1. Power Dissipation in Nanoelectronics
R. Pecora, S. Belavadi, D. Estrada
Pop Research Group
ECE Dept., University of Illinois, Urbana, IL 61801

2. Why is this Important?
Modern electronics such as CPUs generate substantial amounts of heat. This heat has to go somewhere, and it severely limits further improvements to devices.
Lots of power is used up in memory, while PCM can use less energy for more memory density(Making your tiny Ipod nano even smaller)

3. How Small is Nano?

4. CNT – Carbon Nano Tubes
Allotropes of carbon and are 1D hexagonally arranged C atoms.
Properties: High thermal conductivity,
electrical conductivity, tensile strength…
DNA( diameter~ 2.5nm)
SWCNT( diameter~ 1.7nm)

5. Bottom-Up Approach Heater Random CNT Film Sensor 50µm
Target the source of the heat generation, instead of looking into bigger and better cooling.
Graphene: Graphite on the nano level
CNTFET(Carbon Nano Tube Field Effect Transistor): Smaller and less resistive than traditional Higher Transistor Density!
PCM(Phase Change Material): Material that changes phase depending on heating method and temperature.
Sensor
Heater
Random CNT Film
50µm

6. Current Projects
Phase Change Memory: Heat GST(Germanium Antimony Tellurium) to make a binary 1 or 0.
Thermal Properties of CNTs and Graphene: Establish reliable thermal data and models.
Transistor Reliability: Test limits on CNT Transistors; breakdown and hysteresis.
Carbon Nanotube Field Effect Transistor
SiO 2 V DS I D S
= 0 GS ≈

7. Calibrating The Infrascope II
Helped MNTL Staff setup and calibrate an Infrascope II Infrared Microscope.
LN2 jacket for IR detector cooling
1X, 5X, and 15X objectives
Vibration Isolation Table
PC for data acquisition

8. Thermal Imaging With Scope
Took both .jpg(for pretty colors) and .txt(for analysis) of several different devices and temperatures. Put current through device to observe heating effect.
Early image of heating device
[°C]
I’m thinking that I could get a better picture here, but I don’t have any of them on my computer.

9. FET – Field Effect Transistors
Voltage controlled devices

10. Electrical Characterization
Vg swept on a range of voltage (-10 to 10 and back to -10) with constant drain Voltage-- Drain Current is measured.
Temperature measurements.
2 transistor types studied, Namely:
Single lined CNT on FET
Group lined array of CNT on FET
SiO 2 V DS I D S
= 0 GS ≈

11. Hysteresis Is Observed
Cause: Mainly due to trapping of charge.
Problems faced: It causes an unclear threshold voltage and Mobility* due to a finite Vth ( threshold Voltage). Mobility is extracted by the slope of Id – Vg curve.
But which slope to consider, forward or reverse?
Solution: Develop technique to measure true mobility by coinciding the forward and reverse sweeps.
(Design circuit parameters such that Vth is reduced to 0.)
*T. Dürkop, S. A. GeCy, E. Cobas, et al., Nano LeCers 4, 35 (2004).
X. Zhou, J. Park, S. Huang, et al., Physical Review LeCers 95, 4 (2005

12. Pulsed Gate Voltage Pulsed Voltage given to Vg.
Time period = Ton + Toff
Ton variation produces has little effect on hysteresis.
Toff varied – allows charges to settle down *
*Courtesy Sumit Dutta

13. Single CNTFET
toff = 1ms
toff = 1s
toff = 10s

14. Aligned Array Transistor
TOFF=1ms
TOFF=1ms
TOFF=1s
TOFF=1s
TOFF=10s
TOFF=10s
T=23°C
T=100°C
T=23°C
T=100°C
T=180°C

15. Summary Hysteresis reduction can be attained by: Pulsed Vg
High temperatures
Decreasing the physical diameter of CNT.

16. Future Work Heater Random CNT Film Sensor Sensor 50µm
Pulsed ID-VG measurements on Random CNT TFTs
Pulsed ID-VG measurements on Graphene FETs
IR Imaging of Random CNT TFTs
IR Imaging of Graphene FETs