Schottky Diodes Using SWNT
Networks
Bryan Hicks
Brigham Young University
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
• Large mobilities for high-speed devices
• Can be semiconducting or metallic
Carbon Nanotube Networks
• Random networks of
tubes
• No processing
necessary
• Low resistance at
CNT junctions
• 1/3 metallic, 2/3
semiconducting
• Have properties of
both metals and
semiconductors
Fabrication Process
• Deposit Au and Al
electrodes on to a
Si02/Si chip with SWNT
networks
• Wire bond the
electrodes to a chip
carrier
Current Rectification Properties
Maximum Current Capacities: 8 μA & 22 μA
On/off ratios: 20 & 5
Series Resistances:136 kΩ & 375 kΩ
Current (nA)
SW2 Current Rectification
30000
-4
20000
4Al-3Au
10000
2Al-5Au
0
-2
0
2
-10000
Voltage (V)
4
Current (nA)
Gate Voltage Characterization
Gate Voltage Dependence
800
600
400
200
0
-15
-10
-5
0
5
Gate Voltage (V)
•Current decreases as carriers are removed
•Current increases as carriers are introduced
•The hysteresis seen is due to carrier trapping seen in
other CNT transistors as well
10
15
Actual Devices
• We suspect that the electrode spacing plays a critical
role in achieving current rectification.
• No rectification in device on left
• Varying rectification in the two devices on the right
Summary
• Carbon Nanotube Networks present an
economic way to incorporate CNT properties
into macroelectronics
• Electrode spacing appears to affect mobility
and current rectification
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)
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Acknowledgements
Rocky Mountain Space Grant Consortium
– Summer Internship
ESMD Faculty/Student mentor program
BYU College of Physical and Mathematical Sciences
Brigham Young University
– David Allred, Jon Brame, Johnathan Goodsell
Goddard Space Flight Center Code 541
– Stephanie Getty, Rachel Bis, Dewey Dove