![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.](https://image.slidesharecdn.com/presentation2cnt1-210719120142/85/Carbon-nantubes-basics-20-320.jpg)
Carbon nantubes basics
- 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.
- 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