1. Carbon Nanotubes
Adam Charnas

2. A brief history of CNTs
O’Connell

3. 1990
Smalley proposes the existence of a tubular form of carbon following the discovery of fullerenes.

4. Dresselhaus introduces theoretical work on CNT structure and band structure.
August
1991
1990
Smalley proposes the existence of a tubular form of carbon following the discovery of fullerenes.

5. Iijima reports the experimental discovery of MWCNTs.
Dresselhaus introduces theoretical work on CNT structure and band structure.
August
1991
November 1991
1990
Smalley proposes the existence of a tubular form of carbon following the discovery of fullerenes.
Iijima reports the experimental discovery of MWCNTs.

6. Iijima reports the experimental discovery of MWCNTs.
Dresselhaus introduces theoretical work on CNT structure and band structure.
Iijima et. al. and Bethune et. al. report experimental confirmation of SWCNTs.
August
1991
1993
November 1991
1990
Smalley proposes the existence of a tubular form of carbon following the discovery of fullerenes.
Iijima reports the experimental discovery of MWCNTs.

7. Endo reports nanoscale CVD growth of hollow carbon tubes.
1976
Endo reports nanoscale CVD growth of hollow carbon tubes.

8. Endo reports nanoscale CVD growth of hollow carbon tubes.
Bacon observes microscale carbon whiskers that, “…consist of cylindrical or prismatic layers of graphite extending over large distances along the axes…”
1956
1976
Endo reports nanoscale CVD growth of hollow carbon tubes.

9. Bacon observes microscale carbon whiskers that, “…consist of cylindrical or prismatic layers of graphite extending over large distances along the axes…”
1956
1955
Hofer et. al. observe nanoscale cylindrical carbon.
1976
Endo reports nanoscale CVD growth of hollow carbon tubes.

10. Bacon observes microscale carbon whiskers that, “…consist of cylindrical or prismatic layers of graphite extending over large distances along the axes…”
Radushkevich and Lukyanovich observe 50 nm diameter MWCNTs via TEM.
1952
1956
1955
Hofer et. al. observe nanoscale cylindrical carbon.
1976
Endo reports nanoscale CVD growth of hollow carbon tubes.

11. O’Connell

12. Degenerate semi-metals with zero bandgap
Semimetal with finite bandgap if 𝑛−𝑚 3 is an integer and 𝑛≠𝑚.
Semiconductor otherwise.
O’Connell

13. Band Structure 𝐸 𝐺 ~ 0.84 𝑒𝑉/𝑑, where d is the tube diameter in nm.
O’Connell

14. Mobility and Current Density
A single CNT has been observed to carry up to 25µA of current (109 A/cm2)
Many potential applications for high speed devices.
Field-effect mobility as high as 79,000 cm2/Vs observed (2004)
Intrinsic mobility estimated ~ 100,000 cm2/Vs at RT
O’Connell
Dürkop et. al., Nano Letters, 2004.

15. Contact Resistance
(Left) For aggressive device scaling contact resistance becomes a major problem.
(Right) One approach that has had some success is pulse annealing (1us to induce joule heating in contacts, to eliminate tunneling barriers).
Franklin et. al., ACS Nano, 2014.
Woo et. al., Nanotechnology, 2007.

16. On/Off Ratio On/Off ratio of 105 in 2018.
(Left) Stanford group (Subhashish Mitra & Philip Wong) method. They use a short high voltage to burn out metallic and leaky semiconducting CNTs.
(Right) An example of modern CNTFET devices.
Burn metallic CNTs to improve On/Off ratio in overall device.
Lin et. al., IEEE Trans. Nano., 2009.
Zhang et. al., ACS Nano, 2018.

17. Device Structure Original device structure Back gated
CNT overlaid on a prepared substrate
(Left) The original CNTFET structure.
(Right) Comparison of typical back-gated CNTFET and traditional MOSFET.
Tans et. al., Lett. to Nature, 1998.
Martel et. al., APL, 1998.

18. Modern CNTFET Devices
(Left) Test chip featuring more advanced CNT devices.
(Middle) An example of an advanced CNTFET device including a top gate, external doping, high-k dielectric, and optimized substrate.
(Right) An example of a T-CNTFET. Some have been fabricated but they are ambipolar and have low current.
Schröter et. al., IEEE J. Elec. Dev. Soc., 2013.
Pourfath et. al., J. Comput. Electron., 2007.

19. Applications Gas Sensing Digital Logic Commercial Applications Nantero
In simulation, a CMOS full adder implemented with CNTFETs outperforms traditional MOSFETs and FinFETs in power consumption, delay, and power delay product.
Commercial Applications
Nantero
RFNano
CMOS applications
Huq et. al., IEEE Proc. 4th Conf. Adv. EE, 2017.
Wang et. al., Sensors, 2011.

20. Applications Computing (Stanford)
Comparable processing power to the Intel 4004 chip.
178 CNTFETs.
From the same Stanford group that did the On/Off ratio burnout improvement (Mitra and Wong).
Shulaker et. al., Nature, 2013.