Diodes Properties of
SWNT Networks
Bryan Hicks
Diodes and Transistors
An ever increasing number in an ever decreasing area
Why Carbon Nanotubes?
• Ballistic transport –Low power
• No chemical passivation necessary allows for
a variety of different insulators
• Current densities of 109 A/cm2 vs. 103 A/cm2
for silicon
• Huge mobility for high speed devices
• Can be semi-conducting or metallic
Carbon Nanotube Networks
• Random networks of
tubes
• Low resistance at
CNT junctions
• No processing
necessary
• 1/3 metallic 2/3
semiconducting
• Have properties of
both metals and
semiconductors
Fabrication Process
• Deposit Al and Au
electrodes on to a
Si02/Si chip with SWNT
networks
• Wire bond the
electrodes to a chip
carrier
Actual Devices
Current
Rectification
Properties
Maximum Current Capacities: Device 1: 8 μA &
Device 2: 22 μA
On/off ratios: Device 1: 20 & Device 2: 5
Devices 1 and 2
Current (µA)
25
20
15
10
5
0
-5
-10
Device 1
Device 2
-4
-2
0
Voltage (V)
2
4
Current Rectification Properties
Device 3
Current (µA)
800
600
400
200
0
-200
-4
-2
0
Voltage (V)
2
Maximum Current Capacities: 678.9 μA
On/off ratios: 27
4
Current Rectification Properties
Device 4
1000
Current (µA)
800
600
Trial 1
Trial 2
400
200
0
-200
-4
-2
0
2
4
Voltage (V)
Maximum Current Capacities: 840 μA
On/off ratios: 108
Current Rectification Properties
Device 5
Current (uA)
1000
500
0
-500
-1000
-4
-2
0
Voltage (V)
2
Maximum Current Capacities: 840 μA
On/off ratios: ??
4
Gate Voltage Characterization
Gate Voltage Dependence
Current (nA)
650
550
450
350
250
-12
-8
-4
0
4
Gate Voltage (V)
•Current decreases as carriers are removed
•Current increases as carriers are
introduced
•The hysteresis seen is due to trapping seen
in other CNT transistors as well
8
12
Summary
• Carbon Nanotube Networks present an
economic way to incorporate CNT properties
into macroelectronics
• Current Rectification seems to be a product of
contact resistance and is often lost when
various scans are made.
Sources
• C. Lu, L. An, Q. Fu, J. Liua, H. Zhang and J. Murduck. Appl.
Phys. Lett. 88, 133501 (2006)
• P. Avouris, J. Appenzeller, Richard Martel, And S. J. Wind.
Proceedings of the IEEE. 91, 11 (2003)