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 PropertiesMaximum Current Capacities: Device 1: 8 μA &
Device 2: 22 μAOn/off ratios: Device 1: 20 & Device 2: 5
Devices 1 and 2
-10
-5
0
5
10
15
20
25
-4 -2 0 2 4Voltage (V)
Cur
rent
(µA
)
Device 1
Device 2
Current Rectification PropertiesDevice 3
-200
0
200
400
600
800
-4 -2 0 2 4Voltage (V)
Cu
rren
t (µ
A)
Maximum Current Capacities: 678.9 μA On/off ratios: 27
Current Rectification PropertiesDevice 4
-200
0
200
400
600
800
1000
-4 -2 0 2 4
Voltage (V)
Cur
rent
(µ
A)
Trial 1
Trial 2
Maximum Current Capacities: 840 μA On/off ratios: 108
Current Rectification PropertiesDevice 5
-1000
-500
0
500
1000
-4 -2 0 2 4Voltage (V)
Cu
rren
t (u
A)
Maximum Current Capacities: 840 μA On/off ratios: ??
Gate Voltage Characterization
•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
Gate Voltage Dependence
250
350
450
550
650
-12 -8 -4 0 4 8 12
Gate Voltage (V)
Cu
rren
t (n
A)
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)