Electrical Properties of Defects in Carbon Nanotubes

Brett Goldsmith

UC Irvine

Department of Physics and Astronomy

Collins Group

SPM Studies of Nanotubes

• There have been a number of studies to characterize the frequency and effects of defects in nanotubes.

• Some unanswered questions still remain:– Is gate dependence only based on

band structure?– Are high resistance devices always

dominated by contact effects?

Freitag et al, PRL 89 (21) 2002

source electrode drain electrode

nanotube

Insulator

Gate

Nanotube Transistors

Nanotube Current vs Gate Voltage

0

0.1

0.2

0.3

-10 0 10Gate Voltage (V)

Curr

ent (m

icro

Am

ps)

d

Nanotube Current vs Gate Voltage

0

0.1

0.2

0.3

-10 0 10Gate Voltage (V)

Curr

ent (m

icro

Am

ps)

d

Scanned Gate Microscopy Setup

Source

VSD

VG

Vtip

Drain

1 MΩ

apply AC+DC back gate

lock in on AC current here

apply DC “tip gate”

SGM – Semiconducting Nanotube

3 VDC back Gate

SGM – Gate Dependance

5 VDC back Gate

SGM – Metallic Tube

Kelvin Probe Microscopy

Source

VSD

VG

Vtip

Drain

1 MΩ

DC voltage across nanotubeAC voltage between tip and entire sample

)( tSinVVConstF ACDC

Local Voltage Drops

900 kΩ570 kΩ

? ?

Changing the Voltage Profile

2V

3V

Combining SGM and KFM

Summary

• metallic nanotubes can have local gate dependence

• gate sensitive regions correspond to points of local voltage drops

Dr. Phil Collins

Dr. Yuwei Fan

Nathan EmmottDerek Kingrey

Alex KaneBucky Khalap

Jorge GuerraKevin Loutherback

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

ACS-PRF