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)