Signatures of Chemical Defects in

Carbon Nanotube Electronic Devices

Brett GoldsmithCollins LabDepartment of Physics and Astronomy

A broad look at defects

Types of Devices (all CVD SWCNT):

•pristine nanotube with nearly ballistic conduction

•Growth defects in unmodified nanotubes

•Mild oxidation (no missing carbon)

•Harsh oxidation (missing carbon)

Tools to Study CNT Defects

•Scanning Tunneling MicroscopyIshigashi, PRL. November, 2004

•Chemical LabelingFan, Nature Materials. December, 2005

•Scanning Gate MicroscopyBachtold, PRL. June, 2000

•Kelvin Force MicroscopyBachtold, PRL. June, 2000

Fan, Nature Materials. December, 2005

Scanning Probe Microscopy - KFM

Kelvin Force Microscopy (KFM):• Records forces between tip and

sample• Measures Surface Potential• Allows indirect measurement of

local resistance

Source

VSD

Vtip

Drain

VF

Source

Drain

Scanning Probe Microscopy - SGM

Scanned Gate Microscopy (SGM):• Records current through the

nanotube circuit• Measures local field sensitivity• Shows where the device is “gate

sensitive”

Source

VSD

Vtip

Drain

VF

topography topography + SGM

Growth Defects - KFM

Ballistic Nanotube Nanotube with Growth Defects

Ballistic Nanotube

Growth Defects – KFM detail

Nanotube with Growth Defects:

Growth Defects - SGM

topography

topography + SGM

Defect Creation on Nanotubes

WE

RE

CE

Vg

Many ways to create defects:

• Mechanical• Chemical• Irradiation• Electrochemical

Jaan Mannik V18.7

Basic Effects of Oxidation

-6000

-4000

-2000

0

2000

4000

6000

Cur

rent

(na

noA

mps

)

-0.50 -0.25 0.00 0.25 0.50Voltage

Pristine Nanotube

Basic Effects of Oxidation

-200

-100

0

100

200

Cur

rent

(na

no A

mps

)

-0.50 -0.25 0.00 0.25 0.50Voltage

Weak DefectWeak Oxidation

Basic Effects of Strong Oxidation

-4

-2

0

2

4

Cur

rent

(na

noA

mps

)

-0.50 -0.25 0.00 0.25 0.50Voltage

Strong DefectStrong Oxidation

Mild Oxidation - SGM

topography topography + SGM

One SWNT after Progressively Harsh Treatments

Surface Potential along as-grown CNT:

Surface Potential after mild oxidation:

Surface Potential after strong oxidation:

Weak Defects - KFM

Ballistic Nanotube Mildly Oxidized Nanotube

Summary

Microscopy techniques such as KFM and SGM show that oxidation and growth defects have similar effects on CNT circuits.

Engineering the Microworld at The University of California, IrvineUCI Integrated Nanosystems Research Facility

Dr. Yuwei FanDr. Jaan MannikBrett GoldsmithAlex KaneDerek KingreyBucky Khalap

Kevin LoutherbackFatima AlimYasser Elliasal

ACS-PRF