This contains a basic introduction of carbon nanotubes, its properties and types

1. CARBON NANO TUBES
PROPERTIES AND
BENEFITS
Sushmita Dandeliya
2014PIT108

2. Content
 Introduction
 History
 Structure of CNT
 Band structure
 Types of CNT
 Properties and benefits
 CNTFET
 Future
 Conclusion

3. What is carbon nanotube
A carbon nanotube is a graphene sheet (with carbon atoms
appearing in a hexagonal pattern) rolled up to form a hollow
cylinder. CNTs have extremely low electrical resistance
because electrons can travel for large distances without
scattering. This is partly due to their very small diameter and
huge ratio of length to diameter. Also, because of their low
resistance, CNTs dissipate very little energy. This will prove
useful in solving the power consumption problems that are
plaguing Silicon circuits.

4. History of CNT

5. Structure of CNTs
 To understand the atomic structure of CNTs, one can
imagine taking the structure of graphite
Graphene is pure carbon in
the form of a very thin,
nearly transparent sheet,
one atom thick. It is
remarkably strong for its
very low weight (100 times
stronger than steel) and it
conducts heat and electricity
with great efficiency.

6.  A CNT can be viewed as a rolled-up graphene
strip which forms a closed cylinder

9. Contd…
where a = 0.142 nm is the carbon–carbon bond length.
C = na1 + ma2

10. C=Circumferential vector
A,B= 2 atoms in unit cell of graphene

12. Electronic properties
 Zigzag : n or m=0, θ= 00
 ARM Chair : n =m, θ= 300
 Carbon nanotube can be metallic or
semiconducting based on the following rule
n - m = 3i ⇒ Metallic
n – m! = 3i ⇒ Semiconducting
where i is an integer
 A small increase in diameter has a major impact
on the conduction properties of carbon
nanotubes.

13. Band Gaps & Fermi Level of
Materials

14. Cont….
A. Conductor B. Semiconductor C. Semimetal

15. Band structure of CNTs
a. armchair (5,5) nanotube
b. zigzag (9,0) nanotube
c. zigzag (10,0) nanotube

16. Types of CNT
Based on structure
 Single walled nanotube
 Multi walled nanotube MWNTs carry current densities approaching
109 Acm−2.

17. Based on condutuctivity
 Metallic CNT
 hold promise as interconnects in both silicon nanoelectronics
and molecular electronics because of their low resistance and
strong mechanical properties.
 Semiconducting CNT
 Used as channel material in semiconductor applications

18. Properties of CNT
 Small size
 Exceptional electrical properties(Ballistic transport)
 Large current carrying capability
 High mobility

19. Benefits of CNT devices
Predictable electron transport properties
 Reliable device performance
Unique properties due to quantum confinement effects
 Enhancement in device characteristics
Potential to revolutionize nano-scale science and technology

20. CNT based FET
• The operation principle and
the device structure similar to
CMOS devices.
• We can reuse the same CMOS
fabrication process for
CNTFET [3].
• CNTFET has the best
experimentally demonstrated
device current carrying ability
to date.

21. Advantages of CNTs over Silicon
 As Silicon transistors are scaled down the doping of the
channel has to increase proportionately while its volume
decreases. The change in the number of dopants produces
important differences in switching properties and degrades
the overall performance of the system.
 Nanotube transistors can operate even without dopants and
are less sensitive to differences in the channel length.
Instead, CNFETs depend on the diameter of the tube and its
chirality.

22. CNT Challenges
 The production methods available for CNTs either produce
CNTs with widely varying sizes and chiralities or are
prohibitively expensive.
 Exposure to open air can cause an n-type CNT to revert back
to p-type.
 Placing CNTs on substrate is also a big challenge. Some
prospective solutions are DNA Self-Assembly and using a
electric field to direct CNT growth during Chemical Vapor
Deposition.
 The main obstacle to CNTs replacing Silicon transistors is that
there are no mass production methods available for CNTs to
rival the well-developed Silicon and photolithography process
at present.

23. The Future
23
 Medium term (5-10 years)
- Memory devices
- Fuel cells, batteries
- Biosensors (CNT, molecular)
- Biomedical devices
- Advances in gene sequencing
 Long term (> 15 years)
- Nanoelectronics (CNT)
- Molecular electronics
- Use in new aerospace and automotive industry
composites

24. Conclusion
 Carbon Nanotubes show a unique combination of stiffness,
strength, and tenacity compared to other fiber materials
which usually lack one or more of these properties.
 Thermal and electrical conductivity are also very high, and
comparable to other conductive materials.
 Beyond 7nm, silicon is not the ideal substance for nanowires
and it is better to use carbon nanotubes.
 A carbon nanotube FET (CNTFET) has the potential of an
enormous increase of 3-10X in power and/or performance.

25. References
1. Review Paper: Challenges for Nanoscale MOSFETs and
Emerging Nanoelectronics, Yong-Bin Kim, Trans. Electr. Electron.
Mater. 10(1) 21 (2009): G.-D. Hong et al.
2. Leakage current mechanism and leakage reduction techniques in
deep submicrometer cmos circuits, Kaushik Roy et al.,
proceedings of IEEE, Vol 91, No. 2, February 2003
3. Carbon nano tube field effect transistor: A review, PA ALVI et al.,
Indian journal of pure & applied physics, vol.43, Dec 2005, pp.
899-904
4. Simulations of Carbon Nanotube Field EffectTransistors, Rasmita
Sahoo and R. R. Mishra, International Journal of Electronic
Engineering Research ISSN 0975- 6450 Volume 1 Number 2
(2009) pp. 117–125 .

26. Thank you