electrical properties of defects in carbon nanotubes brett goldsmith uc irvine department of physics...
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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