y ,films, di-block copolymers discussed in class

• Porous alumina is fabricated by electrochemical etching ofelectrochemical etching of alumina using by various acids

• Pore diamter controlled by Potential and acid concentration

<10 200– <10 nm – 200 nm – 109-1011 pores/cm2

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JDW, UAHuntsville ECE, Spring 2009

Alumina Templated FabricationAlumina Templated Fabrication

Pores filled using Electrochemical Deposition:Deposition:

Materials include: Bi, Co, Fe, Cu, Ni, Ag, Au, CdS C /CCdS, Cu/Co

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Electroplated NanowiresElectroplated Nanowires

Aft T l t R lAfter Template RemovalEx. Alumina etches in KOH

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Colloidal Electrodeposition of N i l d N dNanoparticles and Nanorods

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VLS Method for Nanowire S h iSynthesis

• Anisotropic crystal growth by vapor-liquid solid depositionliquid-solid deposition

• Adsorption from a gas onto surface to form a liquid followed by catalytic or high temperature crystallization at the tip

• Wire size reduction has been met in recent years by:– Maintaining single droplet metallic

clusters on individual nanotips at high c uste s o d dua a ot ps at gtemperatures

– Self-formation of metallic nano-islands when a strain layer is grown or heated on a non-epitaxial substrate

– Laser assisted VLS growth under non-equilibrium conditions

• Used to produce a wide variety of compound semiconductor nanowirescompound semiconductor nanowires

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JDW, UAHuntsville ECE, Spring 2009

Other TechniquesOther Techniques• Electrodeposition from the edges of

graphite crystal planes (note:graphite crystal planes (note: graphene conductance due to edge effects)

• Langmuir Blodget films

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Analysis TechniquesAnalysis Techniques

SEM TEM

STM

MFM

STM

Etc.

XRD10

JDW, UAHuntsville ECE, Spring 2009